Summary1. Arbuscular mycorrhizal fungi (AMF) can influence plant community composition and diversity. Previous research has shown that the addition of nutrients reduces the effectiveness of AMF. However, the ways in which soil nutrient availability and AMF interact and affect plant community productivity and ecosystem stability are still poorly understood. 2. We examined the impact of AMF suppression and phosphorus (P) addition on plant diversity, community productivity and temporal stability (TS) in a field experiment. AMF root colonization and the concentration of an AMF-specific phospholipid fatty acid were significantly reduced after application of the fungicide benomyl as a soil drench. 3. The TS of the plant community was higher in communities without benomyl application compared with communities with benomyl application indicating that AMF contribute to the TS of plant communities. AMF suppression increased productivity at the plant species, functional group and community levels under high P addition rates. At the zero P addition rate, AMF did not affect plant community productivity, as the dominant species Artemisia frigida was more abundant in control plots with AMF, while the subdominant species Stipa krylovii was more abundant in the benomyltreated plots with reduced AMF abundance. Compensatory effects between C 3 grasses and non-N 2 -fixing forbs were observed in the control plots with AMF along the gradient of P addition rates, but these effects were not detected among plant species in the benomyl-treated plots under AMF suppression above an addition rate of 4.76 P 2 O 5 m À2 year À1 . Although AMF suppression did not influence the diversity of the plant communities, it did decrease the diversity of N 2 -fixing forbs at the zero P addition rate and above an addition rate of 18.90 g P 2 O 5 m À2 year À1 , indicating that AMF play key roles in the maintenance of N 2 -fixing forbs at these P addition rates. P addition led to biodiversity losses at application rates below 2.36 g P 2 O 5 m À2 year À1 at the community level.4. Synthesis. Arbuscular mycorrhizal fungi and soil P availability interact to influence the productivity and TS of a plant community by mediating compensatory effects among plant species and functional groups.

Mutations in the X-linked gene encoding the transcriptional modulator methyl-CpG-binding protein 2 (MeCP2) impair postnatal development of the brain. Here we use neuronal-type specific gene deletion in mice to show that conditional Mecp2 deletion in GABAergic parvalbumin-expressing (PV) cells (PV-Mecp2 À /y ) does not cause most Rett-syndrome-like behaviours, but completely abolishes experience-dependent critical period plasticity of primary visual cortex (V1) that develops normal visual functions. However, selective loss of Mecp2 in GABAergic somatostatin-expressing cells or glutamatergic pyramidal cells does not affect the critical period plasticity. MeCP2-deficient PV cells exhibit high intrinsic excitability, selectively reduced efficacy of recurrent excitatory synapses in V1 layer 4 circuits, and decreased evoked visual responses in vivo. Enhancing cortical gamma-aminobutyric acid (GABA) inhibition with diazepam infusion can restore critical period plasticity in both young and adult PV-Mecp2 À /y mice. Thus, MeCP2 expression in inhibitory PV cells during the critical period is essential for local circuit functions underlying experiencedependent cortical plasticity.

The potential of grazing lands to sequester carbon must be understood to develop effective soil conservation measures and sustain livestock production. Our objective was to evaluate the effects of grazing on soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC) in Typical steppe and Desert steppe ecosystems, which are both important grassland resources for animal grazing and ecological conservation in China, and to derive region-specific soil C changes associated with different stocking rates (ungrazed, UG; lightly grazed, LG; moderately grazed, MG; heavily grazed, HG). This study substantiated that significant higher SOC, TN and MBC appeared with the treatment of LG in typical steppe. From 2004 to 2010, grazing treatments increased soil carbon storage in desert steppe, which was partly due to the grazing history. The higher MBC concentration and MBC/SOC suggest a great potential for carbon sequestration in the desert steppe ecosystem. The greater MBC in desert steppe than typical steppe was mainly the result of higher precipitation and temperature, instead of soil substrate. The change of MBC and the strong positive relationships between MBC and SOC indicated that MBC in the soil was a sensitive index to indicate the dynamics of soil organic carbon in both steppes in Inner Mongolia of China.

No abstract