Long-term stability of sward patch structure under different intensities of cattle grazing

In low-intensity grazing systems, selective defoliation by the grazing animals can lead to a mosaic pattern of short, frequently grazed, and tall, rarely grazed patches. If the spatial pattern of these patches is stable over time, this may result in divergent development of botanical composition and nutrient cycling. Using sward height data from permanent quadrats, we tested the hypothesis that, under continuous cattle stocking, patch grazing can create sward structures that are stable not only over the short term, but also over several years. For three grazing treatments with different stocking rates, the transitions between three sward height classes (short, medium and tall) were quantified for three time scales: seasonal, interannual and long- term transitions. With the exception of long-term transitions under the highest stocking rate, transitions between sward height classes were non-random, confirming the initial hypothesis of short- and long-term patch stability. A stable sward height pattern may enhance biodiversity and has methodological consequences for studying extensive pastures.