Factors Of Soil Organic Carbon Research Articles

Storage, pattern and driving factors of soil organic carbon in the desert rangelands of northern Xinjiang, north-west China

Storage, pattern and driving factors of soil organic carbon in the desert rangelands of northern Xinjiang, north-west China

Aridity affects soil organic carbon concentration and chemical stability by different forest types and soil processes across Chinese natural forests

Forest soils play a critical role in carbon (C) reservoirs and climate change mitigation globally. Exploring the driving factors of soil organic carbon (SOC) concentration and stability in forests on a large spatial scale can help us evaluate the role of forest soils in regulating C sequestration. Based on SOC quantification and solid-state 13C nuclear magnetic resonance spectroscopy, we investigated the SOC concentration and SOC chemical stability (indicated by alkyl-to-O-alkyl ratio and hydrophobic-to-hydrophilic ratio) in top 0–5 and 5–10 cm soils from 65 Chinese natural forest sites and explored their driving factors. Results showed that SOC concentration in 0–5 cm soils were highest in mixed forests but SOC chemical stability in 0–5 cm soils were highest in coniferous forests, while SOC concentration and chemical stability in 5–10 cm soil layers did not differ across forest types. SOC concentration in 0–5 cm was directly related to soil pH and soil bacterial diversity. Structural equation models showed that aridity indirectly affected SOC concentration in 0–5 cm by directly affecting soil pH. While SOC chemical stability in 0–5 cm soils was higher with increased aridity. According to the correlations, the potential mechanisms could be attributed to higher proportion of coniferous forests in more arid forest sites, lower relative abundance of O-alkyl C, higher MgO and CaO contents, and higher bacterial diversity in soils from more arid forest sites. Our study reveals the important role of aridity in mediating SOC concentration and chemical stability in top 0–5 cm soils in Chinese natural forests on a large-scale field investigation. These results will help us better understand the different mechanisms underlying SOC concentration and stability in forests and assess the feedback of forest SOC to future climate change.

Tracking the Effects of Mangrove Changes and Spartina alterniflora Invasion on Soil Carbon Storage: A Case Study of the Beibu Gulf of Guangxi, China

In order to clarify the long-term changes in mangroves in the Beibu Gulf of Guangxi and the carbon storage changes after the invasion of Spartina alterniflora (S. alterniflora) in the Dandou Sea area, the Continuous Change Detection and Classification (CCDC) algorithm combined with feature indices was first used to track the changes. Subsequently, the random forest algorithm was applied to classify each change segment, and then sampling was conducted based on the distribution of S. alterniflora in different invasion years. The results showed that the Kappa coefficient of the classification result of the latest change segment was 0.78. The rapid expansion of S. alterniflora, aquaculture pond construction, and land reclamation activities have led to changes in mangroves, causing a decrease in the area of the mangrove region. A total of 814.57 hectares of mangroves has been converted into other land-cover types, with most pixels undergoing one to two changes, and many of these changes were expected to continue until 2022. An analysis of the distribution characteristics and influencing factors of soil organic carbon (SOC) and soil organic carbon storage (SOCS) at different invasion stages revealed that SOC and SOCS were mainly influenced by soil bulk density, soil moisture content, and electrical conductivity. It was found that S. alterniflora had higher SOC content compared to the mudflats. With the increase in invasion years, S. alterniflora continuously increased the SOC and SOCS content in coastal wetlands.

Spatial distribution and driving factors of soil organic carbon in the Northeast China Plain: Insights from latest monitoring data

Soil organic carbon (SOC) is a critical component of soil fertility and plays a crucial role in the global carbon cycle. Despite the widespread reports of a decrease in SOC content and stock in the Northeast China Plain in recent decades, the current status and driving factors of its content and distribution are unclear. In this study, the surface soil (0–20 cm) SOC content data of 1920 sampling points within the Northeast China Plain covering an area of 2.6 × 105 km2 were obtained based on the Land Quality Geochemical Monitoring Network established in 2018. Random forest model and correlation analysis were used to identify the main driving factors of SOC distribution. The results showed that the SOC content, soil organic carbon density (SOCD), and soil organic carbon storage (SOCS) in the Northeast China Plain were 13.48 g·kg−1, 3.45 kg·C·m−2, and 898.95 Tg, respectively. SOC content in paddy land was the highest among different land use types, which reached 18.77 g·kg−1. SOC content showed strong spatial dependence and gradually increased from southwest to northeast in the monitoring area. The results of the random forest analysis showed that the SiO2, mean annual temperature, and Fe2O3 explained 39.4 %, 18.9 %, and 12.8 % of the spatial variation of SOC, respectively. Although the SOCS (0–20 cm) in the Northeast China Plain has decreased by 8.68 % in the last 40 years compared to the Second National Soil Survey (1980), it's important to note that the SOCS has transitioned from a decreasing trend between 1980 and 2006 to an increasing trend from 2006 to 2018.This study provides important information for decision-makers on the spatiotemporal changes of SOC and its driving factors in the Northeast China Plain, which has a great significance for soil carbon sequestration and the development of management strategies to maintain soil fertility.

Distribution characteristics and influencing factors of soil organic carbon in tidal flat wetland of central Jiangsu, China.

We measured winter and summer soil organic carbon (SOC) contents in two typical coastal wetlands, the Spartina alterniflora salt marsh and the non-vegetation mudflat, on the south side of the Chuandong River Estuary in Yancheng, Jiangsu Province. We investigated the spatiotemporal variations of soil organic carbon contents and its driving factors. The results showed that SOC content ranged from 0.75 to 2.38 g·kg-1 in the mudflat area and from 2.07 to 18.59 g·kg-1 in the S. alterniflora salt marsh area, showing a decreasing trend towards the sea. The SOC content in the S. alterniflora salt marsh area was approximately 2.5 to 3.5 times of that in the mudflat area. Within a depth range of 1 m, there was no vertical variation in SOC content in the mudflat area, but an increasing and then decreasing pattern in the S. alterniflora marsh area with the peak occurring in the depth range of 20 to 30 cm. Soil organic carbon content exhibited significant seasonal difference, with higher value in summer than in winter. The summer SOC content was 5% to 10% higher than that in winter in the S. alterniflora marsh area, while it was 43% higher in summer than in winter in the mudflat area. In the S. alterniflora marsh area, soil organic carbon content was positively correlated with soil moisture and salinity, but negatively correlated with sediment particle size. In contrast, there was no significant correlation between soil organic carbon content and soil physicochemi-cal factors in the mudflat area. Those results indicated that the correlation between various soil physicochemical factors and SOC is established on the basis of vegetation cover in coastal wetlands. Our findings could provide valuable insights for the conservation of blue carbon ecosystems in coastal wetlands in China.

Climate factors regulate the depth dependency of soil organic carbon under grazing exclusion in Chinese grasslands: A meta‐analysis

AbstractSoil carbon (C) is one of the most abundant C pools in terrestrial ecosystems, and its dynamics is highly dependent on soil depth. Grazing exclusion (GE) has proven to be a promising approach for enhancing C sequestration; however, the comprehensive analysis on the depth distribution of soil C and driving factors of soil C dynamics under GE are still lacking. This study collected data comprising 563 paired observations from 75 papers to analyze the distribution characteristics and the driving factors of soil organic carbon (SOC) changes with soil depth under GE in Chinese grasslands. The results showed that GE positively contributed to soil C sequestration, and the change range of SOC were higher (47.70%) in the subsoil (>20 cm) than in the topsoil layer (0–20 cm; 29.24%). Furthermore, SOC was influenced by GE duration, exhibiting an increasing trend and reaching its highest value at 13–15 years of GE, then remaining stable or slightly decreasing thereafter. Boosted regression trees (BRTs) showed that climatic factors were the primary determinants of SOC changes; however, the key drivers of SOC varied across different soil depths. Mean annual precipitation (MAP) was the key driver of topsoil C dynamics, accounting for 32.7% of the variance. In contrast, mean annual temperature (MAT) regulated the response of subsoil SOC to GE, explaining 48.23% of the variance. In addition, plant biomass was a significant factor influencing the depth distribution of soil C under GE, and its effect on SOC decreased with increasing soil depth. Our study provides evidence that the subsoil has a greater potential for C sequestration than the topsoil layer after GE, and future studies should consider deep soil C dynamics to accurately assess C sequestration in grassland ecosystems.

The Dominant Factor Affecting Soil Organic Carbon in Subtropical Phyllostachys edulis Forests Is Climatic Factors Rather Than Soil Physicochemical Properties

Phyllostachys edulis, also known as moso bamboo, is widely distributed in China, has strong carbon sequestration potential, and contributes significantly to carbon sinks at the regional scale. However, the distribution and influencing factors of soil organic carbon (SOC) are unclear in bamboo forests at the regional scale. We selected six sites in Phyllostachys edulis forests in the northern subtropics, middle subtropics, and southern subtropics of China to determine the SOC contents and estimate its stocks. The relationships between the SOC and geographic position, climate, vegetation, and the soil’s physical and chemical characteristics were analyzed via Pearson correlation coefficients. Structural equation modeling (SEM) was established to reveal the direct and indirect effects of all factors on the SOC. The SOC content significantly decreased with an increase in soil depth in the subtropics. The Pearson correlation analysis and structural equation modeling results indicated that the climate was closely related to and had the most significant effect on the SOC in moso bamboo forests. The maximum effect values of the annual mean temperature (MAT) and annual mean precipitation (MAP) on SOC were −0.975 and 0.510, respectively. Elevation and latitude were strongly correlated with Phyllostachys edulis forests and 0–10 cm SOC content and significantly contributed to the SOC with effect values of 0.488 and 0.240, respectively. The soil’s physical properties and forest biomass had significant negative effects on the SOC. Both NH4+-N and available phosphorus (SAP) were significantly and positively correlated with the SOC at different soil depths in moso bamboo forests to different degrees, but he soil’s chemical properties, in general, had no significant direct effect on the SOC.

Storage and controlling factors of soil organic carbon in alpine wetlands and meadow across the Tibetan Plateau

AbstractAlpine wetlands and meadows across the Three Rivers Source Region (TRSR) store high soil organic carbon (SOC). However, information on factors affecting SOC storage is scanty. Herein, we investigated SOC storage and explored factors affecting SOC storage, including climate, soil properties and above‐ and belowground biomass, using 50 soil profiles across the TRSR on the Tibetan Plateau. The SOC storage was 491.9 ± 158.5 Tg C and 545.2 ± 160.8 Tg C in the TRSR alpine wetlands and meadow, respectively. The SOC stock was positively correlated with the mean annual precipitation. However, no significant correlation between SOC stock and mean annual temperature was observed, as opposed to the global trend. In addition, SOC stock was positively correlated with both the aboveground biomass (AGB) and belowground biomass (BGB). Soil pH indirectly affected SOC stock, while SOC stock positively correlated with Al and Fe oxyhydroxides. Compared with vegetation biomass and climatic factors, soil properties, including soil pH and Al and Fe oxyhydroxides (Alo and Feo), affected not only SOC stock variation but also affected the impact of vegetation and climatic factors on SOC stock. Climate factors, AGB, BGB, soil pH, Alo and Feo jointly accounted for 59% of SOC stock variation in alpine wetlands and 64% of SOC stock variation in alpine meadow. This study suggests that soil properties are the dominant factors affecting SOC variation in alpine wetlands and meadow on the Tibetan Plateau.

Manuring improves soil health by sustaining multifunction at relatively high levels in subtropical area

As an effective field management practice for better crop productivity, fertilization showed profound impacts on soil health by altering soil chemical, physical, and biological processes. But, how soil health and related ecosystem multifunctionality (EMF) respond to long-term fertilization remains unclear. In this study, based on a 29-year field experiment, we evaluated soil health and EMF under chemical fertilization versus manure application. Long-term manure application maintained soil pH, significantly increased water-stable aggregate, total and available nutrients, microbial biomass and community (bacteria, fungi, and actinomycetes, etc.), and enzyme activities compared with treatments under chemical fertilizers. Edaphic factors of soil organic carbon (SOC), available phosphorous (AP), fungi, cation exchange capacity, and clay content were identified as key indicators of soil health evaluation by network analysis. The soil health indices (SHIs) of chemical fertilizer treatments were 39–52% lower than that of natural vegetation recovery, with carbon and nutrient cycling, soil biodiversity maintenance, and productivity at low ecosystem function levels. Manure application enhanced soil health by 150–196% compared to unfertilized control by improving SOC, P availability, and sustaining ecosystem functions with carbon and nutrient cycling, soil biodiversity maintenance, buffering and filtering capacity, and productivity at relatively high ecosystem function levels. The individual functions of carbon and nutrient cycling, physical structure stability, and productivity illustrated sensitive responses to the increase in soil health, while inherent soil functions of buffering and filtering capacity and soil biodiversity maintenance were only correlated with high soil health. Manuring improved soil functions and soil health simultaneously, indicating a synergistic relationship. Our findings highlight the significance of manure application to improve soil health and sustain functions in intensive agricultural systems.

Spatial Distribution Characteristics and Influencing Factors of Soil Organic Carbon Density in Yellow River Basin Based on MGWR Model

As the largest terrestrial carbon pool, the spatial distribution characteristics and influencing factors of soil organic carbon have important implications for global carbon cycle processes. Soil organic carbon density (SOCD) and influencing factors were predicted in the Yellow River basin using a mixed geographically weighted regression (MGWR) model based on soil organic carbon density data and environmental factors. The results showed that:① the SOCD ranged from 0-14.82 kg·m-2 and 0-32.39 kg·m-2 for the soil depths of 0-20 cm and 0-100 cm, with mean values of 3.48 kg·m-2 and 8.07 kg·m-2 and reserves of 2.76 Pg and 6.48 Pg, respectively. The high SOCD value areas were mainly located in the southern part of the Qinghai-Tibet Plateau and Loess Plateau, and the low value areas were located in the eastern part of the upper Yellow River and the inland flow area. ②Among the ecosystem types, the SOCD of soil depth in 0-20 cm was in the descending order of:forest>water body and wetland>other>grassland>farmland>settlement>desert, with mean values of 4.52, 4.31, 3.84, 3.73, 2.89, 2.78, and 2.22 kg·m-2, respectively, and the SOCD of the 0-100 cm soil depth was in the descending order of:water bodies and wetlands>forest>other>grassland>farmland>settlement>desert, with mean values of 9.58, 9.58, 8.85, 8.66, 7.07, 6.81, and 5.29 kg·m-2, respectively. The SOCR in descending order was:grassland>farmland>forest>desert>water bodies and wetlands>settlement>others, with 1.40, 0.60, 0.47, 0.11, 0.07, 0.06, and 0.05 Pg at a soil depth of 0-20 cm and 3.31, 1.49, 0.99, 0.26, 0.17, 0.14, and 0.12 Pg at a soil depth of 0-100 cm, respectively. ③ The main factors affecting the SOCD distribution were intercept, profile curvature, NDVI, and precipitation; in addition, curvature and silt also had important effects on the deep SOCD distribution in the Yellow River basin. Among the ecosystem types, precipitation and NDVI were the main factors affecting the SOCD distribution. The intercept also had important effects on the SOCD distribution in the all ecosystems except forests, whereas curvature and silt only had important effects on deserts and other ecosystems. These results revealed the spatial distribution of SOCD, influencing factors, and SOCR in the Yellow River basin and can provide a scientific basis for carbon balance, soil quality evaluation, and ecological management restoration and consolidation in the region.

Shapley values reveal the drivers of soil organic carbon stock prediction

Abstract. Insights into the controlling factors of soil organic carbon (SOC) stock variation are necessary both for our scientific understanding of the terrestrial carbon balance and to support policies that intend to promote carbon storage in soils to mitigate climate change. In recent years, complex statistical and algorithmic tools from the field of machine learning have become popular for modelling and mapping SOC stocks over large areas. In this paper, we report on the development of a statistical method for interpreting complex models, which we implemented for the study of SOC stock variation. We fitted a random forest machine learning model with 2206 measurements of SOC stocks for the 0–50 cm depth interval from mainland France and used a set of environmental covariates as explanatory variables. We introduce Shapley values, a method from coalitional game theory, and use them to understand how environmental factors influence SOC stock prediction: what is the functional form of the association in the model between SOC stocks and environmental covariates, and how does the covariate importance vary locally from one location to another and between carbon-landscape zones? Results were validated both in light of the existing and well-described soil processes mediating soil carbon storage and with regards to previous studies in the same area. We found that vegetation and topography were overall the most important drivers of SOC stock variation in mainland France but that the set of most important covariates varied greatly among locations and carbon-landscape zones. In two spatial locations with equivalent SOC stocks, there was nearly an opposite pattern in the individual covariate contribution that yielded the prediction – in one case climate variables contributed positively, whereas in the second case climate variables contributed negatively – and this effect was mitigated by land use. We demonstrate that Shapley values are a methodological development that yield useful insights into the importance of factors controlling SOC stock variation in space. This may provide valuable information to understand whether complex empirical models are predicting a property of interest for the right reasons and to formulate hypotheses on the mechanisms driving the carbon sequestration potential of a soil.

Variations and influencing factors of soil organic carbon during the tropical forest succession from plantation to secondary and old–growth forest

IntroductionSoil organic carbon (SOC) accumulation changed with forest succession and hence impacted the SOC storage. However, the variation and underlying mechanisms about SOC during tropical forest succession are not fully understood.MethodsSoil samples at four depths (0–10 cm, 10–20 cm, 20–40 cm and 40–60 cm), litter, and roots of 0–10 cm and 10–20 cm were collected from three forest succession stages (plantation forest, secondary forest, and old– growth forest) in the Jianfengling (JFL) National Nature Reserve in Hainan Island, China. The SOC, soil enzyme activities, physiochemical properties, the biomass of litter and roots were analyzed.ResultsResults showed that forest succession significantly increased SOC at 0–10 cm and 10–20 cm depth (from 23.00 g/kg to 33.70 g/kg and from 14.46 g/kg to 22.55 g/kg, respectively) but not at a deeper depth (20–60 cm). SOC content of the three forest succession stages decreased with increasing soil depth and bulk density (BD). With forest succession from plantation to secondary and old–growth forest, the soil pH at 0–10 cm and 10–20 cm depth decreased from 5.08 to 4.10 and from 5.52 to 4.64, respectively. Structural equation model (SEM) results showed that the SOC at depths of 0–20 cm increased with total root biomass but decreased with increasing soil pH value. The direct positive effect of soil TP on SOC was greater than the indirect negative effect of decomposition of SOC by soil acid phosphatase (AP).DiscussionTo sum up, the study highlighted there was soil P– limited in tropical forests of JFL, and the increase in TP and total root biomass inputs were main factors favoring SOC sequestration during the tropical forest succession. In addition, soil acidification is of great importance for SOC accumulation in tropical forests for forest succession in the future. Therefore, forest succession improved SOC accumulation, TP and roots contributed to soil C sequestration.

Spatial-temporal variations and driving factors of soil organic carbon in forest ecosystems of Northeast China

Forest soil carbon is a major carbon pool of terrestrial ecosystems, and accurate estimation of soil organic carbon (SOC) stocks in forest ecosystems is rather challenging. This study compared the prediction performance of three empirical model approaches namely, regression kriging (RK), multiple stepwise regression (MSR), random forest (RF), and boosted regression trees (BRT) to predict SOC stocks in Northeast China for 1990 and 2015. Furthermore, the spatial variation of SOC stocks and the main controlling environmental factors during the past 25 years were identified. A total of 82 (in 1990) and 157 (in 2015) topsoil (0–20 ​cm) samples with 12 environmental factors (soil property, climate, topography and biology) were selected for model construction. Randomly selected 80% of the soil sample data were used to train the models and the other 20% data for model verification using mean absolute error, root mean square error, coefficient of determination and Lin's consistency correlation coefficient indices. We found BRT model as the best prediction model and it could explain 67% and 60% spatial variation of SOC stocks, in 1990, and 2015, respectively. Predicted maps of all models in both periods showed similar spatial distribution characteristics, with the lower SOC in northeast and higher SOC in southwest. Mean annual temperature and elevation were the key environmental factors influencing the spatial variation of SOC stock in both periods. SOC stocks were mainly stored under Cambosols, Gleyosols and Isohumosols, accounting for 95.6% (1990) and 95.9% (2015). Overall, SOC stocks increased by 471 ​Tg ​C during the past 25 years. Our study found that the BRT model employing common environmental factors was the most robust method for forest topsoil SOC stocks inventories. The spatial resolution of BRT model enabled us to pinpoint in which areas of Northeast China that new forest tree planting would be most effective for enhancing forest C stocks. Overall, our approach is likely to be useful in forestry management and ecological restoration at and beyond the regional scale.

Fractions, stability, and influencing factors of soil organic carbon under different land-use in sodic soils

Salt-affected soils have considerable carbon sequestration potential in aboveground biomass and soil organic carbon (SOC). However, organic carbon pool characteristics and the significant important factors affecting the land use of sodic soils have not been clearly elucidated. In this study, 252 samples were collected from 20 typical sodic soil sites across the western Songnen Plain, China. This study investigated the effects of five land-use types, that is, saline wasteland (SWL), degraded grassland (GL), forestland (FL), upland (UL), and paddy fields (PF), on sodic soil SOC fractions and stabilities to find that UL and PF decreased salinity and alkalinity, but increased soil nutrient and water stability aggregate (WSA) contents and stability. Compared with degraded natural land-use types (SWL and GL), FL and croplands (UL and PF) increased the physical protection of SOC and aggregate-associated SOC contents. Furthermore, cropland, especially PF, increased nonlabile organic carbon (NOC) (7.47 g kg−1), labile organic carbon (LOC) (3.79 g kg−1), dissolved organic carbon (DOC) (0.16 g kg−1), and mineralizable organic carbon (MOC) (0.41 g kg−1) fractions. Furthermore, compared with degraded natural lands, PF increased NOC ratios (59.65%) and carbon management index (CMI) (126.1), thus increasing organic carbon content and stability. Structural equation modelling revealed that improvements in soil properties, total nitrogen (TN), WSA, electrical conductivity (EC), and pH were the crucial factors for increasing SOC stock in sodic soils. We concluded that the positive effect that PF had on SOC content and stability were much greater than that of the other land-use types, and that PF was the optimal management practice for increasing SOC sequestration capacity in sodic soils.

Spatial variations and influencing factors of soil organic carbon under different land use types in the alpine region of Qinghai-Tibet Plateau

Understanding soil organic carbon (SOC) distribution and influencing factors are important to accurately assess soil carbon sink potential and ecosystem quality. However, variations and controls of SOC content and stock under various land use types in the alpine region of Qinghai-Tibetan Plateau remain challenging. In this study, soil properties (pH, bulk density, porosity, clay content, soil organic carbon, soil water content, total nitrogen, total phosphorus, available nitrogen and available phosphorus) and environmental parameters (annual average temperature, annual average rainfall, normalized differential vegetationindex, altitude, slope, surface roughness, longitude and latitude) were determined across a 600 km east–west transect in the Tibet alpine region for investigating the distribution characteristics and controls of SOC for three land use patterns — farmland (FA), forestland (FO) and grassland (GR). Results indicated that SOC content in the 0–30 cm decreased with increasing soil depth at different reduction rates under various land use types. The average SOC content and stock in GR was significantly higher than that in FO and FA due to the existence of mattic epipdon in GR under high altitude. The non-consideration of gravel content in soil can lead to an overestimation of SOC stock of 0–30 cm soil layer by 15.37 %, 16.70 % and 17.43 % for FA, FO and GR, respectively. Soil properties and environmental conditions simultaneously affect the spatial distribution of SOC under various land use patterns. Pedotransfer functions (PTFs) using multiple regression were used to forecast SOC content in the studied alpine region, which had a better predictive performance than previous published PTFs in the plain area, especially when SOC contents were higher than 40 g kg−1. Our study provides a foundation to build SOC prediction models for other alpine regions in the world, where SOC contents generally exhibit a wider range than the plain areas.

Effects of Spartina alterniflora Invasion on Soil Organic Carbon Storage in the Beihai Coastal Wetlands of China

The invasion of Spartina alterniflora (S. alterniflora) has changed the carbon cycle process of local ecosystems. In order to clarify the effect of S. alterniflora invasion on coastal soil carbon pool in Northern Beibu Gulf, the distribution characteristics and influencing factors of soil organic carbon (SOC) and SOC storage (SOCS) at different intrusion stages were investigated and analyzed. The results showed that the SOC content in S. alterniflora wetlands (2.65–21.54 g/kg) was higher than that in mudflats (0.85–1.19 g/kg). SOC content in 0–20 cm depth was highest than that in 20–40 cm and 40–60 cm depth. The total SOCS increased by 72.11%, 78.45%, 77.56%, 80.42%, and 90.63% in 3a, 12a, 15a, 16–19a, and 26a compared with mudflats, respectively. S. alterniflora invasion increased SOC and SOCS both in surface soil and deep soil. SOCS increased rapidly during the initial stage of invasion, and remained in a relatively stable and continuous growth state after 12–15 years. The distributions and accumulation of SOC and SOCS were affected mainly by soil texture, soil bulk density, moisture content, total nitrogen and total phosphorus. The source of SOC from S. alterniflora was increasing with invasion ages and would be mainly input in 26a, while marine sources was mainly imported in other invasion ages. Our data indicated that S. alterniflora continuously enhances the SOC sequestration over the years in coastal wetland ecosystems.

Identifying the scale-controlling factors of soil organic carbon in the cropland of Jilin Province, China

Soil organic carbon (SOC) is the largest and most important terrestrial carbon pool, and it can influence global environmental management and food security. However, the spatial variability of SOC in cultivated areas and the relative controlling factors that drive the variations across different spatial scales are still not clear. On the basis of 2745 soil samples collected during 2006–2011, the spatial variability of SOC was first obtained from all of Jilin Province. Then, five categories of predictors, including climate, topography, soil, vegetation, and management practice, were selected to establish the environmental datasets at seven target scales (500 m, 1 km, 2.5 km, 5 km, 10 km, 25 km, and 50 km). Last, a machine learning method (random forest) was used to analyze the scale behaviors of these predictors on SOC variations. The results showed that the SOC content in Jilin Province had a moderate spatial dependence. Across all seven scales, elevation, precipitation, and temperature-related variables always had an important impact on SOC variation. Topography-related predictors had higher importance (relative importance (RI): 30.76%–44.20%) at the 1 km to 50 km scale, especially in the eastern humid mountainous ecoregion, while management practices had the largest importance (RI: 19%–29.20%) at the 500 m to 2.5 km scale in the central semihumid plain ecoregion. For the western semiarid plain, precipitation had higher importance (RI: 18.88%–23.68%) across all seven scales. Understanding the scale behaviors of environmental factors on SOC variations will be useful for improving soil health, food security and global environmental management.

Distribution and influencing factors of soil organic carbon in a typical karst catchment undergoing natural restoration

Understanding the distribution patterns and controlling factors of soil organic carbon (SOC) in karst areas is important for soil carbon management. However, due to the wide variety of human activities and karst habitats, the factors influencing SOC in karst areas vary. A typical catchment undergoing natural restoration in the karst region of South China was investigated to determine the distribution and variation of soil properties and SOC stocks (SOCSs) under three types of terrain: a hillslope, a depression and a sinkhole. The factors influencing SOC under the different terrain types were determined by redundancy analysis and multiple linear regression modelling. The results indicated that terrain and hydrological conditions affect the distribution of SOC on the hillslope. The spatial heterogeneity of SOC and dissolved organic carbon (DOC) on the hillslope was high. Terrain type and land use differences significantly affected the SOC and DOC concentrations at the catchment scale. SOC loss was more serious in the depression due to agricultural activities, and SOC accumulation was more obvious on the hillslope due to its relatively long natural restoration period. The average SOCSs of the hillslope were 16.5% and 54.6% larger than those of the depression and sinkhole, respectively, and the average dissolved organic carbon stocks (DOCSs) were 70.6% and 179.7% larger, respectively. In addition, the impacts of environmental factors on SOC and DOC varied among the different terrain types. Soil texture and topography were the main factors controlling the distribution of SOC and DOC on the hillslope and in the whole catchment, and soil texture was the main factor controlling SOC at the catchment scale. In addition, soil loss through sinkholes may be an important carbon sink in karst areas. The results of this study are of great significance for evaluating soil carbon storage and vegetation restoration strategies in karst areas.

Controlling factors of soil organic carbon and nitrogen in lucerne grasslands in a semiarid environment

Lucerne (Medicago sativa L.) is one of the most successfully introduced species for revegetation on the Loess Plateau of China and provides important ecosystem services. However, the driving mechanism of soil organic carbon (SOC) and total nitrogen (TN) in lucerne grasslands remains unclear. This study explored the controlling factors of SOC and TN in lucerne grasslands in the semiarid Loess Plateau. A total of 112 quadrats were employed in 28 lucerne fields. Vegetation characteristics, topographic factors, and soil properties at a 0–20 cm depth were measured in each quadrat. The SOC and TN contents increased with altitude and showed positive correlations with species richness, aboveground biomass of native plants, soil moisture, soil inorganic nitrogen, total soil phosphorus (P), and C:P and N:P ratios. Variations in SOC and TN contents were mainly attributed to soil resources, followed by the interaction of topography, vegetation and soil. Soil P, soil moisture, altitude, and native plant species were the main factors controlling SOC and TN contents in these lucerne grasslands. Results suggest that specific abiotic (soil P and moisture) and biotic (plant species diversity) factors controlled SOC and TN in semiarid lucerne grasslands. These factors should be included in SOC and TN evaluation models to predict the future terrestrial ecosystem carbon and nitrogen dynamics.

植被修复初期对贵州高原喀斯特湿地湖滨带碳元素的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 植被修复初期对贵州高原喀斯特湿地湖滨带碳元素的影响 DOI: 10.5846/stxb202108302443 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 贵州省科技计划项目（黔科合基础-ZK[2021]一般099） Influence of vegetation restoration on carbon in the lakeside zone of Karst Wetland in Guizhou Plateau Author: Affiliation: Fund Project: Effects of vegetation succession on occurrence characteristics and release contributions of organic carbon: a case study at Caohai, Guizhou, SW China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以贵州草海保护区（海拔约为2171.7 m）为研究对象，采用时空互代法研究不同地貌环境（非喀斯特地貌、喀斯特地貌及植被修复地貌）下，保护区内土壤有机碳（SOC）、易氧化有机碳（ROC）、可溶性有机碳（DOC）含量分布规律及其影响因素，以期为准确估算保护区内碳组分储量及其固碳效益评价提供科学依据。结果表明：（1）不同地貌下有机碳（SOC）含量、易氧化有机碳（ROC）和可溶性有机碳（DOC）与土层深度存在极显著负相关关系，即随土层深度增加而降低；（2）在0-50 cm土层中喀斯特地貌与非喀斯特地貌下土壤团聚体均以>0.2 mm粒级有机碳含量相对较高，<0.125 mm粒级含量最低。（3）植被恢复过程中，土壤碳组分含量显著增加，土壤固碳能力增强提高了土壤有机碳含量，促进了土壤团聚体的形成，同时也提高了土壤团聚体的稳定性。 Abstract:This paper takes Guizhou Caohai Reserve (2171.7 m above sea level approximately) as the research object, the time-space substitution method was used to study the distribution and influencing factors of soil organic carbon (SOC), easily oxidizable organic carbon (ROC) and soluble organic carbon (DOC) in different geomorphological environments (non-karst landforms, karst landforms and vegetation restoration landforms). The purpose of this paper is to provide a scientific basis for accurately estimating the reserves of carbon components and evaluating the benefits of carbon sequestration in the reserve.The results showed that:(1) The contents of SOC, ROC and DOC,under different landforms had very significantly negative correlation with soil depth, that was, they decreased with the increase of soil depth. (2) In the 0-50 cm soil layer, both karst and non-karst landforms had relatively higher organic carbon content in soil aggregates larger than 0.2 mm, and the lowest content of smaller than 0.125 mm. (3) During the process of vegetation restoration, the content of soil carbon components increased significantly, and the enhancement of soil carbon sequestration capacity increased soil organic carbon content, promoted the formation of soil aggregates, and also improved the stability of soil aggregates. 参考文献 相似文献 引证文献