Dynamics of forage production in pasture-woodlands of the Swiss Jura Mountains under projected climate change scenarios
Résumé
Silvopastoral systems of the Swiss Jura Mountains serve as a traditional source of forage and timber in the subalpine vegetation belt, but their vulnerability to land-use and climate change puts their future sustainability at stake. In this paper we couple experimental and modelling approaches to assess the impacts of climate change on the pasture-woodland landscape. We draw conclusions on the resistance potential of wooded pastures with different management intensities by sampling along a canopy-cover gradient. This gradient spans from unwooded pastures associated with intensive farming, to densely wooded pastures associated with extensive farming. Transplanted mesocosms of these ecosystems placed at warmer and drier conditions provided experimental evidence that climate change reduced herbaceous biomass production in unwooded pastures, but had no effect in sparsely wooded pastures, and even stimulated productivity in densely wooded pastures. Through modelling these results with a spatially explicit model of wooded pastures (WoodPaM) modified for the current application, results were extrapolated to the local landscape under two regionalised IPCC scenarios for climate change. This led to the suggestion that within the Jura pasture-woodlands, forage production in the near future (2000-2050 AD) would be affected disproportionately throughout the landscape. A stable forage supply in hot, dry years would be provided only by extensive and moderate farming, which allows the development of an insulating tree cover within grazed pastures. We conclude that such structural landscape diversity would grant wood-pastures with a buffering potential in the face of climate change in the forthcoming decades.
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