帽儿山次生林区土壤有机碳储量及地形因子的影响

Soil Organic Carbon Storage and Effects of Topographical Factors of the Secondary Forest Region of Mao,er Mountains

在帽儿山次生林区,按坡位、坡向差异对等设置20块样地,采集1 m剖面深度范围内不同发生层土样,研究了地形因子（坡位、坡向、坡度）对土壤有机碳含量、有机碳密度的影响,并通过逐步回归分析量化各因子对土壤有机碳密度变异影响的相对重要性。结果表明,本区土壤剖面有机碳密度为8.89~31.31 kg/m^2,具有较大的空间变异性。土壤有机碳的表聚特征十分明显,平均而言,A层集中了全剖面总有机碳的53.2%。坡位和坡向显著影响土壤有机碳的分布：平均而言,下坡A层有机碳密度是上坡的1.95倍,其1 m剖面有机碳密度是上坡的1.67倍;阴坡A层有机碳密度是阳坡的1.38倍,其1 m剖面有机碳密度是阳坡的1.23倍。不过,在所调查的范围内坡度对上、下坡土壤有机碳含量和密度均无显著影响。逐步回归显示,坡位是土壤有机碳数量分异的主控因子,可独立解释A层有机碳密度空间变异的61.25%和1 m剖面有机碳空间变异的64.0%。研究结果可为区域森林土壤碳储量准确估算和碳汇林立地选择提供参考。

In the secondary forest region of Mao, er Mountains, a total of 20 sampling plots were established symmetrically in accordance with the position and aspect of slope, and soil samples representing different genetic horizons were collected within a profile depth of 1 m. The effects of topographical factors （ the position, aspect, and gradient of slope ） on soil organic carbon （ SOC ） content and density were investigated. Stepwise regression analysis was employed to quantify the relative influence of each factor. The SOC density within lm profile ranged from 8. 89 to 31.31 kg/m^2 , of which 53.2% was concentrated in the A horizon on average. SOC dis- tribution was significantly influenced by slope position and aspect. Downslope sites hold 95% more SOC in the A horizon and 67% more SOC in the lm profile than upslope sites, while ubac sites hold 38% more SOC in the A horizon and 23% more SOC in the lm profile than adret sites, respectively. No significant relation was found between the amount of SOC and the gradient of slope, when the down-or upslope sites were examined alone. Stepwise regression analysis suggested that slope position was the dominating factor, which alone could explain 61.2% of the spatial variability of SOC density for the A horizon and 64. 0% for the lm profile. The results of this study have implications for accurate estimation of SOC stock in hilly areas, and for site selection of carbon sink forests.