子午岭森林灰褐土受物理保护的有机碳数量上限(英文)

通过密度分组和超声波技术将每个土样分为3个组份:自由组份、闭合组份和重组,分别分析每个组份的有机碳质量分数.闭合组份和重组中的有机碳为受物理保护的有机碳.结果表明:在整个土壤剖面上各组份有机碳的数量表现为重组有机碳自由轻组闭合轻组,这就表明土壤中大部分有机碳是受物理保护的.各组份有机碳均表现为在0～40 cm深度迅速递减,40～80 cm深度相对稳定.随深度的增加,轻组中有机碳递减速率比重组和闭合组份中有机碳的递减显著.如0～10 cm深度轻组有机碳质量分数为6.672×10~(-6),但在60～80 cm深度轻组有机碳质量分数仅为0.260×10~(-6);0～10 cm深度重组有机碳质量分数为17.228×10~(-6),在60～80 cm深度重组有机碳质量分数为6.563×10~(-6).子午岭森林灰褐土保护有机碳的能力是有限的,通过曲线拟合得出在该地区每1000 g土壤中受物理保护的有机碳不会超过23.64 g.表层以下大部分土壤颗粒远未达到饱和,如果有更多的有机碳可利用,这部分土壤具有较大的碳汇潜能.

Detection of upper limit for physically protected OC in Ziwuling haplic greyxems soil

By a density fractionation approach and ultrasonic technique,each soil sample was divided into three fractions:free right fraction (free-LF),occluded fraction(occluded-LF)and heavy fraction (HF).The obtained fractions were analyzed for OC concentration.OC in the occluded and heavy fractions were taken together as protected OC.The results showed that,in the whole soil profile,dominance of OC consistently decreased in the following order:HF,free-LF,occluded-LF.This suggested that OC in soils were mostly protected.The OC content in free-LF,occluded-LF and HF all decreased rapidly in the 0～40 cm soil horizons and almost constant in 40～80 cm depths.In addition,the drop rate of OC content in LF with depths was more significant than that in occluded-LF and HF.OC content in LF was 6.672×10-6 in 0～10 cm depth and only 0.260×10-6 in 60～80 cm depth while OC content in HF was 17.228×10-6 in 0～10 cm depth and 6.563×10-6 in 60～80 cm depth.There was a clear upper limit for protected OC in Haplic Greyxems soil,which can be approached by curve fitting.1 kg total soil could at most protect 23.64 g OC in the region.In addition,most of the soil particles below the surface soil horizon were unsaturated,which gave the studied soil a large potential for OC sink,if more OC became available.