莽山不同次生林土壤有机碳分布与土壤物理性质的相关性

Correlation between distribution of soil organic carbon and soil physical properties for different secondary forests in Mangshan

【目的】探讨湖南莽山国家级自然保护区三类次生林土壤有机碳(SOC)分布特征与土壤物理性质的关系,为该地区森林土壤碳储量的准确计量及森林土壤固碳增汇提供参考依据。【方法】在海拔1230~1300 m区域内的杉木、粤松林和竹林内设9个固定标准地,采集不同层次土壤样品32个,测定其SOC、土壤容重及田间持水量,运用方差分析、相关分析及回归分析法研究不同植被类型SOC分布特征及其与土壤容重和田间持水量间的关系。【结果】杉、松、竹三类林地不同土层SOC含量存在显著差异(P<0.05,下同),随土壤深度增加呈递减趋势;不同林分变化幅度差异不同,且各土层间的差异达显著水平。三类林地0~40 cm土层SOC存贮有机碳在整个土层所占比重不同,分别为77.7%、77.1%和85.9%。经回归分析发现,杉、松、竹三类林地SOC和土壤容重拟合值R分别为0.632、0.727和0.615,杉木林SOC含量与土壤容重呈极显著相关(P<0.01,下同);三类林地SOC含量与田间持水率均呈极显著或显著正相关。方差分析结果表明,黏粒、粉粒、砂粒含量在同一土层中的三类林地间存在极显著差异;黏粒、粉粒、砂粒含量与SOC含量相关不显著(P>0.05),而砂粒与黏粒、粉粒存在极显著负相关。杉、松、竹三类林地砂粒含量在土壤垂直剖面各层均高于黏粒、粉粒含量。【结论】莽山不同次生林SOC与土壤物理性质密切相关,土壤容重、田间持水量、土壤机械组成等物理性质可作为营林和增加森林土壤碳汇的参考指标。

[Objective]The relationship between soil organic carbon（SOC） distribution and physical properties of three types of secondary forests in Mangshan National Forest Park, Hunan, in order to provide reference for soil carbon storage calculation and soil carbon sequestration in the forests. [Method]Thirty-two soil samples in nine treatment plots had been collected which were set up in three types of secondary forests including Chinese fir, Piuus kwangtungensis and bamboo at altitude of 1230-1300 m. SOC, bulk density and field capacity of the samples were measured. Variance analysis, correla- tion analysis and regression analysis were conducted to study distribution characteristics and its relation with bulk density and field capacity. [Resuh]SOC content in different layers of the three forests were significantly different（P〈0.05, the same below）. With the increase of soil depth,SOC generally decreased, but the variation range of SOC was different among these three types of secondal7 forests. There was a significant difference in variation between different soil layers. The proportions of SOC in 0-40 cm layer of Chinese fir（77.7%）, P. kwangtungensis（77.1%） and bamboo（85.9%） forests were different.According to regression analysis, SOC-bulk density fitted value R for Chinese fir, P. kwangtungensis and bamboo forests were 0.632, 0.727 and 0.615 respectively. For Chinese fir forest, there was extremely significant correlation between SOC and bulk density（P〈O.O1, the same below）. There was extremely significant difference or significant difference between SOC and field capacity in three types of forests. Variance analysis showed that there was extremely significant difference in clay, silt and sand contents at the same layer between different types of forests. Clay, silt and sand contents were not significantly correlated with SOC content（P〉0.05）, but there was extremely significant correlation between sand and clay, silt. At all vertical layers, sand content was higher than those of clay and silt in three types of forests. [Conclusion]SOC of different types of secondary forests in Mangshan is closely related with soil physical properties. Bulk density, field capacity, soil mechanical composition can serve as indexes for forest management and increasing forest soil carbon sequestration.