Tree Carbon Research Articles

Tree Diversity, Carbon Stock, and Factors Influencing the Adoption of Agroforestry Systems in Dugda District, Ethiopia

The Dugda district's, Ethiopia farmers have employed the agroforestry system for millennia. However, farmers usually ignore the agroforestry system in favor of an intensive farming that grows a monocrop because they are unaware of its conservation and climate change mitigation benefits. This study's goal was to assess the impact of agroforestry on the plant diversity, carbon stock and to identify factors governing its adoption. From a total of 242 sampling points, tree species identification, height and diameter at breast height measurements were all done simultaneously. Complete measurements were taken in the home garden, 50 m x 100 m, 10 m x 10 m, and 10 m x 5 m quadrat were used for farmland, woodlot and grazing land, and line planting, respectively. From 0 to 30 cm depths, at each corner and in the middle, composite soil samples were collected from 50 sites (25 in agroforestry adopters and 25 in non-adopter). The outcome demonstrates that adopter sites store more carbon in their biomass and soil than the non-adopter sites. The one-way ANOVA and Fisher's LSD test findings revealed a significant difference in the mean biomass between adopters' and non-adopters sites. The highest plant diversity was recorded at the adopter site (H'), 2.25, while the maximum diversity (H'), at the non-adopter site was 1.95. Age, education, and family size are factors influencing farmers’ decision to adopt agroforestry practices. The results of the study showed how agroforestry reduces climate change and protects biodiversity. Therefore, encouraging non-adopters to engage in agroforestry practices is essential.

Impacts of the US southeast wood pellet industry on local forest carbon stocks

We assessed the net impacts of a wood-dependent pellet industry of global importance on contemporaneous local forest carbon component pools (live trees, standing-dead trees, soils) and total stocks. We conducted post-matched difference-in-differences analyses of forest inventory data between 2000 and 2019 to infer industrial concurrent and lagged effects in the US coastal southeast. Results point to contemporaneous carbon neutrality. We found net incremental effects on carbon pools within live trees, and no net effects on standing-dead tree nor soil pools. However, we found concurrent lower carbon levels in soils, mixed effects associated with increased procurement pressures and large mill pelletization capacity, and possible spillover effects on standing-dead tree carbon pools beyond commercial procurement distances. There is robust evidence that although some trade-offs between carbon pools exist, the wood pellet industry in this particular context and period has met the overall condition of forest carbon neutrality.

Effects of nitrogen deposition on carbon allocation between wood and leaves in temperate forests

Societal Impact StatementIncreasing atmospheric nitrogen (N) deposition represents a major global change factor, but its long‐term effect on tree growth and carbon (C) sequestration remains uncertain. Our manipulation experiment and meta‐analysis reveal that N deposition in temperate and boreal forests promoted tree growth and the allocation of more C into wood than into leaves in China and worldwide. Thus, N deposition may increase forest C sequestration through enhanced wood production and distribution of C into stable sinks. In the context of achieving “Carbon Neutrality,” understanding how N deposition affect long‐term forest C sinks will help us with mitigation strategies under climate change.Summary Increased nitrogen (N) deposition is driving many temperate and boreal forests in the Northern Hemisphere towards N saturation. However, it is uncertain how long‐term N deposition affects tree growth and carbon (C) allocation in these forests. To investigate this, we treated temperate larch and mixed forests in northeastern China with N additions for 8 years. In addition, we collected data from 25 N‐addition experiments in temperate and boreal forests worldwide to reveal the overall effects of N on tree growth and C allocation. Nitrogen additions significantly promoted total biomass increment by 24% in both study forests, with on average additional 8 kg C per kg N gain into woody biomass over the study period. Nitrogen additions increased the ratio of woody biomass increment to foliage litterfall production in the larch forest (by 34%). Literature data analysis also revealed greater N promotion on wood (24%) over foliage (9%) production. However, the positive effect on foliage diminished over time. These results combined imply that N deposition may promote tree growth in temperate and boreal regions and drive proportionally more photosynthate allocation into wood than leaves, thus may enhance forest C sequestration in the long run.

Physiological traits and response strategies of four subtropical tree species exposed to drought

World-wide, forests are experiencing drought-induced mortality. However, physiological adaptation to drought is highly variable, which may lead to differential mortality patterns and alter community structure. In this study, saplings of four common tree species ( Ormosia pinnata , Dalbergia odorifera , Castanopsis fissa and Michelia macclurei ) grown in subtropical plantations in southern China were subjected to average rainfall and three drought treatments, consisting of low (25% rainfall reduction), moderate (50% rainfall reduction) and high (75% rainfall reduction) drought. To investigate their drought response strategies and select tree species with higher drought tolerance, we examined plant traits, including tree growth, stomatal regulation, water relations, carbon dynamics and morphology, that might contribute to drought tolerance. We found that O. pinnata adapted to drought by decreasing turgor loss point (TLP) and increasing leaf dry matter content and leaf mass per area (LMA). D. odorifera exhibited low leaf minimum conductance and high LMA as the key drought traits to reduce water loss. C. fissa was slowest to initiate stomatal closure but completed stomatal closure more rapidly than the other species. Drought reduced light-saturated photosynthetic rates (A sat ) for O. pinnata , D. odorifera and C. fissa primarily due to declining stomatal conductance (g s ), with lesser limitations due to the biochemical capacity of Rubisco carboxylation (V cmax ) and electron transport (J max ). M. macclurei was the first species to close stomata. Drought did not affect A sat for M. macclurei due to stable photosynthetic biochemical processes; however, V cmax regulation of A sat increased with drought intensity. There was trait variation in the capacity of study trees to tolerate drought, with M. macclurei exhibiting the highest capacity to tolerate drought due to key stomatal (earlier stomatal closure) and hydraulic (lower TLP) traits reducing plant water loss with progressive drought stress. • Selecting species with morphological and physiological traits that confer high drought tolerance and resistance will be critical for designing and managing plantations. • M. macclurei might be the best adapted plantation tree for growth in future drier climates. • M. macclurei exhibited high drought avoidance and resistance, and maintained photosynthesis.

Can seasonal fire management reduce the risk of carbon loss from wildfires in a protected Guinea savanna?

AbstractFire is fundamental to the functioning of tropical savannas and routinely used as a management tool. Shifting prescribed burning from later to earlier in the growing season has the potential to reduce greenhouse gas emissions. However, large uncertainties surround the impact of seasonal burning on longer term plant and soil carbon sequestration. In this study, we quantify ecosystem carbon storage across burn seasons and histories in a wet‐to‐mesic Guinea tropical savanna in Mole National Park, Ghana. Aboveground (plant and litter) and belowground (soil plus roots) carbon storage was quantified across four burning seasons and histories: recent (<3 years) early‐season burns, recent late‐season burns, old (>4 years) late‐season burns, and long‐unburned (>15 years) sites. We found that recent late‐season burns significantly lowered belowground carbon storage to a depth of 17 cm compared with all other burn seasons and histories. Belowground carbon was 1.2 kg C m−2, or 27% lower, for recent late‐season burns compared with prescribed early‐season burns. However, in older late‐season burns sites, belowground carbon “recovered” after 4–13 burn years to comparable storage as long‐unburned and early‐season burn sites. For most aboveground carbon pools, there was no significant difference in carbon storage across burn seasons and histories, except higher aboveground tree carbon in long‐unburned sites. We suggest that observed changes in belowground carbon are likely due to the turnover and production of root carbon. Prescribed early‐season burning is promoted to reduce greenhouse gas emissions and our findings affirm that early‐season burning has limited impact on plant and soil carbon stocks compared with long‐unburned sites. While early‐season burning regimes will have some patches that become late‐season wildfires, our results suggest on balance early‐season burning regimes are a low‐risk land management practice in reducing plant and soil carbon storage losses and sustaining a patch‐mosaicked landscape with multiple other ecosystem service benefits for savannas.

The analysis of carbon carburizing of ST 60 steel with 80 mesh due to hardness and microstructure

ST 60 steel is a steel with a medium carbon content of about 0.56% by weight. The process will affect the amount of carbon that will be diffused on the surface when the carburizing process is carried out. Different types of carbon from materials and finer carbon grains, it is hoped that carbon diffusion will easily occur. In this study, carbon grains were made with a mesh size of 80, from variations of coal, coconut shell carbon, mangrove tree carbon to microstructure and hardness in ST60 steel material. The method carried out is to heat the ST 60 steel which is inserted in a pack of carbon powder until 900 °C is held for 60 minutes. After that, room temperature cooling is carried out so that carbon atoms are still diffused until the temperature is completed. The tests carried out microstructure (SEM) on raw materials formed pearlite and ferrite phases, after pack carburizing the phase formed pearlite, ferrite and coated by graphite from carbon atoms caused the hardness of the specimen to increase in the pearlite phase exposed to carbon. The results of the Rockwell Hardness test on raw material 52.3 HRA after the pack carburizing process, the hardness of the material has increased which is found in coal carbon of 62.2 HRA, coconut shell carbon of 64.8 HRA and mangrove carbon of 60.7 HRA from the test. The chemical composition of the results obtained in the raw material condition of 0.404 when in pack carburizing increased each material’s coal carbon by 0.829, coconut shell carbon by 0.88, mangrove carbon by 0.76. The largest intake of carbon when pack carburizing compared to the largest is in the pack carburizing with coconut shell charcoal.

Tree biomass and carbon stock in subtropical Sal forest of Central Himalaya, India

Tree biomass and carbon stock in subtropical Sal forest of Central Himalaya, India

Tree biomass, carbon stock characteristics and ground beetles (Coleoptera: Carabidae) diversity in the Uzungwa Scarp Forest Nature Reserve, Tanzania.

Reducing carbon emission from Deforestation and forest Degradation (REDD+) has drawn attention and remain one of the main options for climate change mitigation. However, the extent to which conservation for carbon may enhance biodiversity conservation in both disturbed and relatively undisturbed (control) environment remain unclear in most forest types. The extent to which anthropogenic disturbances affect carbon stock and ground beetle diversity is also far from clear. This paper addressed these knowledge gaps using data based on ground beetles, carbon stock in live trees and tree species sampled in Uzungwa Scarp Nature Forest Reserve (USNFR). All trees with a diameter at breast height (DBH) ≥ 5 cm were measured for height and DBH in twelve clusters of 1 ha in size. In the same clusters, ground beetles were sampled using pitfall traps, active night search and active day search. The species diversity of ground beetles differed significantly between control sites and disturbed sites (p < 0.05). The mean total biomass and carbon stock in live trees were high in disturbed sites (323.72 t/ha) when compared to control sites (289.72 t/ha) but the difference was not statistically significant (U = 14, p > 0.05). Carbon in live trees and ground beetle diversity showed a weak positive correlation, while richness and abundance showed weak negative in control sites. Results show that REDD+ related activities in a tropical forest may enhance ground beetle diversity and carbon stock if ground beetles conservation is explicitly taken into account. Thus forest conservation planning that pursues both carbon storage and ground-dwelling invertebrate diversity is recommended.

Crop Load Management in Nashi Pear—A Review

Most nashi cultivars require heavy thinning, and this has traditionally been performed by the time and labour-intensive practice of hand thinning. Crop load management is a key cost driver for nashi production, but there are limited cost-effective options available for nashi growers compared to other pome fruit, especially apples and, to a lesser extent, European pears. There is, however, potential to adapt some of the thinning tools and techniques used in apples and European pears to reduce the labour requirements and high cost of thinning in nashi, thus improving industry profitability. Several chemical thinning agents have potential for nashi, and an understanding of the optimal application rates, times and weather conditions for each chemical, as well as the conditions/factors that impact the tree carbon balance, will improve the predictability of chemical thinning. However, it is difficult to target specific flowers/fruitlets within a cluster with chemicals, and the flowers that produce the preferred fruit shape and size are in the middle of the flower cluster. Mechanical thinning during the flowering period with either Darwin or BAUM-style string thinners has potential, particularly as these devices can be used as early as flower emergence. As for chemical thinning, the issue of non-selectivity needs to be addressed; however, the development of mechatronic systems should overcome most problems that occur with the currently available mechanical thinners. Shading at critical times is an avenue that could be explored further to ascertain the critical stage when developing fruit are susceptible to enable the determination of the optimal timing and duration of shading. Targeted pruning and bud thinning during the dormant winter period to reduce the floral bud numbers is a valuable option for the precise placement of fruit in optimal positions and to set up the required number of clusters. This review highlighted several tools/techniques that, with further work, can be incorporated into a systematic approach to crop load management in nashi while reducing the risk and cost.

Carbon Stocks Assessment in a Disturbed and Undisturbed Mangrove Forest in Ghana

Mangroves and other blue carbon ecosystems have long been recognised for their carbon sink function, yet the organic carbon stocks of mangroves in many countries in Africa remain to be assessed. This study evaluates the impact of traditional forest conservation on long-term carbon sequestration in a non-degraded (Amanzule) and a degraded (Kakum) mangrove forest system in Ghana (West Africa). The amount of carbon stored in mangrove trees was estimated from diameter-based allometric equations. Tree (above- and below-ground) carbon was ~34-fold higher in the Amanzule forest (mean = 0.89 ± 0.10 t/ha) than in the Kakum forest (mean = 0.026 ± 0.019 t/ha). Soil carbon density was estimated as organic carbon and bulk density at specific depths in both forests. Soil organic carbon density was ~5-fold higher in the Amanzule forest (mean = 2935.79 ± 266 t/ha) than the Kakum forest (mean = 554.01 ± 83 t/ha). The variation in the vertical distribution of soil carbon was not significant in either forest (F = 0.57; p &gt; 0.05). These findings underscore the role of traditional conservation on mangrove carbon stocks and the need to consider the governance of coastal ecosystems when estimating blue carbon.

Effect of Forest Management on Carbon Stock of Tropical Moist Afromontane Forest

Moist tropical forests have a significant role in provisioning and regulating ecosystem services. However, these forests are under threat of deforestation and forest degradation. In Ethiopia, the moist evergreen Afromontane forests have the potential for carbon storage and support a high diversity of plant species. However, it is under severe threat of deforestation and degradation.This investigation was conducted to obtain adequate information on the carbon stock potential of the moist Afromontane forest of southwestern Ethiopia. A comparison of carbon stock was conducted between disturbed and undisturbed forests. A systematic sampling design was applied for recording woody species and soil data. A total of 100 main plots of 400 m2 were laid to record trees and shrubs with a diameter at breast height (DBH) ≥ 5 cm. The soil data were collected from 1 m2 subplots established at the four corners and the center of each main plot. The DBH and height were measured to calculate the aboveground carbon of trees and shrubs with DBH ≥ 5 cm. A total of 68 tree and shrub species belonging to 59 genera and 33 families were recorded. The mean carbon stock density was 203.80 ± 12.38 t·ha–1 (aboveground carbon stock) and 40.76 ± 2.47 t·ha–1 (belowground carbon stock). The highest proportion of aboveground carbon (t·ha–1) (42.34%) was contributed by a few tree individuals with DBH &gt; 70 cm. The soil organic carbon stock (SOCS) (t·ha–1) for the depth of 0–30 cm is ranging from 58.97 to 198.33 across plots; the mean is 117.16 ± 3.15. The carbon stored in the moist Afromontane forest indicates its huge potential for climate change mitigation. Therefore, for the enhancement of forest biodiversity and carbon sequestration effective conservation measure and sound management approach is essential.

Development of an Urban Turfgrass and Tree Carbon Calculator for Northern Temperate Climates

The presence of urban plants in an ecosystem are vital for processes including carbon sequestration and the type of urban plants included in urban settings affect the amount of carbon sequestered. The objective of this study is to assess the ability of urban plants to sequester carbon under a number of available management practices through the development and refinement of an accessible carbon calculator. Available urban plant data were analyzed using the calculator developed using available literature regarding carbon sequestration to determine differences between different types of plants, when hidden carbon costs (HCC) were considered. Carbon sequestration including HCC for turfgrasses could be calculated but there was a lack of information regarding HCC of urban trees and shrubs. The calculator was shown to be an effective tool for homeowners to determine viable management practices to maintain or increase carbon sequestration.

The synergistic effect of hydraulic and thermal impairments accounts for the severe crown damage in Fraxinus mandshurica seedlings following the combined drought-heatwave stress

Drought combined with extreme heatwaves has been increasingly identified as the important trigger of worldwide tree mortality in the context of climate change; nonetheless, our understanding of the potential hydraulic and thermal impairments of hot droughts to trees and the subsequent post-recovery process remains limited. To investigate the response of tree water and carbon relations to drought, heatwave, and combined drought-heatwave stresses, three-year-old potted seedlings of Fraxinus mandshurica Rupr., a dominant tree species in temperate forests of northeast China, were grown under well-watered and drought-stressed conditions and exposed to a rapid, acute heatwave treatment. During the heatwave treatment with a maximum temperature exceeding 40 °C for two days, the leaf temperature of drought-stressed seedlings was, on average, 5 °C higher than that of well-watered counterparts due to less effective evaporative cooling, indicating that soil water availability influenced leaf thermoregulatory capacity during hot extremes. Consistently, more pronounced crown damage, as shown by 13 % irreversible leaf scorch, was found in seedlings under the drought-heatwave treatment relative to sole heatwave treatment, alongside the more severe stem xylem embolism and leaf electrolyte leakage. While the heatwave treatment accelerated the depletion of non-structural carbohydrates in drought-stressed seedlings, the increase of branch soluble sugar concentration in response to heatwave might be related to the requirement for maintaining hydraulic functioning via osmoregulation under high dehydration risk. The coordination between leaf stomatal conductance and total non-structural carbohydrate content during the post-heatwave recovery phase implied that plant-water relations and carbon physiology were closely coupled in coping with hot droughts. This study highlights that, under scenarios of aggravating drought co-occurring with heatwaves, tree seedlings could face a high risk of crown decline in relation to the synergistically increased hydraulic and thermal impairments.

Temporal changes in tree community structure and carbon stocks in a human-impacted tropical dry evergreen forest, South India

Long-term studies in forest ecosystems are crucial to interpret the dynamics and are essential for conservation and management. However, characterizing long-term dynamics in relation to disturbance across dry tropics is often constrained by a dearth of data particularly from Indian tropics. In this context, a one-hectare permanent plot established in 2001 was revisited in 2011 and further re-censused in 2020 to ascertain species composition, stand structure and carbon stock dynamics of tree community over a 19-year period (2001−2020). Although species richness remained more or less unaffected, tree species composition did vary with the addition and loss of five and 10 species over this period. Species-level mortality rates overshadow the annual recruitment rate resulting in a net decrease in structural components. The results revealed that tree density decreased profoundly to 583 individuals ha−1 in 2020, roughly 46% of the initial inventory. Similarly, basal area is reduced by 40% (from 58.27 m2 ha−1 to 34.91 m2 ha−1), highlighting the impact of increased site disturbance over 19 years. The distribution of individuals and basal area to various diameter classes displayed a reverse J-shaped trend in both the inventories suggesting that all the size classes suffered equally over the years. The total carbon stock was as high as 416.01 Mg ha−1 in the initial inventory and reduced to 250.70 Mg ha−1 in the present re-census. Relative carbon stock calculations revealed that Ficus benghalensis (−46.05 Mg ha−1), Drypetes sepiaria (−22.68 Mg ha−1) and Pterospermum canescens (−14.98 Mg ha−1) represented 64.84% of total carbon stock loss over the period. Among the 29 resourceful species, Memecylon umbellatum, Drypetes sepiaria and Glycosmis mauritiana represented the highly targeted species with varied dietary and medicinal importance. These findings attest the impact of anthropogenic disturbances on species composition and carbon stock potential of the present site, which underline the need for such long-term monitoring efforts useful to forest management and conservation.

Sacred groves of Central India: Diversity status, carbon storage, and conservation strategies

AbstractSacred groves (SGs) play an important role in the conservation of local biodiversity and provide numerous ecosystem services worldwide. We studied how the ecological status of Central Indian SGs contributes to regional tree diversity and carbon (C) storage. We inventoried the trees in fifty‐nine SGs of Madhya Pradesh and recorded a total of 109 tree species (90 genera, 40 families). The most species‐rich families were Fabaceae, Combretaceae, Malvaceae, and Moraceae. The tree density ranged from 75 to 925 individuals ha−1 (mean: 398 ± 32 individuals ha−1), while basal area varied from 2.5 to 69.2 m2 ha−1 (mean: 24.2 ± 1.9 m2 ha−1). The total C stock {tree C + soil organic C (SOC; 0–30 cm)} ranged from 44.7 to 455.4 Mg C ha−1 (mean: 153.8 ± 9.6 Mg C ha−1) across the SGs. The studied SGs represented 74.7% of the total tree diversity and contained 33.1% higher total C stock than the forests of the state. Tree C stock was significantly positively correlated with tree basal area, distance from the nearest village, and number of years of existence. The present study highlights the crucial role of SGs in sustaining regional biodiversity and storing C in biomass and soil. Continued conservation efforts and contained interventions by people are necessary in order to maintain the current role of these SGs as biodiversity and carbon reservoirs of Central India.

Patterns and drivers of tree carbon stocks in Kashmir Himalayan forests: implications for climate change mitigation

BackgroundTemperate forests are major carbon sinks because of their high storage potential and low decomposition processes. We quantified tree carbon (TC) storage from 143 plots distributed across three major forest types of Kashmir Himalaya, relative to differences in ecological factors. Combined regression and Random Forest (RF) analysis were used to examine the distribution of TC stock along ecological gradients and recognize the role of driving factors on TC stocks.ResultsAmong the three forest types, sub-alpine (SA) forest was the primary TC sink, accounting for 228.73 t ha−1 of carbon, followed by mixed conifer (MC; 181.29 t C ha−1) and blue pine (BP; 133.04 t C ha−1) forests. The distribution of TC stocks among the three forest types differed significantly (χ2 = 18.87; P = 0.000). Relative carbon stock analysis demonstrated that Abies pindrow and Pinus wallichiana accounted 91% of TC stocks across the landscape. Basal area, mean diameter at breast height (DBH), elevation, disturbance and precipitation had significant effects on TC stocks in bivariate regression models. The RF model explained 86% of the variation; basal area interpreted 30.15%, followed by mean DBH (17.96%), disturbance complex (10.64%), precipitation (8.00%) and elevation (7.34%).ConclusionsKashmir Himalayan forests are significant carbon sinks as they store a substantial quantum of carbon in trees. Forest carbon, an essential climatic indicator, is determined by a complex interaction of other ecological variables, particularly stand structural features. The study provides insights into the role of these natural forests in climate change mitigation and in REDD+/national commitments to offset the carbon.

TreeMap 2016 Dataset Generates CONUS-Wide Maps of Forest Characteristics Including Live Basal Area, Aboveground Carbon, and Number of Trees per Acre

Abstract The TreeMap 2016 dataset provides detailed spatial information on forest characteristics including number of live and dead trees, biomass, and carbon across the entire forested extent of the continental United States at 30 × 30m resolution, enabling analyses at finer scales where forest inventory is inadequate. We used a random forests machine learning algorithm to assign the most similar Forest Inventory Analysis (FIA) plot to each pixel of gridded LANDFIRE input data. The TreeMap 2016 methodology includes disturbance as a response variable, resulting in increased accuracy in mapping disturbed areas. Within-class accuracy was over 90% for forest cover, height, vegetation group, and disturbance code when compared to LANDFIRE maps. At least one pixel within the radius of validation plots matched the class of predicted values in 57.5% of cases for forest cover, 80.0% for height, 80.0% for tree species with highest basal area, and 87.4% for disturbance. A new feature of the dataset is that it includes linkages to select FIA data in an attribute table included with the TreeMap raster, allowing users to map summaries of 21 variables in a GIS. TreeMap estimates compared favorably with those from FIA at the state level for number of live and dead trees and carbon stored in live and dead trees. Study Implications: TreeMap 2016 provides a 30 × 30 m resolution gridded map of the forests of the continental United States. Attributes of each grid cell include a suite of forest characteristics including biomass, carbon, forest type, and number of live and dead trees. Users can readily produce maps and summaries of these characteristics in a GIS. The TreeMap also includes a database containing, for each pixel, a list of trees with the species, diameter, and height of each tree. TreeMap is being used in the private sector for carbon estimation and by land managers in the National Forest system to investigate questions pertaining to fuel treatments and forest productivity as well as Forest Plan revisions.

Impact of forest fire frequency on tree biomass and carbon stocks in the tropical dry deciduous forest of Panna Tiger Reserve, Central India

Impact of forest fire frequency on tree biomass and carbon stocks in the tropical dry deciduous forest of Panna Tiger Reserve, Central India

Tree mortality and carbon emission as a function of wildfire severity in south-eastern Australian temperate forests

Disturbance trends over recent decades indicate that climate change is resulting in increased fire severity and extent in Australia's temperate Eucalyptus forests. As disturbance cycles become shorter and more severe, empirical measurements are required to identify potential change in forest carbon (C) stock and emissions. However, such estimates are rare in the literature.The 2019–2020 wildfires burnt through 6 to 7 million ha of mainly temperate open Eucalyptus forest in south-east Australia, with top down emission estimates ranging from 97 to 130 tonnes CO2 ha−1. Study sites that had been assessed for all aboveground C pools prior to the wildfires, were burnt in January 2020 by wildfire that varied in severity. Here we quantify the impact of high and low/moderate fire severities on tree mortality, C loss and C redistribution and assess implications for future C storage in these temperate Eucalyptus forests.Higher fire severity resulted in greater overstorey tree mortality but not understorey or loss of dead standing trees than in low/moderate severity fires. High severity fires combusted almost twice as much C from live trees (42 Mg C ha−1) as low/moderate severity fires (25 Mg C ha−1), while C loss from dead standing trees was similar among fire severity classes (average 17 Mg C ha−1). Total aboveground C lost across study sites was 42 Mg C ha−1 for high and 47 Mg C ha−1 for low/moderate severity, with an average of 45 Mg C ha−1 equivalent to 15 % (high severity) and 14 % (low/moderate severity) of AGC.Extrapolating our findings to other tall to medium open Eucalyptus forests across Victoria revealed that 37.33 ± 12.25 Tg C (mean ± s.e.) or 152 ± 50 Mg CO2 ha−1 was lost to the atmosphere from the 0.9 million ha of these productive forests, equating to about 20 % of Australia's total net annual emissions.

Estimating aboveground carbon stocks of urban trees by synergizing ICESat-2 LiDAR with GF-2 data

Accurately mapping carbon stocks of urban trees is necessary for urban managers to design strategies to mitigate climate change. However, the aboveground carbon stocks of urban trees are usually underestimated by passive remote sensing data because of the signal saturation problem. The research is the first attempt to develop a framework to map aboveground carbon density of trees in urban areas by synergizing Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) LiDAR data with Gaofen-2 (GF-2) imagery. The framework consists of three key steps. First, we used a support vector machine classifier to classify GF-2 images and extracted urban tree regions. Second, we estimated the tree carbon density of ICESat-2 strips by developing a ICESat-2 photon feature-based aboveground carbon density estimation model. Third, we mapped the carbon density of urban trees by developing a synergistic model between ICESat-2 and GF-2 data based on an object-oriented method. We tested the approach for the areas within the fifth ring road of Beijing, China. The results showed that the 50th percentile height (PH50) of nighttime photons was a good predictor for estimating carbon density of urban trees, with a R2 of 0.69 and a Root Mean Square Error (RMSE) of 2.81 kg C m−2. Using the spectral features generated by GF-2 imagery, we could further extrapolate the carbon density estimated by ICESat-2 strip data to a full coverage of accurate mapping carbon density by urban trees, resulting in a R2 of 0.64 and a RMSE of 2.32 kg C m−2. The carbon stocks within the fifth ring road of Beijing were 8.28 × 108 kg in total, with the mean carbon density of 3.52 kg C m−2. Such estimations were larger than that of previous study using passive remote sensing data only, suggesting the integration of spaceborne LiDAR and spectral data could greatly reduce the underestimation of carbon stocks of urban trees. Our approach can more accurately estimate carbon stocks of urban trees and has the potential to be applicable in other cities.