Resilience of turkish grasslands in the face of global change – example of Manisa

Semi-natural grasslands are dominated by natural herbaceous vegetation and play an important role e. g. in carbon storage, high quality primary production for livestock and pollination. They provide significant economic benefits for human well being, however, they are exposed to different pressures from global change. Climate change is one of the most important facets of global change. Due to global increase of greenhouse gases, temperature rises globally and extreme events such as drought are increasing in frequency and magnitude. Changes in climate can affect plant species and therefore change plant communities. Disturbed communities might be subject to invasion by introduced species. Besides climate change and invasion, land-use change is another important aspect of global change. Regarding grasslands, the difference in cutting height could play an impotant role for biodiversity and primary productivity with relevant effects on ecosystem functions and stability. Grasslands can react differently to extreme events such as drought, meaning that they can be affected on the short term and thus be not resistant. However, they might have the capacity to recover from a drought effect and thus be resilient. For Turkish grasslands, there are no studies that have evaluated the resistance or resiliance under drought. Grasslands are composed of many different plant species. For biodiversity and ecolgoy research, species richness is one of the most applicable and representative measurements. However, there are different sampling techniques of species richness and we need a better understanding if their differences matter. The reserach of this thesis has two main goals. First, we assess the effects of climate change (drought), invasion and land use on semi-natural grassland systems in Turkey. Second, we evaluate the effects of species richness sampling techniques on speciess richness counts in the grassland system. The field experiment was conducted on semi-natural grassland system during the years of 2013-2015 in the campus of Celal Bayar University. Drought was simulated by plastic rain out shelters in the period from 2nd/5 to 3rd/5 of the growing season in the first year (2013). To determine the invasion effect two invader species were planted at the end of the drought season, i.e. Senecio inaequidens DC. and Lupinus polyphyllus Lindl. Invasion effect was also tested using twenty different species of invaders by adding their seeds to the grassland. To test the land use effect related to cutting height we carried out 3 cm and 10 cm cutting levels and abandonment. Regarding the second goal, we studied the effect of sampling techniques on species richness counts. Here, the effects of plot shapes (square, rectangle (1:4) and thin elongated (1:16)) and plot dispersions (subblock, block and site level) on speciess richness was tested using 2688 sampling units in the grassland site. Analysis were carried out to test the effect of drought, land use and invasion on plant cover, plant speciess richness and aboveground biomass of the grassland. Generally, cover estimates provided more meaningful results than the other parameters. According to the results, drought, invasion and land use as a single factor and also regarding their interaction had no effect on grassland system in terms of biomass and speciess richness including all functional groups. Drought as a single factor increased the cover of legumes but reduced the cover of forbs. However, the forbs recovered in the following year. The interaction of drought and invasion had significant positive effects on the cover of graminoids. However, invaders of Senecio inaequidens DC. and Lupinus polyphyllus Lindl. did not grow well in the grassland system. Similar results were obtained in the further add on experiment of invasion of twenty different species of invaders. Most of them were able to germinate during the first two weeks but none of them came into flower at the end of season as they did not survive. Regarding the effects of different sampling techniques on species richness counts, there are slight differences between square and rectangle (1:4) plot shapes but the difference gets more meaningful with an elongation of the rectangle (1:16). In addition to this, plot dispersion is more important than plot shape for the species richness count and the extent of dispersion was the most influencing factor. In conclusion, drought has only low effect on the cover of legumes and non-legume forbs but there were no more differences in the year after drought. Neither the single factors, i.e. invasion and land use, nor their interaction had effect on the biomass production, the total plant cover or the species richness of the grassland system. Therefore we conclude that the grassland system is resilient and keeps community stability.