The Soil Organic Carbon Characteristics Of Jatropha Curcas Plantation Ecosystem In Dry-hot Valley Region In Yunnan Province, China

The dynamics and characteristics of soil labile organic carbon(MBC,WSO,ROC),mineral nitrogen and the biomass of Jatropha curcas were studied in 3 different densities Jatropha curcas plantation and 3 different land use types(Jatropha curcas plantation, banana plantation and grassland)by the fixed plots combined with laboratory mtthods in dry-hot valley of Honghe river region,Yunnan Province,China. The results showed as follows.(1)The sequence of TOC and ROC conten were planting spacing 1.5m×2m>3m×3m>2m×3m; The sequence of WSOC content were planting spacing 1.5m×2m>2m×3m>3m×3m; The sequence of MBC content were planting spacing 3m×3m>1.5m×2m>2m×3m; The soil labile organic carbon content decreased with the increasing of soil depth in the same planting density. The correlationship analysis showed that, soil total nitrogen ,total organic carbon and soil temperature is the main ecological facrors. Three factrors have an effect on soil labile organic carobn content and accumulative contribution rates of these 3 factors accounted for 93.67%.(2)The variation of TOC,WSOC,MBC and ROC content in different soil depth were inconsistent at 3 different land use types. The sequence of TOC,WSOC and ROCcontent at 0～10cm soil depth were Jatropha curcas plantation >banana plantation>grassland. The sequence of TOC,WSOC and ROCcontent at 10～25cm and 25～40cm soil depth were banana plantation > Jatropha curcas plantation >grassland; The sequence of MBC content at 0～10cm,10～25cm and 25～40cm soil depth were banana plantation > grassland > Jatropha curcas plantation; the correlationship analysis showed that, soil organic carbon and total phosphorus were the main ecological factors and there has an effect on soil organic carbon content and the accumulative contribution rates of these 2 factors accounted for81.27%.(3)There was a same variation characteristic of the soil labile organic carbon content at 3 different planting spacing Jatropha curcas plantations and 3 different land use types in dry-hot valley. The mean content of WSOC and ROC in the dry season were higher than that in the rain season; the mean content of MBC in the rain season was higher than that in the dry season;(4)There was a obvious temporal and seasonal variation characteristic of soil mineral nitrogen(NO3--N and NH4+-N)content at 3 different planting spacing Jatropha curcas plantations and 3 ifferent land use types. NO3--N and NH4+-N content decreased with the soil depth increasing. Soil NO3--N content was the highest at the beginning of rain season and mean content in the dry season was higher than that in the rain season at the grassland. The NH4+-N content was the lowest in the end of dry season and the highest in the rain season and mean content in the rain season was higher than that in the dry season at the Jatropha curcas plantations and grassland. (5)The biomass Regression model Y=25.005(D2H)0.952 was set up and applied. The biomass and annual net primary productivity were 26.025t·hm-2 and 10.827t·hm-2·a-1 of Jatropha curcas ,respectively.(6)The sequence of carbon ratio in different organs of Jatropha curcas were fruit(56.74%)>stem(45.87%)>root(45.12%)>leaf(45.12%) and the whole tree carbon ratio was 47.27%. the soil organic carbon content and carbon density were 16.61g·kg-1 and 22.76t·hm-2,respectively.