九寨沟世界自然遗产核心景区钙华景观的研究进展与展望

九寨沟钙华是距今约3万年(特别是1万年)以来逐渐形成的。大规模的钙华沉积是湖泊、滩流、瀑布、泉及台地景观形成的基础,覆盖核心景区2.4 km²的面积。钙华景观是九寨沟遗产地突出普遍价值——"自然美学价值"的核心,是景区的关键吸引力。为九寨沟的持续保护和为未来研究提供支持,本文从钙华沉积物、钙华景观成因、钙华景观变化及其原因、钙华景观保护恢复的角度,总结了公开和未公开发表的研究结果。针对目前钙华景观保护面临的主要问题(钙华退化、藻类生物量增加、沼泽化),本文归纳了相关的自然与人为因素,包括气候变暖、大气沉降、水化学变化、旅游活动、森林采伐、地质灾害等;归纳了地震和滑坡等地质灾害对钙华景观形成与重塑的双重作用;总结了钙华景观保护恢复的管理工作及其成效。本文提出未来可重点研究:(1)气候变化和人为活动背景下多圈层(大气、陆地生态系统、水生生态系统和基岩系统)对水体氮、磷、溶解性有机物、绿藻生物量、钙华沉积与溶蚀的影响机制及程度;(2)2017年九寨沟7.0级地震后,自然与人为干预下钙华微地貌的长期稳定性,水土流失加剧对湖泊透明度、钙华、沼泽化及美学价值的长期影响,地质灾害及其防治对钙华景观的长期效应。

Tufa Landscapes in the Key Scenic Areas of the Jiuzhaigou Natural World Heritage Site:A Critical Review and Future Research Needs

Tufa deposition has continued in Jiuzhaigou since about 30,000 years ago and mostly since 10,000 years ago, forming bases for diverse landscapes, such as lakes, shoals, waterfalls, springs, and terraces, and covering a total area of 2.4 km² in the key scenic area. These landscapes constitute the key of Jiuzhaigou heritage''s outstanding universal value, namely, natural aesthetic value, and are incomparable tourist attractions. To better protect Jiuzhaigou and to support future research, we reviewed previous studies from the perspectives of tufa sediment, tufa landscape formation mechanisms, tufa landscape changes and relevant causes, and tufa landscape protection and restoration. The major challenges for tufa landscape conservation (including tufa degradation, increased green algae, and lake swamping) were described. The natural and anthropogenic causes of these challenges are climate warming, atmospheric deposition, hydrochemical changes, tourist activities, previous commercial logging, geological disasters, and others. We also introduced the dual effects of geological disasters (such as earthquakes and landslides) on the formation and evolution of tufa landscapes. Furthermore, tufa landscape management and its effectiveness were summarized. In the end, we suggested the major future research needs:(1) the mechanisms and extents that earth''s multispheres (including terrestrial ecosystem, atmospheric environment, aquatic ecosystem, and lithosphere) and tourist activities influencing the tufa dissolution and deposition, nitrogen, phosphorous, dissolved organic matter, and green algae in water environment; and (2) effects of the 2017 Ms 7.0 Jiuzhaigou Earthquake, including long-term impacts from enhanced soil erosion on lake transparency, swamping, tufa, and aesthetic value, long-term stability of tufa landscapes restored artificially and naturally, and long-term effects of geological disasters and their controls on tufa landscapes.