580 Pflanzen (Botanik)
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Aboveground herbivory induces physiological responses, like the release of belowground chemical defense and storage of secondary metabolites, as well as physical responses in plants, like increased root biomass production. However, studies on effects of aboveground herbivory on root morphology are scarce and until now no study tested herbivory effects under natural conditions for a large set of plant species. Therefore, in a field experiment on plant-soil interactions, I investigated the effect of aboveground insect herbivory on root morphological traits of 20 grassland plant species. For 9 of the 20 species, all individuals showed shoot damage in the presence of insect herbivores, but no damage in insect herbivore exclusions. In these 9 species root biomass increased and root morphological traits changed under herbivory towards thinner roots with increased specific root surface. In contrast, the remaining species did not differ in the number of individuals damaged, root biomass nor morphological traits with herbivores present vs. absent. The fact that aboveground herbivory resulted in thinner roots with increased specific root surface area for all species in which the herbivore exclusion manipulation altered shoot damage might indicate that plants increase nutrient uptake in response to herbivory. However, more importantly, results provide empirical evidence that aboveground herbivory impacts root morphological traits of plants. As these traits are important for the occupation of soil space, uptake processes, decomposition and interactions with soil biota, results suggest that herbivory-induced changes in root morphology might be of importance for plant-soil feedbacks and plant-plant competition.
Bryophytes constitute an important and permanent component of the grassland flora and diversity in Europe. As most bryophyte species are sensitive to habitat change, their diversity is likely to decline following land-use intensification. Most previous studies on bryophyte diversity focused on specific habitats of high bryophyte diversity, such as bogs, montane grasslands, or calcareous dry grasslands. In contrast, mesic grasslands are rarely studied, although they are the most common grassland habitat in Europe. They are secondary vegetation, maintained by agricultural use and thus, are influenced by different forms of land use. We studied bryophyte species richness in three regions in Germany, in 707 plots of 16 m(2) representing different land-use types and environmental conditions. Our study is one of the few to inspect the relationships between bryophyte richness and land use across contrasting regions and using a high number of replicates. Among the managed grasslands, pastures harboured 2.5 times more bryophyte species than meadows and mown pastures. Similarly, bryophyte cover was about twice as high in fallows and pastures than in meadows and mown pastures. Among the pastures, bryophyte species richness was about three times higher in sheep grazed plots than in the ones grazed by cattle or horses. In general, bryophyte species richness and cover was more than 50% lower in fertilized than in unfertilized plots. Moreover, the amount of suitable substrates was linked to bryophyte diversity. Species richness of bryophytes growing on stones increased with stone cover, and the one of bryophytes growing on bark and deadwood increased with larger values of woody plant species and deadwood cover. Our findings highlight the importance of low-intensity land use and high structural heterogeneity for bryophyte conservation. They also caution against an intensification of traditionally managed pastures. In the light of our results, we recommend to maintain low-intensity sheep grazing on sites with low productivity, such as slopes on shallow soils.
Bryophytes constitute an important and permanent component of the grassland flora and diversity in Europe. As most bryophyte species are sensitive to habitat change, their diversity is likely to decline following land-use intensification. Most previous studies on bryophyte diversity focused on specific habitats of high bryophyte diversity, such as bogs, montane grasslands, or calcareous dry grasslands. In contrast, mesic grasslands are rarely studied, although they are the most common grassland habitat in Europe. They are secondary vegetation, maintained by agricultural use and thus, are influenced by different forms of land use. We studied bryophyte species richness in three regions in Germany, in 707 plots of 16 m2 representing different land-use types and environmental conditions. Our study is one of the few to inspect the relationships between bryophyte richness and land use across contrasting regions and using a high number of replicates.Among the managed grasslands, pastures harboured 2.5 times more bryophyte species than mead-ows and mown pastures. Similarly, bryophyte cover was about twice as high in fallows and pastures than in meadows and mown pastures. Among the pastures, bryophyte species richness was about three times higher in sheep grazed plots than in the ones grazed by cattle or horses. In general, bryophyte species richness and cover was more than 50% lower in fertilized than in unfertilized plots. Moreover, the amount of suitable substrates was linked to bryophyte diversity. Species richness of bryophytes growing on stones increased with stone cover, and the one of bryophytes growing on bark and deadwood increased with larger values of woody plant species and deadwood cover. Our findings highlight the importance of low-intensity land use and high structural heterogeneity for bryophyte conservation. They also caution against an intensification of traditionally managed pastures. In the light of our results, we recommend to maintain low-intensity sheep grazing on sites with low productivity, such as slopes on shallow soils.