Functional biogeography : testing new approaches based on gross primary production

Functional biogeography focuses on understanding the causes and consequences of the spatial distribution of functional traits. One of the functions that plants fulfill in ecosystems is to regulate the exchange of energy and matter through photosynthesis (i.e., Gross Primary Production, GPP). In this direction, previous studies define the maximum photosynthetic capacity (GPPmax) as an Ecosystem Functional Property (EFP). It is expected that EFPs will help to better understand how ecosystems are affected by climate change and global warming. In this dissertation, I present how to understand an ecosystem function such as GPP and an EFP as GPPmax through three main axes: Magnitude, Time and Space. Specifically, in the first axis, I focus on understanding how environmental variables limit GPPmax at a global scale. In the second axis, time, I evaluate how climatic variables affect the timing (i.e. Day of the year, DOY) when GPPmax is reached (DOYGPPmax). Finally, on the last axis, I explore how new satellite missions can help improve GPP prediction. In the first axis, my approach using an optimal ecosystem process as GPPmax and its limiting factors allow us to generate a new functional map that relate optimum ecosystem processes with climate information. This new map can be used as input for future global-scale modeling studies. On the second axis, Time, I find that for most of the ecosystems across the globe, an increase in short-wave incoming radiation, temperature, and vapor pressure deficit will produce an earlier DOYGPPmax (when compared with the mean DOYGPPmax) during the growing season. In the last axis, Space, I find that red-edge vegetation indices (estimated from Sentinel-2 images) improve the performance of the prediction of GPP. The exploration of the axes proposed in this dissertation contribute to frame our understanding of vegetation functional biogeography, by combining concepts from biometeorology, ecosystem physio-phenology, and satellite observations.