Grassland Management Experiment - GRASSMAN
Since the 1960s, meadow and pasture management has changed from extensive to intensive farming in most of Central Europe. N, P and K fertiliser input into managed grasslands roughly tripled with spectacular effects on productivity (Humphreys 1997); mowing frequencies of meadows increased from 1-2 to 3-5 (in intensive pasture systems up to 10) times per year. These changes had dramatic effects on biodiversity: Whereas extensively managed mesic grasslands may harbour as many as 70 species of vascular plants per 20 m2, diversity decreases rapidly with increasing management intensity and fertiliser input (Herben & Huber- Sannwald 2002). In permanent grasslands, differences in species diversity are most often a consequence of contrasting management intensities. Important ecosystem services may be impaired as well. Harvestable biomass increases with increasing mowing frequency up to a certain limit, but net primary production is generally reduced, as is root biomass and soil carbon accumulation (Dawson et al. 2000, Soussana et al. 2004). High fertiliser amounts and mowing frequencies may lead to enhanced trace gas emissions from grasslands (Schmid et al. 2001, Seidel et al. 2004), and can reduce pest control and pollination (e.g. Tscharntke et al. 2005). Currently, too little is known about important ecological functions and the economic value of ecosystem services associated with agriculture and forestry (Balmford et al. 2002, Robertson & Swinton 2005). Well-designed studies on the relationship between use intensity, biodiversity and ecosystem functions in such semi-natural ecosystems are urgently needed (Vandermeer & Perfecto 1997, Vandermeer et al. 2002).
The core research activity is a replicated experiment at the Relliehausen Experimental Farm north of Göttingen. A long-term field experiment with different management intensity treatments was established at a semi-natural, moderately species-rich grassland site. Experiments with a three-factorial design are started with the first factor being the diversity of the swards and the second and third factor the management intensity (fertiliser application and cutting). Three different levels of species richness (with dicots and monocots; only with monocots; only with dicots) were established by applying herbicides prior to the start of the experiment which exclude only monocot species or dicot species (in particular legumes). Differences in the diversity of plant functional types are associated with the three plant diversity levels.
The management intensity treatments comprise the following levels:
1. Nature conservation-orientated management, no fertilisation, one late cut per year.
2. High fertiliser application (180-30-100 kg NPK per ha and year), one late cut per year.
3. No fertilisation, three cuttings per year.
4. High fertiliser application (180-30-100 kg NPK per ha and year), three cuttings per year.
In total, 72 plots (15 x 15 m) were established in this semi-natural grassland (3 diversity treatments, 4 management levels, 6 replicates). The management intensity gradient itself will result in a gradient of species richness; thus, a matrix of plots with differential species richness will be generated.