岷江上游退化森林的保护、修复与展望

Protection,Restoration,and Prospects of Degraded Forests in the Upper Reaches of the Minjiang River in China

岷江上游的亚高山森林是成都平原的重要水源地和生态屏障,在长江经济带和国家生态安全屏障构建中具有重要作用。亚高山天然林主要以冷杉(Abies spp.)和云杉(Picea spp.)占优势的老龄林。20世纪50—80年代期间,该地区的原始针叶林经历了大规模采伐,现有森林植被为残留的原始针叶林斑块和天然次生针阔混交林、次生阔叶林、人工针叶林、人工天然混交林类型。针对岷江上游退化森林植被恢复和水源涵养功能提升的关键问题,历经近30年的系统性研究和生态恢复的经营实践,该区域取得的主要研究成果包括:1)采用多尺度观测和跨尺度分布式数值模拟技术,构建了植被生态和水文过程的耦合方法,揭示了岷江上游森林植被水文调节功能的多尺度形成与演变机制;2)运用氢同位素技术阐明了岷江上游不同植被类型之间水分的空间分配、迁移、转化与利用的循环机制;3)发现了岷江冷杉(A.fargesii var.faxoniana)原始林具有最高的水源涵养功能;4)创建了定量辨识退化森林恢复状态和演替阶段的方法与基于水碳效益权衡的水源涵养林空间规划决策支持系统;5)提出了自然演替与人工促进措施相结合的森林植被恢复与水源涵养功能提升的关键技术体系,以及岷江上游水碳效益权衡的森林植被空间格局优化配置方案。基于以上5方面的研究进展,我们提出了岷江流域森林植物保护修复的4个优先重点领域,包括山水林田湖草流域系统治理、生物多样性保护、森林植被质量与水源涵养功能提升和亚高山森林植被对气候变化的响应与适应。未来岷江上游退化森林植被生态保护和修复研究,需要从经典的森林植被恢复转变为统筹推进山水林田湖草系统治理,面向生态系统服务的水源涵养和固碳增汇功能协同提升,以及基于自然的流域生态保护修复空间战略及实现途径。

Subalpine forests in the upper reaches of the Minjiang River are very important for water resource conservation and eco-services in the Chengdu Basin and play important roles in the economic belt and ecological shelters of the Yangtze River.Subalpine natural forests are typically old-growth forests dominated by firs(Abies spp.)and spruces(Picea spp.).During the periods from the 1950s to 1980s,these subalpine forests were heavily logged with a large-scale clear-cut.Now,the existing forests in subalpine region have become a mixed pattern with some remnant old-growth forests as well as a mixture of natural secondary mixed broadleaf-conifer forests,secondary broad-leaved forests,and artificial and naturally regenerated mixed forest.In view of the forest vegetation restoration and enhancement of water conservation in the upper reaches of the Minjiang River,there have been carrying out systematic research and ecological restoration practice over nearly 30 years,the main research achievements for the ecological restoration include the following findings.1)Using multiscale observations and a distributed eco-hydrological model were put forward as new methods to develop a coupling approach of ecological processes and hydrological processes,by which to reveal the mechanisms underlying water resource conservation and s forest vegetation pattern change in the upper reaches of the Minjiang River.2)By using stable isotope(deuterium)technology,Temporal-spatial distribution patterns in the movement,allocation,transformation,and use of water cycling processes through different vegetation types in the upper reaches of the Minjiang River.3)Old-growth A.fargesii var.faxoniana forest showed the highest water conservation capacity among the five main vegetation types in the upper reaches of the Minjiang River.4)Quantitative methods to evaluate restoration status and successional stages for degraded forests and a decision-making management system based on water-carbon tradeoffs for water resource conservation of subalpine forests were successfully developed.5)Key technique package systems for enhancing forest vegetation recovery and water conservation function by combining natural restoration succession with human-aid natural regeneration,and the optimal configuration scheme of forest vegetation spatial patterns for managing the watershed water-carbon tradeoffs in the upper reaches of the Minjiang River were elaborated.Based on the above five principal findings,we put forward four future research priorities,including the systematic watershed rehabilitation of mountain-water-forest-farmland-lake-grassland,biodiversity conservation,improvements of forest quality and water conservation function,and responses and adaptation of subalpine forests to climate change.We suggest that the research on protection and restoration of degraded forests in the upper reaches of the Minjiang River should shift n from the traditional vegetation recovery at stand and ecosystem scales to the systematic integrity of the comprehensive management of mountain-water-forest-farmland-lake-grassland continuum at landscape and regional scales,the synergistic enhancement of water resource conservation and carbon sequestration aiming for ecosystem services,and nature-based spatial strategic planning and realization route of watershed conservation and restoration.