| Reclaimed land from lake is a typical change of land utilization in the region of Poyang Lake even all the middle and lower reaches of yangtze river. In the background of a large population with relatively little land and scramble for land from lake, there is as much as 1301km2 wetlands in poyang lake region has been reclaimed. To research the stoichiometry of typical natural wetland soil and reclaimed wetland soil in Poyang Lake has very important theoretical significance to know how the plant utilizes its nutrient and carbon(C), nitrogen(N) and phosphorous(P). Besides,it can provide scientific guidance to assess how much impact the land utilization change makes to the wetland ecosystems. We take seven kinds of soil under different plant community along water level to measure the organic carbon(C), total nitrogen(N)and total phosphorus(P) from Poyang Lake natural wetland which is Gan river delta front nanji wetland national nature reserve in 2013. We have sampled six reclaimed farmland soils of different years in Poyang, Yugan and Xingzi county which is the typical area of Poyang lake wetland reclamation to measure its carbon(C), nitrogen(N)and phosphorus(P). In addition, to clarify the wetland carbon composition characteristic and to provide scientific data to subtropical lake wetland soil carbon responses to the climate change. In the study of chemometrics, we have also compared the different components of soil organic carbon(light group of organic carbon, restructuring of organic carbon, soluble organic carbon, microbial biomass carbon) before and after reclaimed in the Poyang Lake wetland. Main results are as follows:(1) As the change of water level gradient and community types, the natural wetland soil C:N:P stoichiometric ratio changes significantly, the soil C:N, C:P changes mainly depends on the organic carbon content, N:P changes mainly depends on the nitrogen content.(2)The C:N of Poyang lake natural wetland soil is low, this is good for the wetland to accumulate organic carbon. Under different water level gradient, the C:N in the soil and the changes of soil organic carbon is incomplete synchronization shows that natural wetland soil carbon is not only affected by C:N ratio, also together with the wetland water level and other factors such as soil bulk density.(3)The different years of reclaimed soils the C:N ratio has no significant difference, it is relatively stable. The C:N ratio in the soil not only depends on the organic carbon content, but also depends on the nitrogen content. Surface soil C:P ratio has significant differences, the C:P ratio mainly depends on organic carbon, the N:P ratio of the soil between 0-10 cm and 10-30 cm has significant differences, the N:P ratio mainly depends on nitrogen.(4)The light group of organic carbon(1.88mg·g-1) in the reclaimed farmland soil on the surface is more than the natural wetland(1.08mg·g-1), it is probably owing to straw returned and organic fertilizer input afterreclaimed. In addition, another import reason maybe is the natural wetland alternation of wetting and drying year after year which loses light group of organic carbon of the surface and underground runoff.(5)The microbial biomass carbon in the reclamation soil is significantly higher than the natural wetland’s. In the process of reclaimed, the measures such as succession of crops and straw returned would make the soil microbial activity, all this makes the soil microbial biomass carbon content higher than the unused wetlands.(6) In the 0-30 cm soil of farmland reclamation,the organic carbon, light group of organic carbon in the surface, microbial biomass carbon are higher than natural wetland, it means that “reclaim land from lake” which is the important characteristics of regional land use has effectively increased the soil carbon storage library. Moreover, the C, N, P content and its stoichiometric ratio in the wetland has changed dramatically after the land is enclosed. |
PDF Full Text Request