The main objective of the theoretical work in Phase 1 is to examine the validity of the AHTO under a wider range of scenarios and conditions than those examined in the original model. Therefore, our modelling strategy was designed to maximize generality by adopting a general approach that takes into account those mechanisms and interactions which are common to any kind of organisms. This approach, however, has the limitation that it ignores processes and interactions that are important in structuring grassland communities, our target in this project. Thus, a major need at this stage is to shift from our current, highly abstract and general modeling approach into a more mechanistic approach that takes into account those processes and interactions that are most important in determining the diversity of real grasslands. Such an extension will allow us to directly and tightly link our theoretical, experimental, and observational findings.
Our main objective in the experimental component of Phase 1 was to establish a long-term microcosm experiment that will allow us to test hypotheses generated by our models under highly controlled conditions. A long-term monitoring of this extensive experiment is crucial because community level responses to manipulations of the environment are driven by demographic processes (birth, death and dispersal) which operate at relatively long time scales, especially in perennials and plants with clonal propagation. Thus, a major need of our experimental component is to continue monitoring the responses of the artificial communities to the various manipulation treatments. Another need resulting from the shift in our modelling approach into a more mechanistic approach is to obtain appropriate empirical data for parameterizing our new models. To this end we plan to establish a new experiment in which we will measure growth responses of individual plants to experimental manipulations of relevant environmental variables.
The most important need of our current work is to link it more directly to the general framework of the BEs. This extension is strongly supported by recent syntheses from the BEs, all of which highlighting habitat heterogeneity as a main potential - but not confirmed - explanation for various patterns and processes found across the land use intensity gradient of the Exploratories (e.g. Blüthgen et al. 2016, Solivieres et al. 2015, Manning et al. 2015). Thus, in the second phase we plan to add an observational component in which all aspects investigated in the theoretical and experimental subprojects will be studied also in a wide range of grassland BEs that will be selected to represent the main land-use gradients.