Fragility of karst ecosystem and environment: Long-term evidence from lake sediments
Fragility of karst ecosystem and environment: Long-term evidence from lake sediments
复制标题
喀斯特生态系统和环境的脆弱性：来自湖泊沉积物的长期证据
DOI：
10.1016/j.agee.2020.106862
复制
发表时间：
2020-06-01
影响因子：
6.6
通讯作者：
Wang, Jingfu
中科院分区：
文献类型：
--
作者：
Chen, Jingan;Yu, Jia;Wang, Jingfu
中国西南地区是世界上最大的连续喀斯特地区，生态退化严重。岩溶生态系统与环境的脆弱性问题已引起了许多学者的关注。然而，这些研究主要集中在特定的岩溶地质背景和短期（年度）的生态环境变化。在较长的时间尺度上，关于KEE如何应对气候变化和人类活动等外部干扰的知识非常有限。通过对中国西南岩溶区湖泊沉积物地球化学分析，探讨了十年-百年尺度上的KEE演化特征。白仙湖有机C/N、Sr/Rb比值和孢粉组合表明，3.6 ~ 2.2 ka B. P.的干旱事件使白仙湖生态环境发生了明显的恶化，植被退化，草本植物减少，蕨类植物增加，陆地生产力下降。而且，喀斯特生态系统经过很长一段时间也没有恢复到早期的水平。一旦发生退化，喀斯特生态系统在短期内难以恢复。喀斯特土壤的水土保持能力差、抗旱能力弱是喀斯特生态系统脆弱性的内在机制。红枫湖近三十年来富营养化迅速加剧。由于岩溶区碳酸盐岩流域的溶解无机碳（DIC）供应量比非岩溶区丰富，水库对农业氮磷添加的响应更敏感。初级生产力的提高、有机质沉积通量的增加、低层缺氧和磷释放的增加之间可能存在正反馈循环。这种正反馈，连同DIC施肥效应和农业N和P添加的敏感性，可以解释水生KEE的脆弱性。本文首次提出了KRSC陆地和水生生态系统脆弱性的长期证据，并为KEE对气候变化和农业活动的敏感性和恢复力提供了新的见解，突出了喀斯特地区生态环境保护的极端重要性。
Southwest China is the largest continuous karst area in the world, which has suffered from serious ecological degradation. Many researchers have discussed the fragility of karst ecosystem and environment (KEE). However, these studies focused mainly on the particular karst geologic setting and short-term (annual) eco-environmental changes. At longer timescales, knowledge of how KEE responds to external disturbances such as climate changes and human activities is very limited. Based on geochemical analysis of lake sediments in the karst region of Southwest China (KRSC), this paper probes into the evolutionary characteristics of KEE at decadal-centurial timescales. Organic C/N ratios, Sr/Rb ratios and pollen assemblage in Baixian Lake indicate that striking ecoenvironmental deterioration occurred as a result of the drought event between 3.6 ka B.P. and 2.2 ka B.P. The regional vegetation degraded with dwindling herbs, increasing ferns and decreasing terrestrial productivity. Furthermore, the karst ecosystem had not restored to the earlier level even after a long time. Once degradation happens, the karst ecosystem would be unlikely to recover in the short term. Poor water-soil conservation capacity and weak drought resistance of karst soil should be the inherent mechanism of the fragility of terrestrial KEE. Hongfeng Lake has suffered from rapid eutrophication in the last three decades. Reservoirs respond more sensitively to agricultural N and P addition because of abundant dissolved inorganic carbon (DIC) supply from the carbonate catchment in karst region than in non-karst region. A positive feedback loop may develop among elevated primary productivity, higher deposition fluxes of organic matter, anoxia in hypolimnion and enhanced internal P release in aquatic ecosystem. This positive feedback, together with the DIC fertilization effect and sensitivity to agricultural N and P addition, may explain the fragility of aquatic KEE. This paper for the first time presents a long-term evidence for the fragility of both terrestrial and aquatic ecosystem in the KRSC, and provides new insights into the sensitivity and resilience of KEE to climate change and agricultural activities, highlighting the extreme importance of eco-environment protection in karst region.