L'objectif principal de ce travail est d'évaluer si l'amendement calco-magnésien de deux bassins versants acidifiés du massif vosgien (un sur grès et un sur granite) engendre des changements de la morphologie des humus, de l'abondance et de la diversité de la mésofaune, de la biomasse fongique, du stockage de carbone dans les horizons organiques 5 et 7 ans après l'amendement. Par ailleurs, nous avons effectué une étude dans des conditions contrôlées de laboratoire en utilisant des microcosmes contenant les horizons organiques du sol provenant de bassins versants acidifiés sur grès et sur granite afin d'évaluer les effets à court terme de l'amendement. Les résultats indiquent que les effets de l'amendement sont beaucoup plus marqués sur le substrat le plus acide. À court terme, sur substrat gréseux, nous observons une diminution de l'abondance de la mésofaune puis une augmentation de celle-ci 5 ans après l'amendement avant de ne montrer plus aucun effet 7 ans après l'épandage. L'effet inverse ou aucun effet n'est par contre observé sur substrat granitique. Le contenu en Ca et Mg de l'horizon OL a augmenté avec l'amendement, mais cet effet n'est également significatif que sur grès. La biomasse fongique du sol n'a pas été affectée par le chaulage, mais est significativement plus élevée sur granite que sur grès. Le chaulage a augmenté l'épaisseur de l'horizon OH sur grès alors qu'il a diminué l'épaisseur de l'horizon OL sur granite, probablement en relation avec les modifications de l'activité biologique (mésofaune ou microorganismes). Enfin, sur substrat gréseux, le stock de carbone de l'humus a augmenté du fait d'un épaississement notable de l'horizon OH avec le chaulage. / The main objective of this work is to assess the consequences of calco-magnesium liming on two acidified forested catchments in Vosges Mountain (sandstone and granite) on humus morphology, abundance and diversity of mesofauna, fungal biomass and carbon storage in organic horizons 5 and 7 years after liming. Moreover, we performed a study to verify under laboratories conditions by using microcosms filled with soil from acidified catchments lying on sandstone and granite in order to study the short-term effect of calco-magnesium liming. During the two field campaigns, we determined calcium and magnesium contents of OL horizon, pH, humus morphology, mesofauna abundance and diversity, fungal biomass, soil carbon storage of organic layers OL, OF and OH.Results indicated that calco-magnesium liming affects studied parameters in different ways according to elapsed time after liming and the geological substrate (sandstone and granite), the more acidic catchment (sandstone) showing the most remarkable reaction. Results of immediate effects of liming showed a decrease of mesofauna abundance and then gradually increasing tendencies in field campaigns after 5 years while no effect after 7 years after liming. The opposite or no effects were observed on granite substrate. Ca and Mg contents in OL horizon increased by liming but this effect were only significant on sandstone substrate. Soil fungal biomass was not affected by liming but was significantly higher on granite substrate than sandstone. Liming increased the OH horizon thickness on sandstone while decreased the OL horizon on granite, under the influence of biological activity (mesofauna vs microorganisms).

This thesis consists of one chapter accepted for publication in a book and four papers published in international journals with impact factors. All of the contributions deal with the role of wood ants in energy and nutrient fluxes in forest ecosystems. Wood ant nests are known as hot spots of carbon dioxide (CO2) production and are also thought to affect methane (CH4) flux. Stable high temperatures are maintained in ant nests even in cold environments. This study is focused on quantification of CO2 and CH4 flux in wood ant nests, contribution of ants and microbes to CO2 production, properties of nest material that affect CO2 production and the role of ants and microbes in the maintenance of nest temperature. The research was conducted in temperate and boreal forests inhabited by wood ants (Formica s. str.). Gas fluxes were measured either by an infrared gas analyser or a static chamber technique. Ants and nest materials were also incubated in a laboratory. Material properties potentially influencing CO2 flux, such as moisture, nutrient content or temperature were determined. According to the results, CH4 oxidation was lower in wood ant nests than in the surrounding forest soil suggesting that some characteristics of ant nests hinder CH4 oxidation or promote CH4 production. Wood ant nests clearly are hot...

Il est probable que les changements climatiques futurs diminuent la croissance forestière en région tempérée. Cette vulnérabilité des espèces face aux contraintes du climat peut être étudiée via les cernes des arbres. Ces derniers sont en effet des archives du carbone utilisé par les arbres pour leur croissance, en lien avec les caractéristiques spécifiques de gestion du carbone et de réponse au climat. L’objectif principal de cette thèse est de déterminer, à partir des cernes, les réponses fonctionnelles de trois essences forestières tempérées (Fagus sylvatica, Quercus petraea et Pinus sylvestris) aux variations climatiques. Pour cela, nous avons réalisé une approche expérimentale en étudiant deux proxys (ou indices climatiques) : la croissance et la composition isotopique en 13C (δ13C) des cernes, à deux échelles temporelles : interannuelle et saisonnière. A l’échelle interannuelle, sur la période 1960-2007, une étude dendrochronologique a été réalisée sur les trois essences et a été complétée par l’analyse du δ13C des cernes (en relation avec le climat). A l’échelle saisonnière, nous avons déterminé précisément, sur une année (2009), les dynamiques de croissance du cerne et les variations de δ13C intra-cerne. Nos résultats mettent en évidence une sensibilité de la croissance et du δ13C des cernes des trois essences aux sécheresses estivales. Grâce à la complémentarité des proxys et des échelles temporelles, nous avons également trouvé des réponses climatiques contrastées entre espèces. La croissance du Hêtre est la plus réactive au climat d’une année à l’autre. Cette croissance ainsi que le δ13C des cernes sont fortement sensibles aux températures de juillet, en plus des précipitations printanières et estivales. Cette réponse immédiate au climat peut être expliquée par une forte dépendance de la croissance au fonctionnement foliaire et une faible utilisation des réserves carbonées pour assurer le début de la croissance. Le Chêne présente lui des arrières-effets climatiques sur sa croissance, via une forte sensibilité aux sécheresses de l’automne précédent, contrairement aux deux autres espèces. Ce résultat est à mettre en relation avec l’utilisation importante de réserves carbonées par rapport aux assimilats pour la croissance du bois initial, cette dernière étant très rapide, comme nous l’avons observé grâce à l’analyse saisonnière de la croissance. Concernant le Pin, la croissance, parce qu’elle dure plus longtemps que celle des décidues, est influencée par les températures et les précipitations de juin jusqu'à août. Le δ13C des cernes de pins est celui qui enregistre le plus la réponse au VPD, aussi bien à l’échelle saisonnière qu'interannuelle, probablement du fait d’une forte sensibilité de la conductance stomatique à ce paramètre. Les informations fournies par les cernes permettent d’appréhender la survie des espèces face aux changements climatiques futurs et peuvent être utilisées pour comprendre le dépérissement lié à ces changements. / Climate change will probably alter the tree growth in temperate forests. The species vulnerability to climatic constraints can be studied using tree rings. The latter's are natural archives of carbon used for tree growth and are linked to species carbon transfer and response to climate. The main thesis objective was to determine the functional response of three temperate species (Fagus sylvatica, Quercus petraea et Pinus sylvestris) under climatic variations using tree rings. For this, an experimental approach was conducted using two proxies (or climatic indices): the radial growth and the carbon isotope composition in 13C (δ13C) of rings at two time scales: interannual and intra-annual (or seasonal). At interannual scale, over the period 1960-2007, a dendrological study was done for three species and was completed by analysis of ring δ13C (in relation to climate). Over one year (2009) at seasonal scale, we precisely determined the radial growth dynamics and the variations in intra-ring δ13C. Our results highlighted growth and ring δ13C sensitivities to summer droughts. Because of proxy and time-scale complementarities, we have also found contrasted climatic responses among species. The beech growth is the most year-to-year responsive to climate. This growth and ring δ13C were highly sensitive to temperature in July in addition to spring and summer precipitation. This quick response of beech growth to climate could be explained by strong growth dependence to leaf functioning and low carbon reserve use to ensure the growth beginning. Contrary to the two others species, long-term consequences of climate on oak growth were found, via a high sensitivity to previous autumnal droughts. This result could be related to the high use of carbon reserves compared to assimilates for earlywood growth, which was very quick as observed by seasonal growth analysis. Concerning pine, the growth was influenced by temperatures and precipitation from June to August because the growth lasted longer for pine than that of the deciduous species. At both seasonal and interannual scales, the ring δ13C of pine trees was the best recorder of the VPD response, probably because of strong sensitivity of stomatal conductance to VPD. The information provided by tree rings allow to anticipate the species survival under future climate change and could be used to understand the declining due to these changes.

Les chiroptères sont reconnus comme de potentiels régulateurs des populations d’insectes. Ce sont aussi les mammifères européens pour lesquels les enjeux de conservation sont les plus importants. Ils trouvent dans les forêts des habitats favorables qui sont cependant menacés par les changements climatiques et la fragmentation. Il convient donc de mieux comprendre lesrelations entre les communautés de chiroptères, leurs habitats et leurs proies en forêt. L'objectif de cette thèse est de quantifier les effets, à différentes échelles spatiales, desprincipales composantes de l’habitat forestier sur l’activité, la richesse spécifique, la diversité fonctionnelle et la composition des communautés de chiroptères européens. Les résultats reposent sur des données collectées grâce à des protocoles expérimentaux en Aquitaine et dans les six pays du réseau de placettes forestières organisé par le projet FunDivEurope. De la parcelle au continent, l'accroissement de la diversité des essences forestières, de la proportion de feuillus et du bois mort, en augmentant les ressources en proies et en gîtes, ont des effets positifs sur les communautés de chiroptères. Ces effets, non stationnaires, se renforcent vers le nord avec la rigueur du climat. Nous confirmons également que les chiroptères forestiers, par leur réponse numérique et fonctionnelle aux densités de proie, peuvent limiter la démographie d’un insecte défoliateur. Des mesures de gestion, visant le renforcement des structures-clés des habitats forestiers, sont proposées pour favoriser la conservation des communautés de chiroptères et leur capacité de régulation des insectes ravageurs. / Insectivorous bats are increasingly recognized as potential regulators of pest insect populations.They also represent the group of European mammals with the most unfavorable conservation status. Forests are key habitats for many bat species but are currently under threat from climate change and fragmentation. It is therefore urgent to better understand the relationships between the bats, their prey and their habitats in forests. Our main objective was to quantify the effects, at multiple spatial scales, of the main attributes of forest habitats on the activity, species richness, functional diversity and composition of European bat communities. They were studied using manipulative experiments in Aquitaine plantation forests and automatic recordings in the network of exploratory plots set up in six European countries by the FunDivEurope project. From the plot to the continent scale, increasing tree diversity, amount of broad leaved trees and dead wood, had positive effects on bat communities through an increase in prey and roost resources. However these effects were not stationary, being stronger at higher latitudes, probably due to lower habitat carrying capacity in relation to harsher climatic conditions. In addition we experimentally demonstrated that the numerical and functional responses of bats to prey density could result in effective regulation of pine processionary moth populations. Forest management strategies aim at enhancing key habitat structures, are eventually proposed in order to improve the conservation of bats and to increase the service of pest regulation they can provide.

Rain forest canopies are renowned for their very high biodiversity and the critical role they play in key ecological processes and their influence on global climate. Despite that New Zealand supports one of the most diverse and extensive epiphyte flora of any temperate forest system, few studies have investigated epiphyte communities and their invertebrate fauna along with factors that influence their distribution and composition. This thesis represents the first comprehensive study of entire epiphyte communities and their resident invertebrate fauna in the canopy of New Zealand’s indigenous forests. The aim of this study was to determine spatial patterns of epiphyte and invertebrate species richness, abundance and community composition in relation to abiotic variables, and in particular, the responses of these communities to elevated temperature and rainfall. This study was carried out in coastal lowland podocarp-broadleaved forests at two sites on the West Coast of the South Island of New Zealand. Samples from 120 mat-forming epiphyte assemblages located on inner canopy branches of 40 northern rata (Metrosideros robusta) trees were studied to characterise the component flora and fauna. Additionally, biomass, branch and tree characteristics and community responses to treatments designed to elevate temperature and rainfall to simulate predicted climate change were measured. This investigation revealed astonishing diversity and functional complexity of epiphyte and invertebrate life in this ecosystem. The 30.6 kg (dry weight) of epiphyte material collected contained a total of 567 species, 170 epiphyte and 397 invertebrate (excluding immature specimens and mites) species, including at least 10 species new to science and many undescribed species Epiphyte communities were found to be dominated by non-vascular plants (80 % of the total species richness), particularly liverworts and invertebrate communities were dominated with respect to abundance (~ 80 % of the total individuals) by Acari, Collembola and Hymenoptera (primarily ants) and functionally by scavengers and ants. Epiphyte and invertebrate communities were highly variable with respect to spatial patterning of species richness, abundance and composition across sites, among trees within sites and among branches within trees. Overall, a highly significant proportion, > 75 %, of the variance could be attributed to differences at the branch level, but these differences could not be explained by the environmental factors measured. There were no consistent relationships between the spatial pattern of epiphytes and invertebrates, or between vascular and non-vascular plants. However, there were significant positive correlations between epiphyte biomass and invertebrate species richness (r = 0.472; p < 0.0001) and abundance (r = -0.395; p < 0.0001), as well as non-living epiphyte biomass and scavenger species richness (r = 0.4; p < 0.0001). Microclimatic measurements taken on epiphyte mats were also highly variable with respect to temperature and relative humidity at similar physical locations within the same tree as well as across trees within sites. There was also considerable variation in the intensity and frequency of climatic extremes, although potentially harmful climatic conditions were experienced by all the epiphyte mats for which weather variables were measured. Negative correlations existed between both epiphyte and invertebrate community composition and increased temperatures expressed as cumulative degree days above 5˚C. However, variability was such that there was no direct evidence that increased temperature and rainfall treatments had an effect on invertebrate species richness, abundance or diversity. Northern rata host trees harbour an astonishingly diverse and complex canopy flora and fauna that is characterised by high spatial variability. Such variability highlights that to determine species distribution and community dynamics in canopy habitats in response to disturbance caused either by climate change or invasive species the structure of entire communities at different taxonomic and spatial scales, along with their responses to microclimatic factors, need to be studied. If such complexities are not taken into account, inappropriate interpretation may result in poor decisions concerning the conservation status, vulnerability and subsequent management of such unique ecosystems.

The latter part of the reproductive growth phase in chickpea (<i>Cicer arietinum</i> L.) often coincides with declining temperature and wet conditions in western Canada, in sharp contrast to many other growing environments. This exacerbates the indeterminate nature of the crop, leading to excessive canopy development, and subsequently resulting in delayed maturity. The objectives of this study were to: i) determine the genetic relationships of short internode, double podding and early flowering traits with earliness of crop maturity; ii) determine the genetic control of major earliness traits in chickpea; iii) assess the patterns of post-flowering dry matter accumulation and partitioning to reproductive parts as related to earliness. <p>The results showed that double podding significantly reduced the number of days taken to maturity, under the conditions where this trait was sufficiently expressed. The best double podding genotypes, i.e. those with 1535% of the podded nodes bearing double pods, were about one week earlier than their single podding counterparts and standard checks. A physiological study revealed that the double podding parental genotype 272-2 partitioned a relatively greater proportion (about 58%) of the total dry matter to pods compared to 4254% in the single podding genotypes. Double podding increased the total number of pods set, and thus the increased demand for assimilates may have precluded further production of stems and leaves, resulting in an earlier transition of reproductive growth to physiological maturity. Days to flowering was positively associated with days to maturity, and partial path analysis revealed that days to flowering contributed to days to maturity indirectly via days to first pod maturity. Days to flowering explained 32% of the variation in days to first pod maturity. However, the short internode trait had an undesirable effect, in that all the short internode segregants were too late to mature. <p>Genetic studies revealed that days to flowering was determined by two major genes plus polygenes in chickpea in the short-season temperate environment of western Canada. The two major genes control over 65% of the phenotypic variation. Also, the additive component of genetic variance was significant for days to first podding, days to first pod maturity, reproductive period, and days to maturity; which is desirable for development of superior inbred cultivars of chickpea. These key phenological traits are interrelated but could be manipulated separately in the breeding process. Additional gain in earliness of crop maturity may be achieved through combined selection for these traits.

The latter part of the reproductive growth phase in chickpea (<i>Cicer arietinum</i> L.) often coincides with declining temperature and wet conditions in western Canada, in sharp contrast to many other growing environments. This exacerbates the indeterminate nature of the crop, leading to excessive canopy development, and subsequently resulting in delayed maturity. The objectives of this study were to: i) determine the genetic relationships of short internode, double podding and early flowering traits with earliness of crop maturity; ii) determine the genetic control of major earliness traits in chickpea; iii) assess the patterns of post-flowering dry matter accumulation and partitioning to reproductive parts as related to earliness. <p>The results showed that double podding significantly reduced the number of days taken to maturity, under the conditions where this trait was sufficiently expressed. The best double podding genotypes, i.e. those with 1535% of the podded nodes bearing double pods, were about one week earlier than their single podding counterparts and standard checks. A physiological study revealed that the double podding parental genotype 272-2 partitioned a relatively greater proportion (about 58%) of the total dry matter to pods compared to 4254% in the single podding genotypes. Double podding increased the total number of pods set, and thus the increased demand for assimilates may have precluded further production of stems and leaves, resulting in an earlier transition of reproductive growth to physiological maturity. Days to flowering was positively associated with days to maturity, and partial path analysis revealed that days to flowering contributed to days to maturity indirectly via days to first pod maturity. Days to flowering explained 32% of the variation in days to first pod maturity. However, the short internode trait had an undesirable effect, in that all the short internode segregants were too late to mature. <p>Genetic studies revealed that days to flowering was determined by two major genes plus polygenes in chickpea in the short-season temperate environment of western Canada. The two major genes control over 65% of the phenotypic variation. Also, the additive component of genetic variance was significant for days to first podding, days to first pod maturity, reproductive period, and days to maturity; which is desirable for development of superior inbred cultivars of chickpea. These key phenological traits are interrelated but could be manipulated separately in the breeding process. Additional gain in earliness of crop maturity may be achieved through combined selection for these traits.

No description available.

Soil organic matter (SOM) contains about twice the amount of carbon in the atmosphere. With global changes, the potential shifts in SOM quantity and quality are a major concern. Due to its heterogeneity, SOM remains largely unknown in terms of its molecular composition and responses to climatic events. Traditional bulk soil analysis cannot depict the structural changes in SOM. This thesis applies two complementary molecular-level methods, i.e., SOM biomarker gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR) spectroscopy, to examine the origin and degradation of various SOM components in grassland and temperate forest soils, and to investigate the shifts in microbial community and SOM composition with both laboratory- and field-simulated global changes, such as frequent freeze-thaw cycles, increasing soil temperatures, elevated atmospheric CO2 levels, and nitrogen (N) deposition. This thesis has several major findings. First, as the most active component in soil, microbial communities were sensitive to substrate availability changes resulting from prolonged soil incubation, freeze-thaw-induced cell lyses, N fertilization and increased plant inputs under elevated CO2 or soil warming. Microbial community shifts have direct impacts on SOM decomposition patterns. For instance, an increased fungal community was believed to contribute to the enhanced lignin oxidation in an in situ soil warming experiment as the primary degrader of lignin in terrestrial environments. Second, contrast to the conventional belief that aromatic structure was recalcitrant and stable in SOM, ester-bond aliphatic lipids primarily originating from plant cutin and suberin were preferentially preserved in the Canadian Prairie grassland soil profiles as compared with lignin-derived phenols. Cutin- and suberin-derived compounds also demonstrated higher stability during soil incubation. With an increased litter production under elevated CO2 or global warming, an enrichment of alkyl structures that had strong contributions from leaf cuticles was observed in the Duke Forest Free Air CO2 Enrichment (FACE) and soil warming experiments, suggesting an accumulation of plant-derived recalcitrant carbon in the soil. These results have significant implications for carbon sequestration and terrestrial biogeochemistry. Overall, this thesis represents the first of its kind to employ comprehensive molecular-level techniques in the investigation of SOM structural alterations under global changes.

Soil organic matter (SOM) contains about twice the amount of carbon in the atmosphere. With global changes, the potential shifts in SOM quantity and quality are a major concern. Due to its heterogeneity, SOM remains largely unknown in terms of its molecular composition and responses to climatic events. Traditional bulk soil analysis cannot depict the structural changes in SOM. This thesis applies two complementary molecular-level methods, i.e., SOM biomarker gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR) spectroscopy, to examine the origin and degradation of various SOM components in grassland and temperate forest soils, and to investigate the shifts in microbial community and SOM composition with both laboratory- and field-simulated global changes, such as frequent freeze-thaw cycles, increasing soil temperatures, elevated atmospheric CO2 levels, and nitrogen (N) deposition. This thesis has several major findings. First, as the most active component in soil, microbial communities were sensitive to substrate availability changes resulting from prolonged soil incubation, freeze-thaw-induced cell lyses, N fertilization and increased plant inputs under elevated CO2 or soil warming. Microbial community shifts have direct impacts on SOM decomposition patterns. For instance, an increased fungal community was believed to contribute to the enhanced lignin oxidation in an in situ soil warming experiment as the primary degrader of lignin in terrestrial environments. Second, contrast to the conventional belief that aromatic structure was recalcitrant and stable in SOM, ester-bond aliphatic lipids primarily originating from plant cutin and suberin were preferentially preserved in the Canadian Prairie grassland soil profiles as compared with lignin-derived phenols. Cutin- and suberin-derived compounds also demonstrated higher stability during soil incubation. With an increased litter production under elevated CO2 or global warming, an enrichment of alkyl structures that had strong contributions from leaf cuticles was observed in the Duke Forest Free Air CO2 Enrichment (FACE) and soil warming experiments, suggesting an accumulation of plant-derived recalcitrant carbon in the soil. These results have significant implications for carbon sequestration and terrestrial biogeochemistry. Overall, this thesis represents the first of its kind to employ comprehensive molecular-level techniques in the investigation of SOM structural alterations under global changes.