Carbon Stocks In Tropical Forests Research Articles

Wood Basic Density in Large Trees: Impacts on Biomass Estimates in the Southwestern Brazilian Amazon

Wood basic density (WD) plays a crucial role in estimating forest biomass; moreover, improving wood-density estimates is needed to reduce uncertainties in the estimates of tropical forest biomass and carbon stocks. Understanding variations in this density along the tree trunk and its impact on biomass estimates is underexplored in the literature. In this study, the vertical variability of WD was assessed along the stems of large trees that had a diameter at breast height (DBH) ≥ 50 cm from a dense ombrophilous forest on terra firme (unflooded uplands) in Acre, Brazil. A total of 224 trees were sampled, including 20 species, classified by wood type. The average WD along the stem was determined by the ratio of oven-dry mass to saturated volume. Five models were tested, including linear and nonlinear ones, to fit equations for WD, selecting the best model. The variation among species was notable, ranging from 0.288 g cm−3 (Ceiba pentandra, L., Gaertn) to 0.825 g cm−3 (Handroanthus serratifolius, Vahl., S. Grose), with an average of 0.560 g cm−3 (±0.164, standard deviation). Significant variation was observed among individuals, such as in Schizolobium parahyba var. amazonicum (H. ex D.), which ranged from 0.305 to 0.655 g cm−3. WD was classified as low (≤0.40 g cm−3), medium (0.41–0.60 g cm−3), and high (≥0.61 g cm−3). The variability in WD along the stem differs by wood type. In trees with low-density wood, density shows irregular variation but tends to increase along the stem, whereas it decreases in species with medium- and high-density wood. The variation in WD along the stem can lead to underestimations or overestimations, not only in individual trees and species but also in total stocks when estimating forest biomass. Not considering this systematic bias results in significant errors, especially in extrapolations to vast areas, such as the Amazon.

The effect of repeated hurricanes on the age of organic carbon in humid tropical forest soil.

Increasing hurricane frequency and intensity with climate change is likely to affect soil organic carbon (C) stocks in tropical forests. We examined the cycling of C between soil pools and with depth at the Luquillo Experimental Forest in Puerto Rico in soils over a 30-year period that spanned repeated hurricanes. We used a nonlinear matrix model of soil C pools and fluxes ("soilR") and constrained the parameters with soil and litter survey data. Soil chemistry and stable and radiocarbon isotopes were measured from three soil depths across a topographic gradient in 1988 and 2018. Our results suggest that pulses and subsequent reduction of inputs caused by severe hurricanes in 1989, 1998, and two in 2017 led to faster mean transit times of soil C in 0-10 cm and 35-60 cm depths relative to a modeled control soil with constant inputs over the 30-year period. Between 1988 and 2018, the occluded C stock increased and δ13C in all pools decreased, while changes in particulate and mineral-associated C were undetectable. The differences between 1988 and 2018 suggest that hurricane disturbance results in a dilution of the occluded light C pool with an influx of young, debris-deposited C, and possible microbial scavenging of old and young C in the particulate and mineral-associated pools. These effects led to a younger total soil C pool with faster mean transit times. Our results suggest that the increasing frequency of intense hurricanes will speed up rates of C cycling in tropical forests, making soil C more sensitive to future tropical forest stressors.

Algorithm Theoretical Basis Document for GEDI Footprint Aboveground Biomass Density

AbstractThe Global Ecosystem Dynamics Investigation (GEDI) lidar is a multibeam laser altimeter on the International Space Station (ISS). GEDI is the first spaceborne instrument designed to measure vegetation height and to quantify aboveground carbon stocks in temperate and tropical forests and woodlands. This document describes the algorithm theoretical basis underpinning the development of the GEDI Level‐4A (GEDI04_A) footprint aboveground biomass density (AGBD) data product. The GEDI04_A data product contains estimates of AGBD for individual GEDI footprints and associated prediction intervals. The algorithm uses GEDI02_A relative height metrics and 13 linear models to predict AGBD in 32 combinations of plant functional type and world region within the observation limits of the ISS. GEDI04_A models for the release 1 and release 2 data products were developed using 8,587 quality‐filtered simulated GEDI waveforms associated with field estimates of AGBD in 21 countries. Although this is the most geographically comprehensive data available for the development of AGBD models using lidar remote sensing, important regions are underrepresented, including the forests of continental Asia, deciduous broadleaf forests and savannas of the dry tropics, and evergreen broadleaf forests north of Australia. We describe the scientific and statistical assumptions required to develop globally representative estimates of AGBD using GEDI lidar, including generalization beyond training data, and exclusion of GEDI02_A observations that do not meet requirements of the GEDI04_A algorithm. The footprint‐level predictions generated by this process provide globally comprehensive estimates of AGBD. These footprint‐level predictions are a prerequisite for the GEDI04_B gridded AGBD data product.

Selective logging that occurred decades ago is still impacting aboveground biomass and tree assemblage structure in Brazilian semi-deciduous seasonal Atlantic forest fragments

The majority of tropical forests in the world have undergone or are still undergoing selective logging. This human disturbance is among the actions that most affect the dynamics of the carbon stocks of tropical forests and also the vegetation structure, richness, and species composition. One of the most widely used approaches to understand forest responses to this disturbance has been to compare them with other undisturbed forests in the given region. Here, we measure the effects of the selective logging history on the aboveground biomass, tree abundance, basal area, and wood density in four Brazilian Atlantic Forest fragments logged once, 35–45 years before the current sampling. We used two unlogged forest fragments as reference ecosystems. We found 40% less aboveground biomass (AGB) and 31% lower basal area in logged than in unlogged forest fragments. Large trees (trees with a diameter greater than 50 cm) were strongly affected by selective logging, showing AGB, basal area, mean wood density and tree abundance values 59%, 52%, and 46%, respectively, lower in logged forest fragments. We found an increase in the abundance of softwood, early-successional species in logged forests, where 45% of the AGB accumulated was due to only two species (Astronium graveolens Jacq and Gallesia integrifolia (Spreng.) Harms). The opposite was observed in unlogged forest fragments, where two late successional hardwood species (Aspidosperma polyneuron Müll.Arg and Holocalyx balansae Micheli) accumulated 38% of the AGB. Our findings indicate that even decades after the last logging event semi-deciduous seasonal Atlantic Forest fragments with a selective logging history may present different AGB, structure, and functional composition from the expected pattern for old-growth forests in the given region.

Biological, structural and functional responses of tropical forests to environmental factors

As compared to temperate and boreal forests, the majority of tropical forests are biodiverse, structurally-complex and high-functioning ecosystems, yet their potential attributes are vulnerable to anthropogenic disturbances and environmental factors. Here, we hypothesize that the biological, structural and functional attributes of tropical forests respond to water-related climatic and soil nutrient-related factors. Thus, we quantified 27 forest attributes and 20 environmental factors across 189 plots of Sri Lankan tropical forests. Our results suggest that environmental conditions were characterized by both water-related and temperature-related factors, and as such, both coarse-textured and compacted-structured soils determined soil conditions. Forest conditions were characterized by high species-functional diversity, structural complexity and aboveground biomass-related functions. We found strong positive effects of water-related climatic factors (particularly mean annual precipitation) followed by temperature-related climatic factors (i.e., growing degree days) but negligible positive to negative effects of textured-related (i.e., gravel contents) and nutrient-related (i.e., bulk density) soil factors on most of the biological, structural and functional attributes. Overall the biodiversity and carbon stocks of Sri Lankan tropical forests are likely to increase with water-energy balance and improved soil conditions, and thus, studied forests could offset a substantial quantity of anthropogenic carbon emissions to achieve carbon neutrality which can have both regional and global significance if protected from anthropogenic disturbances. Broadly, this study suggests that conservation practices should consider multiple environmental and biotic attributes of the tropical forests during forest management which can have a win-win situation for biodiversity conservation and climate change mitigation.

Increasing liana biomass and carbon stocks in tropical dry evergreen forests of southern India

Tropical forests act as a great carbon reservoir covering about 30% of the global carbon content, however, structural alteration of these forests caused by forest disturbances adversely affects the carbon cycle. One such structural change happening in these tropical forests is the increasing dominance of lianas (woody climbers). Among various tropical forest types, lianas are an integral constituent of the tropical dry evergreen forests (TDEFs) found in peninsular India. A re-inventory of lianas was carried out to observe temporal changes in basal area and carbon stock in two 1-ha permanent plots of two disturbed tropical dry evergreen forest sites (TDEF; Oorani -OR and Puthupet - PP) over a 19-year interval (2001-2020). The total basal area in OR and PP increased respectively by 2.26 m2 ha-1 and 0.93 m2 ha-1. The total biomass and the carbon stock in OR and PP increased by 82% and 51% respectively. The dominant species Strychnos lenticellata showed an increase in its basal area by three-fold in OR, whereas, in PP, a marginal increase of 4% was observed. The lower diameter class (1-6 cm) showed an increase in basal area in OR and PP by 101% and 16% respectively. The mid-diameter class (6-11 cm) was the top contributor of the total biomass/carbon in both OR and PP in the latest re-inventory (2020). The present results show that lianas, although known to negatively affect the forest biomass/carbon stock, play an important role in carbon sequestration, thus providing insights into their ecological importance which will certainly be useful in proposing strategies for the conservation of this forest type dominated by lianas.

A global evaluation of the effectiveness of voluntary REDD+ projects at reducing deforestation and degradation in the moist tropics.

Reducing emissions from deforestation and forest degradation (REDD+) projects aim to contribute to climate change mitigation by protecting and enhancing carbon stocks in tropical forests, but there have been no systematic global evaluations of their impact. We used a new data set for tropical humid forests and a standardized evaluation approach (based on pixel matching) to quantify the performance of a representative sample of 40 voluntary REDD+ projects in 9 countries certified under the Verified Carbon Standard (VCS). In the first 5 years of implementation, deforestation within project areas was reduced by 47% (95% confidence interval [CI]: 24-68) compared with matched counterfactual pixels, and degradation rates were 58% lower (95% CI: 49-63). Reductions were small in absolute terms but greater in sites located in high-deforestation settings and did not appear to be substantially undermined by leakage activities in forested areas within 10km of project boundaries. At the 26th Conference of the Parties of the United Nations Framework Convention on Climate Change, the international community renewed its commitment to tackling tropical deforestation as a nature-based solution to climate change. Our results indicate that incentivizing forest conservation through voluntary site-based projects can slow tropical deforestation and highlight the particular importance of prioritizing financing for areas at greater risk of deforestation.

Forest structure and carbon stock of Suan Phueng Nature Education Park in Ratchaburi Province, Western Thailand

Abstract. Chanlabut U, Nahok B. 2022. Forest structure and carbon stock of Suan Phueng Nature Education Park in Ratchaburi Province, Western Thailand. Biodiversitas 23: 4314-4321. Forests play an important role in the global carbon budget. Yet, carbon stocks in tropical forests are uncertain depending on many factors. This study aims to study forest structures and carbon stocks in Suan Phueng Nature Education Park, Ratchaburi, Western Thailand. In 12 plots of 20 × 20 m, an inventory of trees ? 4.5 cm diameter at breast height (DBH) was carried out. Soil samples were also collected in sampling plots. To describe forest structures, ecological parameters were analyzed (IVI, diversity indices, basal area, and DBH size classes). Forest carbon stocks were calculated based on biomass and soils. Allometric equations were used to calculate aboveground biomass and converse to carbon stock. The soil carbon was analyzed using the wet oxidation method. The result showed that the lower montane forest (493.74 ± 90.20 Mg C ha-1) had the highest forest carbon stock, followed by the dry evergreen + mixed deciduous forest (203.83 ± 82.74 Mg C ha-1), and mixed deciduous forest (145.46 ± 47.90 Mg C ha–1). In the three forests, there were atotal of 637 trees belonging to 70 species in 29 families. Shannon’s diversity index was 3.59 with a range of 2.17-3.21, indicating a moderate to high diversity. Tree density was 1,137.50 stems ha-1 with a range of 737.50-1,581.25 stems ha-1. The basal area had a range of 5.82-11.11 m2 ha-1. The DBH classes exhibited J-shaped distribution. The large trees (?71 cm) had a greater aboveground carbon stock, despite their lower density. This indicates their importance as carbon sinks in the forest. This study highlights that the forests in Suan Phueng Nature Education Park not only have the potential to be carbon stocks but also contain a high diversity of tree species.

Coarse woody debris density and carbon concentration by decay classes in mixed montane wet tropical forests

AbstractThe role of coarse woody debris (CWD) in the global carbon (C) cycle is growing under increasing tree mortality driven by climate variability and disturbances. Quantifying C in CWD critically depends on accurate estimates of CWD density and C concentration in CWD. This study considered the main decomposition pathways (the proportions of CWD decomposed by fungi vs. invertebrates; fungal decay types) and the relationships between decay class, wood density, moisture, and C content of CWD in old‐growth mixed monsoon montane tropical forests in Vietnam based on the inventory of 359 CWD pieces. The bulk density of wood of the 1st, 2nd, 3rd, 4th, and 5th decay classes averaged 0.56, 0.49, 0.37, 0.28, and 0.15 g cm−3, respectively. The density reduction across decay classes did not significantly differ for snags, stumps, branches, leaning, and lying logs. Wood density was negatively related to wood moisture. The wood mass loss averaged 0%, 20%, 37%, 54%, and 74% in the CWD of the 1st, 2nd, 3rd, 4th, and 5th decay classes, respectively. Signs of invertebrate activity were recorded on 3% of CWD pieces. Among CWD samples with identifiable decay type, 88% were decomposed by white‐rot, 8% were decomposed as brown‐rot, and 4% of pieces contained both white‐ and brown‐rot patches. The mean C concentration in wood was 46.5%. It did not change with decay class. Our research provides an empirical basis for future inventories of CWD carbon stocks in Asian montane tropical mixed forests.

Relationship between forest biodiversity attributes and potential carbon stocks in dry tropical reserve forests of Assam, northeast India

Relationship between forest biodiversity attributes and potential carbon stocks in dry tropical reserve forests of Assam, northeast India

Tropical tree allometry and crown allocation, and their relationship with species traits in central Africa

Common allometric patterns have been reported across the tropics and good performance on independent data was retrieved for the most recent pantropical model predicting tree aboveground biomass (AGB) from stem diameter, wood density and total height. General models are undoubtedly useful for the estimation and monitoring of biomass and carbon stocks in tropical forests, however specific allometry, allocation, and traits, are at the core of many models of vegetation dynamics, and there is lack of such information for some regions and species. In this study, we specifically evaluated how size-dependent changes in above-ground biomass and biomass allocation to crown relate to other allometric and life-history traits for tropical tree species. We gathered destructive data available in eight terra firme forest sites across central Africa and the combined dataset consisted of 1,023 trees belonging to 54 tropical tree species phylogenetically dispersed, with only two congeneric species. A huge body of field and laboratory measurements was used for computing AGB and crown mass ratio (CMR) at the tree level, and to derive key allometric traits at the species level. For the latter, species-specific relationships between tree diameter and total height, crown exposure to light, wood density, and bark thickness were fitted for 50 species. Our results show interspecific variation in the relationships relating tree diameter to both AGB and CMR, and including species traits in a multi-specific AGB model confirmed that interspecific variation in biomass allometry is primarily determined by species wood density. We also showed that the allocation of biomass to crown increases linearly with tree diameter for most species, and that interspecific variation in the CMR model is associated with the species dispersal mode and maximum height. Trait covariations among our set of tropical tree species widespread and/or locally abundant in central Africa, revealed a continuum between large-statured species, which tended to be light-demanding, deciduous and wind-dispersed, and species with opposite attributes. Information on allometry, allocation, and traits provided here could further be used in comparative ecology and for parameterizing dynamic and succession models. Also importantly, the species-specific AGB models fitted for major tree species, including most timber species of central Africa, will help improve biomass estimates.

Carbon balance of tropical peat forests at different fire history and implications for carbon emissions.

Accurate assessment of tropical peat forest carbon stocks and impact of fires on carbon pools is required to determine the magnitude of emissions to the atmosphere and to support emissions reduction policies. We assessed total aboveground carbon (AGC) in biomass pools including trees, shrubs, deadwood, litter and char, and peat carbon to develop empirical estimates of peat swamp forest carbon stocks in response to fire and disturbance. In contrast to the common assumption that peat fires combust all AGC, we observed that about half of undisturbed forest AGC, equivalent to about 70Mg C ha-1, remains after one or two recent fires - mainly in dead trees, woody debris and pyrogenic carbon. Both recently burnt and repeatedly burnt peat forests store similar amounts of carbon in the top 10cm of peat when compared with undisturbed forests (70Mg C ha-1), mainly due to increased peat bulk density after fires that compensates for their lower peat C%. The proportion of fuel mass consumed in fire, or combustion factor (CF), is required to make accurate estimates of peat fire emissions for both AGC and peat carbon. This study estimated a CF for AGC (CFAGC) of 0.56, comparable to the default value of the Intergovernmental Panel on Climate Change (IPCC). This study estimated a varying CF for peat (CFPEAT) that ranged from 0.4 to 0.68 as depth of burn increased. This revised CFPEAT is one third to one half of the IPCC default value of 1.0. The current assumption of complete combustion of peat (CF=1.0) is widely acknowledged in the literature as oversimplification and is not supported by our field observations or data. This study provides novel empirical data to improve estimates of peat forests carbon stocks and emissions from tropical peat fires.

Evaluation of allometries for estimating above-ground biomass using airborne LiDAR data in tropical montane forest of Northern Borneo

Tropical forests play a crucial component of the terrestrial carbon pool and estimate of above-ground biomass (AGB) with high accuracy is important in quantifying tropical forest carbon stocks. There are several allometries available for estimating tropical forest tree AGB using field measurements, the choice of allometric equation is a decisive factor that can influence the AGB estimation accuracy. This study examined the use of allometric equations to accurately estimate AGB using airborne LiDAR data. The LiDAR data of Ulu Padas area was acquired using Optech Orion C200. 56 field plots were established to collect data on diameter at breast height, tree height and tree species. Field AGB was calculated from allometric equations of Yamakura et al. (1986), Basuki et al. (2009), Chave et al. (2005) and Chave et al. (2014). All LiDAR-derived height metrics and variables were correlated with field AGB (R: 0.30-0.88). Based on stepwise multiple regression analysis, Chave et al. (2014) allometry had highest model R2, explaining 81% of the variance of the field AGB. In short, allometry that includes wood density should be used in LiDAR applications on tropical forest AGB estimation.

Long-term thermal sensitivity of Earth's tropical forests.

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (-9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth's climate.

Thermal sensitivity of tropical trees

Tropical Forests A key uncertainty in climate change models is the thermal sensitivity of tropical forests and how this value might influence carbon fluxes. Sullivan et al. measured carbon stocks and fluxes in permanent forest plots distributed globally. This synthesis of plot networks across climatic and biogeographic gradients shows that forest thermal sensitivity is dominated by high daytime temperatures. This extreme condition depresses growth rates and shortens the time that carbon resides in the ecosystem by killing trees under hot, dry conditions. The effect of temperature is worse above 32°C, and a greater magnitude of climate change thus risks greater loss of tropical forest carbon stocks. Nevertheless, forest carbon stocks are likely to remain higher under moderate climate change if they are protected from direct impacts such as clearance, logging, or fires. Science , this issue p. [869][1] [1]: /lookup/doi/10.1126/science.aaw7578

Biomasse et stocks de carbone en Afrique centrale : importance de l’allométrie des arbres

Quantifier les stocks de biomasse et de carbone dans les forêts tropicales est essentiel pour la mise en œuvre des stratégies d’atténuation des changements climatiques, et notamment le mécanisme de réduction des émissions dues à la déforestation et la dégradation des forêts. Les scientifiques s’accordent aujourd’hui à utiliser une équation allométrique de biomasse générale, combinée à une allométrie hauteur-diamètre ajustée sur des données locales non destructives. Or, l’allométrie des arbres varie entre les espèces et stratégies fonctionnelles d’une part, entre les types de forêts et conditions du milieu d’autre part. L’objectif de cette thèse de doctorat était d’étudier les variations de l’allométrie des arbres entre espèces coexistantes, et entre sites et types de forêts, en vue d’améliorer les estimations de la biomasse et des stocks de carbone en Afrique centrale. Les variations des allométries hauteur-diamètre et houppier-diamètre ont été rapportées pour les 45 espèces d’arbres coexistantes d’un site représentatif des forêts semi-décidues à Celtis du nord du Congo. Les relations entre les traits architecturaux dérivés à partir des allométries spécifiques aux espèces et les traits fonctionnels ont mis en évidence un continuum d’espèces entre les espèces de grande taille dominant la canopée et les espèces de petite taille dominant le sous-bois. Les espèces d’arbres de grande taille étaient exigeantes en lumière, dispersées par le vent, décidues avec une large contribution à la biomasse forestière, alors que les espèces d’arbres de petite taille étaient tolérantes à l’ombrage, dispersées par les animaux, sempervirentes et plus abondantes en densité de tiges. Les variations des allométries hauteur-diamètre et houppier-diamètre ont été également montrées entre les types de forêts en Afrique centrale. Ces tendances étaient en outre confirmées pour les espèces communes entre les types de forêts, suggérant un contrôle environnemental sur les variations de l’allométrie des arbres. Des attributs architecturaux dérivés des allométries spécifiques aux sites, en plus des attributs plus classiques de structure et de composition, ont pu être dérivés et reliés aux variations spatiales de la biomasse et des stocks de carbone. Cette thèse de doctorat a fourni de nouvelles données pour les futures cartes de biomasse dans le cadre du suivi du carbone forestier en Afrique centrale.

Understanding the importance of primary tropical forest protection as a mitigation strategy

Given the short time-frame to limit global warming, and the current emissions gap, it is critical to prioritise mitigation actions. To date, scant attention has been paid to the mitigation benefits of primary forest protection. We estimated tropical forest ecosystem carbon stocks and flows. The ecosystem carbon stock of primary tropical forests is estimated at 141–159 Pg C (billion tonnes of carbon) which is some 49–53% of all tropical forest carbon, the living biomass component of which alone is 91–103% of the remaining carbon budget to limit global warming to below 1.5 degrees above pre-industrial levels. Furthermore, tropical forests have ongoing sequestration rates 0.47–1.3 Pg C yr−1, equivalent to 8–13% of annual global anthropogenic CO2 (carbon dioxide) emissions. We examined three main forest-based strategies used in the land sector—halting deforestation, increasing forest restoration and improving the sustainable management of production forests. The mitigation benefits of primary forest protection are contingent upon how degradation is defined and accounted for, while those from restoration also depend on how restoration is understood and applied. Through proforestation, reduced carbon stocks in secondary forests can regrow to their natural carbon carrying capacity or primary forest state. We evaluated published data from studies comparing logged and unlogged forests. On average, primary forests store around 35% more carbon. While comparisons are confounded by a range of factors, reported biomass carbon recovery rates were from 40 to 100+ years. There is a substantive portfolio of forest-based mitigation actions and interventions available to policy and decision-makers, depending on national circumstances, in addition to SFM and plantation focused approaches, that can be grouped into four main strategies: protection; proforestation, reforestation and restoration; reform of guidelines, accounting rules and default values; landscape conservation planning. Given the emissions gap, mitigation strategies that merely reduce the rate of emissions against historic or projected reference levels are insufficient. Mitigation strategies are needed that explicitly avoid emissions where possible as well as enabling ongoing sequestration.

Variation in tree biomass and carbon stocks in three tropical dry deciduous forest types of Madhya Pradesh, India

Variation in tree biomass and carbon (C) stocks in tropical dry forests is important at both regional and global scale to know their contribution in global C cycle. In Indian tropical forests, the information on variation in tree biomass and C stocks at forest type level is scarce and fragmented. In the present study, three tropical dry deciduous forest types: dry deciduous teak forest (DDTF), dry deciduous mixed forest (DDMF) and Boswellia forest (BF) have been selected in Madhya Pradesh, Central India, to assess the biomass and C stocks. The total tree biomass (aboveground + belowground) ranged from 70.4 (DDTF) to 296.6 (BF) Mg/ha with a mean of 184.1 Mg/ha, whereas the tree C ranged from 35.3 (DDTF) to 140.9 (BF) Mg C/ha with a mean value of 87.4 Mg C/ha. The greatest biomass (220.4 Mg/ha) and C stocks (104.7 Mg C/ha) have been observed in BF type, whereas the least biomass (160.9 Mg/ha) and C (76.4 Mg C/ha) have been observed in DDTF type, with the mean biomass and C stock values of 184.1 Mg/ha and 87.4 Mg C/ha, respectively. In both DDTF and DDMF types, Tectona grandis contributed 76.5 and 26.4% of C, whereas in BF type, Boswellia serrata contributed 73.6% of C to the total C stock. A significant positive (R2 = 0.951; p < 0.01) relationship has been observed between basal area and tree C stock. The present study would improve our understanding of C stocks present in these forest types and could be used to enhance the C sequestration potential through conservation, monitoring and management of such forests.

Tropical forest soil carbon stocks do not increase despite 15 years of doubled litter inputs

Soil organic carbon (SOC) dynamics represent a persisting uncertainty in our understanding of the global carbon cycle. SOC storage is strongly linked to plant inputs via the formation of soil organic matter, but soil geochemistry also plays a critical role. In tropical soils with rapid SOC turnover, the association of organic matter with soil minerals is particularly important for stabilising SOC but projected increases in tropical forest productivity could trigger feedbacks that stimulate the release of stored SOC. Here, we demonstrate limited additional SOC storage after 13–15 years of experimentally doubled aboveground litter inputs in a lowland tropical forest. We combined biological, physical, and chemical methods to characterise SOC along a gradient of bioavailability. After 13 years of monthly litter addition treatments, most of the additional SOC was readily bioavailable and we observed no increase in mineral-associated SOC. Importantly, SOC with weak association to soil minerals declined in response to long-term litter addition, suggesting that increased plant inputs could modify the formation of organo-mineral complexes in tropical soils. Hence, we demonstrate the limited capacity of tropical soils to sequester additional C inputs and provide insights into potential underlying mechanisms.

Monitoring tropical forest carbon stocks and emissions using Planet satellite data

Tropical forests are crucial for mitigating climate change, but many forests continue to be driven from carbon sinks to sources through human activities. To support more sustainable forest uses, we need to measure and monitor carbon stocks and emissions at high spatial and temporal resolution. We developed the first large-scale very high-resolution map of aboveground carbon stocks and emissions for the country of Peru by combining 6.7 million hectares of airborne LiDAR measurements of top-of-canopy height with thousands of Planet Dove satellite images into a random forest machine learning regression workflow, obtaining an R2 of 0.70 and RMSE of 25.38 Mg C ha−1 for the nationwide estimation of aboveground carbon density (ACD). The diverse ecosystems of Peru harbor 6.928 Pg C, of which only 2.9 Pg C are found in protected areas or their buffers. We found significant carbon emissions between 2012 and 2017 in areas aggressively affected by oil palm and cacao plantations, agricultural and urban expansions or illegal gold mining. Creating such a cost-effective and spatially explicit indicators of aboveground carbon stocks and emissions for tropical countries will serve as a transformative tool to quantify the climate change mitigation services that forests provide.