Long‐term impacts of changed grazing regimes on the vegetation of heterogeneous upland grasslands

Abstract

1. Marginal agricultural land, which in the UK refers to upland grazings in particular, is going to see changes in management driven by markets, subsidies, grants and environmental change with implications for biodiversity. Using a large-scale, long-term grazing experiment in the UK uplands we assessed the impact of intensification (tripling sheep numbers), abandonment (removal of sheep) and grazer diversification (partial replacement of sheep by cattle) on vegetation composition in a heterogenous area of grassland. 3. Species benefiting from increased grazing included sweet vernal grass (Anthoxanthum odoratum), mat grass (Nardus stricta) and deer grass (Trichophorum cespitosum). Species that benefitted from the removal of grazing included bog asphodel (Narthecium ossifragum), bracken (Pteridium aquilinum) and blaeberry (Vaccinium myrtillus). 4. Responses differed between vegetation communities; more productive acid grassland communities showed little change when grazing was removed, whilst less productive mire communities contained species, capable of increasing after grazing removal. Increased grazing and, to a lesser extent, the introduction of cattle increased species diversity. 5. Synthesis and applications. Marginal agricultural grassland will likely see management change driven by markets, subsidies and environmental change. Vegetation change in these relatively infertile grasslands is slow and features shuffling dominance amongst species in the initial vegetation. Initial structural changes affect other trophic levels in this experiment; the slow change in composition will affect the system over longer timescales. Management decisions in the uplands encompass complex trade-offs between production, biodiversity and a range of ecosystem services. Predicting the consequences of decisions is difficult given the slow dynamics of unproductive habitats.

Diverse Swards and Mixed-Grazing of Cattle and Sheep for Improved Productivity

“…This was also confirmed for belowground biomass (Rose et al, 2013) and is in line with the present results. Besides provision of forage for livestock, extensive management of diverse grasslands also contributes to the conservation of many species (Everwand et al, 2014;Pakeman et al, 2018). In addition, mixed low-intensity grazing was shown to offer good opportunities for butterflies (Fraser et al, 2014) and vertebrates (Evans et al, 2015) and this should be taken into account when evaluating the performance, in terms of ecosystem services, of such systems.…”

“…Grassland offers great potential for biodiversity conservation, subject to it being managed in a suitable way (Pavlu et al, 2006). There are, however, ongoing threats of grassland abandonment in many marginal areas in regions of Europe (Pakeman et al, 2018), and mixed-grazing of diverse swards offers potential opportunities for a more sustainable maintenance of ecosystem services of grasslands, including both biodiversity conservation and utilized agricultural production. Therefore, in this study, we designed a two-factorial experiment with two different sward types ("diverse-" and "grass-dominated") and three grazing treatments (cattle and sheep in mono-and mixed-grazing) analyzed over five successive years.…”

Livestock grazing impacts components of the breeding productivity of a common upland insectivorous passerine: Results from a long‐term experiment

“…To examine the influence of the initial vegetation community on pipit breeding output, vegetation was sampled prior to the set up of fences and experiment treatments in 2002. The vegetation communities were sampled by measuring cover of each plant species as the number of hits within a pin-frame at 25 locations per plot in late July to early August (Pakeman et al, 2019). We then measured vegetation height during each year of the bird surveys as the first hit of a sward stick at 50 points per plot between 10 May and 4 June.…”

“…Given the association of meadow pipits with habitat mosaics (Douglas et al, 2008;, we hypothesized that positive effects of the low-intensity treatments (Low and Table S2). Therefore, other factors such as weather and predation pressure unrelated to grazing treatments may contribute to a larger proportion of the variation in breeding success (see 'Long-term regional changes' below), but see Ibáñez-Álamo et al 2015 Moreover, it took a minimum of 6, and sometimes 12 or 15 years for individual plant species to show a different response to grazing treatments (Pakeman et al, 2019). This suggests that changes in plant composition would not yet have been apparent in [2003][2004].…”

“…However, both studies investigated shortterm bird responses in the first few years after the experiments had commenced. Land management change can take several decades, or longer, to reach their full effects on plant composition (Pakeman, Fielding, Everts, & Littlewood, 2019) and to have potential knock-on effects on other taxa across trophic levels. Yet to our knowledge, no experimentally managed grazing study has examined the long-term effects of grazing management on avian breeding success, largely due to the logistical and financial constraints of maintaining such experiments at large spatial scales.…”