Carbon, Nitrogen And Phosphorus Stoichiometry Of Plant And Soil In The Sandy Hills Of Poyang Lake

There are some sandy hills distributed along Poyang Lake, which belong totypical southern desertification. The desertified land area is about38,900hectares,mainly in Pengze, Hukou, Duchang, Xingzi, Xinjian and so on. As located insubtropical climate zone, the sandy hills differed in vegetation and soil from northerndeserts. During the past ten to twenty years, Pinus elliottii was introduced in sandyhills for vegetation restoration. Leaves of17dominant species and soil were alsosampled along desertification intensity gradient in Duobao sandy hill, Poyang Lake.Since carbon (C), nitrogen (N) and phosphorous (P) stoichiometry are criticalindicators of biogeochemical coupling in terrestrial ecosystems, the nutrientsstoichiometry has been successfully used in indicating community succession andvegetation restoration in recent years. However, our knowledge of the temporalvariability of carbon, nitrogen and phosphorous stoichiometry is much less developedthan its spatial pattern. Besides, it remains unknown whether there is consistenttemporal pattern for various ecosystem components, such as plants and soil. In thisstudy, organic carbon, total nitrogen and total phosphorous in leaves of17dominantspecies, soil and Pinus elliottii plantation were measured along desertificationgradient in a typical sandy hill close to Poyang Lake. The objective of this study wasto clarify C、N、P stoichiometry of leaf and soil in response to desertificationintensity，and the effects of desertification intensity and stand age on leaf and soilcarbon, nitrogen and phosphorous stoichiometry, as well as the role of nutrientsstoichiometry in indicating vegetation restoration in sandy hills. Results showed that:(1) Soil organic carbon, total nitrogen and total phosphorous were ranged from0.26%to1.54%,0.014%to0.078%and0.010%to0.031%respectively. They all showed thesame dynamic patterns: increasing with desertification intensity lowered.(2) Leavesof17dominant species carbon, nitrogen and phosphorous are ranged from347.9to428.9mg·g-1,3.1to22.7mg·g-1and0.7to2.1mg·g-1, respectively.(3) Soil C:N valueranged from9.8to46.3for0～10cm depth,2.4to46.5for10～30cm depth and3.7to45.0for30～50cm depth, respectively. Soil C: P value varied from19.8to75.9,3.0to90.5and4.7to76.5for the corresponding layers, respectively. Soil N:P valuevaried from0.4to3.7,0.4to2.9and0.7to3.4for the three layers.(4) Moreover, leafC:N and C:P stoichiometry showed the same pattern in response to desertification intensity, with the minimum occurred in the high desertification area. The minimumof leaf N: P occurred in the medium desertification area. Soil C:N, C:P and N:Pstoichiometry showed different pattern along the desertification gradient. The ratio ofC:N increased with desertification intensity, but C:P and N:P value showed theopposite trend in contrast to C:N. Soil C:N and N:P variations depended on soil totalnitrogen. By comparison, soil C:P variation was controlled by soil organic carbon.(5)Leaf N:P ratios were20.63and15.61for10-year and less than10-year Pinus elliottii,respectively, which suggested growth of Pinus elliottii was firstly limited by bothnitrogen and phosphorous, however, Pinus elliottii plantation would change tophosphorous limitation during stand development.(6)Leaf C:N and C:P ratio of Pinuselliottii is higher than other plants significantly, showing the advantages of carbonfixation and nutrient use efficiency. The introduction of Pinus elliottii is important tothe rapid increase of vegetation coverage at sandy hill, Poyang Lake. Leaf nitrogenand ratio of C:N were most sensitive to changes in desertification intensity and standage which is an indication of diagnosis and assessment the Pinus elliottii growthconditions in the sandy hills of Poyang Lake.