Monika Wulf, Jens Kolk

• Questions: (i) Is plant species richness related to patch configuration, quality, heterogeneity and history in very small forest patches? (ii) Is there a similar effect of patch configuration, quality, heterogeneity and history on all plant species or does it vary for different plant groups? (iii) Does the importance of patch configuration, quality, heterogeneity and history vary for plant species richness between patch size classes? Location: Prignitz region, western part of Brandenburg, Germany Methods: Plant species lists for 183 forest patches (0.08-12.7 ha) were compiled. We conducted a hierarchical partitioning analysis to test which of the four patch variables - configuration, quality, heterogeneity and history - explained most of the variance in plant species richness and richness of various plant groups. Results: Irrespective of patch size class, species richness is mainly predicted by patch quality and heterogeneity. In particular, generalists are primarily affected by the soil moisture and nutrient level, and specialistsQuestions: (i) Is plant species richness related to patch configuration, quality, heterogeneity and history in very small forest patches? (ii) Is there a similar effect of patch configuration, quality, heterogeneity and history on all plant species or does it vary for different plant groups? (iii) Does the importance of patch configuration, quality, heterogeneity and history vary for plant species richness between patch size classes? Location: Prignitz region, western part of Brandenburg, Germany Methods: Plant species lists for 183 forest patches (0.08-12.7 ha) were compiled. We conducted a hierarchical partitioning analysis to test which of the four patch variables - configuration, quality, heterogeneity and history - explained most of the variance in plant species richness and richness of various plant groups. Results: Irrespective of patch size class, species richness is mainly predicted by patch quality and heterogeneity. In particular, generalists are primarily affected by the soil moisture and nutrient level, and specialists additionally by patch heterogeneity and history. A higher historical habitat quality, together with long habitat continuity, led to an increase in forest specialists and geophytes in all patches. In the >5-ha patches only historical habitat quality accounted for a significant increase in the number of species with short-distance dispersal capacity in all species. Regardless of patch size, the number of locally infrequent species increased significantly with historical habitat quality. The effect of patch configuration was negligible, except for space-filling trees and shrubs, when considering all patches. Conclusions: Our more comprehensive statistical approach shows, in general, that all complex variables have an effect on species richness and should be considered in future studies. The fact that patch heterogeneity and quality are the main predictors of species richness indicates that very small forest patches covered a range of highly structured patches and sites having various growth conditions. We assume that the century-old tradition of private ownership with smallholder social structure is the main reason for variability in stand structure and species assemblage, resulting in the uniqueness of each patch. Since the number of locally infrequent plant species increases significantly with historical habitat quality, we suggest that it is particularly important to consider this variable in future studies on the decline of infrequent plant species.…