Measuring the success of calcareous grassland restoration : a practical test of ecological theory

The calcareous grassland ecosystem is highly biodiverse. It is semi-natural, having been created and maintained by the farming of livestock iri a traditional, non-intensive manner. During the last 60 years, with the increasing intensification of farming, its extent has declined dramatically, and consequently many of the flora and fauna that comprise it are now endangered. Since the early 1990s substantial efforts have been made to restore ex-arable land to species-rich calcareous grassland, but there is little evidence that the target ecosystem can be obtained by the restoration techniques and management practices currently used. My primary interests were to assess the efforts currently underway, and to identify any areas in which improvements could be made. This called for an approach which centred on several large-scale surveys (since it has been previously shown that a timescale of at least several decades is needed for grassland restoration on ex-arable land) combined with a number of experimental studies in order to limit variation under controlled conditions. The large-scale surveys involved 40 restoration sites, representing a range of restoration ages and management practices, paired with 40 nearby ancient calcareous grasslands. At these sites vegetation, seed bank, and ant communities were measured, and measures of site isolation and soil chemistry made. At a smaller range of sites, soil bacterial communities were investigated through molecular means. Pot experiments were used to measure the effects of different arbuscular mycorrhizal fungi (AMF) communities and soil fertility on the growth of, and competition between, specialist calcareous grassland and early-successional plant species. Through the multivariate analysis of 40 pairs of sites, it was found that restoration appears to be moving in the right direction, although 60 years did not appear to be long enough for complete success. A high soil phosphorus concentration, or high phosphorus/nitrogen ratio was particularly detrimental to the restoration of the vegetation and seed bank communities, as was the isolation of sites, due in no small part to the increased competition faced by calcareous grassland species from early successional species under these conditions. More controversial was the evidence that seeding of restoration sites can prevent restoration proceeding, particularly where seed mixes used were of low diversity. The ant communities were not sensitive enough to record all of these effects, but MY17llica sabuleti was found to be a useful representative of the invertebrate taxa for indicating restoration success. Bacterial communities from long-term restoration sites appeared more similar to those of recently abandoned arable land than those of the target sites, although how much of a problem this may be to restoration success requires further investigation at a finer level of resolution. Different AMF communities were found not to influence plant growth in this instance, but a more comprehensive investigation should be a priority for future research. These results provided further insights into ecological theory and also gave rise to several practical recommendations.EThOS - Electronic Theses Online ServiceGBUnited Kingdo