Abstract:

There are some sandy hills distributed along Poyang Lake, which belong to typical southern desertification. As located in subtropical climate zone, the sandy hills differed in vegetation and soil from northern deserts. Since carbon (C), nitrogen (N) and phosphorous (P) stoichiometry are critical indicators of biogeochemical coupling in terrestrial ecosystems, the nutrients stoichiometry has been successfully used in indicating community succession, vegetation restoration and degenerative process in recent years. The C〖DK〗∶N and C〖DK〗∶P of plant leaf can indicate the ability of assimilating the carbon when the plant uptakes the N and P elements, as well as the nutrient use efficiency of plant. The C〖DK〗∶N and C〖DK〗∶P of soil can reflect organic matter decomposition and soil nutrient supply. In addition, the homoeostasis of C, N and P stoichiometry is the important mechanism maintaining ecosystem structure, function and stability. However, carbon, nitrogen and phosphorous stoichiometry of the sandy hills along Poyang Lake were still poorly understood. In this study, leaves of 17 dominant species and soil were sampled along desertification intensity gradient in Duobao sandy hill, Poyang Lake. Subsequently, leaf and soil organic carbon, total nitrogen and total phosphorous were measured. The objective of this study was to clarify C〖DK〗∶N and C〖DK〗∶P stoichiometry of leaf and soil in response to desertification intensity and provide a scientific basis for vegetation restoration. Results indicated that ratio of leaf carbon to nitrogen ranged from 185 to 1273, with mean of 431. The ratio of carbon to phosphorous varied from 1698 to 5071, averaged at 3418. The ratio of leaf carbon to nitrogen in high desertification intensity is 280, the ratio of carbon to phosphorous is 3074. The ratio of leaf carbon to nitrogen in moderate desertification intensity is 595, and the ratio of carbon to phosphorous is 3701. However, the ratio of leaf carbon to nitrogen in low desertification intensity is 390, while the ratio of carbon to phosphorous is 3376. The soil C〖DK〗∶N value ranged from 98 to 463 for 0-10 cm depth, 24 to 465 for 10-30 cm depth and 37 to 450 for 30-50 cm depth, respectively. The soil C〖DK〗∶P value varied from 198 to 759, 30 to 905 and 47 to 765 for the corresponding layers, respectively. Moreover, leaf C〖DK〗∶N and C〖DK〗∶P stoichiometry showed the same pattern in response to desertification intensity, with the minimum occurred in the high desertification area. Soil C〖DK〗∶N and C〖DK〗∶P stoichiometry showed different pattern along the desertification gradient. The ratio of C〖DK〗∶N decreased with desertification intensity, but C〖DK〗∶P value showed the opposite trend in contrast to C〖DK〗∶N. Additionally, according to our correlation analysis results, the variation of leaf C〖DK〗∶N and C〖DK〗∶P was controlled by leaf nitrogen and phosphorous concentration. The soil C〖DK〗∶N variation depended on soil total nitrogen. By comparison, soil C〖DK〗∶P variation was controlled by soil organic carbon.