Publikationen (FIS)

Bird use of short rotation coppice strips within a modern silvoarable agroforestry system during the winter season: Comparison of different coppice strip variants and hedgerows

verfasst von
Felix Zitzmann

Silvoarable agroforestry systems (AFS) with short rotation coppice strips (CS) are considered as a potential measure to promote biodiversity in agricultural landscapes while simultaneously producing arable crops and woody biomass. However, there are few studies that examine the actual potential of these novel land use systems to enhance biodiversity. Therefore, in this study the use of three different variants of CS ("Conventional" (CS-C), "Aspen" (CS-A) and "Ecological" (CS-E)) by birds during the winter season was investigated within an experimental AFS site in northern Germany. In addition, surveys in hedgerows in the immediate vicinity were conducted to compare the habitat function and quality of these woody habitats of traditional AFS with CS (representing elements of modern AFS). Bird surveys were made by point counts on eight dates between November 2021 and February 2022, with each section surveyed exactly 10 minutes per visit. In addition, the food supply of seed- and fruit-bearing woody plants within the variant "CS-E" (where native woody species were planted with the aim of an ecological improvement in addition to high-yielding poplar clones) and within the hedgerows was assessed. Overall, hedgerows had the highest species numbers and the most birds were observed there. In fact, even more species were recorded and more birds were observed in the hedgerows (16 species, 195 bird observations) than in all three CS variants together (all CS variants together: 13 species, 136 observations, thereof 12 species and 116 observations in CS-A, 5 species and 16 observations in CS-E and 3 species and 4 observations in CS-C). In the CS sections, no birds were detected on a majority of the visits (77–95%), while in hedgerows birds were detected on 83% of the visits. At the individual recording dates, significantly more species were detected and more birds were observed in the hedgerows than in CS-C and CS-E on each of the eight dates. In contrast, hedgerows and CS-A differed significantly (hedgerows with more species and bird observations) on only three out of eight dates. Among the three CS variants, CS-A had the most species and bird detections overall; however, there were no significant differences between the three variants on any of the eight recording dates. With regard to the food supply associated with the woody plants, an equal number of woody species were found in the CS-E and hedgerow sections. However, the number of woody species actually bearing seeds and fruits and the number of trees/shrubs carrying seeds and fruits were significantly higher in the hedgerow sections. Thus, the plant-based food supply offered by the hedgerows was much greater and more diverse. Overall, the results show that hedgerows are more important (foraging) habitats for birds in the winter season than CS. The surprisingly poor performance of the CS-E variant was probably caused by the fact that the native woody species were harvested for the last time one year before the study and are usually harvested at short intervals (3–6 years), which explains the limited presence of seed- and fruit-bearing trees and shrubs despite the planting of various native woody species. Thus, the native woody species in CS-E should be harvested much less frequently so that this variant achieves greater importance as foraging habitat for birds. The clear preference for hedgerows over CS and their much more diverse and extensive food supply even at the end of the survey period, together with the (currently) low use of CS-E, indicate that there was a sufficient supply of seed- and fruit-bearing trees and shrubs in the surrounding landscape and that the integration of CS and the planting of native woody species in CS-E therefore added only limited additional value. Modern silvoarable AFS with CS are therefore likely to be more important in cleared agricultural landscapes that lack higher-quality woody habitats such as hedgerows or groves. Thereby, the additional cultivation of native, seed and fruit-bearing woody species in short rotation or for the production of timber could further increase the food supply and structural diversity of the CS.

Institut für Umweltplanung
Naturschutz und Landschaftsökologie
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