Soil Stocks Research Articles

Carbon accumulation over 70 years of old-field succession driven by live biomass in a Mediterranean continental environment

Forest expansion in abandoned agricultural lands entails the fixation of atmospheric CO2 in the live biomass, the soil as well as in other ecosystem compartments, and in turn, has strong implications for C budgets and the design of actions to mitigate climate change all over the world. However, changes in C stocks in these compartments are still poorly understood. We assessed the main patterns and drivers of C accumulation over spontaneous colonization of abandoned agricultural lands, considering the above- and below-ground biomass (AGB and BGB, respectively), the woody debris (WD), the litter and the surface soil (SS; 0–6 cm depth), in an area of Central-North Spain. To attain this objective, we established a chronosequence of 30 plots (0.0625 ha) located in agricultural lands abandoned in 1956–1977, 1977–2005 and 2005–2017, in four different forest types. We found that the AGB and the SS accounted for the major proportion of the total C stock, but the BGB was also relatively important. Carbon stocks in all these major compartments increased linearly with the age of tree colonization. But C in the SS did not significantly differ among plots abandoned in the three periods considered and showed decreasing rates of change from youngest (i.e. those in plots abandoned in 2005–2017) to oldest (i.e. those in plots abandoned in 1956–1977) stands. Carbon accumulation was mainly driven by adult stem density and age of tree colonization in the AGB and the BGB, and by the total nitrogen content in the SS. Our findings indicate that, in these new forests, C accumulation in the live biomass is still ongoing and proceeds relatively fast and at an increasing rate, which points toward a clear potential for atmospheric CO2 fixation over the next few decades. This process, however, proceeds more slowly and shows signals of an apparent deceleration in the SS. The C stock in the surface soil is, in fact, largely disconnected from that of live biomass and varies depending on pre-abandonment land-use differences among the study sites.

Strong links between aggregate stability, soil carbon stocks and microbial community composition across management practices in a Chinese dryland cropping system

Increasing soil carbon (C) stocks and improving soil structure are critical challenges in semi-arid agroecosystems. Conservation tillage has been widely applied to promote aggregate stability, enhance soil organic C (SOC) storage, and conjointly influence microbial community composition. However, the relation among soil microbial groups, aggregate stability and SOC stocks under management practices remains unclear. We conducted a 17-year field experiment in a spring maize cropping system on the Loess Plateau of northwest China, comparing three types of management: conventional tillage with residue removal (CT-RR), reduced tillage with residue incorporation (RT-RI) and no-tillage with residue mulching (NT-RM). We evaluated aggregate stability index (ASI), SOC stocks and microbial community composition at 0–10 and 10–25 cm. The results showed that RT-RI and NT-RM significantly increased ASI by 11% and 16% relative to CT-RR in the 0–10 cm layer; RT-RI significantly increased ASI by 13% relative to CT-RR in the 10–25 cm layer (p < 0.05). The RT-RI increased the SOC concentrations and SOC stocks of macroaggregates (>250 μm), which harbor most of the total SOC stocks in bulk soil. Both RT-RI and NT-RM increased total microbial biomass and biomass of six microbial groups (i.e., gram-negative bacteria (GN), gram-positive bacteria (GP), total bacteria (B), total fungi (F), arbuscular mycorrhizal fungi (AMF) and saprophytic fungi (SF)) at 0–10 cm, and RT-RI increased the above groups at 10–25 cm. Across a range of microbial community indicators, we found strong positive relationships between SOC and GN, ASI and AMF in bulk soil. A random forest analysis indicated that GN and F were the best microbial predictors of SOC concentrations and overall aggregate stability, whereas AMF/SF was the best predictor of SOC concentrations within aggregates and the stability of individual aggregate size classes. These results demonstrated a strong link between aggregate stability, SOC dynamics and microbial community composition, and suggest that conservation tillage increases both soil aggregation and SOC storage, thus providing sustainability and technical feasibility for the development of dryland agroecosystems.

Factors affecting the tree and soil carbon stock in Shorea robusta Gaertn. forests along the elevational gradient in Eastern Nepal

Shorea robusta Gaertn. forest is a tropical or sub-tropical forest that has a good potential to store carbon. However, its capacity to store carbon can vary along the elevational gradient. The present study aimed to find the relationship between carbon stock and factors (edaphic, topographic, and physical) affecting it in S. robusta forests along an elevational gradient in eastern Nepal. The study was conducted in three community forests in Sunsari and Dhankuta Districts, which were regarded as lower, middle, and upper altitude forests, respectively. Altogether, 90 circular plots (30 in each forest) were laid for trees. Physico-chemical parameters (nitrogen, potassium, phosphorus, organic matter, moisture, pH, and bulk density) were analyzed from all 90 plots. The carbon stock in trees and soil ranged from 134 t ha−1 to 372 t ha−1 and 27.69 t ha−1 to 60.03 t ha−1, respectively. The tree carbon stock was higher in lower altitude forests. However, the highest soil carbon stock was recorded in the higher altitude forest. Potassium content and pH were positively correlated with the tree carbon stocks. However, organic matter, nitrogen content, and altitude negatively influenced the tree carbon stock. Nitrogen content and altitude positively affected the soil carbon stock. However, potassium content and pH had a negative relationship with soil carbon stock. It is clear that these forests have served as carbon storage facilities, and the potential to store carbon was influenced by edaphic, physical and topographic factors. This research advances our knowledge of how community-managed Sal forests can help to mitigate the consequences of climate change along an elevational gradient.

Carbon sequestration and storage capacity of Chinese fir at different stand ages

In southern China, Chinese fir Cunninghamia lanceolata is one of the most important native conifer trees, widely used in afforestation programs. This area has the largest forestland atmospheric carbon sink, and a relatively young stand age characterizes these forests. However, how C. lanceolata forests evolved regarding their ability to sequester carbon remains unclear. Here we present data on carbon storage and sequestration capacity of C. lanceolata at six stand ages (5−, 10−, 15−, 20−, 30− and 60 − year−old stands). Results show that the carbon stock in trees, understory, vegetation, litter, soil, and ecosystem significantly increased with forest age. The total ecosystem carbon stock increased from 129.11 to 348.43 Mg ha−1 in the 5− and 60 − year−old stands. The carbon sequestration rate of C. lanceolata shows an overall increase in the first two stand intervals (5–10 and 10–15), peaks in the 15–20 stand intervals, and then decreases in the 20–30 and 30–60 stand intervals. Our result revealed that carbon sequestration rate is a matter of tree age, with the highest sequestration rates occurring in the middle age forest (15–20 − year−old). Therefore, this information may be useful for national climate change mitigation actions and afforestation programs, since forests are primarily planted for this purpose.

Root but not shoot litter fostered the formation of mineral-associated organic matter in eroded arable soils

Erosion leads to a decline in carbon (C) stocks in arable soils and negatively impacts soil functions worldwide. For soil restoration, it is critical to identify the factors that link crop residue quality to effective C sequestration in the soil, primarily through the formation of mineral-associated organic matter (MAOM) and through incorporation into aggregates (oPOM). The widely accepted concept links effective C stabilization with input of high-quality substrates, but studies of C-deficient soils do not support this assumption. Therefore, we aimed to determine the potential of eroded arable soils to stabilize C from barley shoot and root residues, which represent high- and low-quality inputs, respectively. In a year-long laboratory experiment, we added the residues to two soil pairs (eroded and non-eroded) with different soil textures, observed the formation of oPOM and MAOM and identified microbial groups important for substrate transformation. We found that eroded soils retained added residues very efficiently (35–65% bound residue C), making them a high-priority target for C sequestration. Root residues caused more efficient MAOM formation than shoot residues, primarily by direct binding of depolymerized root-C to mineral surfaces without subsequent microbial transformation. This root C stabilization in MAOM was more pronounced in eroded (highly C-undersaturated) soils than in non-eroded soils and in fine-textured soils, which provided more space for microbial colonization and C sorption, than in coarse-textured soils. Shoot residues were decomposed and metabolized by a microbiome rich in efficient bacterial decomposers (Actinobacteria, Xanthomonadales). This led to inevitably higher C losses related to their growth and biomass turnover, and probably also to an intense priming effect on pre-existing MAOM that lowered the efficiency of MAOM formation. Our results argue for crops with robust root systems, or for the inclusion of deep-rooted plants in crop rotations, which could help rapidly restore the C stocks in arable soils.

Nitrogen fertilizers technologies as a smart strategy to mitigate nitrous oxide emissions and preserve carbon and nitrogen soil stocks in a coffee crop system

The paper consolidates the role of conventional and stabilized N fertilizers used in coffee crop production in Brazil and their N2O emissions in tropical systems. The experiment consisted of the combination of three fertilizers and five doses with four repetitions, totalling 60 experimental plots. The factors of the experiment were conventional urea (U), ammonium nitrate (AN), and urea + NBPT (UNBPT), while the doses were 0, 150, 275, 400, and 525 kg ha−1 year−1 of N. The municipality is located in a region at 1100 m of altitude, 20°53′26.04″ S and 44°52′04.14″ W. A randomized block design with a 3 × 5 factorial scheme was used. This region, traditional in coffee production, has a tropical humid climate, classified as Cwa according to the Köppen scale, with temperate summer and dry winter. UNBPT and the ammonium nitrate mitigated the N2O emissions by 50.6% and 78.5%, respectively, in comparison to the conventional urea. High C stocks were found in the 1 m soil layer, from 117 to 162 t ha−1 of organic C, indicating the importance of the soil as a C sink in coffee plantations. N stocks varied from 33 to 17 t ha−1 of N but no differences among the treatments were found. Approximately 50% of soil C was in the 0–0.4 m layer as a consequence of the greater amount of plant biomass, nutrients, and biological activity. Soil C:N ratio in the entire layer varied from 4.2 to 9.2. Our results indicate that nitrification is the most predominant process of N2O emissions. The standard EF proposed by the IPCC overestimates the N2O emissions in the Brazilian coffee plantations and the emissions differ according to the N fertilizer technology. These coffee crop systems have an important ability to stock C and N in the soil.

Assessment of Carbon Stock and CO2 Production Potential for Soils of Coniferous-Broadleaved Forests

—The assessment of carbon stocks in soils of coniferous and broadleaved forests, agrocenoses, fallow lands, and floodplains has been performed for the territory of the Chashnikovo Agrobiological Station of Moscow State University. The typology of litter horizons, the contents of plant detritus in the them, and the ratio of the thicknesses of litter subhorizons have been determined as indicators of the organic matter decomposition intensity. For mineral soil profile, total organic carbon stocks in the layers of 0–30 and 0–100 cm layers and the stock of biologically active carbon in the layer of 0–20 cm layer have been determined. Maximum organic matter accumulation in litters and moderate accumulation in mineral profile is typical of soddy-podzolic soils (Retisols) under coniferous forests. The litter carbon stocks in spruce forests differ by almost an order of magnitude depending on the position in the tessera. Minimum carbon accumulation in litters is characteristic of the soils of upland and floodplain meadows. Alluvial soils of floodplain meadows are characterized by the highest stock of total carbon, as well as carbon of biologically active soil organic matter. The potential of CO2 production by soil determined the structural and functional litter characteristics and the stock of biologically active organic matter in the upper (0–20 cm) soil layer depend on several factors: vegetation type, hydromorphism degree, and agricultural use at present and in the past. Soils of coniferous forests in comparison with soils of broadleaved forests are characterized by lower rates of litter decomposition due to the biochemical features of plant remains and are assumed to have a lower potential for CO2 production. Soils of natural herbaceous ecosystems, especially floodplain meadows, are characterized by the maximum potential production of carbon dioxide due to intense decomposition of plant residues and high stock of biologically active organic matter carbon.

Soil Carbon Stock and Soil Properties under Different Land Use Types of Agriculture

Agriculture soils play a crucial role in carbon storage and food security. However, uncertainty remains about soil carbon stocks due to spatial variability. This study estimated soil carbon stocks in agricultural land and examined the impact of land use and soil properties on soil organic carbon in Ratchaburi Province, Thailand. Soil samples were collected at three depths (0-10, 10-20, and 20-30 cm) within five different land use types: cassava, coconut, paddy fields, pineapple, and sugarcane. The results revealed that soil organic carbon decreased with increasing depth. Significant differences in soil carbon and soil properties were observed among land uses. The carbon stocks at 0-30 cm depth were as follows: coconut (35.87 mg C/ha), paddy fields (31.17 mg C/ha), sugarcane (28.02 mg C/ha), pineapple (21.79 mg C/ha), and cassava (16.12 mg C/ha). The carbon stocks were significantly correlated with sand, density, clay, silt, and pH. This study highlights the impact of land use types on carbon stocks in agricultural soils and emphasizes the role of soil properties, particularly soil texture, in influencing carbon storage variability. Furthermore, the study highlights the carbon storage potential in agricultural areas, which could guide the formulation of policies to utilize agricultural land to offset CO2 emissions from other sectors.

Does olive cultivation sequester carbon?: Carbon balance along a C input gradient

Currently, there are some initiatives aimed at transforming agriculture from being a source to a sink of greenhouse gases, mainly by encouraging combination of management practices that drive nature-based climate processes (NbCS) resulting in an increase in the stocks of soil and biomass organic carbon. Olive grove cultivation represents a key socio-economic and environmental asset for Mediterranean rural regions. Being a woody crop planted in an orchard fashion, the potential for organic carbon accumulation in the biomass and the soil is very high. In this study, farm, trees and soil carbon balances were analysed in 12 pairs of olive groves located in Southern Spain with different tree densities, age, varieties and irrigation regimens. One from each pair of the olive groves has applied (> 8 years) a combination of management practices that promote NbCS resulting in an increase in the entry of carbon, whereas the other comparable nearby olive grove has not implemented management practices that promote NbCS or C entries (non-NbCS). C balance at the farm level was mainly neutral or positive and averaged + 1.20 Mg C ha−1 y−1. However, C balance in the NbCS olive groves was 5 times higher than that of the non-NbCS. The mean soil C balances were negative (−0.18 Mg C ha−1 y−1; losing soil organic C) in the non-NbCS and positive (+1.48 Mg C ha−1y−1) in the NbCS olive groves thanks to the increase in the carbon entries due to the management practices which boost NbCS. This study highlights the important contribution of olive farming in mitigating climate change, which in turn would be an economic incentive for olive growers. Nonetheless, there is a high potential for improvement by implementing management practices which enhance nature-based processes such as the cultivation of temporary spontaneous cover crops and the application of shredded tree pruning and composted olive mill pomace and/or manure to the soil.

Determining Environmental Drivers of Fine-Scale Variability in Blue Carbon Soil Stocks

Blue carbon ecosystems sequester and store a larger mass of organic carbon per unit area than many other vegetated ecosystems, with most being stored in the soil. Understanding the fine-scale drivers of variability in blue carbon soil stocks is important for supporting accurate carbon accounting and effective management of saltmarsh and mangrove habitats for carbon abatement. Here, we investigate the influence of local- and regional-scale environmental factors on soil organic carbon stocks using a case study from South Australia. We sampled 74 soil cores from mangrove, intertidal saltmarsh and supratidal saltmarsh sites where we also recorded precise elevation and vegetation data. Using a Bayesian mixed-effects regression approach, we modelled soil organic carbon stocks as a function of multiple environmental variables. The best model (Bayes R2 = 0.82) found that distance to the nearest tidal creek, vegetation type and soil texture significantly affected soil organic carbon stocks. Coarser soils with higher sand content had lower stocks, while finer-grained, clay-dominated soils had greater stocks. Mangroves had significantly greater stocks than intertidal saltmarshes and stocks were higher in sites closer to tidal creeks, highlighting the important role that local tidal creek systems play in sediment and water transport. This study’s findings are based on a broader range of local environmental factors than are usually considered in blue carbon models and increase our understanding and ability to predict site-level soil organic blue carbon stocks. The results emphasise the potential for organic carbon stocks to vary at local scales; the ability to predict this using appropriate environmental datasets; and the importance of accounting for local organic carbon stock variability when selecting sites for blue carbon-focussed restoration or conservation actions that aim to achieve carbon abatement.

Moving beyond agriculture and aquaculture to integrated sustainable food systems as part of a circular bioeconomy

The objective of this perspective paper is to present and discuss how systemic innovations can deliver a step change in the way food is produced in Europe. The production of healthy, safe and affordable food can contribute toward a just transition to net zero carbon (C) for Europe. A systemic and cross sectorial approach can contribute to climate mitigation by transfer of atmospheric CO2 to the terrestrial biosphere using low trophic species (LTS), including plants, seaweed and mussels (i.e. C sequestration) and increasing organic C stocks in soils and vegetation biomass (i.e. C storage). Innovative combinations of technologies applied to LTS, processed animal protein, new crops, and diversified and integrated production systems can link the high primary productivity rates of the marine environment to the C storage capability of the terrestrial food sector. Furthermore, the important roles of both private and public sector actors and better use of systemic approaches to further elucidate the multi-dimensional and multi-level interplays in complex food systems needs consideration. This can pave the way for linking and scaling up C-neutral marine and terrestrial food production systems into a future sustainable and circular bioeconomy. This systems-based approach can address some of the challenges associated with the current farming systems, as interdisciplinary research on aquaculture innovation can support the development of a resilient and sustainable food system. Examples of technologies provided include: a custom configured and digital user-oriented co-creation approach for Responsible Research and Innovation (RRI), a WebGIS tool on soil C storage, innovative composting methods, advanced breeding methods, new machinery for low greenhouse gas diversified orchard farming, AI model systems to improve decision support systems in management of soil, vertical farming, and animal feeding.

Agronomical management of detention basin

The importance of effective stormwater management through detention basin arrangement has become increasingly evident due to recurring extreme events in recent years. Limitations of the traditional detention basin include a reduced ability of basins to infiltrate water due to compacted soil and the carbon cost associated with the Diesel-powered tractors with lawn shredders. This study aims to compare six different agronomical management approaches for detention basins to improve the water storage capacity and the carbon sequestration potential, including the cultivation of crimson clover, white clover, tillage radish, and two mono-dicotyledonous mixes, against the conventional stable lawn-based approach. The trial was conducted in the detention basin in Castelletti (Firenze, Italy) for one growing season (2020/2021) according to a randomized complete block design with 9 replicates. Soil physical and chemical properties, as well as soil water storage capacity, were assessed to determine the feasibility of agronomical management for detention basins. Results indicated that the different treatments significantly influenced aboveground biomass production, soil organic carbon (SOC) stock, carbon sequestration potential, and water storage capacity. Specifically, crimson clover exhibited the highest aboveground biomass of around 6 t ha-1 among the treatments, while tillage radish demonstrated the greatest carbon sequestration potential (4.58 t CO2 ha-1), stable carbon stock in soil (1.14 t S-SOC ha-1), as well as the highest potential for improving the water storage volume (389 m3 ha-1) in the topsoil (0-20 cm) of the detention basin. The findings suggested also that the sowing of different mono-dicotyledonous plant mix were poorly effective in improving carbon sequestration potential and water storage volume compared to conventional basin management. To sum up, this experiment has demonstrated that alternative agronomical management practices can enhance the capacity of detention basins to store carbon and stormwater. These results provide valuable insights for improving the sustainability and functionality of detention basins.

Acacia auriculiformis agroforestry fallows of different ages improve soil physico-chemical properties and carbon stocks on the Batéké plateau, Democratic Republic of Congo

Our study evaluated the effects of Acacia auriculiformis agroforestry fallows installed on impoverished sandy soils of the Bateke Plateau in the Democratic Republic of the Congo (DRC). We compared physico-chemical properties and carbon stocks of soils under 1 to 3, 3 to 5 and 5 to 7 yr-old Acacia auriculiformis fallows and 5 yr-old savanna fallows. Soils were collected at depths of 0–10 cm, 10–40 cm and 40–100 cm and analyzed for the following parameters: soil organic carbon (SOC), nitrogen (N), available phosphorus (P), exchangeable cations (Ca2+, Na+, K+, Mg2+), cation exchange capacity (CEC), pH (H2O and CaCl2), granulometry and bulk density. In general, results obtained showed that agroforestry fallows are superior to traditional fallows for most measured parameters. The presence of A. auriculiformis improves the chemical properties of the soils compared to savanna soils; soil C and N concentrations as well as cation exchange capacity (CEC) were higher (P < 0.0001) under agroforestry soils than under savanna soils, especially between 0 and 10 cm depth. Our results also showed that A. auriculiformis agroforestry fallows stored 1.5 times more soil carbon than savanna fallows between 0 and 100 cm depth with 75, 106, 114, and 106 Mg C ha−1 respectively for savanna, 1–3 years, 3–5 years, and 5–7 years fallow soils. However, establishment of A. auriculiformis agroforestry fallows resulted in a decrease in soil pH compared to savanna soils. Differences in age and depth of the agroforestry fallow soils did not influence the physico-chemical properties evaluated. Overall, our results show that the establishment of A. auriculiformis agroforestry fallow improves the physico-chemical properties and increases soil carbon stocks compared to traditional savanna fallow. Therefore, we suggest the scaling up of the A. auriculiformis agroforestry improved fallow as a soil regenerative agrotechnology in the tropics.

Climate, as well as branch-level processes, drive canopy soil abundance and chemistry

Canopy soils can be important to forest nutrient cycling, hydrology, and biodiversity, but the factors determining their distribution and properties are largely unknown. We surveyed canopy soils across gradients of temperature and precipitation in six primary forests in Costa Rica. We used solid-state 13C nuclear magnetic resonance (NMR) and mass spectrometry (MS) to understand how the composition of canopy soil organic matter varies within and across sites. Climate, particularly fog, appears to drive canopy soil abundance across forests, while tree size determines canopy soil abundance within a forest. Canopy soil chemistry mostly varied within sites, though temperature was associated with the carbon (C) to nitrogen ratio, total dissolved nitrogen, and alkyl-C abundance, while fog explained some of the variation in dissolved organic carbon and O-alkyl C abundance. This study is the first-ever glimpse into large- and small-scale drivers of canopy soil abundance and biochemical composition. Our results highlight the importance of tree size and fog in determining the quantity and quality of canopy soil organic matter, suggesting that canopy soil stocks may be particularly vulnerable to climate and land use change. Identifying how multi-scale factors influence canopy organic matter processes will enhance our ability to identify and predict how environmental change might affect the abundance and chemistry of canopy soils and thus biodiversity that they support.

Improvement of the soil quality under intercropped conilon coffee (Coffea canephora P.) in the coastal tablelands of Southeast Brazil

The objective of this study was to evaluate the physical-hydrological and chemical properties and organic carbon stock of soil under intercropped conilon coffee (Coffea canephora P.) and in full sun in the coastal tablelands of Espírito Santo, Brazil. The treatments evaluated were coffee intercropped with rubber tree (CR) and in full sun (FS) in the area 1; coffee intercropped with papaya (CP) and in full sun (FS) in the area 2; coffee intercropped with coconut (CC), in full sun (FS), and an area of ​​native vegetation (NV) in the area 3. The physical and chemical properties of the soil and its organic carbon stocks were measured in layers of 0-0.4 m. In area 1, CR showed lower soil bulk density and temperature, and higher total porosity and macroporosity. In area 2, CP presented higher available water capacity and soil water content, better soil fertility, and lower soil temperature. In area 3, CC presented higher total porosity, available water capacity, and soil organic carbon stock. NV presented physical and chemical properties of soil that limit the agricultural development of the crops. Conilon coffee plantations can improve the physical-hydrological and chemical quality of soil compared to cultivation in full sun and native vegetation in the coastal tablelands, which varies according to the intercropped culture.

Changes in Organic Carbon Stock in Soil and Whole Tree Biomass in Afforested Areas in Latvia.

This study investigates the soil organic carbon (SOC) and whole tree biomass carbon (C), soil bulk density (BD) as well as changes in these parameters in afforested areas in Latvia. The study covered 24 research sites in afforested areas-juvenile forest stands dominated by Scots pine, Norway spruce and Silver birch. The initial measurements were conducted in 2012 and repeated in 2021. The results show that afforestation mostly leads to a general decrease in soil BD and SOC stock in 0-40 cm soil layer and an increase in C stock in tree biomass across afforested areas with various tree species, soil types, and former land uses. The physical and chemical properties of the soil could explain the differences in changes in soil BD and SOC caused by afforestation, as well as the impact of past land use may have persisted. When comparing the changes in SOC stock with the increase in C stock in tree biomass due to afforestation, taking into account the decrease in soil BD and the resulting elevation of soil surface level, the afforested areas at juvenile development stage can be considered a net C sink.

Review on Selected Church Forests of Ethiopia: Implication for Plant Species Conservation and Climate Change Mitigation

Forests are known to play an important role in the conservation of biodiversity and regulation of global climate. Global climate is regulated through sequestering and storing much more carbon from the atmosphere due to the presence of forests. However, loss of forest cover and biodiversity due to anthropogenic activities are a growing concern in many parts of the world. The problem of deforestation and loss of biodiversity is more pronounced in developing countries like Ethiopia. Because of deforestation, the species diversity and climate mitigation potential of natural forests are going to be reduced. Thus, patches of Church forests are left and found throughout the degraded landscapes. Because of their religious significance, these forests have been conserved by local communities. They are the only refuge for different plant species and store high amounts of atmospheric carbon. This is due to local communities do have higher respect and trust in them than other local institutions, which has made the Church the central institution and platform for socio-economic issues of the people. As stated by different scholars, around the Church areas, numerous indigenous and International Union for Conservation of Nature red list species existed. In terms of the diversity of species, the forest around the Church has compared to that of a natural forest. Next to the conservation role, the conserved plant species have a significant contribution to climate change mitigation through carbon stock in biomass and soil. Trees in the Church areas have long life history and are higher in stand structure parameters such as height, diameter at breast height, crown diameter, and their carbon storage potential has been maximum. Overall, Church forests are serving as hot spot sites for biodiversity conservation and have a significant role in mitigating climate change by limiting greenhouse gas emissions and increasing the amount of carbon stored in forests.

Ultisols with Unique Soil Properties and their Implications in Carbon Enhancement Strategies for Indian Tropical Soils

Million years old Ultisols, developed as an end stage of advance soil weathering on base-poor rock systems under forest and plantation crops of the Indian sub-continent, are enriched with organic carbon (OC). Despite their remarkable acid chemical reaction, they show an upward increase in extractable bases (EB) and base saturation (BS) in the pedon, and on some occasion BS &gt; 35% in surface horizons. Recent research suggests that the litter falls from forest species provide bases on soil surface, which causes similar depth distribution of EB and BS in Andisols of Nilgiri Hills of humid tropical southern India, developed on pre-weathered lateritic materials consisting primarily of Fe and Al oxides/ hydroxides. Under similar humid tropical (HT) climate in protected rain forest, million years old OC rich soils of Andaman and Nicobar Islands, developed on base-poor rock systems, have similar chemical and clay mineralogical properties of Ultisols except however their EB and BS, which are more than 10% and much above 50%, respectively and therefore, they are acidic Alfisols. Formation of Alfisols on the Island is a unique example on the formidable role of vegetation in soil formation, suggesting that if inland Ultisols are kept under natural protected forest ecosystem, they may phase towards Alfisols thereby facilitating OC sequestration and perform other ecosystem functions. The preservation of natural or semi-natural ecosystems is thus essential to raise the OC stocks of soils, which would help to gain various ecological benefits.

Grazing in a megagrazer‐dominated savanna does not reduce soil carbon stocks, even at high intensities

Recent studies suggest that wild animals can promote ecosystem carbon sinks through their impacts on vegetation and soils. However, livestock studies show that intense levels of grazing reduce soil organic carbon (SOC), leading to concerns that rewilding with large grazers may compromise ecosystem carbon storage. Furthermore, wild grazers can both limit and promote woody plant recruitment and survival on savanna grasslands, with both positive and negative impacts on SOC, depending on the rainfall and soil texture contexts. We used grazing lawns in one of the few African protected savannas that are still dominated by megagrazers (&gt; 1000 kg), namely white rhinoceros Ceratotherium simum, as a model to study the impact of prolonged and intense wild grazing on SOC stocks. We contrasted SOC stocks between patches of varying grazing intensity and woody plant encroachment in sites across different rhino habitat types. We found no differences in SOC stocks between the most‐ and least grazed plots in any of the habitats. Intermediately grazed plots, however, had higher SOC stocks in the top 5 cm compared to most and least grazed plots, but only in the closed‐canopy woodland habitat and not in the open habitats. Importantly, we found no evidence to support the hypothesis that wild grazing reduces SOC, even at high grazing intensities by the world's largest megagrazer. Compared to the non‐encroached reference plots, woody encroached plots had higher SOC stocks in soils with low clay content and lower SOC stocks in soils with high clay content, although only in the top 5 cm. Accordingly, our study highlights that wild grazers may influence SOC indirectly through their impact on tree‐grass ratios in grassy ecosystems. Our study thus provides important insights for future natural climate solutions that focus on wild grazer conservation and restoration.Keywords: fire, grazing impact, rewilding, soil carbon, white rhinoceros, woody encroachment

Molecular Weight Distribution of Humic Acids Isolated from Buried Soils and Yedoma Sediments

The soils of cold regions store up to 60% of all organic carbon on the planet. As a result of climate change, this organic matter can be biodegraded by microorganisms and thereby make an additional contribution to carbon balance. Nowadays, there are fragmentary data on organic C stocks in high-latitude soils and single works on the analysis of the quality of buried organic matter. This paper presents the first data on the molecular weight distributions of humic acids (HAs) extracted from soils and sediments in Yedoma. Molecular weight distributions of HAs preparations were obtained on an AKTAbasic 10 UPS chromatographic system (Amersham Biosciences, Sweden) using a SuperdexTM 200 10/300 GL column (with cross-linked dextran gel, fractionation range for globular proteins 10–600 kDa). As a result of the study, it was found that the buried soil horizons are characterized by the highest content of low molecular weight fraction (with molecular mass (Mr) 1.4–1.9 kDa and molar fraction in the range of 54.3–67.1%). The high molecular weight fraction is concentrated mainly in the superficial horizons and decreases with depth (with Mr 299–346 kDa and molar fraction in the range of 3.4–9.8%). In the Yedoma sediments, the maximum content of the medium-molecular fraction is observed (with Mr 24.6 kDa and 39.6% of the molar fraction), which may indicate a low rate of organic matter transformation in the permafrost. The data obtained serve as a database of analysis in terms of modeling the global carbon cycle in the cold regions of the planet.