Abstract:

Forests are important natural resources and have important ecological and economic values, which play an important role in regulating the global carbon cycle, mitigating climate warming and promoting sustainable social and economic development. In the context of carbon trading, thinning management of plantations could greatly affect carbon sequestration and the corresponding economic value. To study the effects of thinning on carbon dynamics and the economic value of carbon sequestration and accurately understand the response of forest ecosystem carbon dynamics to thinning, we conducted field observations and simulations of ecosystem carbon dynamic components after 30% (density) thinning in subtropical Pinus massoniana plantations from December 2014 to December 2016 and evaluated the economic value of ecosystem carbon fixation under three carbon price scenarios (1200 yuan, 150 US dollars and 34.38 yuan). The results showed that the carbon sink function of the forest ecosystem decreased significantly after thinning and even changed from a carbon sink to a weak carbon source in the first year after thinning. The increase in the carbon emissions of understory vegetation and stump respiration were the main reasons for this result. Subsequently, the forest ecosystem carbon sink function recovered rapidly and recovered to 70.0% in the second year after thinning. The decrease in the carbon emissions of the tree layer and the increase in the carbon emissions of the understory vegetation and stump respiration played an important role in this process. The effects of thinning on forest environmental factors, soil nutrients and plant competition significantly changed the carbon dynamic components of the subtropical Pinus massoniana plantation and together affected the carbon dynamics and carbon fixation capacity of the ecosystem. The changes in understory vegetation carbon emissions and stump respiration carbon emissions played an important role in this change. The carbon price significantly affected the economic value of ecosystem carbon fixation after thinning, which decreased by 7647.27 yuan∙hm^-2, 5869.28 yuan∙hm^-2, and 219.09 yuan∙hm^-2 and 1623.75 yuan∙hm^-2, 1246.23 yuan∙hm^-2, and 46.53 yuan∙hm^-2, respectively. The loss of economic value of carbon fixation caused by the reduction in the carbon sink function can be compensated for by calculating the economic benefit of wood obtained from thinning. The research results play an important role in refining the measurement methods of ecosystem carbon dynamics and comprehensively evaluating the economic value of ecosystem carbon fixation and put forward higher requirements for improving the carbon trading market.

Key words: thinning, carbon dynamics, carbon fixation, economic value, Pinus massoniana, subtropical

摘要：

森林兼具资源与环境双重属性,在调控全球碳循环、减缓气候变暖、促进社会经济可持续发展方面起着重要作用。碳交易背景下,对人工林实施间伐管理将对生态系统碳动态及碳固定经济价值产生显著的影响。为研究间伐对人工林碳动态及碳固定经济价值的影响,准确掌握人工林森林生态系统碳动态组分对间伐的响应,以亚热带马尾松（Pinus massoniana Lamb.）人工林为研究对象,于2014年12月—2016年12月开展间伐30%（密度）后生态系统碳动态组分野外观测与模拟以及在3种碳价格（1200元、150美元和34.38元）情境下碳固定经济价值评估。结果表明：间伐后森林生态系统碳汇功能显著降低,间伐后第一年甚至由碳汇转变为微弱的碳源,林下植被碳排放及伐桩呼吸碳排放升高是导致这一结果的主要原因;随后其碳汇功能迅速恢复,间伐后第二年恢复至70.0%,乔木层碳排放降低和林下植被碳排放及伐桩呼吸碳排放升高在这一过程中发挥了重要作用。间伐对森林环境因素、土壤养分、植物竞争关系等的影响,显著改变了亚热带人工马尾松林生态系统碳动态组分,并共同影响了生态系统碳动态和碳固定能力。碳价格显著影响生态系统碳固定经济价值,在上述3种碳价格情境下第一年和第二年间伐后生态系统碳固定经济价值分别减少7647.27、5869.28、219.09 yuan∙hm^-2和1623.75、1246.23、46.53 yuan∙hm^-2,计算间伐获得木材经济收益则可弥补因碳汇功能降低导致的碳固定经济价值损失。研究结果对于细化研究生态系统碳动态实测方法和综合评估生态系统碳固定经济价值具有重要作用,也对完善碳交易市场提出了更高的要求。

关键词: 间伐, 碳动态, 碳固定, 经济价值, 马尾松, 亚热带