Influence of tree health on ground flora in the Chiltern Beechwoods, England

The aim of this study was to investigate whether changes in crown condition associated with decline in the health of beech (Fagus sylvatica) stands ar e affecting the species composition of the woodland ground flora. Forty-thr ee woods in the Chilterns region of south-east England were surveyed in the summer of 1989, In each wood, two sample plots (30 m x 30 m) were chosen o n the basis of the relative health of their trees (i.e. one 'healthy' plot and one 'unhealthy' plot). The percentage cover of all species of ground fl ora was recorded for each plot. Stand, soil and site characteristics were a lso recorded. Data were analyzed using detrended correspondence analysis (D CA). The resulting axis scores were compared for healthy and unhealthy plot s using paired t tests, and relationships between the axes and environmenta l variables were explored using correlation analysis. A significant differe nce was found in the ground Bora under healthy and unhealthy trees on calca reous soils, using an axis which was determined by the light requirements o f the plants. No other environmental or stand variable explained this diffe rence. In plots with lower tree crown density, the ground flora comprised s pecies more typical of clearings, rides and woodland margins, at the expens e of more typical woodland species. This finding is important given evidenc e of declines in tree health in the Chilterns and elsewhere in Europe over the past decade. (C) 1999 Elsevier Science B.V. All rights reserved.