Forest Carbon Sink Research Articles

Near-term investments in forest management support long-term carbon sequestration capacity in forests of the United States.

The forest carbon sink of the United States offsets emissions in other sectors. Recently passed US laws include important climate legislation for wildfire reduction, forest restoration, and forest planting. In this study, we examine how wildfire reduction strategies and planting might alter the forest carbon sink. Our results suggest that wildfire reduction strategies reduce carbon sequestration potential in the near term but provide a longer term benefit. Planting initiatives increase carbon sequestration but at levels that do not offset lost sequestration from wildfire reduction strategies. We conclude that recent legislation may increase near-term carbon emissions due to fuel treatments and reduced wildfire frequency and intensity, and expand long-term US carbon sink strength.

Future forestation in China should aim to align the temporal service window of the forest carbon sink with the “carbon neutrality” strategy

Future forestation in China should aim to align the temporal service window of the forest carbon sink with the “carbon neutrality” strategy

Measurement of the fair value of forest carbon sinks – Taking Yixing National Forest Park as an example

Management of forest carbon sinks can be viewed as a strategy to deal with climate change. To promote the establishment and improvement of the forest carbon market, it is important to measure the economic benefits of China’s existing forest carbon sinks with special weighting to forests along with protection of nature. Objectively measuring the value of a carbon sink is an important prerequisite to play the role of forest carbon pool and improve the efficiency of carbon sinks. This paper considers the strategy and process of forest carbon sink value accounting from two aspects of forest carbon storage and value, puts forward a set of forest carbon sink fair value accounting ideas, and considers Yixing forest farm as the research area. The following methods were used to compare the forest carbon stock of the Yixing National Forest Park. First, the economic benefits of forest carbon sink were evaluated with a market approach and carbon fair value. Next, the biomass expansion factor method and income approach were used to compute the forest carbon stock of Yixing National Forest Park, indicating a high carbon fair value.

Hopf Bifurcation Analysis of a Class of Saperda populnea Infectious Disease Model with Delay

Under the background of double carbon, it is important to study forest pests and diseases to improve forest carbon sink. In this paper, we establish a delayed model associated with the larvae and adults of Saperda populnea, susceptible poplars, and infected poplars. First, we analyze the existence and stability of the equilibrium of the model. Second, we study the existence of Hopf bifurcation near the equilibrium and obtain the normal form of Hopf bifurcation by the multiple time scales method. Then, we analyze the direction and stability of Hopf bifurcating periodic solutions. Third, we analyze and conjecture some parameter values based on official data, and carry out numerical simulations to verify our results. Finally, we give some suggestions on the prevention and control of Saperda populnea.

Forestation at the right time with the right species can generate persistent carbon benefits in China

Previous evaluations on the biophysical potential of forest carbon sink have focused on forestation area distribution and the associated carbon stock for equilibrium-state forests after centuries-long growth. These approaches, however, have limited relevance for climate policies because they ignore the near-term and mid-term decadal carbon uptake dynamics and suitable forest species for forestation. This study developed a forestation roadmap to support China's "carbon neutrality" objective in 2060 by addressing three key questions of forestation: where, with what forest species, and when to afforest. The results yielded a high-confidence potential forestation map for China at a resolution of 1 km with the identified optimal native forest type or species. Our analysis revealed an additional 78 Mha suitable for forestation up to the 2060s, a 43% increase on the current forest area. Selecting forest species for maximal carbon stock in addition to maximizing local environmental suitability enabled almost a doubling in forest carbon sink potential. Progressive forestation of this area can fix a considerable amount of CO2 and compensate for the carbon sink decline in existing forests. Altogether, the entire forest ecosystem can support a persistent biophysical carbon sink potential of 0.4 Pg C y-1 by 2060 and 0.2 Pg C y-1 by 2100, offsetting 7 to 14% of the current national fossil CO2 emissions. Our research provides an example of building a forestation roadmap toward a sustained forest carbon sink, which creates a critical time window for the emission cuts required by the goal of carbon neutrality.

A New Method for Reconstructing Tree-Level Aboveground Carbon Stocks of Eucalyptus Based on TLS Point Clouds

Eucalyptus plantation forests in southern China provide not only the economic value of producing timber, but also the ecological value service of absorbing carbon dioxide and releasing oxygen. Based on the theory of spatial colonial modeling, this paper proposes a new method for 3D reconstruction of tree terrestrial LiDAR point clouds for determining the aboveground carbon stock of eucalyptus monocotyledons, which consists of the main steps of tree branch and trunk separation, skeleton extraction and optimization, 3D reconstruction, and carbon stock calculation. The main trunk and branches of the tree point clouds are separated using a layer-by-layer judgment and clustering method, which avoids errors in judgment caused by sagging branches. By optimizing and adjusting the skeleton to remove small redundant branches, the near-parallel branches belonging to the same tree branch are fused. The missing parts of the skeleton point clouds were complemented using the cardinal curve interpolation algorithm, and finally a real 3D structural model was generated based on the complemented and smoothed tree skeleton expansion. The bidirectional Hausdoff distance, average Hausdoff distance, and F distance were used as evaluation indexes, which were reduced by 0.7453 m, 0.0028 m, and 0.0011 m, respectively, and the improved spatial colonization algorithm enhanced the accuracy of the reconstructed tree 3D structural model. To verify the accuracy of our method to determine the carbon stock and its related parameters, we cut down 41 eucalyptus trees and destructively sampled the measurement data as reference values. The R2 of the linear fit between the reconstructed single-tree aboveground carbon stock estimates and the reference values was 0.96 with a CV(RMSE) of 16.23%, the R2 of the linear fit between the trunk volume estimates and the reference values was 0.94 with a CV(RMSE) of 19.00%, and the R2 of the linear fit between the branch volume estimates and the reference values was 0.95 with a CV(RMSE) of 38.84%. In this paper, a new method for reconstructing eucalyptus carbon stocks based on TLS point clouds is proposed, which can provide decision support for forest management and administration, forest carbon sink trading, and emission reduction policy formulation.

Canary in the forest?—Tree mortality and canopy dieback of western redcedar linked to drier and warmer summers

AbstractAimForest dieback is increasing from unfavourable climate conditions. Western redcedar (WRC)—a culturally, ecologically and economically important species—has recently experienced anomalously high mortality rates and partial canopy dieback. We investigated how WRC tree growth and dieback responded to climate variability and drought using tree‐ring methods.LocationPacific Northwest, USA.TaxonWestern redcedar (Thuja plicata).MethodsWe collected tree cores from three tree health status groups (no canopy dieback, partial canopy dieback, and dead trees) at 11 sites in coastal (maritime climate) and interior (continental climate) WRC populations. From growth rates, we computed four growth indices that assessed the resilience to drought and estimated the year of death.ResultsWarmer and drier climate conditions in May/June that extended the annual July‐to‐September dry season reduced radial growth in 9 of 11 sites (1975–2020). WRC trees recovered growth to pre‐drought rates within 3 years when post‐drought climate conditions were cooler/wetter than average. However, recovery from drought was slower or absent when warmer/drier conditions occurred during the post‐drought recovery period, possibly leading to the recent and widespread mortality across the coastal population. WRC mortality was portended by 4–5 years of declining growth. Annually‐resolved mortality in coastal populations predominately occurred in 2017–2018 (80% of sampled dead trees), a period that coincided with exceedingly hot temperatures and the longest regionally dry period from May to September (1970–2020). In interior populations, mortality was dispersed among years but associated with warmer and drier conditions from August to September.Main conclusionsOur findings forewarn that a warming climate and more frequent and severe summer droughts, especially in consecutive years, will likely increase the vulnerability of WRC to canopy dieback and mortality and possibly other drought‐sensitive trees in one of the world's largest forest carbon sinks.

Maximum potential of vegetation carbon sink in Chinese forests

Forest vegetation is essential in sequestering carbon dioxide (CO2) from the atmosphere and mediating global warming. The carbon (C) sink potential of forest vegetation in different provinces is vital for policymakers to develop C-neutral technical routes and regional priorities in China; however, the mechanism remains unclear. In this study, we compiled the public data on forest vegetation biomass or storage along forest succession series between 2003 and 2022 and obtained the spatial variation of the maximum C storage(BCmax) of forest vegetation using classic logistic equation and nonlinear fitting. Furthermore, the C sink potential (∆Cpot) of the Chinese forest vegetation was calculated based on the differences between the BCmax and intensive field-investigated data in the 2010s. The results showed that the BCmax in the Chinese forest vegetation was approximately 19.03 Pg. The BCmax in southwest and northeast China were higher than those in other regions. The ∆Cpot was estimated as 8.83 Pg. Moreover, 1 km × 1 km spatial raster data for ∆Cpot were produced using the spatial raster calculation. Similarly, the per capita ∆Cpot of regions with low economic development (southwest, central, and southern Chinese provinces) were five to ten times higher than those of regions with a higher economic level. The ∆Cpot correlated negatively with gross domestic product (GDP)across all Chinese provinces. Our findings provide new insights into the ∆Cpot of the Chinese forest vegetation under natural restoration and emphasize that some differences in financial and political support among different provinces facilitate achieving a large ∆Cpot for C neutrality.

A study of forest management plans based on single-objective optimization

The global decline in forest area and massive greenhouse gas emissions have increased concern about the scale of forest carbon sinks, but the social value of forests as a source of timber and of forests themselves for tourism is also a focus of attention. The balance between forest carbon sinks and other values becomes a research question in this paper. We propose a forest management plan for forest managers by developing a carbon sink model and a forest management decision model. First, we developed a carbon sequestration model to determine how much carbon dioxide can be sequestered by the forest and its products over time. Then, we developed a single-objective optimization model with the goal of maximizing the amount of carbon sequestered. To develop a forest management plan, we selected six influencing factors: carbon storage, forest trees and their products, biodiversity, soil water storage, climate regulation, and landscape value, and then used hierarchical analysis to determine the influence weights of each factor, and then built a forest management decision model based on the single-objective optimization model. For specific forests, we initialize the model with specific parameters of the influencing factors and determine the transition points so that the model can be suitable for diverse forests and make a targeted management plan.

A linear positive relationship between tree species diversity and forest productivity across forest-dominated natural reserves on a large spatial scale

Exploring diversity-productivity relationships (DPRs) of various ecosystems is essential to forest management and conservation, as it can inform us about the dynamics and future trend of forest productivity and carbon sequestration under the change of species diversity. However, the DPR of natural reserve and its formation mechanisms are poorly understood, although such ecosystem plays a key role in protecting species diversity and maintaining carbon sink and other ecological service functions. By integrating ground survey data of 113,007 trees of 163 tree species from 1029 plots and remotely sensed vegetation data, we investigated the DPR features as well as the mechanisms behind them of 25 forest-dominated national natural reserves across the large part of northeastern China. We found a significant (P < 0.01) positive relationship between species diversity index and aboveground biomass across the analyzed natural reserves on a large spatial scale. In addition, the species diversity index and aboveground biomass obtained from the ground survey data were significantly (P < 0.01) and positively correlated with satellite-derived enhanced vegetation index linked to forest productivity, further confirming the robustness of the linear positive DPR observed. These results indicate that forest productivity and carbon sequestration would probably decline if a decrease in tree species number, highlighting the importance of species diversity protection in natural reserves. A structural equation modeling analysis suggested that heat-related and water-related climate factors played predominant roles in modulating species diversity index and aboveground biomass respectively and hence DPR across the natural reserves studied. Meanwhile, geographical location (i.e. latitude and longitude) can indirectly affect DPR by regulating the climate factors above. The findings of this study can contribute to understanding the DPR and predicting the future trends of forest carbon sink under climate change and thus to sustainable forest management for our study region as well as other similar natural reserves.

China’s current forest age structure will lead to weakened carbon sinks in the near future

Forests are chiefly responsible for the terrestrial carbon sink that greatly reduces the buildup of CO2 concentrations in the atmosphere and alleviates climate change. Current predictions of terrestrial carbon sinks in the future have so far ignored the variation of forest carbon uptake with forest age. Here, we predict the role of China's current forest age in future carbon sink capacity by generating a high-resolution (30 m) forest age map in 2019 over China's landmass using satellite and forest inventory data and deriving forest growth curves using measurements of forest biomass and age in 3,121 plots. As China's forests currently have large proportions of young and middle-age stands, we project that China's forests will maintain high growth rates for about 15 years. However, as the forests grow older, their net primary productivity will decline by 5.0%± 1.4% in 2050, 8.4%± 1.6% in 2060, and 16.6%± 2.8% in 2100, indicating weakened carbon sinks in the near future. The weakening of forest carbon sinks can be potentially mitigated by optimizing forest age structure through selective logging and implementing new or improved afforestation. This finding is important not only for the global carbon cycle and climate projections but also for developing forest management strategies to enhance land sinks by alleviating the age effect.

Is Regulation Protection? Forest Logging Quota Impact on Forest Carbon Sinks in China

As the central part of terrestrial ecosystems, forests have an irreplaceable role in regulating climate, prompting various efforts to protect them. Logging regulation is the most commonly used forest conservation strategy. Although the logging permit scheme was written into the Forest Law in China, its effect on forest carbon sequestration has rarely been subject to careful empirical scrutiny. In this paper, we develop and estimate a spatial econometric model to disentangle its potential effects on forest carbon sinks based on a panel dataset of 29 provinces from 1989 to 2018 in China. Our calculations show that China’s forest carbon sinks are still growing and are connected geographically, with a tendency towards “high-high” and “low-low” aggregation. Increasing the logging quota produced a spatial spillover effect that might encourage the formation of forest carbon sinks in nearby areas. It considerably encouraged the expansion of forest carbon sinks. Additional mechanism testing is consistent with the claim that rising logging quotas have significantly boosted the proportion of timber forests in afforestation but had no effect on the movement of rural labor to urban areas. The development of forest carbon sinks is impacted in different ways by various logging quota types, with an increasing tendency for logging quotas to have a more significant contribution. Additionally, the non-collective forest region has a more significant spatial spillover effect of the logging quota on forest carbon sinks. The logging quota scheme should be improved by policymakers, beginning with eliminating tending quotas in the southern collective forest region. After that, the logging quota would gradually be eliminated nationwide, notably for commercial forests.

Spatiotemporal Trends of Forest Carbon Stock and Its Response to Environmental Factors in the Yangtze River Basin during 2005–2020

It is of great significance to accurately assess the carbon sink capacity and trend of forest ecosystems on a regional scale, which is a key step to realizing sustainable forest management and carbon sink. Based on several remote sensing datasets, this study analyzes the dynamic characteristics of forest carbon stock in the Yangtze River Basin and its response to environmental factors using the Mann–Kendall nonparametric test, correlation analysis, and BP neural network during 2005–2020. The results show that forest carbon stock in the Yangtze River Basin shows a fluctuating upward trend, with an average annual growth rate of 0.91%. Forest carbon stock in western high-altitude areas and areas with high human activity in the east showed a downward trend, while the central plains showed a stable growth trend. In the vast plains of the Yangtze River Basin, a suitable drought degree (−0.5 &lt; SPEI &lt; 0.5) is helpful to the accumulation of forest carbon reserves. In the future, rich forest resources should be fully developed to promote synergy between environmental protection and economic development from the perspective of developing green carbon trading, such as the carbon-sink forestry projects of CCER.

DUAL PERSPECTIVE DIAGNOSIS ON LOW CARBON CITY PERFORMANCE

ABSTRACT Developing low-carbon cities (LCC) is a strategic measure to mitigate climate change. This study proposes to diagnose LCC performance from a dual perspective in order to identify problematic areas for improvement. The dual perspective refers to management processes (including Plan, Do, Check, and Act) and low carbon city performance dimensions (namely, energy structure, economic development, production efficiency, urban population, water carbon sink, forest carbon sink, green space carbon sink, and low carbon technology). A diagnosis model has been introduced based on the dimension-process dual perspective. The model has been applied for diagnosing the LCC performance in four municipalities in China. It has been found that the performance in the economic development dimension is much better than in other LCC dimensions, and the performance in Plan and Do stages are better than that in other stages. This reflects the traditional practice in China where more attention and resources are often given to urban planning and implementation with less attention to checks and feedback. The findings from this study provide important references for both further research in the discipline and practical application in promoting LCC in other cities.

Building capacity for estimating fire emissions from tropical peatlands; a worked example from Indonesia

Tropical peatlands are globally significant in the terrestrial carbon cycle as they are comprised of a large forest carbon sink and a large peat carbon store—both of which can potentially be exchanged with the atmosphere on decadal time frames. Greenhouse gas emissions from fire-disturbance and development of tropical peatlands over the last few decades, and the potential for ongoing emissions, highlights the need for policy to slow or halt emissions and to activate mechanisms to sequester carbon through restoration of degraded peatlands. The UN REDD + scheme provides a means for developing countries to receive payments for avoided deforestation and forest degradation, but the steps to achieve REDD+ compliance are rigorous and the details required can be a barrier to activating benefits—especially for peatlands where repeated cycles of fire interrupt forest recovery and create a range of recovery classes. Therefore, to improve estimates of peat fire emissions and of carbon balance of tropical peatlands, the biomass and combustion factor parameters need to be developed and applied according to forest recovery stage. In this study we use published activity data from the extensive 1997 fires in the peatlands of Indonesian Borneo to detail a transparent and accountable way to estimate and report emissions from tropical peatland fires. This example for estimating and reporting emissions is provided to assist REDD+ countries to efficiently develop their capacity for improving emissions estimates from fire-impacted tropical peatlands.

Sensitivity of South American tropical forests to an extreme climate anomaly

The tropical forest carbon sink is known to be drought sensitive, but it is unclear which forests are the most vulnerable to extreme events. Forests with hotter and drier baseline conditions may be protected by prior adaptation, or more vulnerable because they operate closer to physiological limits. Here we report that forests in drier South American climates experienced the greatest impacts of the 2015–2016 El Niño, indicating greater vulnerability to extreme temperatures and drought. The long-term, ground-measured tree-by-tree responses of 123 forest plots across tropical South America show that the biomass carbon sink ceased during the event with carbon balance becoming indistinguishable from zero (−0.02 ± 0.37 Mg C ha−1 per year). However, intact tropical South American forests overall were no more sensitive to the extreme 2015–2016 El Niño than to previous less intense events, remaining a key defence against climate change as long as they are protected.

Who benefits from payments for ecosystem services? Policy lessons from a forest carbon sink program in China

To secure effective and sustainable climate change policies, it is of the utmost importance to create synergies between socioeconomic and environmental development goals. Payments for Ecosystem Services (PES) programs are being promoted as a suitable mechanism furthering, among others, carbon offsetting and poverty reduction in ecologically fragile areas of developing countries. Rural households are compensated for the loss of property and business income through income transfers and potential job opportunities connected to environmental programs. While the potential pro-poor effects of such policies are well recognized, the impact of PES on extremely poor households has not been systematically reviewed. Drawing on a pooled cross-sectional dataset of 5225 households in the Province of Sichuan, this paper analyzes the income and distributional effects among poor households in rural China participating in a forest carbon sink (FCS) program. To be able to make causal inferences, we employ an Instrumental Variable (IV) approach to control for potential endogeneity and self-selection. Our results indicate a strong need to adjust the PES program: While moderately poor rural households benefit from program participation, extremely poor rural households, in fact, suffer net losses. The main reason is that income reduction resulting from limited access to forest resources is compensated mainly via wage income from participating in forest tending work. Extremely poor households with low labor ability cannot make use of these job opportunities, and thus they'll not only fail to benefit but even incur losses from a PES program. While PES programs can be a viable tool for poverty reduction in underdeveloped regions due to their overall pro-poorness, they need to be accompanied by additional benefits for extremely poor rural households to avoid net losses among marginalized population groups especially.

Mathematical Modeling and Stability Analysis of the Delayed Pine Wilt Disease Model Related to Prevention and Control

Forest pests and diseases have been seriously threatening ecological security. Effective prevention and control of such threats can extend the growth cycle of forest trees and increase the amount of forest carbon sink, which makes a contribution to achieving China’s goal of “emission peak and carbon neutrality”. In this paper, based on the insect-vector populations (this refers to Monochamus alternatus, which is the main vector in Asia) in pine wilt disease, we establish a two-dimensional delay differential equation model to investigate disease control and the impact of time delay on the effectiveness of it. Then, we analyze the existence and stability of the equilibrium of the system and the existence of Hopf bifurcation, derive the normal form of Hopf bifurcation by using a multiple time scales method, and conduct numerical simulations with realistic parameters to verify the correctness of the theoretical analysis. Eventually, according to theoretical analysis and numerical simulations, some specific suggestions are put forward for prevention and control of pine wilt disease.

Higher site productivity and stand age enhance forest susceptibility to drought-induced mortality

Warmer and drier conditions increase forest mortality worldwide. At the same time, nitrogen deposition, longer growing seasons and higher atmospheric CO2 concentrations may increase site productivity accelerating forest growth. However, tree physiological studies suggest that increased site productivity can also have adverse effects, reducing adaptation to drought. Understanding such intricate interactions that might foster tree mortality is essential for designing activities and policies aimed at preserving forests and the ecosystem services they provide. This study shows how site factors and stand features affect the susceptibility of Scots pine to drought-induced stand-level mortality. We use extensive forest data covering 750,000 ha, including 47,450 managed Scots pine stands, of which 2,547 were affected by mortality during the drought in 2015–2019. We found that the oldest and most dense stands growing on the most productive sites showed the highest susceptibility to enhanced mortality during drought. Our findings suggest that increasing site productivity may accelerate the intensity and prevalence of drought-induced forest mortality. Therefore, climate change may increase mortality, particularly in old and high-productive forests. Such exacerbated susceptibility to mortality should be considered in forest carbon sink projections, forest management, and policies designed to increase resilience and protect forest ecosystems.

Increased Amazon carbon emissions mainly from decline in law enforcement.

The Amazon forest carbon sink is declining, mainly as a result of land-use and climate change1-4. Here we investigate how changes in law enforcement of environmental protection policies may have affected the Amazonian carbon balance between 2010 and 2018 compared with 2019 and 2020, based on atmospheric CO2 vertical profiles5,6, deforestation7 and fire data8, as well as infraction notices related to illegal deforestation9. We estimate that Amazonia carbon emissions increased from a mean of 0.24 ± 0.08 PgC year-1 in 2010-2018 to 0.44 ± 0.10 PgC year-1 in 2019 and 0.52 ± 0.10 PgC year-1 in 2020 (±uncertainty). The observed increases in deforestation were 82% and 77% (94% accuracy) and burned area were 14% and 42% in 2019 and 2020 compared with the 2010-2018 mean, respectively. We find that the numbers of notifications of infractions against flora decreased by 30% and 54% and fines paid by 74% and 89% in 2019 and 2020, respectively. Carbon losses during 2019-2020 were comparable withthose of the record warm El Niño (2015-2016) without an extreme drought event. Statistical tests show that the observed differences between the 2010-2018 mean and 2019-2020 are unlikely to have arisen by chance. The changes in the carbon budget of Amazonia during 2019-2020 were mainly because of western Amazonia becoming a carbon source. Our results indicate that a decline in law enforcement led to increases in deforestation, biomass burning and forest degradation, which increased carbon emissions and enhanced drying and warming of the Amazon forests.