Soil Organic Carbon Storage Research Articles

Enhancement of soil humic acid hydrophobicity by 5 consecutive years of full-amount straw shallow-mixed field return

Crop yield is directly influenced by the storage and stabilisation of soil organic carbon (SOC), which is determined by the hydrophobicity of soil humic acid (HA). Changes in soil HA hydrophobicity, humic substances, SOC and crop yield were compared after the application of different amounts of straw returns in the field, and the contribution of straw application in enhancing HA hydrophobicity was examined. The treatments included no straw application and soil stirring, no straw application with soil stirring, application of half-amount straw shallow-mixed field return, application of full-amount straw shallow-mixed field return and application of double-amount straw shallow-mixed field return. Using elemental analysis, infrared spectroscopy and fluorescence spectroscopy, the structural hydrophobicity of soil HA was exhaustively characterised. The results showed that the hydrogen to carbon ratio of HA increased by 11.46%, the ratio of hydrophobic to hydrophilic intensity increased by 21.02%, and the ratio of peak B to peak A fluorescence intensity decreased by 32.21% after 5 years of full amount straw shallow-mixing field return compared to no straw application and soil stirring. The observed results indicate that the augmentation in hydrophobicity stimulates the formation of HA, enhances soil humification, elevates SOC content by 9.78% and potentially contributes to the ultimate crop yield increase by 22.98%. Compared with stirring the soil, the contribution rate of applying full amount of straw to increase HA hydrophobicity was 49.57-62.05%, and the contribution rate to increase SOC and yield were 54.59% and 76.37%, respectively. While stirring the soil contributed to increasing hydrophobicity, straw application persisted as the primary factor in enhancing hydrophobicity. The findings of this study have significant implications for understanding the mechanism by which straw improves HA hydrophobicity, thereby facilitating carbon sequestration and increasing crop yield.

Divergent mechanisms driving nutrient stoichiometry in surface and deep soils of desert ecosystems on the Qinghai–Tibetan plateau

The ecological stoichiometric properties of desert soils determine nutrient availability and contribute to biodiversity and ecosystem stability. We obtained 1784 soil samples from 330 soil profiles distributed across the desert area of the Qinghai–Tibet Plateau (QTP). We measured the content of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali-hydrolyzed nitrogen (AN), available phosphorus (AP), and available potassium (AK) to elucidate the vertical patterns of soil stoichiometric characteristics and their driving factors. We found a unique vertical distribution of SOC and soil nutrients in the QTP desert ecosystem: the proportions of SOC and nutrient storage in the topsoil (0–20 cm) were the highest that have been reported to date, especially for the proportion of SOC, which reached 54 %. The vertical distributions of SOC and AN fit an exponential function (r = 0.247 and 0.249), TN fit a linear function (r = 0.115), and TP, AP, and AK fit a curvilinear function (r = 0.127, 0.175, and 0.103), indicating that soil components exhibited a depth-dependent distribution in the alpine desert ecosystem. With increasing soil depth, C:N and C:P decreased significantly, AN:AP first increased and then decreased, and AP:AK first decreased and then increased. The factors that influenced soil nutrients and stoichiometry differed between the topsoil (0–20 cm) and deep soil (20–100 cm) layers. In the topsoil (0–20 cm), vegetation and precipitation were the dominant factors for soil nutrients and stoichiometry, while topography and climate affected soil nutrients and stoichiometry indirectly by influencing vegetation growth. In the deep soil (20–100 cm), silt particles and precipitation were the dominant factors for soil nutrients and stoichiometry, but climate affected soil nutrients and stoichiometry indirectly, mainly by influencing soil texture. The inconsistencies of nutrient stoichiometric driving mechanisms in surface and deep soils contributed to a comprehensive understanding of soil stoichiometric properties at the profile scale of desert ecosystems.

Tree species selection for optimizing soil carbon storage: Insights from litter decomposition and bacterial community analysis in coastal ecosystems

Coastal wetland ecosystems are critical sinks for atmospheric carbon dioxide, playing a vital role in global carbon cycling and climate regulation. The decomposition of leaf litter plays a crucial role in the formation and stability of soil organic carbon (SOC) in these environments. This study investigated the impact of leaf litter decomposition from five tree species (Populus deltoids, Ligustrum lucidum, Taxodium 'Zhongshanshan', Hibiscus hamabo, and Nerium oleander) on SOC dynamics, humus composition, and soil bacterial community structure in a tidal flat. Litterbags were used to monitor the mass loss and changes in litter chemical composition over 270 days. The results revealed significant differences in decomposition rates among the tree species, with Nerium oleander exhibiting the fastest decomposition and Populus deltoids the slowest. Surprisingly, initial litter chemistry did not correlate with decomposition rates; however, changes in lignin and hemicellulose content during decomposition were significantly related to mass loss. Despite its rapid decomposition, Nerium oleander litter resulted in the highest accumulation of SOC, total humus, and humin compared to the other species, challenging the conventional view that slower decomposition leads to greater SOC storage. The soil microbial community structure was significantly influenced by SOC, humus, and litter components, with distinct microbial assemblages associated with each tree species. A random forest model identified key bacterial taxa, predominantly Proteobacteria, as important predictors of SOC content, highlighting the role of bacterial diversity in regulating SOC dynamics. These findings underscore the importance of considering litter quality, decomposition dynamics, and bacterial community composition in strategies aimed at enhancing soil carbon sequestration. This study suggests that selecting tree species with rapidly decomposing litter, such as Nerium oleander, in coastal plantations can be an effective management tool for optimizing soil carbon storage, offering valuable insights for mitigating climate change impacts.

Protective role of reactive aluminum phases to stabilize soil organic matter against long-term cultivation in the humid tropics under volcanic influence

ABSTRACT Cultivation can cause rapid depletion of soil organic matter (SOM), particularly in the humid tropics. Understanding the factors controlling SOM storage is a key step toward effective soil management for sustainable crop production. While clay + silt content is known to be an important factor for soil organic carbon (SOC) storage, recent studies have shown greater importance of oxalate-extracted Al (Alo; roughly corresponds to short-range-order aluminosilicate minerals and organo-Al complexes) and Fe (Feo). However, the extent to which these mineralogical factors control the response of SOM pool to land-use changes remains unclear, especially in the tropics. This study aimed to clarify the factors regulating SOM content in croplands compared to secondary forests or home gardens in Negros Occidental, Philippines. Along two line transects having a wide range of Alo contents, soil samples were collected at a depth of 0 − 10 cm from sugarcane sites (n = 33; long-term continuous cultivation of >70 years) that were paired with either secondary forests (n = 10) or home gardens (n = 20). Sugarcane sites had significantly lower SOC and total nitrogen (N) contents than secondary forest and home garden sites, whereas there was no clear difference between the latter two land uses. Both SOC and total N contents showed significant positive correlations with Alo content and, to a much less extent, with Feo content, but not with clay + silt content. The slope of the regression line between SOC and Alo was indifferent between sugarcane and the other two land uses, while the intercept was significantly lower in the sugarcane sites. These results suggest the protective role of Alo phases in both agricultural and forest soils and the presence of unprotected SOM (e.g. plant litter) in the latter sites. Furthermore, δ13C analysis suggested that the proportion of forest (C3 plant) derived carbon remaining in the sugarcane soils ranged between 10% and 50% and increased with Alo content. Together, our study showed indirect evidence of Alo-induced stabilization of SOM against long-term cultivation under the humid tropical environment.

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.

Arbuscular mycorrhizal symbiosis enhances the accumulation of plant-derived carbon in soil organic carbon by regulating the biosynthesis of plant biopolymers and soil metabolism

Plant-derived carbon (C) is a critical constituent of particulate organic carbon (POC) and plays an essential role in soil organic carbon (SOC) sequestration. Yet, how arbuscular mycorrhizal fungi (AMF) control the contribution of plant-derived C to SOC storage through two processes (biosynthesis of plant biopolymers and soil metabolism) remains poorly understood. Here, we utilized transcriptome analysis to examine the effects of AMF on P. communis roots. Under the AM symbiosis, root morphological growth and tolerance to stress were strengthened, and the biosynthetic pathways of key plant biopolymers (long-chain fatty acids, cutin, suberin, and lignin) contributing to the plant-derived C were enhanced. In the subsequent metabolic processes, AMF increased soil metabolites contributing to plant-derived C (such as syringic acid) and altered soil metabolic pathways, including carbohydrate metabolism. Additionally, C-acquiring soil extracellular enzyme activities were enhanced by AMF, which could affect the stabilization of plant-derived C in soil. The contents of POC (21.71 g kg−1 soil), MAOC (10.75 g kg−1 soil), and TOC (32.47 g kg−1 soil) in soil were significantly increased by AMF. The concentrations of plant-derived C and microbial-derived C were quantified based on biomarker analysis. AMF enhanced the content of plant-derived C in both POC and MAOC fractions. What's more, plant-derived C presented the highest level in the POC fraction under the AMF treatment. This research broadens our understanding of the mechanism through which plant-derived C contributes to the accumulation of POC and SOC induced by AM symbiosis, and evidences the benefits of AMF application in SOC sequestration.

Synergistic Promotion of Particulate and Mineral-Associated Organic Carbon Within Soil Aggregates After 10 Years of Organic Fertilization in Wheat-Maize Systems

How different fertilization practices modify soil organic carbon (SOC) sequestration is still unclear. Our study aimed to evaluate the changes in SOC stocks and their physical fractions after 10 years of organic and inorganic fertilization. Five treatments were established under a wheat-maize system in Northern China: control (CK), chemical fertilizer (F), straw plus chemical fertilizer (SF), manure plus chemical fertilizer (MF), and straw and manure plus chemical fertilizer (SMF). The results showed that the SOC sequestration rate at 0–20 cm depth decreased in the following order: SMF (1.36 Mg C/ha/yr) > MF (1.13 Mg C/ha/yr) > SF (0.72 C/ha/yr) > F (0.15 Mg C/ha/yr) > CK (−0.25 Mg C/ha/yr). The values indicated that straw returning and manure application were important measures to achieve the “4 per 1000” target, and the application of manure was a more effective strategy. The high input of chemical fertilizer only maintained the initial SOC level and was not a powerful C-farming practice. A minimum input of 4.93 Mg C/ha/yr was required to keep the initial SOC storage. The SOC associated with small macroaggregate (0.25–2 mm) was the most sensitive indicator for the changes of bulk SOC. In addition, the accumulation of SOC under SMF, MF, and SF treatments mainly occurred in the occluded particulate organic C (oPOC) in small macroaggregates, indicating that the physical protection of macroaggregates played a predominant role in SOC sequestration. The SMF, MF, and SF treatments also displayed higher mineral organic C (mSOC) in soil aggregates than the CK and F treatments. A transformation of oPOC towards the mSOC fraction indicated that exogenous C further shifted into stable C pools under the physical protection of soil aggregates. In conclusion, these findings confirmed the important role of straw returning and manure application in SOC accumulation and stabilization, highlighting that a combination strategy of straw + manure + chemical fertilizer had the best effect.

How do reactive aluminum and iron phases control soil organic carbon and phosphate adsorption capacity in agricultural topsoils across Japan?

ABSTRACT The growing number of studies suggests that the prediction of soil organic carbon (SOC) storage and persistence can be improved by accounting for variations in soil reactive metal phases. Nevertheless, the dataset on reactive metals is often limited at a national scale. In Japan, the phosphate adsorption coefficient (PAC) has been measured for agricultural soils nationwide. PAC is known to be strongly controlled by reactive metals, and hence, it can be used as a surrogate for reactive metal content. However, the relationships between SOC, reactive metals and PAC across a wide range of agricultural soils remain unclear. We thus examined these relationships using agricultural topsoils taken from 115 sites across Japan, covering two major soil great groups, Andosols and Lowland soils, as well as various land uses and soil temperature regimes (7.2–19.1°C). For the whole dataset, PAC was strongly correlated with oxalate-extractable metals (Alox + 0.5Feox: Metalox, r = 0.83) and moderately with pyrophosphate-extractable metals (Alp + 0.5Fep: Metalp, r = 0.68). These results suggest a stronger contribution of short-range-order (SRO) minerals to PAC as the former parameter reflects the content of both SRO minerals and organically complexed metals, while the latter reflects only that of organo-metal complexes. Moreover, Metalp was the best predictor of SOC contents in both Andosols (r = 0.79) and Lowland soils (r = 0.65). When only soils at near neutral soil pH range were considered, the exchangeable Ca content also co-varied with SOC in Lowland soils (n = 17). Of the two metallic elements, reactive Al phases better explained the variation of SOC and PAC in Andosols, whereas reactive Fe phases also showed similar explanatory power for PAC in Lowland soils. Our analyses also suggested that soil group (esp. erosion intensity) and land use likely impacted the SOC-Metalox relationship in Andosols, whereas environmental factors such as soil temperature and soil redox regime affected those relationships in Lowland soils. Overall, we showed that PAC is a useful surrogate for SRO minerals and organo-metal complexes and, with careful considerations of the environmental and pedogenic factors, it is potentially useful to estimate the amounts of SOC stabilized by reactive metal phases in agricultural soils across Japan.

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.

Lifting the Profile of Deep Forest Soil Carbon

Forests are the reservoir for a vast amount of terrestrial soil organic carbon (SOC) globally. With increasing soil depth, the age of SOC reportedly increases, implying resistance to change. However, we know little about the processes that underpin deep SOC persistence and what deep SOC is vulnerable to climate change. This review summarizes the current knowledge of deep forest SOC, the processes regulating its cycling, and the impacts of climate change on the fate of deep forest SOC. Our understanding of the processes that influence deep SOC cycling and the extent of SOC stores is limited by available data. Accordingly, there is a large degree of uncertainty surrounding how much deep SOC there is, our understanding of the influencing factors of deep SOC cycling, and how these may be distinct from upper soil layers. To improve our ability to predict deep SOC change, we need to more accurately quantify the deep SOC pool and deepen our knowledge of how factors related to the tree root–soil–microbiome control deep SOC storage and cycling. Thereby, addressing the uncertainty of deep SOC contribution in the global C exchange with climate change and concomitant impacts on forest ecosystem function and resilience.

Land use effects on soil microbiome composition and traits with consequences for soil carbon cycling

Abstract The soil microbiome determines the fate of plant-fixed carbon. The shifts in soil properties caused by land use change leads to modifications in microbiome function, resulting in either loss or gain of soil organic carbon (SOC). Soil pH is the primary factor regulating microbiome characteristics leading to distinct pathways of microbial carbon cycling, but the underlying mechanisms remain understudied. Here, the taxa-trait relationships behind the variable fate of SOC were investigated using metaproteomics, metabarcoding and a 13C labelled litter decomposition experiment across two temperate sites with differing soil pH each with a paired land use intensity contrast. 13C incorporation into microbial biomass increased with land use intensification in low pH soil but decreased in high pH soil, with potential impact on carbon use efficiency (CUE) in opposing directions. Reduction in biosynthesis traits was due to increased abundance of proteins linked to resource acquisition and stress tolerance. These trait trade-offs were underpinned by land use intensification-induced changes in dominant taxa with distinct traits. We observed divergent pH-controlled pathways of SOC cycling. In low-pH soil, land use intensification alleviates microbial abiotic stress resulting in increased biomass production but promotes decomposition and SOC loss. In contrast, in high-pH soil, land use intensification increases microbial physiological constraints and decreases biomass production, leading to reduced necromass build-up and SOC stabilisation. We demonstrate how microbial biomass production and respiration dynamics and therefore CUE can be decoupled from SOC highlighting the need for its careful consideration in managing SOC storage for soil health and climate change mitigation.

Land use change and ecosystem service tradeoffs on California agricultural land

Abstract Introduction &amp;#xD;The need to transition to sustainable agricultural practices while maintaining high food yield and strengthening resilience to climate change cannot be overstated. California farmers have received incentive funding from federal and state agencies to use land management practices that are less impactful to the land and in line with California’s sustainability goals. However, there are no regional monitoring measures to determine whether farming is becoming more sustainable. &amp;#xD;&amp;#xD;Methods &amp;#xD;In this study, we used land cover change analysis and ecosystem services modeling to understand how farming practices influence environmental benefits on California farmland from 2010 to 2020. We analyzed the tradeoffs between soil erosion control, soil carbon storage, and production of California’s top agricultural commodities, and we compared these changes to changes in land cover in five agricultural regions statewide. &amp;#xD;&amp;#xD;Results and Conclusion &amp;#xD;We found that the trade-offs in ecosystem services and food production differ depending on the regional context, and that major expansion in almond production and land use changes have had different impacts throughout California. Statewide, soil organic carbon storage increased, soil erosion control increased slightly, and food production boomed for most commodities. Incentive programs that influence farming practices may need to operate at a regional level rather than a statewide level to achieve sustainable outcomes specific to each region.&amp;#xD;

Unraveling the impact of global change on glomalin and implications for soil carbon storage in terrestrial ecosystems

Glomalin-related soil protein (GRSP) is a potential byproduct of arbuscular mycorrhizal fungi (AMF) and a major contributor to the passive soil organic carbon (SOC) pool. Despite its crucial role in SOC storage, we know little about the response of GRSP to anthropogenic global change factors (GCFs). Here, using 530 observations from 107 primary studies, we conducted a global meta-analysis to unravel the effects of multiple GCFs (climate change, plant invasion (PI), wildfire, urbanization, land-use change (LUC), and nutrient addition (nitrogen; N, phosphorus; P, and potassium; K) on two functional GRSP fractions (easily extractable- (EE-) and total- (T-) GRSPs) in terrestrial ecosystems. We found that elevated carbon-dioxide increased T-GRSP by 28%, combined NP addition by 39.9%, and NPK addition by 29.5%. Climate warming and alone N addition increased EE-GRSP solely by 2.4% and 13.6%, respectively, but did not influence T-GRSP. However, urbanization and drought decreased T-GRSP by 26% and 15%, respectively. The LUC from natural ecosystems to cropland decreased T-GRSP by 40%, while afforestation in croplands increased it by 32%. Other GCFs (PI, wildfire, and P) had non-significant effects on GRSP probably because of (i) minor changes in AMF activity and (ii) the counterbalancing of effects by opposite processes. GCF impacts were robust when applied at higher intensities for medium-to-long durations (3–10＋ years) in humid conditions and clay-rich soils. The sandy soils experienced greater T-GRSP losses during LUC. Increases in T-GRSP were positively correlated with AMF-root colonization, soil mean-weight diameter, and SOC content. Further, our structure equation model confirmed that GCFs directly influence SOC by altering AMF-GRSP production and indirectly affecting soil aggregate formation and protection, suggesting that optimizing GRSP production can enhance SOC sequestration.

Bacterial and fungal keystone taxa play different roles in maintaining community resistance and driving soil organic carbon dynamics in response to Solidago Canadensis invasion

The invasion of alien plants has significant implications for vegetation structure and diversity, which could lead to changes in the carbon (C) input from vegetation and change the transformation and decomposition processes of C, thereby altering the dynamics of soil organic carbon (SOC) within ecosystems. Whether alien plant invasion increases the SOC stock and changes SOC fractions consistently within regional scales, and the underlying mechanisms driving these SOC dynamics remain poorly understood. This study investigated SOC dynamics by comparing the plots that suffered invasion and non-invasion of Solidago Canadensis across five ecological function areas in Anhui Province, China, considering climate, edaphic factors, vegetation, and soil microbes. The results demonstrated that the impact of S. Canadensis invasion on SOC storage was not consistent at each site in the 0–20 cm soil layer, as indicated by the range of SOC content (5.94–12.45 g kg−1) observed at non-invaded plots. Stable SOC exhibited similar response patterns with SOC to plant invasion, whereas labile SOC did not. In addition, bacterial and fungal communities were shifted in structure at each site by plant invasion. Bacterial communities exhibited greater resistance to S. Canadensis invasion than did fungal communities, as evidenced by three aspects of the resistance indices—community resistance, phylogenetic conservation, and network complexity. The mechanisms driving SOC dynamics under S. Canadensis invasion were explored using structural equation models. This revealed that fungal keystone taxa responsible for community resistance controlled stable SOC fractions. In contrast, bacterial keystone taxa had the opposite effect on labile and stable SOC. Climatic and edaphic factors were also involved in the labile and stable SOC dynamics. Overall, this study provides novel insights into the dynamics of SOC under S. Canadensis invasion on a regional scale.

Modelling and validating soil carbon dynamics at the long-term plot scale using the rCTOOL R package

We introduce rCTOOL, an open-source R package for carbon (C) turnover modelling, featuring comprehensive documentation and a user-friendly interface. As an enhanced version of the widely used Danish C-TOOL model, rCTOOL maintains minimal input data requirements and reliable performance, while addressing the original model's limitations in openness and documentation. To validate rCTOOL, we analysed topsoil Soil Organic Carbon (SOC) dynamics using data from the long-term Askov straw disposal experiment (1981–2019), which quantifies the impact of varying annual straw C inputs on SOC storage. Our validation shows an unbiased global prediction error of less than 10%, with a mean error of 1.1 Mg C/ha (CI -0.7–3.0 Mg C/ha). The discrepancies between observed and predicted values were primarily due to spatiotemporal variability represented by the block and year in the long-term field experiment. We demonstrate how rCTOOL is a reliable asset for diverse applications in SOC management and research.

Enhanced soil microbial stability is associated with soil organic carbon storage under high-altitude forestation

The potential of forestation to mitigate climate warming depends largely on whether it can improve terrestrial carbon (C) storage. Changes in soil microbial stability can cause ecosystem C fluctuations. Unfortunately, it remains unclear whether forestation alters soil microbial stability with cascading effects on C storage in high-altitude ecosystems. In this study, a total of 14 typical planted forests were selected on the Tibetan Plateau. We showed that high-altitude forestation, particularly with poplars, altered the microbial diversity and potentially improved the stability of soil microbial communities. These changes were associated with soil C accumulation and potentially positive feedback on soil organic C storage. Variations in the microbial community stability were mostly caused by changes in soil bulk density and dissolved organic C. Superior network stability was found in fungal community rather than bacterial community. Additionally, there were strong interactions between bacterial and fungal communities that influenced soil C storage. These findings contribute to understand the differences and relationships between bacteria and fungi in plantation soils. This work reveals the potential of high-altitude forestation to mitigate climate warming through insights into the microbial-mediated mechanisms responsible for soil C storage in high-altitude ecosystems.

Crop diversity significantly enhances soil carbon sequestration via alleviating soil inorganic carbon decline caused by rhizobium inoculation

Increasing crop diversity and nitrogen (N) fertilizer application have been identified as effective strategies for enhancing productivity and soil organic carbon (SOC) storage in agroecosystems. However, the impact of these management practices on soil inorganic carbon (SIC) in agroecosystems remains unclear. At present, we evaluated the effects of maize/faba bean intercropping, N application rates, and inoculation rhizobia of faba bean on SIC in the top 20 cm of soil depth using a 13-year crop diversity field experiment. Our results showed that the soil total carbon (TC) content increased significantly by 5.9 % and 7.0 % compared to faba bean monoculture and maize monoculture, respectively, after 13 years of continuous intercropping. Intercropping increased the pedogenic carbonate (PIC) content by 36.7 %, resulting in an 8.9 % higher SIC content compared to faba bean monoculture. Additionally, intercropping significantly reduced the dissolution of lithogenic carbonate (LIC) by 17.5 %, leading to a 7.6 % higher SIC content compared to maize monoculture. The formation of PIC was associated with an increase in soil available cations especially Ca2+ in intercropping. The conservation of LIC was related to the higher soil available Mg2+ in intercropping than monoculture. Faba bean inoculated with rhizobia significantly decreased SIC content due to soil acidification after 13 years of continuous cropping. Intercropping also significantly increased SOC and C3-derived SOC content compared to maize monoculture and increased C4-derived SOC content compared with faba bean monoculture. Soil organic carbon showed a positive correlation with SIC across all cropping systems, and the SOC fractions could affect the neoformation of PIC and dissolution of LIC. Our results demonstrate that intercropping can increase SIC content, which further promotes soil carbon sequestration. This study highlights the significance of increasing crop diversity on cropland carbon sequestration and provides practical implications for mitigating carbon emissions.

Forest stand and soil types determine soil organic carbon storage in the Middle Atlas region of Morocco using machine learning models

Forest stand and soil types determine soil organic carbon storage in the Middle Atlas region of Morocco using machine learning models

The effect of mosses on the relocation of SOC and total N due to soil erosion and percolation in a disturbed temperate forest

Forests cover one-third of the global land and are important components of carbon and nitrogen cycling. Anthropogenic disturbances, such as forest road systems or skid trails for timber harvesting, can dramatically change the nutrient cycling in these ecosystems. Skid trails increase soil erosion and thus the displacement of soil organic carbon (SOC) and total nitrogen (Nt). Additionally, runoff transports high amounts of dissolved organic carbon (DOC), which can have a negative impact on aquatic ecosystems. One of the most important countermeasures against soil erosion is the quick recolonization of vegetation. To date, the extent to which natural vegetation succession influences the relocation of SOC and Nt, and in particular the role of mosses in this context, has not been well investigated. This study investigates the influence of natural vegetation succession and in particular of mosses on the displacement process of SOC and Nt as well as DOC caused by soil erosion. To this end, we combine the results of a field study using in-situ rainfall simulations with small-scale runoff plots in skid trails of the Schönbuch Nature Park in southwestern Germany with the results of ex-situ rainfall simulation experiments with infiltration boxes containing the substrate from the respective skid trails. The eroded sediments of skid trails were on average enriched in SOC by 16% and in Nt by 35% compared to the original soil, which lead to a decrease of the C/N ratio in sediments. As vegetation succession progressed, the displacement of SOC and Nt was reduced, confirmed by a negative correlation between the enrichment ratios of SOC (ERSOC), Nt and total vegetation cover. However, mosses tended to reduce ERSOC more than vascular plants. Additionally, mosses significantly decreased DOC concentration in surface runoff compared to bare soils, while no difference in DOC concentration in percolated water could be observed. Future research should explore the role of mosses in the storage of SOC and Nt in the soil and their impact on soil stability. Thus, utilizing mosses could potentially minimize environmental impacts from soil disturbances in forests.

Crop Residue Biochar Rather Than Manure and Straw Return Provided Short Term Synergism Among Grain Production, Carbon Sequestration, and Greenhouse Gas Emission Reduction in a Paddy Under Rice‐Wheat Rotation

ABSTRACTReturn of crop residues directly as straw, animal manure, or biochar are recommended management options for biowaste recycling and soil organic carbon (SOC) maintenance in agriculture. However, to address the soil health challenges associated with soil degradation and climate change, it is critical to determine if or which of these different forms of crop residues could deliver a synergic improvement in SOC storage, emission reduction, and crop productivity following field application. In this study, maize straw in the form of air‐dried biomass (CS), manure via cattle digestion (CM), and biochar via pyrolysis (CB) was respectively amended once at a dose of 10 t C ha−1, in comparison to no maize straw addition (CK), in a paddy field under rice‐wheat rotation. Changes in soil properties, SOC storage, greenhouse gas (GHG) emissions, and rice/wheat yield were examined over two consecutive rice/wheat rotation cycles following soil amendment. The total rice grain yield considerably increased by 6% under CM and CB, while it reduced by 6% under CS compared to CK. Soil nutrient content persistently increased under CM and CB by 4.2% ~ 17% and 11% ~ 26% for total nitrogen, 26% ~ 61% and 20% ~ 53% for available P, and 2% ~ 82% and 30% ~ 115% for available K, respectively. Topsoil SOC storage increased considerably by 8% under CM and 20% under CB, while remained unchanged under CS, compared to CK. The total methane (CH4) and nitrous oxide (N2O) emissions were considerably increased by 7 folds and 15% under CS and 3.5 folds and 61% under CM, respectively, compared to CK. In contrast, these emissions considerably decreased under CB by 33% for CH4 and 29% for N2O. Consequently, the C emission efficiency considerably reduced under CS and CM but increased under CB over the two rotation cycles monitored. Moreover, the soil quality index (SQI) considerably improved under CM and CB but remained unchanged under CS compared to CK. Among the different forms of straw return, manure, and biochar, straw amendments differed considerably in their effects on C sequestration, GHG emissions, and crop productivity. Only biochar from crop residues synergistically improved these functions in the short‐term following application to paddy soil.