摘要:西南喀斯特地区是我国主要的生态脆弱区之一，石漠化严重，旱涝灾害频发。植被恢复是提升脆弱生态系统土壤碳氮固持的有效方式，但该区不同植被恢复方式土壤碳氮动态监测的研究还很缺乏。本研究以典型喀斯特峰丛洼地为对象，选取人工林、牧草地、人工林+牧草地、撂荒地自然恢复4种最主要的植被恢复方式为研究对象，以耕地作为对照，对比分析退耕前（2004年）、退耕10年（2014年）和13年后（2017年）土壤碳氮储量动态变化特征。其中2004-2014年研究区未发生极端内涝灾害，2014-2017年连续发生2次极端内涝灾害事件。研究结果表明，退耕10年后，4种恢复方式下土壤有机碳（SOC）储量均显著增加，但退耕13年后，除撂荒地SOC持续增加外，其他3种恢复方式下SOC表现出下降趋势。植被恢复后土壤全氮（TN）储量提升相对缓慢，退耕10年仅牧草地显著增加，退耕13年后人工林+牧草和撂荒地TN增加，且撂荒地在退耕后呈持续增加趋势。相关性分析结果表明，土壤交换性Ca2+与SOC、TN均呈显著正相关关系，且与2014年相比，2017年不同植物恢复方式下土壤交换性Ca2+均显著下降，这可能与研究区2015年和2016年连续内涝灾害有关。以上结果说明，不同恢复方式均能显著提升喀斯特地区土壤碳氮固持，并以自然恢复最佳，其生态系统能有效抵御极端气候灾害带来的负面影响。
关键词:喀斯特生态系统/
植被恢复方式/
植被恢复年限/
土壤有机碳/
土壤全氮/
内涝灾害
Abstract:The karst region in Southwest China is one of the most ecologically fragile areas characterized with severe rocky desertification, and increased and frequent flood events. Vegetation restoration has been recognized as an effective strategy for soil carbon and nitrogen accumulation in degraded ecosystems. However, soil carbon and nitrogen dynamics following vegetation restoration have not been evaluated with a long-term, fixed-point research approach in the karst areas. Thus, we compared the effects of vegetation restoration types on soil carbon and nitrogen stocks before (in 2004) and after 10 (in 2014) and 13 years (in 2017) of cropland abandonment. Four restoration strategies were implemented in the present study, namely, restoration with plantation forest, grassland, a combination of plantation forest and grassland, and spontaneous regeneration to a natural grassland. Cropland under maize-soybean rotation (CR) was used as the control. From 2004 to 2014, there were no extreme water-logging disasters, whereas from 2014 to 2017, two extreme water-logging disasters occurred in the study region. The results revealed that soil organic carbon (SOC) stocks in all the four restored vegetation types significantly increased after 10 years of cropland abandonment, whereas after 13 years, the plantation forest, grassland, and the combination of plantation forest and grassland, except the natural grassland, showed a decreasing trend. The increase in the total nitrogen (TN) content of soil in response to vegetation restoration was less than that of SOC; the TN content significantly increased only in the grassland after 10 years of cropland abandonment. The TN content in the combination of plantation forest and grassland and natural grassland increased after 13 years of cropland abandonment, and that in the natural grassland continuously increased after cropland abandonment. The correlation analysis showed that soil exchangeable Ca2+ was positively correlated with SOC and TN (P < 0.05). However, the content of soil exchangeable Ca2+ significantly decreased in 2017 than in 2014. The reduction in soil exchangeable Ca2+ can be attributed to the continuous flood event in the study area in 2015 and 2016. Vegetation restoration can significantly improve soil carbon and nitrogen sequestration in karst areas. Furthermore, when compared with other vegetation restoration types, natural vegetation restoration was more beneficial to soil carbon and nitrogen sequestration, which can resist the negative effects of extreme climate disasters effectively.
Key words:Karst ecosystem/
Vegetation restoration measure/
Vegetation restoration years/
Soil organic carbon/
Soil total nitrogen/
Water-logging disaster
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