Natural forests are the primary carbon sinks within terrestrial ecosystems,playing a crucial role in mitigating global climate change.China has successfully restored its natural forest area through extensive protectiv...Natural forests are the primary carbon sinks within terrestrial ecosystems,playing a crucial role in mitigating global climate change.China has successfully restored its natural forest area through extensive protective measures.However,the aboveground carbon(AGC)stock potential of China's natural forests remains considerably uncertain in spatial and temporal dynamics.In this study,we provide a spatially detailed estimation of the maximum AGC stock potential for China's natural forests by integrating high-resolution multi-source remote sensing and field survey data.The analysis reveals that China's natural forests could sequester up to 9.880.10 Pg C by 2030,potentially increasing to 10.460.11 Pg C by 2060.Despite this,the AGC sequestration rate would decline from 0.190.001 to 0.080.001 Pg C·yr^(-1)over the period.Spatially,the future AGC accumulation rates exhibit marked heterogeneity.The warm temperate deciduous broadleaf forest region with predominantly young natural forests,is expected to exhibit the most significant increase of 26.36%by 2060,while the Qinghai-Tibet Plateau Alpine region comprising mainly mature natural forests would exhibit only a 0.74%increase.To sustain the high carbon sequestration capacity of China's natural forests,it is essential to prioritize protecting mature forests alongside preserving and restoring young natural forest areas.展开更多
Most research on carbon storage in forests has focused on qualitative studies of carbon storage and influ-encing factors rather than on quantifying the effect of the spatial distribution of carbon storage and of its i...Most research on carbon storage in forests has focused on qualitative studies of carbon storage and influ-encing factors rather than on quantifying the effect of the spatial distribution of carbon storage and of its influencing factors at different scales.Here we described the spatial dis-tribution of aboveground carbon storage(ACS)in a 20-ha plot in a subtropical evergreen broad-leaved forest to evalu-ate and quantify the relative effects of biotic factors(species diversity and structural diversity)and abiotic factors(soil and topographic factors)on ACS at different scales.Scale effects of the spatial distribution of ACS were significant,with higher variability at smaller scales,but less at larger scales.The distribution was also spatially heterogeneous,with more carbon storage on north-and east-facing slopes than on south-and west-facing slopes.At a smaller scale,species diversity and structural diversity each had a direct positive impact on ACS,but soil factors had no significant direct impact.At increasing scales,topographic and soil fac-tors gradually had a greater direct influence,whereas the influence of species diversity gradually decreased.Structural diversity had the greatest impact,followed by topographic factors and soil factors,while species diversity had a rela-tively smaller impact.These findings suggest studies on ACS in subtropical evergreen broadleaf forests in southern China should consider scale effects,specifically on the heterogene-ity of ACS distribution at small scales.Studies and conser-vation efforts need to focus on smaller habitat types with particular emphasis on habitat factors such as aspect and soil conditions,which have significant influences on community species diversity,structural diversity,and ACS distribution.展开更多
Greenhouse gas emission of carbon dioxide（CO2） is one of the major factors causing global climate change.Urban green space plays a key role in regulating the global carbon cycle and reducing atmospheric CO2.Quantify...Greenhouse gas emission of carbon dioxide（CO2） is one of the major factors causing global climate change.Urban green space plays a key role in regulating the global carbon cycle and reducing atmospheric CO2.Quantifying the carbon stock,distribution and change of urban green space is vital to understanding the role of urban green space in the urban environment.Remote sensing is a valuable and effective tool for monitoring and estimating aboveground carbon（AGC） stock in large areas.In the present study,different remotely-sensed vegetation indices（VIs） were used to develop a regression equation between VI and AGC stock of urban green space,and the best fit model was then used to estimate the AGC stock of urban green space within the beltways of Xi＇an city for the years 2004 and 2010.A map of changes in the spatial distribution patterns of AGC stock was plotted and the possible causes of these changes were analyzed.Results showed that Normalized Difference Vegetation Index（NDVI） correlated moderately well with AGC stock in urban green space.The Difference Vegetation Index（DVI）,Ratio Vegetation Index（RVI）,Soil Adjusted Vegetation Index（SAVI）,Modified Soil Adjusted Vegetation Index（MSAVI） and Renormalized Difference Vegetative Index（RDVI） were lower correlation coefficients than NDVI.The AGC stock in the urban green space of Xi＇an in 2004 and 2010 was 73,843 and 126,621 t,respectively,with an average annual growth of 8,796 t and an average annual growth rate of 11.9%.The carbon densities in 2004 and 2010 were 1.62 and 2.77 t/hm2,respectively.Precipitation was not an important factor to influence the changes of AGC stock in the urban green space of Xi＇an.Policy orientation,major ecological greening projects such as ＂transplanting big trees into the city＂ and the World Horticultural Exposition were found to have an important impact on changes in the spatiotemporal patterns of AGC stock.展开更多
Alpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River.However,due to continuous high-intensity harvesting,a large number of plantings,and the complet...Alpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River.However,due to continuous high-intensity harvesting,a large number of plantings,and the complete harvesting ban measures in recent decades,the forest tree species and age cohorts have become relatively homogenous,and the biodiversity and ecological functions have been reduced.To design effective forest management options to optimize forest structure and increase carbon sequestration capacity,Mao County in Sichuan Province was selected as the study site and six forest management options(harvesting,planting)of different intensities were tested using the LANDIS-II model to simulate and compare the differences in forest aboveground carbon sequestration rate(ACSR)between these options and the current management option over the next 100 years.Our results showed that(i)the different harvesting and planting intensities significantly changed the ACSR compared with the current management options;(ii)different communities responded differently to the management options,with the ACSR differing significantly in cold temperate conifers and temperate conifers but not in broad-leaved trees(P<0.05);and(iii)a comprehensive consideration of forest management options at the species,community and landscape levels was necessary.Our results suggest that implementing a longer harvesting and planting interval(20 years)at the study site can maximize forest ACSR.This study provides an important reference for evaluating the ability of forest management options to restore forest ecological functions and increase carbon sequestration capacity and for selecting effective forest management programs in the eastern Tibetan Plateau.展开更多
Forests are among the most important carbon sinks on earth. However, their complex structure and vast areas preclude accurate estimation of forest carbon stocks.Data sets from forest monitoring using advanced satellit...Forests are among the most important carbon sinks on earth. However, their complex structure and vast areas preclude accurate estimation of forest carbon stocks.Data sets from forest monitoring using advanced satellite imagery are now used in international policy agreements.Data sets enable tracking of emissions of COinto the atmosphere caused by deforestation and other types of land-use changes. The aim of this study is to determine the capability of SPOT-HRG Satellite data to estimate aboveground carbon stock in a district of Darabkola research and training forest, Iran. Preprocessing to eliminate or reduce geometric error and atmospheric error were performed on the images. Using cluster sampling, 165 sample plots were taken. Of 165 plots, 81 were in natural habitats, and 84 were in forest plantations. Following the collection of ground data, biomass and carbon stocks were quantified for the sample plots on a per hectare basis. Nonparametric regression models such as support vector regression were used for modeling purposes with different kernels including linear, sigmoid, polynomial, and radial basis function.The results showed that a third-degree polynomial was the best model for the entire studied areas having an root mean square error, bias and accuracy, respectively, of 38.41,5.31, and 62.2; 42.77, 16.58, and 57.3% for the best polynomial for natural forest; and 44.71, 2.31, and 64.3%for afforestation. Overall, these results indicate that SPOTHRG satellite data and support vector machines are useful for estimating aboveground carbon stock.展开更多
Over the past 4 decades,Southwest China has the fast vegetation growth and aboveground biomass carbon(AGC)accumulation,largely attributed to the active implementation of ecological projects.However,Southwest China has...Over the past 4 decades,Southwest China has the fast vegetation growth and aboveground biomass carbon(AGC)accumulation,largely attributed to the active implementation of ecological projects.However,Southwest China has been threatened by frequent extreme drought events recently,potentially countering the expected large AGC increase caused by the ecological projects.Here,we used the L-band vegetation optical depth to quantify the AGC dynamics over Southwest China during the period 2013-2021.Our results showed a net AGC sink of 0.064[0.057,0.077]Pg C year^(−1)(the range represents the maximum and minimum AGC values),suggesting that Southwest China acted as an AGC sink over the study period.Note that the AGC loss of 0.113[0.101,0.136]Pg C year^(−1)was found during 2013-2014,which could mainly be attributed to the negative influence of extreme droughts on AGC changes in Southwest China,particularly in the Yunnan province.For each land use type(i.e.,dense forests,persistent forests,nonforests,afforestation,and forestry),the largest AGC stock increase of 0.032[0.028,0.036]Pg C year^(−1)was found in nonforests,owing to their widespread land cover rate over Southwest China.For AGC density(i.e.,AGC per unit area),the afforestation areas showed the largest AGC density increase of 0.808[0.724,0.985]Mg C ha−1 year^(−1),reflecting the positive effect of afforestation on AGC increase.Moreover,the karst areas exhibited a higher increasing rate of AGC density than nonkarst areas,suggesting that the karst ecosystems have a high carbon sink capacity over Southwest China.展开更多
This study developed allometric models to estimate aboveground biomass and carbon of Prosopis africana and Faidherbia albida. The destructive method was used with a sample of 20 trees per species for the two parkland ...This study developed allometric models to estimate aboveground biomass and carbon of Prosopis africana and Faidherbia albida. The destructive method was used with a sample of 20 trees per species for the two parkland sites. Linear regression with log transformation was used to model aboveground biomass according to dendrometric parameters. Error analysis, including mean absolute percentage of error(MAPE) and root mean square of error(RMSE), was used to select and validate the models for both species. Model 1(biomass according to tree diameter) for P. africana and F. albida were considered more representative. The statistical parameters of these models were R2 = 0.99, MAPE 0.98% and RMSE1.75% for P. africana, and R2 = 0.99, MAPE 1.19%,RMSE 2.37% for F. albida. The average rate of carbon sequestered was significantly different for the two species(P ≤ 0.05). The total amount sequestered per tree averaged0.17 × 10-3 Mg for P. africana and 0.25 × 10-3 Mg for F. albida. These results could be used to develop policies that would lead to the sustainable management of these resources in the dry parklands of Niger.展开更多
A study was conducted to assess carbon stocks in various forms and land-use types and reliably estimate the impact of land use on C stocks in the Nam Yao sub-watershed （19°05′10″N, 100°37′02″E）, Thaila...A study was conducted to assess carbon stocks in various forms and land-use types and reliably estimate the impact of land use on C stocks in the Nam Yao sub-watershed （19°05′10″N, 100°37′02″E）, Thailand. The carbon stocks of aboveground, soil organic and fine root within primary forest, reforestation and agricultural land were estimated through field data collection. Results re- vealed that the amount of total carbon stock of forests （357.62 ± 28.51 Mg·ha^-1, simplified expression of Mg （carbon）·ha^-1） was significantly greater （P〈 0.05） than the reforestation （195.25 ± 14.38 Mg·ha^-1） and the agricultural land （103.10 ± 18.24 Mg·ha^-1）. Soil organic carbon in the forests （196.24 ± 22.81 Mg·ha^-1） was also significantly greater （P〈 0.05） than the reforestation （146.83 ± 7.22 Mg·ha^-1） and the agricultural land （95.09± 14.18 Mg·ha^-1）. The differences in carbon stocks across land-use types are the primary consequence of variations in the vegetation biomass and the soil organic matter. Fine root carbon was a small fraction of carbon stocks in all land-use types. Most of the soil organic carbon and fine root carbon content was found in the upper 40-cm layer and decreased with soil depth. The aboveground carbon：soil organic carbon： fine root carbon ratios （ABGC： SOC： FRC）, was 5：8：1, 2：8：1, and 3：50：1 for the forest, reforestation and agricultural land, respectively. These results indicate that a relatively large proportion of the C loss is due to forest conversion to agricultural land. However, the C can be effectively recaptured through reforestation where high levels of C are stored in biomass as carbon sinks, facilitating carbon dioxide mitigation.展开更多
Forest ecosystems play a crucial role in mitigating global climate change by forming massive carbon sinks. Their carbon stocks and stock changes need to be quantified for carbon budget balancing and international repo...Forest ecosystems play a crucial role in mitigating global climate change by forming massive carbon sinks. Their carbon stocks and stock changes need to be quantified for carbon budget balancing and international reporting schemes. However, direct sampling and biomass weighing may not always be possible for quantification studies conducted in large forests. In these cases, indirect methods that use forest inventory information combined with remote sensing data can be beneficial. Synthetic aperture radar (SAR) images offer numerous opportunities to researchers as freely distributed remote sensing data. This study aims to estimate the amount of total carbon stock (TCS) in forested lands of the Kizildag Forest Enterprise. To this end, the actual storage capacities of five carbon pools, i.e. above- and below-ground, deadwood, litter, and soil, were calculated using the indirect method based on ground measurements of 264 forest inventory plots. They were then associated with the backscattered values from Sentinel-1 and ALOS-2 PALSAR-2 data in a Geographical Information System (GIS). Finally, TCS was separately modelled and mapped. The best regression model was developed using the HH polarization of ALOS-2 PALSAR-2 with an adjusted R^(2) of 0.78 (p < 0.05). According to the model, the estimated TCS was about 2 Mt for the entire forest, with an average carbon storage of 133 t ha^(−1). The map showed that the distribution of TCS was heterogenic across the study area. Carbon hotspots were mostly composed of pure stands of Anatolian black pine and mixed, over-mature stands of Lebanese cedar and Taurus fir. It was concluded that the total carbon stocks of forest ecosystems could be estimated using appropriate SAR images at acceptable accuracy levels for forestry purposes. The use of additional ancillary data may provide more delicate and reliable estimations in the future. Given the implications of this study, the spatiotemporal dynamics of carbon can be effectively controlled by forest management when coupled with easily accessible space-borne radar data.展开更多
Assessing the changes in forest carbon stocks over time is critical for monitoring carbon dynamics,estimating the balance between carbon uptake and release from forests,and providing key insights into climate change m...Assessing the changes in forest carbon stocks over time is critical for monitoring carbon dynamics,estimating the balance between carbon uptake and release from forests,and providing key insights into climate change mitigation.In this study,we quantitatively characterized spatiotemporal variations in aboveground carbon density(ACD)in boreal natural forests in the Greater Khingan Mountains(GKM)region using bi-temporal discrete aerial laser scanning(ALS)data acquired in 2012 and 2016.Moreover,we evaluated the transferability of the proposed design model using forest field plot data and produced a wall-to-wall map of ACD changes for the entire study area from 2012 to 2016 at a grid size of 30 m.In addition,we investigated the relationships between carbon dynamics and the dominant tree species,age groups,and topography of undisturbed forested areas to better understand ACD variations by employing heterogeneous forest canopy structural characteristics.The results showed that the performance of the temporally transferable model(R^(2)=0.87,rRMSE=18.25%),which included stable variables,was statistically equivalent to that obtained from the model fitted directly by the 2016 field plots(R^(2)=0.87,rRMSE=17.47%).The average rate of change in carbon sequestration across the entire study region was 1.35 Mg⋅ha^(-1)⋅year^(-1) based on the changes in ALS-based ACD values over the course of four years.The relative change rates of ACD decreased as the elevation increased,with the highest and lowest ACD growth rates occurring in the middle-aged and mature forest stands,respectively.The Gini coefficient,which represents forest canopy surface structure heterogeneity,is sensitive to carbon dynamics and is a reliable predictor of the relative change rate of ACD.This study demonstrated the applicability of bi-temporal ALS for predicting forest carbon dynamics and fine-scale spatial change patterns.Our research contributed to a better understanding of the in-fluence of remote sensing-derived environmental variables on forest carbon dynamic patterns and the development of context-specific management approaches to increase forest carbon stocks.展开更多
Canadian boreal mixedwood forests are extensive,with large potential for carbon sequestration and storage;thus,knowledge of their carbon stocks at different stand ages is needed to adapt forest management practices to...Canadian boreal mixedwood forests are extensive,with large potential for carbon sequestration and storage;thus,knowledge of their carbon stocks at different stand ages is needed to adapt forest management practices to help meet climate-change mitigation goals.Carbon stocks were quantified at three Ontario boreal mixedwood sites.A harvested stand,a juvenile stand replanted with spruce seedlings and a mature stand had total carbon stocks(±SE)of 133±13 at age 2,130±13 at age 25,and 207±15 Mg C ha^-1 at age 81 years.At the clear-cut site,stocks were reduced by about 40%or 90 Mg C ha^-1 at harvest.Vegetation held 27,34 and 62%of stocks,while detritus held 34,29 and 13%of stocks at age 2,25 and 81,respectively.Mineral soil carbon stocks averaged 51 Mg C ha^-1,and held 38,37 and 25%of stocks.Aboveground net primary productivity(±SE)in the harvested and juvenile stand was 2.1±0.2 and 3.7±0.3 Mg C ha^-1 per annum(p.a.),compared to 2.6±2.5 Mg C ha^-1 p.a.in the mature stand.The mature canopies studied had typical boreal mixedwood composition and mean carbon densities of 208 Mg C ha^-1,which is above average for managed Canadian boreal forest ecosystems.A comparison of published results from Canadian boreal forest ecosystems showed that carbon stocks in mixedwood stands are typically higher than coniferous stands at all ages,which was also true for stocks in vegetation and detritus.Also,aboveground net primary productivity was typically found to be higher in mixedwood than in coniferous boreal forest stands over a range of ages.Measurements from this study,together with those published from the other boreal forest stands demonstrate the potential for enhanced carbon sequestration through modified forest management practices to take advantage of Canadian boreal mixedwood stand characteristics.展开更多
Mount Kilimanjaro and the Taita Hills are adjacent montane areas that experience similar climate and agricultural activity, but which differ in their geologic history, nature of elevation gradients and cultures. We as...Mount Kilimanjaro and the Taita Hills are adjacent montane areas that experience similar climate and agricultural activity, but which differ in their geologic history, nature of elevation gradients and cultures. We assessed differences in cropland above ground carbon (AGC) between the two sites and against environmental variables. One hectare sampling plots were randomly distributed along elevational gradients stratified by cropland type;AGC was derived from all trees with diameter ≥ 10 cm at breast height in each plot. Predictor variables were physical and edaphic variables and human population. A generalized linear model was used for predicting AGC with AIC used for ranking models. AGC was spatially upscaled in 2 km buffer and visually compared. Kilimanjaro has higher AGC in cropped and agroforestry areas than the Taita Hills, but only significant difference in AGC variation in agroforestry areas (F = 9.36, p = 0.03). AGC in cropped land and agroforestry in Kilimanjaro has significant difference on mean (t = 4.62, p = 0.001) and variation (F = 17.41, p = 0.007). In the Taita Hills, significant difference is observed only on the mean AGC (t = 4.86, p = 0.001). Common tree species that contribute the most to AGC in Kilimanjaro are Albizia gummifera and Persea americana, and in the Taita Hills Grevillea robusta and Mangifera indica. Significant and univariate predictors of AGC in Mount Kilimanjaro are pH (R2 = 0.80, p = 0.00) and EVI (R2 = 0.68, p = 0.00). On Mount Kilimanjaro, the top multivariate model contained SOC, CEC, pH and BLD (R2 = 0.90, p = 0.00), whereas in the Taita Hills, the top multivariate model contained elevation, slope and population (R2 = 0.89, p = 0.00). Despite of the difference in land management history of Mount Kilimanjaro and the Taita Hills, mean of AGC in croplands does not differ significantly. Difference occurs on variation of AGC, type of trees contributing AGC, and environmental variables that explain AGC distribution. The research results provide reference for management of carbon sequestration on inhabited montane areas.展开更多
The aim of this study was to assess Acacia senegal trees’ characteristics as well as evaluate the carbon stock under a variety of ages in the El Demokeya forest in Sudan, where the Gum Arabic belt is located. 12 samp...The aim of this study was to assess Acacia senegal trees’ characteristics as well as evaluate the carbon stock under a variety of ages in the El Demokeya forest in Sudan, where the Gum Arabic belt is located. 12 sample plots, in 2021 were randomly distributed to represent the entire area of the forest prior to the required measurements. The sample was designed as squire plots with one hectare. In each sample plot, all trees were counted, their height (m), and Diameters Breast Height (DBH in cm), respectively. The results showed the highest number of trees per ha at age 20 years old and the lowest number at age 47 years, while the highest values of DBH and volume were found at age 47 years old. As a result, the maximum and minimum values of the aboveground biomass were found in the age 47 years old and 16 years, accounting for 19.87 tons and 1.9 tons respectively. Thus, the amount of carbon stock was 11.92 tons/ha in the 35-years-old and 1.19 tons/ha in the 21-year stands. Furthermore, the average carbon stock in all plots was estimated as 18.70 tons/ha and hence the total carbon stock in the El Demokeya forest is equal to 620.11 tons. Conclusively, the characteristics of trees, amount of aboveground biomass and carbon stock in the El Demokeya forest varied among the uneven-aged plantation groups. The study recommends and encourages the protection of A. senegal in order to increase the carbon sink as well as protect the environment in the era of climatic changes.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF1300203)the National Natural Science Foundation of China(Grant No.42371329s).
文摘Natural forests are the primary carbon sinks within terrestrial ecosystems,playing a crucial role in mitigating global climate change.China has successfully restored its natural forest area through extensive protective measures.However,the aboveground carbon(AGC)stock potential of China's natural forests remains considerably uncertain in spatial and temporal dynamics.In this study,we provide a spatially detailed estimation of the maximum AGC stock potential for China's natural forests by integrating high-resolution multi-source remote sensing and field survey data.The analysis reveals that China's natural forests could sequester up to 9.880.10 Pg C by 2030,potentially increasing to 10.460.11 Pg C by 2060.Despite this,the AGC sequestration rate would decline from 0.190.001 to 0.080.001 Pg C·yr^(-1)over the period.Spatially,the future AGC accumulation rates exhibit marked heterogeneity.The warm temperate deciduous broadleaf forest region with predominantly young natural forests,is expected to exhibit the most significant increase of 26.36%by 2060,while the Qinghai-Tibet Plateau Alpine region comprising mainly mature natural forests would exhibit only a 0.74%increase.To sustain the high carbon sequestration capacity of China's natural forests,it is essential to prioritize protecting mature forests alongside preserving and restoring young natural forest areas.
基金supported by the Guangxi Natural Science Foundation Program(2022GXNSFAA035583,2021GXNSFBA196052)the National Natural Science Foundation of China(32060305,32460270).
文摘Most research on carbon storage in forests has focused on qualitative studies of carbon storage and influ-encing factors rather than on quantifying the effect of the spatial distribution of carbon storage and of its influencing factors at different scales.Here we described the spatial dis-tribution of aboveground carbon storage(ACS)in a 20-ha plot in a subtropical evergreen broad-leaved forest to evalu-ate and quantify the relative effects of biotic factors(species diversity and structural diversity)and abiotic factors(soil and topographic factors)on ACS at different scales.Scale effects of the spatial distribution of ACS were significant,with higher variability at smaller scales,but less at larger scales.The distribution was also spatially heterogeneous,with more carbon storage on north-and east-facing slopes than on south-and west-facing slopes.At a smaller scale,species diversity and structural diversity each had a direct positive impact on ACS,but soil factors had no significant direct impact.At increasing scales,topographic and soil fac-tors gradually had a greater direct influence,whereas the influence of species diversity gradually decreased.Structural diversity had the greatest impact,followed by topographic factors and soil factors,while species diversity had a rela-tively smaller impact.These findings suggest studies on ACS in subtropical evergreen broadleaf forests in southern China should consider scale effects,specifically on the heterogene-ity of ACS distribution at small scales.Studies and conser-vation efforts need to focus on smaller habitat types with particular emphasis on habitat factors such as aspect and soil conditions,which have significant influences on community species diversity,structural diversity,and ACS distribution.
基金supported by the Forestry Research Foundation for the Public Service Industry of China (200904004)
文摘Greenhouse gas emission of carbon dioxide（CO2） is one of the major factors causing global climate change.Urban green space plays a key role in regulating the global carbon cycle and reducing atmospheric CO2.Quantifying the carbon stock,distribution and change of urban green space is vital to understanding the role of urban green space in the urban environment.Remote sensing is a valuable and effective tool for monitoring and estimating aboveground carbon（AGC） stock in large areas.In the present study,different remotely-sensed vegetation indices（VIs） were used to develop a regression equation between VI and AGC stock of urban green space,and the best fit model was then used to estimate the AGC stock of urban green space within the beltways of Xi＇an city for the years 2004 and 2010.A map of changes in the spatial distribution patterns of AGC stock was plotted and the possible causes of these changes were analyzed.Results showed that Normalized Difference Vegetation Index（NDVI） correlated moderately well with AGC stock in urban green space.The Difference Vegetation Index（DVI）,Ratio Vegetation Index（RVI）,Soil Adjusted Vegetation Index（SAVI）,Modified Soil Adjusted Vegetation Index（MSAVI） and Renormalized Difference Vegetative Index（RDVI） were lower correlation coefficients than NDVI.The AGC stock in the urban green space of Xi＇an in 2004 and 2010 was 73,843 and 126,621 t,respectively,with an average annual growth of 8,796 t and an average annual growth rate of 11.9%.The carbon densities in 2004 and 2010 were 1.62 and 2.77 t/hm2,respectively.Precipitation was not an important factor to influence the changes of AGC stock in the urban green space of Xi＇an.Policy orientation,major ecological greening projects such as ＂transplanting big trees into the city＂ and the World Horticultural Exposition were found to have an important impact on changes in the spatiotemporal patterns of AGC stock.
基金funded by the National Natural Science Foundation of China(41801185,32171550)the Natural Science Foundation of Sichuan Province(2023NSFSC0191)+1 种基金the Strategic Priority Research Program(category A)of Chinese Academy of Sciences(XDA20020302)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2021371).
文摘Alpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River.However,due to continuous high-intensity harvesting,a large number of plantings,and the complete harvesting ban measures in recent decades,the forest tree species and age cohorts have become relatively homogenous,and the biodiversity and ecological functions have been reduced.To design effective forest management options to optimize forest structure and increase carbon sequestration capacity,Mao County in Sichuan Province was selected as the study site and six forest management options(harvesting,planting)of different intensities were tested using the LANDIS-II model to simulate and compare the differences in forest aboveground carbon sequestration rate(ACSR)between these options and the current management option over the next 100 years.Our results showed that(i)the different harvesting and planting intensities significantly changed the ACSR compared with the current management options;(ii)different communities responded differently to the management options,with the ACSR differing significantly in cold temperate conifers and temperate conifers but not in broad-leaved trees(P<0.05);and(iii)a comprehensive consideration of forest management options at the species,community and landscape levels was necessary.Our results suggest that implementing a longer harvesting and planting interval(20 years)at the study site can maximize forest ACSR.This study provides an important reference for evaluating the ability of forest management options to restore forest ecological functions and increase carbon sequestration capacity and for selecting effective forest management programs in the eastern Tibetan Plateau.
基金Project funding:Sari University of Agricultural Sciences and Natural Resources
文摘Forests are among the most important carbon sinks on earth. However, their complex structure and vast areas preclude accurate estimation of forest carbon stocks.Data sets from forest monitoring using advanced satellite imagery are now used in international policy agreements.Data sets enable tracking of emissions of COinto the atmosphere caused by deforestation and other types of land-use changes. The aim of this study is to determine the capability of SPOT-HRG Satellite data to estimate aboveground carbon stock in a district of Darabkola research and training forest, Iran. Preprocessing to eliminate or reduce geometric error and atmospheric error were performed on the images. Using cluster sampling, 165 sample plots were taken. Of 165 plots, 81 were in natural habitats, and 84 were in forest plantations. Following the collection of ground data, biomass and carbon stocks were quantified for the sample plots on a per hectare basis. Nonparametric regression models such as support vector regression were used for modeling purposes with different kernels including linear, sigmoid, polynomial, and radial basis function.The results showed that a third-degree polynomial was the best model for the entire studied areas having an root mean square error, bias and accuracy, respectively, of 38.41,5.31, and 62.2; 42.77, 16.58, and 57.3% for the best polynomial for natural forest; and 44.71, 2.31, and 64.3%for afforestation. Overall, these results indicate that SPOTHRG satellite data and support vector machines are useful for estimating aboveground carbon stock.
基金supported in part by research grants from the National Natural Science Foundation of China(Grant Nos.42322103,42171339,and 41830648).
文摘Over the past 4 decades,Southwest China has the fast vegetation growth and aboveground biomass carbon(AGC)accumulation,largely attributed to the active implementation of ecological projects.However,Southwest China has been threatened by frequent extreme drought events recently,potentially countering the expected large AGC increase caused by the ecological projects.Here,we used the L-band vegetation optical depth to quantify the AGC dynamics over Southwest China during the period 2013-2021.Our results showed a net AGC sink of 0.064[0.057,0.077]Pg C year^(−1)(the range represents the maximum and minimum AGC values),suggesting that Southwest China acted as an AGC sink over the study period.Note that the AGC loss of 0.113[0.101,0.136]Pg C year^(−1)was found during 2013-2014,which could mainly be attributed to the negative influence of extreme droughts on AGC changes in Southwest China,particularly in the Yunnan province.For each land use type(i.e.,dense forests,persistent forests,nonforests,afforestation,and forestry),the largest AGC stock increase of 0.032[0.028,0.036]Pg C year^(−1)was found in nonforests,owing to their widespread land cover rate over Southwest China.For AGC density(i.e.,AGC per unit area),the afforestation areas showed the largest AGC density increase of 0.808[0.724,0.985]Mg C ha−1 year^(−1),reflecting the positive effect of afforestation on AGC increase.Moreover,the karst areas exhibited a higher increasing rate of AGC density than nonkarst areas,suggesting that the karst ecosystems have a high carbon sink capacity over Southwest China.
基金supported by the project stocks and potential of carbon sequestration under agroforestry parklands in Niger funded by African Forest Forum(AFF)and International Foundation for Science(IFS),Grant No.D/563-1
文摘This study developed allometric models to estimate aboveground biomass and carbon of Prosopis africana and Faidherbia albida. The destructive method was used with a sample of 20 trees per species for the two parkland sites. Linear regression with log transformation was used to model aboveground biomass according to dendrometric parameters. Error analysis, including mean absolute percentage of error(MAPE) and root mean square of error(RMSE), was used to select and validate the models for both species. Model 1(biomass according to tree diameter) for P. africana and F. albida were considered more representative. The statistical parameters of these models were R2 = 0.99, MAPE 0.98% and RMSE1.75% for P. africana, and R2 = 0.99, MAPE 1.19%,RMSE 2.37% for F. albida. The average rate of carbon sequestered was significantly different for the two species(P ≤ 0.05). The total amount sequestered per tree averaged0.17 × 10-3 Mg for P. africana and 0.25 × 10-3 Mg for F. albida. These results could be used to develop policies that would lead to the sustainable management of these resources in the dry parklands of Niger.
文摘A study was conducted to assess carbon stocks in various forms and land-use types and reliably estimate the impact of land use on C stocks in the Nam Yao sub-watershed （19°05′10″N, 100°37′02″E）, Thailand. The carbon stocks of aboveground, soil organic and fine root within primary forest, reforestation and agricultural land were estimated through field data collection. Results re- vealed that the amount of total carbon stock of forests （357.62 ± 28.51 Mg·ha^-1, simplified expression of Mg （carbon）·ha^-1） was significantly greater （P〈 0.05） than the reforestation （195.25 ± 14.38 Mg·ha^-1） and the agricultural land （103.10 ± 18.24 Mg·ha^-1）. Soil organic carbon in the forests （196.24 ± 22.81 Mg·ha^-1） was also significantly greater （P〈 0.05） than the reforestation （146.83 ± 7.22 Mg·ha^-1） and the agricultural land （95.09± 14.18 Mg·ha^-1）. The differences in carbon stocks across land-use types are the primary consequence of variations in the vegetation biomass and the soil organic matter. Fine root carbon was a small fraction of carbon stocks in all land-use types. Most of the soil organic carbon and fine root carbon content was found in the upper 40-cm layer and decreased with soil depth. The aboveground carbon：soil organic carbon： fine root carbon ratios （ABGC： SOC： FRC）, was 5：8：1, 2：8：1, and 3：50：1 for the forest, reforestation and agricultural land, respectively. These results indicate that a relatively large proportion of the C loss is due to forest conversion to agricultural land. However, the C can be effectively recaptured through reforestation where high levels of C are stored in biomass as carbon sinks, facilitating carbon dioxide mitigation.
文摘Forest ecosystems play a crucial role in mitigating global climate change by forming massive carbon sinks. Their carbon stocks and stock changes need to be quantified for carbon budget balancing and international reporting schemes. However, direct sampling and biomass weighing may not always be possible for quantification studies conducted in large forests. In these cases, indirect methods that use forest inventory information combined with remote sensing data can be beneficial. Synthetic aperture radar (SAR) images offer numerous opportunities to researchers as freely distributed remote sensing data. This study aims to estimate the amount of total carbon stock (TCS) in forested lands of the Kizildag Forest Enterprise. To this end, the actual storage capacities of five carbon pools, i.e. above- and below-ground, deadwood, litter, and soil, were calculated using the indirect method based on ground measurements of 264 forest inventory plots. They were then associated with the backscattered values from Sentinel-1 and ALOS-2 PALSAR-2 data in a Geographical Information System (GIS). Finally, TCS was separately modelled and mapped. The best regression model was developed using the HH polarization of ALOS-2 PALSAR-2 with an adjusted R^(2) of 0.78 (p < 0.05). According to the model, the estimated TCS was about 2 Mt for the entire forest, with an average carbon storage of 133 t ha^(−1). The map showed that the distribution of TCS was heterogenic across the study area. Carbon hotspots were mostly composed of pure stands of Anatolian black pine and mixed, over-mature stands of Lebanese cedar and Taurus fir. It was concluded that the total carbon stocks of forest ecosystems could be estimated using appropriate SAR images at acceptable accuracy levels for forestry purposes. The use of additional ancillary data may provide more delicate and reliable estimations in the future. Given the implications of this study, the spatiotemporal dynamics of carbon can be effectively controlled by forest management when coupled with easily accessible space-borne radar data.
基金We acknowledge grants from the National Key R&D Program of China(Project Number:2020YFE0200800)National Science and Technology Major Project of China's High Resolution Earth Observation System(Project Number:21-Y20B01-9001-19/22-1).
文摘Assessing the changes in forest carbon stocks over time is critical for monitoring carbon dynamics,estimating the balance between carbon uptake and release from forests,and providing key insights into climate change mitigation.In this study,we quantitatively characterized spatiotemporal variations in aboveground carbon density(ACD)in boreal natural forests in the Greater Khingan Mountains(GKM)region using bi-temporal discrete aerial laser scanning(ALS)data acquired in 2012 and 2016.Moreover,we evaluated the transferability of the proposed design model using forest field plot data and produced a wall-to-wall map of ACD changes for the entire study area from 2012 to 2016 at a grid size of 30 m.In addition,we investigated the relationships between carbon dynamics and the dominant tree species,age groups,and topography of undisturbed forested areas to better understand ACD variations by employing heterogeneous forest canopy structural characteristics.The results showed that the performance of the temporally transferable model(R^(2)=0.87,rRMSE=18.25%),which included stable variables,was statistically equivalent to that obtained from the model fitted directly by the 2016 field plots(R^(2)=0.87,rRMSE=17.47%).The average rate of change in carbon sequestration across the entire study region was 1.35 Mg⋅ha^(-1)⋅year^(-1) based on the changes in ALS-based ACD values over the course of four years.The relative change rates of ACD decreased as the elevation increased,with the highest and lowest ACD growth rates occurring in the middle-aged and mature forest stands,respectively.The Gini coefficient,which represents forest canopy surface structure heterogeneity,is sensitive to carbon dynamics and is a reliable predictor of the relative change rate of ACD.This study demonstrated the applicability of bi-temporal ALS for predicting forest carbon dynamics and fine-scale spatial change patterns.Our research contributed to a better understanding of the in-fluence of remote sensing-derived environmental variables on forest carbon dynamic patterns and the development of context-specific management approaches to increase forest carbon stocks.
基金provided by the Canadian Forest Service,with in-kind support from the Ontario Ministry of Natural Resources and Forestry
文摘Canadian boreal mixedwood forests are extensive,with large potential for carbon sequestration and storage;thus,knowledge of their carbon stocks at different stand ages is needed to adapt forest management practices to help meet climate-change mitigation goals.Carbon stocks were quantified at three Ontario boreal mixedwood sites.A harvested stand,a juvenile stand replanted with spruce seedlings and a mature stand had total carbon stocks(±SE)of 133±13 at age 2,130±13 at age 25,and 207±15 Mg C ha^-1 at age 81 years.At the clear-cut site,stocks were reduced by about 40%or 90 Mg C ha^-1 at harvest.Vegetation held 27,34 and 62%of stocks,while detritus held 34,29 and 13%of stocks at age 2,25 and 81,respectively.Mineral soil carbon stocks averaged 51 Mg C ha^-1,and held 38,37 and 25%of stocks.Aboveground net primary productivity(±SE)in the harvested and juvenile stand was 2.1±0.2 and 3.7±0.3 Mg C ha^-1 per annum(p.a.),compared to 2.6±2.5 Mg C ha^-1 p.a.in the mature stand.The mature canopies studied had typical boreal mixedwood composition and mean carbon densities of 208 Mg C ha^-1,which is above average for managed Canadian boreal forest ecosystems.A comparison of published results from Canadian boreal forest ecosystems showed that carbon stocks in mixedwood stands are typically higher than coniferous stands at all ages,which was also true for stocks in vegetation and detritus.Also,aboveground net primary productivity was typically found to be higher in mixedwood than in coniferous boreal forest stands over a range of ages.Measurements from this study,together with those published from the other boreal forest stands demonstrate the potential for enhanced carbon sequestration through modified forest management practices to take advantage of Canadian boreal mixedwood stand characteristics.
文摘Mount Kilimanjaro and the Taita Hills are adjacent montane areas that experience similar climate and agricultural activity, but which differ in their geologic history, nature of elevation gradients and cultures. We assessed differences in cropland above ground carbon (AGC) between the two sites and against environmental variables. One hectare sampling plots were randomly distributed along elevational gradients stratified by cropland type;AGC was derived from all trees with diameter ≥ 10 cm at breast height in each plot. Predictor variables were physical and edaphic variables and human population. A generalized linear model was used for predicting AGC with AIC used for ranking models. AGC was spatially upscaled in 2 km buffer and visually compared. Kilimanjaro has higher AGC in cropped and agroforestry areas than the Taita Hills, but only significant difference in AGC variation in agroforestry areas (F = 9.36, p = 0.03). AGC in cropped land and agroforestry in Kilimanjaro has significant difference on mean (t = 4.62, p = 0.001) and variation (F = 17.41, p = 0.007). In the Taita Hills, significant difference is observed only on the mean AGC (t = 4.86, p = 0.001). Common tree species that contribute the most to AGC in Kilimanjaro are Albizia gummifera and Persea americana, and in the Taita Hills Grevillea robusta and Mangifera indica. Significant and univariate predictors of AGC in Mount Kilimanjaro are pH (R2 = 0.80, p = 0.00) and EVI (R2 = 0.68, p = 0.00). On Mount Kilimanjaro, the top multivariate model contained SOC, CEC, pH and BLD (R2 = 0.90, p = 0.00), whereas in the Taita Hills, the top multivariate model contained elevation, slope and population (R2 = 0.89, p = 0.00). Despite of the difference in land management history of Mount Kilimanjaro and the Taita Hills, mean of AGC in croplands does not differ significantly. Difference occurs on variation of AGC, type of trees contributing AGC, and environmental variables that explain AGC distribution. The research results provide reference for management of carbon sequestration on inhabited montane areas.
文摘The aim of this study was to assess Acacia senegal trees’ characteristics as well as evaluate the carbon stock under a variety of ages in the El Demokeya forest in Sudan, where the Gum Arabic belt is located. 12 sample plots, in 2021 were randomly distributed to represent the entire area of the forest prior to the required measurements. The sample was designed as squire plots with one hectare. In each sample plot, all trees were counted, their height (m), and Diameters Breast Height (DBH in cm), respectively. The results showed the highest number of trees per ha at age 20 years old and the lowest number at age 47 years, while the highest values of DBH and volume were found at age 47 years old. As a result, the maximum and minimum values of the aboveground biomass were found in the age 47 years old and 16 years, accounting for 19.87 tons and 1.9 tons respectively. Thus, the amount of carbon stock was 11.92 tons/ha in the 35-years-old and 1.19 tons/ha in the 21-year stands. Furthermore, the average carbon stock in all plots was estimated as 18.70 tons/ha and hence the total carbon stock in the El Demokeya forest is equal to 620.11 tons. Conclusively, the characteristics of trees, amount of aboveground biomass and carbon stock in the El Demokeya forest varied among the uneven-aged plantation groups. The study recommends and encourages the protection of A. senegal in order to increase the carbon sink as well as protect the environment in the era of climatic changes.
