Spatial pattern of C:N:P stoichiometry characteristics of alpine grassland in the Altunshan Nature Reserve at North Qinghai-Tibet Plateau

Abstract Carbon (C), nitrogen (N) and phosphorus (P) are the most important elemental components of an ecosystem. Nutrient stoichiometry reflects their cycling and distribution with ecosystems. The changes in nutrient stoichiometry in different ecosystems are not consistent. The altitudinal gradient within the Altunshan Nature Reserve can be used as a natural experiment to verify the effect of different altitudes gradients on nutrients changes. Therefore, we studied the changes in plant and soil nutrients from alpine desert ecosystem to alpine grassland ecosystem in this region. The results showed that there was a linear correlation for plant C, N and P, as well as soil C and N with altitude gradient. The C: N and C: P of plants and C: P and N: P of soils were linearly correlated with the elevation gradient. Plant C and N were mainly affected by soil C and N content, but there was no significant correlation between plant P and soil nutrient concentration. Soil nutrients were affected by soil moisture content and pH. Soil moisture content increased gradually with altitude, promoting nutrient mineralization and availability to the ecosystem. The increase of soil nutrient availability and soil water content significantly increased the species diversity, promoting the plant community assembly and the succession from alpine desert ecosystem to alpine grassland ecosystem. This study analyzed the relationship between nutrient cycling and distribution in different ecosystem types on the Qinghai-Tibet Plateau and found that nutrient changes were greatly affected by soil moisture in the arid and cold regions.