Project 1: Cross-scale quantification of vegetation–atmosphere interactions and biodiversity change

Project Team

Gabriela Schaepman-Strub
Pascal Niklaus
Maitane Iturate
Jaqueline Oehri

Research aims - The project investigates biodiversity-effects on vegetation-climate interactions. Focal ecosystems are arctic tundra and terrestrial ecosystems in Switzerland, although all sites and model ecosystems will contribute to this project.

Field experiment in arctic tundra – We combine process-based modelling and statistics to link terrestrial biodiversity measures, in-situ proxy observations of energy and carbon fluxes, and corresponding satellite-inferred landscape-scale products (albedo, vegetation biochemistry, canopy structure, evapotranspiration). The 3D radiative transfer model DART will be used to explore how species diversity influences albedo, canopy light distribution, and ground level radiation throughout the growing season (Gastellu-Etchegorry et al., 1996). The parameterization of DART requires the definition of a limited number of plant functional groups through selected traits that are representative of the functional and taxonomic diversity of tundra vegetation, but at the same time adapted to the intermediate complexity of DART (Boulangeat et al., 2012). While the shortwave module of DART is well tested, the adaption of the heat flux component to natural ecosystems will require further model development. Running DART in the energy budget mode will allow investigating the small spatial scale relation of micro-climate with functional trait diversity. Finally, the model will be parameterized at the landscape level, integrating small-scale patches of differing diversity and size to study the contribution of micro-climatic feedbacks by communities to the landscape scale.

Predictions will be validated using field observations at the patch scale and satellite-inferred land surface products at landscape scale. Upscaling procedures for in-situ proxies will be developed in collaboration with Project 7, based on Bayesian hierarchical dynamic modelling. Given the complexity of processes, we will aim at simplifying the relation of modelled radiation fields with satellite observations and in-situ data at respective spatial and temporal scales in collaboration with Project 7.

Comparative study of effects of landscape-level diversity in Switzerland – We  test for the relation between biodiversity and ecosystem functioning at the ecosystem and landscape-scale. These investigations will cover spatial scales that have not been explored to date in biodiversity research, despite their importance. Diversity measures will be obtained from the Swiss Biodiversity Monitoring (BDM) programme (ecosystem-level) and from land use/cover maps and inventory data (landscape scale). Ecosystem functioning will be gauged from remotely-sensed data and include basic processes such as productivity and growing season length. We further focus on processes characterizing interactions of the ecosystem with the atmosphere since these are crucial in understanding and modeling effects of biodiversity on climate (e.g. components of the surface energy and water balance). Given that the analysis will depend on data sensed over many years, sometimes even decades, we will be able to test for effects on the stability of these processes to inter-annual variation and extreme events (e.g. drought). Data are validated at selected sites using ground-based measurements. These ground-based data either will be collected by the PhD student, in collaboration with other subprojects within this URPP, in collaboration with the Swiss Biodiversity Monitoring programme, or be available from other sources (e.g. camera networks recording phenology, other observational networks). The relationship between biodiversity, ecosystem functioning/land-atmosphere interactions will be analyzed adopting a statistical framework taking into account effects of environmental parameters unrelated to biodiversity and spatial autocorrelation.

Expected contributions to research theme – The research contributes a new and quantitative understanding of feedback mechanisms among vegetation diversity, energy and carbon cycling. Biodiversity research has so far largely focused on the plot-scale, ignoring interactions with the atmosphere. For the Arctic tundra site we will establish a modelling framework to quantify the effect of biodiversity on vegetation-atmosphere interactions. While Arctic biodiversity is increasingly assessed and monitored (Arctic Biodiversity Trends, 2010), the role of plant diversity in vegetation-atmosphere interactions has not been systematically addressed for tundra ecosystems at the local to regional scale. In contrast to sophisticated land surface schemes parameterized at the plant functional type level, the second approach will use statistical methods to test relations of species diversity at the community and meta-community level.