LOWLAND WOODLAND STRUCTURE AND PATTERN AND THE DISTRIBUTION OF ARBOREAL, PHYTOPHAGOUS ARTHROPODS

We investigated factors that limited the distribution of phytophagous species within a woodland system in Midlothian, Scotland. A pattern an alysis was conducted of phytophagous species on a total of 45 Fagus sy lvatica within 15 woodlands. Species richness counted on collected lea ves was tested against within- and between-wood variables. Variables u sed in a regression with arthropod data from Fagus were used to estima te the phytophage richness on Betula pendula and Quercus robur in the same woods. Covariance in the number of phytophages in sampled woods w as found for Fagus over three years and for Fagus, Betula and Quercus in 1992. Association analysis was used to classify the woods into spec ies rich or poor based on presence or absence matrices. The main facto rs that limit phytophages on Fagus (gaps along the woodland edge, dept h and species richness of the field layer, density of leaf litter and the extent of contiguous woodland cover, when including hedgerows and lines of trees) affect phytophages of similar life history strategy on other tree species within the same woods. Eighty-six per cent of spec ies were lost because certain life history stages were vulnerable to f actors that prevail in woods of poor structure. The nature conservatio n value of woodlands could be assessed using the correlated vulnerabil ity of particular phytophages across tree species under specific woodl and conditions.