积雪变化对陆地生态系统植被特征和土壤碳氮过程的影响

在季节性积雪地区，冬季气候变暖导致积雪变薄、积雪不连续、融雪提前及雪盖面积缩小等现象。然而相较于氮沉降、增温、降水变化等全球变化因子，目前尚缺乏积雪因子对陆地生态系统过程和功能影响的系统报道。为加深人们对积雪特征变化生态后果的认知，综述了积雪深度和融雪时间变化对植被物候和群落组成、凋落物分解、土壤碳氮过程、温室气体排放和土壤微食物网(土壤动物和微生物)的影响。由于模拟积雪变化手段不同和复杂的气候、土壤背景，生态系统各要素对积雪特征变化的响应规律存在较大的分异和不确定性。例如，在未来气候变暖导致积雪变薄和融雪提前情景下，植被物候提前，生长季延长，导致生产力增加和凋落物数量增加，禾草比例减少导致凋落物质量增加，早春温度高刺激微生物活性，凋落物分解速率高，促进土壤碳氮周转过程。但积雪减少和融雪提前导致的早春低温和夏季干旱也可能引起植被生产力下降，凋落物数量减少质量降低，土壤微生物活性低，分解速率低，从而减缓碳氮周转过程。此外，积雪特征变化对植被特征和土壤碳氮过程影响相关研究目前还存在以下问题：1)积雪深度和融雪时间对生态系统的影响是否存在交互效应仍缺乏关注，且积雪变化对后续生长季是否存在持续...

Impact of changes in snow cover characteristics on plant community and soil carbon and nitrogen processes

In seasonally snow-covered ecosystem, warmer winters lead to shallow and discontinuous snow packs, accompanied by the earlier snow melting and the declining snow-cover extent. However, compared to the other global changes, such as nitrogen deposition, global warming and precipitation variations, the impacts of snow cover changes on terrestrial ecosystem functions and processes are still unclear. To deepen our understandings on the ecological consequences of the changes in snow cover regime, we summarized the effects of snow cover depth and snow-melting time on plant community composition, litter decomposition, soil carbon and nitrogen pool dynamics, greenhouse gas production/consumption processes, and soil micro-food web (fauna and microorganisms). It was found that, due to the diverse methods simulating snow cover changes and the distinct climate and soil contexts in each individual case, the published observations are conflict and have no general conclusions. For example, under the scenarios of climate warming, shallow snow-cover and earlier snow melting will induce earlier plant phenology, and thus, higher plant productivity and more plant litter. Decreased proportion of grasses in the community will increase the litter quality. The higher temperature in earlier spring will increase the activity of soil microorganisms and litter decomposition rates, which consequently accelerate the carbon and nitrogen turnover processes. In contrast, shallow snow-cover and earlier snow melting might also decrease plant productivity and litter quantity because of low temperature and increased freeze-thaw cycles. The earlier spring drought will decrease the litter quality and microbial activity, and thus, decelerate the carbon and nitrogen cycling processes. The other problems relevant to the research on the impact of snowpack changes on the functions and processes of terrestrial ecosystems include:1) whether there are interactive effects of snow depth and snowmelt time on the ecosystem, and whether the impacts of snow cover changes will last to growing season are not yet fully concerned; 2) the effects of snow cover depth and snow-melting time on plant community composition, litter decomposition, soil carbon and nitrogen dynamics, and soil organisms are studied independently; 3) the underlying microbial mechanism driving soil biogeocycling processes under snow cover changes are still unclear, in particular, lacking genomic supporting data; 4) remote sensing has been rarely applied to inverting various snow parameters relevant to terrestrial ecosystem functions and processes. Thus, we highlighted the importance to strengthen the research on the ecological linkages between plant community, soil carbon and nitrogen processes, and soil micro-food web, soil microbial community composition and function based on genomic analysis, and the application of remote sensing technology, aiming to provide reference for the development of snowpack ecology.