Zhu Xiai, Shen Youxin, Yuan Xia, Yuan Chuang, Jin Liya, Zhao Zhimeng, Chen Fajun, Yang Bin, Jiang Xiaojin, Liu Wenjie
CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, 666303, Yunnan, China.
College of Ecology and Environmental Science, Yunnan University, Kunming, 650500, China.
Environ Sci Pollut Res Int. 2024 May;31(23):34234-34248. doi: 10.1007/s11356-024-33552-y. Epub 2024 May 3.
Soil organic carbon (SOC) is a crucial medium of the global carbon cycle and is profoundly affected by multiple factors, such as climate and management practices. However, interactions between different SOC fractions and land-use change have remained largely unexplored in karst ecosystems with widespread rock outcrops. Owing to the inherent heterogeneity and divergent response of SOC to land-use change, soil samples with close depth were collected from four typical land-use types (cropland, grassland, shrubland, and forestland) in the karst rocky desertification area of China. The aim of this study was to explore the responses of SOC dynamics to land-use types and underlying mechanism. The results showed that land-use type significantly affected SOC contents and its fractions. Compared with cropland, the other three land uses increased the total organic carbon (TOC), microbial biomass carbon (MBC), and non-labile organic carbon (NLOC) contents by 6.11-129.44%, 32.58-173.73%, and 90.98-347.00%, respectively; this demonstrated that a decrease in both labile and recalcitrant carbon resulted in SOC depletion under agricultural land use. Readily oxidized organic carbon (ROC) ranged from 42 to 69%, accounting for almost half of the TOC in the 0-40-cm soil layer. Cropland soil showed significantly higher ROC:TOC ratios than other land-use types. These results indicated that long-term vegetation restoration decreased SOC activity and improved SOC stability. Greater levels of soil exchangeable calcium (ECa) and clay contents were likely responsible for higher stabilization and then accumulation of SOC after vegetation restoration. The carbon pool index (CPI) rather than the carbon pool management index (CPMI) exhibited consistent variation trend with soil TOC contents among land-use types. Thus, further study is needed to validate the CPMI in evaluating land use effects on soil quality in karst ecosystems. Our findings suggest that land-use patterns characterized by grass or forest could be an effective approach for SOC-sequestration potential and ensure the sustainable use of soil resources in the karst area.
土壤有机碳（SOC）是全球碳循环的关键介质，受到气候和管理措施等多种因素的深刻影响。然而，在广泛分布着岩石露头的喀斯特生态系统中，不同土壤有机碳组分与土地利用变化之间的相互作用在很大程度上仍未得到探索。由于土壤有机碳对土地利用变化具有内在的异质性和不同响应，在中国喀斯特石漠化地区从四种典型土地利用类型（农田、草地、灌丛和林地）采集了深度相近的土壤样本。本研究的目的是探讨土壤有机碳动态对土地利用类型的响应及其潜在机制。结果表明，土地利用类型显著影响土壤有机碳含量及其组分。与农田相比，其他三种土地利用方式分别使总有机碳（TOC）、微生物量碳（MBC）和非活性有机碳（NLOC）含量增加了6.11% - 129.44%、32.58% - 173.73%和90.98% - 347.00%；这表明在农业土地利用下，活性碳和难分解碳的减少导致了土壤有机碳的消耗。易氧化有机碳（ROC）在42%至69%之间，占0 - 40厘米土层总有机碳的近一半。农田土壤的ROC:TOC比值显著高于其他土地利用类型。这些结果表明，长期植被恢复降低了土壤有机碳活性，提高了土壤有机碳稳定性。较高水平的土壤交换性钙（ECa）和粘粒含量可能是植被恢复后土壤有机碳更高稳定性进而积累的原因。碳库指数（CPI）而非碳库管理指数（CPMI）在不同土地利用类型间与土壤总有机碳含量呈现出一致的变化趋势。因此，需要进一步研究来验证碳库管理指数在评估喀斯特生态系统土地利用对土壤质量影响方面的有效性。我们的研究结果表明，以草地或森林为特征的土地利用模式可能是提高土壤有机碳固存潜力并确保喀斯特地区土壤资源可持续利用的有效途径。
