Effects of grazing by free‐ranging cattle on vegetation dynamics in a continental north‐west European heathland

Abstract

Summary1. Abandonment and eutrophication are major threats to traditional pastoral landscapes and their wildlife in Europe. Social and economical developments have rendered traditional pastoralism impracticable. More knowledge is needed about the eects of grazing with free-ranging herbivores, which is increasingly used as a substitute for the traditional herding system. 2. We studied the eects of free-ranging cattle on the recovery of Calluna heather, tree encroachment and plant species richness in six habitats in a grass-rich Dutch heathland during a 10-year period. The habitats diered in soil fertility, initial heather±grass ratio and developmental stage of Calluna. 3. Despite preferential grass defoliation, cattle grazing neither reduced grass cover in grass heath nor prevented grass invasion in heather. Grass invasion failed only in a nitrogen-poor turf-stripped Calluna heath. Grazing induced a substantial Calluna recovery in grass heaths on podzolic soils, but its recovery failed in grass heath on a phosphorus-rich medieval arable ®eld. As a consequence, the grass± heather mosaics generated by free-ranging cattle were restricted to habitats of intermediate soil fertility. 4. Grazing did not prevent encroachment by pine and birch. Removal by the site manager prevented conversion of 10±20% of the open heathland to forest. 5. During the ®rst 5 years, grazing induced a signi®cant increase in species richness in all habitats. During the second 5 years, species richness stabilized in grass heath and heather±grass mosaics and it declined in the pioneer Calluna heaths. 6. We found indications of various nutrient-mediated grazing eects on the competitive balance between grass and woody pioneers. These suggest that nutrientmediated feedback might be an important explanatory mechanism for the described vegetation mosaic cycling in heathlands. 7. Free-ranging grazing did not remove the high atmospheric nutrient inputs of the whole area. Substantial amounts of nutrients were redistributed from the grass lawns to the forest. 8. Free-ranging grazing combined with tree cutting appeared to be a suitable management regime for the maintenance of species-rich open heathlands with dynamic grass±heather mosaics. 9. Without tree cutting, free-ranging grazing would have created dynamic tree±grass± heather mosaics in open heathland. Wood±pasture landscapes are fundamentally different from the open heather-dominated heathlands produced by the traditional sedentary farming system. Integrated grazing of heathland, nutrient-rich farmland and forests accelerates this change. Alternative grazing regimes are discussed.

Effects of cattle and rabbit grazing on clonal expansion of spiny shrubs in wood-pastures

“…Our results underline the generally overlooked potential for small selective herbivores to control the dynamics of woody vegetation in grazed ecosystems (Weltzin et al 1997). By controlling the expansion of spiny shrubs -and the dependent recruitment of palatable trees within these shrubs -rabbits play a similar key engineering role in the landscape as is regularly claimed for large herbivores (Olff et al 1999;Bokdam & Gleichman 2000).…”

“…Various studies on ancient grazed ecosystems indeed suggest that large herbivores create and maintain this landscape heterogeneity and inherent diversity (Vera 2000;Bakker, Olff, Vandenberghe, De Maeyer, & Smit 2004;Smit, Beguin, Buttler & Müller-Schärer 2005;Smit, den Ouden & Müller-Schärer 2006). Also on abandoned agricultural land, heathlands or riverine floodplains ('nature development projects') the introduction of large herbivores leads to heterogeneous landscapes (Bokdam & Gleichman 2000;Van Uytvanck, Maes, Vandenhaute & Hoffmann 2008).…”

Soil Microbial Community Changes in Wooded Mountain Pastures due to Simulated Effects of Cattle Grazing

“…Furthermore, the spatial patterns of the three activities are not congruent. Cattle have, for example, preferred resting and dunging areas, which may be different from their preferred grazing areas (Bokdam and Gleichman, 2000). In addition, the field studies compared existing situations with little control over the fields and independent variables (pseudoexperiment) (e.g., Bardgett et al, 2001;Donnison et al, 2000;Grayston et al, 2004) and microcosms were usually used in experiments (e.g., Bardgett et al, 1999;Jordan et al, 2003).…”

“…Grazing is the main biotic factor affecting ecosystem structure and dynamics in pastures (Bokdam and Gleichman, 2000;Olff et al, 1999). The effect of cattle or sheep on their environment can be subdivided into three categories of stress factors: herbage removal, dunging and trampling.…”

Interacting effects of grass height and herbivores on the establishment of an encroaching savanna shrub

“…There is considerable debate on how rainfall (Fensham and Holman 1999;FernandezGimenez and Allen-Diaz 1999;Fynn and O'Connor 2000) and grazing (Hulme et al 1999;Bokdam and Gleichman 2000;Sternberg et al 2000) should be taken into account in terms of management of shrub encroachment. The results of this study indicate that reductions in D. cinerea regeneration may occur when drought acts in concert with light grazing.…”