The spatio-temporal analysis of land use changes & above-ground carbon stock in Sumbawa mangrove ecosystem, Indonesia

The unprecedented increase in atmospheric CO2 concentration has attracted global research attention on the potential role of tree plantations in climate change mitigation. There is an urgent need to estimate the above-ground biomass (AGB) and carbon stock in forest plantations. This is particularly essential for Sierra Leone, where above-ground biomass (AGB) and carbon stock data are presently lacking. This study estimated the above-ground biomass accumulation and carbon stock of Tectona grandis Linn.f. and Gmelina arborea Roxb. in the spacing and plantation trials at Njala University, Southern Sierra Leone. The assessment was based on a total inventory of trees having a diameter at breast height (DBH) ≥ 5 cm and tree height. Above-ground biomass (AGB) was estimated using the allometric equation by Chave et al. (2005), and above-ground carbon (AGC) stock was calculated by multiplying the biomass with a conversion factor of 0.5. The result showed that the mean above-ground carbon stock for Gmelina arborea was higher in the plantation trial (25.2 t ha-1) than in the spacing trial (7.5 t ha-1). For Tectona grandis, the mean above-ground carbon stock was similarly higher in the plantation trial (6.6 t ha-1) than in the spacing trial (1.5 t ha-1). The results further suggest that the variation in the means of above-ground carbon stock is not dependent on the tree species type and experimental site because there were no significant differences (P>0.05) between the tree species and experimental sites.

The importance of terrestrial ecosystems for carbon sequestration and climate regulation is acknowledged globally. However, the underlying structural drivers are still not well understood, particularly across distinct tropical forest ecosystems where trees species have different growth habits and potential to reach different maximal size. In particular, how important are different tree size classes in contributing to stand aboveground carbon (AGC) remains unclear across forest ecosystems. Here, we hypothesized that (i) tree size classes would contribute differently to stand AGC across forest ecosystems; and (ii) few species, possibly dominant, would determine most of stand AGC. We tested these hypotheses using a 17-ha sampled inventory data from gallery forests, woodlands and savannahs in the Republic of Benin. We examined (i) how AGC stocks vary among small- (<20 cm), medium- (20–40 cm) and large-size (>40 cm diameter at breast height - dbh) trees; (ii) how the large size class and its individual species contribute to AGC; and (iii) how size class-based taxonomic and structural variables influence AGC?Stand AGC was 23 ± 5, 30 ± 8 and 42 ± 12 MgC ha−1 in savannah, woodland and gallery forest, respectively. There were significant main and interaction effects of vegetation types and size classes. As expected, medium and large-size classes contained more of the AGC, irrespective of the vegetation type. However, gallery forests had the lowest AGC in the <20 cm dbh class, but higher values in medium- and large-size classes as compared to woodlands and savannahs. The top 10 species contributed 82%, 89% and 91% of AGC in gallery forests, woodlands and savannahs, respectively. In addition, five of the top 10 dominant species were shared by the three vegetation types and alone contributed 70–76% of AGC. Tree basal area was the most constant structural attribute influencing AGC; however, its influence shifted with vegetation type and size class, with greater effects of large-size tree basal area in gallery forests, and of medium trees and small trees’ basal area in woodlands and savannahs, respectively. The study shows that (i) AGC allocation to size class varied across vegetation types, and (ii) small and medium trees are also important in predicting AGC, especially in semi-arid environments dominated by high densities of small-size trees (e.g. woodlands and savannahs). It also highlights the importance of few dominant species in contributing a large proportion of AGC stocks. The conservation of these dominant species is essential to avoid substantial decline of AGC stock.

Bark beetle outbreaks kill billions of trees in western North America, and the resulting tree mortality can significantly impact local and regional carbon cycling. However, substantial variability in mortality occurs within outbreak areas. Our objective was to quantify landscape-scale effects of beetle infestations on aboveground carbon (AGC) stocks using field observations and remotely sensed data across a 5054 ha study area that had experienced a mountain pine beetle outbreak. Tree mortality was classified using multispectral imagery that separated green, red, and gray trees, and models relating field observations of AGC to LiDAR data were used to map AGC. We combined mortality and AGC maps to quantify AGC in beetle-killed trees. Thirty-nine per cent of the forested area was killed by beetles, with large spatial variability in mortality severity. For the entire study area, 40–50% of AGC was contained in beetle-killed trees. When considered on a per-hectare basis, 75–89% of the study area had >25% AGC in killed trees and 3–6% of the study area had >75% of the AGC in killed trees. Our results show that despite high variability in tree mortality within an outbreak area, bark beetle epidemics can have a large impact on AGC stocks at the landscape scale.

Human activities have been severely affecting forest structure and functions in humid tropics across the globe. In present study, we estimated aboveground biomass and carbon stocks along a disturbance gradient in wet tropical forests of southern Assam, India, using non-destructive sampling method. A total of 26 forest stands were surveyed and based on a disturbance index grouped into 4 categories, viz. undisturbed (UD), mildly disturbed (MLD), moderately disturbed (MD) and highly disturbed (HD) forests. Mean aboveground carbon (AGC) stocks and basal area decreased with increased disturbance index. Though phytosociological parameters such as species richness, Shannon-Wiener diversity index, tree density, basal area and AGC stocks showed a significant negative correlation with disturbance index, tree density (693 ± 11.6 trees ha−1) and Shannon-Wiener diversity index (1.98 ± 0.07) were highest in mildly disturbed forests. Aboveground carbon stocks were positively correlated with basal area (p < 0.01) and diversity indices (p < 0.01) across disturbance regimes. Tree species such as Cynometra polyandra, Mesua ferrea, Palaquium polyanthum, Mesua floribunda, Artocarpus chama and Stereospermum personatum together contributed 41.3 ± 6.2 % and 42.4 ± 6.7% of the total AGC stocks in undisturbed and mildly disturbed forests, respectively, while Artocarpu schama, Holarrhena pubescens, Mitragyna rotundifolia, Sapium baccatum, Schima wallichii and Toona ciliata contributed 47.2 ± 3.5% in moderately and 55.4 ± 4.0% in highly disturbed forests.

Planting forests is an important practice for climate change mitigation, especially in the tropics where the carbon (C) sequestration potential is high. Successful implementation of this mitigation practice requires knowledge of the role of species identity and diversity on carbon accrual of plantations. Despite this need, solid data on the long‐term development of forest plantations are still very scarce. Monospecific and two species mixture plots of a 77‐year‐old tree diversity experiment in Yangambi in the Congo basin were fully inventoried. We calculated above‐ground C stocks using allometric equations, and soil C stocks by analyzing soil samples at multiple depths. Linear mixed effects models were used to analyze the effect of taxonomic and functional identity and diversity on the aboveground and soil carbon stocks. A high variability in aboveground C stocks across tree species combinations was observed. Apart from a species identity effect, the proportion of planted species in the total stand basal area (BApl) and effective species richness were identified as compositional parameters with a significant effect on the aboveground carbon (AGC), with BApl being more important. Both AGC and BApl were coupled to the functional identity of the planted species; the planting of short‐lived pioneers led to low AGC. We found no clear benefits, but also no drawbacks, for AGC of two species mixture plots over monospecific plots or including nitrogen fixing species in the plantation scheme. However, the latter was the only compositional parameter with a significant positive effect on the soil carbon stock up to 1 m depth. We conclude that the different plantation configurations gave rise to a wide range in carbon stocks. This was predominantly caused by large differences in AGC sequestration over the past 77 years. Altogether, short‐lived pioneer species had a low BApl resulting in low carbon sequestration, while partial shade tolerant species achieved the highest AGC stocks. Tolerating spontaneous ingrowth during the plantation development can further increase the AGC stock, given that the appropriate functional type is planted.

Carbon recovery in secondary forests: Insights from three West African countries

ABSTRACTUrban vegetation can help to offset carbon emissions. However, urban vegetation cover is vulnerable to urbanization. This study attempts to detect the change in vegetation cover and to quantify its impact on aboveground carbon (AGC) stocks in Auckland, New Zealand, between 1989 and 2014. Field-measured vegetation parameters were used to calculate the amount of carbon stored in plants at the plot-level. Plot-level AGC stocks were linked with vegetation spectral/structural features derived from Landsat images and Light Detection and Ranging (LiDAR) data. These data were also used to map vegetation cover and to estimate AGC stock. Vegetation cover decreased from 394.0 km2 in 1989 to 379.4 km2 in 2014. AGC stock in 1989 was estimated at 1,001,184 Mg C from Landsat 4 data. The total AGC in 2014 was estimated at 1,459,530 Mg C from Landsat 8 data. Thus, total AGC stock increased by 458,346 Mg C (45.8%) in spite of a 3.7% decrease in vegetation cover (14.6 km2) during the same period. The increase in AGC stock was derived partly from tree growth and tree plantings. Vegetation growth contributed more to the increase in AGC stock than its gain from non-vegetation to vegetation changes. The AGC stored in trees and shrubs estimated at 1,333,011 Mg C from the 2014 Landsat data is 5.7% lower than 1,414,607 Mg C estimated from the 2013 LiDAR data, due to the inability of optical imagery to capture the sub-canopy structure of forests and the saturation effect. Thus, LiDAR data provided a more accurate estimate of AGC stock, especially when the stock density is high (e.g. >97.9 Mg C ha–1).

&#x0D; &#x0D; &#x0D; Homegardens are one of the most significant and oldest types of land use systems in Sri Lanka which have been recognized as an essential component in providing a variety of ecosystem services. In these systems, trees and shrubs are grown together with food crops under family labor, creating a multitude of biological interactions. Due to rich tree diversity and density, homegarden agroforestry systems are known to have a great capacity to capture and store carbon in their biomass and soil, and thus greatly contribute to mitigation of climate change. Even though the importance of homegardens with regard to the above is highlighted significantly, large knowledge gaps remain on their total carbon storage potential, particularly in low country wet zone homegardens of Sri Lanka. Therefore, the current study aims to estimate the total aboveground and belowground carbon stocks of homegardens in Kalutara district. The study was conducted in ten homegardens ranging from 0.15 Ha to 0.43 Ha. The study focused on all perennial woody trees present in the homegardens. Heights and diameters at breast height (DBH) were measured in a total of 966 woody trees. Aboveground biomass of each tree was calculated nondestructively, using allometric equations which incorporated wood density, DBH and tree height. Belowground biomass was calculated using root: shoot ratios of trees. Total biomass of each tree was converted to total carbon stocks using a conversion factor of 0.5 extracted from literature, considering that total carbon stock of a tree is equivalent to half of its biomass. In order to get the total carbon stock, soil organic carbon (SOC) content of each home garden was analyzed in the laboratory from collected soil samples using the Loss-on-ignition method. Belowground biomass carbon stock and the SOC stock together were taken as the total belowground carbon stock of each homegarden. Estimated mean aboveground carbon stock was 91.4±11.4 Mg ha-1, while the mean belowground carbon stock was determined as 134.3±12.3 Mg ha-1 in low country wet zone home gardens. Aboveground carbon stock, together with the belowground carbon stock, was taken as the total carbon stock of the homegardens. Calculated total carbon stock per unit area for low country wet zone homegardens ranged between 179.873 Mg ha-1 and 286.606 Mg ha-1 with a mean value of 225.7±11.9 Mg ha-1. Above findings of the study present evidence for significant carbon storage capacity of low country wet zone homegardens.&#x0D; Keywords: Homegarden, Low country, Wet zone, Carbon stock, Climate change&#x0D; &#x0D; &#x0D;

Types of agroforestry systems and their capacity to sequester carbon vary globally, and the extent of carbon sequestered greatly depends on environmental conditions and system management. This study aimed at investigating the species composition and determining the aboveground carbon stocks of coffee agroforests at low (1240–1320 m a.s.l.) and medium (1321–1504 m a.s.l.) elevations of Manafwa District in Uganda. For each elevation, the agroforest structures were described and the aboveground carbon (AGC) stocks estimated using allometric models for all measured shade and coffee trees. Two coffee varieties were cultivated with SL-14 extending up to 40 years, while LWIL-11, a more recently introduced variety, extended up to 7 years only. Therefore, the estimated AGC stocks were significantly greater for the SL-14 (0.250–2.317 tons ha−1) than LWIL-11 (1.044–2.099 tons ha−1) and were significantly higher at the medium versus the low elevation. The analysis for shade trees indicated no significant differences in the species diversity for the elevation sites, but with significant variations in mean DBH and thus AGC stocks. Farms at low elevation were characterized by smaller (2.037 ± 0.131 tCO2e ha−1) and significantly high (2.037 ± 0.131 tCO2e ha−1) mean AGC stocks per unit area for coffee and shade trees, respectively, as compared to the medium elevation farms. While the variation in the coffee trees within the elevation sites could be attributed to the uneven distribution within the age groups, the AGC stocks in the shade trees were attributed to the generally large sizes of the trees that dominated. Irrespective of the differences in elevation attributes, coffee agroforests can potentially provide carbon sinks and thus contribute to climate change mitigation.

Despite the importance of agroforestry parkland systems for ecosystem and livelihood benefits, evidence on determinants of carbon storage in parklands remains scarce. Here, we assessed the direct and indirect influence of human management (selective harvesting of trees), abiotic factors (climate, topography, and soil) and multiple attributes of species diversity (taxonomic, functional, and structural) on aboveground carbon (AGC) stocks in 51 parklands in drylands of Benin. We used linear mixed-effects regressions and structural equation modeling to test the relative effects of these predictors on AGC stocks. We found that structural diversity (tree size diversity, HDBH) had the strongest (effect size β = 0.59, R2 = 54%) relationship with AGC stocks, followed by community-weighted mean of maximum height (CWMMAXH). Taxonomic diversity had no significant direct relationship with AGC stocks but influenced the latter indirectly through its negative effect on CWMMAXH, reflecting the impact of species selection by farmers. Elevation and soil total organic carbon content positively influenced AGC stocks both directly and indirectly via HDBH. No significant association was found between AGC stocks and tree harvesting factor. Our results suggest the mass ratio, niche complementarity and environmental favorability as underlying mechanisms of AGC storage in the parklands. Our findings also highlight the potential role of human-driven filtering of local species pool in regulating the effect of biodiversity on AGC storage in the parklands. We conclude that the promotion of AGC stocks in parklands is dependent on protecting tree regeneration in addition to enhancing tree size diversity and managing tall-stature trees.

Mangrove forests are important sinks of atmospheric carbon, and the internal deposits and fluxes of organic matter can reflect how these ecosystems respond to disturbances and environmental changes. Data on carbon content of mangrove forests vary geographically due to differences in abiotic (climate, geomorphic settings, tides) and biotic (diversity, herbivory, bioturbation) conditions. Mangroves have been degraded worldwide and ecological restoration is an alternative to recover these ecosystems and their functionality. However, although growing and biomass after disturbances have been addressed, studies on the recovery of faunal groups are rare. The brachyuran crab assemblage is strongly integrated to carbon recycling and ecosystem functioning, since propagule consumption and fossorial activity can affect the diversity and biomass of mangroves. We assessed the aboveground biomass and carbon stock of differently managed mangrove areas in northeastern Brazil, after being deforested for shrimp culture and then abandoned, and compared data with other forests worldwide. After a decade, the area restored with Rhizophora mangle showed higher carbon stock than the self-recovered forest and similar amount as an older forest. We discuss the applied rehabilitation measures regarding the effects of management and brachyuran crabs on forest aboveground carbon storage. The effects of herbivory and bioturbation of brachyurans on the low recruitment of Laguncularia racemosa propagules, contributed to higher biomass levels in the restored forest through reinforcing the predominance of R. mangle, which stocks more aboveground carbon with respect to Laguncularia. This suggests that the particularities of target tree species and brachyuran assemblage need to be considered in mangrove restoration, since they are related to function recovering and carbon cycling in the ecosystem.

Changes of vegetated land to built-up land will affect the above ground carbon (AGC) stocks in an area. These changes have an impact on climate change. This study aimed to estimate AGC stocks changes in Mijen Sub-District during 2017-2022. Mijen Sub-District is one of the suburban areas of Semarang City which has the main function as the lungs of the city. To determine the AGC stock, remote sensing data and GIS analysis are used. The results showed that during 2017-2022 AGC stock in the area decreased by 3,234.24-ton C. Estimation of changes of AGC stocks in Mijen Sub-District needed as a reference for local governments for policy making in regional and urban planning that integrates sustainable development.

Brazil is one of the major contributors to land-use change emissions, mostly driven by agricultural expansion for food, feed, and bioenergy feedstock. Policies to avoid deforestation related to private commitments, economic incentives, and other support schemes are expected to improve the effectiveness of current command and control mechanisms increasingly. However, until recently, land tenure was unknown for much of the Brazilian territory, which has undermined the governance of native vegetation and challenged support and incentive mechanisms for avoiding deforestation. We assess the total extent of public governance mechanisms protecting aboveground carbon (AGC) stocks. We constructed a land tenure dataset for the entire nation and modeled the effects and uncertainties of major land-use acts on protecting AGC stocks. Roughly 70% of the AGC stock in Brazil is estimated to be under legal protection, and an additional 20% is expected to be protected after areas in the Amazon with currently undesignated land undergo a tenure regularization. About 30% of the AGC stock is on private land, of which roughly two-thirds are protected. The Cerrado, Amazon, and Caatinga biomes hold about 40%, 30%, and 20% of the unprotected AGC, respectively. Effective conservation of protected and unprotected carbon will depend on successful implementation of the Forest Act, and regularization of land tenure in the Amazon. Policy development that prioritizes unprotected AGC stocks is warranted to promote conservation of native vegetation beyond the legal requirements. However, different biomes and land tenure structures may require different policy settings considering local and regional specifics. Finally, the fate of current AGC stocks relies upon effective implementation of command and control mechanisms, considering that unprotected AGC in native vegetation on private land only accounts for 6.5% of the total AGC stock.

Tropical montane forests play a key role in carbon storage, but they face constant threats from land use change. However, the relations between land use change, vegetation structure and carbon stocks remain poorly understood. We aimed to assess aboveground carbon storage in four land use types within a montane forest in the Central Andes of Peru. We quantified carbon stocks from trees, crops, dead biomass, and herbaceous plants across 61 sample plots. We identified a gradient of carbon storage from highest to lowest across land uses: Old-growth Montane Forest (193.03 ± 68.2 t ha -1), Montane Forest in Regeneration (87.52 ± 50.29 t ha -1), Agroforestry (48.67 ± 24.05 t ha -1), and Croplands (12.46 ± 9.75 t ha -1). Vegetation structure variables (tree height, DBH, basal area, and tree density, canopy cover) showed a significant positive correlation with aboveground carbon stocks (r2 ranging from 0.63 to 0.91). In contrast, soil physical properties (textural class (% sand, silt, and clay) and soil bulk density) did not correlate with aboveground carbon stocks. Our estimations indicate that trees are a great carbon pool and the presence of trees with DBH ≥ 30 often indicates conservation status. This study proves that there is a loss of carbon storage and vegetation structural characteristics as land use intensifies. Restoration of degraded forests and adoption of an agroforestry approach offer promising alternatives to preserve ecosystem functions and mitigate climate change.

Tree-size dimension inequality shapes aboveground carbon stock across temperate forest strata along environmental gradients