Leaf traits have long been used to classify and characterise species in natural ecosystems. In addition, leaf traits provide important information about plants’ strategies for the use of resources and can be used to improve our understanding of ecosystem level processes such as nutrient cycling and carbon allocation. To explore the linkages between leaf traits and productivity, we worked in two resource-limited ecosystems (a grassland and a forest), and used leaf traits to understand how species respond to changes in available resources and their relationship to ecosystem processes. We worked in a species rich limestone-grassland located in central England, which has been subjected to long-term climatic manipulation (winter warming, summer drought and extra summer rainfall). We characterised species composition in terms of their identity, abundance and leaf structural properties (nitrogen content and leaf mass per area (LMA)) in the main treatments and the control. We found that change in species abundance was the most important factor to understand the differences in productivity (above ground biomass and total foliar nitrogen). We then measured CO2 exchange at ecosystem level, using a chamber technique, and assessed the treatments’ effect on the gross primary productivity (GPP) and ecosystem respiration (Reco). GPP and Reco were controlled by soil moisture and above ground biomass but also influenced by the conditions experienced during the growing season prior to the measuring period. Our second location was a post-disturbance chronosequence in a seasonally dry tropical forest in Costa Rica and we used leaf level gas exchange measurements to explore the role of nitrogen (N) and phosphorus (P) on the temporal-spatial variation of photosynthesis of dominant species. We found that photosynthetic efficiency was strongly linked to leaf N and P content, but that there was an important seasonal pattern on this relationship likely associated to P remobilization. Additionally we found seasonal changes in resources (water, nutrients) had a larger impact on the photosynthetic parameters than changes along the chronosequence. The two ecosystems studied for this thesis are contrasting in their physiognomy, species composition and climate, but are also characterised by species whose structural traits (high LMA and high C:N ratio) are likely to have a significant impact on the nutrient cycling processes. We learned that leaf traits provide important information about species strategies and their usage of resources and they can also aid to address questions at ecosystem level in time and space, either through simple aggregation or as emergent properties. Additionally, the traits explored are important input information to up-scale processes from leaf to the ecosystem level, a step needed to address the effect changes in resources will have on the seasonally dry tropical forest and grasslands, which represent a significant fraction of the total global carbon storage.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21971号 / 農博第2361号 / 新制||農||1071(附属図書館) / 学位論文||R1||N5222(農学部図書室) / 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 小杉 緑子 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Submitted by Ricardo Cedraz Duque Moliterno (ricardo.moliterno@uefs.br) on 2016-01-20T22:46:00Z No. of bitstreams: 1 GR?NIVEL MOTA DA COSTA (1).pdf: 2200564 bytes, checksum: 3828a984c3a6ee25ef6f2d93f10132ad (MD5) / Made available in DSpace on 2016-01-20T22:46:00Z (GMT). No. of bitstreams: 1 GR?NIVEL MOTA DA COSTA (1).pdf: 2200564 bytes, checksum: 3828a984c3a6ee25ef6f2d93f10132ad (MD5) Previous issue date: 2014-09-24 / The caatinga vegetation of northeastern Brazil mainly occurs in Pre-Cambrian-crystalline-derived soils and sedimentary-basin-derived sandy soils. Recent evidence has shown variations in the dynamics, structure and floristic composition of the caatinga, which justifies the need for studies focusing on different substrates. A floristic study of the caatinga ecoregions Depress?o Sertaneja Meridional and Raso da Catarina in the municipality of Tucano, Bahia, Brazil, is of special interest because both substrates occur in a local scale, letting the opportunity to broaden our knowledge on ecological heterogeneity within the Caatinga biome. In the current study we carried out a floristic survey of 14 sites distributed throughout the ecoregions of caatinga in Tucano. We found high species diversity in the caatingas of Tucano when compared to other areas in northeastern Brazil. A total of 451 species, 288 genera, and 82 families were collected. The most species rich families are Leguminosae and Euphorbiaceae. There occur 226 species in the sites on crystalline basement, whereas 284 species were collected in the sandy areas. The ecoregions were only 13% similar in floristic composition. We found strong differences between the ecoregions with respect to floristic composition and predominant plant habit as proxy for phytophysiognomy. Overall, our results reinforce the hypothesis of two distinct biotas that assembly the caatinga dry woodlands. / A vegeta??o de caatinga do nordeste brasileiro ocorre principalmente sobre solos derivados de rochas cristalinas pr?-cambrianas e sobre cobertura arenosa de bacias sedimentares. Evid?ncias recentes t?m demonstrado varia??es na din?mica, estrutura e composi??o flor?stica da caatinga, o que fundamenta a necessidade de estudos com enfoque nos diferentes substratos. O presente estudo flor?stico das ecorregi?es de caatinga, Depress?o Sertaneja Meridional e Raso da Catarina, no munic?pio de Tucano, Bahia, ? de especial interesse porque h? esses dois substratos em escala geogr?fica local, permitindo ampliar o conhecimento sobre a heterogeneidade do Dom?nio da Caatinga. Neste trabalho ? apresentado um invent?rio flor?stico de 14 localidades nas duas ecorregi?es de caatinga. Em conjunto, as caatingas amostradas apresentaram uma alta riqueza flor?stica em compara??o com outras ?reas no nordeste do Brasil. Foram coletadas 451 esp?cies, 288 g?neros e 82 fam?lias. A maior riqueza em esp?cies foi das Leguminosae, seguida por Euphorbiaceae. Nas localidades sobre substrato derivado do embasamento cristalino ocorreram 226 esp?cies, enquanto nas de substrato arenoso ocorreram 284 esp?cies. A propor??o de esp?cies em comum nas duas ecorregi?es foi apenas 13%. Diferen?as em composi??o flor?stica refor?am a hip?tese de duas biotas distintas associadas aos dois principais tipos de substrato, que comp?em a vegeta??o da caatinga.