S. Mcintyre et S. Lavorel, PREDICTING RICHNESS OF NATIVE, RARE, AND EXOTIC PLANTS IN RESPONSE TOHABITAT AND DISTURBANCE VARIABLES ACROSS A VARIEGATED LANDSCAPE, Conservation biology, 8(2), 1994, pp. 521-531
Species richness o native, rare native, and exotic understorey plants
was recorded at 120 sites in temperate grassy vegetation in New South
Wales. Linear models were used to predict the effects of environment a
nd disturbance on the richness of each of these groups. Total native s
pecies and rare native species showed similar responses, with richness
declining on sites of increasing natural fertility of parent material
as well as declining under conditions of water enrichment (resulting
from human-induced changes in drainage characteristics, leading to inc
reased run-off), severe livestock grazing, and soil disturbance. The r
esponse of rare native species to water enrichment however, was signif
icantly greater than that of all native species. Exotic species richne
ss varied in reverse to that of native species with positive responses
to water enrichment and soil disturbance, The contrasting behaviors a
re attributed to differences in the evolutionary history of native and
exotic assemblages and their resulting preadaptations to a landscape
recently subjected to agricultural settlement It would appear that for
exogenous disturbances, the intermediate disturbance hypothesis is no
t supported by our data In the sampled region, pastures represent the
major land-use in terms of area, but have relatively low densities of
native and rare species compared with more lightly grazed areas. Howev
er, their management is considered to be essential to the maintenance
of diversity on a regional scale.