Mixed Grassland Research Articles

Leaf area index estimation in semiarid mixed grassland by considering both temporal and spatial variations

Leaf area index (LAI) estimation in a mixed grassland ecosystem is limited by temporal and spatial variations controlled by land surface heterogeneity and ecological parameters. Therefore, simply estimated LAI usually has difficulty in meeting the requirements of the land surface–atmosphere interaction models. We estimated LAI based on the relationship between LAI and normalized difference vegetation index (NDVI) by considering temporal and spatial variations. Spatial variations of both LAI and NDVI were investigated using the Morlet wavelet approach. Based on the ground reflectance data, LAI estimation can be greatly improved by taking temporal and spatial variations into account. The coefficient of determination (r 2 ) values of the LAI-NDVI equations were increased by 0.28, 0.51, and 0.44 in the early, maximum, and late growing seasons, respectively. LAI estimation from SPOT 4/5 and Landsat TM 5 images confirmed the applicability of the proposed estimation approach.

A comparison of winter bird communities in agricultural grassland and cereal habitats in Ireland: implications for Common Agricultural Policy reform

Capsule In winter, grassland sites had greater bird numbers compared to winter cereals, but a number of species of conservation concern were exclusively recorded on winter cereals. Aims To compare the winter bird communities in grassland and winter cereal fields. Methods Grassland and winter cereal fields were surveyed for overwintering birds in a landscape of mixed grassland and arable agriculture. Results Generalized Linear Models demonstrated that total bird abundance, the mean abundance of the majority of ecological groups and that of several common species, were significantly greater in grassland compared with winter cereal fields. However, a number of species of conservation concern, e.g. Skylark Aluda arvensis, were observed only on winter cereal fields. Only a minority of bird variables showed a positive response to field size. Of these, total bird species richness and the Shannon and Simpson's diversity indices showed positive significant responses to increasing field size, which may alternatively and perhaps more correctly be interpreted as a positive response to field boundary density within the farmed landscape. Conclusions Farmland habitats are important for the provision of overwintering resources for birds, and policy directed towards bird conservation should target the management of locally significant habitat types. The implications of these findings are discussed in light of the proposed revision of the Common Agricultural Policy in 2014, particularly the proposed measure for crop diversification.

Effects of grazing on grassland soil carbon: a global review

Soils of grasslands represent a large potential reservoir for storing CO2 , but this potential likely depends on how grasslands are managed for large mammal grazing. Previous studies found both strong positive and negative grazing effects on soil organic carbon (SOC) but explanations for this variation are poorly developed. Expanding on previous reviews, we performed a multifactorial meta-analysis of grazer effects on SOC density on 47 independent experimental contrasts from 17 studies. We explicitly tested hypotheses that grazer effects would shift from negative to positive with decreasing precipitation, increasing fineness of soil texture, transition from dominant grass species with C3 to C4 photosynthesis, and decreasing grazing intensity, after controlling for study duration and sampling depth. The six variables of soil texture, precipitation, grass type, grazing intensity, study duration, and sampling depth explained 85% of a large variation (±150gm(-2) yr(-1) ) in grazing effects, and the best model included significant interactions between precipitation and soil texture (P=0.002), grass type, and grazing intensity (P=0.012), and study duration and soil sampling depth (P=0.020). Specifically, an increase in mean annual precipitation of 600mm resulted in a 24% decrease in grazer effect size on finer textured soils, while on sandy soils the same increase in precipitation produced a 22% increase in grazer effect on SOC. Increasing grazing intensity increased SOC by 6-7% on C4 -dominated and C4 -C3 mixed grasslands, but decreased SOC by an average 18% in C3 -dominated grasslands. We discovered these patterns despite a lack of studies in natural, wildlife-dominated ecosystems, and tropical grasslands. Our results, which suggest a future focus on why C3 vs. C4 -dominated grasslands differ so strongly in their response of SOC to grazing, show that grazer effects on SOC are highly context-specific and imply that grazers in different regions might be managed differently to help mitigate greenhouse gas emissions.

BiotecVisions 2013, February

BiotecVisions 2013, February

Biophysical and spectral responses to various burn treatments in the northern mixed-grass prairie

Over the past century, environmental managers have worked to suppress fire throughout various biomes. Today, burning is generally considered beneficial to many ecosystems, though the precise effects are not entirely understood. This research aims to further our understanding of the biophysical effects of fire in C3 dominated mixed-grass prairies and to find an effective remote sensing approach for differentiating between burn treatments in late spring. Biophysical properties including vegetation cover, biomass, soil properties, canopy height, Leaf Area Index (LAI), and individual wavebands of the SPOT-5 sensor as well as two vegetation indices (Normalized Difference Vegetation Index and Normalized Burn Ratio Index) derived from SPOT-5 images were compared among unburned sites and sites with various burning treatments in Grasslands National Park, Canada. Results showed that significantly higher soil temperature and lower LAI were found in burned sites. Dead material biomass, total biomass, and percentage of standing dead cover were significantly lower in burned and grazed sites. The percentage of bare ground cover was the only biophysical variable to show significant changes in all burning treatments. Burned and unburned sites could not be distinguished based on assessing the changes of individual wavebands of the SPOT-5 sensor and the two vegetation indices. Models based on linear combinations of spectral indices were developed for biophysical properties that show significant changes in burned sites. The agreement between model simulated biophysical properties and field measured values suggest the feasibility of remote sensing to assess or monitor post-fire effects in mixed grasslands.

A suitable NDVI product for monitoring spatiotemporal variations of LAI in semiarid mixed grassland

Routinely produced Normalized Difference Vegetation Index (NDVI) products are an important source for leaf area index (LAI) in terrestrial modelling. However, little research has focused on the performance of NDVI products to identify intra-annual spatial variations of LAI in semiarid mixed grasslands where a large amount of dead plant material exists. The objective of this study was to determine a suitable NDVI product to identify spatial variation of LAI between tame and native grassland during the entire growing season in the St. Denis wildlife reserve area, Saskatchewan. MODIS 250 m NDVI products were evaluated for monitoring spatiotemporal variations of LAI by comparisons with NDVI data at 0.5 m, 10 m, and 20 m spatial resolution. Results indicate that MODIS 250 m NDVI data are closely correlated with the ground measured NDVI data with a correlation coefficient of 0.90. NDVI products with a spatial resolution of 250 m or higher can differentiate LAI of land cover types during the entire growing season in the study area. MODIS 250 m NDVI product is qualified to be a model input describing spatiotemporal variations in LAI in semiarid mixed grasslands characterized by a large amount of dead plant materials.

Comparative analysis of SPOT, Landsat, MODIS, and AVHRR normalized difference vegetation index data on the estimation of leaf area index in a mixed grassland ecosystem

Many grassland studies have depended on or are currently depending on the Landsat series of satellite sensors for monitoring work. However, given the identified gaps in Landsat data, alternatives to Landsat imagery need to be tested in an operational environment. In this study, normalized difference vegetation index (NDVI) values are derived from a Système Pour l'Observation de la Terre (SPOT), Moderate Resolution Imaging Spectroradiometer (MODIS), and Advanced Very High Resolution Radiometer (AVHRR) image and compared to the NDVI values from a Landsat image for LAI estimation in a semi-arid heterogeneous grassland. Results indicate a high agreement between Landsat and SPOT data with R2 over 85% at all buffer levels (100, 250, and 1000 m), and a significant but lower agreement between MODIS and Landsat with R2 around 28% at 250 m buffer level to 37% at 100 m buffer level. Based on in situ measurements of LAI in 22 homogeneous sites, the relationships established between LAI and NDVI show that SPOT and Landsat could predict LAI with acceptable accuracy, but MODIS and AVHRR cannot quantify the spatial variation in LAI measurements. Data fusion or blending techniques that combine the spectral information of high spatial/low temporal resolution data with low spatial/high temporal resolution data may be considered to study semi-arid heterogeneous grasslands.

高寒山区一年生混播牧草生态位对密度的响应

Niche refers to the space-time position of a population occupied and the functional relationship between it and related population.Niche including the requirements of the species on the environment and the influence of environment on species,it reflects the interaction between species and habitats quantitatively.Density-dependent is one of the important selecting pressure in nature,which makes the ground light competition between the neighborhood.by changing the number of populations within each plant availability of resources.Therefore,niche and density gradient are inseparable.To analyze the dynamic distribution rules of niche of mixed pasture from the density gradient is a significant approach to study the strategy of plant population ecological adaptation.Study sites are located in the HuangCheng town(37°58'26″ N,101°47' 34″ E) which belongs to an upper reaches ShiYang River,SuNan county of alpine region(2530 m) lying in the north of Qilian Mountains.In replacement series experiments,the two species of planting densities were varied but the total density was held constantly.It was used to build mixed-seeding meadow of Avena sativa L.and Vicia vilosa Roth in June 15,2010.This study set up seven grass-legume seeding ratios: KY(1∶0),A(8∶2),B(6∶4),C(5∶5),D(4∶6),E(2∶8),KM(0 ∶1) which maintains about 300 plants total density constantly.There are total of 21 plots(2 m × 5 m) adopted randomized block arrangement with three replications.We recorded the phonological period,plant-height and branch(tiller) number of mixed grasses every 10 days started from July 17,2010 to August 27,2010.The sampling area is 50 cm × 50 cm in every plot,the mixed grasses were separately placed into an oven at 65 ℃ for 8 hours according to the block order until it reached the constant weight,thus the biomass were recorded respectively.Niche breadth is the metric of plants scale on environment and natural resource utilization,niche overlap occurs when two or more species to take possession of or make use of a certain kind of resources(space,nutrient content,food,etc) together.Under density dependant,the niche breadth of Avena sativa L and Vicia vilosa Roth and the niche overlap of the two species transfer occurred to some extent during the growing period of grasses.The results showed that:(1) With the growth of forage,the density of Avena sativa L niche breadth decreases gradually and Vicia vilosa Roth showed a gradually increasing tendency in all group of mixed grassland,niche overlap of Vicia vilosa Roth and Avena sativa L.showed a reducing tendency.(2) In mixed grassland with Avena sativa L relative density decreases and the relative density increase of Vicia vilosa Roth..Avena sativa L niche breadth decreases gradually and Vicia vilosa Roth showed a gradually increasing tendency,the niche overlap of Avena sativa L and Vicia vilosa Roth increases gradually.To sum up,in the course of grass growth,density dependence lead the resource allocation strategies of the two mixed pasture response to intraspecific,interspecific competition adjusted.Mixed pasture competition ability' s change led to its niche in a certain degree of metastasis and differentiation,which made the relationship between species and community structure tend to be stable.To form a mutual stability and mutual influence ecological system,achieve maximum resource utilization.

Assessing light to moderate grazing effects on grassland production using satellite imagery

Understanding the influences of grazing intensity on grassland production is essential for grassland conservation and management improvement. Grazing at light to moderate intensity theoretically enhances grassland production, thus benefiting grassland ecosystems. However, inconsistent results of the beneficial effects of light to moderate grazing on grassland production were reported due to the lack of accurate and repeatable techniques for discriminating grazing effects from other abiotic factors. Advanced remote-sensing techniques provide a promising tool for filling this gap in grazing effects research due to their high spatial and temporal resolution. In this article, the influences of light to moderate grazing on grassland production in mixed grasslands were investigated for the period 1986–2005, using spectral data derived from satellite images. The effects of precipitation on the detection of grazing-induced production change were also analysed. The results revealed that the normalized canopy index (NCI) showed superior performance in quantifying grassland production in mixed grasslands. Significant differences in grassland production between grazed and ungrazed treatments occurred in the three years with above-average and average growing-season precipitations (April–August), but not in the dry years. Most of the variation in production (75%) was explained by growing-season precipitation for both grazed and ungrazed sites. Our results demonstrate the feasibility of using remote-sensing data to monitor long-term light to moderate grazing effects and the important role of precipitation, especially growing-season precipitation, in modulating production in mixed-grassland ecosystems.

Western Range Boundaries Of Floodplain Trees in the Southeastern United States

.Forest vegetation in the southeastern United States extends westward beyond the Ozark and Ouachita plateaus in Arkansas and Missouri into the Central Plains. Along this transect, luxuriant forests give way to mixed forests and grasslands that include smaller trees and progressively fewer tree species and eventually to grassland‐dominated landscapes in central Kansas, Oklahoma, and Texas. This transition is directly related to decreasing precipitation with distance to the west of the Mississippi River valley. Many species, however, have abrupt western range boundaries related to physiography and hydrogeomorphic processes. The western range limits for many trees correspond to Coastal Plain boundaries that at a regional scale impose sharper range boundaries than would be expected on the basis of decreasing precipitation. Also, riparian habitats within stream valleys extending westward from the Coastal Plain provide suitable habitats for trees in the dry regions of the Great Plains. The presence of riparian trees in this region is determined largely by the presence or absence of groundwater conditions necessary for survival. For floodplain trees, then, it is primarily habitat—not climate—that determines the location of range boundaries.

Crop yield and nitrogen concentration with controlled release urea and split applications of nitrogen as compared to non-coated urea applied at seeding

Controlled release urea (CRU) has been shown to improve nitrogen fertilizer use efficiency in a number of production systems. However, the effectiveness of CRU will be strongly affected by the environmental conditions of the region. Research trials were conducted at five locations across four major ecoregions spanning 1600km across the Northern Great Plains and Pacific Maritimes of North America from 2004 to 2006 to evaluate the effects of a single application of polymer-coated urea (CRU) or split applications of urea fertilizer as compared with non-coated urea for their effects on crop growth, crop N concentration, and crop N accumulation of wheat (Triticum aestivum L.), barley (Hordeum vulagre L.) canola (Brassica napus L.) and corn (Zea mays L.) across a wide range of environmental conditions. Urea applied as an in-soil band at the time of seeding was generally as or more effective than similarly placed CRU, split application of urea or blended urea and CRU in the semi-arid Mixed Grassland, moist Aspen Parkland or wet Boreal Transition ecoregions in increasing early season dry matter yield and seed or grain yield of canola, wheat or barley. Similarly, broadcast urea was as or more effective than broadcast CRU, split applications or blended applications in increasing corn dry matter yield under the wet conditions in the Lower Mainland ecoregion. There were some situations where use of split applications or use of the CRU in a blend with the non-coated urea resulted in increases in grain yield as compared to the non-coated urea, primarily under moist conditions in the Boreal Transition or Aspen Parkland ecoregions. Some yield losses occurred from use of the CRU as compared with the non-coated urea and were attributed to delays in release of N from the granule that limited early season N availability and crop growth, especially in corn with a high N demand. Effects on grain N concentration and accumulation of N in the crop at harvest were mixed, with the CRU, blended applications of CRU and urea or split applications occasionally producing higher grain N concentration and N accumulation in the crop than the non-coated urea. Benefits of CRU on grain N concentration were more frequent than benefits on grain yield, but were not large or consistent. Response of crop growth and N uptake to N management was generally similar under CT and RT, with occasional differences occurring due to changes in yield potential or N deficit associated with the differences in tillage management. Therefore, under growing conditions across a wide range of ecoregions in the Northern Great Plains and the Pacific Maritimes, the use of CRU or split applications do not appear to provide a consistent improvement in crop yield, N concentration in the grain, total N accumulation at harvest, or nitrogen use efficiency as compared to standard regional timing and placement of non-coated urea.

Does the stress tolerance of mixed grassland communities change in a future climate? A test with heavy metal stress (zinc pollution)

Will species that are sensitive/tolerant to Zn pollution still have the same sensitivity/tolerance in a future climate? To answer this question we analysed the response of constructed grassland communities to five levels of zinc (Zn) supply, ranging from 0 to 354 mg Zn kg −1 dry soil, under a current climate and a future climate (elevated CO 2 and warming). Zn concentrations increased in roots and shoots with Zn addition but this increase did not differ between climates. Light-saturated net CO 2 assimilation rate ( A sat) of the species, on the other hand, responded differently to Zn addition depending on climate. Still, current and future climate communities have comparable biomass responses to Zn, i.e., no change in root biomass and a 13% decrease of above-ground biomass. Provided that the different response of A sat in a future climate will not compromise productivity and survival on the long term, sensitivity is not altered by climate change.

Estimating aerodynamic roughness (zo ) in mixed grassland prairie with airborne LiDAR

In this research note we show that airborne imaging light detection and ranging (LiDAR) is capable of estimating the aerodynamic roughness height (zo ) in a mixed grassland prairie. This is accomplished by establishing empirical relations between wind profile derived estimates of zo and vegetation height measurements from the airborne LiDAR data. We show that up to 65% of the variation of zo can be explained by LiDAR estimates of vegetation height and that up to 76% of the variation can be explained by the height variability of vegetation. We also show the effects of different filter sizes used to identify the ground surface and the top of the vegetation in the LiDAR point cloud data. Overall, results from this investigation are encouraging for future spaceborne LiDAR missions, especially in terms of the potential for providing new insight on spatial and temporal patterns of zo .

Altered response to nitrogen supply of mixed grassland communities in a future climate: a controlled environment microcosm study

Few studies have investigated whether responses to nutrient supply of mixed plant communities change under combined elevated CO2 and climate warming. In this study we analyzed the response of constructed temperate grassland communities to five levels of nitrogen (N) supply, ranging from 0 to 150 kg N ha−1, under two climate scenarios. Biomass of the plant communities responded positively to N supply in the current climate, but was insensitive to N supply in the future climate. This altered response was not the result of a changing response from a single species, but all species seemed to contribute to it. The weaker response in the future climate was caused by changes in N uptake rather than by changes in nitrogen use efficiency, as community N stocks showed the same response pattern as community biomass. Climate change apparently modified the relation between fertilizer N addition and plant available N.

Investigating vegetation biophysical and spectral parameters for detecting light to moderate grazing effects: a case study in mixed grass prairie

AbstractIdentifying effective vegetation biophysical and spectral parameters for investigating light to moderate grazing effects on grasslands improves management practices on grasslands. Using mixed grasslands as a case study, this paper compares responses of vegetation biophysical properties and spectral parameters derived from satellite images to grazing intensity, and identifies the suitable biophysical and spectral parameters to detect grazing effects in these areas. Biophysical properties including cover, canopy height and Leaf area index (LAI) were measured in three sites with different grazing managements and one benchmark site in 2008 and 2009 in Grasslands PlaceTypeNational Park and surrounding provincial pastures, Canada. Thirteen vegetation spectral indices, calculated by statistically combining different spectral information, were evaluated. The results indicate that canopy height and the ratio of photosynthetically active vegetation cover to non-photosynthetically active vegetation cover (PV/NPV) showed significant differences between ungrazed and grazed sites. All spectral vegetation indices except the canopy index (CI) show significant differences between grazing treatments. Red-Near infrared (Red-NIR) based vegetation indices, such as Modified Triangular Vegetation Index 1 (MTVI1), Soil-adjusted Vegetation Index (SAVI), are significantly correlated to the PV/NPV. Green/Mid-infrared (Green/MIR) related vegetation indices, i.e. Plant Senescence Reflectance Index (PRSI) and Normalized Canopy Index (NCI), show significant correlation with canopy height. Models based on a linear combination of MTVI1 and SAVI were developed for PV/NPV and PRSI and NCI for canopy height. Models that simulated PV/NPV and canopy height show significant correlations with grazing intensity, suggesting the feasibility of remote sensing to quantify light to moderate grazing effects in mixed grasslands.

A suitable vegetation index for quantifying temporal variation of leaf area index (LAI) in semiarid mixed grassland

Determining a suitable vegetation index (VI) is important for accurately quantifying temporal variation in leaf area index (LAI) in semiarid mixed grassland where performances of VI are highly influenced by complex canopy composition, large amounts of dead vegetation, and bare soil. This study investigates the effects of canopy composition on LAI, evaluates the performances of 16 hyperspectral VIs on LAI estimation at each growing stage, and documents the sensitivity of the VIs to green vegetation and the resistance to dead vegetation and bare soil. Finally, the most suitable VI for quantifying LAI temporal variation is determined. The results indicate that dead vegetation accounts for more variation in LAI than does green vegetation. The study also shows that performances of ratio-based, chlorophyll-independent, soil-line-litter-corrected (L-ATSVI), and soil-line-related VIs are more reliable and stable than chlorophyll-corrected VIs and atmospheric resistant vegetation index (SARVI). Normalized difference vegetation index (NDVI), standardized LAI determining index (SLAIDI), and transformed soil-adjusted vegetation index (TSAVI) are the optimum VIs for LAI estimations in the early, maximum, and late growing seasons, respectively. NDVI is the most suitable VI for quantifying temporal variation in LAI during the entire growing season.

Seedling establishment of late colonizer is facilitated by seedling and overstory of early colonizer in a post-mined peatland

The seedling establishment of late colonizer may be promoted in the environments created by the early colonizer without interspecific seedling competition. To confirm the hypothesis, seed-sowing experiments were conducted in a post-mined peatland, northern Japan. Seeds on three grasses (Rhynchospora alba, Moliniopsis japonica and Phragmites australis) were sown in four vegetation sites: bareground, R. alba grassland, M. japonica grassland, and grassland mixed with three examined species. R. alba is the earliest colonizer, and M. japonica and P. australis are the later ones. Seedling emergence, survival, growth and resource allocation were monitored for two growing seasons. The seedling emergence of all the species was lowest on bareground. The emergence of R. alba and P. australis was high in R. alba and mixed grasslands, but was low in M. japonica grassland. M. japonica seedlings emerged more in vegetation with moderate plant cover and litter. R. alba seedlings yielded the highest biomass on bareground, and the biomass decreased with increasing shading. R. alba did not change resource allocation of height to above-ground biomass between vegetation types. The seedling biomass of M. japonica was affected little by shading, probably because M. japonica adjusted resource allocation with shading. In the two summers, R. alba and M. japonica seedlings survived more when the neighboring seedlings emerged more. P. australis seedlings failed in overwintering. The seedling characteristics of each species explained the species replacement, i.e., R. alba invaded bareground and facilitated the establishment of late colonizer, M. japonica, by the shelter effects of the overstory and seedling.

Influence of plant species and soil conditions on plant–soil feedback in mixed grassland communities

Summary 1. Our aim was to explore plant–soil feedback in mixed grassland communities and its significance for plant productivity and community composition relative to abiotic factors of soil type and fertility. 2. We carried out a 4‐year, field‐based mesocosm experiment to determine the relative effects of soil type, historic management intensity and soil conditioning by a wide range of plant species of mesotrophic grassland on the productivity and evenness of subsequent mixed communities. 3. The study consisted of an initial soil conditioning phase, whereby soil from two locations each with two levels of management intensity was conditioned with monocultures of nine grassland species, and a subsequent feedback phase, where mixed communities of the nine species were grown in conditioned soil to determine relative effects of experimental factors on the productivity and evenness of mixed communities and individual plant species performance. 4. In the conditioning phase of the experiment, individual plant species differentially influenced soil microbial communities and nutrient availability. However, these biotic effects were much less important as drivers of soil microbial properties and nutrient availability than were abiotic factors of soil type and fertility. 5. Significant feedback effects of conditioning were detected during the second phase of the study in terms of individual plant growth in mixed communities. These feedback effects were generally independent of soil type or fertility, and were consistently negative in nature. In most cases, individual plant species performed less well in mixed communities planted in soil that had previously supported their own species. 6. Synthesis. These findings suggest that despite soil abiotic factors acting as major drivers of soil microbial communities and nutrient availability, biotic interactions in the form of negative feedback play a significant role in regulating individual plant performance in mixed grassland communities across a range of soil conditions.

Soil NO 3-leaching during growth of three grass–white-clover mixtures with mineral N applications

The effect of sward composition and grass species richness on soil NO 3-leaching following the application of mineral N was tested on a very rapidly draining soil in a cool humid climate 2007 and 2008. The factorial split-plot experiment used NH 4NO 3 at three rates in three split applications to three different mixtures of white clover ( Trifolium repens), timothy ( Phleum pratense), blue grass ( Poa pratensis), meadow fescue ( Festuca pratensis), and reed canary ( Phalaris arundinacea). Grass–clover composition of the sward induced two effects on NO 3-leaching from the soil following the application of mineral N. Apparent fertilizer N replacement by white clover increased NO 3-leaching while blue grass proportion reduced NO 3-leaching. Summer application of mineral N amplified the phenological asynchrony between white clover and cool season species, like timothy, in the N cycle of mixed grassland. An increase of the number of grass species from two to four did not reveal any N-conserving effect that could be attributed to species richness.

Do grazer hair and faeces reflect the carbon isotope composition of semi-arid C3/C4 grassland?

The carbon isotope composition (δ13C) of C3/C4 mixed grassland is reflected in the δ13C of diet, hair or faeces of grazers, if 13C discrimination (13Δ) between grassland vegetation and these tissues is known and constant. However, these relationships could be modified by selective grazing or differential digestibility of the C3 and C4 components, potentially creating a bias between grassland and grazer tissue δ13C. Importantly, these factors have never been studied in detail. We investigated the relation between δ13C of C3/C4 grassland vegetation and that of faeces and hair of sheep in a 3-year (2005–2007) experiment in the Inner Mongolian semi-arid steppe. The experiment employed six stocking rates (0.375–2.25 sheep ha−1 year−1; four replications), which allowed for a large variation in species composition, digestibility, and diet selection. Faecal-nitrogen content, a proxy for digestibility, decreased from 1.9% to 1.5% during the grazing period due to aging of the herbage. At the same time, the C3/C4 ratio decreased due to the later growth initiation of C4 species. 13Δ between diet and faeces (13ΔDF; 0.6‰) and between diet and hair (13ΔDH; −3.9‰) were not influenced by stocking rate, period in the season or C3/C4 ratio. Moreover, faeces–hair discrimination (13ΔFH; −4.3‰), which reflects differences between digestibility of the C3 and C4 components, did not vary along the different gradients. The δ13C of grassland vegetation can be estimated from the δ13C of sheep faeces and hair, provided that 13Δ was accounted for. This is useful for landscape- or regional-scale investigations or reconstruction of C3/C4 vegetation distribution from faeces and hair, which provide different temporal and spatial integration of grassland isotope signals. Die Kohlenstoff-Isotopenzusammensetzung (δ13C) von C3/C4 Grasland widerspiegelt sich im δ13C des Futters, der Haare sowie des Kots von Weidetieren, sofern die 13C-Diskriminierung (13Δ) zwischen der Vegetation und dem jeweiligen Tierparameter bekannt und konstant ist. Unterschiedliche Verdaulichkeiten der C3 und C4 Komponenten, oder selektiver Fraß können jedoch 13Δ verändern und somit zu Fehlern bei der Schätzung des δ13C von Grasland führen. Diese Zusammenhänge wurden bisher noch nicht systematisch untersucht. In der vorliegenden Studie untersuchten wir deshalb die Beziehung zwischen dem δ13C von gemischtem C3/C4 Grasland und dem Kot und den Haaren von Schafen. Die Studie wurde in einem mehrjährigen Beweidungsexperiment (2005–2007) mit sechs verschiedenen Besatzdichten (0.375 bis 2.25 Schafe pro ha, vier Wiederholungen) in der semi-ariden Steppe der Inneren Mongolei durchgeführt. Dieses Versuchsdesign ermöglichte eine große Variation der Artenzusammensetzung, der Verdaulichkeit und der Futterselektion. Der Kotstickstoffgehalt (ein Maß für die Verdaulichkeit) sank während der Weideperiode von 1.9% auf 1.5%. Dieser Effekt beruhte auf der Alterung des Pflanzenbestandes. Gleichzeitig nahm das C3/C4-Verhältnis durch den späteren Austrieb der C4 Arten ab. Die 13Δ zwischen Futter und Kot (13ΔDF; 0.6‰) und zwischen Futter und Haar (13ΔDH; −3.9‰) war unabhängig von der Besatzdichte, dem Zeitpunkt innerhalb der Weideperiode und dem C3/C4-Verhältnis. Des Weiteren wurde die Kot-Haar Diskriminierung (13ΔFH; −4.3‰) – ein Maß für Verdaulichkeitsunterschiede zwischen C3 und C4 Arten – ebenfalls nicht von den verschiedenen Gradienten beeinflusst. Diese Untersuchungen zeigen, dass das δ13C von C3/C4 Grasland in der Inneren Mongolei aus dem δ13C von Kot oder Haaren bestimmt werden kann, sofern die (konstante) 13Δ berücksichtigt wird. Diese Ergebnisse sind besonders für lokale und regionale Untersuchungen, bzw. die Rekonstruktionen des C3/C4-Verhältnisses nützlich, da Kot und Haare Isotopensignale über (unterschiedlich lange) räumlich-zeitliche Skalen integrieren.