Summary1. The Eurasian steppe has long been subject to grazing by domestic ungulates at high levels, resulting in widespread deterioration of biodiversity and ecosystem services. While abundant evidence demonstrates that heavy grazing alters the ecosystem structure and function of grasslands, research on how grazing specifically affects ecosystem functioning and stoichiometry on broad scales is scarce because of a lack of adequate ungrazed reference sites. 2. We examined the effects of grazing on ecosystem functioning and C : N : P stoichiometry across a precipitation gradient along the 700 km China-Mongolia transect (CMT), covering three community types: meadow steppe, typical steppe and desert steppe. 3. Long-term grazing has dramatically altered the C, N and P pools and stoichiometry of steppe ecosystems along the CMT. Grazing reduced the C, N and P pools in above-ground biomass and litter, while the responses in below-ground biomass and soil C, N and P pools to grazing differed substantially among community types. 4. Grazing increased N content and decreased C : N ratios in all plant compartments, suggesting accelerated N cycling. The altered C : N : P stoichiometry may be explained by changes in the composition of species and functional groups as well as increased foliar N and P contents for the same species in grazed communities. 5. Synthesis and applications. Plant stoichiometric responses to grazing ranged from large in the meadow steppe to small in the typical steppe to generally insignificant in the desert steppe, implying that different underlying mechanisms operated along the regional precipitation gradient. Our findings suggest that reducing the stocking rate and restoring the vastly degraded steppes are essential to sustain native steppe biodiversity, ecosystem functioning and biological capacity for mitigating the impact of climate change in the Inner Mongolia grassland.

Summary 1.Understanding the productivity-diversity relationship (PDR) is a key issue in biodiversity-ecosystem functioning research, and has important implications for ecosystem management. Most studies have supported the predominance of a humpshaped form of PDR in which species richness peaks at an intermediate level of productivity. However, this view has been challenged recently on several grounds. 2. Based on data from 854 field sites across the Inner Mongolia region of the Eurasian Steppe, we tested the form of PDR at different organizational levels (association type, vegetation type and biome) and multiple spatial scales (local, landscape and regional). 3.Our results showed that a positive linear, rather than hump-shaped, form was ubiquitous across all organizational levels and spatial scales examined. On the regional scale, this monotonic PDR pattern corresponded closely with the gradient in mean annual precipitation (MAP) and soil nitrogen. Increasing species dissimilarity with productivity could also contribute to the positive linear form of PDR. 4. Our results also indicated that grazing decreased both primary productivity and species richness but, intriguingly, not the form of PDR. Synthesis and applications.This study provides the first direct test of the productivitydiversity relationship for the world's largest contiguous terrestrial biome -the Eurasian Steppe. The predominance of a positive linear relationship in this region defies the commonly held view that a unimodal form of PDR dominates terrestrial ecosystems, supported mainly by studies in Africa, Europe and North America. It suggests that precipitation has a greater control on the productivity-diversity relationship in the Eurasian Steppe than grasslands elsewhere. Also, the positive linear relationship is surprisingly robust to grazing. Our results provide new insight into the productivitydiversity relationship and have several implications for restoring degraded lands and understanding ecological consequences of climate change in the Eurasian Steppe.

1. The rapid loss of global biodiversity can greatly affect the functioning of above-ground components of ecosystems. However, how such biodiversity losses affect below-ground communities and linkages to soil carbon (C) sequestration is unclear. Here, we describe how losses in plant functional groups (PFGs) affect soil microbial and nematode communities and net ecosystem exchange (NEE) in a 4-year removal experiment conducted on the Mongolian plateau, the world's largest remaining natural grassland. 2. Our results demonstrated that the biomasses or abundances of most components of the two below-ground communities (microbes and nematodes) were negatively affected by PFG loss and were positively related to above-ground plant biomass. The removal of dominant PFGs (perennial bunchgrasses and perennial rhizomatous grasses) reduced the biomass or abundance of belowground community components while removal of less dominant PFGs (perennial forbs and annuals/biennials) did not change or increased the biomass or abundance of below-ground community components. 3. The biomass-based ratio of fungal to bacterial microbes and the number-based ratio of fungalfeeding to bacterial-feeding nematodes decreased with increasing PFG losses. Variation partitioning analyses showed that the identity of PFGs together with above-ground plant biomass explained most of the total variation in soil microbes and that the identity of PFGs and above-ground plant biomass together with nematode food resources explained most of the total variation in soil nematodes. The increase in NEE with PFG loss was mainly explained by decreases in above-ground plant biomass and the ratio of fungi to bacteria. 4. Synthesis. The shift of below-ground communities from a fungal-based to a bacterial-based energy channel as PFG richness decreases indicates that less diverse grassland ecosystems will have lower nutrient retention and hence be more sensitive to land-use or climate change. The dominant effects of above-ground plant biomass and below-ground communities on NEE indicate that PFG loss resulting from land-use or climate change has the potential to reduce C sequestration in semiarid grassland soils. These findings suggest that predictive models may need to consider the composition of above-ground and below-ground communities in order to accurately simulate the dynamics of CO 2 fluxes in terrestrial ecosystems.

Emergent intracoronary transplantation of bone marrow mononuclear cells after AMI is practicable, and it improved cardiac function, prevented myocardial remodelling and increased myocardial perfusion at six months' follow up.

Abstract.Understanding the impacts of biodiversity loss on ecosystem functioning and services has been a central issue in ecology. Experiments in synthetic communities suggest that biodiversity loss may erode a set of ecosystem functions, but studies in natural communities indicate that the effects of biodiversity loss are usually weak and that multiple functions can be sustained by relatively few species. Yet, the mechanisms by which natural ecosystems are able to maintain multiple functions in the face of diversity loss remain poorly understood. With a long-term and large-scale removal experiment in the Inner Mongolian grassland, here we showed that losses of plant functional groups (PFGs) can reduce multiple ecosystem functions, including biomass production, soil NO 3 -N use, net ecosystem carbon exchange, gross ecosystem productivity, and ecosystem respiration, but the magnitudes of these effects depended largely on which PFGs were removed. Removing the two dominant PFGs (perennial rhizomatous grasses and perennial bunchgrasses) simultaneously resulted in dramatic declines in all examined functions, but such declines were circumvented when either dominant PFG was present. We identify the major mechanism for this as a compensation effect by which each dominant PFG can mitigate the losses of others. This study provides evidence that compensation ensuing from PFG losses can mitigate their negative consequence, and thus natural communities may be more resilient to biodiversity loss than currently thought if the remaining PFGs have strong compensation capabilities. On the other hand, ecosystems without well-developed compensatory functional diversity may be much more vulnerable to biodiversity loss.

AimsWe sought to determine whether repeat administration of bone marrow mononuclear cells (BMC) can improve left ventricular function compared with a single infusion in patients with large acute myocardial infarction (AMI). Methods and resultsThirty-nine patients with a ST-elevation AMI of the anterior wall and a significantly decreased left ventricular ejection fraction (LVEF 20-39%) were randomly assigned to three groups following primary percutaneous coronary intervention: Group A (n ¼ 12) received a single intracoronary infusion of BMC (1.9 + 1.2 Â 10 8 ) at 3-7 days after AMI; Group B (n ¼ 15) received BMC administration both at 3-7 days (2.0 + 1.4 Â 10 8 ) and at 3 months (2.1 + 1.7 Â 10 8 ); and the control group (CON, n ¼ 12) received one placebo injection at 3 -7 days. We noted no severe complications associated with the BMC transfer. The increase in LVEF evaluated by magnetic resonance imaging (MRI) after 12 months in Group B (11.7 + 2.6%) was significantly greater than that in Group A (7.2 + 1.6%, P , 0.001) or in CON (2.9 + 2.0%, P , 0.001). Magnetic resonance imaging-derived myocardial infarct size decreased significantly in Group B compared with Group A (11.3 + 2.7% vs. 6.3 + 1.6%, P , 0.001). ConclusionData from this preliminary study suggest that repeated BMC administration might be a safe and feasible therapeutic strategy for patients with large AMI.--

In this study, soil respiration and environmental variables were examined to explore the temporal and spatial variability and controls of soil respiration in eight plant communities along an east–west transect in a temperate steppe of Inner Mongolia, China. Our results show that there was substantial temporal (coefficient of variation (CV) = 58.6 ± 1.54%, n = 14) and spatial variability (CV = 32.6 ± 2.65%, n = 8) in soil respiration. Soil temperature and moisture were more important than plant growth in controlling the seasonal patterns of within‐site soil respiration in all the eight steppe communities. Spatial differences in soil respiration rate could be mainly attributed to the differences in soil moisture and net primary productivity (NPP) among the study sites, whereas soil temperature played a minor role in regulating the spatial pattern of soil respiration. Significantly, positive site‐to‐site correlations were found between soil respiration and site soil traits such as soil C, N, and clay contents. In contrast, soil respiration was negatively correlated with soil bulk density and sand content. These findings indicate that the relative importance of abiotic and biotic factors in regulating soil respiration differs temporally from spatially. The conclusions drawn from the present study provide valuable information for developing future models of soil respiration driven by site climatic and soil variables, applicable for large‐scale estimates of soil respiration in grassland ecosystems.

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