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Plant growth and development are closely related to water availability. Water deficit and water excess are detrimental to plants, causing a series of damage to plant morphology, physiological and biochemical processes. In the long evolutionary process, plants have evolved an array of complex mechanisms to combat against stressful conditions. In the present study, the duration-dependent changes in ascorbate (AsA) and glutathione (GSH) contents and activities of enzymes involved in the AsA-GSH cycle in hairgrass (Deschampsia caespitosa) in response to water stress was investigated in a pot trial using a complete random block design. The treatments were as follows: (1) heavily waterlogging, (2) moderate waterlogging, (3) light waterlogging, (4) light drought, (5) moderate drought, (6) heavily drought, and (7) a control (CK) with plant be maintained at optimum water availability. The hairgrass plants were subjected to waterlogging or drought for 7, 14, 21 and 28 days and data were measured following treatment. Results revealed that hairgrass subjected to water stress can stimulate enzymatic activities of ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and L-galactono-1, 4-lactone dehydrogenase (GalLDH), switched on the ascorbate-glutathione (AsA-GSH) cycle and the L-galactose synthesis, up-regulated the contents of AsA and GSH, and maintained higher ratios of ascorbate to dehydroascorbate (AsA/DHA) and reduced glutathione to oxidized glutathione (GSH/GSSG) to alleviate potential oxidative damage. However, the light waterlogging did not induce hairgrass under stress to switch on the AsA-GSH pathway. In general, the critic substances and enzyme activities in AsA-GSH metabolic pathway increased as the increase of water stress intensity. As the increase of exposure duration, the critic antioxidant substances content and enzyme activities increased first and then maintained a relatively stable higher level. Our findings provide comprehensive information on biochemical responses of hairgrass to hydrological change, which would be a major step for accelerating ecological restoration of degradation alpine marshes in the Qinghai-Tibetan Plateau.

In addition to improving vegetation, grazing prohibition changes the soil micro-environment. Soil enzymes and microbes, which are the chief constituents responsible for mediation of most of the processes involved in energy and material fluxes of ecosystems, are very sensitive to changing environments. This study aimed to illustrate the effects of grazing prohibition on vegetation and soil enzyme characteristics, and to elucidate the responses of soil fungal and bacterial function and community composition on grazing prohibition for 10 years in a Qinghai-Tibetan alpine meadow. About 6 hm2 lightly degraded alpine meadows were selected in 2006, and half of which were fenced to completely prohibit grazing throughout the year, while the other half were subjected to free yak grazing. Four different plots in each site were selected as experimental fields in 2016. Soil microbial characteristics were analyzed by high-throughput gene detection. Grazing prohibition had no significant impact on vegetable Shannon-Wiener diversities or below-ground biomass, but dramatically changed the above-ground biomass and soil phosphatase activity. In the Qinghai-Tibetan alpine meadow, bacteria are dominant members of the soil microbial community. Grazing prohibition significantly increased the fungal species diversity and the abundance of pathotrophs, saprotrophs and symbiotrophs, while it had no effect on soil bacterial diversity and functional structure. A total of 100.0% of the variations in fungi and bacteria could be explained by plant variables. The reciprocal action among plant biomass (i.e. above-ground biomass, below-ground biomass), plant diversities (i.e. Shannon-wiener diversity, species number, coverage) and species important value have a great impact on soil microbial composition variations. Long-term grazing prohibition restrained the phosphatase activity and increased the abundance of pathotrophic fungi but had no effect on the abundance of functional bacteria, which participate in the soil biogeochemistry cycling process. Grazing prohibition for 10 years did not improve the community structure of functional microorganisms related to carbon, nitrogen and sulfur, and appropriate grazing could maintain the sustainable utilization of grassland resources.

Alpine meadow is a major vegetation community on the Qinghai-Tibetan Plateau,China.Kobresia parva alpine meadow is regarded as one of the forage bases for yak production because of its high content of proteins,fats and carbohydrates.However,the alpine meadow vegetation degraded as overstocking.Therefore,it is important to study the effects of yak-grazing on Kobresia parva alpine meadow community.In this study,above-and below-ground biomass and their allocation,absolute growth ration,and influence of grazing intensity on compensatory effect of different plant groups were investigated,based on yaks grazing trial for 2 years in Kobresia parva meadow.Our results showed that total above-ground biomass followed a decreasing trend with the increase of grazing intensity.And,the total above-ground biomass showed a significant differences in the warm-season grazing pasture(P0.01),but not in the cold-season grazing pasture(P0.05) among grazing intensity.With the increased grazing intensity,the below-ground biomass for different soil depth appeared significantly decreasing trend in both the warm-and the cold-season grazing pastures,and there was significant difference for below-ground biomass of each soil depth in the warm-season grazing pasture(P0.05),but not in the cold-season grazing pasture(P0.05) among different grazing intensities.Moreover,the rate of below-ground biomass to above-ground biomass decreased along the increasing of grazing intensity in the cold-season grazing pasture,but,the rate of below-ground biomass to above-ground biomass in the control plot was less than that in the light and moderate grazing plots,and it was higher than that in the heavy grazing plot in the warm-season grazing pasture.Additionally,the over-compensatory growth was existed in the different plant groups for each grazing intensity in the warm-season grazing pasture.Meanwhile,the over-compensatory growth of Cyperaceae and Gramineae plant groups appeared in August,but it appeared in June and July for forbs plant group.Moreover,the compensatory effect of Gramineae plant groups was higher than that of Cyperaceae plant group and forbs plant group.The compensatory effects were more significant in the light and moderate grazing intensities.Theover-compensatory growth also appeared for different plant groups in the cold-season grazing pasture,but the compensatory effect was non-significant.So,our results suggested that the modest grazing(the light and moderate grazing) would be beneficial to bring over-compensatory growth in the warm-season grazing pastures,and the heavy grazing would bring potentially disadvantage for vegetation stabilization in studied Kobresia parva meadow.