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Efeitos de mudanças ambientais nas relações hídricas e de carbono de árvores de florestas nebulares

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Author(s):
Cleiton Breder Eller
Total Authors: 1
Document type: Doctoral Thesis
Press: Campinas, SP.
Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
Defense date:
Examining board members:
Rafael Silva Oliveira; Laszlo Karoly Nagy; Luiz Eduardo Oliveira e Cruz de Aragão; Lucia Rebello Dillenburg; Simone Aparecida Vieira
Advisor: Rafael Silva Oliveira
Abstract

Tropical Montane Cloud Forests (TMCF) are considered one of the most vulnerable tropical ecosystems to climate change. These ecosystems possess a high number of endemic species that can only thrive on the particular environmental conditions found in TMCF. Increases in temperature and changes in the frequency of cloud immersion events might threaten the diversity and functioning of these ecosystems. In this thesis, I investigate how environmental conditions affect carbon and water relations of TMCF trees. In chapter 1, I investigated how foliar water uptake (FWU) helps TMCF trees to maintain leaf turgor during soil drought. I conducted several experiments using apoplastic tracers, deuterium labeling and leaf immersion in water to evaluate differences in FWU among three common TMCF tree species. I also measured the effect of regular fog exposure on the leaf water potential of plants subjected to soil drought and used these data to model species¿ response to long-term drought. All the studied species were able to absorb water through their leaf cuticles and/or trichomes, although the capacity to do so differed between species. During the drought experiment, the species with higher FWU capacity maintained leaf turgor for a longer period when exposed to fog, whereas the species with lower FWU exerted tighter stomatal regulation to maintain leaf turgor. The model fitted to the experimental data suggest that without fog, species with high FWU are more likely to lose turgor during seasonal droughts. In chapter 2, I used two different dendrometer techniques to measure daily growth of TMCF trees, and investigate how the growth of trees with different functional traits responds to changes in environmental conditions. I estimated tree growth (g) directly from bark diameter changes (dDb), and also using a combination of dDb and sap velocity measurements to exclude the bark capacitance effect from dDb. I measured tree functional traits such as xylem hydraulic safety margins, stomatal regulation strategies and wood density. Both methods to estimate g showed a medium to high agreement (R2=0.46-0.81) in fast-growing trees, but poor agreement in slow growing trees. Fast growing trees were able to grow in a wider range of temperature, irradiance, soil water availability and leaf-wetting conditions than slow growing trees. However, fast growing trees had narrower xylem safety margins and less dense wood. Most trees increased g during hotter and cloudy wet season conditions. These results show that environmental conditions in TMCF often limit tree growth and promote leaf turgor loss. The TMCF trees developed different strategies to deal with these environmental restrictions. Some trees adopt hydraulically riskier strategies favoring carbon uptake even during unfavorable periods; while others are more conservative and favor hydraulic safety. Climatic changes that alter fog events might threaten particularly trees with high FWU, which depend on leaf-wetting events for the maintenance of leaf turgor and growth during droughts (AU)

FAPESP's process: 13/19555-2 - Water use and carbon balance dynamics of cloud forest woody species
Grantee:Cleiton Breder Eller
Support Opportunities: Scholarships in Brazil - Doctorate