High Carbon Stocks Research Articles

Estimating heterotrophic and autotrophic soil respiration in a semi-natural forest of Lombardy, Italy

We studied a semi-natural forest in Northern Italy that was set aside more than 50 years ago, in order to better understand the soil carbon cycle and in particular the partitioning of soil respiration between autotrophic and heterotrophic respiration. Here we report on soil organic carbon, root density, and estimates of annual fluxes of soil CO 2 as measured with a mobile chamber system at 16 permanent collars about monthly during the course of a year. We partitioned between autotrophic and heterotrophic respiration by the indirect regression method, which enabled us to obtain the seasonal pattern of single components. The soil pool of organic carbon, with 15.8 (±4.5) kg m −2 , was very high over the entire depth of 45 cm. The annual respiration rates ranged from 0.6 to 6.9 μmol CO 2 m −2 s −1 with an average value of 3.4 (±2.3) μmol CO 2 m −2 s −1 , and a cumulative flux of 1.1 kg C m −2 yr −1 . The heterotrophic component accounted for 66% of annual CO 2 efflux. Soil temperature largely controlled the heterotrophic respiration ( R 2 = 0.93), while the autotrophic component followed irradiation, pointing to the role of photosynthesis in modulating the annual course of soil respiration. Most studies on soil respiration partitioning indicate autotrophic root respiration as a first control of the spatial variability of the overall respiration, which originates mainly from the uppermost soil layers. Instead, in our forest the spatial variability of soil respiration was mainly linked to soil carbon, and deeper layers seemed to provide a significant contribution to soil respiration, a feature that may be typical for an undisturbed, naturally maturing ecosystem with well developed pedobiological processes and high carbon stocks.

Organic carbon stocks in grassland soils and their spatial distribution in Japan

AbstractTo evaluate the nationwide status of grasslands and their soil organic carbon stocks in Japan, we used 1990 as a base year and estimated: (i) the area and the spatial distribution of grasslands, and (ii) the size and the spatial distribution of their soil organic carbon stocks. The carbon stocks were estimated to a 30 cm depth based on datasets containing information on vegetation, wetlands, soils and land classifications. The total grassland area (including natural grasslands, semi‐natural grasslands, meadows/pastures and artificial grasslands for non‐agricultural use) was estimated at 18 700 km2, which is 5.0% of Japan’s total land area. Nearly two‐thirds of the total grassland area contained Andosols or Brown Forest soils, and the percentage of area covered by each soil group differed with grassland type. The estimated soil organic carbon density value (11.4 kg C m–2 for all Japanese grasslands) was consistent with previously reported values (4.0–20.2 kg C m–2 for several Japanese grasslands). A map of the soil organic carbon stocks in grasslands shows a characteristic distribution of high and low carbon stock areas. The total estimated carbon stock in grassland topsoils was 214 Tg C, which is 8.0% of the total carbon stock in Japanese topsoils. The techniques used and the results obtained in this study are valuable for the evaluation of future changes in soil organic carbon stocks in Japan. To obtain more accurate and comprehensive estimates of these changes, it is important to develop the unified grassland categorization system and to collect soil organic carbon data for several types of grasslands, at least meadows/pastures and semi‐natural grasslands for agricultural use.

Scale-dependence of aboveground carbon accumulation in secondary forests of Panama: A test of the intermediate peak hypothesis

Accumulation of aboveground carbon is one of the most important services provided by tropical secondary forests—a land-cover type that is increasing in importance globally. Carbon accumulates rapidly for the first 20years of succession, but few studies have considered forests older than 20years, and the available data do not yield a consistent pattern. Two alternative hypotheses have been proposed: (1) an asymptotic increase, with the highest carbon stocks occurring in the oldest stands, and (2) an intermediate peak, caused by roughly synchronous tree maturity (and thus high carbon stocks) after which time treefall gaps cause carbon stocks to regress. Here we revisited a well-studied tropical moist forest chronosequence in Barro Colorado Nature Monument, Central Panama, consisting of 35, 55, 85, and 115-year-old stands, as well as old-growth stands, to determine whether past evidence for the intermediate peak hypothesis was influenced by the spatial limitations of the field plots used to assess forest structure. We used airborne LiDAR (light detection and ranging) to measure carbon stocks at the scale of the original transects (0.16ha), in surrounding forest of the same age (up to 20ha), and at a landscape scale incorporating thousands of hectares not previously measured. We also compared forest structure as measured in three dimensions by LiDAR, considering vertical and horizontal variation in canopy organization, as well as the abundance of treefall gaps. Our results suggested a strong scale-dependence of aboveground carbon accumulation, supporting the intermediate peak hypothesis at the fine scale of the 0.16-ha transects, but an asymptotic model at the landscape scale incorporating thousands of hectares. Further analyses of forest structure suggest that both the limitations of small plots and intrinsic scaling of forest structure and carbon dynamics account for the scale-dependence of aboveground carbon accumulation in this secondary forest matrix.

High organic carbon stock in a karstic soil of the Middle-European Forest Province persists after centuries-long agroforestry management

Little is known on soil organic carbon (SOC) stocks in karst areas worldwide, although many of them have seen long-term application of agroforestry systems with a potential for carbon sequestration. Therefore, our study aimed to assess landscape-level SOC concentration and stock in the Silica Plateau, a part of the Slovak Karst Biosphere Reserve located in the Western Carpathians (Slovakia) with a centuries-long agroforestry record. The most represented local soil units are Chromi-Rendzic Leptosols and Chromic Cambisols with clayey loam texture, C/N ratio 9–12, and \( {\text{pH}}_{{{\text{H}}_{2} {\text{O}}}} \) 6.6–6.2 in their organo-mineral surface horizons. Mull surface humus form prevails under mixed forest stands dominated by hornbeam (Carpinus betulus L.), oak (Quercus petraea L.), and beech (Fagus sylvatica L.). A total of 2,700 soil samples were collected from 150 soil pits. Both SOC concentrations and stocks were determined for the 0–60 cm mineral soil layer. Soil stoniness was accounted for by means of electrical resistivity tomography. According to the analysis of covariance, cropland SOC concentration (0.026 g g−1) is significantly lower compared to forestland (0.040 g g−1) and pastureland (0.041 g g−1) (P < 0.01). During the period of 130 years after forest clearing, cropland SOC stock has been reduced at an exponential decay rate of ca 0.002 year−1, while the SOC stock in pastureland has increased following land use change from cropland by approximately 30% during the same period of time. Irrespective of land use history, overall SOC stock is high reaching on average 207.4 Mg ha−1, out of which 66% are stored within 0–30 cm and 34% within 30–60 cm soil layers.

CARBON SEQUESTRATION IN EIGHT WOODY NON-TIMBER FOREST SPECIES AND THEIR ECONOMIC POTENTIALS IN SOUTHWESTERN CAMEROON

Carbon sequestration potentials of 8 woody species were assessed on an ecosystem level, using the CO 2FIXV.2 model, for two scenarios. Net carbon sequestration potentials ranged from 246.23 to 306.22 Mg C ha -1 with complete rotation every 40 years, and 292 to 359.3 Mg C ha -1 with partial cut. Ricinodendron heudelotii had the highest net carbon sequestration potential (306.22 and 359.3 Mg C ha -1 for the complete and partial cuts respectively), while Cola lepidota had the least under both scenarios. There were higher carbon stocks in plant biomass than soil for all agroforests under both management regimes. Fine litter had the highest soil carbon fraction and soluble compounds had the least in all the agroforests. Under complete rotation, the agroforests had potential carbon credit values ranging from US$2756 to $3264/ha/rotation, and $ 3114 to $3678/ha/rotation with partial cut. Partial cuts allowed for higher rates of carbon accumulation, and the farmer always has a standing crop. Economic prioritization showed that Irvingia wombulu was the best (US$6.67/Kg), followed by Ricinodendron heudelotii and Afrostyrax lepidophyllus ($5.55/Kg) and the least was Trycocypha abut ($0.33/Kg). These results would aid policy makers in mitigating climate change, improving rural livelihoods, and contributing to sustainable development. Keywords: carbon stocks, CO 2FIXV.2 model, sustainability, climate change and carbon trade

Demography and biomass change in monodominant and mixed old-growth forest of the Congo

Abstract:Mbau forest covers much of the Congo, and shifts in its composition could have a large impact on the African tropics. The Ituri forest in east Congo is near a boundary between the monodominant mbau type and non-mbau mixed forest, and two 20-ha censuses of trees ≥ 1 cm diameter were carried out over 12 y to monitor forest change. Based on published diameter allometry, mbau forest had 535 Mg ha−1 biomass above ground and gained 1.1 Mg ha−1 y−1. Mixed forest had 399 Mg ha−1 and gained 3 Mg ha−1 y−1. The mbau tree (Gilbertiodendron dewevrei) increased its share of biomass from 4.1% to 4.4% in mixed forest; other common species also increased. Sapling density declined at both sites, likely because increased biomass meant shadier understorey, but the mbau tree increased in sapling density, suggesting it will become more important in the future. Tree mortality and growth rates were low relative to other tropical forests, especially in the mbau plots. Shifting toward G. dewevrei would represent a large gain in carbon in the mixed forest, but mbau is presently more important as a high-carbon stock: biomass lost during forest harvest could not recuperate for centuries due to slow community dynamics.

Sitka spruce (Picea sitchensis) forests in Atlantic Europe: changes in forest management and possible consequences for carbon sequestration

Sitka spruce (Picea sitchensis (Bong.) Carr.) was introduced in Atlantic Europe in the nineteenth century. Forests of this species are the major forest type in the United Kingdom and Ireland, with substantial areas in Norway, France and Denmark. Most forests are managed under a patch clearfelling regime on comparatively short (35–50 years) rotations. However, forest policies in a number of countries seek to increase the structural and species diversity of Sitka spruce forests: such measures are also proposed to help adapt to projected climate change and management of climate risk. Datasets from 26 experimental plots in Atlantic Europe representing existing and alternative management approaches showed high carbon stocks under current management and lower stocks in all alternatives. In addition, there was little evidence of Sitka spruce being grown successfully in long-term intimate mixture. Thinning is required to increase the diversity of Sitka spruce forests, but this can result in increased risk of wind damage, and hence reduction in carbon stocks, other than on the most sheltered sites. Such risks will be higher with the wetter soils anticipated from greater winter rainfall. Future management of Sitka spruce forests for carbon sequestration should focus both on improvement of current management (e.g. use of higher-yielding genotypes) and on developing wind-stable stands through careful thinning to act as long-term carbon stores.

The carbon costs of mitigating high-severity wildfire in southwestern ponderosa pine

Forests provide climate change mitigation benefit by sequestering carbon during growth. This benefit can be reversed by both human and natural disturbances. While some disturbances such as hurricanes are beyond the control of humans, extensive research in dry, temperate forests indicates that wildfire severity can be altered as a function of forest fuels and stand structural manipulations. The purpose of this study was to determine if current aboveground forest carbon stocks in fire-excluded southwestern ponderosa pine forest are higher than prefire exclusion carbon stocks reconstructed from 1876, quantify the carbon costs of thinning treatments to reduce high-severity wildfire risk, and compare posttreatment (thinning and burning) carbon stocks with reconstructed 1876 carbon stocks. Our findings indicate that prefire exclusion forest carbon stocks ranged from 27.9 to 36.6 Mg C ha 1 and that the current fire-excluded forest structure contained on average 2.3 times as much live tree carbon. Posttreatment carbon stocks ranged from 37.9 to 50.6 Mg C ha 1 as a function of thinning intensity. Previous work found that these thinning and burning treatments substantially increased the 6.1 m wind speed necessary for fire to move from the forest floor to the canopy (torching index) and the wind speed necessary for sustained crown fire (crowning index), thereby reducing potential fire severity. Given the projected drying and increase in fire prevalence in this region as a function of changing climatic conditions, the higher carbon stock in the fire-excluded forest is unlikely to be sustainable. Treatments to reduce high-severity wildfire risk require trade-offs between carbon stock size and carbon stock stability.

Spatial interpolation of carbon stock: a case study from the Western Ghats biodiversity hotspot, India

Carbon stock distribution in different tropical forest types in India is rarely studied although India is a country with mega-diversity. The present study estimates the biomass and carbon stock of major tropical forest types in India, and attempts to identify suitable interpolation techniques for mapping carbon stock. Empirically derived allometric equations and carbon conversion coefficients were used to estimate the aboveground biomass and carbon stock, respectively. The point estimates were interpolated to spatial surface using different interpolation techniques. Two main modelling approaches were implemented: deterministic modelling and stochastic modelling. Deterministic modelling was to interpolate point information using similarities between measured points (inverse distance weighted (IDW) interpolation), and fitting a smoothing curve along the measured points (polynomial interpolation). In stochastic modelling, ordinary kriging (OK) was employed using parameters derived from semivariograms. The results showed that the average carbon stock in the study area was 84 t/ha. The highest carbon stock was in evergreen forest and the lowest in thorny scrub forest. Validation of the model using the mean and RMS errors indicated that ordinary kriging performs better than IDW and polynomial interpolations.

Carbon storage in soils of Southeastern Nigeria under different management practices

BackgroundChanges in agricultural practices-notably changes in crop varieties, application of fertilizer and manure, rotation and tillage practices-influence how much and at what rate carbon is stored in, or released from, soils. Quantification of the impacts of land use on carbon stocks in sub-Saharan Africa is challenging because of the spatial heterogeneity of soil, climate, management conditions, and due to the lack of data on soil carbon pools of most common agroecosystems. This paper provides data on soil carbon stocks that were collected at 10 sites in southeastern Nigeria to characterize the impact of soil management practices.ResultsThe highest carbon stocks, 7906-9510 gC m-2, were found at the sites representing natural forest, artificial forest and artificial grassland ecosystems. Continuously cropped and conventionally tilled soils had about 70% lower carbon stock (1978-2822 gC m-2). Thus, the soil carbon stock in a 45-year old Gmelina forest was 8987 gC m-2, whereas the parts of this forest, that were cleared and continuously cultivated for 15 years, had 75% lower carbon stock (1978 gC m-2). The carbon stock of continuously cropped and conventionally tilled soils was also 25% lower than the carbon stock of the soil cultivated by use of conservation tillage.ConclusionIntroducing conservation tillage practices may reduce the loss of soil carbon stocks associated with land conversion. However, the positive effect of conservation tillage is not comparable to the negative effect of land conversion, and may not result in significant accumulation of carbon in southeastern Nigeria soils.

EU Environmental Sustainability Requirements and Brazilian Biofuel Exports Exigences de durabilité environnementale de l’Union européenne et exportations brésiliennes de biocarburants Die EU-Anforderungen für ökologische Nachhaltigkeit und Biokraftsto

This article explores the EU's goal to obtain 10 per cent of its transport energy from biofuels by 2020 and considers how the environmental sustainability criteria in the EU's new renewable energy directive might apply to Brazil. In order to count towards the goal, biofuels must achieve greenhouse gas savings as high as 60 per cent after 2017. Regarding Brazil's leading biofuels, the directive assigns a default savings level of 71 per cent to sugarcane-based bioethanol and 31 per cent to soybean-based biodiesel. Biofuels obtained from biomass grown on lands of high carbon stock or high biodiversity value would not qualify as sustainable under the directive, based on the land's status in January 2008. However, the directive leaves open the possibility of converting some savannahs and open forests to biomass production. Amendments reported by the European Parliament's Committee on Industry, Research and Energy (ITRE) but not incorporated within the directive would have called on second-generation biofuels and vehicles powered by renewable sources of electricity or hydrogen to supply at least 40 per cent of the 10 per cent goal, and they would have treated all of Brazil's savannahs and many of its open forests as unsustainable places for biomass production. Copyright No claim to original US government works. Journal compilation (c) The Agricultural Ecomomics Society and the European Association of Agricultural Economists 2010.

Soil organic carbon stock and carbon efflux in deep soils of desert and oasis

An experiment was carried out in two soils of oasis farmland and the surrounding desert at the southern periphery of the Gurbantonggut Desert, in central Asia, to test the effects of land use on soil organic carbon (SOC) stock and carbon efflux in deep soil. The result showed that although SOC content in the topsoil (0–0.2 m) decreased by 27% after desert soil was cultivated, total carbon stock within the soil profile (0–2.5 m) increased by 57% due to the significant increase in carbon stock at 0.2- to 2.5-m depth, and carbon efflux also markedly increased at 0- to 0.6-m depth. In the topsoil, the carbon process of the oasis was mainly dominated by consumption; in the subsoil (0.2–0.6 m) it was likely to be co-dominated by storage and consumption, and the greatest difference in SOC stock between the two soils also lay in this layer; while in the deep layer (0.6–2.5 m) of the oasis, with a more stable carbon stock, there was carbon storage dominated. Moreover, carbon stocks in the deep layer of the two soils contributed about 65% of the total carbon stocks, and correspondingly, microbial activities contributed 71% to the total microbial activity in the entire soil profile, confirming the importance of carbon cycling in the deep layer. Desert cultivation in this area may produce unexpectedly high carbon stocks from the whole profile despite carbon loss in the topsoil.

Soil carbon changes upon secondary succession in Imperata grasslands (East Kalimantan, Indonesia)

Soil carbon changes upon secondary succession in Imperata grasslands are important both for their effect on potential production and for possible implications of forest degradation and regeneration on global climate change. We studied the effect of forest regeneration after fire in Imperata (speargrass) grasslands of East Kalimantan on soil properties, using 47 plots that last burned in 2004, 94 plots that last burned in 2003, 126 plots last burned before 2003, 43 plots of secondary forest, and 28 plots of primary forest. Although soil carbon stocks increase upon natural regeneration from grassland to secondary forest, highest carbon stocks are found in the later regeneration phases and lowest under primary forest. This is contrary to the situation in other forest systems. Low C stocks under primary forests may be due to extremely low fertility, combined with shallow soils and low root mass in the topsoil. Root density—as observed in the field—is much higher under the grass vegetation. The effects of regeneration on soil are strongest in the A-horizon, where soil carbon content increases with 14%, from 14.5 g kg − 1 in Imperata grassland to 16.5 g kg − 1 in secondary forest, while carbon stocks in the A-horizon increase from 16.51 ton C ha − 1 to 18.70 ton C ha − 1. This is accompanied by a decrease in pH and an increase in bulk density. The total soil carbon stocks in Kalimantan (fixed mass, approximate depth section 40 cm) are 36.19 ton ha − 1 in Imperata grassland, 38.98 ton ha − 1 in secondary forest and 33.19 ton ha − 1 in primary forest, which is considerably lower than in Sumatra. Above-ground C/below-ground C ratios are higher in Kalimantan primary forest but lower in Kalimantan secondary forest than in Sumatra. Soil carbon stocks in Imperata grassland could be lower than previously thought. This has important consequences for carbon sequestration projects in East Kalimantan, because carbon storage potentials could be higher.

Climatic regions as an indicator of forest coarse and fine woody debris carbon stocks in the United States

BackgroundCoarse and fine woody debris are substantial forest ecosystem carbon stocks; however, there is a lack of understanding how these detrital carbon stocks vary across forested landscapes. Because forest woody detritus production and decay rates may partially depend on climatic conditions, the accumulation of coarse and fine woody debris carbon stocks in forests may be correlated with climate. This study used a nationwide inventory of coarse and fine woody debris in the United States to examine how these carbon stocks vary by climatic regions and variables.ResultsMean coarse and fine woody debris forest carbon stocks vary by Köppen's climatic regions across the United States. The highest carbon stocks were found in regions with cool summers while the lowest carbon stocks were found in arid desert/steppes or temperate humid regions. Coarse and fine woody debris carbon stocks were found to be positively correlated with available moisture and negatively correlated with maximum temperature.ConclusionIt was concluded with only medium confidence that coarse and fine woody debris carbon stocks may be at risk of becoming net emitter of carbon under a global climate warming scenario as increases in coarse or fine woody debris production (sinks) may be more than offset by increases in forest woody detritus decay rates (emission). Given the preliminary results of this study and the rather tenuous status of coarse and fine woody debris carbon stocks as either a source or sink of CO2, further research is suggested in the areas of forest detritus decay and production.

CARBON SEQUESTRATION POTENTIAL IN ABOVEGROUND BIOMASS OF THONG PHA PHUM NATIONAL FOREST, THAILAND

This study assessed the potential of carbon sequestration on aboveground biomass in the different forest ecosystems in Thong Pha Phum National Forest, Thailand. The assessment was based on a total inventory for woody stem at � 4.5 cm diameter at breast height (DBH). Aboveground biomass was estimated using allometric equation and aboveground carbon stock was calculated by multiplying the 0.5 conversion factor to the biomass. As the results, carbon sequestration showed varied in different types of forests. Tropical rain forest (Ton Mai Yak station) higher carbon stock than dry evergreen forest (KP 27 station) and mixed deciduous forest (Pong Phu Ron station) as 137.73± 48.07, 70.29± 7.38 and 48.14± 16.72 tonne C/ha, respectively. Habitat variability caused differences of biomass accumulation, species composition and the allometric relationships of forests. In the study area, all forest had a similar pattern of tree size class, with a dominant size class at � 4.5-20 cm. The � 4.5- 20 cm trees potentially provided a greater carbon sequestration in tropical rain forest and dry evergreen forest while the size of > 20- 40 cm gave potentially high carbon sequestration in mixed deciduous forest. Due to the trees have the lowest carbon sequestration but they considerably grow up to the further size classes. Apparently, they will be able to increase more biomass accumulation and store more carbon. In conclusion, the greatest carbon sequestration potential is in mixed deciduous forest and followed by tropical rain forest and dry evergreen forest in Thong Pha Phum National Forest. Finally, the appropriate forest ecosystem management can be an alternative solution for carbon dioxide reduction in terms of carbon sink role.

Tree Diversity and Carbon Sinks: Role of Village Agro-ecosystems in the Western Ghats, Karnataka, India

Tree species richness, diversity index, standing biomass and biomass carbon stocks were estimated in six villages located under three agro-ecological zones, namely, coastal, hill and plains of Uttara Kannada district, Western Ghats, Peninsular India. The study showed that land use categories other than forest support higher tree species diversity. High basal area, standing biomass and carbon stock in non-forest land categories indicates their potential as carbon sinks and for promotion of species diversity. Inclusion of other non-forest land use categories in afforestation programmes for promotion of multipurpose tree species for conservation of diversity and for enhancing carbon sinks is suggested. There is a need to promote synergy between biodiversity conservation and carbon sequestration under carbon mitigation projects.

Influences of global change on carbon sequestration by agricultural and forest soils

Global change — including warmer temperatures, higher CO2 concentrations, increased nitrogen deposition, increased frequency of extreme weather events, and land use change — affects soil carbon inputs (plant litter), and carbon outputs (decomposition). Warmer temperatures tend to increase both plant litter inputs and decomposition rates, making the net effect on soil carbon sequestration uncertain. Rising atmospheric carbon dioxide levels may be partly offset by rising soil carbon levels, but this is the subject of considerable interest, controversy, and uncertainty. Current land use changes have a net negative impact on soil carbon. Desertification and erosion associated with overgrazing and excess fuelwood harvesting, conversion of natural ecosystems into cropland and pasture land, and agricultural intensification are causing losses of soil carbon. Losses increase in proportion to the severity and duration of damage to root systems. Strategic landscape-level deployment of plants through agroforestry systems and riparian plantings may represent an efficient way to rebuild total ecosystem carbon, while also stabilizing soils and hydrologic regimes, and enhancing biodiversity. Many options exist for increasing carbon sequestration on croplands while maintaining or increasing production. These include no-till farming, additions of nitrogen fertilizers and manure, and irrigation and paddy culture. Article 3.4 of the Kyoto Protocol has stimulated intense interest in accounting for land use change impacts on soil carbon stocks. Most Annex I parties are attempting to estimate the potential for increased agricultural soil carbon sequestration to partly offset their growing fossil fuel greenhouse gas emissions. However, this will require demonstrating and verifying carbon stock changes, and raises an issue of how stringent a definition of verification will be adopted by parties. Soil carbon levels and carbon sequestration potential vary widely across landscapes. Wetlands contain extremely important reservoirs of soil carbon in the form of peat. Clay and silt soils have higher carbon stocks than sandy soils, and show a greater and more prolonged response to carbon sequestration measures such as afforestation. Increased knowledge of soil organisms and their activities can improve our understanding of how soil carbon will respond to global change. New techniques using soil organic matter fractionation and stable C isotopes are also making major contributions to our understanding of this topic. Key words: climate change, carbon dioxide (CO2), nitrogen, soil respiration, land use change, plant roots, afforestation, no-till.

How to Evaluate Carbon Sequestration by Forests

Enhancing carbon sequestration by forests is important for mitigation of global carbon dioxide. However, it is always necessary to consider the relationship between carbon sequestration and carbon stock. Enhancing carbon sequestration and maximizing carbon stock are both important for the strategies for mitigation of carbon dioxide.Carbon sequestration rate and amount of carbon accumulation vary according to forest stand development stage, and the peak of sequestration rate and the highest level of carbon stock cannot be realized at the same time. The peak of carbon sequestration rate is fond in young stage, while highest carbon stock is found in old-growth stage. So the target stand structure for enhancing carbon sequestration should be aimed from young stage to mature stage, while that for maintaining high carbon stock should be aimed in old-growth-stage.Enhancing carbon sequestration can be realized by forest management for timber production and maintaining high carbon stock can be realized by preservation of forest ecosystems. Energy for processing materials can be reduced by using timber for materials and the consumption of fossil fuels can be reduced by using wood for energy. Using wood is important for establishing recycling-based society.

Sources of organic carbon in mangrove sediments: variability and possible ecological implications

Mangrove sediments from three different mangrove ecosystems (Coringa Wildlife Sanctuary in the Godavari Delta, Andhra Pradesh, India, and Galle and Pambala, south-west Sri Lanka) were analysed for their organic carbon content, elemental ratios (C:N) and carbon stable isotope composition. Organic carbon content (0.6 – 31.7% dry weight), C/N ratios (7.0 – 27.3) and δ 13 C (between −29.4 and −20.6‰) showed a wide range of values. Lower stocks of organic carbon coincided with low C/N (atom) ratios and less negative δ 13 C values, indicating import of marine or estuarine particulate suspended matter. High organic carbon stocks coincided with high C/N ratios and δ 13 C values close, but not equal, to those of the mangrove vegetation. The variations observed in this study and published literature data could be adequately described by a simple two-end mixing model, whereby marine/estuarine suspended matter and mangrove litter were taken as end members. Thus, while in some mangrove ecosystems or vegetation zones, organic carbon stocks can be very high and are almost entirely of mangrove origin, there also appear to be cases in which deposited estuarine or marine suspended matter is the dominant source of organic carbon and nitrogen in mangrove sediments. This situation is remarkably similar to that observed in temperate salt marsh ecosystems where the importance of local vascular plant production to the sediment organic carbon pool is equally variable. The observed high variability in organic matter origin is thought to have a major impact on the overall carbon dynamics in intertidal mangrove ecosystems.

Forest carbon sequestration and harvests in Scots pine stand under different climate and nitrogen deposition scenarios

In this study, effects of altered rotation length, nitrogen deposition and changing climate on harvest removal and carbon sequestration of forest, as well as on economic profitability of forestry, were assessed. This study was based on simulations with a gap-type forest succession model in the conditions that represent Scots pine stands in southern Finland. Both warmer climatic conditions and increased nitrogen deposition enhanced forest productivity and timber yield. This also shortened the optimum rotations based on mean annual yield and soil expectation value. The highest carbon stock in forests, i.e. the highest mean annual carbon stock in the forest over a rotation period, was achieved with long rotations and higher nitrogen deposition. However, a warmer climate had an opposite effect on the forest carbon stock, because enhanced decomposition of soil organic matter resulted in a lower carbon stock in the forest soil.