Changes in vegetation diversity and composition following livestock removal along an upland elevational gradient

Abstract

© iForest -Biogeosciences and Forestry IntroductionCalluna vulgaris-dominated heathlands are cultural landscapes, derived from previouslyforested ecosystems, which have been subject to human manipulation and management for several millennia. Heathlands are of international conservation importance (Thompson et al. 1995, García et al. 2013) and this is recognized in national and international legislation (Maddock 2011, EU Habitats Directive 92/43/EEC). They owe their open character to low-intensity traditional livestock grazing and managed burning (Webb 1998, Fernandes et al. 2013. Habitat degradation, associated with poorly-managed livestock grazing is, however, a global issue facing many tropical, semi-arid and temperate ecosystems (Moleele & Perkins 1998, D'Odorico et al. 2012, Fagúndez 2012. Significant potential exists for livestock grazing to induce dramatic changes in ecosystem state from which restoration can be difficult (Suding et al. 2004). Throughout Europe large areas of heathland habitat have become increasingly degraded over the last century (Fagúndez 2012). Calluna-dominated communities have been lost due to changes to managed fire regimes ; nutrient deposition associated with atmospheric pollution (Friedrich et al. 2011, Bobbink & Hettelingh 2011; acid deposition (Bakker & Berendse 1999); and land-use conversion (Hester et al. 1996). In the United Kingdom there are a growing number of agencies and organisations focused on landscape-scale ecosystem restoration in the uplands. Objectives are often focused on tree planting and the restoration of forest ecosystems (see Hobbs 2009 for an overview), but there is also recognition of the desirability of restoring forest ground flora and a diverse mosaic of habitat types that includes woodlands, heathlands and forest edge ecotone communities (Humphrey et al. 2003). Degraded heathlands are often dominated by competitive grass species such as Molinia caerulea (purple moor grass) and Nardus stricta (moor matgrass). Both of these can attain high levels of abundance, lead to communities with relatively low levels of diversity and can pose significant challenges for restoration practice (Grant et al. 1996, Marrs et al. 2004. A number of studies have examined the effects of grazing regimes on heathland communities, often concluding that restoration prescriptions need to be sitespecific. For example, whilst it has proved possible to facilitate heathland recovery by simply reducing grazing pressure (Anderson & Radford 1994, Hulme et al. 1999, Hulme et al. 2002, often it has taken additional interventions to allow Calluna establishment. Successful treatments have included soil disturbance by cattle trampling, rotavation, herbicide application and reseeding (Marrs et al. 2004, Mitchell et al. 2008) and, where nutrient enrichment is an issue, topsoil removal (Verhagen et al. 2001). Such intensive restoration actions may require managers to make difficult trade-offs as they may maximize Calluna cover but can also lead to the loss of other components of the community (L...

Don't let spurious accusations of pseudoreplication limit our ability to learn from natural experiments (and other messy kinds of ecological monitoring)

“…A paper recently submitted by the one of the authors here, and describing the effects of stock removal on landscape‐scale patterns in species richness (Davies and Bodart ), encountered just such a problem. The monitoring described in the paper examined differences in vegetation on either side of a single fenced exclosure used to remove stock from roughly half of a 640‐ha farm in the Scottish Southern Uplands.…”

“…In cases like the lead author's grazing research (Davies and Bodart ), one should also consider whether, had this been a strict “experiment”, it would have been found acceptable. In the case of the above study, had we established an experiment at our site with multiple small experimental grazing exclosures (Fig.…”

Effects of management regimes on structure, composition and diversity of seasonally inundated herbaceous communities in the Mkomazi National Park, Tanzania

“…(Collins, 1987). However, grazing can also contribute to allow different plant species to coexist by preferentially consuming competitively dominant plants (Collins, 1987;Davies & Bodart, 2015). Indeed, several studies found that grazing may induce changes in vegetation structure without negatively affecting species richness (see e.g.…”

Controlled Grazing of Maize Residues Increased Carbon Sequestration in No-Tillage System: A Case of a Smallholder Farm in South Africa

“…While the Pseudoreplication design is not ideal for most ecological trials, using such an approach is justified considering the values of this experiment, i.e., natural landscape for local community demonstration, in a region scarcely studied in this sense so far, and potential statistical solutions [44,45]. Hence, restricted maximum likelihood mixed (RMEL) was used in the current study, where the treatments were considered fixed effects while the subplots (pseudo-replicates) were the random effects.…”