Jeanette Hall

A comparison of the resilience of four habitats to fire, and the implications of changes in community composition for conservation: a case study from the Serra de Monchique, Portugal

Background: The occurrence of fire is natural in many ecosystems but recently the number and frequency of fires has increased. Aim: To provide an assessment of the resilience of four habitats in the Serra de Monchique to fire and to assess the implications of changes in community composition for conservation. Methods: Plots were established in heathland, rhododendron scrub, rocky outcrops and woodland and the vegetation recorded pre-fire and two and four years post-fire. A one-off survey of a range of heathland plots with different fire history was also conducted. Results: The rarer habitats (rhododendron scrub, woodland and rocky outcrops) were less resilient to fire than the more abundant heathland habitat. Fire caused an increase in the cover and number of therophyte and hemicryptophyte species, and the more typical dominant species failed to reach their natural cover. In the heathlands Erica australis (an indicator species for the ‘dry heathland’ habitat of European community interest) increased and Cistus salvifolius and Ulex minor decreased in cover with time since fire. Conclusions: The rarer habitats were least resilient to fire, which is of considerable conservation importance since fire frequency is predicted to increase with climate change. Higher fire frequencies caused a change towards a less valuable heathland type.

Extending the natural range of a declining species: genetic evidence for native great crested newt (Triturus cristatus) populations in the Scottish Highlands

Determining whether isolated populations of a species are native or introduced is important for conservation, as non-native occurrences are likely to be of lower priority for conservation organisations with limited resources. The great crested newt Triturus cristatus is an important wetland flagship species in the UK, and recent evidence suggested that putatively introduced isolated occurrences around Inverness (Scottish Highlands) might be of native origin. Here, we use six microsatellite loci and mtDNA sequence information (ND4 region) to genetically characterise eight Highland populations, comparing them with two populations from central Scotland (the northern limit of the species’ continuous UK distribution) and central England (Leicestershire). Highland populations were characterised by low amounts of genetic variation at high degrees of differentiation, which can be best interpreted by demographic instability and isolation at the periphery of the species’ range. We found no evidence for population bottlenecks in the last decades. All studied individuals possessed a single mtDNA haplotype previously described for British T. cristatus. Taken together, these results suggest that T. cristatus is native to the Scottish Highlands, with important implications for its local conservation status.

Overall biodiversity and the spatial patterns of atlantic oakwoods

Summary Maintenance of biodiversity in these complex woodlands, that have been historically much altered, is based on actions promoting conservation of existing values but which may also prepare them for future changes, such as a decline in the dominance of oak in the canopy. Site condition monitoring of the 9000 ha of Atlantic oakwoods already designated indicates damage from excessive browsing, invading species and lack of deadwood. These conditions and potential hazards from climate change are being addressed by attempting to expand and interconnect existing woodlands to reduce fragmentation and increase possibilities for species to migrate.

Habitat requirements and conservation needs of peripheral populations : the case of the great crested newt (Triturus cristatus) in the Scottish Highlands

Edge populations are of conservation importance because of their roles as reservoirs of evolutionary potential and in understanding a given species’ ecological needs. Mainly due to loss of aquatic breeding sites, the great crested newt Triturus cristatus is amongst the fastest declining amphibian species in Europe. Focusing on the north-westerly limit of the T. cristatus range, in the Scottish Highlands, we aimed to characterise habitat requirements and conservation needs of an isolated set of edge populations. We recorded 129 breeding pond-related environmental parameters, and used a variable selection procedure followed by random forest analysis to build a predictive model for the species’ present occurrence, as well as for population persistence incorporating data on population losses. The most important variables predicting T. cristatus occurrence and persistence were associated with pond quality, pond shore and surrounding terrestrial habitat (especially mixed Pinus sylvestris–Betula woodland), and differed from those identified in the species’ core range. We propose that habitat management and pond creation should focus on the locally most favourable habitat characteristics to improve the conservation status and resilience of populations. This collaborative work, between conservation agencies and scientific researchers, is presented as an illustrative example of linking research, management and conservation.

Invasion by Rhododendron ponticum depletes the native seed bank with long-term impacts after its removal

The soil seed bank plays an important role in determining what plant species emerge following the removal of monodominant invasive species. A depleted seed bank may provide a substantial barrier to site restoration, however, little is known about what changes occur in the seed bank during invasion and following clearance. This study used greenhouse germination trials to quantify and compare the seed bank present in 30 Scottish Atlantic oak woodland sites under three treatments: (1) sites featuring dense stands of the non-native invasive shrub Rhododendron ponticum; (2) sites that had been previously subject to dense R. ponticum stands but which had been cleared; and (3) uninvaded control sites. Seed banks of densely invaded and cleared sites had significantly lower species richness than those of uninvaded control sites with a lower abundance of graminoid, and to a lesser extent forb seeds than the uninvaded controls. The seed bank community composition differed significantly between the three site types. Uninvaded sites featured a wide array of species, densely invaded sites were dominated by R. ponticum seeds and cleared sites were dominated by birch (Betula sp.) seeds. Cleared sites contained very few R. ponticum seeds indicating that once effective clearance had been achieved, re-invasion would be unlikely to occur from the soil seed bank. Our findings revealed that the soil seed bank present in cleared sites was very different from the seed bank of uninvaded control sites, with clear implications for site restoration.

Testing the validity of a commonly-used habitat suitability index at the edge of a species’ range: great crested newt Triturus cristatus in Scotland

Habitat Suitability Indices (HSI) are widely used in conservation and in pre-development surveying. We tested a commonly-used HSI to assess its effectiveness at predicting the presence of a European protected species, the great crested newt Triturus cristatus , at the edge of its range. This HSI is used to understand species’ conservation needs, and in assessing the need for, and designing, mitigation. Given the cost of surveying to developers, it is essential that they can have confidence in the index used in targeting work and in Environmental Impact Assessments. We found that nine of the ten factors which make up the HSI are robust in the region, even in a disjunct population believed to have been isolated for around 3000 years. However, we propose modification of the geographic factor, based upon an improved knowledge of the species’ distribution since the HSI was originally devised.