B. Tonn

Effect of grazing intensity and soil characteristics on soil organic carbon and nitrogen stocks in a temperate long-term grassland

ABSTRACT The effects of different grazing pressures (GPs) on soil properties are not sufficiently understood. The objectives were to analyse the effects of three different extensive GPs on stocks of soil organic C and total N, soil microbial biomass C, basal respiration and mineral N in three different soil depths of a long-term pasture in Central Germany (FORBIOBEN field trial). No significant (p ≤ 0.05) effects of GP on weighted stocks of soil organic C, total N, soil microbial biomass C, mineral N and basal respiration rate were observed, suggesting that the C and N cycles are coupled in the three grazing treatments. Oxalate soluble Fe contents explained a marked part of the variation of soil organic C (multiple linear regression: R2 = 0.64) and total N contents (R2 = 0.64) in the soils, whereas almost all of the variability of soil microbial biomass C contents and basal respiration was explained by soil organic C contents. Overall, variabilities of soil organic C and N contents were largely explained by oxalate soluble Fe contents, whereas grazing intensity did not affect the C and N dynamics.

Soil pH and phosphorus drive species composition and richness in semi-natural heathlands and grasslands unaffected by twentieth-century agricultural intensification

ABSTRACT Background: Increased soil phosphorus (P) caused by agricultural intensification has been associated with decreased plant species richness (SR) in central Europe. How plant communities and soil P gradients are related in unimproved open habitats remains unclear. Aims: The aim of this article was to characterise the relationship between soil chemical parameters and plant species composition and richness in unimproved open habitats. Methods: The influence of soil chemical parameters (pH, P, K, Mg) on species composition was assessed, using data from 40 heathland and 54 grassland plots, by non-metric multidimensional scaling and permutational multivariate analysis of variance. The relationship between soil chemical parameters and SR was tested by linear mixed effects models. Results: A direct relationship between heathland community composition and pH was observed, explaining 10% of variation in species composition, while P, Mg and pH together explained 17% of variation in grassland composition. In heathlands, SR increased with increasing pH, whereas in grasslands, SR decreased with increasing soil P. Conclusions: Soil chemical parameters were substantially related to plant community composition and richness. In an area spared from a century of agricultural intensification, reduced pH appeared to constrain SR in heathlands, while even slight P increases (<10 mg kg−1) depressed plant SR in semi-natural grasslands.

Mapping semi-natural grassland communities using multi-temporal RapidEye remote sensing data

ABSTRACT Mapping semi-natural grassland has become increasingly important with regard to climate variability, invasive species, and the intensification of land use. At the same time, adequate field data collection is of pivotal importance for national and international reporting obligations, such as the European Habitats Directive. We present a remote-sensing-based monitoring framework for a Natura 2000 site with a heterogeneous composition of different grassland communities, using the Random Forest algorithm. Automated training data selection was successfully implemented based on the Random Forest proximity measure (Overall Accuracy ranging from 77.5–86.5%). RapidEye acquisitions originating from the onset of vegetation (prespring and first spring) and senescence (late summer and first autumn) were identified as important phenological phases for mapping semi-natural grassland communities. The derived probability maps of occurrences for each grassland class captured transitions between grassland communities and are therefore a better approximation of real-world conditions compared to classical, discrete maps.

Herbage biomass and uptake under low-input grazing as affected by cattle and sheep excrement patches

In low-input grazing systems excrement patches are the main nutrient input. They influence both forage production and intake of grazing animals. Our goals were to determine (1) whether seasons of differing weather conditions and swards of differing botanical composition influence the excrement effect on plant biomass in grazed pasture and (2) if animal species differ in their forage intake at excrement patches. We measured the plant biomass and forage intake responses to dung and urine patches of cattle and sheep in rotationally grazed low-input pastures with either grass-dominated or diverse swards in the stocking periods following excrement deposition in spring and autumn. At urine plots the plant biomass production was 14.7% higher than at the corresponding control plots, accompanied by a 19 and 17% higher biomass nitrogen and potassium concentration, respectively. The effect of excrements on plant biomass production, nutrient parameters and animal forage intake was not affected by animal species, sward type or stocking period. Small-scale sward height measurements showed that cattle avoided vegetation close to dung patches in both stocking periods whereas sheep did so only following the excrement deposition in spring and that cattle preferentially grazed at urine plots on grass-dominated swards. The effect of excrement patches on vegetation biomass parameters was small, which masked potential influences by animal species, sward type and excrement deposition time.