Patch-differentiation of vegetation and nutrient cycling in an extensive pasture system

Abstract

In extensive grazing systems, ‘patch-grazing’ may lead to the development of a mosaic structure consisting of short, frequently defoliated, and tall, infrequently defoliated patches. If spatial patterns of sward structure are stable over time, this may result in a long-term differentiation of botanical composition and matter fluxes between patch types within a pasture. Patch dynamics, botanical composition and topsoil nutrient concentrations of different patch types were investigated in a long-term grazing experiment in the Solling hills, Germany, where differentiated grazing intensities have been applied for 10 years. Continuously stocked beef cattle grazed to target sward heights of 6 or12 cm in a put-and-take system in replicated 1-ha paddocks. Time series of point-specific sward height measurements showed that patches were relatively stable within- and between-seasons. Botanical composition as well as soil phosphorus and potassium concentrations differed between short and tall patches. While grazing intensity influenced the frequency of short and tall patches within a pasture, differences between patch types were larger than those within the same patch type between different grazing intensities. The results highlight the importance of studying biodiversity as well as nutrient dynamics of extensive pastures in a patch-specific way. Through the development of pasture areas with different functionality, extensive grazing systems have the potential to maintain biodiversity while sustaining agricultural production.