Direct and indirect effects of land use on bryophytes in grasslands

Direct and Indirect Effects of Management Intensity and Environmental Factors on the Functional Diversity of Lichens in Central European Forests

Using 642 forest plots from three regions in Germany, we analyzed the direct and indirect effects of forest management intensity and of environmental variables on lichen functional diversity (FDis). Environmental stand variables were affected by management intensity and acted as an environmental filter: summing direct and indirect effects resulted in a negative total effect of conifer cover on FDis, and a positive total effect of deadwood cover and standing tree biomass. Management intensity had a direct positive effect on FDis, which was compensated by an indirect negative effect via reduced standing tree biomass and lichen species richness, resulting in a negative total effect on FDis and the FDis of adaptation-related traits (FDisAd). This indicates environmental filtering of management and stronger niche partitioning at a lower intensity. In contrast, management intensity had a positive total effect on the FDis of reproduction-, dispersal- and establishment-related traits (FDisRe), mainly because of the direct negative effect of species richness, indicating functional over-redundancy, i.e., most species cluster into a few over-represented functional entities. Our findings have important implications for forest management: high lichen functional diversity can be conserved by promoting old, site-typical deciduous forests with a high richness of woody species and large deadwood quantity.

Effects of fertilization and irrigation on vascular plant species richness, functional composition and yield in mountain grasslands

Land-use intensification is a major threat to biodiversity in agricultural grasslands and fertilization is one of the main drivers. The effects of fertilization on biodiversity and plant functional composition (community-weighted mean traits and mean ecological indicator values) are well studied in lowland regions, but have received less attention in mountain grasslands. Moreover, in inner-alpine dry valleys, fertilizer is often applied in combination with irrigation, and irrigation effects are less well known. We experimentally tested the effects of fertilization and irrigation on vascular plant species richness and the functional composition of mountain grasslands in the Swiss Alps. After five years, fertilization increased yield but the relationship was quadratic with maximum yield reached at intermediate fertilizer levels (58 kg N ha^-1year^-1). The species richness of all vascular plants and forbs decreased, on average, by 6 and 5 species respectively, per 50 kg N of extra fertilizer (ha^-1 year^-1) applied. Fertilization also favored fast-growing plants (increased mean specific leaf area) and plants typically found in productive environments (increased mean indicator values for soil productivity and moisture). In contrast, we found no effects of irrigation on plant community composition, which suggests that irrigation does not affect vascular plant diversity to the same extent as fertilization in these mesic mountain hay meadows, at least in the mid-term. Our finding that maximum yield can be achieved at intermediate fertilizer levels is very important from an applied, agronomical and conservation point of view. It suggests that without loss of yield, farming costs and at the same time environmental pollution and negative effects on biodiversity can be reduced by applying less fertilizer. We therefore recommend maintaining non-intensive land use and keeping fertilizer inputs as low as possible to maintain the high plant diversity of mountain grasslands.

Urban Atmospheric Environment Quality Assessment by Naturally Growing Bryophytes in Central China

Bryophytes are popular biomonitoring plants for atmospheric environments. The objectives of this study were to examine the characteristics of bryophyte communities, determine a suitable monitor species, and assess urban atmospheric environment quality by the joint use of bryophyte features and chemical properties in a large city in China. A pleurocarpous feather moss Haplocladium angustifolium was recognized as a good biomonitor of atmospheric deposition in central China by investigating bryophyte communities and habitat environment in various ecological function regions of the urban areas in Wuhan. The concentrations of trace elements, including As, Cd, Co, Cr, Cu, Mn, Ni, V, Pb, and Zn, in moss and soil samples from 25 sampling sites were analyzed by inductively coupled plasma mass spectrometry. The concentrations of Cd and Zn in Haplocladium angustifolium collected from the entire study area were much higher than those in substrate soil. Cd was at the highest ecological risk level among the 10 elements, which contributed 34.5% to the potential ecological risk index (RI). An RI value of 392.8 indicated that urban atmospheric quality in Wuhan was in a considerable potential ecological risk. The index of atmospheric purity, regarding species richness, cover, and frequency of bryophytes, was spatially and negatively correlated with RI, also demonstrated the atmospheric quality. Effective measures should be considered to alleviate certain airborne trace element contamination and protect the environment and human health in this metropolis.

Evidence for a possible extinction debt in Swiss wetland specialist plants

Habitat loss leading to smaller patch sizes and decreasing connectivity is a major threat to global biodiversity. While some species vanish immediately after a change in habitat conditions, others show delayed extinction, that is, an extinction debt. In case of an extinction debt, the current species richness is higher than expected under present habitat conditions.We investigated wetlands of the canton of Zürich in the lowlands of Eastern Switzerland where a wetland loss of 90% over the last 150 years occurred. We related current species richness to current and past patch area and connectivity (in 1850, 1900, 1950, and 2000). We compared current with predicted species richness in wetlands with a substantial loss in patch area based on the species-area relationship of wetlands without substantial loss in patch area and studied relationships between the richness of different species groups and current and historical area and connectivity of wetland patches.We found evidence of a possible extinction debt for long-lived wetland specialist vascular plants: in wetlands, which substantially lost patch area, current species richness of long-lived specialist vascular plants was higher than would have been expected based on current patch area. Additionally and besides current wetland area, historical area also explained current species richness of these species in a substantial and significant way. No evidence for an extinction debt in bryophytes was found.The possible unpaid extinction debt in the wetlands of the canton of Zürich is an appeal to nature conservation, which has the possibility to prevent likely future extinctions of species through specific conservation measures. In particular, a further reduction in wetlands must be prevented and restoration measures must be taken to increase the number of wetlands.