Areas Of Southern China Research Articles

Study of the Shear Strength Model of Unsaturated Soil in the Benggang Area of Southern China

Benggangs are a unique type of soil erosion commonly found in southern China, with the gully wall being the most dynamic component of the Benggang system and is crucial for assessing its overall progression. The unsaturated shear strength of soil in Benggang areas is a key factor influencing the stability of the gully wall. However, quantitative analyses of the unsaturated shear strength in the gully walls of Benggangs remain limited. In this study, the soil–water characteristic curves (SWCC) and shear strengths of undisturbed soil samples from four different soil layers in the gully wall of Benggang were measured using a pressure membrane meter and a quadruple direct shear apparatus. The results revealed that the water holding capacity of the soil decreased gradually with increasing matrix suction, and the order of the water holding capacity was the sandy soil layer > transition layer > laterite layer > clastic layer. With an increasing soil water content (SWC), the shear strength, cohesion (c), and internal friction angle (φ) of the four soil layers decreased significantly, and the φ showed a power function decreasing curve (p < 0.05), whereas c in the laterite layer and transition layer exhibited a power function decreasing curve (p < 0.01). The c of the sandy soil layer and clastic layer decreased linearly and logarithmically (p < 0.01) with increasing SWC, respectively. The unsaturated shear strength model for the four soil layers was developed based on the Vanapalli model. The root mean square error (RMSE) of the simulated and measured values was less than 29.349, while the Nash–Sutcliffe efficiency (NSE) and R2 values were greater than 0.638 and 0.788, respectively. The model can be used to analyze and predict the unsaturated shear strength in different layers of Benggang gully walls, providing a theoretical foundation for studying the erosion mechanisms of Benggangs.

Rare Earth Elements Induce Drought Tolerance in Dicranopteris pedata from Ion-Adsorbed Rare Earth Mining Area in Southern China

The ion adsorption rare earth (IARE) mining areas in southern China frequently experience severe seasonal drought, posing significant challenges to plant growth. This study investigates the hypothesis that rare earth elements (REEs) present in these mining areas induce drought resistance in Dicranopteris pedata (D. pedata). An experiment was designed with three drought stress intensities (0%, 5%, and 10% PEG6000) and three levels of rare earth element (REE) addition (none, low, and high). After 72 h of drought stress, physiological indices and metabolomic profiles of D. pedata were examined. The results showed that under drought conditions, the REE additions increased the catalase and peroxidase activities of D. pedata by 99.04% and 81.25%, respectively, and the contents of proline, soluble proteins, and soluble sugars by 97.52%, 71.24%, and 61.81%, respectively. Metabolomic analysis revealed up-regulation of lipid and lipid-like molecules, as well as flavonoid metabolism, which contribute to improved drought resistance in D. pedata under stress. Furthermore, REE addition further up-regulated flavonoid and anthocyanin synthesis compared to drought stress alone, enhancing the plant’s resilience to drought. These findings suggest that D. pedata responds to drought stress by modulating enzyme activities, osmoregulatory substances, and metabolic pathways upon REE exposure. This study underscores the dual role of REEs in enhancing both the drought tolerance and enrichment capacity of D. pedata in IARE mining areas, which is crucial for sustaining plant growth amidst drought stress, and provides new ideas for the ecological restoration and sustainable development of IARE mining areas.

Coupling Relationship Between Soil Properties and Plant Diversity Under Different Ecological Restoration Patterns in the Abandoned Coal Mine Area of Southern China.

Understanding the effects of ecological restoration in abandoned coal mines on soil and plant is important to improve the knowledge of ecosystems evolution and facilitate taking appropriate ecological restoration management practices. This study aims to evaluate the coupling relationship between plant diversity and soil properties after ecological restoration in abandoned coal mine area. The plant diversity such as Margalef index (M), Simpson index (H), Shannon-Wiener index (D), and Pielou index (J), and soil properties such as soil pH, soil water content (SWC), soil bulk density (SBD), soil organic matter (SOM), available nitrogen (AN), and microbial biomass carbon (MBC) were investigated in four sites of different ecological restoration patterns, Tand study the coupling relationship between them. The results indicated that: (1) the Pinus massoniana and Schima superba gardner and champ restoration (PSR) site had higher Shannon-Wiener index and Simpson index values than Pinus massoniana restoration (PR) site, and in herb layer, the plant diversity was significantly higher than in other layers; (2) in the PSR site, the soil properties were improved more notably than that of PR and nature restoration (NR) sites, and the plant diversity were also higher than PR site; (3) Clay, SOM, and MBC made a great contribution to the plant diversity. It was concluded that ecological restoration patterns had significant effects on soil nutrient content and plant diversity, and there exists evident coupling relationship between plant diversity and soil properties. This study has important effects of ecological restoration and management in abandoned coal mine area.

The emerging middle ground: A case study of vernacular Hakka settlements in the peri-urban areas of southern China through an architectural heritage analysis

Rapid urban expansion is transforming rural areas globally, prompting scholars to challenge the traditional urban-rural dichotomy and focus on transitional zones such as the rural-urban fringe and peri-urban areas. This article documents the evolution of architectural morphology in traditional Hakka settlements in peri-urban areas of southern China and coins the hybrid architectural landscape combined with urban and rural characteristics in these ambiguous territories as the “Middle Ground.” Fieldwork was conducted in four Hakka villages in Heyuan, northeast Guangdong, China, between 2021 and 2023. An explorative case study was employed to analyze the architectural morphology of the Middle Ground by mapping village fabric, dwellings, and street markets through aerial photography. A participatory perspective was also incorporated, involving observation, interviews, and documentation of the daily life of local villagers. This research examines how authority and mobility have shaped the Middle Ground, potentially leading to a state of “placelessness,” and explores the role of rural heritage in this context. This research contributes to the broader discourse on peri-urban areas by offering an architectural heritage atlas as an addition to existing research.

Simple synthesis and excellent coagulation performance of a novel red soil-based coagulant

Eutrophication of lakes is a severe threat to local water environment ecosystems and human health and safety. An efficient coagulation process for reducing exogenous nutrient inputs and endogenous algal control is critical. Here, a red soil-based coagulant (RSC) of poly-aluminum iron silicate was prepared by acid leaching and neutralization method using the red soils of southern China as raw material. The removal effect of RSC on various pollutants was tested through coagulation experiments, and the removal rate of humic acid (HA) and turbidity in HA-Kaolin wastewater reached 95.32 % and 99.89 %, which exceeded that of poly-aluminum chloride (PAC). For high concentrations of phosphate (PO43−), the coagulation perform of RSC was approximately 2.5 and 1.8 times higher than that of PAC and poly-ferric chloride (PFC), respectively. The removal effect on Microcystis aeruginosa was 99.2 %, and the coagulation performance was consistent with that of PAC and slightly higher than that of PFC. In addition, excellent coagulation performance for HA (all above 40 %), turbidity (all above 99 %), total phosphorus (all above 87 %), and algae (99 %) in three types of water samples containing municipal effluents, rainy overflow wastewater, and algae-laden water. the TP and COD concentrations of wastewater samples after coagulation treatment were lower than the Class II level (TP ≤ 0.1 mg/L) and III level (COD ≤ 20 mg/L) in Chinese surface water quality standards (GB3838-2002). The study findings show that this simple method of synthesizing a low-cost and highly efficient coagulant using red soil is useful for the pollution control and algal bloom treatments of eutrophic water bodies in red soil areas of southern China or other of world.

Rainfall depth dominates overland flow and sediment yields of the coarse-textured soil: A case study in Southern China

Soil degradation, particularly due to water erosion, is a significant issue in many regions, including the mountainous areas of Southern China. This study investigated the response of overland flow and sediment yield to different rainfall patterns on a coarse-textured soil slope in Southern China. Three distinct rainfall regimes were identified through K-means clustering analysis, based on event rainfall depth, duration, and maximum 30-min intensity (I30). The results showed that rainfall regime II, characterized by moderate rainfall depth, duration, and I30, generated the highest accumulated surface runoff (97.3 mm) and soil erosion (1584.9 t km−2). Further analysis revealed that overland flow and sediment yield were positively correlated with various rainfall characteristics, including rainfall depth, mean intensity, duration, I30, rainfall energy, and rainfall erosivity. However, rainfall depth was identified as the dominant factor, exhibiting the stronger correlations with both the runoff depth (R2 = 0.77, RMSE = 0.396) and the erosion (R2 = 0.58, RMSE = 0.658) than did the mean rainfall intensity, I30, and duration. Note that RMSE values were expressed in logarithmic units in this study. Piecewise regression models were developed to predict overland flow and sediment yield based on rainfall depth, and these models were validated through in-situ rainfall simulation experiments. The results showed that these models produced acceptable soil and water loss predictions, with a mean bias of −0.093 mm and RMSE of 0.197 mm for the runoff depth, and a mean bias of −0.156 t km−2 and RMSE of 0.456 t km−2 for the sediment yield. Thus, rainfall depth is the dominant driver of soil and water loss in the coarse-textured soils of Southern China, and the developed regression models can be used to estimate overland flow and sediment yield in similar environments.

A dynamic fire risk assessment method for compact historic villages based on the improved FRAME

There are a large number of high-value heritage sites in the historic villages preserved in the mountainous areas of southern China. These sites are exposed to major fire risks due to their compact layout and wooden building materials. By improving the fire risk assessment method for engineering (FRAME), we proposed a dynamic fire risk assessment method for compact historic villages. On one hand, a balance between universality and pertinence was established regarding the assessment indexes and weighting system by integrating general factors with unique regional factors. On the other hand, a connecting link between prescriptive fire codes and performance-based design adjustments was established through the cyclic operation path of assessment-intervention-reassessment. Xiaozhai village, which has experienced serious fire incidents, was selected as an example. Its original fire risk, established fire interventions, actual fire results, and optimized fire protection plan were compared and analyzed to validate the effectiveness and reliability of the assessment method. This study reveals the correlation between various factors of the village and building fire risk. Among these factors, building proximity, traditional customs, and fire protection layout, which are not included in the original FRAME, have a significant impact on fire risk. The results of this study can serve as a reference for fire prevention in historic villages with similar characteristics worldwide. Additionally, the proposed methodology can provide insights into the development of fire risk assessment methods for various types of historical settlements, thus promoting the sustainable development of built heritage in these settlements.

Global warming impacts of carbon dioxide, methane, and albedo in an island forest nature reserve

Abstract Forest ecosystems influence climate by sequestering carbon from the atmosphere and by altering the surface energy balance. However, the combined global warming impacts (GWIs), contribution from carbon dioxide (CO2) fluxes, methane (CH4) fluxes, and albedo changes (Δα) remain poorly understood. Here, we reported the combined GWIs of CO2, CH4, and albedo with eddy covariance (EC) measurements during 2020–2022 in a subtropical island forest located in the Nanji Islands National Marine Protected Area in Southern China. We suggested that the island forest acted as a significant carbon sink, with annual CO2 and CH4 fluxes of −548.6 ± 11.1 and −5.67 ± 1.1 g C m−2 yr−1, respectively, while the daily albedo varied within the range of 0.03–0.15. By converting the radiative forcing induced by CH4 and albedo change in the forest to CO2 equivalents, we analyzed the three contributors to the combined GWI. The annual averages GWI of CO2 uptake, CH4 uptake, and Δα were −2 011.6 ± 40.6, −211.3 ± 1.1, and 0.03 ± 4.5 g CO2-eq m−2 yr−1, respectively, with a mean combined GWI of −2 223 ± 40.8 g CO2-eq m−2 yr−1. During 2020–2022, the contributions of CO2 uptake, CH4 uptake, and Δα to the combined GWI were 89.7% to 91.4%, 9.4% to 9.6% and −1.0%–0.9%, respectively. Nanji Island forest had a strong positive effect on climate change mitigation, with CO2 and CH4 uptake greatly enhancing its cooling benefits. Using Pearson correlation and path analysis, we found photosynthetically active radiation, precipitation, soil water content were the primary factors controlling the GWI dynamics, mainly driving the changes in CO2 fluxes. This study provided novel insights into the establishment of the overall evaluation framework for ecosystem-scale GWIs of CO2 and CH4 fluxes, and albedo based on long-term EC measurements in an island forest.

Changes in soil quality during different ecological restoration years in the abandoned coal mine area of southern China

AbstractUnderstanding the effects of abandoned coal mine ecological restoration on soil quality and function is important to protect the regional ecological environment. This study aims to evaluate the ecological restoration effects of soil quality in abandoned coal mine area. Taking Fengcheng County, a typical coal‐rich area in southern China, as a case, this study took 120 soil samples to investigate the influence of restoration years on soil quality by using an integrated soil quality index (SQI). Results indicated that restoration years had significant effects on the saturated hydraulic conductivity (Ks) by affecting the soil bulk density, clay content, and soil water content. Furthermore, clay, soil organic matter, Ks, and pH were selected to assess the effect of ecological restoration years on soil quality. It was found that the ecological restoration 8 years (ER8) site had higher SQI value, indicating ecological restoration years showed a positive correlation with SQI in abandoned coal mine area. Since there was a 4‐year gap between ecological restoration 4 years site and ER8 site, the ecological restoration may be effective between 5 and 8 years. The results of this study are of great significance for improving the effects of ecological restoration and management in abandoned coal mine area.

A Novel Strategy Coupling Optimised Sampling with Heterogeneous Ensemble Machine-Learning to Predict Landslide Susceptibility

The accuracy of data-driven landslide susceptibility prediction depends heavily on the quality of non-landslide samples and the selection of machine-learning algorithms. Current methods rely on artificial prior knowledge to obtain negative samples from landslide-free regions or outside the landslide buffer zones randomly and quickly but often ignore the reliability of non-landslide samples, which will pose a serious risk of including potential landslides and lead to erroneous outcomes in training data. Furthermore, diverse machine-learning models exhibit distinct classification capabilities, and applying a single model can readily result in over-fitting of the dataset and introduce potential uncertainties in predictions. To address these problems, taking Chenxi County, a hilly and mountainous area in southern China, as an example, this research proposes a strategy-coupling optimised sampling with heterogeneous ensemble machine learning to enhance the accuracy of landslide susceptibility prediction. Initially, 21 landslide impact factors were derived from five aspects: geology, hydrology, topography, meteorology, human activities, and geographical environment. Then, these factors were screened through a correlation analysis and collinearity diagnosis. Afterwards, an optimised sampling (OS) method was utilised to select negative samples by fusing the reliability of non-landslide samples and certainty factor values on the basis of the environmental similarity and statistical model. Subsequently, the adopted non-landslide samples and historical landslides were combined to create machine-learning datasets. Finally, baseline models (support vector machine, random forest, and back propagation neural network) and the stacking ensemble model were employed to predict susceptibility. The findings indicated that the OS method, considering the reliability of non-landslide samples, achieved higher-quality negative samples than currently widely used sampling methods. The stacking ensemble machine-learning model outperformed those three baseline models. Notably, the accuracy of the hybrid OS–Stacking model is most promising, up to 97.1%. The integrated strategy significantly improves the prediction of landslide susceptibility and makes it reliable and effective for assessing regional geohazard risk.

Determining the planting year of navel orange trees in mountainous and hilly areas of southern China: a remote sensing based method

Determining the planting year of navel orange trees in mountainous and hilly areas of southern China: a remote sensing based method

A method for assessing the resilience of urban interdependent systems integrating physical damage and social loss

As systems in urban areas become increasingly interdependent, the effects of disasters extend beyond facilities damage, precipitating casualties, and public service disruptions. Establishing a holistic resilience assessment method is crucial for urban sustainability planning. Existing resilience assessment methods often focus on the physical damage; however, few studies examine the social loss. This study proposes a resilience assessment method that integrates physical damage and social loss. A multilayer network model of physical-social systems is first developed based on their interdependency. Then, the evolution of disaster damage within and between systems process, and the multi-task parallel restoration process are quantified. Resilience is assessed by measuring dynamic changes in service supply and demand throughout these processes. The method considers social loss as a combination of population harm and service interruption caused by physical damage. The proposed method was applied to an urban area in Southern China. The results reveal the impact of seismic events on infrastructure, buildings, and populations. Furthermore, they demonstrate the coupling impacts of supply and transportation on emergency and healthcare systems’ resilience. This comprehensive method could facilitate the development of efficient strategies to improve urban resilience to disasters.

Characterizing the Supercooled Cloud over the TP Eastern Slope in 2016 via Himawari-8 Products

Supercooled liquid water (SLW) refers to droplets in clouds that remain unfrozen at temperatures below 0 °C. SLW is an important intermediate hydrometeor in the processes of snowfall and rainfall that can modulate the radiation budget. This study investigates the distribution of supercooled cloud water over mainland China using the East Asia–Pacific cloud macro- and microphysical properties dataset (2016), derived from Himawari-8 observations. The results show that the highest frequency of SLW in liquid-phase stratus clouds occur at the eastern slope of the Tibetan Plateau, the western side of the Sichuan Basin. Additional SLW is mostly found in liquid-phase clouds over the Sichuan Basin and its adjacent areas in southern China. In the region with the highest frequency of SLW, the mechanical forcing of the Tibetan Plateau causes the convergence of low-level airflow within the basin, which also carries moisture that is forced to ascend stably, creating a favorable condition for the formation of supercooled clouds. As the airflow continues to ascend, it encounters the mid-to-upper-level westerlies and temperature inversion. At the mid-to-upper level, the westerlies exhibit stronger wind speeds, directing flow towards the basin. Concurrently, the temperature inversion stabilizes the atmospheric stratification, limiting the further ascent of airflow. This inversion can also restrain convection and upward motion within the clouds, allowing for SLW to exist and persist for an extended period.

A benchmarking analysis of sunlight and daylight availability in a highly dense urban area in southern China

The availability of daylight and sunlight in dense cities has increasingly received attentions. This article presented a benchmarking analysis of daylight & sunlight availability in six urban residential layouts at Guangzhou in southern China. As representatives of old or new towns, these layouts were achieved using local regulations. The benchmarking system was built based on an urban building under various levels of obstruction (horizontally infinite length). Daysim (Radiance) and T-sun were applied to calculate daylight illuminance and sunlight hours at building facades, respectively. Some findings were achieved as follows: 1) For sunlight availability, significant effects of urban layout and orientation can be found in both towns. Most layouts achieved similar sunlight hours as an urban building with high and heavy obstructions, while several southeast-oriented and southwest-oriented layouts had the values like a building with the medium obstruction. No clear differences of sunlight hours can be found between southeast and southwest orientations. 2) For daylight availability, most buildings in both towns had similar frequencies of proper vertical illuminance as an urban building with the medium obstruction. However, the frequencies of excessive vertical illuminance significantly varied in layout, façade position, and orientation and corresponded with the values of an urban building with different obstructions. Effects of layout were found to be clear at low and middle façade positions, while significant effects of orientation were only found at higher façade positions. 3) Generally, a daylighting analysis using the dynamic climate-based model could achieve more practical results than the approach of sunlight hours.

Factors Controlling Differences in Morphology and Fractal Characteristics of Organic Pores of Longmaxi Shale in Southern Sichuan Basin, China

Shale gas is a prospective cleaner energy resource and the exploration and development of shale gas has made breakthroughs in many countries. Structure deformation is one of the main controlling factors of shale gas accumulation and enrichment in complex tectonic areas in southern China. In order to estimate the shale gas capacity of structurally deformed shale reservoirs, it is necessary to understand the systematic evolution of organic pores in the process of structural deformation. In particular, as the main storage space of high-over-mature marine shale reservoirs, the organic matter pore system directly affects the occurrence and migration of shale gas; however, there is a lack of systematic research on the fractal characteristics and deformation mechanism of organic pores under the background of different tectonic stresses. Therefore, to clarify the above issues, modular automated processing system (MAPS) scanning, low-pressure gas adsorption, quantitative evaluation of minerals by scanning (QEMSCAN), and focused ion beam scanning electron microscopy (FIB-SEM) were performed and interpreted with fractal and morphology analyses to investigate the deformation mechanisms and structure of organic pores from different tectonic units in Silurian Longmaxi shale. Results showed that in stress concentration areas such as around veins or high-angle fractures, the organic pore length-width ratio and the fractal dimension are higher, indicating that the pore is more obviously modified by stress. Under different tectonic backgrounds, the shale reservoir in Weiyuan suffered severe denudation and stronger tectonic compression during burial, which means that the organic pores are dominated by long strip pores and slit-shaped pores with high fractal dimension, while the pressure coefficient in Luzhou is high and the structural compression is weak, resulting in suborbicular pores and ink bottle pores with low fractal dimension. The porosity and permeability of different forms of organic pores are also obviously different; the connectivity of honeycomb pores with the smallest fractal dimension is the worst, that of suborbicular organic pores is medium, and that of long strip organic pores with the highest fractal dimension is the best. This study provides more mechanism discussion and case analysis for the microscopic heterogeneity of organic pores in shale reservoirs and also provides a new analysis perspective for the mechanism of shale gas productivity differences in different stress–strain environments.

Specific ion effects on the soil shear strength and clay surface properties of collapsing wall in Benggang.

Benggangs are a special type of soil erosion in the hilly granite regions of the tropical and subtropical areas of Southern China. They cause severe soil and water loss, which can severely deteriorate soil quality and threat to the local ecological environment. Soils (red soil, sandy soil and detritus soil) were collected from collapsing wall of a typical Benggang in Changting County of Fujian Province, and their physicochemical and mineralogical properties were analyzed. Five different monovalent cations were used to saturate the soil samples to examine the specific ion effects on the shear strength and clay surface properties. Red soil had a higher clay content, plastic limit, liquid limit and shear strength than sandy soil and detritus soil. The studied soils mainly consisted of kaolinite, hydroxy-interlayer vermiculite, illite and gibbsite clay minerals. The soils saturated with K+, NH4 +and Cs+ had greater cohesion than the Li+- and Na+-saturated soils, e.g., the cohesion of the red soil saturated with Li+, K+, NH4 + and Cs+ cations were 1.05, 1.23, 1.45 and 1.20 times larger than that of the Na+-saturated soil, respectively. While the internal friction angle was slightly different, which indicated that different monovalent cations affected the shear strength differently. K+-, NH4 +- and Cs+-saturated clay particles had higher zeta potentials and thinner shear plane thicknesses than Li+- and Na+-saturated clay particles and showed strong specific ion effects on the clay surface properties. The changes in clay surface properties strongly affected the soil mechanical properties. Soils saturated with K+, NH4 + and Cs+ could increase the shear strength, and then increase the stability of the collapsing wall, thus might decrease the erosion intensity of Benggang. The results provide a scientific basis for the interpretation of and practical treatment of Benggang.

The adaptation of dryland crops to the climate in southern China

It is unclear how dryland crops adapted to the humid climate of southern China, nevertheless they were an important component of prehistoric agricultural systems in the region. In this study, archaeobotanical results assembled from 110 archaeological sites in southern China, Digital Elevation Model (DEM)-based slope results of these archaeological sites, regional meteorological data and paleoclimate records were used to analyse the main factors affecting the distribution of prehistoric dryland agriculture, to help understand the adaptation of this agriculture to southern China and assess the role of climate change in the expansion of dryland crops in the region. The results highlighted the importance of effective water input and temperature. Farmers in prehistoric times adopted diverse strategies to plant dryland crops in southern China. The main proportion of the dryland crops centred on the use of foxtail millet (over 75% of the total dryland crops) and it was adjusted to adapt to the variations in effective water inputs resulting from precipitation and topography in the low-elevation area. Approximately 3° might be the slope threshold for agricultural transformation in the low-elevation humid areas of southern China. The millets-dominated (61.7%) or rice-dominated (85.3%) agricultural systems in dry-hot valleys, and wheat-dominated (51.8%) agriculture in the west Yunnan-Guizhou Plateau were developed to adapt to the arid climate and the low summer temperature, respectively. The weakening of the Asian monsoon since 5000 BC had objectively favoured the expansion of dryland agriculture in the low-slope areas of southern China, but the role of climate change should not be overestimated in the expansion of dryland crops.

Vegetation restoration limited microbial carbon sequestration in areas affected by soil erosion

The impact of vegetation restoration on soil structure, nutrients, and microorganisms in eroded areas has been extensively studied, but the effect of vegetation restoration on carbon-sequestering bacterial communities and their associated carbon fixation capacity remains largely unknown. In this study, we focused on the 0–20 cm soil layer in eroded and vegetation restoration sites in areas of southern China that have been severely affected by soil erosion and utilized 13C stable isotope labeling and high-throughput sequencing technologies to investigate the influence of vegetation restoration on carbon-sequestering bacterial communities and their carbon sequestration potential. Compared with eroded areas, vegetation restoration areas presented greater soil nutrient contents and greater diversity of bacteria with carbon sequestration functions. Vegetation restoration also altered the composition of carbon-sequestering bacterial communities by increasing the soil alkali-hydrolyzable nitrogen content, with the dominant carbon-sequestering bacteria shifting from Nocardia to Bradyrhizobium. However, the microbial carbon sequestration rate in soil erosion areas significantly increased by 2.15 times compared with that in vegetation restoration areas. Among the factors considered, pH (68.90 %, P = 0.000) was identified as the primary explanatory factor regulating changes in the microbial carbon sequestration rate. Our results are important for revealing the role of vegetation restoration in the global carbon cycle and elucidating the role of microorganisms in the soil carbon cycle.

Characteristics of Vegetation Photosynthesis under Flash Droughts in the Major Agricultural Areas of Southern China

Characteristics of Vegetation Photosynthesis under Flash Droughts in the Major Agricultural Areas of Southern China

Effects of parent material on soil hydraulic properties in subtropical hilly area of Southern China

The parent materials play an important role in soil hydrologic properties. However, in subtropical hilly areas with complex geological conditions, it appears that there is a lack of full understanding about the effect of parent material on soil water-holding and erosion resistance, which can be helpful for agricultural production and conservation of soil and water. In this study, five red soils developed from shale (Ds), quartz sandstone (Dqs), argillaceous nodular limestone (Danl), argillaceous limestone (Dal), and limestone conglomerate (Dlc) in subtropical China were selected. Soil properties, soil water-retention curves (SWRCs), water-stable aggregate fractions, and soil erodibility factor (K) were tested and calculated. The results showed that there are significant differences in soil texture among soils developed from different parent materials, soils with higher clay content have stronger water-holding capacity, and the average water-holding capacity of the five soils followed the order Dal > Danl > Ds > Dlc > Dqs. Furthermore, the erosion resistance of soil is closely related to the clay content and the stability of soil aggregates, and the sequence of average K-value among the five soil types is as follows: Danl > Dal > Dlc > Ds > Dqs. Partial least squares regression revealed that the stability of aggregates has a more significant influence on soil erodibility than the clay content. Therefore, soils with higher mean weight diameter (MWD) and geometric mean diameter (GMD) are more resistance to erosion. This paper evaluated the distinctions in basic properties and hydraulic properties between different parent materials under similar climatic conditions, elevations and vegetation in subtropical hilly area of Southern China, which can serve as a scientific foundation for soil and water conservation in the environments characterized by complex geological conditions.