Connecting the green and the grey world – an experimental approach to separating climate, vegetation and geochemical effects on nutrient cycling along a climate gradient

01/01/2019 to 31/12/2022

One component why biota might shape the Earth’s surface is related to their active role as “weathering engine”. However, efficient nutrient cycling of both plants and soil microorganisms might reduce their need to access nutrients contained in bedrock especially under
increasingly progressed weathering towards more humid climate. In addition, nutrient cycling is affected by even higher trophic levels i.e., herbivory. However, it is virtually unknown how climate, especially rainfall, interacts with herbivory in affecting nutrient cycling and litter decomposition. Our overall goal is to dissect the relative importance of biotic (plants, microorganisms, herbivores) and abiotic factors (geology, climate) on processes related to weathering and biogeochemical nutrient cycling. We will directly link biological and geochemical processes by a) doing in-depth studies on processes at
the interface between the green, the brown, and the grey world that build on the foundations laid in Phase 1, and by b) doing integrated analyses of this data and of new data collected by a large interdisciplinary consortium collaborating in our drought experiment. We expand our initial focus on plant-soil-geology feedbacks related to
litter both ‘downwards’ and ‘upwards’. Specifically, we will focus on a) nutrient limitation and nutrient efficiency of plants and soil microorganisms, and b) the influence of herbivory on decomposability of litter that both potentially affect biogeochemical rock weathering. To that end, we combine the EarthShape space-for-time approach with
mechanistically orientated field experiments that manipulate climate conditions on-site. With this approach, we address the following overarching questions: Can spatial climate gradients, i.e. the result of long-term climatic impact on the earth surface, serve as proxy for
short- to medium-term temporal climatic changes? Which processes (‘green vs. brown vs. grey’) can be best described by spatial gradients? We will be able to answer these questions based on observations and experiments in the field as well as plant and herbivory experiments in the greenhouse. To assess nutrient cycling, we will measure nutrients in plants, soil and soil microorganisms
complemented by innovative stable isotope tracers. By addressing the explicit role of a whole suite of biota in nutrient cycling, we will reveal their potential role as “weathering engine” which is a backbone of
EarthShape. Additionally, our study is the first in Chile to investigate climate change impacts on ecosystem processes using large field experiments.