Volume 191, November 2015, Pages 1–9
- Biogeography and Geomatics, Department of Physical Geography, Stockholm University, 106 91Stockholm, Sweden
- Received 24 February 2015, Revised 25 May 2015, Accepted 4 June 2015, Available online 23 June 2015
Highlights
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- We investigated plant diversity along a tree density gradient in woody pastures.
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- Plant gamma and beta diversity increased continuously along the gradient.
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- Tree density had no significant effect on alpha diversity.
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- Number of grassland specialist species remained indifferent along the gradient.
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- The CAP tree limit regulation needs to be scrutinised to preserve biodiversity.
Abstract
A
vast majority of European farmers are dependent on EU subsidies, which
makes subsidy regulations through the Common Agricultural Policy (CAP)
powerful tools in shaping agricultural landscapes. Unfortunately,
steering recommendations are sometimes arbitrary, like in the case of
pasture management, where 50 trees per hectare constitute an upper limit
to qualify for subsidies. Although pasture biodiversity is well studied
and the core of many CAP conservation programmes, it is seldom studied
as direct effects of subsidy systems. In this paper, we examine plant
diversity in relation to the impact of subsidy systems in Swedish woody
pastures along a gradient from 3 to 214 trees per hectare. We selected
64 sites where we recorded vascular plants, soil properties and canopy
cover. We found a general increase in γ- and β-diversity along the
gradient, whereas α-diversity and the number of grassland specialists
remained indifferent along the gradient. Additionally, tree density,
organic content and C:N-ratio were the strongest predictors of species
composition. Hence, when CAP regulations encourage tree cutting for
pastures to qualify for subsidies there is risk of homogenisation of EU
grasslands, leading to decreased γ- and β-diversity. If a general target
for the subsidies is to increase biodiversity, there is need to
scrutinise these regulation details to preserve the high values of woody
pastures. We argue that habitat variation, species diversity and low
intensity management, rather than a specific number of trees, should be
the main incentives for financial support to preserve biodiversity.
Abbreviations
- CAP, Common Agricultural Policy;
- EIV-L, Ellenberg Indicator Value for Light;
- EIV-N, Ellenberg Indicator Value for Nitrogen;
- NE, not eligible;
- SBA, Swedish Board of Agriculture
Keywords
- CAP;
- Diversity;
- European Union;
- Plant;
- Tree density
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