Historical Factors Affecting the Number and Distribution of Vascular Plant Species in the Woodlands of Central Lincolnshire

Abstract

(1) The number of woodland vascular plant species in eighty-nine ancient woods and 273 recent woods in central Lincolnshire was recorded. Ancient woods were identified from historical and archaeological sources. (2) In both ancient and recent woods the number of species increased with area, probably because of a correlated increase in habitat diversity. (3) The number of species present in part of an ancient wood was not significantly different from the number present in whole ancient woods of equivalent area. (4) The number of species present in recently reduced ancient woods was not significantly different from the number present in ancient woods which were reduced to their present size long ago. This result was also obtained for 'ancient woodland species' and 'recent woodland species' (see (10) below) considered separately. (5) The number of species present in ancient woods was not related to the proportion of the area planted with conifers. (6) Ancient woods were significantly richer than isolated recent woods, i.e. those which have never had a physical contact with an ancient wood. This relationship is true for all but one part of the study area. (7) Recent woods which have had a physical contact with an ancient wood were significantly richer in species than isolated recent woods, and significantly poorer than ancient woods. (8) The number of species present in recent woods did not increase with age. This was tested in woods originating between 1600 and 1947. (9) In so far as it could be tested, the number of species present in recent woods was influenced by habitat diversity. Previous land use influenced which species were present, not how many. (10) Species varied in their bias to ancient or recent woods. Although ancient woods comprised only 25% of all sites (43% by area), sixty-two of the 174 species recorded had over 50% of their localities in ancient woods (= ancient woodland species) and forty-three species had less than 33% of their localities in ancient woods (= recent woodland species). (11) The bias of some species to ancient or recent woods varied from one part of the study area to another. (12) Recent woodland species tended to inhabit disturbed parts of ancient woods, whereas ancient woodland species tended to inhabit undisturbed parts. (13) The influence of isolation, habitat diversity and woodland history on the woodland flora is discussed. The implications of these findings for nature conservation are summarized.