Basic Hierarchic Design
1000 Grid Plots
Each exploratory comprises a large number of study plots differing in their intensity of investigation. Because the first phase of the project considers only grassland and forests, a grid of a very large number of study points (in total 1000 plots per exploratory) were chosen in these ecosystems. On these plots, the number and abundance of plant species as well as land use types and intensity were recorded. In addition, a soil sample from each plot are analysed.
Acoustic monitoring, spotting and trapping are used to assess the diversity of birds, bats, and other mammals in the selected forests and grassland.
100 Experimental Plots (EPs)
After this first assessment, one hundred more intensively studied plots (50 in forest, 50 in grassland per each exploratory) were selected in 2007 to represent broad gradients of land use intensity ranging from near-natural, protected sites to intensively used ecosystems. These intensively studied plots contain instrumentation to measure soil and air temperature and soil humidity, and have a appropriate size for experimental manipulations.
On these intensively studied plots, the diversity of further taxa is assessed, including bees, Ichneumonidae and other Hymenoptera, Heteroptera, Diptera, Chrysomelidae, Curculionidae, Carabidae and xylobiontic beetles. These taxa are assessed using various collection methods and types of traps (suction sampler, sweep nets, malaise traps, fogging). In addition, the pollinator nets for grassland plants and forest understorey plants are quantified by repeated collecting pollinating insects on individual plants.
For the intensively studied plots, we study associated ecosystem processes, such as standing biomass and growth in forests, annual net primary productivity in grasslands, soil respiration and carbon and nitrogen pools in different parts of plants. On a further subset 16 very intensively studied plots (VIPs), the microbial community and the diversity of mycorrhizal fungi are assessed with molecular markers.
Experiments
On the EPs and VIPs, a number of experimental manipulations is performed. They mostly involve manipulation of the plant diversity, exclusion of functional groups or shift of resources to study the consequences on the diversity and on ecosystem functioning for a given land-use type and land-use intensity. These experiments address causal relationships beyond the correlative evidence gained by observations and monitoring. Following experiments are set up:
- A seed sowing experiment in grasslands to overcome seed limitation and increase plant diversity and primary productivity
- A seed sowing experiment of tree species to test seed limitation and recruitment success as a function of diversity and species identity of maternal trees
- A fencing experiment to exclude large herbivores to assess their influence of tree recruitment and tree diversity
- A litter translocation experiment to test for changes in soil carbon and decomposer community
- Dead wood manipulation experiments on ground and in the canopy
- A shrew and rodent exclusion experiment to assess their effect on the arthropod diversity
- A bird and bat exclusion experiment with nets to assess their importance for arthropod diversity and seed set of plants
- Predator-prey manipulations e.g. introducing aphid colonies to assess their survival and the associated predator community
- Herbivory experiments to quantify the degree of herbivory on individual plants and to assess plant fitness on sprayed and non-sprayed plants