Browsing by Author "Kesting, S."

Semi‐natural grasslands often serve as important reserves of biodiversity. In Europe extensive grazing by livestock is considered an appropriate management to conserve biodiversity value and to limit shrub encroachment. However, little is known about the influence of shrubs on agronomic values. A gradient analysis of shrub‐invaded temperate grasslands (from shrub‐free to pioneer forest) in Germany was carried out to test the hypothesis that herbage mass and variables describing nutritive value of herbage decrease with increasing shrub encroachment. The herbage mass of dry matter (DM), variables describing the nutritive value of herbage, composition of the vegetation and mean of Ellenberg’s indicator values were analysed with respect to the extent of shrubs. There was a reduction of herbage mass of DM from 3570 to 210 kg ha−1 with increasing shrub encroachment. Metabolizable energy concentration of herbage ranged from 8·9 to 10·2 MJ kg−1 DM and crude protein concentration from 72 to 171 g kg−1 DM, both measures being positively correlated with shrub occurrence. Increasing shrub occurrence was associated with a decrease in water‐soluble carbohydrates concentration (from 151 to 31 g kg−1) and a reduction in the indicator ‘forage value’. The results indicate a potentially large agronomic value for shrub‐encroached temperate grasslands.

n the present study, we examined the effect of shrub encroachment in temperate semi-natural grasslands on plant species diversity. We tested the hypothesis that an initial shrub encroachment leads to enhanced habitat heterogeneity and thereby to a higher diversity. In a calcareous grassland near Göttingen (Germany) we analysed the effect of shrub encroachment on the species richness in 30, 100 m2 plots each with 10 subplots of 1m2 size. The 30 main plots belonged to six different shrub encroachment classes. A descriptive correlative gradient analysis of shrub invaded grasslands and their species number of flowering plants was performed. Within the 30 plots of different shrub encroachment a total of 203 plant species were recorded. The mean α1-diversity (level of subplots), mean α2-diversity (level of plots) as well as the α3-diversity (level of shrub encroachment classes) have their highest values at medium shrub invaded sites. This finding is in line with our hypothesis of a hump-back relation between shrub encroachment and species richness, and can be explained by the increased habitat heterogeneity. However, Detrended Correspondence Analysis (DCA) emphasized the importance of the present vegetation composition for species richness. The dominance of highly competitive, clonal-growing grass species is accompanied by low diversity swards with a lower facilitation of shrub establishment. Species accumulation curves highlight the benefit of shrub encroachment for γ-(landscape-) diversity. This result emphasises the importance of habitat heterogeneity for biodiversity and, therefore, nature conservation.

A large proportion of rangeland in western Iran is in either fair or poor condition. The objective of this study was to analyse the main drivers of rangeland degradation and the vegetational changes that come along with it, and thereby identify mitigation options. A number of 43 main plots were sampled in four grazing areas using a stratified double sampling method. Soil and topographic variables, plant species richness and the distribution of species composition were determined. A measure of grazing intensity was obtained from livestock census data of the different grazing areas. For data analysis, parametric and non-parametric statistics as well as multivariate data analysis techniques were used. Of the measured environmental variables, altitude was the single one that showed a significant linear correlation with species richness. Furthermore, only the amount of K, the percentage cover of stones, and north-facing aspect were related with species composition. Grazing intensity as a management variable was negatively associated with species richness. The results indicated that past and present grazing intensity may have been an important factor influencing species richness and distribution of species composition in semi-arid rangeland in western Iran.

Overgrazing is the main factor causing rangeland degradation in Iran. The main objectives of this study were to investigate the influence of grazing intensity on the palatability of the herbage and how bush encroachment is related to long-term grazing pressure. Herbage palatability was assessed as the weighted palatability composition of the vegetation considering palatability classes and the abundance of herbaceous and woody plant species. Grazing intensity as a management factor was estimated based on the livestock number of different grazing areas. To this end, 43 main plots were sampled in the rangeland areas of two catchments in the south-east of Kermanshah. High grazing intensity was negatively associated with biomass, species richness, herbaceous cover and palatability. Furthermore, the results indicated that encroachment of the rangeland by shrubs and invader species probably resulted from overgrazing. The results hint at overgrazing as a main factor for decreased palatability of the herbage in rangelands in Kermanshah.

Rangeland condition has often been assessed in relation to either botanical, edaphic, environmental or management factors. In this investigation, we analysed the interaction of soil and topographic variables, management and range condition against the background of a sociological survey of livestock owners in western Iran to better understand the main influencing factors of rangeland quality in the area. In four grazing areas in Kermanshah differing in grazing pressure, environmental variables and livestock owners’ perceptions on range condition, investigations of botanical composition, soil and topographic variables were carried out on 43 main plots. To evaluate range condition, four factors were considered, namely litter frequency, herbage palatability, amount of biomass, and percentage of bare soil. A questionnaire was used to obtain information about management practices, the perception of livestock owners on range condition and suggested solutions to problems in the different grazing areas. The range condition scores showed that the condition of the sites was either fair or poor. Of the soil and topographic factors, only north-facing aspect explained part of the variation in range condition scores. High grazing intensity was associated with poor range condition. To improve the rangeland condition, measures influencing water availability and a reduction of grazing pressure seem to be more relevant in the study area than fertilisation or seeding.