Using results from a long-term experiment at Glen Finglas in Scotland, Robin Pakeman and colleagues show that even substantial changes in grazing management take many years to play out, so forecasting change in the uplands is difficult. Here Robin explains more about their work.
We set up the Glen Finglas experiment in 2002 to look at how changes to the European Common Agricultural Policy, specifically decoupling of support from livestock numbers, might impact upland biodiversity. We were interested in how changes in grazing might cascade through a system from the direct impacts of the grazers on the plants to indirect impacts on other parts of the system (invertebrates, birds and voles).
Since then the team has published on meadow pipits, bugs, moth and voles, to name a few groups. However, 15 years after the start of the experiment, we are publishing the first paper on the vegetation.
The Glen Finglas Experiment
Glen Finglas sits at the southern edge of the Scottish Highlands. We established the experiment on a mixture of uplands habitats: wet heath, wet and dry grassland of varying quality and sedge mire. This mosaic nature of the experiment meant that heterogeneity had to be taken into account in the analysis, and this showed insights into the dynamics of the different vegetation types. Because we were interested in the impacts of grazing on the birds, plots had to be big enough to have multiple territories of the most common breeding bird – the meadow pipits. Plots would be 180 m x 180 m (3.3 ha) if square plots were possible on this hilly terrain. Four grazing treatments have been followed: continued low density sheep (0.9 sheep ha-1), high sheep (2.7 sheep ha-1), mixed cattle and sheep with the same offtake as the continued treatment, and no grazing.
The responses of individual species took a minimum of 12 years and often 15 years to become apparent, with some species showing no detectable changes. Some vegetation types responded quickly to the removal of grazing, including the relatively unproductive wet heath and mat grass dominated grassland, indicating that these had species capable of responding to the removal of grazing such as heather. More productive grasslands, such as those dominated by bents and fescues, which are the usual focus of grazing in these habitats appear to have lost these species and so their response to grazing removal was minimal. Tree invasion was minimal apart from one no grazing plot near a wooded ravine.
The vegetation types that responded fasted to increased grazing were the moderately productive purple-moor grass and sedge mires, indicating a broadening of the foraging of the sheep to from their more preferred bent and fescue grassland. Increased grazing also resulted in greater alpha diversity.
Partial replacement of sheep by cattle had little impact on the vegetation, though there were negative impacts for bracken and blaeberry (Vaccinium myrtillus – a species with many common names), and small increases for plant diversity.
Management change in the upland margins will be driven by changes in policy, agricultural support payments and farm profitability. Different species will benefit under different management regimes and big changes are possible if grazing removal results in woodland regeneration. Animal species and assemblages reacted quickly to changes in structure, we are working on how further changes are driven by the slow changes in plant composition and quality.
Read the full article, Long‐term impacts of changed grazing regimes on the vegetation of heterogeneous upland grasslands, in Journal of Applied Ecology.
The full article, Long-term impacts of changed grazing regimes on the vegetation of heterogeneous upland grasslands, is available in Journal of Applied Ecology
The published study is part of a long-term project funded by the Scottish Government’s Rural and Environment Science and Analytical Services as part of their Strategic Research Programme. Many thanks to the Woodland Trust, our generous and helpful landlords.