Long‐term recovery of the functional community assembly and carbon pools in an African tropical forest succession

On the African continent, the population is expected to expand fourfold in the next century, which will increasingly impact the global carbon cycle and biodiversity conservation. Therefore, it is of vital importance to understand how carbon stocks and community assembly recover after slash‐and‐burn events in tropical second growth forests. We inventoried a chronosequence of 15 1‐ha plots in lowland tropical forest of the central Congo Basin and evaluated changes in aboveground and soil organic carbon stocks and in tree species diversity, functional composition, and community‐weighted functional traits with succession. We aimed to track long‐term recovery trajectories of species and carbon stocks in secondary forests, comparing 5 to 200 + year old secondary forest with reference primary forest. Along the successional gradient, the functional composition followed a trajectory from resource acquisition to resource conservation, except for nitrogen‐related leaf traits. Despite a fast, initial recovery of species diversity and functional composition, there were still important structural and carbon stock differences between old growth secondary and pristine forest, which suggests that a full recovery of secondary forests might take much longer than currently shown. As such, the aboveground carbon stocks of 200 + year old forest were only 57% of those in the pristine reference forest, which suggests a slow recovery of aboveground carbon stocks, although more research is needed to confirm this observation. The results of this study highlight the need for more in‐depth studies on forest recovery in Central Africa, to gain insight into the processes that control biodiversity and carbon stock recovery.     

Stocks of carbon and nitrogen and partitioning between above- and belowground pools in the Brazilian coastal Atlantic Forest elevation range

We estimated carbon and nitrogen stocks in aboveground biomass (AGB) and belowground biomass (BGB) along an elevation range in forest sites located on the steep slopes of the Serra do Mar on the north coast of the State of São Paulo, southeast Brazil. In elevations of 100 m (lowland), 400 m (submontane), and 1000 m (montane) four 1-ha plots were established, and above- (live and dead) and belowground (live and dead) biomass were determined. Carbon and nitrogen concentrations in each compartment were determined and used to convert biomass into carbon and nitrogen stocks. The carbon aboveground stock (C_AGB) varied along the elevation range from approximately 110 to 150 Mg·ha⁻¹, and nitrogen aboveground stock (N_AGB), varied from approximately 1.0 to 1.9 Mg·ha⁻¹. The carbon belowground stock (C_BGB) and the nitrogen belowground stock (N_BGB) were significantly higher than the AGB and varied along the elevation range from approximately 200–300 Mg·ha⁻¹, and from 14 to 20 Mg·ha⁻¹, respectively. Finally, the total carbon stock (C_TOTAL) varied from approximately 320 to 460 Mg·ha⁻¹, and the nitrogen total stock (N_TOTAL) from approximately 15 to 22 Mg·ha⁻¹. Most of the carbon and nitrogen stocks were found belowground and not aboveground as normally found in lowland tropical forests. The above- and belowground stocks, and consequently, the total stocks of carbon and nitrogen increased significantly with elevation. As the soil and air temperature also decreased significantly with elevation, we found a significantly inverse relationship between carbon and nitrogen stocks and temperature. Using this inverse relationship, we made a first approach estimate that an increase of 1°C in soil temperature would decrease the carbon and nitrogen stocks in approximately 17 Mg·ha⁻¹ and 1 Mg·ha⁻¹ of carbon and nitrogen, respectively.     

The age of managed heathland communities: implications for carbon storage?

Background and aims

Shrublands are ecosystems vulnerable to climate changes, with key functions such as carbon storage likely to be affected. In dwarf shrublands dominated by Calluna vulgaris, the aboveground carbon allocation is associated with community age and phase of development. As the Calluna community grows older, a shift to net biomass loss occurs and it was hypothesized this would result in carbon stock increases within the soil.

Methods

The interaction of community age with ecosystem carbon stocks was investigated through a chronosequence study on three Calluna communities, aged 11, 18 and 27 years.

Results

Aboveground Calluna carbon stock increased significantly from the 11 year community (0.73 kg C m^?2) to the 18 year community (1.11 kg C m^?2) but did not significantly change from 18 to 27 years (1.0 kg C m^?2), indicating a net carbon gain that corresponded with the growth phase of the Calluna plants. Moss was also found to be a relatively large contributor to aboveground carbon stock (e.g. 30 % in the Young community). Moss has often been excluded in aboveground assessments on Calluna heathlands which may have led to previous stock underestimation. Belowground carbon stocks to 25 cm were six to nine times greater than in the aboveground pools. For example in the Young community, 8 % of the carbon stock was located aboveground, 35 % in the organic layer and 55 % in the mineral soil.

Conclusions

Increased heathland age resulted in increased aboveground carbon stock until peak production was reached at approximately 18 years of age. However, the proportionally large belowground carbon stock eclipsed any aboveground effect when total carbon stocks were considered. The investigation emphasized both the importance of including the mineral soil in sampling programs and of consider all major species, such as bryophytes, and vegetation age in carbon stock assessments.     

Long‐term changes in forest carbon under temperature and nitrogen amendments in a temperate northern hardwood forest

Currently, forests in the northeastern United States are net sinks of atmospheric carbon. Under future climate change scenarios, the combined effects of climate change and nitrogen deposition on soil decomposition, aboveground processes, and the forest carbon balance remain unclear. We applied carbon stock, flux, and isotope data from field studies at the Harvard forest, Massachusetts, to the ForCent model, which integrates above‐ and belowground processes. The model was able to represent decadal‐scale measurements in soil C stocks, mean residence times, fluxes, and responses to a warming and N addition experiment. The calibrated model then simulated the longer term impacts of warming and N deposition on the distribution of forest carbon stocks. For simulation to 2030, soil warming resulted in a loss of soil organic matter (SOM), decreased allocation to belowground biomass, and gain of aboveground carbon, primarily in large wood, with an overall small gain in total system carbon. Simulated nitrogen addition resulted in a small increase in belowground carbon pools, but a large increase in aboveground large wood pools, resulting in a substantial increase in total system carbon. Combined warming and nitrogen addition simulations showed a net gain in total system carbon, predominately in the aboveground carbon pools, but offset somewhat by losses in SOM. Hence, the impact of continuation of anthropogenic N deposition on the hardwood forests of the northeastern United States may exceed the impact of warming in terms of total ecosystem carbon stocks. However, it should be cautioned that these simulations do not include some climate‐related processes, different responses from changing tree species composition. Despite uncertainties, this effort is among the first to use decadal‐scale observations of soil carbon dynamics and results of multifactor manipulations to calibrate a model that can project integrated aboveground and belowground responses to nitrogen and climate changes for subsequent decades.     

Carbon pools of an intact forest in Gabon

Quantitative and qualitative loss of tropical forests prompted international policy agendas to slow down forest loss through reducing emissions from deforestation and forest degradation (REDD)+, ensuring carbon offset payments to developing countries. So far, many African countries lack reliable forest carbon data and monitoring systems as required by REDD+. In this study, we estimate the carbon stocks of a naturally forested landscape unaffected by direct human impact. We used data collected from 34 plots randomly distributed across the Mount Birougou National Park (690 km²) in southern Gabon. We used tree‐level data on species, diameter, height, species‐specific wood density and carbon fraction as well as site‐level data on dead wood, soil and litter carbon to calculate carbon content in aboveground, belowground, dead wood, soil and litter as 146, 28, 14, 186 and 7 Mg ha^?1, respectively. Results may serve as a benchmark to assess ecosystem carbon loss/gain for the Massif du Chaillu in Gabon and the Republic of Congo, provide field data for remote sensing and also may contribute to establish national monitoring systems.     

Elevation effects on the carbon budget of tropical mountain forests (S Ecuador): the role of the belowground compartment

Carbon storage and sequestration in tropical mountain forests and their dependence on elevation and temperature are not well understood. In an altitudinal transect study in the South Ecuadorian Andes, we tested the hypotheses that (i) aboveground net primary production (ANPP) decreases continuously with elevation due to decreasing temperatures, whereas (ii) belowground productivity (BNPP) remains constant or even increases with elevation due to a shift from light to nutrient limitation of tree growth. In five tropical mountain forests between 1050 and 3060 m a.s.l., we investigated all major above‐ and belowground biomass and productivity components, and the stocks of soil organic carbon (SOC). Leaf biomass, stemwood mass and total aboveground biomass (AGB) decreased by 50% to 70%, ANPP by about 70% between 1050 and 3060 m, while stem wood production decreased 20‐fold. Coarse and large root biomass increased slightly, fine root biomass fourfold, while fine root production (minirhizotron study) roughly doubled between 1050 and 3060 m. The total tree biomass (above‐ and belowground) decreased from about 320 to 175 Mg dry mass ha^?1, total NPP from ca. 13.0 to 8.2 Mg ha^?1 yr^?1. The belowground/aboveground ratio of biomass and productivity increased with elevation indicating a shift from light to nutrient limitation of tree growth. We propose that, with increasing elevation, an increasing nitrogen limitation combined with decreasing temperatures causes a large reduction in stand leaf area resulting in a substantial reduction of canopy carbon gain toward the alpine tree line. We conclude that the marked decrease in tree height, AGB and ANPP with elevation in these mountain forests is caused by both a belowground shift of C allocation and a reduction in C source strength, while a temperature‐induced reduction in C sink strength (lowered meristematic activity) seems to be of secondary importance.     

Contribution of above‐ and belowground bioenergy crop residues to soil carbon

GHG mitigation by bioenergy crops depends on crop type, management practices, and the input of residue carbon (C) to the soil. Perennial grasses may increase soil C compared to annual crops because of more extensive root systems, but it is less clear how much soil C is derived from above‐ vs. belowground inputs. The objective of this study was to synthesize the existing knowledge regarding soil C inputs from above‐ and belowground crop residues in regions cultivated with sugarcane, corn, and miscanthus, and to predict the impact of residue removal and tillage on soil C stocks. The literature review showed that aboveground inputs to soil C (to 1‐m depth) ranged from 70% to 81% for sugarcane and corn vs. 40% for miscanthus. Modeled aboveground C inputs (to 30 cm depth) ranged from 54% to 82% for sugarcane, but were 67% for miscanthus. Because 50% of observed miscanthus belowground biomass is below 30 cm depth, it may be necessary to increase the depth of modeled soil C dynamics to reconcile modeled belowground C inputs with measured. Modeled removal of aboveground corn residue (25–100%) resulted in C stock reduction in areas of corn–corn–soybean rotation under conventional tillage, while no‐till management lessoned this impact. In sugarcane, soil C stocks were reduced when total aboveground residue was removed at one site, while partial removal of sugarcane residue did not reduce soil C stocks in either area. This study suggests that aboveground crop residues were the main C‐residue source to the soil in the current bioethanol sector (corn and sugarcane) and the indiscriminate removal of crop residues to produce cellulosic biofuels can reduce soil C stocks and reduce the environmental benefits of bioenergy. Moreover, a switch to feedstocks such as miscanthus with more allocation to belowground C could increase soil C stocks at a much faster rate.     

Soil carbon stocks across tropical forests of Panama regulated by base cation effects on fine roots

Tropical forests are the most carbon (C)-rich ecosystems on Earth, containing 25–40% of global terrestrial C stocks. While large-scale quantification of aboveground biomass in tropical forests has improved recently, soil C dynamics remain one of the largest sources of uncertainty in Earth system models, which inhibits our ability to predict future climate. Globally, soil texture and climate predict ≤ 30% of the variation in soil C stocks, so ecosystem models often predict soil C using measures of aboveground plant growth. However, this approach can underestimate tropical soil C stocks, and has proven inaccurate when compared with data for soil C in data-rich northern ecosystems. By quantifying soil organic C stocks to 1 m depth for 48 humid tropical forest plots across gradients of rainfall and soil fertility in Panama, we show that soil C does not correlate with common predictors used in models, such as plant biomass or litter production. Instead, a structural equation model including base cations, soil clay content, and rainfall as exogenous factors and root biomass as an endogenous factor predicted nearly 50% of the variation in tropical soil C stocks, indicating a strong indirect effect of base cation availability on tropical soil C storage. Including soil base cations in C cycle models, and thus emphasizing mechanistic links among nutrients, root biomass, and soil C stocks, will improve prediction of climate-soil feedbacks in tropical forests.     

Control of soil pH on turnover of belowground organic matter in subalpine grassland

Grasslands store substantial amounts of carbon in the form of organic matter in soil and roots. At high latitudes and elevation, turnover of these materials is slow due to various interacting biotic and abiotic constraints. Reliable estimates on the future of belowground carbon storage in cold grassland soils thus require quantitative understanding of these factors. We studied carbon turnover of roots, labile coarse particulate organic matter (cPOM) and older non-cPOM along a natural pH gradient (3.9–5.9) in a subalpine grassland by utilizing soil fractionation and radiocarbon dating. Soil carbon stocks and root biomass, turnover, and decomposability did not scale with soil pH whereas mean residence times of both soil organic matter fractions significantly increased with declining pH. The effect was twice as strong for non-cPOM, which was also stronger enriched in ¹⁵N at low pH. Considering roots as important precursors for cPOM, the weaker soil pH effect on cPOM turnover may have been driven by comparably high root pH values. At pH < 5, long non-cPOM mean residence times were probably related to pH dependent changes in substrate availability. Differences in turnover along the pH gradient were not reflected in soil carbon stocks because aboveground productivity was lower under acidic conditions and, in turn, higher inputs from aboveground plant residues compensated for faster soil carbon turnover at less acidic pH. In summary, the study provides evidence for a strong and differential regulatory role of pH on the turnover of soil organic matter that needs consideration in studies aiming to quantify effects of changing environmental conditions on belowground carbon storage.     

菌根真菌影响森林生态系统碳循环研究进展

森林生态系统在全球碳(C)储量中占据极为重要的地位。菌根真菌广泛存在于森林生态系统中,在森林生态系统C循环过程中发挥重要的作用。阐述了不同菌根类型真菌在森林生态系统C循环过程中的功能,对比了温带/北方森林与热带/亚热带森林中菌根真菌介导的C循环研究方面新近取得的研究结果。发现温带和北方森林的外生菌根(EcM)植物对地上生物量C的贡献相对较小,然而是地下C储量的主要贡献者;以丛枝菌根(AM)共生为主的热带/亚热带森林地表生物量占比较高,表明AM植被对热带/亚热带森林地上生物量C的贡献相对较大。我们还就全球变化背景下,菌根真菌及其介导的森林生态系统C汇功能,以及不同菌根类型树种影响C循环的机制等进行了总结。菌根真菌通过影响凋落物分解、土壤有机质形成及地下根系生物量,进而影响整个森林生态系统的C循环功能。菌根介导的森林C循环过程很大程度上取决于(优势)树木的菌根类型和森林土壤中菌根真菌的群落结构。最后指出了当前研究存在的主要问题以及未来研究展望。本文旨在明确菌根真菌在森林生态系统C循环转化过程中的重要生态功能,有助于准确地评估森林生态系统C汇现状,为应对全球变化等提供重要的依据。     

Environmental Consequences of the Demise in Swidden Cultivation in Southeast Asia: Carbon Storage and Soil Quality

The effects of swidden cultivation on carbon storage and soil quality are outlined and compared to the effects of the intensified production systems that swidden systems of Southeast Asia transform into. Time-averaged aboveground carbon stocks decline by about 90% if the long fallow periods of traditional swidden cultivation are reduced to 4 years and by about 60% if swidden cultivation is converted to oil palm plantations. Stocks of soil organic carbon (SOC) in tree plantations are 0–40% lower than stocks in swidden cultivation, with the largest losses found in mechanically established oil palm plantations. Impacts of tree plantations on soil quality are to a large extent determined by management. Conversion of swiddening to continuous annual cropping systems brings about substantial losses of time-averaged aboveground carbon stocks, reductions of SOC stocks and generally leads to declining soil quality. Knowledge of carbon storage in belowground biomass of tree based systems of the tropics is sparse but failure to include this pool in carbon inventories may significantly underestimate the total biomass of the systems. Moreover, studies that consider the ecological reasons behind farmers’ land use decisions as well as spatial variability in biogeophysical and edaphological parameters are needed to evaluate the effects of the ongoing land use transitions in Southeast Asia.     

A disconnect between O horizon and mineral soil carbon – Implications for soil C sequestration

Changing inputs of carbon to soil is one means of potentially increasing carbon sequestration in soils for the purpose of mitigating projected increases in atmospheric CO₂ concentrations. The effect of manipulations of aboveground carbon input on soil carbon storage was tested in a temperate, deciduous forest in east Tennessee, USA. A 4.5-year experiment included exclusion of aboveground litterfall and supplemental litter additions (three times ambient) in an upland and a valley that differed in soil nitrogen availability. The estimated decomposition rate of the carbon stock in the O horizon was greater in the valley than in the upland due to higher litter quality (i.e., lower C/N ratios). Short-term litter exclusion or addition had no effect on carbon stock in the mineral soil, measured to a depth of 30 cm, or the partitioning of carbon in the mineral soil between particulate- and mineral-associated organic matter. A two-compartment model was used to interpret results from the field experiments. Field data and a sensitivity analysis of the model were consistent with little carbon transfer between the O horizon and the mineral soil. Increasing aboveground carbon input does not appear to be an effective means of promoting carbon sequestration in forest soil at the location of the present study because a disconnect exists in carbon dynamics between O horizon and mineral soil. Factors that directly increase inputs to belowground soil carbon, via roots, or reduce decomposition rates of organic matter are more likely to benefit efforts to increase carbon sequestration in forests where carbon dynamics in the O horizon are uncoupled from the mineral soil.     

Control of “blue carbon” storage by mangrove ageing: Evidence from a 66‐year chronosequence in French Guiana

The role of mangroves in the blue carbon stock is critical and requires special focus. Mangroves are carbon‐rich forests that are not in steady‐state equilibrium at the decadal time scale. Over the last decades, the structure and zonation of mangroves have been largely disturbed by coastal changes and land use conversions. The amount of time since the last disturbance is a key parameter determining forest structure, but it has so far been overlooked in mangrove carbon stock projections. In particular, the carbon sequestration rates among mangrove successional ages after (re)establishment are poorly quantified and not used in large‐scale estimations of the blue carbon stock. Here, it is hypothesized that ecosystem age structure significantly modulates mangrove carbon stocks. We analysed a 66‐year chronosequence of the aboveground and belowground biomass and soil carbon stock of mangroves in French Guiana, and we found that in the year after forest establishment on newly formed mud banks, the aboveground, belowground and soil carbon stocks averaged 23.56 ± 7.71, 13.04 ± 3.37 and 84.26 ± 64.14 (to a depth of 1 m) Mg C/ha, respectively. The mean annual increment (MAI) in the aboveground and belowground reservoirs was 23.56 × Age^−0.52 and 13.20 × Age^−0.64 Mg C ha⁻¹ year⁻¹, respectively, and the MAI in the soil carbon reservoir was 3.00 ± 1.80 Mg C ha⁻¹ year⁻¹. Our results show that the plant carbon sink capacity declines with ecosystem age, while the soil carbon sequestration rate remains constant over many years. We suggest that global projections of the above‐ and belowground reservoirs of the carbon stock need to account for mangrove age structures, which result from historical changes in coastal morphology. Our work anticipates joint international efforts to globally quantify the multidecadal mangrove carbon balance based on the combined use of age‐based parametric equations and time series of mangrove age maps at regional scales.     

Carbon stocks in the Guinea savanna of Ghana: estimates from three protected areas

Savannas are widespread in sub‐Saharan Africa (SSA) and play a major role in the global carbon balance. Extensive quantification of savanna carbon stocks in SSA will therefore contribute to better accounting of the global carbon budget in the era of climate change. In this study, we investigated the spatial distribution of carbon stocks of different soil fractions and aboveground biomass within three forest reserves in the Guinea savanna zone of Ghana. Soil carbon stocks (SCSs) ranged from 4.80 to 12.61 Mg C/ha in surface soils (0–10 cm depth). Higher SCSs were associated with the silt +clay fraction than microaggregates and small macroaggregates in all three reserves. Relative to the dominant tree species (Vitellaria paradoxa), the highest SCSs were recorded under the sub‐canopy (SC), drip line (DL), and interspace (2 * SC + DL) zones for the Klupene, Sinsablegbinni, and Kenikeni forest reserves, respectively. The highest tree carbon stock was 60.01 Mg C/ha in Kenikeni. Sinsablegbinni had an average stock of 26.74 Mg C/ha and had the highest tree density. Average carbon capture by a single tree ranged from 0.04 to 0.34 Mg C. Aboveground grass carbon stock ranged from 0.08 to 0.47 Mg C/ha, while the belowground carbon stock ranged from 0.03 to 0.44 Mg C/ha. Accumulation of carbon in the aboveground grass biomass was greater at Klupene with low forest cover.     

Persistent anthropogenic legacies structure depth dependence of regenerating rooting systems and their functions

Biotically-mediated weathering helps to shape Earth’s surface. For example, plants expend carbon (C) to mobilize nutrients in forms whose relative abundances vary with depth. It thus is likely that trees’ nutrient acquisition strategies—their investment in rooting systems and exudates—may function differently following disturbance-induced changes in depth of rooting zones and soil nutrient stocks. These changes may persist across centuries. We test the hypothesis that plant C allocation for nutrient acquisition is depth dependent as a function of rooting system development and relative abundances of organic vs. mineral nutrient stocks. We further posit that patterns of belowground C allocation to nutrient acquisition reveal anthropogenic signatures through many decades of forest regeneration. To test this idea, we examined fine root abundances and rooting system C in organic acid exudates and exo-enzymes in tandem with depth distributions of organically- and mineral-bound P stocks. Our design permitted us to estimate C tradeoffs between organic vs. mineral nutrient benefits in paired forests with many similar aboveground traits but different ages: post-agricultural mixed-pine forests and older reference hardwoods. Fine roots were more abundant throughout the upper 2 m in reference forest soils than in regenerating stands. Rooting systems in all forests exhibited depth-dependent C allocations to nutrient acquisition reflecting relative abundances of organic vs. mineral bound P stocks. Further, organic vs. mineral stocks underwent redistribution with historic land use, producing distinct ecosystem nutritional economies. In reference forests, rooting systems are allocating C to relatively deep fine roots and low-C exudation strategies that can increase mobility of mineral-bound P stocks. Regenerating forests exhibit relatively shallower fine root distributions and more diverse exudation strategies reflecting more variable nutrient stocks. We observed these disparities in rooting systems’ depth and nutritional mechanisms even though the regenerating forests have attained aboveground biomass stocks similar to those in reference hardwood forests. These distinctions offer plausible belowground mechanisms for observations of continued C sink strength in relatively old forests, and have implications for soil C fates and soil development on timescales relevant to human lifetimes. As such, depth-dependent nutrient returns on plant C investments represent a subtle but consequential signal of the Anthropocene.

     

Carbon cycling and budget in a forested basin of southwestern Hokkaido,northern Japan

Quantification of annual carbon sequestration is very important in order to assess the function of forest ecosystems in combatting global climate change and the ecosystem responses to those changes. Annual cycling and budget of carbon in a forested basin was investigated to quantify the carbon sequestration of a cool-temperate deciduous forest ecosystem in the Horonai stream basin, Tomakomai Experimental Forest, northern Japan. Net ecosystem exchange, soil respiration, biomass increment, litterfall, soil-solution chemistry, and stream export were observed in the basin from 1999–2001 as a part of IGBP-TEMA project. We found that 258 g C m^–2 year^–1 was sequestered annually as net ecosystem exchange (NEE) in the forested basin. Discharge of carbon to the stream was 4 g C m^–2 year^–1 (about 2% of NEE) and consisted mainly of dissolved inorganic carbon (DIC). About 43% of net ecosystem productivity (NEP) was retained in the vegetation, while about 57% of NEP was sequestered in soil, suggesting that the movement of sequestered carbon from aboveground to belowground vegetation was an important process for net carbon accumulation in soil. The derived organic carbon from aboveground vegetation that moved to the soil mainly accumulated in the solid phase of the soil, with the result that the export of dissolved organic carbon to the stream was smaller than that of dissolved inorganic carbon. Our results indicated that the aboveground and belowground interaction of carbon fluxes was an important process for determining the rate and retention time of the carbon sequestration in a cool-temperate deciduous forest ecosystem in the southwestern part of Hokkaido, northern Japan.     

Carbon of Chaillu forests based on a phytosociological analysis in Republic of Congo,more than meets the eye?

The objectives were to quantify aboveground, belowground and dead wood carbon pools near Mayoko in the Chaillu massif of Republic of Congo and explore relationships between carbon storage and plant diversity of all growth forms. A total of 190 plots (25 m by 25 m) were sampled (5072 stems, 211 species) and data analysed using recommended central-African forest allometric equations. Mean stem diameter at breast height was 33.6 cm, mean basal area 47.7 m² ha⁻¹ and mean density of individuals 407 ha⁻¹. Mean aboveground carbon (AGC) ranged from 13.93–412.66 Mg C ha⁻¹, belowground carbon from 2.86–96.97 Mg C ha⁻¹ and dead wood from 0.00–7.59 Mg C ha⁻¹. The maximum AGC value recorded in a plot was 916 Mg C ha⁻¹. The analysis performed using phytosociological association as basis rather than broad vegetation type is unique. AGC values for undisturbed terra firme forest sites featured among the highest recorded for African tropical forests. Considering only tree diversity, a weak, yet significant, relationship existed between AGC and species richness, Shannon-Wiener index of diversity and Fisher's alpha. However, if diversity of all plant growth forms is considered, no relationship between carbon and plant diversity existed.     

Altitudinal analysis of carbon stocks in the Antisana páramo,Ecuadorian Andes

Aims The importance of quantifying carbon stocks in terrestrial ecosystems is crucial for determining climate change dynamics. However, the present regional assessments of carbon stocks in tropical grasslands are extrapolated to unsampled areas with a high degree of uncertainty and without considering the carbon and nitrogen composition of vegetation and soil along altitudinal ranges. This study aims to assess carbon and nitrogen concentrations in soil and vegetation, aboveground carbon stocks distribution and soil organic carbon stocks along an altitudinal range in the páramo region in the Ecuadorian Andes.Methods The vegetation inventory was conducted using 15×15 m sampling plots distributed in three altitudinal ranges. Based on the patterns exhibited by the dominant vegetation growth forms, biomass and soil were sampled to quantify the corresponding carbon and nitrogen concentrations. Subsequently, the aboveground live biomass along the páramo altitudinal range was estimated using allometric equations. Finally, soil and vegetation carbon stocks were estimated for the entire basin.Important findings Altitudinal analysis supported a potential distribution of carbon and nitrogen concentrations in soil, litter and live tissues, where higher concentrations were found in the low altitudinal range mainly for tussocks and acaulescent rosettes. Cellulose in litter showed higher concentrations at low altitudinal ranges for acaulescent rosettes and cushions only. For the same growth forms, lignin patterns in litter were higher in high altitudinal ranges. Soil texture provided complementary information: high percentage of silt was highly correlated to high soil nitrogen and carbon concentration. Tussocks were found to be responsive to altitude with their, highest aboveground carbon stocks occurring at the low altitudinal range, but cushions and acaulescent rosettes responded differently. The established relationships among soil, vegetation and altitude shown in this study must be taken into account to estimate both aboveground and soil organic carbon stocks in páramo regions—such estimates will be considerably inaccurate if these relationships are ignored.     

Carbon storage potential of Avicennia marina as influenced by soil factors in National Park Nayband,South Coast of Iran

The carbon storage potential varies according to plant species, locations, and soil parameters. This study conducted to calculate amounts of carbon storage and effects of soil factors on C storage Avicennia marina in the coastal area of Bradkhon-Mal Gonzeh in National Park Nayband, of Bushehr province. To conduct research, aboveground and belowground biomass, and a distance of 1.5 m in two depths (0–60 and 60–100 cm) in 5 sample plots in the habitat zone and control site in March 2019, samples of biomass and soil were taken. The aboveground and belowground biomass were estimated using the allometric equation. The soil factors in each sample point were done by laboratory methods. The relations between soil factors and C storage in above and below-ground biomass were determined using cluster analysis. The result showed that the amount of C storage in above and belowground biomass is 12.7 ± 1.08 and 5.7 ± 0.4 g/m², respectively. The amount of carbon stored at the first depth of the soil was more than the second depth, this is due to the expansion of roots on the surface of the soil. The most important parameters influencing soil carbon storage is electrical conductivity (EC), total neutralizing value (TNV), percentage of sand, silt and clay, organic matter and nitrogen.     

Differences in carbon stocks along an elevational gradient in tropical mountain forests of Colombia

Tropical mountain forests provide an exceptional opportunity to evaluate the patterns of variation in carbon stocks along elevational gradients that correspond to well‐defined temperature gradients. We predicted that carbon stored in live aboveground biomass, aboveground necromass, and soil components of forests on the eastern flank of the Colombian Andes would change with elevation along this gradient extending from 750 to 2,800 m above sea level. The rationale was that the corresponding change in temperature (14–26°C) would influence tree growth and decomposition of organic matter. To address this hypothesis, we examined the carbon stored in these three components using data from 20 0.25‐ha plots located along this elevational gradient. The mean total carbon stock found in the study region was 241.3 ± 37.5 Mg C/ha. Aboveground carbon stocks decreased with elevation (p = 0.001), as did necromass carbon stocks (p = 0.016). Although soil organic carbon stocks did not differ significantly along the gradient (p = 0.153), they contributed proportionately more at higher than at lower elevations, counterbalancing the opposite trends in aboveground carbon and necromass carbon stocks. As such, total carbon stocks did not vary significantly along the elevational gradient (p = 0.576).