Tesi sul tema "Plant ecology"

En aquesta tesi presento quatre capítols, en els quals es discuteix com diferents espècies subarbustives interactuen amb plantes coexistents, sota règims variables d’estrès. Aquesta recerca ha estat centrada en ecosistemes de gran valor ambiental, ecològic i de conservació, i alhora sensibles als canvis ambientals, en quatre regions distintes situades en zones de latitud o altitud elevades. Per ordre latitudinal, els ecosistemes estudiats han estat: 1) el límit supraforestal dels Pirineus Centrals, situats en una zona temperada; 2) el gradient de successió primària d’un ecosistema situat en una zona boreal, a Finlàndia,; 3) el límit supraforestal situat a la zona subàrtica de Lapònia; i 4) la tundra situada en una zona de l’alt àrtic, al nord‐est de Grenlàndia . Els dos primers capítols es basen en una aproximació experimental i se centren en investigar com els subarbustos més comuns trobats prop del límit supraforestal interactuen amb plançons d’arbres de les espècies que formen el límit del bosc en dos ambients contrastats, i.e. el límit supraforestal subàrtic, i el límit supraforestal dels Pirineus Centrals. A més, donat que els arbres que viuen prop del límit de distribució són molt sensibles als canvis ambientals , especialment a l’augment de temperatures durant l’estació de creixement (Körner 2003), també s’ha investigat com podrien afectar el creixement dels plançons d’arbre i la seva supervivència al llarg de l’ecotò, diferents escenaris de canvis ambientals. El primer capítol es titula ‘Les interaccions arbre‐arbust i els canvis ambientals dirigeixen la dinàmica supraforestal a la zona subàrtica’, i s’hi exposa l’experiment de tres anys de durada que es va executar al ‘Parc Nacional d’Abisko’, en els Scandes subàrtics, al nord de Suècia; les plantes estudiades varen ser plançons de Betula pubescens i el subarbust Vaccinium myrtillus. En aquest estudi es va certificar la importància de les interaccions arbust‐arbre, tant facilitatives com competitives, com a elements clau en la dinàmica supraforestal subàrtica. A més, vàrem demostrar que la gran sensibilitat dels plançons a l’escalfament tenia fortes implicacions per la dinàmica supraforestal, tenint en compte l’escenari previst d’augment de temperatures en latituds elevades. També es va observar que les interaccions complexes entre arbusts i herbívors són claus per preveure canvis futurs. El segon capítol es titula ‘Els plançons d’arbres situats als límits supraforestals Pirinencs i subàrtics mostren respostes semblants a la presència d'arbustos i a les simulacions de canvis ambientals’. Aquí es presenta una comparació entre els resultats de l’experiment presentat en el primer capítol i els obtinguts en un experiment paral∙lel dut a terme durant un període de temps semblant prop del límit supraforestal en el ‘Parc Natural de l’Alt Pirineu’, als Pirineus Centrals catalans. Aquest experiment es va basar en el mateix disseny factorial que l’anterior estudi, però amb diferents espècies (i.e. plançons de l’arbre Pinus uncinata i l’arbust Rhododendron ferrugineum). Segons ens consta, és el primer estudi que avalua experimentalment les respostes de les plantes vers diferents escenaris ambientals en un ecosistema d’alta muntanya als Pirineus. En aquest capítol es presenten alguns mecanismes que ajudaran a comprendre la variabilitat recentment observada de les respostes locals de límits supraforestals de zones temperades i subàrtiques com a resultat del clima canviant, i també identifiquem alguns paral∙lelismes que poden utilitzar‐se per generalitzar les respostes a gran escala dels límits supraforestals al canvi climàtic. El tercer capítol se centra en els efectes d’un subarbust dominant (i.e. Empetrum nigrum) en plançons de Pinus sylvestris al llarg del gradient de successió primària en un ecosistema boreal en una illa emergent de la badia de Bòtnia, a Finlàndia. Aquest capítol s’anomena ‘Un arbust ericoide exerceix la doble funció de reclutar pins i els seus simbionts fúngics al llarg d’un gradient de successió primària’. Aquí hem mostrat que els efectes facilitadors i competidors dels subarbustos determinen fortament l’establiment de plançons i la seva colonització fúngica al llarg d’aquest gradient de successió. Segons ens consta, aquests són els primers resultats que demostren que un arbust ericoide micorrízic pot millorar tant el desenvolupament de l’arbre hoste ectomicorrízic com el dels simbionts fúngics de l’arbre. L’estudi presentat al quart capítol es va realitzar al llarg d’un gradient de nivositat en un ecosistema extrem de tundra àrtica al ‘Parc Nacional del nord‐est de Grenlàndia’, el Parc Nacional més gran del món. El capítol es titula ‘Interaccions vegetals i composició de la vegetació àrtica al llarg d’un gradient de nivositat al nord‐est de Grenlàndia’. Aquest ecosistema és probablement el més sensible i fràgil de tots els ecosistemes estudiats en aquesta tesi, donat que s’espera que a la costa est de Grenlàndia s’hi esdevinguin canvis substancials en el clima com a resultat de canvis destacables en els règims de precipitació de neu i de les temperatures (Brown i Mote 2009). Aquí es va avaluar la riquesa d’espècies de plantes, així com els patrons d’establiment i composició de diverses formes de creixement existents en comunitats vegetals àrtiques associades a una variació de la cobertura de neu durant els mesos d’hivern. Aquest estudi ajudarà a preveure la diversitat potencial i els canvis en la vegetació a la zona de l’alt Àrtic, si els règims de precipitació de neu canvien en el futur com es preveu.
In this thesis I present four chapters, and in all of them I discuss how dwarf shrubs interact with co‐occurring plants under varying regimes of stress. This research involved ecosystems of great environmental, nature conservation and ecological value, yet highly sensitive to environmental changes, in four contrasting cold regions at high altitude or high latitude. Following a latitudinal order, the selected ecosystems were: 1) a temperate alpine treeline in the Central Pyrenees; 2) a primary succession gradient in a boreal ecosystem in Finland; 3) a subarctic alpine treeline in Lapland; and 4) a high‐arctic tundra in north‐eastern Greenland. The first two chapters are based on an experimental approach and focus on how shrubs commonly found near the treeline interact with tree seedlings of treelineforming species in two contrasting environments, i.e. in a subarctic forest‐tundra ecotone in Lapland, northern Sweden, and in a more southern, temperate forestalpine pasture ecotone in the Central Pyrenees. In addition, since trees living near their limit of distribution are very sensitive to environmental changes, especially to increased temperature during the growing season (Körner 2003), we also assessed how distinct environmental change scenarios may affect tree seedling growth and survival across the ecotone. The first chapter is entitled ‘Shrub‐tree interactions and environmental changes drive treeline dynamics in the Subarctic’, where we explain the three‐year‐long experiment performed in the Abisko National Park, in the subarctic Scandes, Northern Sweden; the species studied were Betula pubescens tree seedlings and the shrub Vaccinium myrtillus. In this study we showed the importance of facilitative and competitive shrub‐tree interactions as drivers of subarctic treeline dynamics. Furthermore, we demonstrated that the great sensitivity of tree seedlings to warming had strong implications for treeline dynamics under the predicted warmer scenario at high latitudes, and we identified that complex interactions between shrubs and herbivores are critical to predicting future changes. The second chapter is entitled ‘Similar tree seedling responses to shrubs and to simulated environmental changes at Pyrenean and subarctic treelines’. Here we presented a comparison between the results obtained in the experiment presented in the first chapter and those obtained in a parallel experiment performed during a similar period near the treeline in the Alt Pirineu Natural Park, in the Central Pyrenees, Catalonia. This experiment was based on the same factorial design but with different species (i.e. Pinus uncinata tree seedlings and the shrub Rhododendron ferrugineum). To our knowledge, it is the first study which experimentally tests the responses of plants to distinct environmental scenarios in a high mountain ecosystem in the Pyrenees. In this chapter we presented some mechanisms for understanding the recently observed variability of local responses of both subarctic and alpine treelines to currently changing climate while identifying some commonalities that can be used to generalise large scale response of treelines to climate warming. The third chapter focuses on the effects of a dominant dwarf shrub (i.e. Empetrum nigrum) on Pinus sylvestris tree seedlings along a primary succession within a boreal ecosystem on an uplifting island in Bothnian Bay, Finland. This chapter is called ‘An ericoid shrub plays a dual role in recruiting both pines and their fungal symbionts along primary succession gradients’. Here we showed that facilitative and competitive effects of shrubs markedly determined tree seedling establishment and their fungal colonisation along this succession gradient, but in this chapter we did not relate these findings to any environmental changes. As far as we know, we presented the first finding that an ericoid mycorrhizal shrub may enhance both the performance of the ectomycorrhizal host tree and the tree’s fungal symbionts. The study presented in the fourth chapter was performed along a snow‐depth gradient in an extreme arctic tundra ecosystem in the Northeast Greenland National Park, the largest national park in the world. The chapter is entitled ‘Plant interactions and higharctic vegetation composition along a snow‐depth gradient in NE Greenland’. This ecosystem is probably the most sensitive and fragile among the ecosystems studied in this thesis as the eastern coast of Greenland is expected to experience substantial changes in climate due to marked changes in snow precipitation and temperature regimes (Brown and Mote 2009). Here we assessed plant species richness, establishment and composition patterns in distinct growth forms occurring in common arctic plant communities associated with varying snow‐depth during the winter season. This study will help to predict potential diversity and vegetation changes in the high Arctic if snow precipitation regime changes in the future as anticipated.

In this thesis a range of lattice based spatially explicit models of ecosystems are presented and their applicability to various ecological situations is demonstrated with emphasis on plant communities These mechanistic and individual based models which include coupled map lattices and cellular automata aim to produce ecological insights and testable results Models of both short and long term systems are developed with the former being potentially testable in the eld and the latter promoting understanding where experimentation is not feasible A range of graphical and numerical techniques were developed to investigate both plant and animal model ecosystems The starting point is a short term single species coupled map lattice which investigates popula tion structure arising from local competitive interactions The model concludes that increase of size variation with increasing density indicates the presence of competitive intraspecic asymme try This idea is applied to crop data where considerable asymmetry is identied emphasising the need for balancing crop yield and size consistency Multispecies extensions to this model focus on spatial patterning arising from biotic interac tions and various numerical techniques underline the asymmetrical relationship between long and short lived species Environmental heterogeneity is imposed on the plant species in a third version of the model via the incorporation of an explicit resource base The complex inter dependence of community and environment is highlighted and illustrated by a model of the evolution of seed sizes Through the application of cellular automata to forest and epidemiological systems the concept of memory such as age or stage structuring is shown to be vital in the generation of spatial structure in long term ecological systems Analytical investigations generate further insights and again emphasise the crucial role played by spatial extensiveness in the wide range of ecological situations considered here In conclusion lattice models are ideally suited to the study of ecosystems

Differing plant canopy structures between the sexes of the dioecious Cannomois congesta (Restionaceae) were found to be the result of the destructive pre-dispersal seed predation methods used by the four-striped grass mouse (Rhabdomys). Mature, reproductive culms on female plants were felled down (mid way along the culm) in large numbers by Rhabdomys in order for it to access the seeds held terminally on culms. Male plants were largely unaffected due to their lack of seeds. Seeds acquired through culm-felling by Rhabdomys were all eaten shortly after their discovery, leading to significant seed mortality each year and reducing the rate of seed dispersal by ants (myrmecochory). I studied the physiological effects of culm-felling by Rhabdomys in C. congesta. Firstly I investigated nutrient resorption from senescing culms and considered the effects of reproductive effort (higher in females) and sex-specific nutrient losses. I found that nutrient resorption from mature culms was highly efficient in both sexes. Culm-felling by Rhabdomys lead to the loss of pre-senescent culm tissue in females and therefore lead to the loss of a significant proportion of potentially resorbed nutrients. Nutrient resorption was found not to be flexible as a strategy to compensate for higher reproductive costs/nutrient-losses in females. This was possibly due to nutrient resorption occurring near is physiological maximum. Plant photosynthetic performance was also investigated using stable isotopes and gas exchange and was found to be similar in both C. congesta sexes throughout the year. The influence of culm-felling by Rhabdomys on female micro-climate also did not appear to have a significant influence on photosynthetic performance between sexes. There was a general lack of evidence to suggest compensatory physiological changes or reductions in fitness (photosynthetic capacity/growth/reproduction) in females due to higher reproductive costs/nutrient-losses. The lack of physiological differences and the fact that females supported a greater number of culms relative to males suggested that other compensatory mechanisms could exist. Phenological differences were discovered and could be important in allowing flexibility between sexes to best use available resources for their specific sexual requirements. Another possibility is that compensatory growth occurred in females at the cost of rhizome-stored nutrients. This has been shown to occur in graminoids after high levels of herbivory (Bryant et al 1983).

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2008.
Title from PDF t.p. (viewed on Jul 28, 2009). Source: Dissertation Abstracts International, Volume: 69-12, Section: B, page: 7260. Adviser: Heather L. Reynolds.

Invasive plants are widely cited as a major threat to native plant communities, and the correlation between plant invasions and a subsequent decline in native species is well documented at some scales. However, one outstanding question is the degree to which invasive species are a driver of native plant declines versus a correlate of other drivers, such as habitat disturbance. These two hypotheses to explain the dominance of invasive species in communities have been termed the ‘driver’ and ‘passenger’ models, respectively. In order to understand the impacts of plant invasion on native plants we need more studies that consider the role of correlated environmental predictors, which may play unseen roles in the response and recovery of native plant communities frequently attributed to invasion alone. Using a large database of plant community and environmental data from sites across Southern Ontario, I used path analyses to examine the direct and indirect relationships between disturbance, exotic and native plant richness, and relative abundance. Counter to my initial predictions, I found support for both the partial passenger and partial driver models of invasive dominance, while full passenger models were outright rejected. The causal hypotheses consistent with the data indicated significant relationships between native and exotic species richness and native and exotic relative abundance across models. An exploratory analysis, which examined species-specific models, found that the data was consistent with seven out of twelve causal hypotheses. Models that could not be rejected were split almost evenly across full passenger, partial passenger, and partial driver models. Model support varied according to the species included in the dataset suggesting that the best fit underlying model of invasive dominance likely varies by species. While the partial passenger and partial driver models were recurrently consistent with the data, no single model described the underlying patterns of invasive dominance across all systems.

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2006.
"Title from dissertation home page (viewed July 11, 2007)." Source: Dissertation Abstracts International, Volume: 67-08, Section: B, page: 4208. Advier: Keith Clay.

The main aim of the thesis is to explore the interaction between pattern and process in vegetation ecology using a variety of mathematical and statistical methods. Of particular interest is what information about the dynamics of the underlying system can be gained through a single spatial snapshot, such as an aerial photograph or satellite image. The hypotheses are related to seagrass ecology, whose growth is primarily clonal and broadly exists as a monoculture and thus makes it an ideal candidate to study these interactions. The thesis broadly concerns two forms of spatial pattern and the underlying dynamics that give rise to them. The first concerns regular pattern formation, where the pattern has a characteristic length scale. Examples are abundant in natural systems, such as mussel beds, semi-arid ecosystems as well as seagrass. The developments concerned with regular pattern formation include methods of detection in a large spatial dataset, a novel stochastic model of vegetation that produces regular pattern with plausible mechanisms, the development of a new methodology to fit regular spatial pattern data to the model and the impact as well as evolutionary mechanisms of regular patterning in the presence of disease. The second form of spatial pattern exhibited in a wide variety of sessile species is scale-free or fractal patterning. Certain scaling heuristics, such as the boundary dimension of a vegetation cluster or the power-law exponent of the patch-size distribution have been used to infer properties of the dynamics. We explore these heuristics using a variety of plausible models of vegetation growth and find the circumstances under which there is a clear relationship between the spatial heuristics and the dynamics. These are then supplemented by viewing vegetation growth as an aggregation process. A novel model of vegetation aggregation with death is produced to find the origin of the ubiquitous power-law patch-size distribution found in nature. Finally the impact of scaling on the spread of disease is explored.

Landscape ecology has been defined in a variety of different ways, but the common theme is the study of the ecological effects of ecosystem spatial patterning. Since the long history of landscape alteration has created novel systems with unknown dynamics, new tools are necessary to understand, manage and restore human dominated landscapes, preventing the loss of biodiversity. Among all, habitat fragmentation is the main process which affects biodiversity especially in human dominated landscapes. This thesis is based on three research papers concerning the evaluation of plant species diversity in fragmented and secondary plant communities. Moreover, the effect of natural reforestation process on biodiversity of secondary plant communities was investigated through a review paper. Focusing in each paper on different specific objectives due to the variability of landscape context and habitat type, the overall goal of this work was to detect spatial and management components influencing vascular plant species diversity. Through the different tools and methodologies used in each case study, we want to demonstrate the great applicability and versatility of landscape ecology approach both in theory and practice. The analyses were conducted on three fragmented secondary plant communities, i.e. meadow-pastures (Paper II), recent secondary woodlands (Paper III) and hedgerows (Paper IV), scattered in a dominant matrix type. Paper III was done during the collaboration with the Technische Universität of Berlin (Department of Ecology) during my research period abroad. The case studies were conducted both at patch and at landscape level, considering actual field data and management variables of the secondary plant communities surveyed (patch level) and the analysis of landscape asset around (landscape level). The latter was performed by GIS analysis. Regression models were used to relate plant species diversity to spatial and management variables. The survival of species depends on landscape dynamics and on spatial plant community configuration (Paper I). More specifically, where environmental site condition and management variables have not impact on secondary community variability and they did not differ between the surveyed communities, plant species diversity can be deeply influenced by spatial variables (Paper II and III). On the contrary, where management variables have a strong effect on secondary community alteration, i.e. in agrarian hedgerows, this effect is independent from the landscape assets of the different surveyed sites (Paper IV). In general, the integrative methods used by the “landscape ecology approach” allowed us to quantify in a holistic way complex natural-cultural patterns and processes on different time-space scales that influenced vascular plant species diversity.
L’ecologia del paesaggio studia l’influenza dei pattern spaziali sui flussi di specie. La continua frammentazione ed alterazione delle fitocenosi in paesaggi antropizzati rende necessario comprendere le dinamiche delle comunità vegetali che caratterizzano il paesaggio antropizzato, cercando di evitare il più possibile la perdita di diversità biologica che spesso è conseguenza di tali trasformazioni. La mia tesi è basata su tre articoli di ricerca riguardanti l’analisi della diversità della flora vascolare in fitocenosi secondarie e frammentate. In un lavoro di review invece, è stato analizzato l’effetto della riforestazione spontanea su fitocenosi secondarie a seguito dell’abbandono delle pratiche agricole. Ciascun lavoro è stato caratterizzato da specifici obiettivi, adattati in base alla variabilità del paesaggio e del tipo di fitocenosi secondaria indagata. Ciononostante, l’obiettivo comune di questa tesi è stato quello di esaminare l’influenza delle variabili di paesaggio e gestionali sulla variabilità della flora vascolare, tramite l’utilizzo di metodologie e strumenti propri dell’ecologia del paesaggio. Le analisi sono state effettuate in tre fitocenosi secondarie e frammentate, i.e. pascoli (Paper II), neoformazioni boschive (Paper III) e siepi rurali (Paper IV), inserite all’interno di differenti matrici paesaggistiche. Il terzo caso di studio (Paper III) è stato sviluppato in collaborazione con la Technische Universität di Berlino durante il mio periodo di dottorato all’estero. Le analisi sono state effettuate sia a livello di patch che di paesaggio, considerando quindi congiuntamente i rilievi floristici e le variabili gestionali (livello di patch) e l’analisi dell’assetto paesaggistico attorno alle fitocenosi indagate (livello di paesaggio). Le analisi di paesaggio sono state effettuate tramite strumenti GIS. Vari modelli di regressione sono stati utilizzati per mettere in relazione la diversità di specie vascolari con le variabili di paesaggio e gestionali. La sopravvivenza delle specie dipende profondamente dalle dinamiche del paesaggio e dalla sua configurazione spaziale (Paper I). Più nello specifico, nei casi di studio in cui le variabili stazionali e gestionali sono ininfluenti o omogenee in tutti i siti, la diversità di specie vascolari è profondamente influenzata dalle variabili spaziali (Paper II e III). Dove invece la gestione altera sostanzialmente l’equilibrio della fitocenosi, l’effetto è indipendente dalle variabili di paesaggio (Paper IV). In generale, i principi ed i metodi dell’ecologia del paesaggio che sono stati utilizzati nei casi di studio presentati, hanno permesso di quantificare precisamente i processi e le dinamiche che influenzano la diversità di specie vascolari a differnti scale spaziali e temporali.

Ecological systems are inherently dynamic, and a primary way in which they are dynamic is through time. Individual organisms, populations, communities, species interactions, and ecosystem functions all follow a temporal progression from the past, to the present, and into the future. This temporal progression can occur over the course of minutes, hours, days, weeks, months, years, decades, or various other timescales. In this sense, temporal dynamics are an intrinsic property of all biological systems. In fact, one of the most prominent signals of recent global climate change is the significant change in the timing of biological events for a diversity of organisms. In light of this widespread pattern, there is a renewed interest in understanding the multifaceted importance of time in ecology. In this dissertation, I investigate the temporal ecology of a subalpine ecosystem, specifically focusing on flowering plant communities and plant-pollinator interactions. I examine the temporal dynamics of this system over multiple decades in response to ongoing climate change as well as over shorter time scales within a growing season. Using a 39-year record of flowering phenology, I show that species-specific shifts in the timing of flowering in response to climate change can substantially reshape a subalpine plant community over this time period. Community phylogenetic analyses reveal that these changes are largely independent of evolutionary history. Using a laboratory experiment, I show that the timing of an important harsh abiotic event-low temperatures that cause frost damage to plants-can differentially affect flowering plant species, with implications for plant demography, community structure, and interactions with pollinators. Finally, I show that plant-pollinator interactions exhibit substantial within-season temporal turnover, and that this temporal flexibility of plant-pollinator interactions from one week to the next is consistent and predictable across years. Taken together, this dissertation provides a multifaceted investigation of the temporal ecology of plant communities and plant-pollinator interactions, revealing the important consequences of ecological timing at short-term and longer-term scales.

The morphology, phenology and stem demography of devil's club and thimbleberry were examined to elucidate their niche utilization strategies. The study was conducted in the Kitimat River valley in west central B.C. during the 1986 and 1987 growing seasons. Thimbleberry was sampled in a girdled alder site and a nongirdled alder site, whereas devil's club was sampled in an old growth forest. The variation in the plant characters, as summarized by principal components axes, was apportioned within and among clones, between sites, years, and species. Except for the thimbleberry vegetative phenology, within-sites differences accounted for most variation and variation between-sites often exceeded that between years. Moreover, between-species differences accounted for less variation than within-species differences for morphology and phenology. The variation in plant characters was also examined in relation to canopy cover, soils and adjacent vegetation using multivariate methods. The rate of vegetative development for devil's club in 1986 increased as canopy cover decreased; other environmental measures were uncorrelated with devil's club. Both vegetative and reproductive rates of development increased with disturbance due to girdling and increasing moisture for the combined girdled and ungirdled thimbleberry data set. Similarly, morphdodcal size was greater for the combined thimbleberry data set with increasing moisture and dsturbance. Environmental correlations were reflected differently within-sites, however, with rates of development, plant size and the number of flowers decreasing with increasing moisture at the nongirdled thimbleberry site. The relationship between plant characters was also assessed. Phenology and morphology were correlated for both devil's dub and thimbleberry; stem development began earlier and was more rapid with increasing stem size. Demography and phenology were unrelated. Both species displayed different niche utilization strategies; thimbleberry being more flexible than devil's club. In contrast to devil's dub, thimbleberry is morphologically a phenologically responsive to disturbance and is mizomatous rather man stoloniterous. Stems and lateral branches also had several phonological and developmental possibilities. This flexibility imparted an advantage to thimbleberry in the fluctuating conditions of its earlier successional niche. The differing correlation structure between and within thimbleberry sites suggests that several scales of observation are necessary to clarify plant-environment relationships. Moreover, as environmental characters interact differently with plants from site to site, management must be site specific. Alder girdling may be a judicious management technique at drier sites, where thimbleberry is not as prolific under an open canopy.
Science, Faculty of
Botany, Department of
Graduate

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Variação intra-específica na fenologia de espécies de sub-bosque de Floresta Atlântica e sua relação com variáveis microambientais - Fatores abióticos, como a umidade relativa, temperatura e luz, influenciam o estabelecimento, desenvolvimento e reprodução das espécies vegetais florestais. Entretanto é necessária a coleta de parâmetros estruturais, microclimáticos e microambientais para a caracterização dos ambientes nos quais as plantas se desenvolvem. Neste contexto, o presente trabalho objetivou avaliar a influência de fatores do microambiente na resposta fenológica de espécies vegetais componentes do sub-bosque de floresta Atlântica, em Ubatuba, SP. Procuramos responder as seguintes perguntas: i) As plantas de sub-bosque podem ser agrupadas em relação aos ambientes de luz: borda natural, clareira e interior sombreado da floresta?; ii) Existem variações intra-específicas na fenologia das espécies de sub-bosque de Floresta Atlântica de acordo com o ambiente de luz em que foram agrupadas?; iii) A intensidade das respostas fenológicas (número de estruturas reprodutivas produzidas) está relacionada aos locais de luz?; iv) Outras condições microclimáticas, como temperatura e umidade relativa, e microambientais, como a densidade da vegetação, também influenciam a fenologia das espécies? Para tanto a fenologia e a produção de estruturas reprodutivas de quatro espécies abundantes do sub-bosque foram acompanhadas de janeiro de 2009 a abril de 2010. Indivíduos foram selecionados em ambientes previamente determinados como borda natural (beira de rio), clareira e interior de floresta atlântica. Medidas periódicas das variáveis microclimáticas (temperatura, umidade relativa, PAR) e microambiental (abertura do dossel) próximas aos indivíduos amostrados foram realizadas. Medidas estruturais...
Phenological intraspecific variation of Atlantic Forest understory species and its relation to microenvironmental variables - Abiotic factors such as humidity, temperature and light influence the establishment, development and reproduction of forest plant species. However, it is necessary to collect structural, microclimatic and microenvironmental parameters to characterize the environments in which plants grow. In this context, this study evaluated the influence of the microenvironment in the phenological response of understory plant species components of the Atlantic Forest in Ubatuba, São Paulo State. We tried to answer the following questions: i) Can the understory species be grouped in relation to natural edge, gaps and interior microenvironments? ii) Do exist intraspecific variations in the phenology of understory species of Atlantic forest in accordance with the light environment in which they were grouped? iii) Do the intensity of phenological responses (number of reproductive structures produced) related to local condictions of light?; iv) Do other microclimatic (such as temperature and relative humidity) and microenvironmental (density vegetation) conditions also influence the phenology of species? The phenology and reproductive structures production of four abundant species of the understory were followed from January 2009 to April 2010. Individuals were selected in environments previously determined as natural edge (riverside), gap and interior. We performed periodic measurements of microclimatic (temperature, relative humidity and PAR) and microenvironmental variables (canopy openness) near the sampled individuals. Structural measures (CAS, CAP, plant height, crown height from the ground and crown size) and microenvironment characterization (canopy height, understory vertical density, distance... (Complete abstract click electronic access below)

The analysis of presence/absence data of plant species by regression analysis is the subject of this thesis. A nonparametric approach is emphasized, and methods which take into account correlations between species are also considered. In particular, generalized additive models (GAMs) are used, and these are applied to species’ responses to greenhouse scenarios and to examine multispecies interactions. Parametric models are used to estimate optimal conditions for the presence of species and to test several niche theory hypotheses. An extension of GAMs called vector GAMs is proposed, and they provide a means for proposing nonparametric versions of the following models: multivariate regression, the proportional and nonproportional odds model, the multiple logistic regression model, and bivariate binary regression models such as bivariate probit model and the bivariate logistic model. Some theoretical properties of vector GAMs are deduced from those pertaining to ordinary GAMs, and its relationship with the generalized estimating equations (GEE) approach elucidated.
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This project described the vegetation of a stretch of the Parana River and investigated which natural or human-imposed factors might be controlling its characteristics, its capacity for biodiversity support and its potential to provide an economic resource. This information is of value in the planning of management strategies aiming to conserve biodiversity and develop sustainable ways in which the floodplain resources can be utilised. Central to this study were the surveys of vegetation and environmental characteristics of aquatic, terrestrial and transitional habitats of the Parana floodplain near Porto Rico. These produced extensive data sets which helped to reveal the types of vegetation-environment relationships structuring the floodplain plant communities. To complement this investigative approach, three aspects of the functioning of floodplain vegetation were chosen for closer study. These were the impacts of livestock grazing on wetland and island vegetation, competitive interactions between pairs of free-floating aquatic plant species and the role of aquatic macrophytes in contributing carbon to aquatic food webs. Three major community types were identified in the aquatic habitats of the floodplain, one which included Eichhornia azurea in mixture with several free-floating and emergent species, a second in which E. azurea was strongly dominant and a third comprised purely of submerged species. Two strongly contrasting broad vegetation communities were identified at bank and shore environments. Polygonum and Ludwigia species were important in one group and Poaceae, creepers, woody plants and ferns in the other group. Sub-groups of these communities could also be suggested, but these are less distinct. Most of the floodplain sites supported a Poaceae-creeper community type with the remaining sites supporting a community indicated by Polygonum species. The Poaceae group was comprised of a number of sub-communities in which the importance of Poaceae relative to other species varied. The aquatic vegetation communities differed structurally with contrasting community biomass, canopy height, canopy cover, species richness and stem density. They were associated with waterbodies with different water depth and pH and different sediment nitrogen and phosphorus contents. Water flow rate category and underwent light availability also differed between the sites that tended to support the different vegetation types. The two major bank and shore vegetation communities differed in canopy cover, in the soil nitrogen, phosphorus and calcium levels with which they were associated and in the steepness of the bank on which they tended to grow. Floodplain vegetation communities contrasted in species richness and differed in the soil nitrogen and calcium levels and river systems with which they were associated.

Invasive exotic species threaten native biodiversity, alter ecosystem structure and function, and annually cost over $100 billion in the US alone. Determining the ecological traits and interactions that affect invasion success are thus critical for predicting, preventing, and mitigating the negative effects of biological invasions. Native herbivores are widely assumed to facilitate exotic plant invasions by preferentially consuming native plants and avoiding exotic plants. Here, I use freshwater plant communities scattered broadly across the Southeastern U.S. to show that herbivory is an important force driving the ecology and evolution of freshwater systems. However, native consumers often preferentially consume rather than avoid exotic over native plants. Analyses of 3 terrestrial datasets showed similar patterns, with native herbivores generally preferring exotic plants. Thus, exotic plants appear defensively nave against these evolutionarily novel consumers, and exotic plants may escape their coevolved, specialist herbivores only to be preferentially consumed by the native generalist herbivores in their new ranges. In further support of this hypothesis, a meta-analysis of 71 manipulative field studies including over 100 exotic plant species and 400 native plant species from terrestrial, aquatic, and marine systems revealed that native herbivores strongly suppressed exotic plants, while exotic herbivores enhanced the abundance and species richness of exotic plants by suppressing native plants. Both outcomes are consistent with the hypothesis that prey are susceptible to evolutionarily novel consumers. Thus, native herbivores provide biotic resistance to plant invasions, but the widespread replacement of native with exotic herbivores eliminates this ecosystem service, facilitates plant invasions, and triggers an invasional meltdown. Consequently, rather than thriving because they escape their co-evolved specialist herbivores, exotic plants may thrive because their co-evolved generalist herbivores have stronger negative effects on evolutionarily nave, native plants.

In the spring of 2007 the Kuba Dam in Nätra Stream was removed for restoration purposes, mainly to give free passage to migrating fish. This action gave an opportunity to study the effects of dam removal on organisms both on land and in water, a type of study which is in demand for planning purposes of future dam removals. This study focuses on the effects upon the vegetation along the stream where the former reservoir was situated. Willow cuttings and sunflower seeds were used as phytometers to assess the growth conditions one year after removal at three different elevation levels at four different sites along the Nätra Stream. The reaches studied were the former reservoir of Kuba Dam (Site A), the area just downstream of this former dam (Site B), further upstream in the reservoir of the existing Nyfors Dam (Site C), and even further upstream at Myreforsen, a reference area not affected by dams (Site D). Willow cuttings and sunflower seeds were planted at three different riparian levels at the sites in June and left to grow until August when growth results were collected. Many of the cuttings had died but statistically significant differences between sites could still be detected. They showed that the former reservoir shorelines in Kuba (Site A) had a plant growth significantly higher than the other regulated site. In other words, it was no longer equal to an existing reservoir but not yet similar to a free-flowing reach. The western side of the stream at this site had a higher growth than the eastern side and also higher than all the other sites. As for the three levels, the results showed a higher growth at the lowest elevation level at site A than all at the other levels and sites. This suggests that a combination of good access to sunlight and nutrients and fine-grade moist substrate results in a good growing conditions nearer the water in this former reservoir. The results for the sunflower seeds showed that the reference reach had a higher colonization success than the other sites.

Utrivningen av Kubadammen i Nätraån våren 2007 gav möjlighet att studera och följa upp hur en sådan förändring påverkar organismer på land och i vatten både uppströms och nedströms den tidigare dammen. Denna typ av undersökningar efterfrågas allt mer i och med att fler och fler dammar rivs av olika anledningar. I Kubadammens fall hade dammen förlorat sin ursprungliga roll och de fördelar som magasinet förde med sig för bland annat rekreation vägde inte längre upp dämningens negativa effekter på vattendragets ekosystem, till exempel som vandringshinder för fiskar. I denna studie har fokus lagts på vad som sker med vegetationen på stränderna längs det forna vattenmagasinet efter rivning. Med hjälp av videkvistar och solrosfrön som fytometrar undersöktes tillväxten ett år efter rivning på tre olika strandnivåer på fyra olika lokaler längs Nätraån. Dessa lokaler var Kubadammens gamla magasin (Lokal A), området direkt nedströms den före detta dammen (Lokal B), den nuvarande Nyforsdammens magasin (Lokal C) uppströms den före detta dammen, samt en referenssträcka vid Myreforsen (Lokal D) uppströms alla Nätraåns dammar och därmed ej påverkad av dämningseffekter. Videkvistarna och solrosorna planterades på tre nivåer på de olika lokalerna i juni och tilläts växa till augusti då tillväxtresultaten samlades in. Många kvistar hade dött under tiden men tillräckligt många överlevde för att det skulle gå att läsa ut statistiskt signifikanta skillnader i tillväxt. Resultaten visade att det före detta magasinet vid Kuba (Lokal A) hade en signifikant högre tillväxt än de andra lokalerna, vilket visar på att tillväxtförhållandena för vide varken liknar dem i ett befintligt magasin eller på en orörd sträcka eller nedströmssträckan, utan var betydligt mer gynnsamma. På denna lokal växte fytometrarna dessutom signifikant bättre på den västra sidan än på den östra sidan. När man ser till de tre nivåerna så växte videkvistarna i nivån närmast vattnet i det före detta magasinet vid Kuba bättre än på de övriga nivåerna på samma lokal och på de övriga lokalerna. Troligtvis beror detta på en kombination av öppenhet som ger bra tillgång till solljus, bra näringstillgång, substratets finkornighet och förmåga att hålla kvar fukt närmare vattnet. Resultaten av solrosfrönas etablering visade på att referenssträckan hade en högre etablering än övriga lokaler.

The evolution of non-flying mammal pollination has given rise to a broad suite of adaptive plant traits including dull coloured and geoflorous flowers, copious sucrose rich nectar, nocturnal anthesis and nectar production and a musky odour. The Fynbos endemic, Liparia parva (Fabaceae) has been recognised to exhibit several of these traits. Based on this observation, field studies were carried out on the Cape Peninsula, South Africa, to investigate the prediction that L. parva is rodent pollinated. Several lines of evidence indicate that flowers of L. parva are visited by rodents. These include; the presence of Liparia pollen in the faeces of live trapped rodents; observations of captive rodents selectively foraging at flowers of L. parva; floral debris underneath L. parva plants; and video footage captured of a rodent visiting L. parva flowers in the field. However, a strong plant-pollinator relationship was apparent only in the Cape spiny mouse, Acomys subspinosis. Captive Acomys foraged non-destructively at flowers of L. parva, becoming visibly dusted with pollen. The exclusion of rodents from flowers resulted in a significant reduction in seedpod set, indicating rodents do contribute to pollination success in L. parva. Additional evidence that L. parva is adapted to pollination by rodents includes nocturnal floral anthesis and large amounts of total nectar in inflorescences. The findings of this study provide substantial evidence for rodent pollination in L. parva and thus represent the first report of rodent pollination in a legume.

This thesis presents laboratory investigations on the competitive interactions which take place within and between bethylid parasitoids. Part one investigates the compatibility of three bethylids (Cephalonomia hyalinipennis, Cephalononlia stephanoderis and Prorops nasuta) for biocontrol releases against the principal pest of coffee, the coffee berry borer (CBB), Hypothenemus hampei. Cephalonomia hyalinipennis is able to hyperparasitise and consume pupae of C stephanoderis and P. nasuta. Cephalonomia stephanoderis also engages in intra-guild predation, consuming pupae of C hyalinipennis. In contests for CBB hosts, fatal fighting occurs in 69% of inter-specific replicates but never occurs in intra-specific replicates. This suggests that interspecific competition is stronger than intraspecific competition and that species coexistence may be compromised. Cephalonomia tephanoderis is the superior interspecific contestant while P. nasuta is the least successful and never kills an opponent. Where CBB infested coffee berries are provided to the three bethylids, coexistence between species is possible, but rare, within a single coffee berry. Prorops nasuta is the most successful species in interspecific replicates and replicates containing C. hyalinipennis generally have low production, regardless of the species combination added. Part two investigates contest interactions, the variables that influence contest outcome between Goniozus nephantidis females and chemical release. Prior ownership and difference in contestant weight have positive influences on contest outcome. Host weight positively influences the outcome of contests between two 'owners' and 'intruder' take-over success increases when intruders are older than owners. Seven bethylid species are found to release volatile chemicals when stressed. A pilot study identifies the volatile chemical in G. nephantidis and employs Atmospheric Pressure Chemical Ionisation-Mass Spectrometry for real-time analysis of chemical release during contest interactions. The appendix contains an advanced investigation using this technique. Bethylids are useful model organisms for the study of competitive interactions but appear to be generally ineffective as biological control agents.

This thesis examines Greater Melbourne’s indigenous plants movement from the 1930s to the early twenty first century. It demonstrates the important scientific and educational role of the public intellectual, Professor John Turner, and of the Melbourne University Botany School which he led for thirty five years. The case study of the movement within the City of Sandringham and its successor the City of Bayside reveals how the inhabitants of an urbanised are responded to threats to the indigenous trees and wildflowers of their neighbourhood, stimulating botanists to assist them and using political means in order to achieve their conservation objectives. The thesis draws upon a range of local archives, conservation literature and private papers.

Thesis (Ph. D.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on June 4, 2009) Vita. Includes bibliographical references.

Background information, essential to a full appreciation of the research presented in the thesis, is submitted in Chapters Two, Three and Four in the form of literature reviews. Chapter Two includes a review of the geology, climate, soils, past management, vegetation history and nature conservation value of Bodmin Moor. The chapter culminates by discussing the proposed future management of grazing on Bodmin Moor. Chapter Three comprises a review of the mechanisms by which grazing affect vegetation. Particular reference is made to the effects of 7 General Introduction variation in grazing practices and interactions between grazing and other environmental variables. Chapter Four provides a review of successional processes with particular reference to the effects of grazing on upland plant community succession and the limits of current knowledge of grazing management in upland habitats. Chapter Five presents the results of phytosociological classification and explores the relationships between environmental variables and vegetation. Chapter Six examines spatial variation in the seed bank of Bodmin Moor in a range of communities at different depths. Chapter Seven presents the results of a Countryside Stewardship monitoring scheme established on Bodmin Moor North SSSI. Chapter Eight investigates the effects of variation in timing, frequency and severity of defoliation, on Molütia caerulea, along a soil moisture gradient. Chapter Nine reviews the preceeding work focusing on the overall implications of the thesis. The structure of the thesis is presented diagrammatically in Figure 1.1.