Soil carbon pools of six ecological regions of the United States

Mineralisable soil organic carbon(SOC)pools vary with ecosystem type in response to changes in climate,vegetation and soil properties.Understanding the effect of climate and soil factors on SOC pools is critical for predicting change over time.Surface soil samples from six ecoregions of the United States were analyzed for permanganate oxidizable C(KMnO4-C)and mineralizable C pools.Variations of SOC ranged from 7.9 mg g^-1(Florida site)to 325 mg g^-1(Hawaii site).Mineralisable C pools and KMnO4-C were highest in soils from the Hawaii site.Mean annual precipitation explains SOC and resistant C pool variations.Clay content was related to mineralisable active C pools and bacterial abundance.Mean annual precipitation and clay content are potential variables for predicting changes in SOC pools at large spatial scales.

The below-ground biomass contributes more to wetland soil carbon pools than the above-ground biomass-a survey based on global wetlands

The biomass of wetland plants is highly responsive to environmental factors and plays a crucial role in the dynamics of the soil organic carbon(SOC)pool.In this study,we collected and analyzed global data on wetland plant biomass from 1980 to 2021.By examining 1134 observations from 182 published papers on wetland ecosystems,we created a comprehensive database of wetland plant above-ground biomass(AGB)and below-ground biomass(BGB).Using this database,we analyzed the biomass characteristics of different climate zones,wetland types and plant species globally.Based on this,we analyzed the differences between the biomass of different plant species and the linkage between AGB and BGB and organic carbon.Our study has revealed that wetland plant AGB is greater in equatorial regions but BGB is highest in polar areas,and lowest in arid and equatorial zones.For plant species,the BGB of the Poales is higher than the AGB but Caryophyllales,Cyperales and Lamiales have higher AGB.Moreover,our findings indicate that BGB plays a more significant role in contributing to the organic carbon pool compared to AGB.Notably,when BGB is less than 1 t C ha^(-1),even slight changes in biomass can have a significant impact on the organic carbon pool.And we observed that the SOC increases by 5.7 t C ha^(-1)when the BGB content is low,indicating that the SOC is more sensitive to changes in biomass under such circumstances.Our study provides a basis for the global response of AGB and BGB of wetland plants to organic carbon.

Carbon pools and fluxes in the China Seas and adjacent oceans

The China Seas include the South China Sea, East China Sea, Yellow Sea, and Bohai Sea. Located off the Northwestern Pacific margin, covering 4700000 km^2 from tropical to northern temperate zones, and including a variety of continental margins/basins and depths, the China Seas provide typical cases for carbon budget studies. The South China Sea being a deep basin and part of the Western Pacific Warm Pool is characterized by oceanic features; the East China Sea with a wide continental shelf, enormous terrestrial discharges and open margins to the West Pacific, is featured by strong cross-shelf materials transport; the Yellow Sea is featured by the confluence of cold and warm waters; and the Bohai Sea is a shallow semiclosed gulf with strong impacts of human activities. Three large rivers, the Yangtze River, Yellow River, and Pearl River, flow into the East China Sea, the Bohai Sea, and the South China Sea, respectively. The Kuroshio Current at the outer margin of the Chinese continental shelf is one of the two major western boundary currents of the world oceans and its strength and position directly affect the regional climate of China. These characteristics make the China Seas a typical case of marginal seas to study carbon storage and fluxes. This paper systematically analyzes the literature data on the carbon pools and fluxes of the Bohai Sea,Yellow Sea, East China Sea, and South China Sea, including different interfaces(land-sea, sea-air, sediment-water, and marginal sea-open ocean) and different ecosystems(mangroves, wetland, seagrass beds, macroalgae mariculture, coral reefs, euphotic zones, and water column). Among the four seas, the Bohai Sea and South China Sea are acting as CO_2 sources, releasing about0.22 and 13.86–33.60 Tg C yr^(-1) into the atmosphere, respectively, whereas the Yellow Sea and East China Sea are acting as carbon sinks, absorbing about 1.15 and 6.92–23.30 Tg C yr^(-1) of atmospheric CO_2, respectively. Overall, if only the CO_2 exchange at the sea-air interface is considered, the Chinese marginal seas appear to be a source of atmospheric CO_2, with a net release of 6.01–9.33 Tg C yr^(-1), mainly from the inputs of rivers and adjacent oceans. The riverine dissolved inorganic carbon (DIC) input into the Bohai Sea and Yellow Sea, East China Sea, and South China Sea are 5.04, 14.60, and 40.14 Tg C yr^(-1),respectively. The DIC input from adjacent oceans is as high as 144.81 Tg C yr^(-1), significantly exceeding the carbon released from the seas to the atmosphere. In terms of output, the depositional fluxes of organic carbon in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea are 2.00, 3.60, 7.40, and 5.92 Tg C yr^(-1), respectively. The fluxes of organic carbon from the East China Sea and South China Sea to the adjacent oceans are 15.25–36.70 and 43.93 Tg C yr^(-1), respectively. The annual carbon storage of mangroves, wetlands, and seagrass in Chinese coastal waters is 0.36–1.75 Tg C yr^(-1), with a dissolved organic carbon(DOC) output from seagrass beds of up to 0.59 Tg C yr^(-1). Removable organic carbon flux by Chinese macroalgae mariculture account for 0.68 Tg C yr^(-1) and the associated POC depositional and DOC releasing fluxes are 0.14 and 0.82 Tg C yr^(-1), respectively. Thus, in total, the annual output of organic carbon, which is mainly DOC, in the China Seas is 81.72–104.56 Tg C yr^(-1). The DOC efflux from the East China Sea to the adjacent oceans is 15.00–35.00 Tg C yr^(-1). The DOC efflux from the South China Sea is 31.39 Tg C yr^(-1). Although the marginal China Seas seem to be a source of atmospheric CO_2 based on the CO_2 flux at the sea-air interface, the combined effects of the riverine input in the area, oceanic input, depositional export,and microbial carbon pump(DOC conversion and output) indicate that the China Seas represent an important carbon storage area.

Assessment of above- and belowground carbon pools in a semi-arid forest ecosystem of Delhi, India

Background:Assessment of carbon pools in semi-arid forests of India is crucial in order to develop a better action plan for management of such ecosystems under global climate change and rapid urbanization.This study,therefore,aims to assess the above-and belowground carbon storage potential of a semi-arid forest ecosystem of Delhi.Methods:For the study,two forest sites were selected,i.e.,north ridge(NRF)and central ridge(CRF).Aboveground tree biomass was estimated by using growing stock volume equations developed by Forest Survey of India and specific wood density.Understory biomass was determined by harvest sampling method.Belowground(root)biomass was determined by using a developed equation.For soil organic carbon(SOC),soil samples were collected at 0–10-cm and 10–20-cm depth and carbon content was estimated.Results:The present study estimated 90.51 Mg ha−1 biomass and 63.49 Mg C ha−1 carbon in the semi-arid forest of Delhi,India.The lower diameter classes showed highest tree density,i.e.,240 and 328 individuals ha−1(11–20 cm),basal area,i.e.,8.7(31–40 cm)and 6.08m2 ha−1(11–20 cm),and biomass,i.e.,24.25 and 23.57 Mg ha−1(11–20 cm)in NRF and CRF,respectively.Furthermore,a significant contribution of biomass(7.8 Mg ha−1)in DBH class 81–90 cm in NRF suggested the importance of mature trees in biomass and carbon storage.The forests were predominantly occupied by Prosopis juliflora(Sw.)DC which also showed the highest contribution to the(approximately 40%)tree biomass.Carbon allocation was maximum in aboveground(40–49%),followed by soil(29.93–37.7%),belowground or root(20–22%),and litter(0.27–0.59%).Conclusion:Our study suggested plant biomass and soils are the potential pools of carbon storage in these forests.Furthermore,carbon storage in tree biomass was found to be mainly influenced by tree density,basal area,and species diversity.Trees belonging to lower DBH classes are the major carbon sinks in these forests.In the study,native trees contributed to the significant amount of carbon stored in their biomass and soils.The estimated data is important in framing forest management plans and strategies aimed at enhancing carbon sequestration potential of semi-arid forest ecosystems of India.

Forest and Soil Carbon Stocks, Pools and Dynamics and Potential Climate Change Mitigation in Nepal

The degradation of forest and soil contribute significantly to carbon emission to the atmosphere leading to the build-up of carbon dioxide in atmosphere and contributing to global warming. Consequences of climate change are not only the rise in global temperatures, but also changes in the precipitation patterns, which could affect agricultural production, food security, human health and long-term ecosystem properties balance. The deforestation and land degradation are major sources of GHG （greenhouse gas） emissions. International negotiations and dialogues on REDD＋ mechanism are held for both national and local level mitigation policies formulation for the reduction of carbon emission from land use, land use change and forestry sector. The reduction of emissions from fossil fuel combustion and avoidance of deforestation and forest/land degradation constitute lasting and long-term solutions for mitigating climate change. There is an urgent need of relevant and efficient methods of measuring forest and soil carbon through application of the latest geospatial technologies, i.e., GIS （geographic information system）, Remote Sensing and LiDAR （Light Detection and Ranging）. These technologies can support the precise measurement of carbon stocks, as well as, offer cost effective and interoperable data generation methods. The REDD＋ mechanism is being promoted worldwide mainly to reduce the diminishing of forest in developing countries. Such an approach must consider use rights, sustainable management of forests, ensuring and safe-guarding the benefit sharing mechanism and good governance, along with the legal framework and local livelihood concerns.

Predicting dynamics of soil organic carbon mineralization with a double exponential model in different forest belts of China

The dynamics of soil organic carbon （SOC） was analyzed by using laboratory incubation and double exponential model that mineralizable SOC was separated into active carbon pools and slow carbon pools in forest soils derived from Changbai and Qilian Mountain areas. By analyzing and fitting the CO2 evolved rates with SOC mineralization, the results showed that active carbon pools accounted tor 1.0% to 8.5% of SOC with an average of mean resistant times （MRTs） for 24 days, and slow carbon pools accounted for 91% to 99% of SOC with an average of MRTs for 179 years. The sizes and MRTs of slow carbon pools showed that SOC in Qilian Mountain sites was more difficult to decompose than that in Changbai Mountain sites. By analyzing the effects of temperature, soil clay content and elevation on SOC mineralization, results indicated that mineralization of SOC was directly related to temperature and that content of accumulated SOC and size of slow carbon pools from Changbai Mountain and Qilian Mountain sites increased linearly with increasing clay content, respectively, which showed temperature and clay content could make greater effect on mineralization of SOC.

Soil Carbon Pool Management Index under Different Straw Retention Regimes

[Objective] To clarify the effects of different straw retention regimes on soil fertility in double cropping paddy field. [Method] The effects of different straw reten- tion regimes on total organic carbon （CToc）, active carbon （CA） and mineralized carbon （CM） were analyzed, and carbon pool active （A）, carbon pool active index （A/）, carbon pool index （CPI） and carbon pool management index （CPMi） for each treat- ment were calculated. [Result] Compared with the unfertilized treatment （CK）, CToc, CA, CM and the available ratio of soil carbon were increased in the treatment of re- turning early season and late season rice straws to field. With the same nutrient application, CToc, CA and the available ratio of soil carbon in the field with straw re- turned to field were higher than that of straw incineration and no straw returning, and the change in soil CA content was more significant. The difference in CPMI be- tween different treatments reached significant or very significant level, and the value was in the order of straw directly returned to field 〉 straw returned to field after in- cineration 〉 no straw returned to field. [Conclusion] This study provided theoretical bases for the increase of soil CA content and soil fertility in double rice fields.

Carbon pool structure and carbon density of soil in Pinus koraiensis plantation ecosystem

The organic carbon contents,carbon density and carbon storage of the soil in the Pinus koraiensis plantation ecosystem were investigated in Maoershan experimental forest farm,Shangzhi County,Heilongjiang,on the west slope of the Zhangguangcai Mountains in northeastern China for providing data to evaluation of the carbon balance in forest ecosystem of northeastern China.These soil carbon indicators were measured in three forest types,pure P.koraiensis plantation,P.koraiensis and Betula platyphylla mixed forest,and the P.koraiensis and Quercus mongolica mixed forest.The soil carbon pool consisted of four compartments,namely L layer,F layer,H layer and B layer.With variance analysis,we found that both organic carbon content and carbon density of the soil were significantly affected by forest types,soil compartments and slope positions.The highest soil carbon density（278.63 Mg·ha^-1）.was observed in the mixed forest of P.koraiensis and Q.mongolica.The B layer had the highest carbon density（212.28 Mg·ha^-1） among all the soil compartments.In terms of slope position,the highest soil carbon density（394.18 Mg·ha^-1） presented in the low slope.Besides,soil carbon content and carbon density had a marked change with the organic matter content and vertical depth of the soil in each compartment.The results of this study implied that in the temperate humid region,the mixed ecosystem of regional Pinus koraiensis plantations and natural forest had relatively high carbon storage capability.

Estimation of above-ground biomass and carbon stock of an invasive woody shrub in the subtropical deciduous forests of Doon Valley,western Himalaya,India

This study describes the different parameters used to derive the allometric equation for calculating the biomass of an invasive woody shrub Lantana camara L.from the subtropical conditions of western Himalaya.It identifies the most accurate and convenient method for biomass calculation by comparing destructive with nondestructive methodology.Different parameters were measured on a wide range of Lantana from different community levels for the non-destructive calculation of total aboveground biomass.Different explanatory variables were identified and measured such as basal diameter either as a single independent variable or in combination with plant height.The other suitable combinations of available independent variables include crown length,crown width,crown area,crown volume and coverage of the plant.Amongst the wide range of allometric equations used with different variables,the equation with D2 H as a variable was found to be the most suitable estimator of biomass calculation for Lantana.Sahastradhara,being the most disturbed area due to its high tourist activity round the year,showed maximum coverage（58.57 % ha-1）,highest biomass（13,559.60 kg ha-1） and carbon density（6,373.01 kg ha-1）of Lantana.The degree of Lantana’s invasiveness in subtropical conditions was also calculated on the basis of importance value index（IVI）.The maximum IVI（22.77）and mean coverage（26.8 % ha-1） was obtained from the areas near Jolly Grant airport,indicating that physically disturbed areas are more suitable for the growth of Lantana,which may significantly increase shrub biomass.The importance of incorporating allometric equations in calculation of shrub biomass,and its role in atmospheric carbon assimilation has thus been highlighted through the findings of this study.

Labile and stabile soil organic carbon fractions in surface horizons of mountain soils–relationships with vegetation and altitude

Global and local climate changes could disturb carbon sequestration and carbon stocks in forest soils. Thus, it is important to characterize the stability of soil organic matter and the dynamics of soil organic carbon(SOC) fractions in forest ecosystems. This study had two aims:(1) to evaluate the effects of altitude and vegetation on the content of labile and stabile forms of organic carbon in the mountain soils; and(2) to assess the impact of the properties of soil organic matter on the SOC pools under changing environmental conditions. The studies were conducted in the Karkonosze Mountains(SW Poland, Central Europe). The content of the most labile fraction of carbon(dissolved organic carbon,DOC) decreases with altitude, but the content of fulvic acids(FA), clearly increases in the zone above 1000 m asl, while the stabile fraction(humins, nonhydrolyzing carbon) significantly decreases. A higher contribution of stabile forms was found in soils under coniferous forests(Norway spruce), while a smaller-under deciduous forests(European beech) and on grasslands. The expected climate change and the ongoing land use transformations in the zone above1000 m asl may lead to a substantial increase in the stable humus fraction(mainly of a non-hydrolyzing carbon) and an increase in the SOC pools, even if humus acids are characterized by a lower maturity and greater mobility favorable to soil podzolization.In the lower zone(below 1000 m asl), a decrease in the most stable humus forms can be expected,accompanied by an increase of DOC contribution,which will result in a reduction in SOC pools. Overall,the expected prevailing(spatial) effect is a decreasing contribution of the most stable humus fractions,which will be associated with a reduction in the SOC pools in medium-high mountains of temperate zone of Central Europe.

Carbon accumulations by stock change approach in tropical highland forests of Chiapas, Mexico

Changes in forest biomass and soil organic carbon reserves have strong links to atmospheric carbon dioxide concentration.Human activities such as livestock grazing,forest fires,selective logging and firewood extraction are the common disturbances that affect the carbon dynamics of the forest ecosystems.Here,we hypothesized that such anthropogenic activities significantly reduce the carbon stocks and accumulation rates in the tropical highland forests of the Sierra Madre de Chiapas in Southern Mexico.We sampled the Pinus oocarpa Scheide dominated forests within the elevation range of 900 to 1100 m above sea level in 2010,2014 and 2017.We measured the stand structural properties and used the reported allometric equations to calculate the tree carbon stocks.Stock change approach was used to calculate carbon accumulation rates.The results showed a gradual increase in carbon storage over the 7-year period from 2010 to 2017,but the rate of increase varied significantly between the study sites.The aboveground carbon stock was 107.25±11.77 Mg ha-1 for the site with lower anthropogenic intensity,compared to 74.29±16.85 Mg ha-1 for the site with higher intensity.The current annual increment for the forest with lower anthropogenic intensity was 7.81±0.65 Mg ha-1 a-1,compared to 3.87±1.03 Mg ha-1 a-1 in the site with high anthropogenic intensity.Although at varying rates,these forests are functioning as important carbon sinks.The results on carbon accumulation rates have important implications in greenhouse gas mitigations and forest change modelling in the context of changing global climate.

Topsoil organic carbon mineralization and CO_2 evolution of three paddy soils from South China and the temperature dependence

Carbon mineralization and its response to climatic warming have been receiving global attention for the last decade. Although the virtual influence of temperature effect is still in great debate, little is known on the mineralization of organic carbon （SOC） of paddy soils of China under warming. SOC mineralization of three major types of China＇s paddy soils is studied through laboratory incubation for 114 d under soil moisture regime of 70% water holding capacity at 20℃ and 25℃ respectively. The carbon that mineralized as CO2 evolved was measured every day in the first 32 d and every two days in the following days. Carbon mineralized during the 114 d incubation ranged from 3.51 to 9.22 mg CO2-C/gC at 20℃ and from 4.24 to 11.35 mg CO2-C/gC at 25℃ respectively; and a mineralizable C pool in the range of 0.24 to 0.59 gC/kg, varying with different soils. The whole course of C mineralization in the 114 d incubation could be divided into three stages of varying rates, representing the three subpools of the total mineralizable C： very actively mineralized C at 1-23 d, actively tnineralized C at 24--74 d and a slowly mineralized pool with low and more or less stabilized C mineralization rate at 75-114 d. The calculated Q10 values ranged from 1.0 to 2.4, varying with the soil types and N status. Neither the total SOC pool nor the labile C pool could account for the total mineralization potential of the soils studied, despite a well correlation of labile C with the shortly and actively mineralized C, which were shown in sensitive response to soil warming. However, the portion of microbial C pool and the soil C/N ratio controlled the C mineralization and the temperature dependence. Therefore, C sequestration may not result in an increase of C mineralization proportionally. The relative control of C bioavailability and microbial metabolic activity on C mineralization with respect to stabilization of sequestered C in the paddy soils of China is to be further studied.

Soil carbon pool in China and its global significance

Soil organic carbon density and its related characteristics of 41 soil types all over China were analyzed by using data of 745 soil profiles , and size of soil carbon pool was estimated. As a result, area-weighted averages of these 41 soil types for bulk density, profile depth, organic carbon content and profile carbon were 1. 24 tC/m3, 86. 2 cm, 3. 04% and 19. 7 kg C/m2 respectively. Total size of soil carbon pool was 185. 68 × 1009tC, which is 29 times of that in terrestrial biomass of China and 12. 6% of global soil carbon pools. Because of its huge carbon pool, soil of China plays an important role in global carbon cycle.

Temporal variation of soil carbon stock and its controlling factors over the last two decades on the southern Song-nen Plain,Heilongjiang Province

Against the current background of global climate change, the study of variations in the soil carbon pool and its controlling factors may aid in the evaluation of soil＇s role in the mitigation or enhancement of greenhouse gas. This paper studies spatial and temporal variation in the soil carbon pool and their controlling factors in the southern Song-nen Plain in Heilongjiang Province, using soil data collected over two distinct periods by the Multi-purpose Regional Geochemical Survey in 2005-2007, and another soil survey conducted in 1982-1990. The study area is a carbon source of 1479 t/km2 and in the past 20 years, from the 1980s until 2005, the practical carbon emission from the soil was 0.12 Gt. Temperature, which has been found to be linearly correlated to soil organic carbon, is the domi- nant climatologic factor controlling soil organic carbon contents. Our study shows that in the relevant area and time period the potential loss of soil organic carbon caused by rising temperatures was 0.10 Gt, the potential soil carbon emission resulting from land-use change was 0.09 Gt, and the combined potential loss of soil carbon （0.19 Gt） caused by warming and land-use change is comparable to that of fossil fuel combustion （0.21 Gt）. Due to the time delay in soil carbon pool variation, there is still 0.07 Gt in the potential emission caused by warming and land-use change that will be gradually released in the future.

The Effects of Land Use and Landscape Position on Labile Organic Carbon and Carbon Management Index in Red Soil Hilly Region,Southern China

Labile organic carbon （LOC） and carbon management index （CMI）, which are sensitive factors to the changes of environment, can improve evaluating the effect of land management practices changes on soil quality. The objective of this study was to investigate the effects of land use types and landscape positions on soil quality as a function of L0C and CMI. A field study in a small watershed in the red soil hilly region of southern China was conducted, and soil samples were collected from four typical lands （pine forest （PF） on slope land, barren hill （BH） on slope land, citrus orchard （C0） on terrace land and Cinnarnornum Camphora （CC） on terrace land） at a sampling depth of 20 cm. Soil nutrients, soil organic carbon （SOC）, L0C and CMI were measured. Results showed that the L0C and CMI correlated to not only soil carbon but also soil nutrients, and the values of LOC and CMI in different land use types followed the order CC 〉 PF 〉 CO 〉 BH at the upper- slope, while CO 〉 CC 〉 BH 〉 PF at mid-slope and down-slope. With respect to slope positions, the values of LOC and CMI in all the lands were followed the order： upper-slope 〉 down-slope 〉 mid- slope. As whole, the mean values of LOC and CMI in different lands followed the order CC 〉 CO 〉 PF 〉 BH. High CMI and LOC content were found in the terrace lands with broadleaf vegetations. These results indicated that the terracing and appropriate vegetations can increase the carbon input and lability and decrease soil erosion. However, the carbon pools and CMI in these lands were significantly lower than that in reference site. This suggested that it may require a long time for the soil to return to a high~ quality. Consequently, it is an efficient way to adopt the measures of terracing and appropriate vegetations planting in improving the content of LOC and CMI and controlling water and soil loss in fragile ecosystems.

The variation of sediments organic carbon content in Chongming east tidal flat during Scirpus mariqueter growing stage

The investigations on the organic carbon （OC） of core sediments were carried out in Chongming east tidal fiat （CM） during Scirpus mariqueter growing stage （from April to December 2004） in Yangtze Estuary. The Yangtze River annually transports a runoff discharge of 30,000 m^3/s, carrying about 480 million tons of sediments to the estuarine and coastal area, which formed a great OC pool. In the sampling spots, seven quadrats of 50 cm × 50 cm and five sediments cores of 20 cm deep （40 cm deep in December） were randomly established in order to collect vegetations and core sediments samples during the low tide each month except November. After pretreatment, the core sediments were sieved and their OC contents were measured according to the potassium dichromate method. The results show that the higher surface sediment OC content in summer comes from allochthonous terrigenous particle settlements on the Chongming east middle tidal fiat S. mariqueter zone. In autumn and winter, the decomposing of the defoliated S. mariqueter increases the surface sediments OC content. Settling velocity, sediment temperature and S. mariqueter growth are the main factors that can control the sediment carbon content. Summer is the “carbon losing” period of the tidal fiat sediments, while from September, it changes into the “carbon accumulating” period of sediment OC pool because of the decomposing of dead S. mariqueter community in the sediments. From this alternation of “carbon losing” period and “carbon accumulating” period, we conclude that carbon in the OC pool of the middle tidal fiat S. mariqueter zone sediments mainly comes from the atmospheric carbon rooted by S. mariqueter photosynthesis.

Carbon dioxide release due to change in land use in China mainland

The carbon pool and emission of carbon dioxide from terrestrial ecosystems in Chinahave been estimated. The carbon pool is 2.51×10￣9-25.2×10￣9 ton C in vegetation, and 49. 7×10￣9ton C in soil. The carbon dioxide release from terrestrial ecosystems is 0.0317× 10￣9- 0. 195× 10￣9ton C due to changes in land-use in recent years, mainly caused by deforestation and degradation ofgrassland. This carbon release due to changes in land-use is approximately 17% of the current carbondioxide emission from fossil fuel combustion and cement production in China. As compared withthe global carbon pool, the carbon pool in vegetation and in soil in China are 1.8% and 3.3% ofthe global figures, respectively.

Pool Sizes and Turnover of Soil Organic Carbon of Farmland Soil in Karst Area of Guilin

The three-pool and first-order model separates the mineralizable organic carbon into active,slow,and passive carbon pools.This paper used the model and decomposition curves of the soil organic carbon to fit the active pool and its decomposition rate,slow pool and its decomposition rate.The results showed that the size of the active pool from different profiles accounted for 2.09%-3.08% of the total soil organic carbon and the mean residue time was 3.57-17.21 days.And the size of the slow pool accounted for 3.19%-43.55% and the mean residue time was 1.12-4.94 years.Acid hydrolysis（6M HCl） was used to fractionate the passive organic carbon,which accounted for 50.83%-94.44% of the total soil organic carbon.

Carbon concentrations and carbon storage capacity of three old-growth forests in the Sila National Park,Southern Italy

Old-growth forests play a key-role in reducing atmospheric carbon dioxide(CO_(2)) concentrations by storing large CO_(2)amounts in biomass and soil over time.This quantifies the carbon pool into different forest compartments in three Mediterranean old-growth forests of Southern Italy populated by Pinus laricio,Fagus sylvatica and Abies alba.Ecosystem carbon pools have been assessed per compartment,i.e.,living trees,dead wood,litterfall(foliar and woody),roots and 0-20 cm topsoil,combining the whole old-growth forest mass,(i.e.,using tree allometric relationships,deadwood factor conversions,root-to-shoot ratios,litterfall and soil samplings) by the respective organic carbon concentrations.The results show the considerable capacity of these forest ecosystems in storing CO_(2)in biomass and soil,with carbon pool values ranging from 532.2to 596.5 Mg C ha-1.Living trees and 0-20 cm topsoil had larger carbon pool,contributing 53.0 and 22.1%,respectively.In most cases,organic carbon concentration was higher(more than 60%) than the average carbon conversion rate of 50%,especially in living trees,deadwood,and woody litterfall.This study contributes further scientific evidence of the capacity of old-growth forests in storing CO_(2)in their different compartments,with special evidence on tree biomass,litterfall and mineral soil,thereby highlighting the key role of old-growth forests within the challenge of climate change mitigation.

Natural forests in New Zealand–a large terrestrial carbon pool in a national state of equilibrium

Background:Natural forests cover approximately 29%of New Zealand’s landmass and represent a large terrestrial carbon pool.In 2002 New Zealand implemented its first representative plot-based natural forest inventory to assess carbon stocks and stock changes in these mostly undisturbed old-growth forests.Although previous studies have provided estimates of biomass or carbon stocks,these were either not fully representative or lacked data from important pools such as dead wood(coarse woody debris).The current analysis provides the most complete estimates of carbon stocks and stock changes in natural forests in New Zealand.Results:We present estimates of per hectare carbon stocks and stock changes in live and dead organic matter pools excluding soil carbon based on the first two measurement cycles of the New Zealand Natural Forest Inventory carried out from 2002 to 2014.These show that New Zealand’s natural forests are in balance and are neither a carbon source nor a carbon sink.The average total carbon stock was 227.0±14.4 tC·ha^(−1)(95%C.I.)and did not change significantly in the 7.7 years between measurements with the net annual change estimated to be 0.03±0.18 tC·ha^(−1)·yr^(−1).There was a wide variation in carbon stocks between forest groups.Regenerating forest had an averaged carbon stock of only 53.6±9.4 tC·ha^(−1) but had a significant sequestration rate of 0.63±0.25 tC·ha^(−1)·yr^(−1),while tall forest had an average carbon stock of 252.4±15.5 tC·ha^(−1),but its sequestration rate did not differ significantly from zero(−0.06±0.20 tC·ha^(−1)·yr^(−1)).The forest alliance with the largest average carbon stock in above and below ground live and dead organic matter pools was silver beech-red beech-kamahi forest carrying 360.5±34.6 tC·ha^(−1).Dead wood and litter comprised 27%of the total carbon stock.Conclusions:New Zealand’s Natural Forest Inventory provides estimates of carbon stocks including estimates for difficult to measure pools such as dead wood and roots.It also provides estimates of uncertainties including effects of model prediction error and sampling variation between plots.Importantly it shows that on a national level New Zealand’s natural forests are in balance.Nevertheless,this is a nationally important carbon pool that requires continuous monitoring to identify potential negative or positive changes.