Groupings of life-history traits are associated with distribution of forest plant species in a fragmented landscape

Abstract

Questions: 1. Do relationships among forest plant traits correspond to dispersability-persistence trade-offs or other inter-trait correlations found in the literature? 2. Do species groups delineated by trait similarity, differ in occurrence in ancient vs. new forests or isolated vs more continuous forest patches? 3. Are these patterns consistent for different forest types? Location: Central Belgium, near Leuven. Methods: We investigate the distributions of a large set of plant traits and combinations among all forest species occurring in patches with varying forest continuity and isolation. Through calculation of Gower's similarity index and subsequent clustering,‘emergent’ species groups are delineated. Then, the relative occurrence of these different groups in forest patches of different age and size, sustaining different forest types (alluvial vs. Quercion), and having different isolation status is compared through multivariate GLM analysis. Results: Correlations among several life history traits point towards trade-offs of dispersability and fecundity vs. longevity. We distinguished three species groups: 1= mainly shrubs or climbers with fleshy or wind dispersed fruits and high dispersal potential; 2 = dominated by small, mainly vegetatively reproducing herbs; 3 = with spring flowering herbs with large seeds and mainly unassisted dispersal. Relative occurrence of these groups was significantly affected by forest age, area, isolation and forest type. Separate analyses for alluvial and Quercion forests indicated that the relative importance of these factors may differ, depending on forest type and species group. Both forest continuity and isolation are important in restricting the relative occurrence of forest species in alluvial forests, whatever their group membership. In Quercion forests forest patch area was the primary determinant of relative occurrence of species groups. Conclusions: It is very important to preserve the actual forest area including the spatial setting and the dispersal infrastructure within the landscape. Next, forest connectivity may be restored, but it is inherently a long process.