دانلود رایگان مقاله واکنش تابعی برگ و پلنتوپر به لقاح و آبیاری مدرن مراتع یونجه

Abstract

In the drier regions of the European Alps, traditional land-use of montane and subalpine meadows, i.e. extensively managed with solid manure application and irrigation via water channels, is currently shifting towards application of slurry and aerial irrigation. The impact of these new practices upon biodiversity remains poorly understood and calls for quantitative assessments of their effects. Relying on a full block design, we tested the effects of six management treatments corresponding to an increasing gradient of farming intensification (fertilisation with slurry and/or irrigation with sprinklers) on Auchenorrhyncha (Hemiptera) communities occurring in the inner Swiss Alps. The experimental set up consisted of: control plots (no fertiliser, no irrigation; C-plots); plots that received only fertiliser (F-plots); plots that were only irrigated (I-plots); and plots that received low-, medium- and high-input of fertiliser and water (F + I 1/3-plots; F + I 2/3, F + I 3/3-plots; 3/3 corresponds here to the input level necessary for achieving maximum theoretical hay yield locally). After two years of experimental treatment (2012), plots that were only fertilised or only irrigated showed no change in the population sizes of Auchenorrhyncha, while plots that received low-, medium- and high-input of fertiliser and water harboured significantly higher abundances (1.9, 1.5 and 1.4 times higher, respectively), biomass (1.8, 1.6 and 1.8 times higher, respectively), as well as species richness (+27–30%, on average) than control plots. Abundances and species richness were also higher in plots with low-input of fertiliser and water compared to fertilised only plots. Monophagous and oligophagous species were most abundant in plots with low-input of fertiliser and water. Medium- and high-input treatments (F + I 2/3 and 3/3) increased the number of generalist (eurytopic) species, while only low-input treatment (F + I 1/3) boosted the more specialised (stenotopic) species. This provides support to the hump-shaped diversity-disturbance relationship and guidance for sustainable management of biodiversity-rich mountain hay meadows.

Conclusions and management recommendations

Shallow fertilisation with slurry and irrigation with sprinklers promptly enhanced conditions for Auchenhorryncha in very low-input mountain hay meadows in the short term, notably by increasing the abundance of monophagous and oligophagous species and the richness of stenotopic species. A greater application of fertiliser and water still enhanced abundance and species richness of Auchenorrhyncha, but exclusively through an increase of trophic and habitat generalists. We predict that a prolonged application of our experimental manipulation beyond two years would further negatively impact plant species richness (due to a growing accumulation of fertiliser; Humbert et al., 2016); this would further impoverish the palette of host-plants for Auchenorrhyncha, leading to more detrimental effects for monophagous and stenotopic species. In many mountainous regions of Europe, the management of hay meadows on flat and accessible terrain is currently undergoing massive intensification, whereas meadows on steep, less accessible slopes are progressively being abandoned (Tasser & Tappeiner, 2002). This dichotomous, negative trend should be reversed. Based on this research on a key indicator taxon of mountain biocenoses, we can already recommend applying doses of fertiliser and water roughly equivalent to one third of the amount that would be necessary to achieve the maximum theoretical local hay yield (our figures for F + I 1/3 can serve as reference, see Table 2). Future results of our ongoing experiment will certainly help fine-tune these prescriptions. Finally, future studies should also investigate to which extent organisms situated higher up along the food chain (predatory arthropods, vertebrates) might benefit from the management recommendations that promote emblematic taxa such as Auchenorrhyncha, especially given the staple food resource that they represent for higher trophic levels.