BEAM I – Impact of land-use and functional diversity on species diversity and stability of grassland communities in fragmented landscapes
In this cooperative project we aim for an understanding of the various mechanisms underlying the link between diversity and ecosystem function. To achieve this goal we will develop based on and as an expansion of Hubbell’s neutral theory, theoretical models to test the plausibility and scope of basic and general explanations for the diversity-function relationship. On the other hand we will design data-based mechanistic models which will allow to integrate existing and future data in such a way that important hypotheses about the link between diversity and ecosystem functioning can be evaluated.
Our primary goal within Task 1 (PI Hovestadt) is to learn more about the principal mechanisms which lead to the establishment of certain diversity patterns. To achieve this we will use different theoretical and modelling approaches to test the plausibility and generality of alternative explanatory approaches. As a reference and null-model we will use Hubbel’s “neutral theory”. However, we will analyse the predictions of this theory for non-equilibrium conditions and expand it to apply to heterogeneous landscapes (forgoing the neutrality assumption). With the latter modification we also develop instruments to model the link between diversity and ecosystem function about which Hubbell’s theory does not make any predictions.
1. The correlation in diversity across different, non-interacting functional groups depends on the similarity in fundamental life-history attributes like life-expectancy, fertility, dispersal potential, resistance against disturbance, or specialization.
2. Diversity patterns and correlations of them across different functional groups are distinctly different in equilibrium and non-equilibrium phases, e.g. following habitat disturbances, landscape alternations, or during the invasion of new species.
3. Landscapes showing fine-grained habitat diversity are characterized by high alpha- but low beta- diversity and will be dominated by habitat generalists. Ecosystem functions will not be provided at optimum (maximum) level. Opposing predictions can be made for landscapes dominated by coarse grained habitat diversity.
Subproject 2: Towards a mechanistic understanding of biodiversity and its functional consequences – the Biodiversity Exploratory additional modeling component
We seek to develop, test and apply novel grid-based mechanistic process models to simulate changes in plant functional trait (PFT) diversity in grassland succession in a regional context of land-use diversity. A bottom-up approach will be used to link mechanisms and processes acting at a local scale to the regional/landscape level.
Task 2 proceeds in three steps: In task 2.1, the small-scale, individual based, spatially-explicit PFT grassland model will be developed. In task 2.2, the model will be further developed into a patch-level state-and-transition grassland model. Finally, in task 2.3, the model will be linked with a landscape model, which provides the basis to further scale up to the regional level.
Subproject 3: Forest diversity and functioning in response to management and herbivory
PIs Prof. Dr. Christian Wirth, Dr. Markus Reichstein