Search

Succession is a key ecological process that supports our understanding of community assembly and biotic interactions. Dispersal potential and dispersal strategies, such as wind- or animal-dispersal, have been assumed to be highly relevant for the success of plant species during succession. However, research yielded varying results on changes in dispersal modes between successional stages. Here, we test the hypotheses that (a) vascular plant species that use a number of dispersal modes dominate in early stages of succession while species specialized on one/few dispersal modes increase in abundance towards later stages of succession; (b) species well adapted to wind-dispersal (anemochory) will peak in abundance in early successional stages and (c) species well adapted to adhesive dispersal (epizoochory) will increase with proceeding succession. We test these hypotheses in four sites within agriculturally dominated landscapes in Germany. Agricultural use in these sites was abandoned 20–28 years ago, leaving them to secondary succession. Sites have been monitored for plant biodiversity ever since. We analyze changes in plant species richness and abundance, number of dispersal modes and two ranking indices for wind- and adhesive dispersal by applying generalized linear mixed-effect models. We used both abundance-weighted and unweighted dispersal traits in order to gain a comprehensive picture of successional developments. Hypothesis (a) was supported by unweighted but not abundance-weighted data. Anemochory showed no consistent changes across sites. In contrast, epizoochory (especially when not weighted by abundance) turned out to be an indicator of the transition from early to mid-successional stages. It increased for the first 9–16 years of succession but declined afterwards. Species richness showed an opposing pattern, while species abundance increased asymptotically. We suggest that plant-animal interactions play a key role in mediating these processes: By importing seeds of highly competitive plant species, animals are likely to promote the increasing abundance of a few dominant, highly epizoochorous species. These species outcompete weak competitors and species richness decreases. However, animals should as well promote the subsequent increase of species richness by disturbing the sites and creating small open patches. These patches are colonized by weaker competitors that are not necessarily dispersed by animals. The changes in the presence of epizoochorous species indicate the importance of plant traits and related plant–animal interactions in the succession of plant communities.

Phylogenetically related species are assumed to be ecologically similar. Ecological similarity might lead to competition and to low distributional overlap. Therefore, if competitive interactions drive assemblages, we expect a decrease in distributional overlap with increasing phylogenetic relatedness and phylogenetic over-dispersion in assemblages. We tested this hypothesis by evaluating the mean phylogenetic distance of bat assemblages within grid cells of ≈36 km 2 across Bavaria, Germany (887 grids; 20,023 records). To calculate phylogenetic distance between species, we used a phylogenetic tree derived from sequences of three mitochondrial genes (cytb, COI, ND1), two nuclear-protein-encoding genes (vWF, RAG2) and the genes encoding16S rRNA, 12S rRNA and tRNA-Val. Overall, bat species co-occurring within grid cells were more similar than expected from null models (phylogenetic clustering). This suggests that on the considered scale, bat assemblages are triggered more by environmental filters than by competition. Furthermore, mean phylogenetic distance decreased with the amount of anthropogenic habitats within grids. This contrasts with species richness of bats, which increased with anthropogenic habitats.

Whether diversity and composition of avian communities is determined primarily by responses of species to the floristic composition or to the structural characteristics of habitats has been an ongoing debate, at least since the publication of MacArthur and MacArthur (1961). This debate, however, has been hampered by two problems: 1) it is notoriously time consuming to measure the physiognomy of habitat, particularly in forests, and 2) rigorous statistical methods to predict the composition of bird assemblages from assemblages of plants have not been available. Here we use airborne laser scanning (lidar) to measure the habitat (vegetation) structure of a montane forest across large spatial extents with a very fine grain. Furthermore, we use predictive co-correspondence and canonical correspondence analyses to predict the composition of bird communities from the composition and structure of another community (i.e. plants). By using these new techniques, we show that the physiognomy of the vegetation is a significantly more powerful predictor of the composition of bird assemblages than plant species composition in the field and as well in the shrub/tree layer, both on a level of p

The effects of set-aside and intensive management of agricultural soils on soil organic carbon (SOC) and nitrogen (N) mineralisation rates (gross and net rates), microbial biomass (chloroform-fumigation extraction method) and microbial community structure (phospholipid fatty acid analysis, PLFA) were assessed during one growing season (June and September). A former arable soil which has been set-aside as fallow with natural succession vegetation (“fallow land”) was compared to a soil under intensive agricultural management (“intensive”) with site conditions typical of NE-Saxony, Germany. The soil type was a sandy Cambisol. Six years of intensive agricultural management significantly decreased SOC and TN contents as well as pH and increased NO 3 -N contents in the topsoil (0–10 cm) compared to fallow soil. As indicated by higher gross N mineralisation rates, the potential to deliver N increased during the fallow period. However, the substrate use efficiency of microorganisms and the turnover of the microbial biomass were higher in the intensively managed soil. Independent of management system SOC mineralisation, net N mineralisation, gross NH 4 consumption and gross NO 3 transformation rates increased with increasing water content from June to September. Principal component analysis of PLFA data indicated differences in the microbial community composition between the sites. However, in total the soil microbial community was more stable against land-use changes than against seasonal changes. The PLFA profiles of both sites changed into the same direction from June to September. Only the relative abundances of PLFA marker characteristic of Gram − bacteria and fungi showed a site × time interaction as did the MBC/MBN ratio and the MBN content. In total, the influence of land-use on most examined parameters of the sandy Cambisol was less pronounced than seasonal changes. Therefore, set-aside and taking set-aside land back into intensive agricultural production seem to be a reasonable management practice for sites on sandy Cambisols in NE-Saxony, Germany.

Information on species diversity is urgently needed but often unavailable. Conservation biologists have therefore used the ‘Higher-Taxon Approach’ to predict the distribution of α-diversity of species from the diversities of higher taxa. We expanded this approach. We studied the Kenyan woody plant flora on a 56×56 km grid basis and found that the distribution of species α-diversity could be predicted precisely even from ordinal diversity. In contrast, the distribution of species β-diversity was difficult to predict even from the genus level, although within biogeographic zones the prediction improved. The spatial scale of species α-diversity could be predicted precisely only from genus level, and was hardly predictable from ordinal level. The spatial scale of species β-diversity was roughly predictable from genus to ordinal levels. Overall, the Higher-Taxon Approach could be expanded to a rough prediction of the spatial scale of species diversities. But, the approach only poorly predicted the spatial distribution of species β-diversity.