Browsing by Subject "Grassland management"

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Changing botanical composition of species-rich meadows through variation of management
(2022) Boob, Meike; Lewandowski, Iris
Species-rich hay meadows are threatened habitats for many plant and animal species. The biomass of these meadows has traditionally been used as forage for extensively kept ruminants. During the last decades, their habitat quality and area have been declining. On the one hand, the decline of species-rich hay meadows could be caused by increased fertiliser use as well as earlier and more frequent cutting. On the other hand, a reduction or abandonment of agricultural usage reduces their floristic diversity. This reduces important ecosystem services provided by these habitats, e.g. pollination. Therefore, benchmarking data on botanical composition and biomass is needed to estimate effects of different fertilisation and cutting regimes. This thesis aims at developing recommendations on how to manage species-rich hay meadows in order to conserve habitat functions and to enable agronomic usage at the same time. More specifically, management effects on botanical composition, biomass quantity and quality were investigated in a field trial running from 2013-2018. In this field trial, twelve different treatments were tested in a randomised block design at two sites in southern Germany. The different treatments consisted of a combination of three fertilisation levels (none, PK and NPK) and four different dates of first cut. The cutting date variants were chosen according to the phenology of dominant grasses before, at the beginning and at the end of flowering as well as a late cut at the seed-ripening stage. Both sites were species-rich hay meadows and each plot was fertilised annually and cut twice a year during the six-year field trial. The first study investigates changes in botanical composition. The number of vascular plant species did not significantly change after four years of fertilisation or cutting-date treatments, but botanical composition was affected significantly. The proportion of grasses was promoted by NPK fertilisation at both sites and by early cutting dates at one site only. Forbs were replaced by grasses because this site was dominated by the annual species Rhinanthus alectorolophus, a hemiparasite relying on generative reproduction. The second study addresses the question if living conditions of small plant species are affected by changed management. It was shown that shading reduced the proportion of small plant species due to the increased dry matter yield (DMY) caused by NPK fertilisation. It was concluded that annual NPK fertilisation containing 35 kg N ha-1 impairs the habitat function of species-rich hay meadows and, in the long term, excessive fertilisation could lead to reduced species numbers. Results of the third study revealed that although the date of first cut plays an important role in determining chemical composition of biomass, there is flexibility of choice at later cutting dates. Between the flowering and the seed-ripening stage, there were no significant differences in forage quality. However, late-cut hay is suitable as exclusive feed for horses only. Therefore, an early cut is recommended for use as biogas substrate and to be included into rations for extensively kept ruminants. In conclusion, general patterns of management effects were detected: Annual NPK fertilisation decreases the habitat quality of species-rich hay meadows. Based on the three studies presented in this thesis, the date of first cut in perennial plant communities should be handled more flexibly. This would benefit farmers, because higher forage qualities can be achieved. However, it was shown that there are site-specific effects. Plant communities containing annuals can be severely affected by advanced cutting dates, and the phenology at the date of first cut is crucial for the survival of these species. Interacting negative effects of fertilisation and cutting date on habitat quality suggest that the combination of late cutting date and NPK fertilisation should be avoided. Therefore, the best management at whole-farm scale appears to be a rotational cut and an extensive fertilisation of single meadows.