Document type
Academic documents
Document subtype
PhD thesis
Title
Responses of coastal dune forests to groundwater changes
Participants in the publication
Cristina Maria Nunes Antunes (Author)
CE3C
C. Máguas (Adviser)
Dep. Biologia Vegetal
CE3C
Summary
Ecosystems can be profoundly influenced by groundwater. Predicted droughts and anthropogenic groundwater use will increase the rates of water table lowering in both mediterranean and tropical regions. Spatio-temporal variations in water table depth can have a great impact on physiological fundamental processes, constraining plant performance and, ultimately, survival. In coastal dune forests, groundwater can be particularly important for ecosystem water balance and a relevant water source for vegetation. Our understanding of the impacts of groundwater changes on these ecosystems globally is still poor. Thus, the overall aim of this study was to investigate the ecophysiological responses of coastal dune forests to groundwater changes across contrasting climatic conditions. We modeled water table depth, quantified the contribution of different water sources to plant water through Bayesian isotope mixing models, and used a combination of leaf spectral reflectance and isotope data to characterize ecophysiology of the dominant woody vegetation. Their variation was evaluated under contrasting temporal water availability conditions and along spatial gradients of groundwater table depth, in two mediterranean (humid and semi-arid) and one tropical coastal dune forest (restinga). In chapter 2 we found that in semi-arid mediterranean coexisting plant functional types segregate along a wide spectrum of contrasting water-source use under extremely dry conditions, evidencing great soil water partitioning. Furthermore, we confirmed that the water-source-use behavior accompany broader strategies of drought resistance. Relevant seasonal water-use shifts towards deeper soil layers occurred across different climates, but in the tropical site we did not found differentiation among the woody species. In chapter 3 we found that under a mediterranean climate and antropogenic pressure, increasing depth to groundwater trigger water uptake adjustments towards deeper soil layers only in the dry season, but not in all plant functional types. Moreover, we observed a greater use of groundwater in semi-arid conditions. Under this climatic context, groundwater lowering negatively affects traits related to both photosynthetic capacity and plant water status, regardless plants¿ water-sources-use strategy. Species showed distinct operating physiological ranges but a common physiological sensitivity to hydrological drought. In chapter 4 we found that in restinga, under less-wet conditions, topographic variation of water table depth influenced plants¿ water-uptake depth, but not their physiological conditions. Under the studied conditions, stand density, biomass and diversity had a negligible influence on plants physiological performance. Comparatively, light availability is a major driver of photosynthetic traits¿ variations, particularly partitioning over and understory species. We have highlighted the ecophysiological responses of coastal dune woody vegetation to groundwater lowering in different climatic contexts. In these ecosystems, interactions between climatic conditions, hydrology and vegetation response capacity determined plant ecophysiological patterns. We found that while groundwater influence on water-uptake depth is globally prevalent, its contribution to overall physiological status of woody species is not. The physiological impact of increasing depth to groundwater showed to be greater with increasing aridity. Under semi-arid conditions, the combined effect of soil- and ground-water scarcity, promote physiological and water stress in the woody community. Thus, plants under this hydrological context are more susceptible to suffer from water table depletion.
Institution
UNIVERSIDADE ESTADUAL DE CAMPINAS
Publication Identifiers
Publisher
Universidade Estadual de Campinas
Document Identifiers
DOI -
https://doi.org/10.47749/t/unicamp.2018.1096460
URL -
https://doi.org/10.47749/t/unicamp.2018.1096460
Awards
Prêmio CAPES de Tese - Edição 2019