Drought resistance traits are important for deciduous woody species distribution across rainfall and disturbance gradients in caatinga

Eunyoung Jung1, Timo Conradi1, Marcelo Tabarelli2, Inara Real2, Bettina Engelbrecht1
1 Department of Plant Ecology, University of Bayreuth
2 Department of Botany, Universidade Federal de Pernambuco

O 3.4 in Tracking Spatial Patterns: From Mosquitos to Biomes

11.10.2018, 14:45-15:00, H36, NW III

Seasonally dry tropical forests are highly threatened by both rapid climate change (e.g. severe droughts) and chronic human disturbances (e.g. wood extraction and livestock grazing). A role of drought for community assembly across rainfall and chronic disturbance gradients is however poorly known for dry tropical forests. Using physiological traits hypothesized to promote species drought resistance, we tested if drought is important for shaping community assembly across rainfall and disturbance gradients. We measured three traits, i.e. turgor loss point, bark conductance, and minimum leaf conductance, from 22 deciduous woody species occurring in caatinga. Community weighted means of traits were calculated using stem density records from 19 plots distributed across rainfall and disturbance gradients. Rainfall niche of 49 deciduous woody species occurring in dry tropical forests were additionally estimated using species occurrence data available from global databases for expanding the analysis from caatinga to whole dry tropical forests. Community bark conductance and community turgor loss point showed a positive and a negative relation to annual rainfall, respectively, indicating that these are important traits for species distribution across rainfall gradients in caatinga. Species’ turgor loss point was positively related with various rainfall niches both within caatinga species and across all species, opposite to the result from the community analysis of caatinga species. This suggests that importance of drought resistance strategies (e.g. avoiding or tolerating) for species distribution across rainfall gradients may change with local conditions such as intensity of chronic disturbance and nutrient availability.    

Keywords: community weighted mean, rainfall niche, turgor loss point, bark conductance

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