Carbon Sink Enhancement Research Articles

Contribution of straw disposal to carbon source and sink under the framework of carbon neutrality

Exploring the spatio-temporal variation characteristics of carbon source and carbon sink under different disposal methods of crop straw is of great significance for optimizing the utilization policy of crop straw resources in China and realizing the goal of maximizing carbon emission reduction and carbon neutralization. Based on data from National Statistical Yearbook, we examined the changing trends of both the amount and value of carbon emission, carbon emission reduction, carbon sink enhancement under different crop straw disposal methods in 31 provinces of Chinese mainland. The results showed that the mean annual carbon emissions of straw burning in China from 2008 to 2019 were 8.74 million tons of CO2e. Since 2014, the mean annual reduction rate of carbon emissions was 17.3%. The mean annual carbon emission reduction of energy utilization was 39.82 million tons of CO2e, with solid briquette fuel produced by straw contributing the most with a contribution of about 98%. The amount of carbon sequestration of straw returning to field was increasing annually, with an average annual value of 271 million tons of CO2e. There was a carbon ecological surplus in straw disposal in China. The annual growth rate of net carbon emission reduction was 9.8%. The net carbon emission reduction intensity and its value were increasing, reaching 2.62 t·hm-2 and 76.19 yuan·hm-2 in 2019, respectively. A spatial pattern of 'high in the east and low in the west' was observed for the mean annual carbon emissions of straw, energy carbon emission reduction, carbon sink of straw returning to the field, and net carbon emission reduction in China, with main external characteristics of the regional differences and spatial aggregation.

Carbon stock estimation of mixed-age date palm (Phoenix dactylifera L.) farms in northeastern Ethiopia

The date palm (Phoenix dactylifera) is a fruit tree that grows from 392 to 1500 m above sea level. In addition to their socioeconomic, traditional, and religious value, it is a tree that tolerates high temperatures, drought, and salinity better than many other fruit crop plant species and plays an important role in the balancing and sequestration of atmospheric carbon. Date palm has been cultivated by agro pastoralists in Northeastern Ethiopia since ancient times, but no research has been done on the carbon stock of date palm farms (DPF) in the region. Therefore, the focus of the current study was to examine the carbon storage capacity in the biomass and soil of a DPF in the Aysaita and Afambo Districts of Northeastern Ethiopia. The ages of recorded date palm on the plot were classified into three age classes using information collected from the farm owners: 1st age class (for plantations less than 10 years), 2nd age class (for plantations between 10 and 20 years), and 3rd age class (for plantations older than 20 years). In the DPF, 45 main plots (20 m × 20 m) were established for tree species inventory. In the main plots, three 1 m × 1 m subplots were set up to collect soil samples. A total of 360 soil samples were collected; 180 for soil organic carbon fraction analysis and 180 for bulk density determination. The total carbon stock was calculated by adding the carbon stocks in biomass and soil (0–60 cm depth). Date palm trees accounted for 98.79% of total biomass carbon stocks in the date palm farm. The average aboveground biomass carbon stock of date palm trees older than 20 years was 1.55 and 1.36 times higher than the first and second age classes, respectively. Date palm trees between the ages of 5 and 20 years contributed 69.45% of total biomass carbon stocks (Mg C ha−1). Soil organic carbon made for 32.9% of total carbon stocks. Our research found that the date palm farm of this study would contribute to emission reduction and carbon sink enhancement, as well as improving local livelihoods in the study area.

Impacts of ecological restoration projects on the ecosystem carbon storage of inland river basin in arid area, China

As an important means to cope with global climate change, ecological restoration projects have a huge impact on ecosystem carbon storage functions. Scientifically evaluating the response process and mechanism of basin ecosystem carbon storage functions in ecological restoration projects is beneficial to the improvement of regional ecosystems. Taking Shiyang River Basin (SRB) as an example, and based on the perspective of “carbon sink–carbon source” mutual transformation, the current study utilized the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model to analyze the spatio-temporal dynamics of carbon storage in SRB, quantified the effect of ecological restoration projects on the ecosystem carbon fixation capacity, and identified sensitive and vulnerable areas of carbon loss against the background of climate and land use/cover change (LUCC). The results show that the ecosystem carbon storage in SRB changed significantly before and after the ecological project implementation, with a decrease of 5.71 Tg in 1986–2000 and an increase of 14.11 Tg in 2000–2016. The proportion of carbon sink enhancement areas was only 7.46% in 1986–2000, which increased to 15.04% in 2000–2016, indicating that the ecological restoration effect of the watershed was obvious as a result of the ecological management. The contribution of LUCC brought about by the ecological restoration project to the increase in ecosystem carbon storage was as high as 103.71%, for which the increase in woodland and grassland was the key. However, in 2000–2016, low carbon optimization areas accounted for 4.17% and carbon emission control areas for 6.16% of the total area of SRB. The carbon fixation capacity of these areas declined, and carbon emissions were elevated, especially in carbon emission control areas. These were mainly distributed in the oasis–desert transition zone in the mid-lower reaches, which are sensitive and vulnerable areas for carbon loss. Therefore, in future ecological restoration and protection processes, these areas should be given more attention and protection.

Fire decline in dry tropical ecosystems enhances decadal land carbon sink

The terrestrial carbon sink has significantly increased in the past decades, but the underlying mechanisms are still unclear. The current synthesis of process-based estimates of land and ocean sinks requires an additional sink of 0.6 PgC yr−1 in the last decade to explain the observed airborne fraction. A concurrent global fire decline was observed in association with tropical agriculture expansion and landscape fragmentation. Here we show that a decline of 0.2 ± 0.1 PgC yr−1 in fire emissions during 2008–2014 relative to 2001–2007 also induced an additional carbon sink enhancement of 0.4 ± 0.2 PgC yr−1 attributable to carbon cycle feedbacks, amounting to a combined sink increase comparable to the 0.6 PgC yr−1 budget imbalance. Our results suggest that the indirect effects of fire, in addition to the direct emissions, is an overlooked mechanism for explaining decadal-scale changes in the land carbon sink and highlight the importance of fire management in climate mitigation.

Effects of atmospheric aerosols on terrestrial carbon fluxes and CO2 concentrations in China

Abstract Atmospheric aerosols have contributed to the terrestrial carbon cycle through diffuse radiation fertilization effect and hydrometeorological feedbacks. Subsequently, perturbations in terrestrial carbon sink alter atmospheric carbon dioxide (CO2) concentrations and influence future climate change. Here, we use a regional climate model, RegCM4, coupled with the Yale Interactive terrestrial Biosphere model (YIBs) to assess the effects of the current aerosol loading on terrestrial carbon fluxes and atmospheric CO2 concentrations during 2006–2015 over China. We found that aerosols enhance gross primary production (GPP) by 0.36 Pg C yr−1 (5%), which primarily stems from Southwest and Southeast China. Meanwhile, the aerosol-induced diffuse fraction (DF) increase, surface cooling and vapor pressure deficit (VPD) decrease together lead to a − 0.06 Pg C yr−1 (21%) reduction in the net ecosystem exchange (NEE). Among them, aerosol-induced DF increment is found to be the dominant contributor, which covers ~ 59–62% of China's land area. The effects of aerosols on GPP and NEE are more evident in the growing season, with maximum effects occurring in July and August, respectively. Moreover, the terrestrial carbon sink enhancement due to aerosols further results in a significant decline in CO2 concentrations, with a large reduction (>2 ppm) found in southern and eastern parts of China during the summer. Our results highlight the importance of understanding the interactions among aerosol pollution, climate change, and the global carbon cycle.

Forest Carbon Sequestration, Pathogens and the Costs of the EU’s 2050 Climate Targets

Carbon sequestration is suggested as a low-cost option for climate change mitigation, the functioning of which can be threatened by pathogen infestation. This study calculates the effects of infectious pathogens on the cost of achieving the EU’s 2050 climate targets by combining the so-called production function method with the replacement cost method. Pathogens are then assumed to affect carbon sink enhancement through the impact on productivity of forest land, and carbon sequestration is valued as the replacement for costly reductions in emissions from fossil fuels for reaching the EU’s 2050 climate targets. To this end, we have constructed a numerical dynamic optimization model with a logistic forest growth function, a simple allometric representation of the spread of pathogens in forests, and reductions in emissions from fossil fuels. The results show that the annual value of forest carbon sequestration ranges between approximately 6.4 and 14.9 billion Euros, depending on the impact and dispersal of pathogens. Relatively large values are obtained for countries with large emissions from fossil fuels, e.g., Germany, France, Spain and Italy, which also face costs of pathogen together with countries with large forest area, such as Romania.

Decrease in winter respiration explains 25% of the annual northern forest carbon sink enhancement over the last 30 years

AbstractAim Winter snow has been suggested to regulate terrestrial carbon (C) cycling by modifying microclimate, but the impacts of change in snow cover on the annual C budget at a large scale are poorly understood. Our aim is to quantify the C balance under changing snow depth.Location Non‐permafrost region of the northern forest area.Methods Here, we used site‐based eddy covariance flux data to investigate the relationship between depth of snow cover and ecosystem respiration (Reco) during winter. We then used the Biome‐BGC model to estimate the effect of reductions in winter snow cover on the C balance of northern forests in the non‐permafrost region.Results According to site observations, winter net ecosystem C exchange (NEE) ranged from 0.028 to 1.53 gC·m−2·day−1, accounting for 44 ± 123% of the annual C budget. Model simulation showed that over the past 30 years, snow‐driven change in winter C fluxes reduced non‐growing season CO2 emissions, enhancing the annual C sink of northern forests. Over the entire study area, simulated winter Reco significantly decreased by 0.33 gC·m−2·day−1·year−1 in response to decreasing depth of snow cover, which accounts for approximately 25% of the simulated annual C sink trend from 1982 to 2009.Main conclusion Soil temperature is primarily controlled by snow cover rather than by air temperature as snow serves as an insulator to prevent chilling impacts. A shallow snow cover has less insulation potential, causing colder soil temperatures and potentially lower respiration rates. Both eddy covariance analysis and model‐simulated results show that both Reco and NEE are significantly and positively correlated with variation in soil temperature controlled by variation in snow depth. Overall, our results highlight that a decrease in winter snow cover restrains global warming as less C is emitted to the atmosphere.

Determination of Priorities in the Forest Carbon Sink Enhancement Policies in the Republic of Korea

탄소흡수원으로써의 산림부문의 중요성이 점차 증가함에 따라 다양한 정책들이 고려되고 있다. 제한된 예산과 자원 여건 하에서 정책의 효율성을 추구하기 위하여 본 연구에서는 최고최저조정법을 이용하여 산림청의 10대 산림 탄소흡수원 증진 정책들의 우선순위를 결정하였다. 산림 분야 전문가 설문조사 결과, 산림경영방식 및 시업체계 개선, 조림 및 식생복구 확대, 산림바이오매스 에너지 활용 및 이용시설 증대, 임목수집 시스템 및 재활용 체계 개선, REDD+ 사업 참여 확대 순으로 중요한 것으로 나타났다. 이 연구 결과는 향후 국내 산림탄소흡수원 확충을 위한 정부 핵심 정책을 수행함에 있어서 우선순위를 정하는데 중요한 정보를 제공할 것으로 기대한다.

Application of Remote Sensing to Monitor Ecosystem Carbon Source and Sink in China

Kyoto Protocol states that developed countries have the responsibility to reduce the amount of greenhouse gas emissions. It, also, suggests that developed countries take measures to enhance carbon sink. Therefore, every country pays more attention on the research of global carbon cycle. China, a developing country with a fast economic increasing rate, has urgent need of related data and information so as to adjust its national development plan and negotiate with other countries. Remote sensing is one of the most important technologies and data sources for large-scale carbon-related researches including terrestrial ecosystem carbon cycling law, carbon sink/source pattern and sink enhancement technology. This paper introduces recent applications of remote sensing technology to the following aspects in China: monitoring land cover, simulating carbon flux, spatial distribution of carbon sink and carbon sink enhancement measures.

The littoral zone in the Three Gorges Reservoir, China: challenges and opportunities

For flood control purpose, the water level of the Three Gorges Reservoir (TGR) varies significantly. The annual reservoir surface elevation amplitude is about 30 m behind the dam. Filling of the reservoir has created about 349 km(2) of newly flooded riparian zone. The average flooding period lasts for more than 6 months, from mid-October to late April. The dam and its associated reservoir provide flood control, power generation, and navigation, but there are also many environmental challenges. The littoral zone is the important part of the TGR, once its eco-health and stability are damaged,which will directly endanger the ecological safety of the whole reservoir area and even the Yangtze River Basin. So, understanding the great ecological opportunities which are hidden in littoral zone of TGR (LZTGR) and putting forward approaches to solve the environmental problems are very important. LZTGR involves a wide field of problems, such as the landslides, potential water pollution, soil erosion, biodiversity loss, land cover changes, and other issues. The Three Gorges dam (TGD) is a major trigger of environmental change in the Yangtze River. The landslides, water quality, soil erosion, loss of biodiversity, dam operation, and challenge for land use are closely interrelated across spatial and temporal scales. Therefore, the ecological and environmental impacts caused by TGD are necessarily complex and uncertain. LZTGR is not only a great environmental challenge but also an ecological opportunity for us. In fact, LZTGR is an important structural unit of TGR ecosystem and has special ecosystem services function. Vegetation growing in LZTGR is therefore a valuable resource due to accumulation of carbon and nutrients. Everyone thinks that the ecological approach to the problem is needed. If properly designed, dike-pond systems, littoral woods systems, and re-created waterfowl habitats will have the capacity to capture nutrients from uplands and obstruct soil erosion. Ecological engineering approaches can therefore reduce environmental impacts of LZTGR and optimize ecological services. In view of the current situation and existing ecological problems of LZTGR, according to function demands such as environmental purification, biodiversity conservation, and vegetation carbon sink enhancement, we should explore the eco-friendly utilization mode of resources in LZTGR. Ecological engineering approaches might minimize the impacts or optimize the ecological services. Natural regeneration and ecological restoration in LZTGR are valuable for soil erosion decrease, pollutant purification, biodiversity conservation, carbon sink increase, and ecosystem health maintenance in TGR.

Preliminary estimation of the organic carbon pool in China’s wetlands

Accurate estimation of wetland carbon pools is a prerequisite for wetland resource conservation and implementation of carbon sink enhancement plans. The inventory approach is a realistic method for estimating the organic carbon pool in China’s wetlands at the national scale. An updated data and inventory approach were used to estimate the amount of organic carbon stored in China’s wetlands. Primary results are as follows: (1) the organic carbon pool of China’s wetlands is between 5.39 and 7.25 Pg, accounting for 1.3%–3.5% of the global level; (2) the estimated values and percentages of the organic carbon contained in the soil, water and vegetation pools in China’s wetlands are 5.04–6.19 Pg and 85.4%–93.5%, 0.22–0.56 Pg and 4.1%–7.7%, 0.13–0.50 Pg and 2.4%–6.9%, respectively. The soil organic carbon pool of China’s wetlands is greater than our previous estimate of 3.67 Pg, but is lower than other previous estimates of 12.20 and 8–10 Pg. Based on the discussion and uncertainty analysis, some research areas worthy of future attention are presented.

A comparative assessment of different options to reduce CO 2 emissions

The IIASA research project on Environmentally Compatible Energy Strategies includes the assessment of options and measures for mitigating global CO 2 emissions. The basis of this assessment is the comparative inventory of technological and economic measures including efficiency improvement, conservation, enhanced use of low-carbon fuels, carbon free sources of energy and measures for removing carbon from fuels, flue gases and also from the atmosphere such as afforestation, and finally also measures for enhancement of carbon sinks. To include all potential options, the comparison is based on energy end-use accounting for the fully interlinked energy conversion chain up to energy resources. The analysis is supported by a fully interactive data bank system, CO2DB, that is capable of evaluating full energy chains with respect to their economic, technical and environmental parameters. The paper reports energy requirements, cost and CO 2 emissions for different energy chains providing industrial drives, cooling and air transport services. At additional cost, emissions can be reduced drastically on all these end-use categories.