Changes In Carbon Density Research Articles

Determinants of carbon sequestration in thinned forests

Given global climate change and the projected increases in the greenhouse effect, enhancing the carbon storage capacity of forest ecosystems is especially critical. To fully realize the potential carbon sequestration, it is imperative to understand the drivers affecting carbon storage in forest ecosystems, particularly with disturbances that disrupt existing balance. In this study, we explored the effects of stem-only harvest at various thinning intensities on forest structure and carbon density in middle-aged natural secondary forests, located in the northern temperate zone. Carbon density included aboveground carbon density (ACD), soil organic carbon stocks (SOCD), and total carbon density (TCD), which was the sum of ACD and SOCD. We employed the random forest analysis method to identify significant variables influencing changes in carbon density. Structural equation modelling (SEM) was then used to determine the drivers of changes in forest carbon density. The results showed that moderate thinning (20 %–35 % trees removed), is an effective management practice for increasing the TCD in forests. Although heavy thinning (35.1 %–59.9 % trees removed) accelerated individual growth, it did not fully offset the carbon removed due to thinning. It is noteworthy that light thinning (0–19.9 % trees removed) not only reduced the species richness but also caused a significant number of tree deaths. Large live trees were an important direct determining factor of ACD, but not the only one. In addition, thinning indirectly influenced ACD by reducing canopy density and deformed tree density. The increase in dead tree density had an adverse impact on SOCD, and this phenomenon increased with the passage of recovery time. Conversely, greater thinning intensity enhanced SOCD. Moreover, TCD was directly influenced by tree height, large live trees, and stand density. Furthermore, thinning altered the conifer ratio, thereby influencing tree growth and indirectly controlling the TCD. We believe that this knowledge will be highly beneficial for successful forest management and enhancing the carbon sequestration capacity of forest ecosystems.

Methodology for evaluating soil carbon stock changes based on regional geochemical survey data: A case study in Huangpi, China

Soil carbon pools play a crucial role in the Earth's ecosystem, acting as significant carbon sinks and sources. Through a detailed analysis of soil carbon content using data from the Huangpi District in Wuhan, China, this research employs geochemical survey data, field replicates, and spatial autocorrelation information to establish an assessment model for soil carbon stocks. The model addresses the sources of errors and their effects on carbon pool changes, using both traditional statistical theories and geostatistical models to detect changes in carbon density and estimate carbon sources and sinks with minimized error ranges. Key findings indicate that sampling errors, influenced by small-scale spatial variability, are the primary source of observational inaccuracies in assessing total soil carbon and organic carbon, accounting for over 90% of the variation. Meanwhile, analytical errors are more significant when quantifying soil inorganic carbon content due to its lower concentrations. From 2001 to 2022, no significant changes were observed in the soil organic carbon stock in Huangpi District, while a modest increase in inorganic carbon was noted. The study highlights that increasing sample density beyond a certain threshold does not significantly affect carbon stock estimates or their error ranges, emphasizing the stability of the block kriging method in estimating regional carbon stocks.

Analysis of Linkage between Long-Term Morphological Spatial Pattern Analysis and Vegetation Carbon Storage of Forests in Hunan, China

The carbon sequestration of forest ecosystems plays a pivotal role in constraining global warming and mitigating climate change. The landscape pattern of forests is being altered due to the combined effects of climate change and human interference. Furthermore, the relationship between forest pattern changes and carbon storage distribution in a long time series remains unclear. Therefore, it is necessary to examine the relationship between forest patterns and carbon density, investigating the variations and similarities in the changes in carbon density across different modes of pattern change over time, and suggestions for forest planning were provided from a perspective focused on pattern change to enhance carbon storage. The Google Earth Engine (GEE) platform’s random forest model was used to map the spatial distribution of forests in Hunan Province for 1996 and 2020, followed by analyzing the correlation between the changes in forest patterns using the morphological spatial pattern analysis (MSPA) and carbon density simulated by the model. Results show that the net growth rate ((area in 2020-area in 1996)/area in 2020) of the forest in Hunan increased 26.76% between 1996 and 2020. The importance scores for the decade average temperature, short-wave length infrared band 1 (SWIR-1), and slope were the highest metrics in the model of carbon density, and were 0.127, 0.107 and 0.089, respectively. The vegetation carbon storage in Hunan Province increased by 31.02 Tg, from 545.91 Tg to 576.93 Tg in 25 years. This study demonstrates that vegetation carbon storage is influenced by the pattern type in both newly established and pre-existing forests (p < 0.05). The findings of this study offer empirical evidence to support forest management strategies targeted at enhancing carbon sequestration.

Scale-dependent and driving relationships between spatial features and carbon storage and sequestration in an urban park of Zhengzhou, China

Research indicates that urban ecosystems can store large amounts of carbon. However, few studies have examined how the spatial features of park greenspace affect its carbon-carrying capacity, and how those effects vary with the spatial scale. Lidar point clouds and remote sensing images were extracted for the 196 ha green space in the China Green Expo to study carbon storage and sequestration in parks. Full subset regression, stepwise regression, HP analysis, and structural equation modeling were used to examine the scale dependency and the driving relationship between carbon storage and carbon sequestration in parks. The results show that the optimal statistical sample diameters for carbon density and carbon sequestration density in parks are 100 m. Under the influence of impermeable surfaces and water bodies, the statistical values of carbon density were minimized when the sample plot diameter was 700 m. Biodiversity and forest structure are the main drivers of carbon density, with the influence of water bodies being more prominent on a larger scale. Texture characteristics explain more carbon density than the vegetation index, and RVI could better explain the variation of carbon sequestration than NDVI. This study explores scaled changes in carbon density, carbon sequestration density in parks, and their driving relationships, which can aid in developing carbon sequestration strategies based on parks.

Inconsistent Carbon Budget Estimation Using Dynamic/Static Carbon Density under Land Use and Land Cover Change: A Case Study in Henan Province, China

The scientific estimation of carbon budgets induced by land use and land cover change (LUCC) can improve the accuracy of carbon budget estimates for terrestrial ecosystems and deepen our understanding of the future carbon sink potential of these ecosystems. Previous studies have typically selected one of many LUCC-induced carbon budget methods and overlooked the differences in the results between the different methods. Taking Henan Province, China, as a case study, we used the IPCC method, the bookkeeping model, and the inventory method to estimate LUCC-induced carbon budgets and compared the differences in these methods. The results showed that LUCC in Henan Province was categorized as a carbon sink from 1980 to 2015 based on the IPCC method and the inventory method. However, the estimates were significantly different, and the total estimates of the IPCC method were 40% less than those of the inventory method. At the regional ecogeographical scale, the two methods were not consistent in assessing the carbon source/sink of LUCC. The bookkeeping model categorized LUCC as a carbon source in Henan Province for the same period, and the carbon storage change trend opposed those of the other two methods. The failure of the IPCC method and the bookkeeping model to include the dynamic changes in carbon density caused by climate and land use management led to the great differences between the three methods. The inventory method is recommended to estimate the carbon budget caused by LUCC for regions where carbon density varies greatly over time. Both the IPCC method and the bookkeeping model may have great uncertainty in estimating changes in LUCC-induced carbon stocks and should be used with caution.

Simulated Soil Organic Carbon Density Changes from 1980 to 2016 in Shandong Province Dry Farmlands Using the CENTURY Model

The changes in cultivated soil organic carbon (SOC) have significant effects on soil fertility and atmospheric carbon dioxide (CO2) concentration. Shandong Province is an important agricultural and grain production area in China. Dry farmland accounts for 74.15% of the province’s area, so studies on dynamic SOC changes would be helpful to understand its contribution to the Chinese national carbon (C) inventory. Using the spatial overlay analysis of the soil layer (1:10,000,000) and the land use layer (1:10,000,000), 2329 dry farmland soil polygons were obtained to drive the CENTURY model to simulate SOC dynamics in Shandong Province from the period 1980 to 2016. The results showed that the CENTURY model can be used to simulate the dry farmland SOC in Shandong Province. From the period 1980 to 2016, the soil organic carbon storage (SOCS) and soil organic carbon density (SOCD) showed an initial increase and then decreased, especially after reaching a maximum in 2009. In 2016, the SOCS was 290.58 × 106 t, an increase of 26.99 × 106 t compared with 1980. SOCD in the dry farmland increased from 23.69 t C ha−1 in 1980 to 25.94 t C ha−1 in 2016. The dry farmland of Shandong Province was a C sink from 1980 to 2016. Among the four soil orders, inceptisols SOCD dominated, and accounted for 47.81% of the dry farmland, followed by >entisols > vertisols > alfisols. Entisols SOCD growth rate was the highest (0.23 t C ha−1year−1). Compared to 1980, SOCD in 2016 showed an increasing trend in the northeast, northwest and southeast regions, while it followed a downward trend in the southwest.

Evolution characteristics of soil carbon density after homestead remediation

In order to gain an in-depth understanding of the effects of different reclamation years on soil carbon sequestration after remediation of abandoned homesteads, this study relied on the land improvement project carried out in Changchun County, Shaanxi Province, to study the soil carbon density of different reclamation years. The results shown that the total carbon and inorganic carbon content of 0-20cm and 40-60cm soil layers increased steadily with the extension of cultivation time after the rectification of abandoned homesteads. In the 20-40 cm soil layer, the soil total carbon and inorganic carbon content increased firstly, then decreased and then increased with the extension of the cultivation period, especially the total carbon content changed the most. In the 0-40 cm soil layer, the organic carbon showed a tendency to decrease first, and the change trend of the organic carbon content in the 40-60 cm soil layer increased first and then decreased. The trend of carbon density changes was consistent with the trend of carbon content. After 10 years of reclamation compared with before the renovation, soil total carbon and inorganic carbon density increased by 22.93% to 47.72% and 16.11% to 45.30%, respectively, the regularities of vertical distribution was 40-60 cm > 0-20 cm > 20-40 cm. The density of organic carbon increased by 41.12% to 68.27% compared with before the renovation, and the regularities of vertical distribution was 0-20cm>20-40cm>40-60cm. It shows that long-term reclamation after homestead remediation is beneficial to the increase and fixation of surface soil organic carbon.

Potential shift from a carbon sink to a source in Amazonian peatlands under a changing climate

Amazonian peatlands store a large amount of soil organic carbon (SOC), and its fate under a future changing climate is unknown. Here, we use a process-based peatland biogeochemistry model to quantify the carbon accumulation for peatland and nonpeatland ecosystems in the Pastaza-Marañon foreland basin (PMFB) in the Peruvian Amazon from 12,000 y before present to AD 2100. Model simulations indicate that warming accelerates peat SOC loss, while increasing precipitation accelerates peat SOC accumulation at millennial time scales. The uncertain parameters and spatial variation of climate are significant sources of uncertainty to modeled peat carbon accumulation. Under warmer and presumably wetter conditions over the 21st century, SOC accumulation rate in the PMFB slows down to 7.9 (4.3-12.2) g⋅C⋅m-2⋅y-1 from the current rate of 16.1 (9.1-23.7) g⋅C⋅m-2⋅y-1, and the region may turn into a carbon source to the atmosphere at -53.3 (-66.8 to -41.2) g⋅C⋅m-2⋅y-1 (negative indicates source), depending on the level of warming. Peatland ecosystems show a higher vulnerability than nonpeatland ecosystems, as indicated by the ratio of their soil carbon density changes (ranging from 3.9 to 5.8). This is primarily due to larger peatlands carbon stocks and more dramatic responses of their aerobic and anaerobic decompositions in comparison with nonpeatland ecosystems under future climate conditions. Peatland and nonpeatland soils in the PMFB may lose up to 0.4 (0.32-0.52) Pg⋅C by AD 2100 with the largest loss from palm swamp. The carbon-dense Amazonian peatland may switch from a current carbon sink into a source in the 21st century.

Drivers Analysis of CO₂ Emissions from the Perspective of Carbon Density: The Case of Shandong Province, China.

Against the backgrounds of emission reduction targets promised by China, it is crucial to explore drivers of CO2 emissions comprehensively for policy making. In this study, Shandong Province in China is taken as an example to investigate drivers in carbon density by using an extended Kaya identity and a logarithmic mean Divisia index model (LMDI) with two layers. It is concluded that there are eight positive driving factors of carbon density during 2000–2015, including traffic congestion, land urbanization, etc., and seven negative driving factors comprising energy intensity, economic structure, etc. Among these factors, economic growth and energy intensity are the main positive and negative driving factor, respectively. The contribution rate of traffic congestion and land urbanization is gradually increasing. Meanwhile, 15 driving factors are divided into five categories. Economic effect and urbanization effect are the primary positive drivers. Contrarily, energy intensity effect, structural effect, and scale effect contribute negative effects to the changes in carbon density. In the four stages, the contribution of urbanization to carbon density is inverted U. Overall, the results and suggestions can give support to decision maker to draw up relevant government policy.

Assessment of Carbon Storage and Its Influencing Factors in Qinghai-Tibet Plateau

Land use/cover change (LUCC) is one of the major factors influencing the storage of ecosystem carbon. The carbon storage in Qinghai-Tibet Plateau, the world’s highest plateau, is affected by a combination of many factors. Using MCD12Q1 land classification data, aboveground biomass, belowground biomass, soil carbon and humus carbon data, as well as field sampling data for parameters verification, we applied the InVEST model to simulate the ecosystem carbon storage and the impacts of driving factors. The field survey samples were used to test the regression accuracy, and the results confirmed that the model performance was reasonable and acceptable. The main conclusions of this study are as follows: From 2001 to 2010, carbon storage in the Qinghai-Tibet Plateau increased by 10.39 billion t when assuming that the carbon density in each land cover type was constant. Changes of the land cover types caused carbon storage to increase by 116 million t, which contributed 13.82% of the dynamic carbon storage. Consequently, changes in carbon density accounted for 86.18% of the carbon storage change. In addition, we investigated the soil organic matter and aboveground biomass characteristics between 2012 and 2014 and found that the influences of fencing and dung on carbon storage were positive.

Global and regional fluxes of carbon from land use and land cover change 1850–2015

AbstractThe net flux of carbon from land use and land cover change (LULCC) is an important term in the global carbon balance. Here we report a new estimate of annual fluxes from 1850 to 2015, updating earlier analyses with new estimates of both historical and current rates of LULCC and including emissions from draining and burning of peatlands in Southeast Asia. For most of the 186 countries included we relied on data from Food and Agriculture Organization to document changes in the areas of croplands and pastures since 1960 and changes in the areas of forests and “other land” since 1990. For earlier years we used other sources of information. We used a bookkeeping model that prescribed changes in carbon density of vegetation and soils for 20 types of ecosystems and five land uses. The total net flux attributable to LULCC over the period 1850–2015 is calculated to have been 145 ± 16 Pg C (1 standard deviation). Most of the emissions were from the tropics (102 ± 5.8 Pg C), generally increasing over time to a maximum of 2.10 Pg C yr−1 in 1997. Outside the tropics emissions were roughly constant at 0.5 Pg C yr−1 until 1940, declined to zero around 1970, and then became negative. For the most recent decade (2006–2015) global net emissions from LULCC averaged 1.11 (±0.35) Pg C yr−1, consisting of a net source from the tropics (1.41 ± 0.17 Pg C yr−1), a net sink in northern midlatitudes (−0.28 ± 0.21 Pg C yr−1), and carbon neutrality in southern midlatitudes.

Forest biomass carbon storage from multiple inventories over the past 30 years in Gansu Province, China: implications from the age structure of major forest types

We used the forest inventory data of Gansu Province, China to quantify carbon storage and carbon density changes by regional forest cover and by typical forest types in 1979–2006. Total forest area increased from 1.77 × 106 ha in 1979 to 2.32 × 106 ha in 2006, and the forest carbon storage, estimated by the continuous biomass expansion factor method, increased from 83.14 to 100.66 Tg, equivalent to a carbon accumulation rate of 0.0071 Tg per year during the period. Mean carbon densities were 44.83–48.50 t ha−1 and the values decreased slightly over the time period. Natural forests generated greater carbon storage and density than did plantations. By regression analysis, forest stand age was an important parameter in carbon density studies. We developed various regression equations between carbon density and stand age for major types of natural forests and plantations in the region. Our results can be used for proper selection of re-forestation species and efficient management of young and middle-aged forests, offering great potential for future carbon sequestration, especially in arid and semi-arid regions.

Decay patterns and carbon density of standing dead trees in California mixed conifer forests

Dead wood plays important structural and biogeochemical roles in forest ecosystem processes. Some aspects of woody debris dynamics have been carefully studied, but the decay patterns and carbon density of standing dead (SD) trees are only weakly characterized. Climbing forest mortality rates are also driving increases in the creation and abundance of SD trees. All forms of forest carbon accounting, from stand-level biomass calculations to dynamic earth systems models, are improved by a better understanding of SD tree physical and chemical traits. Using dimensional analysis, we described the patterns of density, carbon concentration, and net carbon density in decaying SD trees of six California mixed conifer species. As decay class advanced, trees showed a progressively lower density and a small increase in carbon concentration. Net carbon density of the most decayed SD trees was only 60% that of live trees. The key characteristics of SD trees that determine these patterns are species, surface to volume ratio, and relative position within the tree. The decay of SD trees and how deadwood biomass is estimated in large scale inventories also have repercussions in greenhouse gas accounting. When the measured changes in carbon density are applied to SD carbon stock estimates for California mixed conifer forests, the decay-adjusted estimates are 3.66–3.74Tg (18%) lower than estimates that do not incorporate change due to decay.

Changes in carbon density for three old-growth forests on Changbai Mountain, Northeast China: 1981–2010

Introduction The old-growth forests on Changbai Mountain have been well protected from human activities and provide a living laboratory for studying forest carbon sequestration under natural environmental conditions.

A spatial resolution threshold of land cover in estimating terrestrial carbon sequestration in four counties in Georgia and Alabama, USA

Abstract. Changes in carbon density (i.e., carbon stock per unit area) and land cover greatly affect carbon sequestration. Previous studies have shown that land cover change detection strongly depends on spatial scale. However, the influence of the spatial resolution of land cover change information on the estimated terrestrial carbon sequestration is not known. Here, we quantified and evaluated the impact of land cover change databases at various spatial resolutions (250 m, 500 m, 1 km, 2 km, and 4 km) on the magnitude and spatial patterns of regional carbon sequestration in four counties in Georgia and Alabama using the General Ensemble biogeochemical Modeling System (GEMS). Results indicated a threshold of 1 km in the land cover change databases and in the estimated regional terrestrial carbon sequestration. Beyond this threshold, significant biases occurred in the estimation of terrestrial carbon sequestration, its interannual variability, and spatial patterns. In addition, the overriding impact of interannual climate variability on the temporal change of regional carbon sequestration was unrealistically overshadowed by the impact of land cover change beyond the threshold. The implications of these findings directly challenge current continental- to global-scale carbon modeling efforts relying on information at coarse spatial resolution without incorporating fine-scale land cover dynamics.

The influence of climate, hydrology and permafrost on Holocene peat accumulation at 3500 m on the eastern Qinghai–Tibetan Plateau

Peatland of the eastern Qinghai–Tibetan Plateau lies at the convergence of the East Asian and Indian monsoon systems in eastern Asia. To understand the evolution of this peatland and its potential to provide new insights into the Holocene evolution of the East Asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near Hongyuan. The age-depth profile was determined using 16 14C-AMS age dates, the peat analysed for a range of environmental variables including carbon, nitrogen and hydrogen concentration, bulk density, δ 13C and the associated spring water analysed for hydrogen and oxygen isotopes. The age-depth profile of the recovered peat sequence covers the period from 9.6 to 0.3 kyr BP and is linear indicating that the conditions governing productivity and decay varied little over the Holocene. Using changes in carbon density, organic carbon content and its δ 13C, cold dry periods of permafrost characterised by low density and impeded surface drainage were identified. The low δ 18O and δD values of the spring water emanating around the peat deposit, down to −13.8 and −102‰ (VSMOW), respectively, with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day. In view of the current annual mean air temperature of 1 °C this suggests conditions in the past have been conducive to permafrost. Inferred periods of permafrost correspond to independently recognised cold periods in other Holocene records from across China at 8.6, 8.2–7.8, 5.6–4.2, 3.1 and 1.8–1.5 kyr BP. The transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at Hongyuan are of longer duration than equivalent cold dry periods over central and eastern China. Light–dark banding peat on a scale of 15–30 years from 9.6 to 5.5 kyr BP may indicate a strong influence of decadal oscillations possibly the Pacific Decadal Oscillation and a potential link between near simultaneous climatic changes in the northwest Pacific, ENSO, movement of the Intertropical Convergence Zone and the East Asian Monsoon.

The Potential Response of Terrestrial Carbon Storage to Changes in Climate and Atmospheric CO 2

We use a georeferenced model of ecosystem carbon dynamics to explore the sensitivity of global terrestrial carbon storage to changes in atmospheric CO2 and climate. We model changes in ecosystem carbon density, but we do not model shifts in vegetation type. A model of annual NPP is coupled with a model of carbon allocation in vegetation and a model of decomposition and soil carbon dynamics. NPP is a function of climate and atmospheric CO2 concentration. The CO2 response is derived from a biochemical model of photosynthesis. With no change in climate, a doubling of atmospheric CO2 from 280 ppm to 560 ppm enhances equilibrium global NPP by 16.9%; equilibrium global terrestrial ecosystem carbon (TEC) increases by 14.9%. Simulations with no change in atmospheric CO2 concentration but changes in climate from five atmospheric general circulation models yield increases in global NPP of 10.0–14.8%. The changes in NPP are very nearly balanced by changes in decomposition, and the resulting changes in TEC range from an increase of 1.1% to a decrease of 1.1%. These results are similar to those from analyses using bioclimatic biome models that simulate shifts in ecosystem distribution but do not model changes in carbon density within vegetation types. With changes in both climate and a doubling of atmospheric CO2, our model generates increases in NPP of 30.2–36.5%. The increases in NPP and litter inputs to the soil more than compensate for any climate stimulation of decomposition and lead to increases in global TEC of 15.4–18.2%.