Ecological aspects of nature reserve management at St. Cyrus National Nature Reserve
(1) The major aim of this work was to provide a scientific basis for the management of St. Cyrus National Nature Reserve. The Nature Reserve itself consists of cliffs, sand-dunes and a salt-marsh. Most of the research was focussed on the latter two. The approach to the research was partly descriptive, partly experimental. (2) A description of the salt-marsh and sand-dune vegetation was obtained by means of classification and photointerpretation. The landform changes around the N. Esk estuary were mapped from aerial photographs (maps 1a and b). Six communities were described and mapped from the salt-marsh: a Festuca rubra-community, a Juncus gerardii-community, a Scirpus maritimus-community, a Relict Puccinellia or tall herb-grassland community and an open and closed Elymus-Ammophila -community on deposited sand (map 2). These communities were ranked into the Braun-Blanquet phytosociological classification system. The distribution of the surviving salt-marsh flora was mapped (map 3) and its distribution related to environmental conditions. The successional development since 1951 was related to the decrease in flooding frequency, a consequence of the landform changes in the area; most affected by the desalination and desiccation processes was the former Puccinelietum maritimae which developed into the tall herb-grassland or Relict Puccinellia-community, characterised by pasture and ruderal species. The future development of the salt-marsh vegetation largely depends on the dynamic processes around the N. Esk estuary. (3) A polythetic divisive classification method, TWINSPAN, led to the identification of the sand dune communities. The following sequence of communities was described (map 4): foreshore colonisation, mobile Ammophila-dune, Ammophila-dune in its stabilising and early stages of fixation, tall Arrhenatherum-grassland and grazed dune pasture. The last stage of the successional series is represented by dune scrub dominated by Ulex europaeus. The lichen-rich grey dune community, an anomaly in the present series, probably represents a deflection of the successional trends. The most important trends observed since 1951 were the stabilisation and fixation of the Ammophila-dunes, the development of tall Arrhenatherum-grassland and Ulex-scrub. The decrease in rabbit numbers after the advent of the myxomatosis in 1954 was partly responsible for these changes. (4) The effect of the removal of the rabbit grazing factor was assessed from rabbit-proof exclosures. Principal Components Analysis proved to be an effective means of detecting time-related trends in the vegetation. The exclusion of rabbits from the grazed dune pasture led to the development of taller vegetation, a significant increase in the cover of Festuca rubra and a small but significant decrease in species richness. Excluding rabbits from the grey dunes resulted in a decrease of annual species. A more detailed study of the grey dunes revealed that the variation in this community was related to the disturbance by man and/or rabbits. (5) About 18 km of paths, and tracks, were mapped from the Nature Reserve (map 5). This included 3 km of tractor tracks created by the fishermen. The remaining 15 km represented footpaths and old tracks. Nearly all of these paths and tracks were concentrated in the dunes which had a path, density of 739 m/ha. A general description of the vegetation and the amount of erosion revealed weak points in the dune system. Vegetation recovery on a footpath in the dunes took approximately two years. Camping on the dune pasture appears to favour a particular assemblage of species. Removal of camping pressures had initially little effect on the dune pasture vegetation. (6) Experimental burning of a part of the Arrhenatherum-grassland was followed by a rapid recovery of the dominants during the first season after the fire. Recolonisation by mosses started in the second season after the fire. Complete recovery of the vegetation is to be expected three or four years after the burning. Fire also appeared to have a rejuvenating effect on Ammophiia arenaria. (7) Bracken and gorse have been invading the dune pasture to the detriment of its attractive and rich flora. Experimental control of bracken with the herbicide asulam demonstrated that spraying with asulam was a safe method for controlling bracken on the Nature Reserve. Application of asulam at the recommended rate of 4.4kg active ingredient per ha resulted in an average reduction of bracken of 79% in the first year after treatment and 58% reduction in the second year after treatment. In the second year after treatment an increase in the cover of Arrhenatherum elatius and a decrease in the cover of bracken litter were observed. The rate of spread of gorse was estimated from maps made from aerial photographs and appeared to be exponential. Gorse-cleared sites in the Arrhenatherum-grassland and dune pasture were recolonised mainly by vigorous Holcus lanatus.