VARIATION IN THE UPLAND HEATHLANDS OF GREAT-BRITAIN - CONSERVATION IMPORTANCE

The two main communities of British upland heaths are heather Calluna vulgaris moor and heather-dominated blanket bog, which occur towards d ry and wet ends, respectively, of a climatic gradient. The four develo pmental phases of heather-pioneer, building, mature and degenerate-als o contribute to the variability, particularly for animal species. Spat ial variation in the invertebrates often reflects these primary determ inants of ecological variation, although soil or geological difference s can be important. Temporal variation relates to the succession after heather burning or cutting. Examples of spatial and temporal variatio n are drawn from studies on the North York Moors, an upland area with 15% of British ground beetles Carabidae, 20% of British spiders Aranea e, but only 2.2% of the British vascular plants. There are many fewer species of vertebrates on upland heaths, but for the breeding birds (1 5% of British species), three questions are discussed in detail-what i s desired, what management options are available and can heath-lands b e managed for assemblages as well as for individual species? The revie w concludes that (i) burning on blanket bog be minimised; (ii) variabl e burning cycles to improve habitat complexity be used; (iii) wet flus hes be conserved; (iv) upland heathland margins be burnt less intensiv ely; and (v) scattered mosaics of scrub and woodland be established Th e mosaic structure of upland heathlands is critical for wildlife conse rvation. The invertebrate assemblages rely for their diversity on this mosaic structure. Several scales of mosaic on any one moor are likely to lead to the greatest diversity of vertebrate species.