Interactive plant-trait and climate effects on soil organic carbon along the Chilean coastal cordillera

• Applicant: Professorin Dr. Maaike Bader
• Subject Area: Physical Geography
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280611154

The input of organic carbon into the soil is one of the major drivers of weathering and erosion. This input, in turn, is primarily controlled by interactive effects of vegetation and climate. Understanding how climate and vegetation together determine soil organic carbon, as an energy source for microorganisms as weathering engines and as a stabilizing factor in erosion, is one of the major scientific goals of the EarthShape program (SPP 1803). With this project we aim to pursue this goal by studying organic carbon fluxes, from plant productivity to litter decomposition and carbon dynamics in soils, disentangling plant and climate effects. Based on our hypothesis that the relative importance of climate and plant traits may be scale dependent we will work at multiple spatial-climatic scales. These scales encompass three biomes along the Chilean coastal cordillera (arid, mediterranean and wet-temperate) and two contrasting study sites within each of these biomes. The investigation of soil organic carbon characteristics below contrasting plant types within these three biomes and six study sites, will allow us to partially decouple vegetation and climate effects. The effect of plant and litter diversity on litter decomposition will also be studied. A further decoupling is achieved by translocating plant litter and soils between the three biomes and sites in a fully-reciprocal experiment over a period of two years. Vegetation will be regarded from a functional point of view, carbon inputs, via primary productivity, litter decomposition, and soil organic carbon transformations being described as functions of plant functional traits (chemical, physical and phenological). To test impacts of vegetation and climate on subsoil organic carbon characterized by a high persistence and a long turnover rate we will translocate subsoil up to the surface where temperature, moisture and organic carbon inputs increase. We will apply innovative lab devices (HPLC, ICM-PS, EA-IRMS, AQUALOG) to describe the chemical composition (C, N, P, 13C, lignin, tannin, trace elements) of leaf, litter and of soil organic carbon (particulate and dissolved) along the soil profile. Simultaneous absorbance-fluorescence measurement technique will advance the analyses of dissolved soil organic carbon compounds including Excitation Emission Matrix (EEM) Fluorescence and Parallel Factor Analysis (PARAFAC) techniques. The joint data analysis is an essential part of this project to connect the plant, litter and soil data following the proposed multi-scale approach. Our results will include a statistical model predicting soil organic carbon contents based on climate and vegetation traits, including the main steps between productivity and final soil carbon contents. This improved process knowledge is important for understanding and modelling carbon cycles and geomorphology-related soil processes.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1803: EarthShape: Earth Surface Shaping by Biota
• International Connection: Austria, Chile
• Cooperation Partners: Professor Dr. Jörg Bendix; Dr. Theresa Blume; Professor Dr. Roland Brandl; Professor Dr. Lutz Breuer; Professorin Dr. Nina Farwig; Dr. Christina Fasching, Ph.D.; Dr. Rodrigo S. Rios; Dr. Alfredo Saldaña; Professor Dr. Michael Scherer-Lorenzen; Professor Dr. Thomas Scholten; Professorin Dr. Marie Anneke Spohn; Professor Dr. Dirk Wagner; Professor Dr. Markus Weiler; Professor Dr. Gerhard Zotz