Identifying indicators of atmospheric nitrogen deposition impacts in acid grasslands
نویسنده
چکیده
Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online's data policy on reuse of materials please consult the policies page. Abstract: Atmospheric deposition of nitrogen has become a serious concern for 25 nature conservation managers and policy makers. It has the potential to reduce 26 species richness, increase the graminoid component of the sward, encourage species 27 typical of more fertile conditions and alter the soil biogeochemistry of grasslands. 28 Calcifugous grasslands (grasslands found on acid soils) are among the most sensitive 29 to N deposition due to their poorly buffered soils and species typical of nutrient poor 30 environments. 31 Indicators have an important role to play in detecting the impact of nitrogen 32 deposition on sites of conservation importance and assessing conservation status. 33 This study investigates potential indicators of nitrogen deposition impacts that could 34 be incorporated into site-condition monitoring programmes such as the UK Common 35 Standards Monitoring. 36 Using two national surveys of calcifugous grasslands we examined the potential for 37 using: the presence or absence of indicator species, the cover of indicator species, the 38 species richness and richness of functional groups, and the cover of functional groups 39 as indicators of N deposition impacts. Of all the potential indicators investigated, 40 graminoid:forb ratio was found to be the best indicator of N deposition impacts. It 41 showed a significant relationship to N deposition in both data sets and is quick and 42 easy to assess in the field. Vegetation indicators must be used with caution as there is 43 potential for vegetation management regime and nutrients from other sources to cause 44 similar changes in species composition. Consideration must be given to these before 45 attributing changes to nitrogen deposition. 46 47
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