中国喀斯特生态系统健康诊断的方法、进展与展望

Methods,progress and prospect for diagnosis of karst ecosystem health in China——An overview

中国是碳酸盐岩型喀斯特面积最大、分布最广的国家,在喀斯特地区居住着约2亿的人口,经济规模约占全国的10%.尤其是以贵州为中心的西南地区,位于长江和珠江的上游,经济欠发达,但却是国家的重要生态安全屏障.喀斯特地貌重要而特殊,科学诊断其生态系统的健康不仅对生态修复和实现可持续发展至关重要,更是制定应对方案的基本前提.尽管以往开展了大量的研究工作,但是依然缺乏系统性和整体性认识.本文结合前人研究,进一步将喀斯特地貌演化发育总结为6个阶段:成岩阶段、成陆阶段、成山阶段、成丛阶段、成林阶段和成原阶段.在此基础上,又从碳酸盐岩风化成土速率的计算、土壤水的诊断、水土流失的评价、石漠化解译与演变、生态系统服务的科学计量5个方面进行系统的总结和梳理.尽管不同时代、不同学者的不同研究方法,其结果有着非常大的差异.但是,综合考虑已有的研究结果及其使用方法的优点和不足,归纳发现:(1)碳酸盐岩化学风化很快(30~130 mm ka^(−1)),但由于其酸不溶物含量低(5%以内),导致其成土速率极其缓慢,一般在5~50 t km^(−2)a^(−1)之间.(2)土壤少且分布不连续,但是土壤含水量却比较高,在0.2~0.4 m^(3)m^(−3)之间,这可能与周边基岩的汇水效应相关,且未来呈干化趋势.(3)土壤侵蚀模数低,一般在2~200 t km^(−2)a^(−1)之间,但由于坡陡、降雨量大且与岩土突变接触,导致其侵蚀风险极大,并存在一定比例的地下漏失现象.(4)石漠化的演变可分为单变式、渐进式和返变式3种经典类型,但是通过决策树和人机交互的石漠化解译方法相对高效和精准.(5)喀斯特生态系统服务功能的评价模型要基于成土速率来进行修正水土保持功能和基于岩溶地质碳汇修正气候调节功能.当前诊断喀斯特生态系统健康的指标、方法和模型亟须改进和创新,要充分体现喀斯特地区的特殊性和模型方法的匹配性,提高监测数据的时空分辨率,特别是亟须建立喀斯特社会-生态系统耦合模型,准确刻画出喀斯特生态系统对气候变化和人类活动的响应过程,提升诊断模型的准确度和可预测性.总之,本文系统总结了诊断中国喀斯特生态系统健康与可持续性的方法和取得的重大进展,并进一步从“岩-土-水-石-生”的角度提出了未来的研究方向和突破重点,以期为维护喀斯特地区的生态安全和可持续发展提供科技支撑.

China is the country with the largest area and widest distribution of carbonate karst,with a population of approximately 200 million and an economic scale of approximately 10%of the country.In particular,the southwest region centered in Guizhou,located at the upper reaches of the Yangtze and Pearl Rivers,is an economically underdeveloped but critical ecological security barrier for the country.Karst landforms are important topological features.Scientific diagnosis of the health of its ecosystem is not only essential for ecological restoration and sustainable development but is also the basic premise for formulating response plans.Although a significant amount of research has been carried out in the past,a lack of systematic and holistic understanding still exists.Based on previous studies,in this paper,we further summarize the evolution and development of karst landforms into six stages:diagenetic,continental,mountain-forming,cluster,forestforming,and primitive stages.On this basis,we also systematically summarize and detail five aspects:The calculation of weathering and soil-forming rate of carbonate rocks,diagnosis of soil water,evaluation of soil and water loss,interpretation and evolution of rocky desertification,and scientific measurement of ecosystem services.Despite the different research methods of different scholars in different times,the results are very different.However,after comprehensive consideration of the existing research results and the advantages and disadvantages of their application methods,the following conclusions were made.(1)Although the chemical weathering of carbonate rocks is very fast(30–130 mm ka^(−1)),their soil formation rate is extremely slow due to their low content of acid-insoluble substances(within 5%),generally between 5 and 50 t km^(−2)a^(−1).(2)The soil is small and the distribution discontinuous,but the soil water content is relatively high,ranging from 0.2 to 0.4 m^(3)m^(−3).This may be related to the catchment effect of surrounding bedrock,and it will be dry in the future.(3)The modulus of soil erosion is low,generally between 2 and 200 t km^(−2)a^(−1).However,due to steep slope,heavy rainfall,and abrupt contact with rock and soil,the risk of soil erosion is very high,and there is a certain proportion of underground leakage.(4)The evolution of rocky desertification can be divided into three classic types,namely univariant,progressive,and retro-variant,but the method of rocky desertification resolution through decision tree and human-computer interaction is relatively efficient and accurate.(5)The evaluation model of karst ecosystem service function should be based on the soil formation rate to correct the water and soil conservation function and the climate adjustment function based on the karst geological carbon sink.At present,the indicators,methods,and models for diagnosing the health of the karst ecosystem must be improved and innovated to fully reflect the particularity of the karst region and the matching of the model methods,to improve the spatial and temporal resolution of the monitoring data(especially to establish a coupling model of the karst social-ecosystem),to accurately depict the response process of the karst ecosystem to climate change and human activities,and to improve the accuracy and predictability of the diagnostic model.In short,in this paper,we systematically summarize and detail the methods and major progress in diagnosing the health and sustainability of China’s karst ecosystem and further propose the future research direction and breakthrough focus from the perspective of“rock soil water stone life”,with a view to providing scientific and technological support for maintaining the ecological security and sustainable development of karst areas.