Relative Importance of Current and Past Landscape Structure and Local Habitat Conditions for Plant Species Richness in Dry Grassland-Like Forest Openings

Abstract

In fragmented landscapes, plant species richness may depend not only on local habitat conditions but also on landscape structure. In addition, both present and past landscape structure may be important for species richness. There are, however, only a few studies that have investigated the relative importance of all of these factors. The aim of this study was to examine the effect of current and past landscape structures and habitat conditions on species richness at dry grassland-like forest openings in a forested landscape and to assess their relative importance for species richness. We analyzed information on past and present landscape structures using aerial photographs from 1938, 1973, 1988, 2000 and 2007. We calculated the area of each locality and its isolation in the present and in the past and the continuity of localities in GIS. At each locality, we recorded all vascular plant species (296 species in 110 forest openings) and information on abiotic conditions of the localities. We found that the current species richness of the forest openings was significantly determined by local habitat conditions as well as by landscape structure in the present and in the past. The highest species richness was observed on larger and more heterogeneous localities with rocks and shallow soils, which were already large and well connected to other localities in 1938. The changes in the landscape structure in the past can thus have strong effects on current species richness. Future studies attempting to understand determinants of species diversity in fragmented landscapes should also include data on past landscape structure, as it may in fact be more important than the present structure.

The effect of current and historical landscape structure and species life‐history traits on species distribution in dry grassland‐like forest openings

“…Approximately 2% of the area is occupied by dry grassland‐like forest openings, with a mean area of 635 m 2 and a mean nearest distance between localities of 48 m (estimated as the distance between nearest points on the borders of neighbouring localities). From a previous study carried out in the same study region (Husáková & Münzbergová ), we obtained data on the distribution of 110 dry grassland‐like forest openings in total, with areas ranging from 20 m 2 to 11 123 m 2 . These localities represented all dry grassland‐like forest openings mapped in the study region, defined as open localities with <30% tree cover that are isolated from other localities by at least 20 m of forest.…”

“…These localities represented all dry grassland‐like forest openings mapped in the study region, defined as open localities with <30% tree cover that are isolated from other localities by at least 20 m of forest. The border between the grassland and the forest was always abrupt, without a transition zone, and it was created by the trunks of trees (Husáková & Münzbergová ).…”

“…To study the effects of isolation and habitat size on species composition, it was absolutely crucial to use only species for which the forest openings are the only possible habitat in the area. To exclude species occurring also in the surrounding forests from the analyses, we generated a list of species growing both in the study localities and in the surrounding forests in the study region (as in Husáková & Münzbergová ). In this way, we excluded 34% of the 296 species recorded at the studied localities (Appendix S2).…”

“…To assess historical and current landscape structures we used the data obtained in our previous study (Husáková & Münzbergová ). We used aerial photographs of the study region from 1938, 1973, 1988 and 2000 available from Geoportal Cenia (http://geoportal.cenia.cz).…”

“…In this area, the dry grassland‐like forest openings are the places with the highest species richness of plants and animals, and are thus places of high conservation interest. During the last century, these places experienced several changes in landscape structure (Husáková & Münzbergová ). To identify the determinants of plant species composition in this landscape we asked the following questions: (1) what is the importance of current and historical landscape structures for plant species composition in dry grassland‐like forest openings in forest matrix; and (2) which life‐history traits explain the response of species to current and past landscape structure?…”