Spatial variability of soil carbon, nitrogen, and phosphorus content and storage in an alpine wetland in the Qinghai-Tibet Plateau, China

This study considers the spatial variability of soil organic carbon, nitrogen, and phosphorus storage in a drained alpine wetland and the possible relationships with soil properties. Top 0-0.30 m soil samples were collected in a typical alpine wetland in the south-eastern Qinghai-Tibet plateau using grid sampling. There was high spatial variability for soil organic carbon density (SOCD), soil total nitrogen density (STND), and soil total phosphorous density (STPD) in the drained alpine wetland. Spherical models best described the structure of the semivariograms for SOCD and STPD, and an exponential model for STND, with the range parameter of <4 m. Similar spatial distribution with lower or higher patches of C, N, and P storage were observed. SOCD, STND, and STPD were significantly negatively correlated with soil moisture (P<0.01), and significantly positively correlated with bulk density (P<0.01). However, no significant correlations were observed between SOCD, STND, and STPD and soil pH values. Wetland drainage might lead to higher C, N, and P densities in top 0.30 m soils due to peat compaction; thus, it is necessary to incorporate water table fluctuations or the whole depth of peat layers to estimating precisely C, N and P storage.