GEOGRAPHY

Researchers assess the potential of forest restoration for carbon sequestration in the southwest karst region


Spatiotemporal divergence of aboveground vegetation carbon sequestration levels in Southwest China in the past 20 years. Photo courtesy of interviewee

The team of researcher Wang Kelin, Huanjiang Karst Ecosystem Observation and Research Station, Institute of Subtropical Agroecology, Chinese Academy of Sciences, has made important progress in assessing the carbon sequestration potential of vegetation restoration in the karst region of southwest China in the past 20 years, and the relevant research results have recently been published in Earth’s Future.

Ecosystem carbon sinks are the greenest and most economical way to achieve carbon neutrality, with forests contributing the most. In the past 20 years, under large-scale artificial afforestation and natural restoration, southwest China has become a hot spot for “greening” of global vegetation cover. However, the saturation of forest growth and limited afforestable land limit the long-term nature of forest carbon sink, and the fragile geological background of karst also restricts the sustainability of large-scale concentrated afforestation, resulting in greater uncertainty in the quantitative assessment of ecological carbon sequestration effect in the karst region of southwest China.

Under the guidance of Wang Kelin and Yue Yuemin, researchers of the Institute of Subtropical Ecology, Xuemei Zhang, a doctoral student at the University of Chinese Academy of Sciences, and the team of Martin Brandt, an associate professor at the University of Copenhagen in Denmark, considered the high heterogeneity of vegetation landscapes in southwest China, and used the remote sensing data of aboveground biomass carbon density obtained by the team from 2002 to 2017 to achieve the maximum aboveground biomass carbon carrying capacity of mature forests by grading and defining regional vegetation. A multi-factor random forest model considering the heterogeneous landscape characteristics of southwest China was constructed, which predicted the maximum aboveground biomass carbon carrying capacity in the region from 2002 to 2017, and quantified the aboveground biomass carbon storage and its future carbon sequestration potential under large-scale afforestation in southwest China in the past 20 years.

The results show that under the current ecological restoration conditions, the maximum aboveground biomass carbon carrying capacity of forests in eight provinces and regions of southwest China is 20.54 PgC, and the aboveground biomass carbon of forests increased by 2.34 PgC from 2002 to 2017 under the background of large-scale afforestation, and there is still a carbon sequestration potential of 5.32 PgC in the future. Using the probability data of forest land from 2002 to 2017, the researchers identified old forests, new forests and potential afforestation areas that have not yet fully reached the carbon sequestration potential, and found that the potential afforestation areas in the eight southwestern provinces and regions can still sequester carbon by 2.39 PgC, while the old forest and new forest areas have carbon sequestration potential of 0.86 PgC and 0.99 PgC respectively in the future, especially the old forests have reached 88.8% of their maximum carrying capacity, which is a stable carbon pool.

In addition, the nonlinear and linear fitting results of the carbon sequestration potential of global forest aboveground biomass show that the maximum aboveground biomass carbon carrying capacity of the current vegetation in southwest China is about 2030-2060, and afforestation and sustainable management of forest land in eight provinces and regions in southwest China provide an important window period to achieve the goal of carbon neutrality, which is an important ecological carbon sink potential area in China.

The study further found that the carbon sequestration of forests in eight provinces and regions in southwest China was mainly affected by the intensity of human activities and topographic characteristics, and there were significant regional differentiation characteristics of the carbon sequestration potential of vegetation aboveground biomass, and then clarified the carbon sequestration potential areas of old forests (mainly distributed in areas with high altitude, large undulations and steep slopes), new forest carbon sequestration potential areas (mainly distributed in slopes and slope foothills with high intensity of human activities) and future afforestation carbon sequestration potential areas (mainly distributed in areas where the current vegetation degradation is still serious). It provides an important reference for the optimal layout of ecological construction space in the southwest karst region in the future.

According to reports, this study does not consider the impact of specific forest types, forest ages and forest management measures on the carbon sequestration capacity of forest land, and there is also certain uncertainty in the definition of old forests, new forests and potential afforestation areas in the future, and it is urgent to carry out accurate quantitative research on the carbon sink function of ecological restoration based on high-resolution satellite remote sensing and deep learning in the future.

The research was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, and the Youth Interdisciplinary Team of the Chinese Academy of Sciences. (Source: Wang Haohao, China Science News)

Related paper information:https://doi.org/10.1029/2022EF002674



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