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林业科学 ›› 2020, Vol. 56 ›› Issue (3): 117-126.doi: 10.11707/j.1001-7488.20200313

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成熟森林固碳研究进展

朱万泽   

  1. 中国科学院水利部成都山地灾害与环境研究所 成都 610041
  • 收稿日期:2018-06-13 出版日期:2020-03-01 发布日期:2020-04-08
  • 基金资助:
    国家重点研发计划(2017YFC0505104-2);四川省环境治理与生态保护重大科技专项(2018SZDZX0031);中科院成都山地所"一三五"方向性项目(SDS-135-1707)

Advances in the Carbon Sequestration of Mature Forests

Wanze Zhu   

  1. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences Chengdu 610041
  • Received:2018-06-13 Online:2020-03-01 Published:2020-04-08

摘要:

成熟森林在在维持生物多样性和长期碳平衡中发挥着重要作用,近十多年来,全球掀起了成熟森林固碳研究热潮。理解成熟森林碳储存和碳源/汇动态,有助于评估和预测成熟森林在区域碳循环中的作用,对于估计森林碳减排范围、发展近自然林管理策略亦十分重要。本研究在介绍成熟森林林龄阈值的基础上,分析成熟森林碳储量与碳分配以及自然成熟森林生产力及其影响因素,综述成熟森林固碳的3个假说:1)碳中性假说随着森林演替林龄增加,森林生产力达到最大值后开始下降,到成熟森林阶段,森林碳吸收与生态系统呼吸达到平衡,因而处于碳中性状态;2)碳汇假说许多热带、亚热带以及北半球的北方和温带成熟森林可持续固碳几百年,成熟森林为全球碳汇,成熟森林固碳主要集中在土壤中,可能与气候变化引起森林生产力增加、植被碳流向土壤碳的比率随森林成熟度增加而增加以及气温上升和大气氮沉降等降低土壤异养呼吸有关;3)碳源假说少数研究报道认为成熟森林为净碳源,与成熟森林地被物、枯死木及土壤有机碳的周转加快有关。越来越多研究证实成熟森林能持续固碳,支持成熟森林碳汇假说。建议今后:1)加强成熟森林碳通量观测研究;2)从生态系统呼吸及其构成角度探讨成熟森林碳源/汇过程及其形成机制研究;3)加强全球变化对成熟森林固碳的影响研究。

关键词: 成熟森林, 碳储量, 碳源/汇, 森林生产力, 生态系统呼吸

Abstract:

Mature forest is often referred to as the old-growth forest or the late-successional forest, which plays an important role in maintaining biodiversity and long-term carbon balance. In recent ten years, the carbon sequestration in mature forests under different environmental regimes and global change scenarios has received increasing attention since the founding that the old-growth forests can accumulate carbon in soils. Understanding the carbon storage and carbon source/sink dynamics of mature forests can be helpful for evaluating and predicting the role of mature forests in regional carbon cycles. It is also essential to evaluate the full range of forest C mitigation and to develop the close-to-nature forest management practices. On the basis of introducing the thresholds of mature forest ages, this paper analyzes the dynamics of carbon storage and distribution in natural mature forest, and the mature forest productivity and their influencing factors. Three carbon source/sink hypotheses of mature forest are summarized:1) The carbon neutral hypothesis proposes that net ecosystem productivity in forests steadily increases to a maximum with the age of forests, followed by gradual decline. The total ecosystem photosynthetic assimilation is increasingly offset by higher autotrophic and heterotrophic respiration at the mature forest stage, eventually, old forests are believed to reach (that is, C neutrality). 2) The carbon sequestration hypothesis suggests that many old-growth forest ecosystems in tropical, subtropical, and northern and temperate regions can continue to accumulate carbon, and act as a net sink for atmospheric carbon dioxide for centuries. The carbon sequestration in the mature forests is mainly in the soil, which is probably related to the increasing productivity of mature forests caused by climate change, and the increasing conversion of vegetation carbon into soil carbon with the increase of forest maturity, as well as the decreasing heterotrophic respiration in mature forest soil due to the global warming and atmospheric nitrogen deposition. 3) But very few studies have shown that the old-growth forests serve as a het carbon source. Accelerated carbon cycling of litters, dead trees, and soil organic carbon pools, especially when coupled with limited growth potential, could potentially drive the mature forest ecosystems to become a net source of carbon under future regional climate change scenarios. A growing number of studies have confirmed that the mature forests can sequester carbon, supporting the mature forest sink hypothesis. The future research should be focused on:1) Ttrengthening the carbon fluxes observation of mature forests by using eddy covariance approach. 2) Exploring the process of carbon source/sink and its formation mechanism in mature forest based on ecosystems respiration and its composition. 3) Studying the effects of global change on carbon sequestration in mature forests.

Key words: mature forest, carbon storage, carbon source/sink, forest productivity, ecosystem respiration

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