青藏高原高寒草原生态系统土壤碳氮比的分布特征

利用67个样点数据,研究了青藏高原高寒草原生态系统土壤碳氮比的分布特征。结果表明:(1)在水平方向上,土壤碳氮比呈现出西北高、东南低的总体态势和斑块状交错分布的格局,碳氮比的高值区主要集中在藏北高原腹地和喜马拉雅山北麓湖盆区,不同草地型和不同自然地带土壤碳氮比差异显著;(2)土壤剖面自上而下,不同草地型碳氮比可分为低-高-低型、由高到低型、由低到高型、高-低-高-低型和高-低-高型等5个类型。表土层(0—20 cm)与底土层(30—40 cm)土壤碳氮比差异显著;(3)土壤碳氮比与与最冷月均气温、年均蒸发量、年均相对湿度和土壤全氮含量呈极显著正相关关系,而与年均日照时数、年均气温、速效钾含量呈极显著负相关关系,这些环境因素对土壤碳氮比影响从大到小的顺序是年均相对湿度年均日照时数最冷月均气温年均气温年均蒸发量土壤全氮含量土壤速效钾含量。

Soil C/N distribution characteristics of alpine steppe ecosystem in Qinhai- Tibetan Plateau

Regional distribution regularities on soil C/N have been a hot topic in recent years, but currently there were few studies reporting the soil C/N distribution in alpine steppe ecosystem under different vegetation zones in Qinhai-Tibetan plateau. In order to reveal the spatial distribution characteristics of the soil C/N on the alpine steppe ecosystem in different vegetation zones, and to provide scientific basis for understanding a regional specific acclimation of vegetation to climate change in Qinhai-Tibetan plateau, we surveyed the soil C/N of alpine steppe ecosystem under different vegetation zones. Collectively, we sampled 67 sampling points. The soil C/N of the alpine steppe ecosystem in Qinhai-Tibetan plateau was also compared with that of 14 natural transects in areas outside the plateau. The results showed that: (1) Along the horizontal direction in Qinhai-Tibetan plateau, C/N appeared higher in northwest and lower in southeast. The higher C/N appeared mainly in the regions with a concentration in the hinterland of northern part of Tibetan Plateau and in the lake basin region of the northern foot of Himalayas. There were significant differences of C/N among different grassland types and natural transects. (2) Along the vertical direction of the soil profiles from aboveground to underground, it could be divided into 5 types of low-high-low, from high to low, from low to high, high-low-high-low and high-low-high of C/N distribution patterns among different grassland types and natural transects, and there was significant difference of C/N between the surface soil depths from 0 cm to 20 cm and the deeper soil depths from 30 cm to 40 cm. (3) C/N was significantly and positively correlated with average temperature in the coldest month, average annual evaporation, average annual relative humidity and soil total nitrogen content, respectively. The C/N was significantly correlated with average annual sunshine hours, average annual temperature and soil available K content negatively, respectively. The effect magnitude of environmental factors on the C/N followed an order of average annual relative humidity > average annual sunshine hours > average temperature in the coldest month > average annual temperature > average annual evaporation > soil total nitrogen content > soil available K content. Due to the complex spatial distribution along both horizon and vertical directions, the research work of soil C and N and the relationship between C and N of the alpine steppe ecosystem in Qinhai-Tibetan plateau are highly important. Conclusively, climate is the most important environmental influence factor on the soil C/N of alpine steppe in Qinhai-Tibetan plateau. Future research work should focus on the relationship between soil C/N and climatic factor, especially the relationship between soil C/N and moisture factor.