黄土高原地区退耕还林后土壤有机碳储量变化特征及影响因素

Variation characteristics and influencing factors of soil organic carbon storage after returning farmland to forest on the Loess Plateau

土壤有机碳(SOC)固存效应与影响因素识别是当前研究的焦点和前沿议题。然而,在退耕还林后,SOC的固存效应以及各影响因素之间的协同变化规律尚不明确。对于基于气候、植被、土壤等多重因素综合作用的定量归因,仍需加强研究。搜集了1999到2022年黄土高原地区有关退耕还林后植被恢复对SOC储量影响的117篇文献,共获得了1140组SOC数据。通过对不同条件下(气候因素、植被因素、土壤因素)植被恢复对SOC储量的影响程度的分析,揭示植被恢复类型对SOC储量的影响。同时,采用地理探测器模型探讨不同植被恢复类型SOC储量增加效应的主要驱动因素及其交互作用。研究结果表明,植被恢复显著提高了该地区的SOC储量。林地的固碳效应优于灌木地和草地,分别显著提高了36.21%,32.41%和15.57%。植被恢复对SOC储量的增加效应随着植被恢复年限和植被覆盖率的增加而增强,特别是在低土壤容重(<1 g/cm^(-3))条件下,植被恢复对SOC储量的增加效应更为显著,但随着土壤深度增加植被恢复对SOC储量的增加效应减弱。在年平均气温(MAT)为7—10℃、年平均降雨量(MAP)为450—550 mm条件下,林地恢复有助于促进SOC储量的增加效应。在MAT<7℃、MAP为450—550 mm条件下,灌木地的SOC储量增加效应更明显,但受植被覆盖率的限制。在MAT<7℃、MAP>550 mm条件下,草地的SOC储量增加效应更为显著。地理探测器模型分析表明,植被恢复年限、植被覆盖率和MAP分别是影响林地、灌木地和草地SOC固存的主要驱动因素。因素间交互作用通常比单一因素对SOC储量的影响更为显著。具体而言,MAP与植被恢复年限的交互作用对林地SOC储量的增加效应最高,达到了33.46%;MAT与土壤容重的交互作用对灌木地SOC储量的增加效应最高,达到了86.77%;MAP与植被覆盖率的交互作用对草地SOC储量的增加效应最高,达到了60.59%。研究结果可为不同恢复条件下选择合理的植被配置方式提供参考。

The carbon sequestration effect of soil organic carbon(SOC)and identification of the influencing factors are the core and frontier issues of current research.However,the retention of SOC after returning farmland to forests and the synergistic effect of various influencing factors are still unclear.The quantitative attribution based on climate,vegetation,soil,and other factors still needs to be strengthened.By collecting117 papers about the influence of vegetation restoration on SOC storage after returning farmland to forests on the Loess Plateau from 1999 to 2022,1140 pairs of valid data were obtained,and the influence of vegetation restoration on SOC storage under different conditions(climate factors,vegetation factors,and soil factors)were analyzed.At the same time,the main driving factors affecting SOC storage of different vegetation restoration types and their interaction were identified and quantified through the modeling of geographic detector.The results showed that vegetation restoration could significantly increase SOC storage on the Loess Plateau,and the effect of forest land restoration on soil carbon sequestration was better than that of shrub land and grassland,which were significantly increased by36.21%,32.41%,and 15.57%,respectively.The effect of vegetation restoration on the SOC storage increased with the increases of vegetation restoration age and vegetation coverage,but decreased with the increase of soil depth.When soil bulk density was low(<1g/cm^(-3)),it was more likely to promote the increase of SOC storage.In addition,when mean annual temperature(MAT)was 7—10℃and mean annual precipitation(MAP)was 450—550 mm,the restoration of forest land was more conducive to increasing SOC storage.When MAT was<7℃and MAP was 450—550 mm,the effect of shrub land on SOC storage was more significant,but it was limited by vegetation coverage.When MAT was<7℃and MAP was>550 mm,the effect of grassland restoration on SOC storage increased significantly.The geographic detector model showed that vegetation restoration age,vegetation coverage,and MAP were main driving factors for SOC storage in forest land,shrub land,and grassland,respectively.In the aspect of increasing SOC storage,the interaction between various factors was better than that of single factor.Specifically,the interaction between MAP and vegetation restoration age made the most significant contribution to SOC storage of forest land,which was 33.46%.In shrub land,the interaction between MAT and soil bulk density contributed the most to SOC storage(86.77%).The interaction between MAP and vegetation coverage contributed the most to SOC storage of grassland(60.59%).It provides a reference for selecting reasonable vegetation allocation under different restoration conditions.