Organic vs. Conventional Grassland Management: Do 15N and 13C Isotopic Signatures of Hay and Soil Samples Differ?

Distinguishing organic and conventional products is a major issue of food security and authenticity. Previous studies successfully used stable isotopes to separate organic and conventional products, but up to now, this approach was not tested for organic grassland hay and soil. Moreover, isotopic abundances could be a powerful tool to elucidate differences in ecosystem functioning and driving mechanisms of element cycling in organic and conventional management systems. Here, we studied the δ15N and δ13C isotopic composition of soil and hay samples of 21 organic and 34 conventional grasslands in two German regions. We also used Δδ15N (δ15N plant - δ15N soil) to characterize nitrogen dynamics. In order to detect temporal trends, isotopic abundances in organic grasslands were related to the time since certification. Furthermore, discriminant analysis was used to test whether the respective management type can be deduced from observed isotopic abundances. Isotopic analyses revealed no significant differences in δ13C in hay and δ15N in both soil and hay between management types, but showed that δ13C abundances were significantly lower in soil of organic compared to conventional grasslands. Δδ15N values implied that management types did not substantially differ in nitrogen cycling. Only δ13C in soil and hay showed significant negative relationships with the time since certification. Thus, our result suggest that organic grasslands suffered less from drought stress compared to conventional grasslands most likely due to a benefit of higher plant species richness, as previously shown by manipulative biodiversity experiments. Finally, it was possible to correctly classify about two third of the samples according to their management using isotopic abundances in soil and hay. However, as more than half of the organic samples were incorrectly classified, we infer that more research is needed to improve this approach before it can be efficiently used in practice

Patterns and Determinants of Post-Soviet Cropland Abandonment in the Western Siberian Grain Belt

The transition from a command to a market economy resulted in widespread cropland abandonment across the former Soviet Union during the 1990s. Spatial patterns and determinants of abandonment are comparatively well understood for European Russia, but have not yet been assessed for the vast grain belt ofWestern Siberia, situated in the Eurasian forest steppe. This is unfortunate, as land-use change in Western Siberia is of global significance: Fertile black earth soils and vast mires store large amounts of organic carbon, and both undisturbed and traditional cultural landscapes harbor threatened biodiversity. We compared Landsat images from ca. 1990 (before the break-up of the Soviet Union) and ca. 2015 (current situation) with a supervised classification to estimate the extent and spatial distribution of abandoned cropland. We used logistic regression models to reveal important determinants of cropland abandonment. Ca. 135,000 ha classified as cropland around 1990 were classified as grassland around 2015. This suggests that ca. 20% of all cropland remain abandoned ca. 25 years after the end of the Soviet Union. Abandonment occurred mostly at poorly drained sites. The likelihood of cropland abandonment increased with decreasing soil quality, and increasing distance to medium-sized settlements, roads and railroads. We conclude that soil suitability, access to transport infrastructure and availability of workforce are key determinants of cropland abandonment inWestern Siberia

Marmots from space: assessing population size and habitat use of a burrowing mammal using publicly available satellite images

Social, burrowing mammals such as prairie dogs, ground squirrels or marmots are keystone species in grassland ecosystems. Grasslands have been converted into cropland or pastures globally, yet it remains virtually unknown how this has affected the biogeography of burrowing mammals, as efficient, broad-scale survey methods are lacking. We aimed to test whether structures created by burrowing rodents can be reliably detected on publicly available, very-high-resolution satellite images, in order to assess rodent distribution and abundance. We identified burrows of Bobak marmot (Marmota bobak), a keystone burrowing steppe rodent, on 1300 randomly selected plots of 1 km diameter (78.53 ha) across the species’ range (~950 000 km²) in Kazakhstan and southern Russia using Google Earth and Bing images. We then used burrow occurrences and species distribution models to map marmot distribution. We assessed how marmot occurrence and density vary across land-use types. We also combined satellite-based burrow densities and ground-survey data to derive a new population estimate for the species across Kazakhstan. We mapped a total of 7425 burrows from the satellite imagery. Field visits at a subsample of burrows suggested that burrow occurrence was detected reliably. Broad-scale marmot distribution was mainly determined by summer rainfall, land use and elevation. Occurrence probability was highest on arable croplands, followed by abandoned croplands and grazed steppe. The current Bobak marmot population size for Kazakhstan was estimated at 6.1 (±2.4) million individuals. Our results demonstrate that publicly available, very-high-resolution images can be used to reliably map the distribution of burrowing mammals across large geographic scales. The observed and predicted distributions indicate that the Bobak's range has remained almost unchanged in Kazakhstan since the 1950s, despite several drastic episode of land-use change. This suggests that burrowing mammals can be remarkably resilient to land-use pressure, questioning prevailing narratives of population collapse in these species following agricultural expansion

Heterogeneity decreases as time since fire increases in a South American grassland

Questions: Disturbances change the fundamental properties of grasslands on different spatio-temporal scales. Uruguay is part of the Río de la Plata grasslands, and 60% is occupied by native grasslands dominated by perennial species. In plant communities dominated by tall tussock grasses, patchy and asynchronous field burns are a traditional practice among ranchers. We asked: how do the structural characteristics of vegetation vary in patches with different time since the last fire? Location: Grassland of the Eastern Hills, Uruguay. Methods: We selected 18 grazed sites in order to obtain a spatial chronosequence with four age categories since the last fire: 6, 18, 30, and more than 60 months before sampling. Plant composition, species richness, coverage of each species, bare soil, and standing dead biomass were determined in plots of 25 m2. We used nonmetric multidimensional scaling (NMDS) and the multiresponse permutation procedure (MRPP) to determine differences in community composition, and the ANOVA or the Kruskal–Wallis test to compare structural variables between patches of different burning ages. Results: Patches of different burning age had different species compositions. Species richness, Shannon diversity index, evenness, and bare soil decreased, whereas plant coverage, standing dead biomass, and vegetation strata increased as time since the last fire increased. Conclusions: Our study confirmed occasional and localized field-burns as major driver of vegetation change and structural diversity in a grazed native grassland dominated by a tall tussock grass. On a larger scale, we observed the coexistence of patches in different successional stages and differences in species composition between patches belonging to early stages. These grasslands require asynchronous burning of patches to generate structural changes that maximize both the spatial and temporal heterogeneity.Agencia Nacional de Investigación e InnovaciónComisión Sectorial de Investigación CientíficaInstituto Nacional de Investigación AgropecuariaComisión Académica de PosgradoInter-American Institute for Global Change Researc

Land use intensification alters ecosystem multifunctionality via loss of biodiversity and changes to functional composition

Global change, especially land-use intensification, affects human well-being by impacting the deliv-ery of multiple ecosystem services (multifunctionality). However, whether biodiversity loss is amajor component of global change effects on multifunctionality in real-world ecosystems, as inexperimental ones, remains unclear. Therefore, we assessed biodiversity, functional compositionand 14 ecosystem services on 150 agricultural grasslands differing in land-use intensity. We alsointroduce five multifunctionality measures in which ecosystem services were weighted according torealistic land-use objectives. We found that indirect land-use effects, i.e. those mediated by biodi-versity loss and by changes to functional composition, were as strong as direct effects on average.Their strength varied with land-use objectives and regional context. Biodiversity loss explainedindirect effects in a region of intermediate productivity and was most damaging when land-useobjectives favoured supporting and cultural services. In contrast, functional composition shifts,towards fast-growing plant species, strongly increased provisioning services in more inherentlyunproductive grasslands

Towards the development of general rules describing landscape heterogeneity-multifunctionality relationships

Rapid growth of the world's human population has increased pressure on landscapes to deliver high levels of multiple ecosystem services, including food and fibre production, carbon storage, biodiversity conservation, and recreation. However, we currently lack general principles describing how to achieve this landscape multifunctionality. We combine theoretical simulations and empirical data on 14 ecosystem services measured across 150 grasslands in three German regions. In doing so, we investigate the circumstances under which spatial heterogeneity in a driver of ecosystem functioning (an ecosystem-driver, e.g., the presence of keystone species, land-use intensification, or habitat types) increases landscape-level ecosystem multifunctionality. Simulations based on theoretical data demonstrated that relationships between heterogeneity and landscape multifunctionality are highly variable and can range from nonsignificant to strongly positive. Despite this variability, we could identify criteria under which heterogeneity-landscape multifunctionality relationships were most strongly positive: this happened when multiple ecosystem services responded contrastingly (both positively and negatively) to an ecosystem-driver. These findings were confirmed using empirical data, which showed that heterogeneity in land-use intensity (LUI) promoted landscape multifunctionality in cases where functions with both positive (e.g., plant biomass) and negative (e.g., flower cover) responses to land use intensification were included. For example, the simultaneous provisioning of ecosystem functions related to forage production (generally profiting from land-use intensification), biodiversity conservation and recreation (generally decreasing with land-use intensification) was highest in landscapes consisting of sites varying in LUI. Synthesis and applications. Our findings show that there are general principles governing landscape multifunctionality. A knowledge of these principles may support land management decisions. For example, knowledge of relationships between ecosystem services and their drivers, such as land use type, can help estimate the consequences of increasing or decreasing heterogeneity for landscape-level ecosystem service supply, although interactions between landscape units (e.g., the movement of pollinators) must also be considered

Temporal and small-scale spatial variation in grassland productivity, biomass quality, and nutrient limitation

Characterization of spatial and temporal variation in grassland productivity and nutrition is crucial for a comprehensive understanding of ecosystem function. Although within-site heterogeneity in soil and plant properties has been shown to be relevant for plant community stability, spatiotemporal variability in these factors is still understudied in temperate grasslands. Our study aimed to detect if soil characteristics and plant diversity could explain observed small-scale spatial and temporal variability in grassland productivity, biomass nutrient concentrations, and nutrient limitation. Therefore, we sampled 360 plots of 20 cm × 20 cm each at six consecutive dates in an unfertilized grassland in Southern Germany. Nutrient limitation was estimated using nutrient ratios in plant biomass. Absolute values of, and spatial variability in, productivity, biomass nutrient concentrations, and nutrient limitation were strongly associated with sampling date. In April, spatial heterogeneity was high and most plots showed phosphorous deficiency, while later in the season nitrogen was the major limiting nutrient. Additionally, a small significant positive association between plant diversity and biomass phosphorus concentrations was observed, but should be tested in more detail. We discuss how low biological activity e.g., of soil microbial organisms might have influenced observed heterogeneity of plant nutrition in early spring in combination with reduced active acquisition of soil resources by plants. These early-season conditions are particularly relevant for future studies as they differ substantially from more thoroughly studied later season conditions. Our study underlines the importance of considering small spatial scales and temporal variability to better elucidate mechanisms of ecosystem functioning and plant community assembly