Thèses : « Temperate and boreal trees »

1

Lin, Jianhong. « Ecophysiological modelling of leaf and wood phenology in temperate and boreal forest trees ». Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASB059.

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La phénologie joue un rôle crucial dans le fonctionnement des plantes et les services écosystémiques. La recherche sur la phénologie des arbres est très active, et je me suis attaché dans cette thèse à traiter des questions rarement abordées par la communauté, relatives à la représentation de la variabilité intra-populationnelle de la phénologie, et à la phénologie de formation du bois. À ce jour, la plupart des études phénologiques se sont concentrées sur la phénologie des feuilles à l'échelle des populations, en négligeant les organes non foliaires, tels que le bois et la variabilité entre les individus. Ces lacunes dans les connaissances posent des défis pour prédire avec précision les réponses phénologiques des arbres au changement climatique. Dans cette thèse, j'ai développé le premier modèle phénologique visant à simuler la variabilité intra-populationnelle (WPV) du débourrement dans des populations d'arbres (Chapitre II). Le modèle WPV a été calibré et évalué à l'aide de 48 442 observations de débourrement, collectées entre 2000 et 2022 pour trois espèces d'arbres feuillus tempérés : le charme (Carpinus betulus), le chêne (Quercus petraea) et le châtaignier (Castanea sativa). Les simulations rétrospectives couvrant la période de 1961 à 2022 ont montré un avancement de la date de débourrement en réponse au réchauffement climatique en cours (Chapitre II). De plus, le modèle WPV a été utilisé pour simuler les tendances des dommages causés par les gelées tardives au printemps au cours des six dernières décennies. Les résultats ont montré une diminution générale de la fréquence et de l'ampleur des dommages causés par les gelées tardives dans les populations de chêne à travers la France, en raison de l'avancée plus rapide du dernier gel de printemps par comparaison à l’avancée de la date de débourrement. Il est important de noter que les tendances de la fréquence et de l'ampleur des dommages causés par les gelées tardives au printemps ne sont pas cohérentes (Chapitre III). Au-delà de la phénologie des feuilles, j'ai calibré et validé un modèle de phénologie du bois prédisant la date d’arrêt de l'élargissement des cellules du xylème (cE), en utilisant la base de données GLOBOXYLO, qui documente l'occurrence des stades phénologiques de la formation du bois (Chapitre IV). Cette étude a porté sur trois espèces de conifères de l'hémisphère Nord, à savoir le pin sylvestre (Pinus sylvestris L.), l'épicéa commun (Picea abies Karst) et l'épinette noire (Picea mariana Mill.), totalisant 718 observations de cE sur 130 site-années. Le modèle a montré de bons résultats pour toutes les espèces, avec une erreur quadratique moyenne de 9,2 ± 1,3 jours. Les résultats indiquent que la température et la photopériode jouent un rôle crucial dans la cessation de la croissance des tiges chez l'épicéa commun et l'épinette noire. Cependant, pour le pin sylvestre, seule la température semble avoir une influence significative. De plus, des facteurs ontogénétiques, tels que le nombre total de cellules du cerne, ont également été identifiés comme influençant la cessation de la croissance des tiges pour toutes les espèces de conifères étudiées (Chapitre IV). Enfin, j'ai intégré un modèle complet de la phénologie de formation du bois, incluant un module simulant la reprise printanière de formation du bois (Delpierre et al., 2019) et le modèle de cessation de la phénologie du bois développé dans le Chapitre IV, dans CASTANEA, un modèle mécaniste de fonctionnement des forêts. Les résultats ont révélé des différences significatives dans les prédictions de croissance du bois en fonction de la définition de la période de croissance du bois. Cela souligne l'importance d'incorporer des modèles de phénologie du bois dans les modèles d'écosystèmes terrestres pour utiliser des estimations fiables de la durée de croissance du bois, et améliorer les estimations de biomasse produite et de carbone séquestré par les forêts (Chapitre V)
Phenology plays a critical role in plant functioning and ecosystem services, serving as a key indicator of temperate and boreal ecosystems' responses to climate change. Research into tree phenology is very active, and in this thesis, I addressed questions rarely addressed by the community, relating to the representation of intra-population variability in phenology, and the phenology of wood formation. To date, most phenological studies have focused at the population level, primarily on leaf phenology, while largely overlooking the substantial variability among individual trees and the phenology of non-leaf organs, such as wood phenology. These knowledge gaps pose challenges for accurately predicting tree phenological responses to climate change. In this thesis, I developed the first model to simulate the within-population variability (WPV) of budburst in tree populations (Chapter II). The WPV model was calibrated and evaluated using 48,442 budburst observations from 2000 to 2022 in three major temperate deciduous tree species, namely, hornbeam (Carpinus betulus), oak (Quercus petraea) and chestnut (Castanea sativa). Retrospective simulations over the period 1961–2022 showed earlier budburst in response to ongoing climate warming. However, the simulations revealed no significant changes in the duration of budburst (DurBB, i.e., the time interval from BP20 to BP80, representing the dates when 20% and 80% of trees in a population have reached budburst) due to the lack of a significant temperature increase during DurBB (Chapter II). Additionally, the WPV model was used to simulate trends in late spring frost damage over the past six decades. The results showed a general decrease in the frequency and extent of frost damage in oak populations across France, driven by the earlier advancement of the last spring frost compared to budburst under climate change. Notably, the trends for the frequency and extent of late spring frost damage were inconsistent (Chapter III). Beyond leaf phenology, I calibrated and validated a wood phenology model for the cessation of xylem cell enlargement (cE, flagging the cessation of radial stem growth) using the GLOBOXYLO database, which documents the occurrence of wood formation phenological stages (Chapter IV). This study focused on three Northern Hemisphere conifer species, namely Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies Karst) and black spruce (Picea mariana Mill.), including 718 observations of cE across 130 site-years. The model performed well for all species, with a root mean square error of 9.2 ± 1.3 days. The results indicate that both temperature and photoperiod play crucial roles in the cessation of stem growth for Norway spruce and black spruce. However, for Scots pine, only temperature appears to have a significant influence. Additionally, ontogenetic factors, such as the number of radial cells, were also found to influence the cessation of stem growth for all conifer species (Chapter IV). Furthermore, I integrated the wood phenology model, including the chilling-influenced heat sum model for the beginning of wood formation (Delpierre et al., 2019) and the cessation of wood phenology model developed in Chapter IV, into CASTANEA, a mechanistic forest stand model. The results demonstrate significant differences in wood growth predictions depending on the definition of the wood growth period. This underscores the importance of incorporating wood phenology models in terrestrial ecosystem models to obtain reliable estimates of wood growth duration (Chapter V)

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Kanoti, Keith-George. « Factors Influencing the Germination, Emergence, and Early Survival of Boreal, Temperate and Exotic Acadian Forest Tree Species in Central Maine ». Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/KanotiKG2005.pdf.

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Kalela-Brundin, Maarit. « Climate information from tree rings / ». Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5641-X.pdf.

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Morén, Ann-Sofie. « Carbon dioxide and water exchange in a boreal forest in relation to weather and season / ». Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5620-7.pdf.

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Wallace, Richard Paul, et n/a. « Effects of trees on temperate native pasture productivity ». University of Canberra. Applied Science, 1999. http://erl.canberra.edu.au./public/adt-AUC20061113.160245.

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The goal of this work was to quantify the effects of eucalypt woodland blocks on the productivity of native pastures. This research was conducted on the Southern Tablelands of New South Wales. Tree planting or retention is seen by many as an important tool in addressing the problems of soil degradation resulting from clearing and pasture improvement that threaten the sustainability of pasture systems. In particular these are dry land salinity and erosion, both of which affect large areas of agricultural lands in the south east of Australia. Whilst native tree cover remains over substantial portions of Australian pasture lands, mainly on steeper slopes and poorer soils, little has been done to measure the effects of trees on pasture productivity and soil fertility on the Southern Tablelands. Previous studies in other areas have shown a range of effects�from facilitation to inhibition�of pasture growth in the presence of trees. Soil fertility beneath trees has been shown by a number of workers to be elevated in comparison with situations in the open. Given that the range of effects may be highly site dependent, application of results from one area to another may not be valid. Thus it is necessary to measure tree effects on a regional scale if results are to be reliable. Pasture productivity was assessed over a two year period on four sites in the vicinity of Bungendore, New South Wales. A pair of plots was selected on each site, one plot in a block of eucalypt woodland, and the other nearby in an exposed, open situation. Plots were chosen to be as similar to each other as possible with the exception of tree cover. Treed plots had a tree basal area of between 10 and 20 m2 ha-1 and plots had an area of 900 m2. Two of the sites were on granitic soils and had a tree cover consisting predominantly of Eucalyptus pauciflora. The remaining two sites were on soil derived from sedimentary rocks with tree cover consisting mainly of E. mannifera, E. dives and E. melliodora. Perennial native pasture species present were similar across all sites, although their relative contributions to standing biomass varied between sites. As the plots were grazed during the period of measurement, productivity and offtake were measured seasonally using exclosure cages on each plot. Pasture standing biomass was assessed using the comparative yield technique. Microclimate was monitored in each plot by automatic weather stations. Soil moisture to a depth of 45 cm was measured by time domain reflectometry using permanent probes in each plot. Ten additional survey plots on each site, covering the range of tree basal area from 0 - 30 m2 ha-1, were assessed each season in the second year for standing biomass, soil fertility and pasture quality; expressed by nitrogen content and dry matter digestibility. Pasture floristics were measured using the dry-weight-rank method. These additional plots were chosen to be as representative of the paddocks as possible. Over the two years that productivity was measured, it was found to be higher under trees than in the open. This was predominantly due to higher winter and spring growth within treed plots. Grazing offtake was also found to be higher under trees, partly accounting for lower standing biomass found in the treed plots. Wind run, evapotranspiration and photosynthetically active radiation were all reduced by the presence of trees. Beneficial effects of shelter from winds may largely explain the higher productivity observed in the treed plots, and could outweigh negative effects of below ground competition and radiation interception by tree canopies at low to moderate tree densities. Soil moisture was not affected by the presence of trees. Soil fertility also did not differ between treed and open plots nor was there any difference in pasture nitrogen content or dry matter digestibility. On the sites where soils were derived from sedimentary rocks, pasture floristics were found to be related to tree basal area. Themeda ausfralis biomass was negatively related to tree basal area, and was partially replaced by large tussock species such as Poa sieberiana and Chionochloa pallida. A reduction of pasture quality resulted, particularly as the latter species is not grazed to any significant extent. Given the desirability of having deep rooted perennial components in grazing lands, the results of this study indicate that it may be possible to utilise trees to assist in preventing or reducing a range of adverse environmental consequences arising from agricultural activities, without unduly compromising pasture productivity. Additionally, the wide range of environmental conditions provided by a mix of treed and open pasture promotes a higher degree of heterogeneity of the herbaceous layer. This may assist in maintaining productivity over a greater range of climatic conditions than would be the case with a more homogeneous pasture.

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Cheng, Song. « Influence of soil temperature on ecophysiological traits of four boreal tree species ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ52716.pdf.

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Spake, Rebecca. « Evaluation of strategies for conserving biodiversity in temperate and boreal forests ». Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/390658/.

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Halting biodiversity loss and the associated decline of ecosystem functioning is one of the greatest challenges faced by mankind. The globally adopted Aichi Biodiversity Targets for 2011-2020, issuing from the 10th Conference of the Parties of the Convention on Biological Diversity, represent the strongest global commitment to this challenge. For forest ecosystems, biodiversity decline can be halted only with i) sustainable management of multifunctional production forests (Target 7), ii) formation of well-connected systems of protected areas (Target 11), and iii) forest restoration (Target 15). Reaching these targets for the world’s forests requires a sound empirical understanding of the functioning and the relative importance of forests under different management regimes. Indeed, environmental policy should be informed by robust scientific evidence. This thesis addresses knowledge gaps that exist in the evidence-base for sustainable forest management and conservation in temperate and boreal forests. Chapter 2 quantifies the recovery rates of different functional groups of beetles, lichens and fungi to forest restoration measures in temperate and boreal regions across the world. A systematic review and meta-analysis identifies functional-group-specific relationships in the response of species richness to stand age after forest disturbance, with some groups requiring around a century of stand continuity for recovery to old-growth levels. The slow recovery of these functional groups makes old-growth forest an effectively irreplaceable biodiversity resource that should be exempted from restoration offset initiatives. Chapter 3 compares the biodiversity value of overmature even-aged planted and old-growth forest stands for ectomycorrhizal fungi in the New Forest National Park, UK. Overmature plantations are those beyond economic maturity, acquiring some of the structural characteristics of old-growth forests and there is increasing interest in their setting aside as a means of preserving species associated with old-growth forests. Analysis of 3 years of field data shows that setting aside of overmature planted forest is an effective means of conserving ectomycorrhizal communities associated with old-growth forests, given temporal continuity in the order of a century. This holds out particular promise for historically deforested regions such as the UK, where little old-growth forest remains and much planted forest exceeds a century in age. Chapter 4 investigates the relative importance of abiotic and biotic drivers of carabid functional trait diversity and composition for coniferous production forests across the UK. Analysis of the dataset of the UK Forestry Commission’s Biodiversity Assessment Project (BAP 1995-1999) contradicts previous studies in showing that ground vegetation diversity is not an important determinant of carabid functional diversity. This result suggests that restoration of plant communities, a major goal of forest restoration efforts, will not necessarily enhance carabid diversity in coniferous plantations. Canopy cover was the most important variable, tending to drive down carabid diversity. Chapter 5 collates an evidence base that will inform forest biodiversity conservation and policy-making in Japan. Four management interventions, outlined in Japan’s National Biodiversity Strategy, are assessed by systematic review and meta-analysis for their impacts on species richness, abundance and composition. The work provides general guidance for forest biodiversity conservation in Japan, and it highlights a major knowledge gap in a widely used contemporary intervention known as ‘satoyama’.

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Vallin, Simon. « Likelihood-based classification of single trees in hemi-boreal forests ». Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-99691.

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Determining species of individual trees is important for forest management. In this thesis we investigate if it is possible to discriminate between Norway spruce, Scots pine and deciduous trees from airborne laser scanning data by using unique probability density functions estimated for each specie. We estimate the probability density functions in three different ways: by fitting a beta distribution, histogram density estimation and kernel density estimation. All these methods classifies single laser returns (and not segments of laser returns). The resulting classification is compared with a reference method based on features extracted from airborne laser scanning data.We measure how well a method performs by using the overall accuracy, that is the proportion of correctly predicted trees. The highest overall accuracy obtained by the methods we developed in this thesis is obtained by using histogram-density estimation where an overall accuracy of 83.4 percent is achieved. This result can be compared with the best result from the reference method that produced an overall accuracy of 84.1 percent. The fact that we achieve a high level of correctly classified trees indicates that it is possible to use these types of methods for identification of tree species.
Att kunna artbestämma enskilda träd är viktigt inom skogsbruket. I denna uppsats undersöker vi om det är möjligt att skilja mellan gran, tall och lövträd med data från en flygburen laserskanner genom att skatta en unik täthetsfunktion för varje trädslag. Täthetsfunktionerna skattas på tre olika sätt: genom att anpassa en beta-fördelning, skatta täthetsfunktionen med histogram samt skatta täthetsfunktionen med en kernel täthetsskattning. Alla dessa metoder klassificerar varje enskild laserretur (och inte segment av laserreturer). Resultaten från vår klassificering jämförs sedan med en referensmetod som bygger på särdrag från laserskanner data. Vi mäter hur väl metoderna presterar genom att jämföra den totala precisionen, vilket är andelen korrektklassificerade träd. Den högsta totala precisionen för de framtagna metoderna i denna uppsats erhölls med metoden som bygger på täthetsskattning med histogram. Precisionen för denna metod var 83,4 procent rättklassicerade träd. Detta kan jämföras med en rättklassificering på 84,1 procent vilket är det bästa resultatet för referensmetoderna. Att vi erhåller en så pass hög grad av rättklassificerade träd tyder på att de metoder som vi använder oss av är användbara för trädslagsklassificering.

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Henry, Hugh Allen Lorenzo. « The relationship between shade tolerance and shade avoidance in temperate trees ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31215.pdf.

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Takahashi, Sayaka. « Relationship between vessel formation and leaf phenology in temperate broad-leaved trees ». Kyoto University, 2015. http://hdl.handle.net/2433/199351.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第19027号
農博第2105号
新制||農||1030(附属図書館)
学位論文||H27||N4909(農学部図書室)
31978
京都大学大学院農学研究科森林科学専攻
(主査)教授大澤晃, 教授髙部圭司, 教授北島薫
学位規則第4条第1項該当

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Toba, T., et T. Ohta. « An observational study of the factors that influence interception loss in boreal and temperate forests ». Elsevier, 2005. http://hdl.handle.net/2237/6939.

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Charron, Isabelle. « Sexual recruitment of trees following fire in the southern mixedwood boreal forest of Canada ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ39456.pdf.

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Bergqvist, Göran. « Stand and wood properties of boreal Norway spruce growing under birch shelter / ». Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5642-8.pdf.

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Fernández, Collao Eduardo [Verfasser]. « Dormancy in temperate fruit trees - Perspectives for farming in a changing climate / Eduardo Fernández Collao ». Bonn : Universitäts- und Landesbibliothek Bonn, 2021. http://d-nb.info/1238687547/34.

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Bartlett, Paul Alexander. « Modelling with CLASS, representing surface-atmosphere interaction in temperate and boreal forests using the Canadian Land Surface Scheme ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2002. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ65664.pdf.

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Anyomi, Kenneth Agbesi. « Spatial and temporal complexities in forest productivity-climate relationships within northern temperate and boreal forests of eastern Canada ». Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30206/30206.pdf.

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La productivité est influencée par des facteurs climatiques et non-climatiques temporaires ou permanents. Leurs effets varient dans le temps et dans l’espace et le fait d’assumer une sensibilité homogène de la productivité alors qu’elle est en fait hétérogène a des conséquences sur la capacité de prévision de la productivité forestière. Il existe des preuves des changements globaux, régionaux et locaux et la réponse en terme de croissance à ces variations dans la forêt boréale est diversifiée et dans certains cas contrastées. Il est donc nécessaire de surveiller constamment la croissance et la productivité et des études régionales sont donc nécessaires pour étudier les alternatives des procédures d'estimation de la productivité. Cette thèse a donc pour but de déterminer dans quelle mesure les changements dans le climat et les régimes de perturbations affecter la productivité du site dans les forêts boréales et tempérées septentrionales situées dans la province de Québec. Des données d’analyse de tiges ont été obtenues pour 32 peuplements dominés par le tremble dans un transect nord-sud couvrant 5 degrés de latitude, représentant un large gradient climatique avec différent dépôts du surface. La croissance en hauteur en temps réel y a été étudiée à l’aide du modèle de productivité de Plonski. Plus de 4000 placettes échantillons temporaires ont été obtenues dans des peuplements d'âges, de structures et de compositions différentes pour mesurer les effets rétroactifs de la végétation sur la productivité, qui résultent indirectement du climat et du sol. Le modèle de Pothier et Savard a ensuite été utilisé pour estimer l'indice de qualité de station du tremble dans des peuplements mélangés. Enfin, le dernier chapitre a utilisé le modèle aspécifique hauteur dominante-âge de Pothier et Auger. Les résultats du premier chapitre montrent que, dans les peuplements dominés par le tremble, la croissance en hauteur est surtout influencée par la somme annuelle des degrés-jours, avec un pouvoir prévisionnel aussi bon que celui obtenu avec des variables basées sur les processus. Un modèle qui suppose que certaines populations ont des réponses différentes au climat est meilleur, ce qui démontre que la sensibilité du tremble au climat n'est pas identique sur toute son aire de dispersion. Dans les peuplements mélangés, la structure du peuplement et la composition en espèces sont les principaux facteurs expliquant la productivité du tremble. Une interaction entre les facteurs du paysage et de la placette influence la productivité à l’échelle des placettes, suggérant qu'une approche de modélisation hiérarchique est plus appropriée. Enfin, puisque les changements de structure et de composition reflètent la dynamique de succession, il est déduit que les changements successionnels dominent la variabilité de la productivité dans les peuplements mélangés. Nos résultats semblent concorder avec l’idée fondamentale de l’existence d’une hétérogénéité (dans la productivité forestière) due aux interactions intra- et inter-specifiques qui produisent des structures capables de s’adapter dans le temps, comme le suggère le concept des systèmes adaptatifs complexes.
Forest productivity is driven by direct climatic and non-climatic factors which are transient or permanent in nature. Their effects vary through time and along spatial scales, thus assuming equal sensitivities across time and space where heterogeneous growth responses exist has consequences for the prediction of forest productivity. There is growing evidence of global changes, associated by rather diverse and in some cases contrasting changes in growth. It is necessary to constantly monitor growth and productivity and regional studies are therefore necessary to consider alternative productivity estimation procedures. This thesis was therefore aimed at determining to what extent global, regional and local changes in climate and disturbance regimes affect forest site productivity within eastern Canadian boreal and northern temperate forests located within the province of Québec. Stem analysis data was first obtained from 32 aspen dominated stands that spanned a 5-degree of latitude-wide transect representing a large climate gradient with different surficial deposit types in order to study real-time height growth. Plonki’s site index model calibrated from stem analysis data was used in estimating a height growth index for these 32 stands. Over 4000 temporary sample plots were also obtained from stands of varying age, structure and species compositional gradients in order to determine feedback effects of vegetation on productivity, which are indirect effects of climate and soil. A site index model calibrated from temporary sample plots (and currently used in Québec for growth and yield estimation) was used in estimating site index for mixed aspen stands. Finally, the last chapter of this thesis used an aspecific height-age relationship. Results of the first chapter show that within aspen dominated stands, height growth is mainly driven by the annual cumulative sum of growing degree days with an explanatory capacity as good as that of more complex processed-based variables. Also, aspen productivity in pure stands is better explained with a model that assumes that specific populations have different response functions to climate, demonstrating that climate sensitivity is not stable across a species’ geographic range. Within mixed species stands, stand structure and species composition are the major drivers of aspen productivity. Variability in productivity is better explained at the level of landscapes than stand-level. An interaction between landscape- and stand-level drivers influence stand-level productivity, suggesting that a hierarchical modelling approach is more appropriate than a single-level model. Since stand structural and compositional changes are dynamics that characterize stand succession, it is inferred that successional changes and not climate drive productivity in mixed stands, when measured with site index. Our results seem to concur with the fundamental idea of the existence of heterogeneity (in forest productivity) due to intra- and inter-specific interactions in a way that produces structures capable of adapting through time, as suggested by the concept of complex adaptive systems.

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Brown, Susann Melissa. « Nitrogen mineralization in boreal forest stands of northwestern Quebec ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0022/MQ29664.pdf.

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Cunningham, Shaun Cameron 1971. « Comparative ecophysiology of temperate and tropical rainforest canopy trees of Australia in relation to climate variables ». Monash University, Dept. of Biological Sciences, 2001. http://arrow.monash.edu.au/hdl/1959.1/9040.

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Bryant, Kelsey N. « Determining and Comparing Hydraulic Behavior among Trees with Differing Wood Types in a Temperate Deciduous Forest ». Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1617026904705736.

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Thurner, Martin [Verfasser], Christiane [Gutachter] Schmullius, Christian [Gutachter] Beer et Dieter [Gutachter] Gerten. « Carbon stock and carbon turnover of boreal and temperate forests / Martin Thurner ; Gutachter : Christiane Schmullius, Christian Beer, Dieter Gerten ». Jena : Friedrich-Schiller-Universität Jena, 2017. http://d-nb.info/1177600072/34.

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van, Woerkom Anne. « Cryptic refugia vs. Tabula Rasa : Boreal trees in glacial Fennoscandia : Plant growth during the Weichselian glaciation and the early Holocene in northern Europe ». Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-114505.

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Recent studies applying innovative technologies, such as genetic analysis and carbon dating, contradict the palynological based assumption that Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) vanished from Fennoscandia during the Last Glacial Maximum (c. 20.000 yrs BP) and re-colonized after the cold Younger Dryas (c. 12.000 yrs BP). Instead, those studies indicate glacial survival of boreal trees in ‘cryptic’ refugia within Scandinavia, which is still heavily debated. In this report, I try to get a better grip on the discussion if Norway spruce and Scots pine survived Weichselian glacial periods in isolated ‘cryptic’ refugia within Scandinavia, or either re-colonized Fennoscandia by post-glacial migration from eastern areas such as Russia. To this aim, climatic settings are described and an overview is given on what is already known on the distribution of boreal trees during the Weichselian glaciations and the post-glacial landscape. Several records are important to detect ancient boreal trees: pollen, macrofossils and currently DNA. Macrofossils indicate early post-glacial tree growth in the central Scandes just after the Younger Dryas, aDNA indicates the existence of a ‘cryptic’ refugium on Andøya during the Last Glacial Maximum and modern DNA analysis possibly indicates isolation of spruce in western Norway, which are all contradicted by the current interpretation of low pollen percentages. Altogether, alternative hypotheses supporting glacial survival of plants might have been overlooked and pollen interpretations need revision, which could turn the exclusion from the past into supporting evidence for the glacial survival of P. abies and P. sylvestris in Scandinavia.

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Doner, Nicholas R. « Effects of drought on the growth of young and mature temperate forests in West Virginia ». Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=53.

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Thesis (M.A.)--West Virginia University, 2004.
Title from document title page. Document formatted into pages; contains viii, 82 p. : ill. (some col.), maps. Vita. Includes abstract. Includes bibliographical references (p. 45-48).

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Angstmann, Julia L. « Spatial and temporal variability of tree transpiration and its drivers along a soil drainage gradient in the boreal black spruce forest ». Laramie, Wyo. : University of Wyoming, 2009. http://proquest.umi.com/pqdweb?did=1990985251&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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Messier, Julie. « Variation and Integration of Ecophysiological Traits across Scales in Tropical and Temperate Trees : Patterns, Drivers and Consequences ». Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/594556.

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The overarching goal of my dissertation is to explore the potential and limits of a trait-based approach to plant ecology. Together, the different studies presented here address two explicit and implicit foundational assumptions underpinning the trait-based approach: (1) that the correlation patterns and biological significance of traits transfer across scales and (2) that the phenotypic complexity of plants can accurately be synthesized into a few meaningful traits to study their ecology. Moreover, the last chapter focuses on a third key assumption: (3) that traits are strong predictors of plant performance (Shipley et al. In Press). I examine these assumptions by exploring multivariate patterns of phenotypic variation and integration across different ecological scales (e.g., individuals, populations, species) while explicitly considering the phenotypic complexity of trees, both in terms of their multidimensional and integrated nature. Two themes thus permeate this body of work: scales and phenotypic complexity. Much of what we know about the relationships among key traits comes from species-scale studies. Trait variation at smaller scales are often interpreted in the context of these interspecific relationships, but it is not clear that interspecific patterns observed at global scales apply to smaller scales. Moreover, although plants are complex, integrated organisms with intricate relationships among their traits, single traits are often studied and interpreted without considering the rest of the phenotype. Yet, examining individual traits outside of their phenotypic context might provide limited insight or be misleading. To address these shortcomings, this body of work examines multidimensional patterns of trait variation and correlation across ecological scales. It uses (1) a set of six ecophysiological leaf traits from mature trees in a lowland tropical rainforest, and (2) a set of twenty leaf, root, stem, branch and whole-plant ecophysiological traits from deciduous saplings in a temperate forest. The combination of our findings point to three main conclusions: (i) local interspecific and intra-population trait integration structures differ from each other and from the global interspecific patterns reported in the literature, such that global-scale interspecific patterns cannot readily be transferred to more local scales; (ii) considering the complexity of the plant phenotype provides better insights into ecological patterns and processes than what we can learn from considering individual or a handful of traits; and (iii) traits strongly affect individual plant performance, although there is no relationship between a species' trait correlation structure and its environmental niche, which suggests that there are multiple alternative optimal phenotypes in a given environment.

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Kaltenrieder, Petra. « Long-term vegetation dynamics, fire disturbance and their driving factors in the boreal and temperate biomes : evidences from palaeoecological approaches / ». Bern : [s.n.], 2008. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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Holgén, Per. « Seedling performance, shelter tree increment and recreation values in boreal shelterwood stands / ». Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5854-4.pdf.

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Dearden, Fiona M. « Decomposition and microbial activity in natural temperate and boreal forests : the influence of microsite, proximity to woody debris and interception by ferns ». Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486461.

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There is a growing but inconclusive body of work on effects of litter-mixing on ecological processes, but few have considered interactions among foliar and woody litters. Further, most work on litter decomposition assumes that litterfall reaches the ground, and the effects of interception of litter (e.g. by ferns or logs) remains largely unexplored. Three studies were perfonned to investigate these issues. The first study was in a long-tenn chronosequence in the Swedish boreal forest where decomposition' rate declined with ecosystem retrogression. Field measurements showed that the ratio of twig to foliage in litterfall increased with prolonged absence ofdisturbance. In a mesocosm experiment, combining foliar and twig litters in their natural proportions reduced overall decomposition rates, suggesting that the increased twig proportion may contribute to the large increase in humus build-up found with prolonged absence of disturbance. The second study was in a New Zealand temperate rainforest, and showed that logs fonned an important microsite for decomposition, with strongly contrasting microbial activity and organic matter content compared with ~e ground. Microbial activity on logs was variable, probably linked to differences in phenolics and decay stage. The third study, also in a New Zealand temperate rainforest, showed that the fern Blechnum discolor has the potential to intercept and retain 10% of falling litter. A higher twig to foliage ratio was found in the litter accumulated in fern crowns than in the incoming litterfall or on the forest floor. Organic matter content, basal respiration and microbial activity were significantly higher in fein crowns than on the forest floor. Further, foliar litter decomposed significantly faster in fern crowns than away from the crown, but not faster than at the trunk base. Consequently, litter interception by ferns may affect nutrient cycling through concentrating nutrients and organic matter in and under ferns.

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DeGomez, Tom. « Training and Pruning Newly Planted Decidous Fruit Trees ». College of Agriculture, University of Arizona (Tucson, AZ), 2015. http://hdl.handle.net/10150/559564.

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6 pp.
Training and pruning newly-planted deciduous fruit trees is one of the most important steps in developing trees with a strong framework (scaffold branches). Trees with a good framework of branches can support heavy crops without limb breakage and will help to bring the young tree into production at an early age. Selection and arrangement of these branches determines the type of development and growth in later years. The goal of pruning and training is to balance vegetative and fruiting wood growth.

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Lance, Andrew C. « SOIL MICROBIOTA AND ECOLOGICAL RESTORATION:CONNECTIONS AND IMPLICATIONS FOR PRACTICE ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1584098163050123.

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Müller, Sandra [Verfasser], et Michael [Akademischer Betreuer] Scherer-Lorenzen. « Architectural light foraging syndromes of juvenile temperate broad leaved trees = Einfluss von Architekturmerkmalen auf die Raumeroberung von Laubbäumen im Jugendstadium ». Freiburg : Universität, 2014. http://d-nb.info/1123481059/34.

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Rudolphi, Jörgen. « Bryophytes, lichens and dead wood in young managed boreal forests / ». Uppsala : Dept. of Ecology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200788.pdf.

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Bhattacharyya, Amalava, Valmore C. Jr LaMarche et Malcolm K. Hughes. « Tree-Ring Chronologies from Nepal ». Tree-Ring Society, 1992. http://hdl.handle.net/10150/262376.

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Ten ring-width based chronologies from Nepal are described and the prospects for further dendroclimatic work there reviewed briefly. The initial results are encouraging, and more intensive subregional sampling is called for. All the cores examined showed distinct annual rings, and there was little evidence of double or missing rings, except juniper at some sites and in some Pinus roxburghii trees. Difficulty was encountered in dating Pinus wallichiana and Cupressus dumosa. Individual site chronologies of Cedros deodora, P. roxburghii and P. wallichiana were particularly promising, and of high elevation Abies spectabilis moderately so. Densitometric data are likely to be more useful for this species. The paucity of meteorological data in Nepal represents an obstacle to further dendroclimatic work there.

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Johansson, Therese. « The conservation of saproxylic beetles in boreal forest : importance of forest management and dead wood characteristics / ». Umeå : Dept. of Animal Ecology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200666.pdf.

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Hellberg, Erik. « Historical variability of deciduous trees and deciduous forests in northern Sweden : effects of forest fires, land-use and climate / ». Umeå : Dept. of Forest Vegetation Ecology, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/s308.pdf.

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Tigabu, Mulualem. « Characterization of forest tree seed quality with near infrared spectroscopy and multivariate analysis / ». Umeå : Dept. of Silviculture, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s274.pdf.

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Nygren, Cajsa. « Functional diversity in nutrient acquisition by ectomycorrhizal fungi / ». Uppsala : Dept. of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/200854.pdf.

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Rindzevičius, Vytautas. « Short-term effects of controlled conservation burning ». Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-234965.

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In this study, the immediate and short term (three months) effects of conservation burning have been investigated in coniferous forests in southeastern Sweden. Five tree species were investigated Picea abies (Norway spruce), Pinus sylvestris (Scots pine), Populus tremula (aspen), Betula pendula (silver birch) and Betula pubescens (downy birch), as well as ground vegetation of mosses, dwarf shrubs and ground lichens. Burning increased the proportion of live deciduous tree shoots from 51 % to 81 % and the live tree shoot size distribution of four tree species was significantly changed by fire. Fire affected the tree species differently. Three months after burning deciduous tree species exhibited strong sprouting, while P. sylvestris had established many seedlings, significantly increasing its share of the tree stand. P. abies lacked any visible positive response to burning and its number of live shoots decreased by 83 %. Mineral soil was exposed on only the moss vegetation and covered just 4 % of the studied plot area. The initial vegetation response to fire was negative, but significant dwarf shrub recovery was detected three months after burning.

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Dehlin, Helena. « Ecosystem functioning and plant-soil interactions in forests : influences of quality and diversity of resources / ». Umeå : Dept. of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200679.pdf.

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McDonald, Hannah Beth. « Tree Growth and Spatial Pattern in Two Forest Park Permanent Plots : A Look at Stand Composition and Condition ». PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/313.

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In June of 2010, two permanent research plots were established in Forest Park, based on their differing proximities to downtown Portland, Oregon. As part of a long-term ecological research project that seeks to explore the ecological status and human thumbprint on this 5,100 acre forested reserve, the 2010 tree data was investigated for emergent compositional and spatial patterns. Stand composition, tree size, growth rates, and spatial patterns were analyzed, along with ecological and land use histories. Results indicate that the Balch plot, more closely located to the urban center, has different stand composition, condition, and vegetation growth rates, compared to the more rural Miller site. This study supports findings from a study done by Broshot in 2009, where more urban plots demonstrate a different stand composition and recruitment pattern than rural sites. The study is an initial step for exploring questions regarding the ecological status of Forest Park and how land use and disturbance, past and present, shape Portland's forested reserve.

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Dillaway, Dylan N. « Thermal acclimation of leaf metabolism and its consequences for plant carbon balance : a comparison of boreal and temperate tree species along a latitudinal transect / ». 2009. http://www.library.wisc.edu/databases/connect/dissertations.html.

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Abdul, Bahar Nur Hazwani. « Photosynthetic characterisation of tropical and temperate rainforest species ». Phd thesis, 2016. http://hdl.handle.net/1885/117236.

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Rubisco catalyses a rate-limiting step in photosynthesis and is the largest nitrogen sink in leaves. The maximum rate of carboxylation of Rubisco, Vcmax, is routinely estimated from gas exchange using the Farquhar, von Caemmerer & Berry 1980 model of photosynthesis. As Vcmax allows mechanistic representation of photosynthesis, it has been incorporated into terrestrial biosphere models to estimate global primary productivity. However, doubts remain about previous estimates of Vcmax for globally important biomes, such as moist forests, both in tropical and temperate regions. In my thesis, I present a survey of Vcmax values – calculated assuming infinite mesophyll conductance - along a 3,300-meter elevation gradient from lowland western Amazon to the Andean tree line in Peru; this region is home to the largest moist forest on Earth. Large variations in Vcmax were found within and across the 18 field sites. As hypothesised, when estimated at a common measuring temperature (25°C), average Vcmax values of lowland Amazon trees were significantly lower than that of Andean trees. When data for the lowland Amazon and upland Andean trees were combined, the resultant mean tropical Vcmax value was lower than that of temperate trees reported in past studies. My analysis points to low Vcmax of Peruvian tropical trees being linked to limitations in phosphorus supply, and to a high proportion of Rubisco being inactive. The second part of my thesis investigated how mesophyll conductance influences the estimation of Vcmax for several Australian tropical (i.e. warm-adapted) and temperate (i.e. cool-adapted) moist-forest trees. Consistent with previous glasshouse studies, the selected tropical tree species exhibited significantly lower Vcmax values than their temperate counterparts. Importantly, I showed, for the first time, that the Vcmax estimated on the basis of intercellular CO2 partial pressure was equivalent to that on the basis of chloroplastic CO2 partial pressure, when using appropriate Michaelis-Menten constants for CO2 and O2. Thus, low mesophyll conductance in tropical moist forest is unlikely to account for the low estimates of Vcmax found in the Peruvian field work study. Finally, mechanisms underpinning development of photosynthesis in tropical moist forest trees, which include ontogenetic changes in leaf anatomy, and mesophyll and stomatal conductances, were examined. Key components of photosynthesis such as Vcmax, maximum electron transport rate and chlorophyll content increased synchronously during expansion, accompanied by development of leaf internal structures such as intercellular air spaces and mesophyll cells. The balance between photosynthetic carbon uptake and respiratory release changed dramatically during leaf development, reflecting a two-fold decline in area-based rates of respiration in expanding leaves as photosynthesis became fully functional. The dataset presented in my PhD thesis adds to the growing number of empirical estimates highly needed by the photosynthetic modelling communities, and validates the accuracy of Vcmax estimation using biochemical approaches. Collectively, my study is expected to contribute towards better understanding and representation of Vcmax in tropical forests.

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Patterson, Angelica Eloisa. « Seeing the Forest for the Trees : The Physiological Responses of Temperate Trees in a Warmer World ». Thesis, 2021. https://doi.org/10.7916/d8-c1cx-8e45.

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A forest’s ability to sequester carbon dioxide depends on factors such as periodic disturbance regimes, land-use change, the composition and productivity of the vegetative community, and the location and age of forested stands. However, one of the driving forces that contributes to changes in forest carbon dynamics include climatic factors, such as changes in temperature and precipitation, as well as atmospheric CO₂ concentrations which can affect the physiology of plants in complex ways. Our theorized understanding of plant physiological response to changing environmental conditions have been based on latitudinal and altitudinal studies or greenhouse experiments that measure plant physiological traits on one or a handful of plant species – and as scientists work to reduce the large variability that exists behind climate projections and plant community predictions, the need to collect locational and species-specific data becomes increasingly evident. This dissertation aims to address this issue by examining the physiological responses to temperature for 23 different tree species that have historically different geographic range distributions categorized into three groups: northern, central, and southern. The ranges of all species overlap and coexist at Black Rock Forest (BRF), an eastern deciduous forest located in the Hudson Highlands of New York. Chapter 1 examines the physiology of 16 coniferous and broadleaved tree species to determine if geographic provenance has a significant effect on foliar respiration rates, response to elevated temperature, and the respiratory substrate used to fuel the respiratory process. Chapter 2 compares the photosynthetic capacities and temperature responses of 17 broadleaved tree species to determine which range group may be more tolerant of a warming climate. Appended to this dissertation is preliminary data of a growth chamber experiment, examining the plasticity of physiological traits expressed under elevated temperatures to assess whether northern red oak seedlings show potential to acclimate to projected climate conditions and regenerate with minimal physiological constraints. Collectively, the results of these studies find significant differences in photosynthetic capacities and photosynthetic and respiration responses to temperature among species and among range groups. Northern, central, and southern ranged trees show an acclimated response to carbon assimilation under current climate conditions. However, central ranged trees, which includes the northern red oak, a dominant tree species in this region of New York, may be at a physiological disadvantage, showing lower rates of photosynthetic capacities and a trending decline of carbon assimilation under elevated temperatures. Furthermore, preliminary data from a greenhouse experiment suggests that leaf morphology and physiology traits are not plastic for northern red oak seedlings, which further weakens its physiological competitiveness and regeneration potential under warming temperatures. The results presented in this study on the physiological traits and temperature responses not only allows for a more thorough understanding of the physiological tolerances of migrant and resident tree species in the New York region but provides new data that could be incorporated into carbon and species distribution models for better predictions on carbon sequestration of forests and geographic ranges of tree species.

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Patra, Lukáš. « Effect of competition on resprouting and sprout growth of temperate trees ». Master's thesis, 2017. http://www.nusl.cz/ntk/nusl-431116.

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Presented thesis is focused on competition, sprout growth and resprouting ability of temperate trees. The main aim was to analyse the effect of competition on resprouting success and sprout growth of selected trees. Calculations are based on sprout size measurements of selected resprouting trees on pre-existing TARMAG II experimental plot near Soběšice, the Czech Republic. Appropriate allometric equations were used to determine biomass of individual trees and pre- and post-harvest competition indices. Statistical analysis disclosed that pre-harvest and post-harvest competition can significantly affect sprout growth of temperate trees, but can differ among species and has variable effect onto the growth. Results also clearly showed that pre-harvest competition did not affect resprouting ability of Quercu spetraea. The results indicate that thinning of sprouts in the early stage of coppice development could support sprout growth and thus biomass production.

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Eerdekens, Gunter [Verfasser]. « Biogenic volatile organic compounds in tropical, temperate and boreal forest ecosystems / vorgelegt von Gunter Eerdekens ». 2010. http://d-nb.info/1013227026/34.

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Tor-ngern, Pantana. « Comparisons of Carbon and Water Fluxes of Pine Forests in Boreal and Temperate Climatic Zones ». Diss., 2015. http://hdl.handle.net/10161/9943.

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Quantifying carbon fluxes and pools of forest ecosystems is an active research area in global climate study, particularly in the currently and projected increasing atmospheric carbon dioxide concentration environment. Forest carbon dynamics are closely linked to the water cycle through plant stomata which are regulated by environmental conditions associated with atmospheric and soil humidity, air temperature and light. Thus, it is imperative to study both carbon and water fluxes of a forest ecosystem to be able to assess the impact of environmental changes, including those resulting from climate change, on global carbon and hydrologic cycles. However, challenges hampering such global study lie in the spatial heterogeneity of and the temporal variability of fluxes in forests around the globe. Moreover, continuous, long-term monitoring and measurements of fluxes are not feasible at global forest scale. Therefore, the need to quantify carbon and water fluxes and to identify key variables controlling them at multiple stands and time scales is growing. Such analyses will benefit the upscaling of stand-level observations to large- or global-scale modelling approaches.

I performed a series of studies investigating carbon and water fluxes in pine forests of various site characteristics, conditions and latitudinal locations. The common techniques used in these studies largely involved sap flux sensors to measure tree-level water flow which is scaled up to stand-level transpiration and a process-based model which calculates canopy light absorption and carbon assimilation constrained by the sap-flux beased canopy stomatal conductance (called Canopy Conductance Constrained Carbon Assimilation or 4C-A model). I collected and analyzed sap flux data from pine forests of two major species: Pinus taeda in temperate (36 °N) and Pinus sylvestris in boreal (64 °N) climatic zones. These forests were of different stage-related canopy leaf area and some were under treatments for elevated atmospheric CO2 concentration or fertilization.

I found that (Chapter 2) the 17-year long free-air CO2 enrichment (FACE) had little effect on canopy transpiration of a mixed forest with the dominant P. taeda and other broadleaved species as the understory in North Carolina, USA (Duke FACE). The result was due to the compensation of elevated [CO2]-induced increase of canopy leaf area for the reduction of mean canopy stomatal conductance. My next theoretical study (Chapter 3), comparing P. taeda (native at 36 °N in North Carolina), P. sylvestris (native at 64 °N in norther Sweden) and Pinus contorta (native at 58 °N in British Columbia, Canada) canopies, revealed that the interaction between crown architecture and solar elevation associated with site latitude of pine canopies affected the distribution and total amount of canopy light absorption and potentially photosynthesis such that the latitudinally prescribed needle organization of a pine canopy is optimal for light interception and survival in its native location. Then, I quantified and analyzed water fluxes in four pine forests: one composed of P. taeda in North Carolina and three containing P. sylvestris in northern Sweden (Chapter 4). The latter forests consisted of various stage-related canopy leaf area and nutrient status. Combining my estimates with other published results from forests of various types and latitudinal locations, I derived an approach to estimate daily canopy transpiration during the growing season based on a few environmental variables including atmospheric and soil humidity and canopy leaf area. Moreover, based on a water budget analysis, I discovered that the intra-annual variation of precipitation in a forest has a small effect on evapotranspiration and primarily affecting outflow; however, variation of precipitation across latitudes proportionally influences anuual evapotranspiration and outflow. Furthermore, the hydrologic analyses implied the `disequilibrium' of forest water cycling during the growing season when forests may use less and more water in dry and wet regions, respectively, than the incoming precipitation. Nevertherless, at annual timescale, most forests became in `equilibrium' by using similar proportion of incoming precipitation. Finally, (Chapter 5) I estimated and analyzed the temporal and spatial variabilities of carbon fluxes of the same four forests measured in Chapter 4 using the 4C-A computational approach and analyzed their resource-use efficiencies. I concluded that, based on my results and others as available, despite the differences in species clumping and latitudes which influence growing season length and solar elevation, the gross primary productivity can be conservatively linearly related to the canopy light absorption. However, based on previous findings from a global study, different allocation of the acquired carbon to the above- and belowground is regulated by soil nutrient status.

Overall, the findings in this dissertation offer new insights into the impacts of environmental changes on carbon and water dynamics in forests across multiple sites and temporal scales which will be useful for larger-scale analyses such as those pertaining to global climate projection.

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Quinn, Eadaoin Maria Ines. « Age-related Crown Thinning : Common but not Universal in Tropical and Temperate Forest Trees ». Thesis, 2013. http://hdl.handle.net/1807/43309.

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Gap dynamics theory proposes that forest canopy gaps provide the high light levels needed for regeneration. Little attention has been given to more gradual alternatives; however, recent studies have demonstrated declines in within-crown leaf area index with tree size in temperate forest trees. Our project builds on this previous research by assessing the prevalence of this age-related crown thinning phenomenon. We quantified crown openness for 18 dominant tree species in temperate and tropical forests (n = 1786 trees). Separate pooled groupings of tropical and temperate species showed significantly positive relationships between openness and DBH (p<0.001). Of the 9 sampled species showing positive relationships, significance (p< 0.05) was detected in 3 out of 10 tropical species and 1 out of 8 temperate species. Two temperate species showed significantly reduced canopy openness with size. These trends highlight the role that very large trees play in influencing light availability for understorey regeneration.

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Salk, Carl F. « Will the Timing of Temperate Deciduous Trees' Budburst and Leaf Senescence Keep up with a Warming Climate ? » Diss., 2011. http://hdl.handle.net/10161/3835.

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Recent changes in the timing of annual events are a sign that climate change is already impacting ecosystems. Carbon sequestration by forests increases with longer growing seasons. Biodiversity can be affected by mis-timing of events through shading interactions and frost damage. Projecting forests' ability to provide these ecosystem services in the future requires an understanding of trees' phenological responses to a new climate. I begin by proposing a first order definition of an `optimal' phenological response to warming: that the mean temperature following budburst should remain essentially constant. Analogously, the temperature preceding senescence can serve the same role.

To understand which environmental cues will drive future changes in phenology, I assimilate clues from observational and experimental literature. For budburst in woody plants, spring warmth, over-winter chilling and light drive nearly all behavior, but species' responses vary widely. Species using chilling or light as safety mechanisms against budburst during mid-winter thaws are thought to be less able to phenologically track a warming climate. However, I show that even species cued solely by spring warmth are likely to under-track temperature changes. Fall cues are more idiosyncratic, and a plant's driver of senescence is likely to vary from year to year.

Models are a tempting method to untangle species budburst cues and forecast phenology under warmer climate scenarios. I tested two models' ability to recover parameters used to simulate budburst data. The simpler model was cued only by spring warmth while the complex one modulated warmth requirements with chilling exposure. For the simple model, parameters could be recovered consistently from some, but not all, regions of parameter space. The complex model's parameters were largely unrecoverable. To understand the consequences of parameter uncertainty, I applied both models to an 18 year phenological record of 13 deciduous tree species. While a few species fell into identifiable regions of the simple model's parameter space, most did not, and projected budburst dates had wide parameter-derived uncertainty intervals. These bands were wider still under a 5°C warming scenario. Even greater uncertainty resulted from the complex model.

To better understand plants' potential for growing season extension I subjected seedlings to warmer climates in a series of open-topped chambers in sites at each end of the eastern deciduous biome. Soil and air were heated to 3 or 5°C above ambient, or left unheated. For nearly all species, warming hastened budburst and germination and delayed senescence. However, these events failed to track temperature changes, happening at warmer temperatures in hotter chambers. Individual species showed a remarkable variability of all events' dates within treatments, and even within chambers. Because phenological traits are heritable, this offers a potential for evolutionary response to climate change.

This research has shown that while individual trees extend their growing seasons under warmer temperatures, they typically under-respond to the magnitude of warming, suggesting forests' capacity for increased carbon sequestration may reach a limit. However, within populations, trees vary substantially in their phenological responses, forming a possibility for evolutionarily adaptation to changing cues.

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Zang, Christian Siegfried [Verfasser]. « Growth reaction of temperate forest trees to summer drought : a multispecies tree-ring network approach / Christian Siegfried Zang ». 2011. http://d-nb.info/1010952110/34.

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Nock, Charles Andrew. « Crown thinning in canopy trees of two temperate deciduous species : Implications for light transmission in tolerant hardwood forests ». 2006. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=450448&T=F.

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Solarik, Kevin. « Variable Retention Harvesting : Mortality of Residual Trees and Natural Regeneration of White Spruce ». Master's thesis, 2010. http://hdl.handle.net/10048/1340.

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In this thesis I examined the impacts of variable retention harvesting on residual tree mortality and natural regeneration of white spruce [Picea glauca (Moench (Voss)] in northern Alberta. The VR was done in four overstory canopy compositions (ranging from deciduous dominated to conifer dominated) and at six rates of canopy retention (2%, 10%, 20%, 50%, 75% and 100%). After 10 years there was 32.9 % mortality of aspen (Populus tremuloides Michx.) and 16.9 % mortality of spruce in the VR cuts. Mortality of individual trees was greater with low density of trees, in the conifer stands and for trees with short live crowns, which are large and trees near machine corridors. Natural regeneration of spruce was greatest with higher availability of seed trees (>30 ha-1) and on machine corridors, where stocking reached 74%. By contrast, stocking was 14% on retention strips, when seed tree density was 11 seed trees ha-1.
Forest Biology and Management

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Thèses sur le sujet « Temperate and boreal trees »

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