Tree physiological and structural properties as response and effect traits of biotic-atmospheric interactions in natural and anthropogenic eco-systems in South Ecuador

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Subproject B2 investigates the dynamics of carbon and water relations as response and effect traits (RTs and ETs, respectively) of the two primary target objectives, evapotranspiration and biomass production at the individual plant level. These details are required for an understanding of the water and carbon fluxes measured by A1 at the plot scale, but also provide realistic parameters for the calibration of LSMBio und LSMatmo. The dynamics of the gas exchange of the leaves (WP 5, 6) as well as the integrating isotope signatures (13C, 18O, WP1) will be studied along altitudinal gradients in both the mountain rainforest (MRF, partly done) and the mountain dry forest (MDF). Corresponding measurements with crops and trees on the agroforestry plots will unveil effects of land use changes on functional RTs and ETs. ETs emerging from the leaves’ gas exchange are the daily water consumption, recorded via xylem sap flow, and carbon gain (growth), variables required for upscaling from the leaf to the plant level. Growth will be estimated from high-resolution stem diameter variations combined with delta13C and delta18O signatures of the wood. For pastures and crop fields biomass production and transpiration will be determined on a m² level. Water use efficiency (instantaneous, intrinsic) will be determined along the gradients for deeper ecophysiological insights (SH1). To adequately incorporate the leaves’ carbon and water budget in partial models of Humbol-TD, RTs and ETs of the gas exchange must be determined in vivo, however under controlled standard conditions, while for model validation diurnal gas exchange measurements under natural conditions (A1, A2) are required. Other parameters like chlorophyll and RubisCO-N-content have already been determined in phase I. The physiological (WP 5 & 6), dendroecological and anatomical studies (WP 1 – 4) will contribute to a deeper understanding of the underlying processes and their environmental margins as posed by the specific hypotheses.