Relevant bibliographies by topics / Vegetation changes / Dissertations / Theses

Dissertations / Theses on the topic 'Vegetation changes'

To see the other types of publications on this topic, follow the link: Vegetation changes.
Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 dissertations / theses for your research on the topic 'Vegetation changes.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.

1

Abraitienė, Jolita. "Climate-induced changes of vegetation in broadleaved deciduous forests." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121024_111936-53102.

Full text
Abstract:
The aim of the study was to investigate the influence of meteorological factors on the phenological phases of the vegetation in broadleaved forests under varying climatic conditions. To attain the aim, the following objectives were set: 1. Characterize the changes of values of meteorological parameters (temperature, precipitation) in the studied period; 2. Determine solar radiation intensity under the canopies of trees, phenological phases of trees and bushes and their changes; 3. Determine the changes of projection coverage, height and phenological phases of herbaceous plants during the growing period; 4. Ascertain the relationship between meteorological factors and phenological phases of woody and herbaceous plants. Scientific novelty, theoretical and practical significance. Up till now in Lithuania phenological studies mostly of agricultural plants have been conducted. Phenological studies on woody and herbaceous plants in the forests of Lithuania are almost absent. Most of the studies were conducted with indicator species, such as hazel, coltsfoot, etc. During the study, for the first time in Lithuania a complex investigation of forest community was carried out and the influence of meteorological factors on the phenological phases of herbaceous and woody plants in Kamša botanical-zoological reserve was determined. The results of the study allow to better assess the influence of meteorological factors on seasonal development (phenology) of herbaceous plants, trees and... [to full text]
Darbo tikslas – ištirti meteorologinių veiksnių įtaką plačialapių lapuočių miškų augalijos fenologiniams tarpsniams skirtingų klimatinių sąlygų metais. Tyrimo uždaviniai: 1. charakterizuoti meteorologinių rodiklių (temperatūros, kritulių) reikšmių kaitą tiriamuoju laikotarpiu; 2. nustatyti apšvietimą po medžių lajomis, medžių ir krūmų lapojimo fenologinius tarpsnius ir jų pokyčius; 3. nustatyti žolinių augalų projekcinio padengimo, aukščio, fenologinių tarpsnių kaitą vegetacijos metu; 4. nustatyti ryšį tarp meteorologinių veiksnių ir sumedėjusių, žolinių augalų fenologinių tarpsnių. Darbo mokslinis naujumas, teorinė ir praktinė reikšmė. Lietuvoje iki šiol daugiausia atlikta fenologinių tyrimų su žemės ūkio augalais. Sumedėjusių augalų ir miško žolinių augalų detalių fenologinių tyrimų Lietuvoje beveik nėra. Daugiausia atlikta indikatorinių rūšių, kaip paprastasis lazdynas, paprastasis šalpusnis ir kt., tyrimų. Pirmą kartą Lietuvoje kompleksiškai tirta miško bendrija, nustatyta meteorologinių veiksnių įtaka sumedėjusių augalų lapojimo ir žolinių augalų fenologiniams tarpsniams Kamšos botaniniame-zoologiniame draustinyje. Darbo rezultatai leidžia geriau įvertinti meteorologinių veiksnių įtaką miško žolinės augalijos, medžių ir krūmų sezoniniam vystymuisi (fenologijai). Gautos žinios svarbios ne tik teoriniam išsamesniam atskirų rūšių biologijos pažinimui, bet ir praktiniams tikslams: dendrologijoje, fitopatologijoje ir t. t.
APA, Harvard, Vancouver, ISO, and other styles
2

Tanentzap, Andrew Joseph. "Global vegetation responses to deer : ecosystem changes and recovery." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609232.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Sturgess, Peter William. "Post-felling vegetation changes on three afforested sand-dune systems." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363340.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Leppälä, M. (Mirva). "Successional changes in vegetation and carbon dynamics during boreal mire development." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514294655.

Full text
Abstract:
Abstract Succession is a compositional change of species and other ecosystem characteristics over time. Mire development, i.e., long-term mire succession is basically driven by an increase in peat layer height, promoting changes in hydrology, vegetation and nutrient status of a particular mire. Due to this, ecosystem processes, such as production and loss of carbon due to decomposition (i.e. carbon gas functions), change with increasing successional mire stage. An adequate method for studying the changes in ecosystem C functions is to measure CO2 and CH4 fluxes between the ecosystem and atmosphere. Succession and carbon dynamics of boreal pristine mires have been much studied. However the link between these phenomena is largely unknown. Further, if and how the C gas functions of mires change during mire succession it is rather poorly understood. The main objective of this thesis was to study how ecosystem functions, measured as CO2 and CH4 exchange, change during mire development. The study also aims to explore the drivers of succession in mire development, i.e., mire succession. Successional mire C dynamics were studied along an eight-kilometer-long successional sequence of primary paludified mires located in the land uplift coast of the Bothnian Bay. Due to the short distance between sites, they all have been under the same climatic control for most of their development. The gradual replacement of plant species with different photosynthetic potential, phenology and assimilating green area resulted in lower-level and temporal variation of CO2 exchange patterns at the later successional stages. Similar to this, CH4 also had the lowest interannual variation in the later stages. In general, CH4 emissions increased with mire age even though this trend did not emerge during the rainy season. Further, this study showed that the wintertime C function pattern was related to the C pattern during the previous summer confirming the important effect of growing season patterns on wintertime C dynamics. In addition to the fundamental effect of vegetation as a driver of succession which was also confirmed in this study, the role of hydrological conditions appeared to be equally important. More constant hydrological conditions at later successional stages resulted in lower temporal variation in CH4 and CO2 fluxes. The present results suggest that the stability of ecosystem C gas functions increases during mire development due to increasing autogenic control
Tiivistelmä Sukkessio on ekosysteemin lajistossa ja sen muissa ominaisuuksissa ajan kuluessa tapahtuva muutos. Suon kehitystä eli pitkäaikaista suosukkessiota vie eteenpäin turpeen paksuuskasvu, joka saa aikaan muutoksia suoekosysteemin hydrologiassa, kasvillisuudessa ja ravinnetilassa. Tästä johtuen myös suoekosysteemin erilaiset prosessit, kuten tuotanto sekä hajoamisen kautta tapahtuva hiilen vapautuminen eli hiilikaasutoiminta muuttuu suon ikääntyessä. Ekosysteemin hiilikaasutoiminnassa tapahtuvia muutoksia voidaan tutkia muun muassa mittaamalla ekosysteemin ja ilmakehän välisiä hiilidioksidi- ja metaanivirtoja. Boreaalisten luonnontilaisten soiden sukkessiota ja hiilidynamiikkaa on tutkittu runsaasti, mutta niiden välistä yhteyttä ei sen sijaan juuri tunneta. Tämän vuoksi ei tiedetä kuinka soiden hiilikaasutoiminta mahdollisesti muuttuu suon kehityksen aikana eli suosukkession edetessä. Tämän tutkimuksen päätavoitteena oli tutkia kuinka hiilidioksidin ja metaanin vaihdolla mitattu ekosysteemitoiminta muuttuu suon kehityksen aikana. Tutkimus pyrki myös selvittämään suosukkessiota kontrolloivat tekijät. Eri-ikäisten soiden hiilikaasudynamiikkaa tutkittiin mittaamalla hiilikaasuja Perämeren maankohoamisrannikolla kahdeksan kilometrin pituisella sukkessiogradientilla, joka koostuu primaarisoistumisen kautta syntyneistä soista. Soiden lyhyestä keskinäisestä etäisyydestä johtuen ne ovat olleet saman ilmastollisen kontrollin alaisena suurimman osan kehityksestään. Vaiheittainen kasvilajien muutos sukkessiogradientilla yhdessä kasvilajien erilaisen yhteyttämispotentiaalin, fenologian ja yhteyttävän lehtipinta-alan kanssa johti hiilidioksidivaihdon alhaisempaan tasoon sekä pienempään ajalliseen vaihteluun vanhemmilla sukkessiovaiheilla. Myös metaanin vaihdolla oli alhaisimmat vuosien väliset vaihtelut vanhemmilla vaiheilla. Yleisesti ottaen metaanipäästöt kasvoivat suon iän myötä, vaikkakaan tätä trendiä ei havaittu sateisena kasvukautena. Lisäksi tutkimus osoitti, että talviaikaiset hiilivirrat (CO2, CH4) seurasivat kesäaikaisen hiilidynamiikan vaihtelua. Kasvillisuuden keskeinen rooli ekosysteemin sukkessiossa havaittiin myös tässä tutkimuksessa. Kasvillisuuden ohella merkittäväksi suosukkessiota sääteleväksi tekijäksi osoittautui hydrologisten olojen vaikutus. Tasaisemmat hydrologiset olot vanhemmilla sukkessiovaiheilla johtivat vähäisempään ajalliseen vaihteluun metaani- ja hiilidioksidivirroissa. Tutkimuksen tulokset viittaavat siihen, että ekosysteemin hiilidynamiikka stabilisoituu suon kehityksen aikana lisääntyvän autogeenisen kontrollin kautta
APA, Harvard, Vancouver, ISO, and other styles
5

Lisius, Grace L. "Vegetation Community Response to Hydrologic and Geomorphic Changes Following Dam Removal in a New England River." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:106917.

Full text
Abstract:
Thesis advisor: Noah P. Snyder
Dam removal is typically used to restore fish passage, natural flow regimes, and sediment transport in streams. However, dam removal also impacts the riparian vegetation, a change that can have wider effects throughout the ecosystem. Quantifying vegetation change requires a multi-year record to document pre-removal communities and both the immediate and delayed responses. In this study, vegetation change was assessed at the Merrimack Village Dam on the Souhegan River in Merrimack, NH, which was removed in August 2008. The removal caused a ~3 meter drop in water level and rapid erosion of impounded sediment, with ~50% removed in the first three months. The vegetation was sampled using plots at specific intervals along 7 monumented transects that were perpendicular to the channel or adjacent wetland. Tree, shrub, and herbaceous communities were assessed using species percent areal coverage techniques in July 2007, 2009, 2014 and 2015. Change over time was quantified using Analysis of Similarity (ANOSIM) on the Bray-Curtis dissimilarity matrix. As expected, vegetation communities in control plots upstream of the impoundment did not show significant change during the study period. Tree and shrub communities adjacent to the impoundment also did not show significant change. All herbaceous communities adjacent to the impoundment changed significantly (p < 0.05). The herbaceous plots closest to the channel changed to bare sand in 2009 due to erosion in the former impoundment, but by 2014 the riparian fringe community seen in 2007 had re-established and expanded in this area, but at a lower elevation. Between 2007 and 2014, the wetland herbaceous community changed from aquatic species to a stable terrestrial community that persisted without significant change in 2015. From 2007 to 2014, the vegetation community on a mid-channel island of impoundment sand changed from a community with ~50% invasive reed canary grass to a ~98% community of invasive black swallowwort, a species not recorded at the site pre-removal. The vegetation response was greatest in areas with largest geomorphic and hydrologic change, such as along the channel margin where erosion and bank slumping created an unstable scarp or on the mid-channel island and off-channel wetland strongly impacted by the lowered water table. However, large unvegetated areas never persisted nor did the areal coverage of invasive species expand: two common concerns of dam removals
Thesis (BS) — Boston College, 2016
Submitted to: Boston College. College of Arts and Sciences
Discipline: Scholar of the College
Discipline: Earth and Environmental Sciences
APA, Harvard, Vancouver, ISO, and other styles
6

Gibbs, Holly K. "Quantification of Human-Induced Changes in Global Vegetation and Associated Climatic Parameters." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406738681.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Bradford, Jessica. "Examining Culex tarsalis (Diptera: Culicidae) population changes with satellite vegetation index data." Kansas State University, 2014. http://hdl.handle.net/2097/17139.

Full text
Abstract:
Master of Public Health
Department of Diagnostic Medicine/Pathobiology
Michael W. Sanderson
A zoonotic disease is any disease or infection that is naturally transmissible from vertebrate animals to humans. Over 200 zoonoses have been described (Zoonoses and the Human-Animal-Ecosystems Interface, 2013). Many zoonotic viruses are arboviruses, viruses transmitted by an infected, blood-sucking, arthropod vector (Hunt, 2010). There are several endemic arboviruses in the United States; some foreign arboviruses, such as Rift Valley fever (RVF) virus, are potential bioterrorism agents (Dar, 2013). Arboviruses, both endemic and foreign, threaten public health (Gubler, 2002) and therefore disease surveillance, vector control and public education are all vital steps in minimizing arboviral disease impact in the United States. Mosquito-borne disease threats, such as West Nile virus and Rift Valley fever, are constant concerns in the United States and globally. Current strategies to prevent and control mosquito-borne diseases utilize vector distribution, seasonal and daylight timing, and variation in population numbers. Climate factors, such as availability of still water for development of immature mosquitoes, shade, and rainfall, are known to influence population dynamics of mosquitoes. Using 1995-2011 mosquito population surveillance data from Fort Riley, Kansas, we compared population numbers of Culex tarsalis (Diptera: Culicidae), a vector of several arboviruses including West Nile virus and potentially Rift Valley fever, to a satellite-derived index of climate, the Normalized Difference Vegetation Index (NDVI) anomaly. No correlation between the population numbers and NDVI anomaly was observed, which contrasts with results from similar analyses in other locations. These findings suggest a need for continued investigation into mosquito population dynamics in additional ecological regions of the United States to better describe the heterogeneity of environment-population relationships within and among mosquito species.
APA, Harvard, Vancouver, ISO, and other styles
8

Winning, Geoffrey Bruce, and res cand@acu edu au. "Vegetation Changes in a Large Estuarine Wetland Subsequent to Construction of Floodgates: Hexham Swamp in the Lower Hunter Valley, New South Wales." Australian Catholic University. School of Arts and Sciences, 2006. http://dlibrary.acu.edu.au/digitaltheses/public/adt-acuvp107.11092006.

Full text
Abstract:
Floodgates were constructed in 1971 on the main creek draining Hexham Swamp, a large wetland on the floodplain of the lower Hunter River, New South Wales. Substantial changes in vegetation have occurred in Hexham Swamp subsequent to the construction of the floodgates. Previous areas of mangroves and saltmarsh have been reduced (180ha to 11ha, and 681ha to 58ha, respectively), and Phragmites australis has expanded (170ha to 1005ha). Much of the mangrove loss (ca. 130ha) was a result of clearing, and the remainder has gradually died off. The factors contributing to the dieback are likely to be a combination of drying of the soil, root competition and, at times, waterlogging. Field sampling as well as microcosm and reciprocal transplant experiments involving key species, Sarcocornia quinqueflora, Sporobolus virginicus, Paspalum vaginatum and Phragmites australis, suggest that a reduction in soil salinity has been an important factor in initiating successional change from saltmarsh to Phragmites reedswamp. The data also suggest that increased waterlogging has been an important factor in initiating vegetation change. This apparently paradoxical result (floodgates and associated drainage generally result in drying of wetlands) is likely to have resulted from occlusion of drainage lines (by sediment and reeds) and is, therefore, likely to be a condition that developed gradually. That is, the initial effect of the floodgates is expected to have been a drying of the swamp, followed over time by an increasing wetness. An examination of vegetation changes after removal of cattle from part of Hexham Swamp, suggests that grazing had little effect on species composition of vegetation or rate of expansion of Phragmites australis. However, grazing does affect vegetation structure (height and density), possibly favours some coloniser species (e.g. Sarcocornia quinqueflora) in particular environmental conditions, and possibly inhibits establishment of Phragmites australis.
APA, Harvard, Vancouver, ISO, and other styles
9

Twigger, S. N. "Late Holocene palaeoecology and environmental archaeology of six lowland lakes and bogs in North Shropshire." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382901.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Bodin, Jeanne. "Observed changes in mountain vegetation of the Alps during the XXth century - Role of climate and land-use changes." Phd thesis, Université Henri Poincaré - Nancy I, 2010. http://tel.archives-ouvertes.fr/tel-00592144.

Full text
Abstract:
La végétation herbacée est un bon indicateur des conditions environnementales. Pour cette raison, elle a souvent été utilisée pour mettre en évidence les changements environnementaux causés par les actions humaines, tels qu'eutrophisation, dépôts atmosphériques acides, changements de l'usage des sols ou de la pression d'herbivorie. Depuis peu, on s'intéresse aux effets des changements climatiques sur les écosystèmes en général, et sur la végétation en particulier. Le choix des zones d'étude s'est naturellement porté sur la montagne, car le gradient thermique induit par le relief (-0,56°C pour 100 mètres d'altitude) y est mille fois plus élevé qu'en plaine le long du gradient latitudinal. D'autre part, les zones de montagne sont soumises à une urbanisation et une pression agricole moindre qu'en plaine, limitant ainsi les obstacles à la migration des espèces. Ces deux arguments font des régions de montagne une zone privilégiée pour l'étude de la réponse migratoire précoce de la végétation aux changements climatiques. Jusqu'ici, les études effectuées se sont focalisées pour la plupart sur la limite supérieure des espèces, ou sur de petites zones géographiques, ou bien encore sur des zones où il est difficile de dissocier les effets du réchauffement de ceux des changements d'usage des sols, qui se produisent eux aussi à grande échelle. Une partie de cette thèse est consacrée aux milieux forestiers montagnards, dans lesquels l'effet du pastoralisme est réduit. D'autre part, une méthode basée sur la modélisation des changements de la réponse de la végétation au gradient d'altitude est développée, permettant le rééchantillonnage sur placettes non-permanentes, et ainsi d'étendre l'utilisation de données anciennes à des séries de relevés non géolocalisés. En s'appuyant sur cette méthode, deux caractéristiques de la végétation ont été analysées : la position de l'optimum d'espèces prises individuellement d'une part (données de l'Inventaire Forestier National dans les montagnes méditerranéennes du sud-est de la France), et les changements de la valeur indicatrice des communautés végétales d'autre part (vallée de la Maurienne, France). Par ailleurs, on a étudié les déplacements à long terme de la limite inférieure des espèces dans la vallée de la Bernina (Suisse), pour tester si la réponse des espèces en limite inférieure, peu étudiée jusque là, est identique à celle en limite supérieure de leur distribution. Enfin, on a étudié l'évolution de la flore d'une zone très localisée, mais par ailleurs protégée des migrations d'espèces par une large barrière physique constituée par deux glaciers (Nunatak Isla Persa, Bernina, Suisse) permettant de s'affranchir totalement des effets potentiels d'autres perturbations anthropiques concomitantes. Dans ces différentes études, les intervalles de temps entre chaque inventaire ou échantillonnage varient de 14 ans à un siècle. Chacun des cas étudiés montre une remontée des espèces en altitude : remontée moyenne de +12,6 m/décennie des optimums de 175 espèces forestières dans les montagnes méditerranéennes, communautés des forêts de Maurienne évoluant vers une végétation plus thermophile à une altitude donnée équivalent à une remontée moyenne de +29.6m/décennie, retrait de la limite inférieure des espèces en Bernina de +5,6 m/décennie, arrivée d'espèce d'étages inférieurs sur le nunatak Isla Persa. Mais d'autres phénomènes expliquant la réponse observée de la végétation sont clairement mis en cause dans cette étude : fermeture et maturation du couvert forestier relativement plus importante à basse altitude dans les montagnes méditerranéennes, eutrophisation importante de la végétation en vallée de la Maurienne probablement due à l'augmentation du trafic routier, probable fragmentation de l'habitat ou dispersion par les randonneurs en Bernina. Ces perturbations anthropiques directes jouent à des échelles de temps et d'espace comparables à l'effet anthropique indirect du changement climatique. Il est donc primordial de les prendre en compte dans les changements de végétation observés, avant de conclure à un effet du réchauffement climatique seul.
APA, Harvard, Vancouver, ISO, and other styles
11

Safar, Nathália Vieira Hissa. "Changes in soil and vegetation attributes during lowland Atlantic forest succession in Brazil." Universidade Federal de Viçosa, 2018. http://www.locus.ufv.br/handle/123456789/21187.

Full text
Abstract:
Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2018-08-15T12:50:42Z No. of bitstreams: 1 texto completo.pdf: 1096026 bytes, checksum: 94757b424c78b7d4e3778473e3f61d24 (MD5)
Made available in DSpace on 2018-08-15T12:50:43Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1096026 bytes, checksum: 94757b424c78b7d4e3778473e3f61d24 (MD5) Previous issue date: 2018-03-09
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Distúrbios antrópicos, como a fragmentação e o desmatamento, causam a perda de biodiversidade e estoque de carbono, afetam a produção de serapilheira, causam mudanças drásticas no microclima no chão da floresta o que afeta a dinâmica dos nutrientes do solo, e consequentemente, afetam o funcionamento do ecossistema. Após uma floresta sofrer distúrbio se inicia um processo de sucessão secundária, que envolve mudanças nas comunidades de plantas e animais (principalmente artrópodes), no estoque de carbono, produção de serapilheira e nas propriedades do solo. A Mata Atlântica brasileira é uma das florestas tropicais mais diversas e ameaçadas do mundo, e sua paisagem é composta principalmente por pequenos fragmentos que se encontram em algum estádio de regeneração devido à impactos humanos passados. Esses fragmentos em regeneração desempenham um importante papel na mitigação do carbono e na conservação da biodiversidade. Para investigar as mudanças ao longo da sucessão e a resiliência de florestas de tabuleiro, nós estabelecemos três objetivos principais: (i) avaliar os efeitos do corte raso, com remoção total das árvores, nas propriedades químicas do solo e sua resiliência; (ii) avaliar os efeitos da sucessão na riqueza e composição de árvores e formigas, estoque de carbono total e acima do solo, nos componentes do solo (C orgânico, P, Al 3+ e soma de bases); e (iii) o tempo que as florestas de tabuleiro em regeneração levariam para atingir os níveis de florestas maduras próximas, para cada parâmetro. Este estudo foi conduzido em florestas preservadas e florestas em regeneração do norte do Espírito Santo, Brasil. Para atingir o objetivo (i) analisamos e comparamos dados de solo (pH, P, Al 3+ , K + , Ca 2+ + Mg 2+ ), coletados em dois momentos (1978, 2017), de uma floresta madura (controle) e uma floresta próxima que sofreu corte raso como parte de um experimento de longo prazo realizado em 1980, na Reserva da Vale (Espírito Santo, Brasil). Para atingir os objetivos (ii-iii) nós adotamos uma abordagem de cronossequências utilizando duas florestas maduras e onze florestas em regeneração com diferentes idades, distribuídas nas regiões Norte do Espírito Santo e Sul da Bahia, Brasil. Ao avaliar os efeitos do corte raso nas propriedades do solo, nossos resultados mostraram que não houve diferenças significativas entre os tratamentos para nenhum dos componentes do solo (LMM; p>0.05). Sendo assim, ambas as florestas apresentaram a mesma dinâmica do solo ao longo dos 39 anos: aumento de pH (LMM; p<0.01) e diminuição de Al 3+ trocável ao longo dos anos (LMM; p<0.001), ausência de mudanças nos níveis de P, K + e Ca 2+ + Mg 2+ (LMM; p>0.05). Estes resultados sugerem que o P disponível e as bases trocáveis, K + e Ca 2+ + Mg 2+ , sejam resistentes ao corte raso de árvores. Outros estudos comparando estes resultados com a dinâmica das árvores das mesmas áreas ajudarão a esclarecer e entender o padrão encontrado. Além disso, ao avaliar os efeitos da regeneração nos atributos florestais, encontramos relações positivas e significativas (p<0.001) entre a idade do fragmento e a riqueza e composição arbórea, a composição de espécies de formigas e o estoque de carbono total e acima do solo, sugerindo que estes parâmetros podem ser usados como indicadores de recuperação florestal. No entanto, não encontramos relação entre as propriedades do solo e o avanço da sucessão (p>0.05). Este estudo prevê que as florestas de tabuleiro em regeneração levariam cerca de 57-126 anos para recuperar a riqueza e composição de espécies de árvores e formigas, e levariam muito mais, cerca de 188 anos para recuperar o estoque total de carbono. Além disso, essas florestas estão potencialmente sequestrando 1.04 Mg C ha - yr -1 , portanto contribuindo com um importante serviço ecossistêmico que é o sequestro de CO 2 . Nossas descobertas sugerem que a riqueza de formigas e os solos de florestais ombrófilas do norte do Espírito Santo podem ser resistentes a distúrbios antrópicos. Por fim, nossos resultados mostram que as florestas de tabuleiro são resilientes, porém levariam aproximadamente de 50 a 200 anos para recuperar o estado original de biodiversidade e funcionamento ecossistêmico, evidenciando a necessidade imediata de desenvolver estratégias para selecionar áreas com maior potencial de regeneração natural.
Human disturbances, such as fragmentation and clear-cut logging, cause the loss of biodiversity and carbon stock, affect litter production, cause microclimatic changes at the forest floor, which affect soil nutrient dynamics, and consequently affect the ecosystem functioning. After a disturbance the process of secondary succession begins, which involves changes in plant and animal communities (mainly arthropods), carbon stock, litter production and soil properties. The Brazilian Atlantic forest is one of the most diverse and threatened tropical forest in the world, and its landscapes are mainly composed by small fragments that are in some stage of recovery from past human disturbance. These second-growth fragments have an important role in carbon mitigation and biodiversity conservation. To investigate the changes during forest succession and the resilience of lowland rain forests, we established three main objectives: (i) to assess the effects of whole-tree logging forest clearance on soil properties and their dynamics; (ii) to assess the effects of stand age on tree and ant species richness and composition, aboveground and total C pool, and soil nutrients (organic C, P, Al 3+ and sum of bases) and (iii) to estimate the time secondary lowland forests take to reach the mature forests levels for each parameter. This study was conducted in old-growth and second-growth lowland rain forests from northern Espírito Santo State, Brazil. To accomplish the objective (i) we analyzed and compared soil data (pH, P, Al 3+ , K + , Ca 2+ + Mg 2+ ), collected in two moments (1978, 2017), from an old-growth forest (control) and one adjacent forest that was cleared as part of a long-term experiment performed in 1980, at the Vale Natural Reserve (Espírito Santo State, Brazil). To accomplish the objective (ii-iii) we adopted a chronosequence approach with two old-growth and 11 second-growth forests at different ages, distributed in the northern Espírito Santo and southern Bahia States, Brazil. When assessing the effects of forest clearance on soil properties, we found no significant differences between treatments for any soil component (LMM; p>0.05). Thus, both forests showed the same soil dynamic along the 39 years of interval: increasing pH (LMM; p<0.01), and decreasing Al 3+ over the years (LMM; p<0.001), and no changes in P, K + and Ca 2+ + Mg 2+ (LMM; p>0.05). This result suggest that available P, and exchangeable bases K + , Ca 2+ + Mg 2+ may be resistant to whole-tree removal. Further studies comparing our results regarding the effects of forest clearance on soil properties with the long-term tree dynamic of similar forested areas will help to clarify and understand the pattern found. Moreover, when assessing the effects of forest regeneration on forest attributes, we found positive significant relations (p<0.001) between stand age and tree species richness and composition, ant species composition and carbon pool (total and aboveground), suggesting that these parameters can be used as indicators of forest recovery. However, we found no relationship between soil properties and forest regeneration (p>0.05). This study predicts that secondary lowland rain forests would take several years (57-126 yr) to recover species richness and composition, and much longer, 188 yr to recover C pool, and that these forests are potentially sequestering 1.04 Mg C ha -1 yr -1 , thus contributing to the important ecosystem service of CO 2 sequestration. Our findings suggest that ant species richness and soils of lowland forests can be resistant to human disturbances. Finally, our results indicate that lowland second-growth forests are resilient, but it would take approximately 50 to 100 years to recover the original state of biodiversity and ecosystem functioning, evidencing that we urgently need to develop strategies for selecting areas with highest natural regeneration potential.
APA, Harvard, Vancouver, ISO, and other styles
12

Charles, Sean Patrick. "Saltwater Intrusion and Vegetation Shifts Drive Changes in Carbon Storage in Coastal Wetlands." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3791.

Full text
Abstract:
Coastal wetlands protect coastlines through efficient storage of organic carbon (OC) that decreases wetland vulnerability to sea level rise (SLR). Accelerated SLR is driving saltwater intrusion and altering vegetation communities and biogeochemical conditions in coastal wetlands with uncertain implications. We quantified changes in OC stocks and fluxes driven by 1) saltwater and phosphorous intrusion on freshwater and brackish marshes, 2) vegetation along an experimental saltmarsh to mangrove gradient, 3) saltwater intrusion and vegetation change across a marsh to mangrove ecotone, and 4) vegetation change and mangrove forest development along a marsh to mangrove ecotone. Increasing salinity in freshwater marshes decreased root biomass and soil elevation within one year. In brackish marshes, increased salinity decreased root productivity and biomass and increased root breakdown rate (k), while added salinity did not increase elevation loss. In our experimental marsh-mangrove ecotone, mangrove vegetation promoted higher organic carbon (OC) storage by increasing above and belowground biomass and reducing organic matter k. However, mangroves also increased belowground k, and decreased allochthonous marine subsidies, indicating the potential for OC storage trade-offs. In the Southeast Everglades, we identified strong interior-coastal gradients in soil stoichiometry and mangrove cover. Interior freshwater soil conditions increased k, while total soil OC stocks decreased toward the coast indicating that saltwater intrusion is driving large scale soil OC loss. In the southeast Everglades, mangrove expansion increased root biomass and root productivity, but did not mitigate the overall loss of OC stocks toward the coast. Similarly, in the southwest Everglades, saltwater intrusion drove a decrease in soil OC. However, mangrove encroachment drove a rapid recovery and increased OC stocks. Mangrove encroachment doubled aboveground biomass within the last ten years, increased it 30 times in the last 30 years, and doubled belowground biomass after 20 years. Our research shows that 1) moderate saltwater intrusion without mangrove encroachment will lead to a loss in OC stocks and potentially lead to wetland elevation loss and submergence, 2) in the absence of a change in saltwater intrusion, mangrove expansion can enhance OC storage 3) mangrove expansion can mitigate OC loss during saltwater intrusion, but this pattern depends on mangrove recruitment and ecosystem productivity.
APA, Harvard, Vancouver, ISO, and other styles
13

Okwany, Vincent Ofafa. "Climate and vegetation relationships in southwestern Kenya and the potential impacts of a warmer world." Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278078.

Full text
APA, Harvard, Vancouver, ISO, and other styles
14

Speranza, Alessandra Olga Maria. "Solar and anthropogenic forcing of late-Holocene vegetation changes in the Czech Giant Mountains." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/84035.

Full text
APA, Harvard, Vancouver, ISO, and other styles
15

Wilcox, Julia K. "Recent Vegetation and Area Changes in a Tidal Marsh Located at Pope's Creek, Virginia." W&M ScholarWorks, 1989. https://scholarworks.wm.edu/etd/1539617597.

Full text
APA, Harvard, Vancouver, ISO, and other styles
16

Maliniemi, T. (Tuija). "Decadal time-scale vegetation changes at high latitudes:responses to climatic and non-climatic drivers." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526220123.

Full text
Abstract:
Abstract Boreal and arctic plant communities are responding to anthropogenic climate change that has been exceptionally rapid during the recent decades. General responses include increased productivity, range expansions and biodiversity changes, all of which affect ecosystem functions. Vegetation dynamics are however controlled by multiple drivers, and the outcomes under the changing climate are not yet fully clear. As high latitude areas often lack long-term monitoring of vegetation, alternative methods are required to observe and understand vegetation changes and dynamics. Recently, resurveying historical vegetation data has become a valuable method of studying vegetation changes over the past few decades. In this thesis, I studied multidecadal (23–60 years) vegetation changes in forest and treeless heath and tundra plant communities along a latitudinal gradient in northern Fennoscandia using both vegetation resurveys and long-term experimental data. In addition to examining climate-driven vegetation changes, I related changes in plant communities to key local drivers of each context including mesotopography, grazing, soil moisture and soil fertility. General trends among the resurveyed treeless heath sites were the pronounced increase of the dwarf shrub Empetrum nigrum ssp. hermaphroditum in snow-protected habitats and the decrease of lichens throughout. Southernmost heath communities showed strong responses to multidriver effects and had shifted towards new community states. The long-term experiment in the tundra confirmed that depending on driver combinations, tundra communities evolve towards divergent alternative states, highlighting the importance of local drivers in modifying tundra vegetation over time. Communities in fertile forest sites experienced greater temporal turnover compared to infertile forest sites, suggesting that the soil fertility level is a key predictor of vegetation changes under climate change. This particularly important finding previously relied mainly on experimental evidence. Despite these generalities, changes in diversity, plant groups and species varied under a rather uniform climatic warming trend and were often habitat- or region-specific. Thus, the results of my thesis highly motivate continued monitoring and resurveying of vegetation under rapid environmental change and also form baseline time-series data for future studies
Tiivistelmä Poikkeuksellisen nopea ilmastonmuutos on johtanut viime vuosikymmenten aikana muutoksiin boreaalisissa ja arktisissa kasviyhteisöissä. Muutoksiin lukeutuvat tuottavuuden lisääntyminen, levinneisyysrajojen siirtyminen sekä muutokset biodiversiteetissä, mitkä kaikki muuttavat ekosysteemien toimintaa. Kasvillisuuden dynamiikkaa säätelevät kuitenkin useat paikallistason tekijät, minkä seurauksena ei ole täysin selvää, miten kasvillisuus on eri alueilla ja habitaateissa muuttunut. Koska kasvillisuuden jatkuva monitorointi on harvinaista pohjoisilla alueilla, vanhojen kasvillisuusaineistojen uudelleenkartoituksista on tullut tärkeä menetelmä muutosten havaitsemiseksi. Tutkin väitöskirjassani vuosikymmenten kuluessa tapahtuneita (23–60 vuotta) kasvillisuusmuutoksia Pohjois-Fennoskandian metsissä, puuttomilla kankailla ja tundralla uudelleenkartoitusten ja kokeellisen tutkimuksen avulla, ja kytkin ne ilmastonmuutokseen sekä tärkeimpiin paikallisiin tekijöihin. Yleisiä trendejä uudelleenkartoitetuilla puuttomilla kankailla olivat variksenmarjan (Empetrum nigrum ssp. hermaphroditum) voimakas lisääntyminen lumensuojaisissa habitaateissa sekä jäkälien väheneminen kaikkialla. Yhteisöjen kokonaismuutos oli voimakkainta eteläisillä puuttomilla kankailla, jossa se korreloi yhtä aikaa lisääntyneiden lämpötilojen ja laidunpaineen kanssa. Kokeellinen tutkimus tundralla osoitti, että kasviyhteisöt kehittyvät hyvin erilaisiksi paikallisten tekijöiden voimakkuussuhteista riippuen, jotka voivat joko hidastaa tai nopeuttaa ympäristömuutoksista johtuvia kasvillisuusmuutoksia. Metsien uudelleenkartoitus osoitti yhteisöjen kokonaismuutoksen olevan pitkällä aikavälillä suurempaa tuottavilla maaperillä lehtometsissä verrattuna karumpiin kangasmetsiin. Tutkimuksen mukaan maaperän tuottavuus on avaintekijä, joka ennustaa kasvillisuusmuutosten voimakkuutta ilmastonmuutoksen aikana. Tästä tärkeästä löydöstä oli aiemmin pääasiassa vain kokeellista tutkimustietoa. Yleisistä trendeistä huolimatta, muutokset diversiteetissä, kasviryhmissä ja yksittäisissä lajeissa olivat kuitenkin vaihtelevia ja usein habitaatti- tai aluesidonnaisia. Väitöskirjani tulokset, jotka muodostavat myös aikasarjan tuleville tutkimuksille, osoittavat kasvillisuuden monitoroinnin ja uudelleenkartoitusten olevan ensisijaisen tärkeitä, jotta kasvillisuuden dynamiikkaa voidaan ymmärtää paremmin nopeasti muuttuvissa olosuhteissa
APA, Harvard, Vancouver, ISO, and other styles
17

Bodin, Jeanne [Verfasser]. "Observed changes in mountain vegetation of the Alps during the XXth century : role of climate and land-use changes / Jeanne Bodin." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2011. http://d-nb.info/1013473574/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
18

Barbosa, Humberto. "Vegetation Dynamics Over the Northeast Region of Brazil and Their Connections With Climate Variability During the Last Two Decades of the Twentieth Century." Diss., The University of Arizona, 2004. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2004_188_sip1_w.pdf&type=application/pdf.

Full text
APA, Harvard, Vancouver, ISO, and other styles
19

Hoyt, Cathryn A. "Grassland to desert : Holocene vegetation and climate change in the northern Chihuahuan Desert /." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992819.

Full text
APA, Harvard, Vancouver, ISO, and other styles
20

Huhta, A. P. (Ari-Pekka). "Restorative mowing on semi-natural grasslands: community-level changes and species-level responses." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514259947.

Full text
Abstract:
Abstract This thesis operates at two levels of ecological research, describing the effects of withdrawal and re-introduction of management on grasslands. The aim of the community-level survey was to explore the effects of abandonment, mowing and grazing on semi-natural meadows in northern Finland. At the species level, the aim was to evaluate the responses of three monocarpic meadow species to various degrees of simulated grazing under natural growth conditions. The community-level studies suggest that strongly competitive grass species with rapid vegetative growth, especially those forming tussocks, are able to retain or increase their cover in abandoned meadows. However, most species are able to persist in a meadow for a long time after abandonment, even when a group of immigrants arrive. This leads to a temporary increase in species diversity, and it may therefore be used as an indicator of ongoing succession. Nevertheless, abandonment is harmful for the rare archaeophytic species in the long run. Late mowing does not have extensive short-term impacts on grass-dominated semi-natural meadows. Therefore, it is neither an efficient nor a substitutional way of management when the goal is to restore a formerly grazed pasture. Mowing executed early in the season may, however, be a more appropriate way of inducing changes in species composition and enhancing species richness. According to the results of the species-level studies, Erysimum strictum and Rhinanthus minor tolerate well minor apical damage, while more severe damage has a detrimental impact on the performance of both species. The observed differences in regrowth responses between the two species are presumably due to their different habitat requirements in relation to competition. The species-level experiment with two late-flowering populations of field gentian Gentianella campestris ssp. campestris revealed that the southern, Swedish population that has been regularly grazed and mown overcompensated for the intermediate (50%) damage level, whereas the northern, Finnish field gentians growing in unmanaged habitats showed at best partial or full compensation. Regular grazing and mowing have presumably favoured grazing-tolerant plant species, i.e. species with a good regrowth capacity. Herbivory reshapes grassland plant communities in two ways: directly by affecting the survival and reproductive success of individual plants and indirectly by changing the competitive environment. Tall and competitive perennial species suffer relatively more from damage than true grassland species, i.e. small herbs and grasses, which are better able to tolerate regular tissue losses and respond to damage within the ongoing growing season. As a result, certain species benefit from grazing and mowing in the sense that they may gain more through competitive relaxation than they lose in defoliation.
APA, Harvard, Vancouver, ISO, and other styles
21

Sulieman, Hussein Mohamed. "Mapping and Modelling of Vegetation Changes in the Southern Gadarif Region, Sudan, Using Remote Sensing." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1199964393472-79860.

Full text
Abstract:
The study was conducted at the vicinity of the rural town of Doka in an area of about 55 x 40 km2. The aim of the study was to map and model the influences of the introduction of mechanized rain-fed agriculture and its rapid expansion on the natural vegetation in the southern Gadarif Region. To achieve these objectives the study utilized a series of techniques. Beside the intensive use of remote sensing imagery, interviews with key informants and farmers as well as detailed field surveys were carried out. Multi-temporal analyses of remote sensing imagery showed that during the seventies the average natural vegetation clearing rate increased most rapidly and then began to slow down. Farmers are aware that land degradation, in various forms, is taking place on their cultivated agricultural land. This is based on their perception and the interpretation of indicators such as weed infestation, reduced soil fertility and soil compaction. Continuous cropping, mono-cropping, rainfall shortage and the use of inferior seeds were the main reasons of land degradation indicated by the farmers. Abandonment of agricultural land to restore soil fertility is a common practice among farmers in the Gadarif Region. The study proved that the subsequent natural regeneration of plant species and the vegetation development on abandoned agricultural land are subject to the previous cultivation period and the duration of the fallow. The current regeneration capacity of the abandoned land may not be sufficient to reach full restoration of the previous vegetation climax except for some pockets which received more regenerative resources. Field surveys in conjunction with remotely sensed and topographic data have the potential to explain the restoration and rehabilitation patterns of degraded/abandoned agricultural land to a good extent. The findings of the study seem to be representative not only for the whole Gadarif Region or other areas in Sudan, but also for other regions in the Sahel Zone with similar problems and environmental and social conditions. One of the most practical conservation approaches is to let farmers play an active role in managing their abandoned land. Such management aims to allow for a certain level of use and benefits while maintaining the natural vegetation development on theses area in order to achieve maximal restoration. Although the study investigated the vegetation development in abandoned mechanized rainfed agricultural land, a full understanding of the path-way needs surveys that include more types of abandoned land and investigation of the effects of other local environmental factors (e.g. fire, grazing, distance from forests etc.) for more than one season.
APA, Harvard, Vancouver, ISO, and other styles
22

Strömberg, Pernilla. "Förändringar i vegetationens sammansättning efter en våtmarksrestaurering : Changes in the vegetation composition after a wetlandrestoration." Thesis, Karlstad University, Division for Environmental Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1715.

Full text
Abstract:

The loss of such great wetlands, which has arose in Sweden the last decades, has created a situation that threats both the function and the biological diversity within the wetlands. Many ecological niches can be found in the wetlands and it is one of the habitats where most different species exist. In the 17th Century people started to ditch damp environments, such as bogs, to create a productive cultivated ground. Further ditches were made when the forestry gave large economical profits. The wetlands were impoverished from both groundwater and nourishment, and this led to a great loss of species.

In a corporation with WWF and Skogsstyrelsen in Arvika, the University of Karlstad has participated in the Laskerudproject, a hydrological restoration-project in a forest landscape. The purpose of the project was to increase the groundwater level and to recreate the functions of the wetlands. The project has partly analysed the change in the vegetations composition during six years. The restoration took place in the year 2004 and the inventory of the wetland’s flora has been carried on between the years 2002 and 2007. The same 40 test-squares in Södra ängsmyren, which have been chosen at random, have been analysed every year in august; also 40 randomly chosen test-squares in Lenungen where looked at. The latter were used as a control area.

All occurring species have been analysed statistically with the parametric z- and t-test and the non-parametric Wilcoxon-test. This was made to analysed if the hypotheses that the number of alter species are more in Södra ängsmyren than in Lenungen. The hypothesis if the hydrophilic species have increased and the hydrophobic species have decreased in Södra ängsmyren was also analysed the same tests mentioned above.

The results of the analysed material showed a significant increase in two of the species in both Södra ängsmyren and Lenungen. The remainder species in Södra ängsmyren could show interesting trends, even though they were not significant. Some species in the wetlands have got a wider area of distribution, this has been visually observed. In comparison with similar studies this study shows the conclusion that more time is needed to prove the changes statistically. As a suggestion, three to five years of further data of the wetlands flora is needed to prove the changes statistically.

APA, Harvard, Vancouver, ISO, and other styles
23

Pittam, Nathan J. "Aspects of vegetation and land use changes during historical times from English lowland lake records." Thesis, Coventry University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439104.

Full text
Abstract:
A major focus of palaeoecological research has been to reconstruct the vegetation history of Britain and examine the impact of humans and climatic variability on the landscape. Most studies undertaken have concentrated on the prehistoric period and less attention has been given to changes occurring in the historical period. This project therefore aims partially to redress this imbalance by presenting the findings of two palaeoenvironmental reconstructions from lake deposits in the English Midlands during the historical and archaeological periods. Palaeoenvironmental changes as inferred from pollen and mineral magnetic signatures preserved in lake sediments of two diverse lowland catchments (Kyre Pool, Worcestershire and Aqualate Mere, Staffordshire) have been placed within a rigid chronological framework usmg combinations of Radiocarbon, Spheroidal Carbonaceous Particle, profiles, Lead-210 and Caesium-137. Key periods of vegetation change have been successfully correlated with archival and archaeological records of land-use change; including the impacts of Romanisation on the landscape, agricultural changes occurring during the Medieval period. Additionally more catchment specific alterations such as Nineteenth Century landscaping and plantation of woodlands are identified and correlated with archival sources. Attempts to detect the short-term regional impact of the Laki Fissure eruption of A.D.l783 was trialled at Kyre Pool with limited success: the eruption could be stratigraphically constrained but no impact in the pollen diagram could be discerned. Findings of ,an assessment of the taphonomic processes operating in lake systems highlight the effects of surrounding vegetation in modifying the atmospheric component of pollen deposited into lakes. A comparison between sediment source changes and the preserved pollen assemblage. highlights a possible relationship between the two. Changes within the pollen record occur alongside sediment sources changes. The taphonomic process of both hydrological and atmospheric pathways has implications for preserved pollen assemblages and interpretations based upon them.
APA, Harvard, Vancouver, ISO, and other styles
24

Memiaghe, Herve Roland. "Old field restoration : vegetation response to soil changes and restoration efforts in Western Cape Lowlands." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/1956.

Full text
Abstract:
Thesis (MScConsEcol (Conservation Ecology and Entomology))--Stellenbosch University, 2008.
In the Mediterranean climate regions of the world, agricultural practices have caused considerable landscape transformation and lead to introduction of alien species that now dominate secondary succession on abandoned agricultural fields. Various restoration attempts have been made to reduce alien plant species cover, and to enhance the re-establishment and cover of native plant species. However, results and successes were mostly short-term due to re-growth and persistence of the weedy alien species, which has been suggested to be caused by land use history, especially the nutrient enrichment of soil, and particularly phosphorus and nitrogen. This study investigated different soil properties (pH, electrical conductivity (EC), soil moisture, as well as available phosphorus (P) and total nitrogen (N)) on 10 and 20 year old abandoned fields, as a function of depth in three habitats (ridge (old cultivated area), ditch (old drainage line) and slope (intermediate zone between ridge and ditch)) on the old fields. The relationship between these soil properties and the vegetation occurring on the two old fields was established. At the same time, restoration treatments (autumn burn, combination of autumn burn and herbicide, herbicide application alone, as well as spring burn) were conducted to reduce the cover and abundance of non-native plant species and Cynodon dactylon, and to enhance cover of native species. Results from the study show that levels of all investigated soil properties were higher on the younger field. The highest difference was observed in EC and pH. Seasonal differences in both soil properties could also be observed. A principal component analysis indicated that the dynamic of all soil properties shaped the vegetation type on old fields, with the main soil properties being dependent on land-use history and time since abandonment. This study suggests that EC and pH could be part of parameters that drive the persistence of undesirable species persistence on old fields and inhibit native plant species instead.
APA, Harvard, Vancouver, ISO, and other styles
25

Herrera, Francisco F. "Decomposition and soil organic matter dynamics associated with changes in land use and vegetation cover." Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368370.

Full text
APA, Harvard, Vancouver, ISO, and other styles
26

Gunnarsson, Urban. "Vegetation changes on Swedish mires : Effects of raised temperature and increased nitrogen and sulphur influx." Doctoral thesis, Uppsala : Acta Universitatis Uppsaliensis, 2000. http://catalogue.bnf.fr/ark:/12148/cb40007342x.

Full text
APA, Harvard, Vancouver, ISO, and other styles
27

Partanen, S. (Sari). "Recent spatiotemporal changes and main determinants of aquatic macrophyte vegetation in large lakes in Finland." Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514285950.

Full text
Abstract:
Abstract During the past half century several large lakes in Finland have experienced notable changes in their ecological condition, induced mainly by water level regulation, eutrophication and land use transformation. The objective of this thesis was the quantification of the spatiotemporal changes of aquatic macrophytes in Finland during the second half of the 1900s. Mapped aquatic macrophyte cover from historic (1947–1963) and present day (1996–2000) aerial photographs, additional macrophyte data and several environmental variables were used to identify the main determinants of aquatic macrophyte distribution, abundance and change. Furthermore, factors influencing the littoral paludification process were identified. The study was conducted in 24 boreal lakes (41–1116 km2) with multisource vegetation data. Selected environmental variables of water level regulation, eutrophication and geomorphology were collected and analyzed. More than 402 km of littoral shoreline in historic and present day aerial photographs was analyzed with stereoscopic visual interpretation. A total of 474 habitat level study sites were used to examine the determining environmental factors of occurrence, abundance and change of emergent vegetation. Finally, 289 vegetation transects were performed in order to study the occurrence, types and main determinants of littoral paludification. Water level regulation was found to be the primary factor behind aquatic macrophyte vegetation development at the whole lake level. The major vegetation changes were determined by the mean water level rise or reduction, decreased fluctuation range and reduced spring flood. The vegetation response was less pronounced in a lake with water level regulation similar to natural fluctuation. Eutrophication influenced aquatic macrophytes at the site level. Land use variables of tributary and agriculture, indicating nutrient increment, corresponded positively with vegetation occurrence and abundance. Geomorphology explained vegetation development at the habitat level. Clay and related deposits and the shore slope specified the vegetation occurrence and affected the abundance of vegetation. Water level regulation, eutrophication, clay and shallowness were found to influence paludification. Helophyte species, common reed (Phragmites australis) and water horsetail (Equisetum fluviatile), dominated the emergent vegetation in the studied lakes
Tiivistelmä Viimeisen puolen vuosisadan aikana suomalaisiin suurjärviin on kohdistunut lukuisia muutoksia, jotka ovat vaikuttaneet järvien ekologiseen tilaan. Muutoksia ovat aiheuttaneet pääasiallisesti vesistöjen säännöstely, rehevöityminen sekä maankäytön muuttuminen. Tämän väitöskirjan tarkoituksena on analysoida noin viimeisten 50 vuoden aikana suomalaisissa suurjärvissä tapahtunutta ranta- ja vesikasvillisuuden pitkäaikaismuutosta. Historiallisilla (1947–1963) ja nykyisillä (1996–2000) ilmakuvilla, muilla kasvillisuusaineistoilla sekä useilla ympäristömuuttujilla tunnistettiin keskeisiä tekijöitä, jotka vaikuttivat kasvillisuuden esiintymiseen, runsauteen ja muutokseen. Tämän lisäksi tutkittiin rantojen pysyvän umpeenkasvun kehitysprosessia. Tutkimusta varten kasvillisuudesta kerättiin monilähdeaineistoa kaikilta Suomen päävaluma-alueilta yhteensä 24 eri järveltä, joiden koko vaihteli 41–1116 km2:n välillä. Tämän lisäksi useita vesistöjen säännöstelyn, rehevöitymisen ja geomorfologian ympäristömuuttujia kerättiin ja analysoitiin. Stereoskooppisella visuaalisella ilmakuvatulkinnalla tutkittiin yli 402 kilometriä rantaviivaa historiallisista ja nykyisistä ilmakuvista. Ilmaversoisen ranta- ja vesikasvillisuuden esiintymistä, runsautta ja historiallista muutosta analysoitiin 474 habitaattitason tutkimuspisteellä. Rantojen pysyvän umpeenkasvun esiintymistä, umpeenkasvun eri tyyppejä ja sitä määrittäviä tekijöitä tutkittiin 289 kasvilinjalla. Tutkimuksen tuloksena havaittiin, että järvitasolla vesistöjen säännöstely oli tärkein kasvillisuuden historialliseen kehitykseen vaikuttava tekijä. Huomattavimmat kasvillisuusmuutokset määräytyivät keskiveden noston, pienentyneen säännöstelyvälin, vähentyneen kevättulvan ja lasketun keskiveden tason seurauksena. Kasvillisuusmuutokset eivät olleet niin selviä, jos säännöstely muistutti luonnontilaista säännöstelyä. Rehevöityminen vaikutti ranta- ja vesikasvillisuuteen paikallisesti. Ravinteisuutta ilmentävät maankäytön muuttujat, ojat sekä maanviljelys, lisäsivät kasvillisuuden esiintymistä ja runsautta. Geomorfologiset tekijät selittivät kasvillisuuden kehitystä habitaattitasolla. Savinen maaperä sekä rannan mataluus lisäsivät vesi- ja rantakasvillisuuden esiintymistä sekä kasvillisuuden runsautta. Vesistöjen säännöstely, rehevöityminen, savinen maaperä sekä rannan mataluus lisäsivät rantojen pysyvää umpeenkasvua. Ilmaversoiset kasvilajit, järviruoko (Phragmites australis) ja järvikorte (Equisetum fluviatile), hallitsivat kasvillisuutta tutkituissa järvissä
APA, Harvard, Vancouver, ISO, and other styles
28

Valayamkunnath, Prasanth. "Understanding the Role of Vegetation Dynamics and Anthropogenic induced Changes on the Terrestrial Water Cycle." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/105061.

Full text
Abstract:
The land surface and atmosphere interact through complex feedback loops that link energy and water cycles. Effectively characterizing these linkages is critical to modeling weather and climate extremes accurately. Seasonal variability in vegetation growth and human-driven land cover changes (LCC) can alter the biophysical properties of the land surface, which can in turn influence the water cycle. We quantified the impacts of seasonal variability in vegetation growth on land surface energy and water balances using ecosystem-scale eddy covariance and large aperture scintillometer observations. Our results indicated that the monthly precipitation and seasonal vegetation characteristics such as leaf area index, root length, and stomatal resistance are the main factors influencing ecosystem land surface energy and water balances when soil moisture and available energy are not limited. Using a regional-scale climate model, we examined the effect of LCC and irrigation on summer water cycle characteristics. Changes in biophysical properties due to LCC reducing the evapotranspiration, atmospheric moisture, and summer precipitation over the contiguous United States (CONUS). The combined effects of LCC and irrigation indicated a significant drying over the CONUS, with increased duration and decreased intensity of dry spells, and reduced duration, frequency, and intensity of wet spells. Irrigated cropland areas will become drier due to the added effect of low-precipitation wet spells and long periods (3-4% increase) of dry days, whereas rainfed croplands are characterized by intense (1-5% increase), short-duration wet spells and long periods of dry days. An analysis based on future climate change projections indicated that 3–4 °C of warming and an intensified water cycle will occur over the CONUS by the end of the 21st century. The results of this study highlighted the importance of the accurate representation of seasonal vegetation changes and LCC while forecasting present and future climate.
Doctor of Philosophy
APA, Harvard, Vancouver, ISO, and other styles
29

Ashcroft, Michael B. "The spatial variation of environmental factors on the Illawarra escarpment and their influence on vegetation patterns." School of Earth & Environmental Sciences - Faculty of Science, 2009. http://ro.uow.edu.au/theses/3042.

Full text
Abstract:
Mapping and explaining the distribution of vegetation helps land managers to make systematic conservation planning decisions. This is typically achieved using models that correlate the distribution of species with environmental factors, and can predict the vegetation at unsurveyed locations. These Species Distribution Models (SDMs) have numerous unresolved issues, but serve as a useful first-pass approximation for planning purposes.This thesis investigates some of the uncertainties of SDMs, including the impact of data accuracy, the incorporation of spatial processes, the evaluation of alternative models, and the benefits and challenges of producing models at the landscape scale. The research was conducted on the Illawarra Escarpment, 80 km south of Sydney, Australia (34.4 oS, 150.9 oE). The escarpment contains a north-south trend in eucalypts (Eucalyptus spp.) that cannot be explained in terms of elevation or geology. It also exhibits a patchy distribution of rainforest communities, some unique to the Illawarra. It is not known which environmental factors determine the distribution of either the eucalypts or rainforest species, or how they may respond to a changing climate.Species distributions are sensitive to the accuracy of data used, and yet many models only use elevation as a surrogate for temperature, or use simple elevation sensitive interpolations from weather stations. I collected hourly temperature data from 40 sites on the Illawarra Escarpment, and investigated whether elevation was an adequate surrogate for temperatures in this landscape. I then investigated whether temperature surfaces could be improved by considering other topographic and geographic factors, including exposure to wind, distance to coast, radiation, and the average conditions in the surrounding neighbourhood. Elevation was well correlated with moderate seasonal temperatures (e.g. summer minima and winter maxima), but was poorly correlated with the extreme temperatures (summer maxima, winter minima) that are physiologically limiting for many species. Using neighbourhood influences, exposure to wind and distance to coast improved the accuracy of temperature surfaces, and increased the explanatory performance of vegetation models. I concluded that elevation was not always an adequate surrogate for temperature. Temperatures are also affected by other topographic and geographic factors, and these should be considered when developing models for systematic conservation planning activities.Species distribution models are typically based solely on niche factors. Where spatial processes are included, it is typically by employing autologistic regression, or other techniques that use survey data as a predictor. This precludes the models being used to make predictions in times or places where survey data is unavailable, and reduces ecological explanation because it is an interpolation technique. I used neighbourhood (contextual) indices based on environmental factors as an alternative method to overcome these problems. I demonstrate that contextual indices improve SDMs over purely niche-based models, and are capable of predicting unknown populations in unsurveyed areas. I conclude that contextual indices have numerous advantages over autologistic regression, and can capture a continuum between niche and dispersal limited species.Models that predict how species will respond to climate change either use coarse-scale climate surfaces, or idealised predictions of uniform warming. These methods may dramatically over-estimate extinction risk because they neglect fine-scale variations in warming, and refugia where species can persist despite unfavourable regional conditions. I created fine-scale estimates of warming by combining 35 years of Bureau of Meteorology observations with one year of intensive fine-scale temperature monitoring. I found that warming was greatest at inland locations, at lower elevations, away from streams, and at sites exposed to hot, dry northwesterly winds. As species are biased in the geographic and topographic positions they occupied, some species have experienced more warming than others and are at greater threat from climate change. I concluded that it was important to continue developing methods to downscale coarse-grained climate surfaces, and suggest that the accuracy of this process could be improved by using a range of topographic factors.There are many methods for selecting predictors in SDMs, and the competing models often make highly variable predictions. I addressed this uncertainty by comparing the performance of models with and without a given environmental factor. I found that there was relatively strong support for the geology and winter minimum temperature predictors, as well as predictors based on contextual indices, as there was a significant drop in model performance when these predictors were excluded. In contrast, there was less support for summer maximum temperature, as other temperature predictors could combine to produce similar model performance. Model performance varied more between models for different species than between different predictor combinations for the same species. I concluded that it was inappropriate to assess models based on subjective benchmarks, such as an AUC of more than 0.7. A comparison between competing models for the same species gives a better indication of the validity of the model building procedure.The results of this research provide important insights into the benefits and challenges of creating SDMs at the landscape scale (extent of 10–200 km). It is a major challenge to obtain spatially and thematically accurate environmental predictors and biotic data at this scale, and studies should include the collection of data to ensure models are adequate. Landscapes will not have as much environmental variation as coarse-scale models, and this will limit the ability to transfer the models to new study areas. However, there are a number of benefits that justify these studies. Producing accurate temperature surfaces at the landscape scale will result in less pseudoreplication and less predictor colinearity. This will improve the robustness of models. Landscape scale studies also allow modellers to capture fine-scale refugia, and this will improve the accuracy of climate change predictions. Finally, many ecological processes operate at a scale that is too fine to be detected with coarse-scale models. Landscape scale models may be the only alternative to detect these processes. There is no optimal scale for SDMs, however, and a future challenge is to better integrate coarse and fine-scale models to make more ecologically robust predictions.
APA, Harvard, Vancouver, ISO, and other styles
30

Abbasova, Tahira. "Detection and analysis of changes in desertification in the Caspian Sea Region." Thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-43241.

Full text
Abstract:
The Caspian Region includes the Caspian Sea and five littoral states: Azerbaijan, Iran, Turkmenistan, Kazakhstan and Russian. 40% of the Caspian coastal zone is arid, 69% of this territory undergone desertification according to international reports. Among the reasons are soil erosion caused by water, wind and irrigation, the salinization of soil, intense bioresources usage, and soil pollution due to oil extraction and production. Desertification is a serious problem, at global, national and local scales. It is important to know what should be sustained or developed in order to protect land from desertification. The generalization of data over desertification processes in Caspian countries, studying the dynamics of this process in space and time could help facilitate measures to counter regional desertification. To understand Caspian Region coastal desertification phenomenon, vegetation cover satellite images for the years 1982 – 2006 were investigated to give map vegetation changes over time. The Normalized Difference Vegetation Index (NDVI) data for this study was derived from the Global Inventory Modeling and Mapping Studies (GIMMS) dataset, with the spatial resolution of 8 km. A coastal strip 160 km from the coast, divided by countries, was investigated. Theanalyses were focused on extent and severity of vegetation cover degradation, and possible causes such as landscape, land use history and culture, climatic changes and policies. The aim was to address questions related to desertification phenomenon, by focusing on Caspian Region time-series of vegetation cover data and investigation patterns of desertification in the region. In this study evidence of land degradation in the Caspian Region countries was found to occur on local scales or sub-national scales rather than across the regional as a whole. Changes in vegetation cover revealed by AVHRR NDVI appeared to be reversible in character and were dependent on the climate conditions, and anthropogenic impact in approximately equal proportions.
APA, Harvard, Vancouver, ISO, and other styles
31

Karlsson, Hanna. "Vegetation changes and forest-line positions in the Swedish Scandes during late Holocene : anthropogenic impact vs. climate /." Umeå : Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/200831.pdf.

Full text
APA, Harvard, Vancouver, ISO, and other styles
32

Moleele, Nkobi Mpho, and n/a. "Ecological change and piospheres : can the classical range succession model and its modifications explain changes in vegetation and soil around boreholes in eastern Botswana?" University of Canberra. Resource, Environmental & Heritage Science, 1994. http://erl.canberra.edu.au./public/adt-AUC20061018.144247.

Full text
Abstract:
There is concern that the communal rangelands of Botswana are overstocked with cattle, and that this has led to unwanted ecological changes. These changes are assumed to be most prominent around boreholes. This study describes vegetation and soil piospheres around boreholes in Eastern Botswana and investigates factors associated with their development. The classical range succession model and its modifications, the bush encroachment theories and the soil-nutrient transfer model, have been applied here to explain changes in vegetation and soil variables with distance from artificial water points. Data on soil texture, soil nutrients, vegetation species composition and cover, dung weight and bare ground were collected from boreholes of different ages, with different numbers of cattle using them. Piosphere patterns were observed. However, some of the patterns were not in accordance with the classical range succession model and the bush encroachment theories. The frequent occurrence of palatable grasses (Panicum maximum, Setaria verticiliata and Digitaria milanjiand) nearer to water points where the grazing pressure is highest, and of unpalatable ones (Aristida congesta and Eragrostis rigidior) further away, where the grazing pressure is minimal, contradicts the classical range succession model. Total tree cover along the gradient did not show any changes, which contradicts bush encroachment theory (two-layer soil moisture model). The concentration of soil nutrients and dung weight close to boreholes was well predicted by the soil-nutrient transfer model. The frequency of Acacia tortilis and Dicrostachys cinerea and bare patches, increased towards boreholes. Grass cover, occurrence of Terminalia sericea, Boscia albitrunca and Combretum apiculatum increased with distance from water points. The results suggest that the range succession model and its modification, the twolayer soil moisture model, cannot satisfactorily explain vegetation changes with distance from water points. Species composition at a point may be affected by the growth, survival, recovery and reproductive strategies of different species, fire, selectivity of browsers and nutrients status, as well as grazing disturbance. Therefore, the 'state and transition' model is recommended, as it considers factors that are ignored by the classical range succession model, and is appropriate for analysing vegetation change under highly variable rainfall. The adverse impacts of grazing around boreholes could be reduced by controlling cattle distribution on the range as a whole.
APA, Harvard, Vancouver, ISO, and other styles
33

Ryner, Maria. "Past environmental and climate changes in northern Tanzania : Vegetation and lake level variability in Empakaai Crater." Doctoral thesis, Stockholm : Department of Physical Geography and Quaternary Geology, Stockholm University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6835.

Full text
APA, Harvard, Vancouver, ISO, and other styles
34

Qi, Xiaoling 1956. "Changes in riparian vegetation communities of the Gila Box, Arizona, an area subject to periodic floods." Thesis, The University of Arizona, 1995. http://hdl.handle.net/10150/278470.

Full text
Abstract:
The objective of this work is to estimate the effect of floods on the riparian vegetation communities of the Gila Box, Arizona, based on historical maps, satellite images, and GPS-referenced airborne video. The condition and extent of selected riparian vegetation communities in 1973, 1982, and 1991 are documented. Changes in riparian vegetation communities for the time period from 1973 to 1982 and from 1982 to 1991 are analyzed to assess the potential effect of floods that occurred in 1978 and 1983, respectively. The results indicate that the floods in 1978 and 1983 may have had an impact on the mesquite riparian community. The effect of floods on riparian vegetation is most apparent in the downstream portion of the Gila River. The information collected and presented in this work can be used to formulate effective management plans to the Gila Box area.
APA, Harvard, Vancouver, ISO, and other styles
35

Longo, Marcos. "Amazon Forest Response to Changes in Rainfall Regime: Results from an Individual-Based Dynamic Vegetation Model." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11268.

Full text
Abstract:
The Amazon is the largest tropical rainforest in the world, and thus plays a major role on global water, energy, and carbon cycles. However, it is still unknown how the Amazon forest will respond to the ongoing changes in climate, especially droughts, which are expected to become more frequent. To help answering this question, in this thesis I developed and improved the representation of biophysical processes and photosynthesis in the Ecosystem Demography model (ED-2.2), an individual-based land ecosystem model. I also evaluated the model biophysics against multiple data sets for multiple forest and savannah sites in tropical South America. Results of this comparison showed that ED-2.2 is able to represent the radiation and water cycles, but exaggerates heterotrophic respiration seasonality. Also, the model generally predicted correct distribution of biomass across different areas, although it overestimated biomass in subtropical savannahs.
Earth and Planetary Sciences
APA, Harvard, Vancouver, ISO, and other styles
36

Otto, Mia. "Spatial and temporal changes in Fynbos riparian vegetation on selected upland rivers in the Western Cape." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86603.

Full text
Abstract:
Thesis (MScConEcol)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Restoration practices commonly make use of a reference condition in order to restore a site to a better ecological state than it is currently in. The selection process and relevance of the reference condition has not yet been tested in upland Western Cape rivers especially with relation to spatial and temporal scales. This thesis sought to evaluate whether space (longitudinal) and time (temporal) influence riparian plant community composition (laterally), how it influences the community composition and whether these differences impacts the selection of a reference condition used in restoration practices. In order to investigate the role longitudinal position, sites were selected across three longitudinal zones: mountain stream, transitional and upper foothills. Historic sites used in a previous study on riparian vegetation of upland rivers were resampled and datasets used for temporal comparisons between undisturbed sites, sites recovering after clearing of invasive alien plants and sites affected by fire. Riparian vegetation communities showed differences between longitudinal zones, basins and rivers. The species responsible for marginal zone identity (plants in close proximity to the active channel), determined using relative cover abundance varied, with Isolepis prolifera responsible for the group identity in the mountain stream and transitional sites but in the foothills Calopsis paniculata, Drosera capensis and Metrosideros angustifolia saplings were responsible for lateral zone identity. The lower dynamic (transitional between wet and drybank) had no similarities between different longitudinal zones across rivers. In the lower zone Pteridium aqualinum was mostly responsible for the identity. The upper bank had no single species responsible for group identity. The species described to be typical for the reference condition on these particular rivers by other studies were mostly present in the comparable lateral zone but it was however not always responsible for the identity of the specific lateral zone. By comparing selected environmental variables such as horizontal distance from active channel, elevation and substrate calibre with different longitudinal zones’ riparian vegetation species distribution, different combinations were produced. The mountain streams showed the strongest relationship with horizontal distance and elevation in combination to one another and the upper foothills horizontal distance from the active channel was linked most strongly to vegetation positioning. These results confirm the importance of space when attempting to assess, study or restore riparian communities. Temporally, sites had stronger similarity to data collected during the same sampling period than with historic data. Also, the overall relative species abundance did not show significant change to be present at a site scale. The changes in community composition were found to be due to a lateral zone scale variation in species abundance. As expected the undisturbed rivers showed less variation in species responsible for temporal changes than the recovering and fire-exposed rivers. Species responsible for changes in relative abundance at a lateral zone scale were Metrosideros angustifolia, Morella serrata, Brabejum stellatifolium, Isolepis prolifera, Elegia capensis, Prionium serratum and Calopsis paniculata. Due to the species diversity not changing much temporally but the relative abundance of specific species showing much variation over time it can be concluded that the changes are not diversity based but instead driven by changes in relative abundances of species typical for a lateral zone. The spatial and temporal variation in riparian vegetation community composition was found to be significant enough to suggest that the use of a fixed reference condition for all Western Cape rivers would not be feasible due to clear differences between basins. Secondly when selecting a reference site the spatial location of this site should be within the same longitudinal zone since bank shape does influence riparian plant species distribution. Finally the temporal comparison between sites showed high diversity in species abundances but small differences in diversity overall. This would suggest that a general community description specific to 1) where the site is situated and 2) based on the present riparian vegetation community composition within a specific basin may be more realistic and achievable for restoration and environmental management purposes as opposed to using site descriptions from the past and reference sites too far upstream or downstream from the restoration site.
AFRIKAANSE OPSOMMING: Herstel praktyke maak algemeen gebruik van 'n verwysing toestand om 'n terrein te herstel na 'n beter ekologiese toestand as wat dit tans is. Die keuringsproses en relevansie van die verwysing toestand is nog nie in die boonste gedeeltes van Wes-Kaap Riviere getoets nie, veral met betrekking tot ruimtelike en tydskale nie. Hierdie tesis het gesoek om te evalueer of ruimte (longitudinaal) en tyd (temporaal) rivieroewers plant gemeenskap samestelling (lateraal) beïnvloed en of hierdie verskille die keuse van 'n verwysing toestand in die herstel praktyke beïnvloed. Ondersoek terreine was oor drie longitudinale sones geselekteer: berg stroom, oorgangs en boonste hange terreine. Historiese terreine was weer ondersoek en die datastelle was gebruik vir die temporale vergelykings tussen onversteurde terreine, terreine wat herstel na die skoonmaak van indringer spesies en wat geraak was deur 'n brand. Oewerplantegroei gemeenskappe het verskille tussen longitudinale sones, rivier-kom en rivier takke gewys. Die spesies wat verantwoordelik was vir marginale zone (plante in nabye afstand met die aktiewe rivier kanaal) identiteit, bepaal met behulp van relatiewe dekking hoeveelheid, het gevarieer met Isolepis prolifera verantwoordelik vir die groep identiteit in die berg stroom en oorgangs trerreine, maar in die boonste hange was dit Calopsis paniculata, Drossera capensis en Metrosideros angustifolia boompies wat verantwoordelik was vir die laterale sone identiteit. Die laer dinamiese area het geen ooreenkomste tussen marginale gebiede van verskillende longitudinale sones gehad nie. In die onderste sone was Pteridium aqualinum meestal verantwoordelik vir die groepering se identiteit. Die boonste bank het nie 'n enkele spesie wat verantwoordelik was vir die groep identiteit gehad nie. Die spesies beskryf as tipies vir die laterale sone deur Reinecke et al. (2007) was meestal teenwoordig in die beskryfde laterale sone van hierdie studie, maar dit was egter nie altyd verantwoordelik vir die identiteit van die laterale sone gemeenskap nie. Verskillende lengte sones het gekorreleer met verskillende omgewingsveranderlikes wat sterkste gekoppel kon word aan die verspreiding van spesies. Die bergstrome het die sterkste verhouding met horisontale afstand en hoogte in kombinasie met mekaar gehad en in die boonste hange was horisontale afstand van die aktiewe kanaal die sterkste gekoppel aan plantegroei posisie. Die belangrikheid van ruimte is onmiskenbaar ten opsigte van evaluering, bestudering en die herstel van rivieroewers gemeenskappe. Terreine het sterker ooreenkoms met data gehad wat tydens dieselfde tydperk versamel was, as met historiese data. Die algehele relatiewe spesies hoeveelheid het egter nie beduidende verandering getoon op 'n terrein skaal nie. Soos verwag was het die onversteurde riviere minder temporale variasie in spesies getoon as die herstellende en brand blootgestelde riviere. Spesies wat verantwoordelik was vir die verandering in relatiewe hoeveelhede op 'n laterale sone skaal was M. angustifolia, Morella serrata, Brabejum stellatifolium, I. prolifera, Elegia capensis, Prionium serratum en C. paniculata. As gevolg van die diversiteit van spesies wat nie baie verander het tydelik nie, maar die relatiewe hoeveelheid van spesifieke spesies wat heelwat variasie oor tyd getoon het, kan dit afgelei word dat die veranderinge nie diversiteit gebaseerd was nie, maar eerder gedryf was deur veranderinge in relatiewe hoeveelhede van tipiese spesies in 'n laterale sone. Die ruimtelike en tydelike variasie in oewerplantegroei gemeenskap samestelling was beduidende genoeg om voor te stel dat die gebruik van 'n vaste verwysing toestand vir alle Wes-Kaapse riviere nie haalbaar sou wees nie as gevolg van duidelike verskille tussen riviere. Tweedens, by die kies van 'n verwysing terrein moet die ruimtelike plek van hierdie terrein in dieselfde lengte sone wees aangesien bank vorm 'n invloed op rivieroewer plant verspreiding het. Laaastens, het die tydelike vergelyking tussen terreine hoë diversiteit in spesies verspreidings maar klein verskille in algehele diversiteit gehad. Dit stel voor dat 'n algemene beskrywing van die gemeenskap wat spesifiek op 1) waar die terrein geleë is en 2) gebaseer op die huidige oewerplantegroei gemeenskap samestelling binne 'n spesifieke rivier netwerk dalk meer realisties en haalbaar vir hersteel en bestuurs doeleindes sou wees. Hierdie benadering word verkies bo die gebruik van n terrein beskrywings uit die verlede en verwysing terreine te ver stroomop of stroomaf van die herstel gebied.
APA, Harvard, Vancouver, ISO, and other styles
37

Kurzman, Amanda Lord. "Changes in major solute chemistry as water infiltrates soils comparisons between managed agroecosystems and unmanaged vegetation /." Diss., Connect to online resource - MSU authorized users, 2006.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
38

Tang, Guoping. "An examination of vegetation modeling-related issues and the variation and climate sensitivity of vegetation and hydrology in China." Thesis, Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2008. http://hdl.handle.net/1794/8543.

Full text
Abstract:
Thesis (Ph. D.)--University of Oregon, 2008.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 128-156). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
APA, Harvard, Vancouver, ISO, and other styles
39

Colwell, Stephanie Renee. "Characterization of Upland/Wetland Community Types: Changes to Flatiron Lake Bog over a 24-Year Period." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243443626.

Full text
APA, Harvard, Vancouver, ISO, and other styles
40

Marlon, Jennifer R. "The geography of fire: A paleo perspective." Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10334.

Full text
Abstract:
xvii, 205 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
Fire is a fundamental, transformative, yet poorly understood process in the Earth system; it can radically reorganize ecosystems, alter regional carbon and energy balances, and change global climate. Short-term fire histories can be reconstructed from satellite (seasonal- to interannual-scales), historical (decadal scales), or dendrochronological records (for recent centuries), but only sedimentary charcoal records enable an analysis of the complex interactions between climate, vegetation and people that drive fire activity over longer temporal scales. This dissertation describes the compilation, synthesis and analysis of a global paleofire dataset and its application to understanding past, current, and future changes in fire activity. Specifically, I co-led efforts to compile charcoal records around the world into a single database, and to conduct three meta-analyses to understand the controls on fire at multiple spatial and temporal scales. The first meta-analysis reconstructed global biomass burning since the Last Glacial Maximum (LGM) 21,000 years ago. Results from this study demonstrated that global fire activity is low when conditions are cool and high when conditions are warm. This fundamental relationship between climate and fire is due in large part to associated changes in vegetation productivity. The second meta-analysis examined fire activity in North America during past abrupt climate changes and looked for evidence of continental-scale wildfires associated with a hypothesized comet impact ∼13,000 years ago. This analysis found a correlation between increased fire activity and abrupt climate change, but provided no evidence for continental-scale wildfires. A final meta-analysis disentangled the climate and human influences on global biomass burning during the past 2000 years; it found a close relationship between climate change and biomass burning until ∼1750 A.D., when human activities became a primary driver of global fire activity. Together, these three meta-analyses demonstrate that climate change is the primary control of global fire activity over long time scales. In general, global fire activity increases when the Earth's climate warms and decreases when climate cools. The paleofire data and analyses suggest that the rapid climate changes projected for coming decades will lead to widespread increases in fire frequency and biomass burning. This dissertation includes previously published and unpublished co-authored material.
Committee in charge: Patrick Bartlein, Chairperson, Geography; Daniel Gavin, Member, Geography; W. Andrew Marcus, Member, Geography; Cathy Whitlock, Member, Geography; Ronald Mitchell, Outside Member, Political Science
APA, Harvard, Vancouver, ISO, and other styles
41

Bjorkman, Anne Donahey. "Changes in the landscape and vegetation of southeastern Vancouver Island and Saltspring Island, Canada since European settlement." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3421.

Full text
Abstract:
Early land survey records can be used to reconstruct the historical distribution and abundance of tree species prior to the large-scale impact of industrialized societies. Comparing these records to current vegetation patterns enables an examination of the shifts that have occurred in plant communities since the arrival of European settlers in North America. I used presettlement (1859-1874) land survey records from southeastern Vancouver Island and Saltspring Island, British Columbia, Canada to reconstruct the relative abundance and density of tree species in these areas. I then collected equivalent vegetation data from the same points in the modern landscape, which enabled me to compare the two points in time and identify the changes in large-scale vegetation patterns that have occurred since European settlement. My results show a significant increase in the relative abundance of maple (Acer macrophyllum) and cedar (Thuja plicata), and a corresponding decrease in Douglas-fir (Pseudotsuga menzeisii). Furthermore, there has been a considerable increase in tree density in undeveloped areas. The 1859 records indicate that at least one third of the land surveyed was made up of prairies or open “plains,” while a combination of open woods and forests made up the remaining two thirds. Based on comparable density measures from 2007, prairies and plains now represent less than 5% of the undeveloped landscape, while forests comprise nearly 90%. These changes are likely due to a combination of factors that have been influenced by European settlement, most notably logging and fire suppression. The suppression of fire has led to an infilling of trees into previously open areas and has led to the rapid decline of the open prairie and savanna habitat types once common in this area. The results of this study can inform conservation efforts throughout the study area, particularly those involving the restoration of prairie or savanna habitats.
APA, Harvard, Vancouver, ISO, and other styles
42

Tamang, Bijay. "Vegetation and soil quality changes associated with reclaiming phosphate-mine clay settling areas with fast-growing trees." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011871.

Full text
APA, Harvard, Vancouver, ISO, and other styles
43

Wills, Timothy Jarrod 1974. "Succession in sand heathland at Loch Sport, Victoria : changes in vegetation, soil seed banks and species traits." Monash University, Dept. of Biological Sciences, 2002. http://arrow.monash.edu.au/hdl/1959.1/7742.

Full text
APA, Harvard, Vancouver, ISO, and other styles
44

Fer, Istem [Verfasser], and Florian [Akademischer Betreuer] Jeltsch. "Modeling past, present and future climate induced vegetation changes in East Africa / Istem Fer ; Betreuer: Florian Jeltsch." Potsdam : Universität Potsdam, 2018. http://d-nb.info/1218404663/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
45

Ward, Steven. "Reconstructing Vegetation Dynamics from Archaeological Cave Sites in the Western Mediterranean: Links with Climate and Cultural Changes." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487148.

Full text
Abstract:
Aim: This thesis reconstructs vegetation dynamics at four key cave sites in the Western Mediterranean region (Taforalt Cave and Rhafas Cave in north-east Morocco, and Gorham's Cave and Vanguard Cave in Gibraltar), spanning the Last Interglacial-Glacial Period (c.130-13ka BP). Furthermore, it tests the hypothesis that climatic forcing played ~ major role in cultural transitions and possibly human extinction in the Late Pleistocene. Location: North-east Morocco and Gibraltar. Methods: Macroscopic charcoal, phytoliths, and charred seeds were analysed using qualitative and quantitative statistical methods. These were compared at intra-site, inter-site and inter-regional scales. Results: Results from north-east Morocco (spanning c.125- f3ka BP) suggest that local vegetation shifted on numerous occasions over the Last Glacial Period. MIS 5d-a and MIS4 vegetation was characterised by a decline in temperate Quercus deciduous and expansion in cool Cedrus atlantica, while MIS 3 and MIS 2 vegetation was largely dominated by Juniperus sp.lTetraclinis articulata, with phases of ecological stress characterised by the expansion of Pinus halepensis and Quercus evergreen. C3 grasses were dominant throughout the record. In contrast, results from Gibraltar (intermittently spanning c.130-25ka BP) ~ showed no significant changes in vegetation dynamics during this period, with (Q) vegetation dominated by Pinus pinea, with lesser frequencies of Pistacia sp., Juniperus sp., and Quercus sp. Main conclusions: This thesis provides the first evidence of Last InterglacialGlacial vegetation dynamics in north-east Morocco and Gibraltar. Results from Morocco seem to show a good association with proposed climatic variations during this time interval, while specific vegetation shifts were also broadly synchronous with cultural transitions. In contrast, the Gibraltar record suggests that vegetation remained quite stable throughout the Last Glacial Period. As such, this thesis supports the suggestion that Gibraltar was an environmental refuge during the Last Glacial Period.
APA, Harvard, Vancouver, ISO, and other styles
46

Brunelle-Daines, Andrea. "Holocene changes in fire, climate and vegetation in the northern Rocky Mountains of Idaho and western Montana /." view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3061935.

Full text
Abstract:
Thesis (Ph. D.)--University of Oregon, 2002.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 170-178). Also available for download via the World Wide Web; free to University of Oregon users.
APA, Harvard, Vancouver, ISO, and other styles
47

Oksanen, P. O. (Pirita O. ). "Development of palsa mires on the northern European continent in relation to Holocene climatic and environmental changes." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514278895.

Full text
Abstract:
Abstract This thesis deals with the Holocene development of palsa mires in continental Europe, especially permafrost dynamics and its consequences on vegetation succession and peat accumulation. Peat deposits of four permafrost mires in boreal and subarctic northeastern European Russia and in northern oroboreal Finland have been studied using plant macrofossil analysis, (AMS) radiocarbon dating, dry bulk density and carbon content measurements. In addition, preliminary results are available from another palsa mire in northeastern European Russia. Modern vegetation has been investigated to support the interpretation of fossil plant assemblages. Earlier literature on vegetation, stratigraphy and dating of permafrost mires in Europe has been reviewed. The vegetation of palsa mires in general is well known. As a rule, palsas are dry ombrotrophic habitats, surrounded by wet flarks of variable trophic levels. There is a lack of information about vegetation in different small-scale habitats within palsa mires, which would have been useful when studying the permafrost-vegetation relationship. Although no functional indicator species of permafrost have been found, permafrost dynamics in peat stratigraphy can often be detected with high degree of probability based on changes in vegetation. Some plant assemblages and vegetation successions are typical on permafrost, while many species rarely grow on or near to permafrost. Relatively sudden changes between dry and wet mire environments and continuously dynamic conditions are good signs of permafrost impact. Also gradual changes towards drier conditions may be caused by permafrost; in these cases the timing of first permafrost aggradation is more difficult to ascertain and can usually be pronounced only in terms of maximum and minimum ages. Changes in peat accumulation rates and even hiatuses in stratigraphy are additional tools to support the interpretation on permafrost history at the studied sites. Dry organic matter and carbon accumulation rates for different developmental stages are calculated for the five studied mires. From earlier studies this information is not available. Accumulation rates in the permafrost environment are very variable: from zero or negative rates in old palsas to as high as 100 gC/m2yr in incipient palsas. On moist plateau palsas, permafrost flarks and in unstable permafrost conditions, accumulation continues at low to moderate rates. Thermokarst processes result in decomposition of former peat deposits with important consequences for the ecosystem carbon balance, especially in plateau palsa mires. Radiocarbon datings are available from 27 permafrost mires in continental Europe; only 5 of these are situated in Russia. Many of the published dates cannot be considered reliable as dating permafrost aggradation. Based on limited material, permafrost started to develop at latest about 3000 BP in mires of northern Russia and 2500 BP in Fennoscandia. Older permafrost formation is suggested for a few sites, but the evidence is insufficient to confirm this interpretation. The oldest preserved palsas are ca. 2500–2000 14C years old. Most of the modern palsas are less than 600 14C years old. Permafrost aggradation follows the major climate development in the Holocene, with formation being most active during the coldest stages. Global warming is expected to greatly affect the Arctic in the near future, which would imply significant changes in ecosystem functioning and carbon balance of permafrost mires. This study contributes to the understanding of the possible impacts of climate change on these ecosystems using paleoecological techniques.
APA, Harvard, Vancouver, ISO, and other styles
48

Gormally, Joshua. "Changes in riparian vegetation following release of reclaimed effluent water into the Santa Cruz River: As a corollary, the effects of channelization on vegetation in the Santa Cruz River." Thesis, The University of Arizona, 2002. http://hdl.handle.net/10150/278792.

Full text
Abstract:
Recharge has been conducted very efficiently for twenty-five years near Roger and Ina roads along the Santa Cruz River using reclaimed water. This project seeks to determine the composition of river vegetation due to the release of the reclaimed water, and as a corollary, to examine the effects of channelization on the vegetation of the Santa Cruz River. Using belt and line transects the vegetation along the Santa Cruz River was surveyed. Treatment with effluent was found to increase plant density, diversity, richness, cover, and incidence of exotic plants. Channelization was found to increase only plant richness and incidence of exotic plants. Furthermore, effluent encouraged the growth of tree plant types while channelization discouraged such growth. Recommendations were made regarding future release of effluent into the Santa Cruz River and future attempts to restore the once prolific, willow-cottonwood forests and mesquite forests.
APA, Harvard, Vancouver, ISO, and other styles
49

Louderback, Lisbeth A. "Changes in vegetation and human adaptation from the latest Pleistocene to late Holocene in the eastern Great Basin : the Blue Lake pollen record /." abstract and full text PDF (UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446788.

Full text
Abstract:
Thesis (M.A.)--University of Nevada, Reno, 2007.
"May 2007" Includes bibliographical references (leaves 138-151). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
APA, Harvard, Vancouver, ISO, and other styles
50

Leeper, Ronnie. "Near-surface Atmospheric Response to Simulated Changes in Land-cover Vegetation Fraction, and Soil Moisture over Western Kentucky." TopSCHOLAR®, 2009. http://digitalcommons.wku.edu/theses/108.

Full text
Abstract:
A series of land-use-land-cover-change (LULCC) based sensitivity experiments, including changes in vegetation type, fractional vegetation (FV), and soil moisture (SM), over Western Kentucky were conducted to investigate atmospheric response to land-use. The choice of land-use for this study was chosen in the context of Western Kentucky’s historical LULCC. For this study, vegetation types considered were grassland, forest, and bare soil with further variations in FV for grassland and forest at 25, 50, 75, and 100 % and systematic increases and decreases in volumetric SM of 0.05, 0.10, and 0.15 m3 m-3. To the author’s knowledge, this is the first assessment of its kind that incorporates these types of LULCC in a single study. In addition, typical anthropogenic land-use change often incorporates several types of LULCC. Moreover, this assessment provides a robust analysis of the impacts LULCC has on atmospheric processes over Western Kentucky. To simulate the importance of land-use on atmospheric processes, a well known meso-scale model developed by the National Center for Atmospheric Research (NCAR) and the Pennsylvania State University (PSU) MM5 coupled with an intermediately complex land surface model (LSM) Noah was used. The purpose of this research is to investigate the impact of multiple types of LULCC on planetary boundary layer (PBL) evolution, PBL stability, near surface 3D-wind fields, temperature, and moisture. Furthermore, it is anticipated that multiple types of LULCC will provide more insight into the complex nonlinear land-atmosphere interactions from atmospheric, air quality, and climatology perspectives. Modeling analysis revealed the importance of land-use on atmospheric processes. Changes in all three types of LULCC (land-cover, FV, and SM) altered the distribution of surface energy and moisture, PBL structure, 3D-wind fields, and PBL stability. In general, it was found that LULCC that enhanced (diminished) ET rates reduced (increased) sensible heat flux, atmospheric temperature and, and PBL heights below (above) control (CTRL). For instance, the conversion of land-cover from CTRL to grassland reduced 2 m temperature and PBL heights by 0.60 °C and 228 m respectively compared to CTRL due to an evaporative advantage (lower stomata resistance). Multiple types of land-use change were found to either offset or enhance overall modeled response to LULCC. A reduction in FV to 25 % over grassland diminished ET despite the evaporation advantage of grassland and increased 2 m temperature and PBL heights with respect to CTRL by 3.3 °C and 504 m. These results significantly altered horizontal and vertical wind fields, affecting moisture advection and the development of meso-scale circulations. Compared to CTRL, these differences were enhanced over drier soils, but muted over moist soils. Moreover, the impact of LULCC on atmosphere evolution was not only dependent on the type of LULCC, but also on the current state of other unaltered land surface features such as vegetation type, FV, and SM. Alterations to modeled PBL development, as a result of LULCC, can have important impacts on a region’s climatology and air quality. Simulated changes in typical PBL moisture and temperature through time can affect local and regional climatology. Depending on the type of LULCC, these alterations in climate may lead to localized cooling. In addition, it was further hypothesized that changes in PBL height can affect air quality. Given the capping inversion layer at the top of the PBL, changes in PBL heights can significantly affect air quality with lower (higher) PBL heights diminishing (enhancing) air quality. Moreover, this research prescribes the importance of considering LULCC in atmospheric assessments of climatology and air quality, including pollutant dispersion and trajectory modeling.
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the bibliographies on the topic 'Vegetation changes' for other source types:
Journal articles Books
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography