Characteristics of soil carbon,nitrogen and their components under different vegetation types in the karst reservoir area:A case study of Huaxi reservoir in Guiyang
The study area is located in the water conservation area of Huaxi reservoir in Guiyang City,Guizhou Province.Soil in this area is developed from limestone with the soil thickness varying greatly from 0 cm to 103.5 cm.Rocks are exposed in some parts of the area.Because the study area has been closed off to prevent deterioration,the vegetation is well protected.The main vegetation types are grassland,shrubs and bamboo forest.In order to understand the relationship between soil nitrogen and phosphorus contents and their components in the karst reservoir area,we analyzed the decomposition characteristics of soil organic matter in the karst area.The result can provide theoretical support for ecological restoration and conservation of water supply in the karst area.In Huaxi reservoir,we chose three typical vegetation types—grassland,shrubbery and bamboo forest—as the research objects.We selected 3-5 duplicates from every different vegetation plot,and studied the soil carbon and nitrogen contents and active components of these three vegetation types in two layers(Layer A and Layer B).The results showed that there were significant effects for different vegetation on carbon and nitrogen and their components(except for AN).With the change of vegetation types(grassland→shrubbery→bamboo forest),the content of organic carbon and its active components gradually increased(Layer A＞Layer B).TOC contents in bamboo forest(36.16 g·kg-1 and 29.68 g·kg-1)were higher than those in grassland(20.48 g·kg-1 and 18.24 g·kg-1).MBC contents in grassland was 54 percent and 49 percent of that in bamboo forest.The proportion of WSOC in total organic carbon was the smallest(0.04％-0.11％),among which the content of WSOC in bamboo forest accounted for a relatively high proportion(0.11％).The proportion of microbial biomass nitrogen was the second,which accounted for a relatively higher proportion in shrubbery(0.99％in layer A and 1.42％in layer B),but the lowest in bamboo forest(0.88％in Layer A and 0.89％in Layer B).The proportion of microbial biomass nitrogen was the least,accounting for only 0.02％-0.20％of total nitrogen.With the restoration(grassland→shrubbery→bamboo forest),MBN contents increased gradually,and the content of NO3--N in Layer A gradually reduced.The contents of microbial biomass nitrogen in bamboo forest(3.48 mg·kg-1 and 3.12 mg·kg-1)were significantly higher than those in shrubbery and grassland.The content of NO3--N in grassland was higher than that in bamboo forest(2.24 mg·kg-1).The content of NH4+-N was much higher than that of NO3-N.The content of nitrate nitrogen was more than 10 times that of NH4+-N.With the layer deepening,the contents of MBN and AN reduced,but the TN content increased.Among the ratios of different nitrogen components to total nitrogen,the ratio of AN to TN was the highest(3.38％-6.93％).The ratio of NH4+-N to TN was higher than that of NO3--N to TN,and the ratio of microbial nitrogen was the lowest,accounting for only 0.03％in shrubbery and grassland.In Layer A,the ratio of C to N was from 8.49 to 21.52,showing as grassland＜shrubbery＜bamboo forest,and layer A＞layer B.In layer B,the ratio was between 8.49 to 11.06,showing as shrubbery＜grassland＜bamboo forest.The results indicate that the vegetation types can affect the contents of carbon and nitrogen and their components.The vegetation of bamboo forest and shrubbery is conducive to the decomposition and absorption of soil carbon and nitrogen and can reduce the loss of soil and water.Therefore,the vegetation of bamboo forest and shrubbery can maintain water quality in the reservoir.Grassland is not suitable for ecological restoration in the karst area.However,this study only analyzes carbon and nitrogen and their components in different vegetation types,but does not explore changes of soil phosphorus content,microorganism content and plant root exudate,which needs further research.
Huaxi reservoirwater conservation areassoil carbon and nitrogenactive componentmicrobial biomass nitrogen
国家科技期刊平台
NSTL
万方数据
