揭示不同幅度上气候因子对土壤有机碳(Soil organic carbon,SOC)影响的主控性变化,是预测未来气候变化对SOC演变趋势影响的基础。本文利用中国西南地区363个森林土壤剖面数据,基于大区、省和地级市3个幅度,研究了气候因子对森林SOC密度的影响随幅度变化的规律及不同幅度下的主控气候因子。结果表明,年均降水量与SOC密度的相关性均随着幅度的减小而减弱,而年均气温与SOC密度的相关性随幅度变化的规律不明显,有较强的区域差异。大区幅度上,SOC密度主要受年均降水量和年均气温的综合作用。省级幅度上,西藏自治区东部主控因子为年均降水量,而四川和云南两省为年均气温。地级市幅度上,各市的主控因子基本与其所属的省一致。气候因子对SOC密度变异的解释能力在大区幅度上约20%,且随着幅度的减小解释能力也逐渐减小。
Knowledge about impacts of climatic factors on soil organic carbon (SOC) density at different scales is critical to predicting potential effect of future climate change on SOC dynamics. Based on the data of 363 forest soil profiles in Southwest China, variation of the effects of climatic factors on forest SOC density with the scale (region, province and prefecture-level city) was studied and dominant climatic factors at different scales were identified as well. Results show that the relativity of mean annual precipitation (MAP) with SOC density is decreasing with reducing scale. However, the relativity between mean annual temperature (MAT) and SOC density varies between regions, but not regularly. At the regional scale, SOC density is mainly under the joint effect of MAP and MAT. At the provincial scale, the dominant climatic factor is MAP in East Tibet, and MAT in Sichuan and Yunnan Provinces. At the city scale, similar results are found. Climatic factors can explain about 20% of the variability of SOC density at the regional scale, however, the explainability decreases with the reduction in scale.