基于NbS的北京市乔木林固碳能力分析

  目的  乔木林生物质碳汇是影响森林碳汇的重要组成部分，是一种自然的气候解决方案，在全球气候变化大背景下，森林的固碳潜力一直被广泛关注，本文以北京市为例，分析不同的林业活动对乔木碳储量的影响。  方法  采用北京市森林资源设计调查数据，利用IPCC材积源—生物量法估算北京市乔木林碳储量，分析了2009—2014年北京市在森林转化、造林以及森林经营3种自然方案下碳储量的变化情况。  结果  （1）2009—2014年北京市森林面积净增长8.35 × 104 hm2，碳储量净增量约1.45 × 109 kg，年均碳固持量为0.29 × 109 kg/a。（2）2014年北京市人工林总碳储量高于天然林，且碳密度高于天然林。当前北京市森林龄级结构偏低龄化，随着森林的自然生长，仍有较大的碳固持潜力。在各个优势树种（组）中，人工杨树林的固碳效率尤为突出，远远高于其他优势树种。（3）山地森林活动强度较小，森林经营区域占比较大，城市森林变化剧烈，受造林与森林转化等措施影响较大。2009—2014年北京市由于森林转化为其他土地造成了1.06 × 109 kg的碳损失，造林带来了2.10 × 109 kg的碳固持，森林经营过程中有1.62 × 109 kg的碳固持与1.21 × 109 kg的碳损失，森林经营活动的总碳储量净增量0.41 × 109 kg，避免森林转化可以带来1.17 × 109 kg的碳汇。  结论  增加乔木林的固碳能力是应对气候变化的重要手段，避免森林转化可以凭借较小的森林面积贡献较大的碳汇，是一种低成本且效果显著的增汇方案。 

Carbon sequestration capacity of Beijing arbor forest based on NbS

  Objective  Carbon sequestration of arbor forest biomass is an important component affecting forest carbon sink, and is a natural based climate solution. In the context of global climate change, the carbon sequestration potential of forests has been widely concerned. This paper takes Beijing as an example to analyze the influence of different forestry activities on forest carbon storage.  Method  Based on the survey data of forest resource design in Beijing, the carbon storage of tree layer forest in Beijing was estimated by IPCC volume-biomass method. The change of carbon storage under three natural schemes of deforestation, afforestation and forest management in Beijing from 2009 to 2014 was analyzed.  Result  (1) From 2009 to 2014 in Beijing, the net increase of forest area in Beijing was 8.35 × 104 ha, the net increase of carbon storage was about 1.45 × 109 kg, and the average annual carbon sequestration was 0.29 × 109 kg/year. (2) In 2014, the total carbon storage of artificial forest in Beijing was higher than that of natural forest, and the carbon density was higher than that of natural forest. The forest age structure in Beijing was getting older and with the natural growth of forest, there was still a great potential for carbon sequestration. Among the dominant tree species (groups), the carbon sequestration efficiency of artificial poplar forest was particularly prominent, which was much higher than that of other dominant tree species. (3) The intensity of mountain forest activity was small, the forest management area accounted for a large proportion, the urban forest changed violently, and was greatly affected by afforestation and deforestation. From 2009 to 2014 in Beijing, deforestation into other lands caused a carbon loss of 1.06 × 109 kg; afforestation caused a carbon sequestration of 2.10 × 109 kg; there was a carbon sequestration of 1.62 × 109 kg and a carbon loss of 1.21 × 109 kg in forest management; the net increment of total carbon storage was 0.41 × 109 kg. Avoiding deforestation can bring 1.17 × 109 kg carbon sink.  Conclusion  Increasing forest carbon sequestration capacity is an important means to cope with climate change. Avoiding deforestation can contribute a large carbon sink with a small forest area, which is a low-cost and effective solution to increase forest carbon sink.