Effects of landscape structure and patch characteristics on the density
of central populations of the eastern green lizard Lacerta
viridis
Abstract
A better understanding of the impact of habitat loss on population
density can be achieved by evaluating effects of both, parameters within
remnant habitat patches and parameters of the landscape surrounding
those patches. The integration of predictors at the patch and landscape
level is scarce in animal ecological studies, especially for reptiles.
In this study, a patch-landscape approach was applied to evaluate the
combined effects of within patch habitat quality, patch geometry and
landscape configuration and composition on the density of remnant
populations of the eastern green lizard, Lacerta viridis, in a
highly modified landscape in Bulgaria. Landscape composition variables
(proportion of different land covers) were measured at different spatial
scales surrounding patches. Single scale models were built to evaluate
combined effects of all predictors on density, when including all
landscape composition variables at a specific spatial scale. Multiscale
models were applied to analyze combined effects when including landscape
composition variables at the scale of their strongest effect (scale of
effect, SoE). Results showed that the SoE of proportion of cropland and
urban areas was small (50 m), while for proportion of habitat was large
(1.5 Km). The overall effect of habitat loss was better explained by the
multiscale model. Population density increased with patch area and
decreased with patch shape irregularity and with the proportion of three
land cover types surrounding patches -cropland, urban areas and habitat.
Combining patch and landscape parameters is important to identify
ecological processes that occur simultaneously at different spatial
levels and landscape scales, and which would imply the application of
multiscale approaches for the protection of wild animal populations.
Results are contrasted with what is known about occupancy patterns of
the species in the same region, and approaches to integrate both,
occupancy and density, in the field design of animal ecological studies
are suggested.