Microorganisms play a key role in maintaining the stability of vegetation-soil-microbial systems and terrestrial geochemical processes in alpine meadows. To investigate the effects of different management practices on the structure and function of microbial communities, the present study used metagenomic sequencing to investigate the structure and function of soil microbial communities in the southern Qilian Mountains of the Qinghai-Xizang Plateau in response to the management practices of fenestration (FE), winter grazing (WG), transition zone between natural and artificial grasslands (TZ), and artificial unicast oats (AU). The management measures significantly changed vegetation diversity and soil physicochemical properties. The prokaryotic community structure was considerably similar in FE and WG, as well as in TZ and AU. Near-natural (FE) and artificial establishment (AU) disturbances changed the fungal community structure. Enzymes related to carbon metabolism did not respond significantly to the management measures, whereas those related to nitrogen metabolism did not respond significantly in TZ and AU. The relative abundance of enzymes involved in nitrogen metabolism was higher under TZ and AU than under FE and WG. We concluded that grassland management measures altered the structure of aboveground graminoid and leguminous vegetation communities and belowground biomass allocation, resulting in changes in K uptake, causing significant changes in the structure of fungal communities and nitrogen-metabolizing enzymes; moderate disturbance (WG) was beneficial for maintaining the stability of microbial communities in alpine grasslands.

The cultivation of artificial grassland, which requires regular sowing and harvesting, is an important and common practice in grassland management and restoration on the Qinghai-Tibetan Plateau (QTP). However, the key factors and successional processes that determine its interannual variability of net ecosystem exchange (NEE) remains unclear. In this study, we analyzed 6 years of eddy covariance observations, quantified seasonal and annual NEE, net carbon uptake period length (CUP), two largest carbon emission periods length (CEPs), and daily minimum and maximum NEE (NEEmin, NEEmax) responses to management measures in an alley silvopasture system with planted Elymus nutans on the QTP. We examined NEE variations before and after sowing and harvesting and investigated how sowing and harvesting managements affect NEE. The five-year life cycle study revealed that this artificial perennial grassland was a weak net carbon sink with an uptake of -180 g C m–2 per plant cycle (2012–2016). Inter-annual variations in NEE was determined by CUP and the first largest carbon emission periods (CEP1). Sowing delayed the beginning of CUP (BCUP) by about 42 days and caused spring C uptake to decline by -36 g C m–2. In contrast, harvesting caused the ending of CUP (ECUP) to advance about 25 days, and caused a decease of autumn C uptake about -33 g C m–2. Sowing and harvesting shortened the CUP and extended the CEP1, which reduces the carbon sequestration potential of the artificial grassland. Based on our results, we recommend that policy makers and authorities consider the effect of timing of sowing and harvesting on C sequestration. Our results provide a new insight for grassland management and the inter-annual variability of NEE on climate mitigation and regional sustainability.