Affect Soil Organic Carbon Research Articles

Forest land-use change affects soil organic carbon in tropical dry forests of the Peruvian Amazon

Aim of study: The loss of forest cover is a global problem that alters ecosystems, contributing to carbon emissions. This study measured the soil organic carbon (SOC) at different soil depths in tropical dry forests of the Huallaga Central in the Peruvian Amazon. Area of study: San Martín Region, Peruvian Amazon. Material and methods: A total of 24 plots of 100 m2 were selected in primary (~200 years), intervened (~50 years since intervention), and deforested forests (10 years ago), with 120 soil samples collected across five depths. Soil texture (hydrometer), bulk density (cylinder method), SOC content, SOC density, and erodibility (K parameter) were calculated. Main results: SOC content in the 0-20 cm soil horizon was 79.5±21.3 t ha-1 for the primary forest, 58.5±11.8 t ha-1 for the intervened forest, and 41.8±10 t ha-1 for the deforested forest. A soil erodibility K of 0.065 was observed for primary forests and 0.076 and 0.093 for intervened and deforested forests. In average, the SOC density obtained in this study was 7.6±5.1 t ha-1 in the primary forest, 6.2±3.6 t ha-1 in the intervened forest, and 4.7±2.7 in the deforested forest. Research highlights: Primary forests had the highest SOC content and SOC density, followed by intervened and deforested forests, while the opposite pattern was found for soil erodibility. These patterns were especially marked in the first 40 cm of soil depth.

Differential diversity and structure of autotrophs in agricultural soils of Qinghai Province.

Agricultural soil plays important roles in carbon fixation during carbon capture and storage. Autotrophic bacteria that utilize inorganic compounds as electron donors for growth fix CO2 photosynthetically or chemo-autotrophically in diverse ecosystems and affect soil organic carbon sequestration. Soil properties, agronomic management measures, and environmental factors can influence the community composition, abundance, and activity of CO2-assimilating bacteria. This study aims at evaluating the effects of different regions and crop types on the abundance, composition, and activity of CO2-fixing bacteria in agricultural soil.

Coupled iron oxides and microbial-mediated soil organic carbon stabilization across tea plantation chronosequences

Soil acidification due to long-term tea plantations is a pervasive problem that may affect soil organic carbon (SOC) preservation by altering organo-mineral interactions. Nevertheless, how iron (Fe) minerals and microbes regulate SOC stabilization with increasing years of tea plantation establishment remains unclear. By analyzing the dynamic changes of SOC, Fe fractions and Fe oxide-bound OC (Fe–OC) pools, and associations with microbial communities over tea plantation establishment time-series (1, 7, 16, 25, and 42 years), this study explored the roles of coupled Fe oxides and microbial communities in regulating SOC accumulation and stabilization. The SOC levels significantly increased with years of tea plantation, accompanied by increases in the proportions of macroaggregates, poorly crystalline Fe oxides and organically complexed Fe, but soil pH decreased sharply. The increased soil Fe–OC pool and molar C:Fe ratios were positive correlated with SOC and macroaggregates, indicating that SOC was preserved by physic-chemical protection. Furthermore, these changes induced decreases in microbial biomass C and bacterial diversity with years of tea plantation. The relative abundance of A-strategists (i.e., Acidobacteria, Actinobacteria, Chloroflexi) increased concurrently, with an opposite trend for Y-strategists, suggesting tea plantation-induced environmental changes shifted the Y-strategists towards the predominance of A-strategists. Collectively, these findings provide new insights into the role of Fe oxides and microbial life history traits in SOC accumulation and stabilization in the progression of tea plantation establishment, including (i) physic-chemical protection of SOC through formation of Fe–OC by complexation; and (ii) regulation of the microbial community diversity and composition, especially bacterial life strategies. These results are of great implications for better predicting and accurately controlling the response of OC pools in tea plantations to future changes and disturbances and for maintaining regional C balance.

Soil and Microbial Biomass Response to Land-Use Changes in the Loess Plateau

Vegetation restoration is a critical strategy for addressing ecosystem degradation globally. However, understanding the specific impacts of land-use changes, particularly the conversion of farmland to forestland and grassland, on soil nutrients and microbial biomass in the Loess Plateau remains limited and requires further evaluation. Therefore, this study was conducted to explore how these conversions affect soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and microbial biomass components under various land-use patterns. We studied the SOC, TN, TP, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) content and their ratios under six land-use patterns (Farmland (FL), Abandoned cropland (ACL), Natural grassland (NG), Alfalfa grassland (Medicago sativa L. (MS)), Spruce forestland (Picea asperata Mast. (PA)) and Cypress forestland (Platycladus orientalis (L.) Franco (PO))). The conversion of FL to grassland and forestland significantly increased C:N and C:P by 9.82~64.12%, 10.57~126.05%, and 51.44~113.40%, 22.10~116.09%, respectively. The conversion of FL to ACL reduced the C:N and C:P by 5.34~13.57% and 1.51~7.55%, respectively. The conversion of FL to NG can increase soil N:P. The conversion of FL to grassland and forestland increased soil MBC, MBN, and MBP by −31.54~84.48%, −48.39~1533.93%, −46.55~173.85%, and −34.96~17.13%, 68.72~432.14%, −38.39~318.46%, respectively. However, the MBC, MBN, and MBP contents in the soil converted from FL to ACL varied from −28.21~11.95%, 11.17~531.25%, and −82.64~70.77%, respectively. Soil SOC, TN, TP, available potassium (AK), pH, and soil bulk density (BD) are the main factors causing microbial biomass differences. These results indicate that converting farmland into forestland and grassland can improve soil nutrient structure and increase soil microbial biomass and carbon accumulation. The results of this study provide theoretical support for the scientific management of regional land.

Effects of tree species composition in plantation forest on soil aggregate stability and organic carbon pools in northeastern China

Forest tree species composition influences soil aggregate stability (SAS) and labile organic carbon (LOC) components, which may affect soil organic carbon (SOC) sequestration. Despite the general belief that mixed forests enhance SOC storage, evidence suggests that certain monocultures may outperform mixed forests. Therefore, information on the specific impact of tree species mixing on SOC through SAS and LOC remains limited. This study aimed to investigate the effects of tree species composition on SAS and LOC in 49-year-old monoculture (Larix gmelinii (Lg), Pinus koraiensis (Pk)) and mixed conifer-broadleaf (Larix gmelinii - Fraxinus mandshurica (LF), and Pinus koraiensis - Populus ussuriensis (PP)) stands, and its impact on SOC sequestration. We measured SAS indices (including mean weight diameter (MWD), geometric mean diameter (GMD), and > 0.25 mm water stable aggregate proportion (WSA)), SOC storage, and LOC components (easily oxidized organic carbon (EOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC)) in 0–40 cm soil horizons during the growing season (June, August, and October). Our results showed that tree species composition significantly influenced SAS and SOC components, with the highest SAS found in the 0–20 cm soil horizon in Pk and PP forests (p < 0.05) (Jun.: MWD Pk: 0.98, GMD Pk: 1.88, WSA Pk: 1.79, MWD PP: 0.98, GMD PP: 1.90, WSA PP: 1.81; Aug.: MWD Pk: 0.99, GMD Pk: 1.85, WSA Pk: 1.77, MWD PP: 0.99, GMD PP: 1.89, WSA PP: 1.81; Oct.: MWD Pk: 0.98, GMD Pk: 1.86, WSA Pk: 1.76, MWD PP: 0.97, GMD PP: 1.83, WSA PP: 1.73) and the highest SOC components in the LF stand (p < 0.05) (soil horizon 0–20 cm: Jun.: SOC: 110.23 g/kg, EOC: 92.81 g/kg, MBC: 1418.39 mg/kg, DOC: 1090.01 mg/kg; Aug.: SOC: 108.46 g/kg, EOC: 79.57 g/kg, MBC: 1369.91 mg/kg, DOC: 1316.11 mg/kg; Oct.: SOC: 109.78 g/kg, EOC: 44.37 g/kg, MBC: 1782.6 mg/kg, DOC: 671.05 mg/kg). Correlation analysis revealed significant relationships between SOC and LOC components (p < 0.05, r EOC = 0.43, r MBC = 0.46, r DOC = 0.17) but not associated with SAS (p > 0.05, r MWD = −0.07, r GMD = −0.07). Tree species composition in plantation stands significantly affects SAS and SOC pools. In conclusion, the positive effect of mixed coniferous and broad-leaved forests on SAS and SOC pools is also contingent upon the tree species identity. The results suggest that targeted selection of tree species could better enhance SAS and SOC pools in plantation than a mere increase in species richness.

Predominant Cropping Systems affect Soil Organic Carbon Content in the Soil Profile of North–West India

Predominant Cropping Systems affect Soil Organic Carbon Content in the Soil Profile of North–West India

Evaluating factors affecting soil organic carbon retention in sustainable stormwater nature - based technologies

Low impact development (LID) are prominent type of vegetated stormwater infrastructure that provides various ecosystem services, such as biodiversity, carbon storage, and improvement in air quality. This study investigated six LID technologies to assess SOC retention and factors influencing accumulation. Soil samples (0–20 cm depth) were analyzed using the Walkley-Black method, specifically focusing on wet oxidation. SOC stocks ranged from 18.5 to 66.3 t C/ha in the inflow and 18.6 to 79.1 t C/ha in the outflow, with SCW and TBF showing higher SOC due to root turnover, stormwater runoff, and media composition. This study found that vegetation and impervious catchments significantly influenced SOC levels. Trees exhibited higher SOC due to their extensive root systems and longer life cycles. Roads and parking lots had higher SOC from plant debris and hydrocarbons in stormwater runoff. SOC also varied seasonally, peaking in spring due to photosynthesis and decreasing in summer and autumn from increased microbial respiration. A complex relationship between SOC and soil physico-chemeical perameters were also investigated, with moisture content and total nitrogen being critical factors for carbon stocks. Overall, the results from this study are seen as beneficial in optimizing the design guidelines for LID technologies for carbon sequestration and green space expansion in urban areas.

Litter and Root Removal Modulates Soil Organic Carbon and Labile Carbon Dynamics in Larch Plantation Ecosystems

Plant detritus plays a crucial role in regulating belowground biogeochemical processes in forest ecosystems, particularly influencing labile carbon (C) dynamics and overall soil C storage. However, the specific mechanisms by which litter and roots affect soil organic carbon (SOC) and its components in plantations remain insufficiently understood. To investigate this, we conducted a detritus input and removal treatment (DIRT) experiment in a Larix principis-rupprechtii Mayr plantation in the Taiyue Mountains, China, in July 2014. The experiment comprised three treatments: root and litter retention (CK), litter removal (LR), and root and litter removal (RLR). Soil samples were collected from depths of 0–10 cm and 10–20 cm during June, August, and October 2015 to evaluate changes in soil pH, water content (SW), SOC, dissolved organic carbon (DOC), readily oxidizable organic carbon (ROC), and microbial biomass carbon (MBC). The removal of litter and roots significantly increased soil pH (p &lt; 0.05), with pH values being 8.84% and 8.55% higher in the LR and RLR treatments, respectively, compared to CK treatment. SOC levels were significantly reduced by 26.10% and 12.47% in the LR and RLR treatments, respectively (p &lt; 0.05). Similarly, DOC and MBC concentrations decreased following litter and root removal, with DOC content in August being 2.5 times lower than in June. Across all treatments and sampling seasons, SOC content was consistently higher in the 0–10 cm depth, exhibiting increases of 35.15% to 39.44% compared to the 10–20 cm depth (p &lt; 0.001). Significant negative correlations were observed between SOC and the ratios of ROC/SOC, pH, DOC/SOC, and MBC/SOC (R = −0.54 to −0.37; p &lt; 0.05). Path analysis indicated that soil pH had a significant direct negative effect on SOC (p &lt; 0.05), with a standardized path coefficient (β) of −0.36, while ROC had a significant direct positive effect on SOC (β = 0.66, p &lt; 0.05). Additionally, pH indirectly affected SOC by significantly influencing ROC (β = −0.69), thereby impacting SOC indirectly. Random forest analysis also confirmed that the ROC/SOC ratio plays a critical role in SOC regulation. This study reveals the complex interactions between litter and root removal and soil C dynamics in larch plantations, identifying soil pH and ROC as crucial regulator of SOC content. However, the short-term duration and focus on shallow soil depths limit our understanding of long-term impacts and deeper soil C storage. Future research should explore these aspects and consider varying climate conditions to enhance the applicability of our findings. These insights provide a scientific foundation for developing effective forest management strategies and forecasting changes in soil C storage in the context of climate change.

Effects of incorporating biochar on soil quality and barley yield in microplastics-contaminated soils

Biochar has been recognized for its potential to improve the fertility soils by reducing the reliance on chemical fertilizers, mitigating carbon emissions, and fostering soil microbial growth. This study aimed to evaluate the impact of biochar addition on the physicochemical properties of arid and semi-arid soils containing microplastics, while also assessing its effect on Barley (Hordeum vulgare) yield under drought stress. The experiment was conducted in a glass greenhouse. Plastic pots containing 3 kg of soil were each planted with 6 barley grains. Biochar was applied at three doses (B0 = 0 g biochar/kg soil, B1 = 6 g biochar/kg soil, B2 = 10 g biochar/kg soil), while microplastics were added at three levels (M0 = Control without microplastics, M1 = 0.5 g/kg soil, and M2 = 1 g/kg soil) on the same sowing date. Water stress was induced when the plants reached the four-leaf stage. ANOVAs and Tukey post-hoc tests were employed for multiple mean comparisons of soil and plant parameters. Drought stress and microplastics negatively influenced soil parameters namely soil moisture, organic carbon, and nitrates, while also affecting electrical conductivity and pH. Biochar exhibited minimal effect on soil properties but significantly altered pH, nitrates, and total CaCO3. Plant chlorophyll levels decreased under stress, particularly with microplastic dose M1. However, biochar and microplastics enhanced chlorophyll a content, except for dose B1 of biochar, which leads to a decrease in chlorophyll b (0.91 ± 0.138 μg/g FM). Microplastics, at dose M2, improved chlorophyll b content (1.11 ± 0.090 μg/g FM). Aboveground biomass, leaf area, and yield were generally unaffected by tested stresses. Nonetheless, barley grain yield decreased in biochar and microplastic dose M1 (0.47 ± 0.108 g/plant), while it improved with microplastic dose M2 (0.65 ± 0.168 g/plant). Leaf relative water content increased under water stress and microplastics but not with biochar alone. Interaction between microplastics and biochar enhanced plant water content. Drought stress and microplastics diminished soil parameters, whereas biochar lowered nitrates and pH without significantly affecting soil organic carbon. Plant productivity parameters generally exhibited no significant change under water stress, microplastics, or biochar, except for yield and chlorophyll pigments.

Nitrogen addition promotes soil carbon accumulation globally.

Soil is the largest carbon (C) reservoir in terrestrial ecosystems and plays a crucial role in regulating the global C cycle and climate change. Increasing nitrogen (N) deposition has been widely considered as a critical factor affecting soil organic carbon (SOC) storage, but its effect on SOC components with different stability remains unclear. Here, we analyzed extensive empirical data from 304 sites worldwide to investigate how SOC and its components respond to N addition. Our analysis showed that N addition led to a significant increase in bulk SOC (6.7%), with greater increases in croplands (10.6%) and forests (6.0%) compared to grasslands (2.1%). Regarding SOC components, N addition promoted the accumulation of plant-derived C (9.7%-28.5%) over microbial-derived C (0.2%), as well as labile (5.7%) over recalcitrant components (-1.2%), resulting in a shift towards increased accumulation of plant-derived labile C. Consistently, N addition led to a greater increase in particulate organic C (11.9%) than mineral-associated organic C (3.6%), suggesting that N addition promotes C accumulation across all pools, with more increase in unstable than stable pools. The responses of SOC and its components were best predicted by the N addition rate and net primary productivity. Overall, our findings suggest that N enrichment could promote the accumulation of plant-derived and non-mineral associated C and a subsequent decrease in the overall stability of soil C pool, which underscores the importance of considering the effects of N enrichment on SOC components for a better understanding of C dynamics in soils.

Increased rainfall frequency enhances dry seasonal soil mineral-associated organic carbon in a subtropical forest

Climate models predict longer and more severe droughts, and alterations in the frequency and intensity of rainfall events. However, how changing precipitation patterns affect soil organic carbon (SOC), particulate organic carbon (POC), and mineral-associated organic carbon (MAOC) remains unclear. Here, we conducted a three-year rainfall manipulation experiment with ambient rainfall as the control, removal of half the total rainfall amount with unaltered frequency (DRA), and increased rainfall frequency with the total amounts unchanged (IRF) in a subtropical forest. The results showed that the rainfall treatments did not change SOC content or fractions during the wet season. In the dry season, DRA significantly increased topsoil POC but did not change SOC or MAOC. IRF significantly increased POC and MAOC levels. The increased MAOC was associated with the newly formed binary complexes of Fe3+, Al3+, and Ca2+, and the adsorption/precipitation of reduced short-range-ordered Fe oxides, likely derived from the enhanced reductive dissolution in the IRF treatment. Our results suggest that changes in rainfall frequency affect organo-mineral interactions more profoundly relative to the rainfall amount and that these effects are season-dependent. Therefore, moisture-sensitive geochemical processes play an essential role in SOC stabilization in subtropical forests.

Vegetation degradation reduces aggregate associated carbon by reducing both labile and stable carbon fraction in Northeast China

Vegetation changes can affect soil organic carbon (SOC) content and storage by altering the inputs of plant biomass and the catabolism and anabolism of soil microorganisms. However, influence of vegetation degradation on aggregate associated carbon fractions and the contribution of different aggregates to total SOC in bulk soil remains poorly understood. In this study, undisturbed soil samples were collected from three types of grassland in Songnen grassland: an undegraded grassland (LEY, Leymus chinensis), a moderately degraded grassland (CHL, Chloris virgata), and a severely degraded grassland (SUA, Suaeda heteroptera). Three soil aggregates including macroaggregate (> 0.25 mm), microaggregate (0.053–0.25 mm) and silt and clay fraction (< 0.053 mm) were separated using wet sieving. Contents of total SOC, soil labile and stable carbon in bulk soil and different soil aggregates were measured. Compared with LEY, the mean weight diameter and geometric mean diameter under the degraded vegetation communities reduced by 39.42 % and 28.47 %, respectively. The reduction in SOC contents in bulk soil, macroaggregate, microaggregate and silt and clay fraction resulting from vegetation degradation was 49.81 %, 26.00 %, 76.17 % and 43.65 %, respectively. Under the degraded vegetation communities, contents of soil labile and stable carbon in bulk soil (45.73 % and 52.61 %, respectively), macroaggregate (17.38 % and 31.61 %, respectively), microaggregate (77.83 % and 74.18 %, respectively), and silt and clay fraction (21.20 % and 53.45 %, respectively) were significantly lower than those under LEY. The contribution of macroaggregate, microaggregate and silt and clay fraction to total SOC was 13.27 %, 23.61 % and 63.12 %, respectively. The contribution of soil aggregates to total SOC following vegetation degradation reduced by 53.63 % for microaggregate, but increased by 47.10 % for silt and clay fraction. These findings collectively indicate that vegetation degradation reduces the aggregate associated carbon content by reducing both labile and stable carbon fraction in Songnen grassland, and sustainable vegetation restoration strategies are need to enhance soil carbon storage in Northeast China.

Impacts of freeze-thaw process on soil microbial nutrient limitation in slope farmlands of the Chinese Mollisol region

Understanding the impacts of freeze-thaw action on soil microbial nutrient limitation can provide important support for sustainable utilization of black soil resources. We analyzed the impacts of freeze-thaw action on soil microbial nutrient limitation on a slope farmland located in a typical thick Mollisol region of Keshan County, Heilongjiang Province. We examined the responses of soil microbial nutrient limitation to soil erosion rates through measuring soil nutrient, soil microbial biomass, and soil enzyme activities before and after freeze-thaw under natural conditions, and estimated the soil erosion rates by 137Cs tracing technology. The results showed that: 1) soil erosion rates of slope farmland ranged from 479.31 to 7802.33 t·km-2·a-1, with an average value of 2751.02 t·km-2·a-1. 2) Under freeze-thaw process, soil water-soluble organic nitrogen and microbial biomass carbon (MBC) of slope farmland significantly decreased by 27.9% and 37.3%, respectively. However, the freeze-thaw process did not affect soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), water-soluble organic carbon, soil available phosphorus, microbial biomass nitrogen and phosphorus. 3) Under freeze-thaw action, the activities of β-1,4-glucosidase, L-leucine aminopeptidase and β-1,4-N-acetyl-glucosaminidase significantly decreased by 43.2%, 11.0%, and 25.5%, respectively. The results of the enzyme quantification vector model indicated that soil microorganisms were limited by carbon and phosphorus availability. The freeze-thaw action weakened the relative carbon limitation of soil microorganisms and strengthened the phosphorus limitation. 4) The structural equation model analysis indicated that freeze-thaw action had a direct positive effect on relative phosphorus limitation and a negative effect on relative carbon limitation in soil microorganisms. Soil erosion rates had a direct negative effect on relative carbon limitation of soil microorganisms. 5) Soil erosion rates had significantly negative influences on SOC and TN before and after freeze-thaw, TP after freeze-thaw, MBC after freeze-thaw, and vector length before freeze-thaw. Overall, freeze-thaw action reduced the activities of soil carbon and nitrogen acquisition enzymes and further changed the resource limitation of soil microorganisms. Our results could improve the understanding of the mechanisms regarding freeze-thaw action impact on the limitation of soil microbial resource in the Chinese Mollisol region and provide scientific support for nutrient management of slope farmland.

Intercropping Legumes Improves Long Term Productivity and Soil Carbon and Nitrogen Stocks in Sub‐Saharan Africa

AbstractFood, feed, and fiber production needs to increase to support demands of the growing population in Sub‐Saharan Africa (SSA), while soil fertility continues to decline. Intercropping, the cultivation of two or more crop species on the same field, can provide yield benefits and is suggested to positively affect soil organic carbon (C) and nitrogen (N) stocks. This study uses the biogeochemical model system LandscapeDNDC with the objective to (a) represent maize‐legume intercropping systems in different bioregions in SSA by simultaneously simulating both crops and their interactions and (b) assess long‐term (20 years) impacts of intercropping under varying mineral fertilizer inputs (0–150 kg N ha−1 yr−1) on productivity as well as soil organic C and N stocks. We test LandscapeDNDC on 82 field data sets (site‐year‐treatment combinations) from 18 sites to represent yields and soil C/N dynamics of maize‐legume intercropping systems. Using the model for long‐term scenario simulations showed that intercropping allows to sustain productivity and to improve or maintain SOC stock in low or zero fertilizer systems if all residues are returned to the soil. In contrast, for sole‐cropped maize systems, a decline in SOC stocks was simulated unless a minimum of 35 kg N ha−1 yr−1 of fertilizer was applied at full residue return. We conclude that intercropping using legumes alongside sufficient residue return allows for stabilizing long‐term yields while avoiding SOC losses even with low fertilizer N inputs. Overall, our study confirms the potential of intercropping as a sustainable agricultural practice that could significantly contribute to food security in SSA.

Long‐Term Biochar Application Improved Aggregate K Availability by Affecting Soil Organic Carbon Content and Composition

ABSTRACTStraw biochar is an effective amendment at improving soil aggregate structure and increasing soil carbon and potassium (K) content. However, little information is available on the relationship between soil organic carbon (SOC) and aggregate‐associated K distribution under long‐term biochar application conditions. To address this, a field trial established in 2013 was used to examine the impact of biochar (B0: 0 and B1: 2.625 t ha−1 year−1) and K fertilizer (K0: 0 and K1: 60 kg ha−1 year−1) on the variation in soil aggregate K and reveal the associated influencing factors. A total of four treatments (B0K0, B0K1, B1K0, and B1K1) were included in this study. The soil analysis results obtained in 2021 showed that after 9 years' amendment, B1K1 increased the aggregate exchangeable K (EK) and nonexchangeable K (NEK) pools by 27.40% and 39.55%, respectively, and the increment was primarily because biochar enhanced &gt; 0.25 mm aggregate fractions and strengthened soil K+ adsorption capacity, which benefit from a synergistic increase in SOC and humic acid (HA) content by biochar. 13C NMR analysis showed that long‐term biochar applications altered the chemical composition of SOC, with an outcome of increased aromaticity and hydrophobicity but decreased the lipidation of SOC, indicating that the complexity of SOC molecular structure was enhanced and eventually contributed to strengthening the macroaggregates stability and soil K+ adsorption capacity. The correlation analysis revealed that soil aggregate EK and NEK contents were positively correlated with SOC and HA contents, which further proved that increase of SOC and soil HA is a significant mechanism for biochar ameliorate soil aggregate‐associated K availability.

Change in Land Use Affects Soil Organic Carbon Dynamics and Distribution in Tropical Systems

Anthropogenic land cover change is directly responsible for the deforestation and degradation of tropical forests. In this context, assessing soil organic carbon (SOC) stocks is key to understanding the impact of anthropogenic activities on SOC so that we can implement management practices that effectively reduce emissions or promote carbon sequestration. Our objective was to assess the effect of land-use change on the dynamics and distribution of SOC in three systems (agriculture, pasture and agroforestry) after 40 years of deforestation in a tropical dry forest in the central–eastern region of Honduras. For this purpose, the bulk density, percentage of coarse fragments (&gt;2 mm) and soil organic carbon content were determined at three depths (0.00–0.10 m, 0.10–0.20 m and 0.20–0.30 m). The results showed an increase in bulk density for all new uses, although soil compaction had not yet occurred. In terms of total soil organic carbon (TOC) stocks, deforestation caused a decrease from 17% to 48% in agricultural and agroforestry soils, respectively; on the other hand, grasslands did not show significant differences compared to tropical dry forest, suggesting that they have a high potential as carbon sinks in deforested tropical areas. However, this did not imply a better state of the system, as the greatest increases in bulk density were found in pastures.

Sugarcane/Soybean Intercropping with Reduced Nitrogen Application Synergistically Increases Plant Carbon Fixation and Soil Organic Carbon Sequestration.

Sugarcane/soybean intercropping and reduced nitrogen (N) application as an important sustainable agricultural pattern can increase crop primary productivity and improve soil ecological functions, thereby affecting soil organic carbon (SOC) input and turnover. To explore the potential mechanism of sugarcane/soybean intercropping affecting SOC sequestration, a two-factor long-term field experiment was carried out, which included planting pattern (sugarcane monocropping (MS), sugarcane/soybean 1:1 intercropping (SB1), and sugarcane/soybean 1:2 intercropping (SB2)) and nitrogen addition levels (reduced N application (N1: 300 kg·hm-2) and conventional N application (N2: 525 kg·hm-2)). The results showed that the shoot and root C fixation in the sugarcane/soybean intercropping system were significantly higher than those in the sugarcane monocropping system during the whole growth period of sugarcane, and the N application level had no significant effect on the C fixation of plants in the intercropping system. Sugarcane/soybean intercropping also increased the contents of total organic C (TOC), labile organic C fraction [microbial biomass C (MBC) and dissolved organic C (DOC)] in the soil during the growth period of sugarcane, and this effect was more obvious at the N1 level. We further analyzed the relationship between plant C sequestration and SOC fraction content using regression equations and found that both plant shoot and root C sequestration were significantly correlated with TOC, MBC, and DOC content. This suggests that sugarcane/soybean intercropping increases the amount of C input to the soil by improving crop shoot and root C sequestration, which then promotes the content of each SOC fraction. The results of this study indicate that sugarcane/soybean intercropping and reduced N application patterns can synergistically improve plant and soil C fixation, which is of great significance for improving crop yields, increasing soil fertility, and reducing greenhouse gas emissions from agricultural fields.

Microbial traits affect soil organic carbon stability in degraded Moso bamboo forests

Microbial traits affect soil organic carbon stability in degraded Moso bamboo forests

Long-Term Planting of Taxodium Hybrid ‘Zhongshanshan’ Can Effectively Enhance the Soil Aggregate Stability in Saline–Alkali Coastal Areas

Not enough research has been conducted on the mechanisms influencing the stability of soil aggregates in coastal saline–alkaline soil and the dynamic changes in aggregates in the succession process of coastal saline–alkaline soil brought on by longer planting times. In this study, soil aggregate composition, stability, and influencing factors of 0–20 cm, 20–40 cm, and 40–60 cm soil layers in different planting time stages were analyzed in the reclaimed land at the initial stage of afforestation and the Taxodium hybrid ‘Zhongshanshan’ plantation with planting times of 6, 10, 17, and 21 years. The results show that, with the increase in planting time, the aggregate stability of the plantation increased significantly. In the 0–20 cm soil layer, the geometric mean diameter (GMD) and aggregate size &gt;0.25 mm (R0.25) increased by 81.15% and 89.80%, respectively, when the planting time was 21 years, compared with the reclaimed land. The structural equation (SEM) showed that planting time had a direct positive effect (path coefficient 0.315) on aggregate stability. However, soil sucrase (0.407) and β-glucosidase (0.229) indirectly improved the stability of aggregates by affecting soil organic carbon. In summary, the establishment of Taxodium hybrid ‘Zhongshanshan’ plants on coastal saline–alkali land is beneficial for stabilizing soil aggregates, improving soil structure, and boosting soil quality. Long-term planting of Taxodium hybrid ‘Zhongshanshan’ can be an effective measure for ecological restoration in this region.

Straw incorporation and nitrogen fertilization regulate soil quality, enzyme activities and maize crop productivity in dual maize cropping system

BackgroundStraw incorporation serves as an effective strategy to enhance soil fertility and soil microbial biomass carbon (SMBC), which in turn improves maize yield and agricultural sustainability. However, our understanding of nitrogen (N) fertilization and straw incorporation into soil microenvironment is still evolving. This study explored the impact of six N fertilization rates (N0, N100, N150, N200, N250, and N300) with and without straw incorporation on soil fertility, SMBC, enzyme activities, and maize yield.ResultsResults showed that both straw management and N fertilization significantly affected soil organic carbon (SOC), total N, SMBC, soil enzyme activities, and maize yield. Specifically, the N250 treatment combined with straw incorporation significantly increased SOC, total N, and SMBC compared to lower fertilization rates. Additionally, enzyme activities such as urease, cellulase, sucrose, catalase, and acid phosphatase reached their peak during the V6 growth stage in the N200 treatment under for both straw management conditions. Compared to N250 and N300 treatments of traditional planting, the N200 treatment with residue incorporation significantly increased yield by 8.30 and 4.22%, respectively. All measured parameters, except for cellulase activity, were significantly higher in spring than in the autumn across both study years, with notable increases observed in 2021.ConclusionsThese findings suggest that optimal levels of SOC, soil total N (STN), and SMBC, along with increased soil enzyme activities, is crucial for sustaining soil fertility and enhancing maize grain yield under straw incorporation and N200 treatments.