Abstract: In this study, plants and soil samples were collected from 8 dominant shrub communities including Nitraria tangutorum, Anabasis elatior, Haloxylon persicum, Calligonum mongolicum, Caragana stenophylla, Ephedra przewalskii, A. brevifolia and Potentilla fruticose that extensively distribute in Xinjiang. By determining the contents of plant biomass carbon (PBC) and soil organic carbon (SOC), this study aimed at assessing the variation of PBC and SOC contents among the different shrub communities. The results showed that: (1) The values of PBC density from different shrub communities exhibited the following pattern: P. fruticose > C. stenophylla > E. przewalskii > H. persicum > C. mongolicum > N. tangutorum > A. brevifolia > A. elatior. Except for P. fruticose, the other shrub communities’ underground PBC densities were higher than those above ground. (2) The SOC density was strongly related to the PBC density. Except for E. przewalskii, A. brevifolia and P. fruticose species, the other shrub communities’ maximum SOC densities occurred in 0-10 cm soil layer, and decreased with the increase of soil depth. (3) The storage values of PBC and SOC in the eight shrub communities ranged from (0.41±0.05) × 10⁴ to (33.46±0.60) × 10⁴ Mg and from (0.22±0.01) to (6.88±0.03) Tg, respectively. (4) The SOC content was significantly positively correlated to altitude (P < 0.05), very significantly positively correlated to soil water content, and soil organic matter (SOM) and total nitrogen (TN) contents (P<0.01), while significantly negatively correlated to soil bulk density. The aboveground PBC content was significantly positively correlated to altitude and soil water content, and very significantly positively correlated to SOM, TN, SOC and underground PBC contents, while a very significant positive correlation was observed between underground PBC content and SOM and TN contents.

Key words: loss of net primary productivity, relative contribution index, act net primary productivity, human activity, quantitative assessment.