Intensive grazing leads to degradation and spatial homogenization of topsoils in two major steppetypes in Inner Mongolia , P .R . China

Introduction Intensive land use and especially overgrazing in semi‐arid grasslands results in degradation of steppe vegetation associated with changes in the amount ,composition ,and turnover of soil organic matter (SOM) . The concurrent degradation of soil structure and destruction of aggregation leads to enhanced soil erosion .The effectof intensive grazing on the amount and composition of SOM was assessed by comparison of grazed and ungrazed plots in Leymus chinensis and Stipa grandis dominated steppe types in Inner Mongolia ,Chin

Organische Düngung in der Karpfenteichwirtschaft: Fischertrag und Umweltaspekte

Dieses Mesokosmenexperiment befasst sich mit verschiedenen Maßnahmen zur Steigerung der Naturnahrung in Teichen unter Nutzung natürlicher Ressourcen. Das Ziel war, Naturertrag, Nachhaltigkeit und Produktqualität in der Karpfenteichwirtschaft zu verbessern. Durch organische Düngung mit Pferde- und Hühnermist (3t/ha) konnte in Teichen mit nährstoffärmeren Teichböden (P2O5-CAL 13,4 mg/100 g Boden) die Nährtierdichte erhöht und der Fischertrag durchschnittlich um etwa 200 kg/ha gesteigert werden. Zudem hatte die organische Düngung am Ende der Produktionsperiode keinen signifikanten Einfluss auf die Wasser- und Bodenqualitätsparameter

Projected loss of soil organic carbon in temperate agricultural soils in the 21^stcentury: effects of climate change and carbon input trends

Climate change and stagnating crop yields may cause a decline of SOC stocks in agricultural soils leading to considerable CO2 emissions and reduced agricultural productivity. Regional model-based SOC projections are needed to evaluate these potential risks. In this study, we simulated the future SOC development in cropland and grassland soils of Bavaria in the 21st century. Soils from 51 study sites representing the most important soil classes of Central Europe were fractionated and derived SOC pools were used to initialize the RothC soil carbon model. For each site, long-term C inputs were determined using the C allocation method. Model runs were performed for three different C input scenarios as a realistic range of projected yield development. Our modelling approach revealed substantial SOC decreases of 11–16% under an expected mean temperature increase of 3.3 °C assuming unchanged C inputs. For the scenario of 20% reduced C inputs, agricultural SOC stocks are projected to decline by 19–24%. Remarkably, even the optimistic scenario of 20% increased C inputs led to SOC decreases of 3–8%. Projected SOC changes largely differed among investigated soil classes. Our results indicated that C inputs have to increase by 29% to maintain present SOC stocks in agricultural soils

Biotic and abiotic controls on carbon storage in aggregates in calcareous alpine and prealpine grassland soils

Alpine and prealpine grasslands provide various ecosystem services and are hotspots for the storage of soil organic C (SOC) in Central Europe. Yet, information about aggregate-related SOC storage and its controlling factors in alpine and prealpine grassland soils is limited. In this study, the SOC distribution according to the aggregate size classes large macroaggregates (> 2000 μm), small macroaggregates (250–2000 μm), microaggregates (63–250 μm), and silt-/clay-sized particles (< 63 μm) was studied in grassland soils along an elevation gradient in the Northern Limestone Alps of Germany. This was accompanied by an analysis of earthworm abundance and biomass according to different ecological niches. The SOC and N stocks increased with elevation and were associated with relatively high proportions of water-stable macroaggregates due to high contents of exchangeable Ca$^{2+}$ and Mg$^{2+}$. At lower elevations, earthworms appeared to act as catalyzers for a higher microaggregate formation. Thus, SOC stabilization by aggregate formation in the studied soils is a result of a joined interaction of organic matter and Ca$^{2+}$ as binding agents for soil aggregates (higher elevations), and the earthworms that act as promoters of aggregate formation through the secretion of biogenic carbonates (low elevation). Our study highlights the importance of aggregate-related factors as potential indices to evaluate the SOC storage potential in other mountainous grassland soils

Einfluss von Maßnahmen der Bodennutzung auf Bodenfunktionen

Eine wesentliche Voraussetzung für eine nachhaltige Bodennutzung ist die Beurteilung der Wirkung von Bodennutzungsmaßnahmen auf Bodenfunktionen. Als solche betrachten wirdie Produktion von Biomasse, die Speicherung von Wasser und Kohlenstoff, die Filterung von Wasser und die Funktion des Bodens als Lebensraum für Organismen. Um den Einfluss von Maßnahmen der Bodennutzung auf diese Funktionen vorhersagenzu können ist ein umfassendes Verständnis von Bodenprozessen unabdingbar. Unser Ansatz ist die dominierenden Komponenten (Prozesse und funktionellen Eigenschaften) in Böden und ihre Interaktionen zu identifizieren. Der Fokus liegt hierbei auf funktionellen Eigenschaften, die sich nur relativ langsam verändern und als Indikatoren für die zugrundeliegenden, wechselwirkenden Bodenprozessen interpretiert werden können. Die Identifizierung der wichtigsten Interaktionen basiert auf einer Analyse der vorhandenen Literatur. Diese soll als Suchmaschine der gesamten bodenwissenschaftlichen Gemeinschaft zur Verfügung gestellt werden. Darüber hinaus wird für spezifische Wechselwirkung auf bestehende Modellansätze zurückgegriffen. Ebenso werden bestehende Modelle genutzt um aus detaillierter Prozessmodellierung die langfristigen Bodenfunktionen abzuschätzen

Does conversion to reduced tillage really increase soil organic carbon stocks in organic arable farming?

Aggravation of weather extremes increases awareness of climate change consequences. Mitigation options are in demand that aim to reduce the atmospheric concentration of greenhouse gases. Amongst others, the conversion from ploughing to reduced tillage is argued to increase soil organic carbon (SOC) stocks as an accumulation of SOC in topsoil layers is commonly reported. Yet, reviews and meta-analyses describe various results from significant increases to just a redistribution of SOC in the soil profile. Reasons can be found in different sampling depths, SOC and bulk density measurement procedure, and stock calculation (equivalent soil mass vs. equal sampling depth). Furthermore, few studies evaluated the impact of organic farming systems. In nine long-term experiments on tillage systems in temperate Europe (France, Germany, Netherlands, and Switzerland), a common soil sampling campaign took place in spring and autumn 2017, and spring 2018. All trials represent common mixed organic farming systems of the respective region and contain plots with conventional and reduced tillage practices. While climatic conditions are similar, soil types vary from sandy to clayey soils. We took three undisturbed soil cores with driving hammer probes (8 cm in diameter) in each plot (minimum 3 plots per treatment) to a maximum depth of 100 cm and divided the cores in the increments 0-30, 30-50, 50-70, and 70-100 cm. The topsoil (0-30 cm) was further divided into the different tillage depths of the respective trial. We determined bulk density and organic carbon concentration as main variables and soil texture and pH as co-variates for each sample and collected C-inputs for each plot in all trails on a yearly basis. Multivariate statistics will enable the comprehensive evaluation of tillage effects on SOC stocks up to a depth of 100 cm in organic long-term trials. Texture, trial age, and the co-variate C-input will be decisive for the development of SOC stocks and enable the evaluation of carbon sequestration potentials of agricultural soils through improved tillage practices

Variation in carbon isotope discrimination in Cleistogenes squarrosa (Trin.) Keng: patterns and drivers at tiller, local, catchment, and regional scales

Understanding the patterns and drivers of carbon isotope discrimination in C4 species is critical for predicting the effects of global change on C3/C4 ratio of plant community and consequently on ecosystem functioning and services. Cleistogenes squarrosa (Trin.) Keng is a dominant C4 perennial bunchgrass of arid and semi-arid ecosystems across the Mongolian plateau of the Eurasian steppe. Its carbon isotope discrimination (13Δ) during photosynthesis is relatively large among C4 species and it is variable. Here the 13Δ of C. squarrosa and its potential drivers at a nested set of scales were examined. Within cohorts of tillers, 13Δ of leaves increased from 5.1‰ to 8.1‰ from old to young leaves. At the local scale, 13Δ of mature leaves varied from 5.8‰ to 8.4‰, increasing with decreasing grazing intensity. At the catchment scale, 13Δ of mature leaves varied from 6.2‰ to 8.5‰ and increased with topsoil silt content. At the regional scale, 13Δ of mature leaves varied from 5.5‰ to 8.9‰, increasing with growing-season precipitation. At all scales, 13Δ decreased with increasing leaf nitrogen content (Nleaf). Nleaf was positively correlated with grazing intensity and leaf position along tillers, but negatively correlated with precipitation. The presence of the correlations across a range of different environmental contexts strongly implicates Nleaf as a major driver of 13Δ in C. squarrosa and, possibly, other C4 species