Karst Region Of Southwest China Research Articles

Study on the differences and influencing factors of spatial distribution of population aging at township scale: a case study of township research units in Anshun City, China.

An aging population is one of the main features of China's current population structure, and it is a key area that needs attention to achieve high-quality population development. Because of its unique geographical environment, economic conditions, and sociocultural background, the study of population aging in the karst region of southwest China is particularly important. However, there is a lack of research exploring the regional differentiation of population aging and its influencing factors in the karst regions of southwest China. In light of this, we chose Anshun City, located in Guizhou Province's southwest area, as the case study area. We used the Lorenz curve and spatial autocorrelation to study the differences in the spatial distribution pattern of population aging and introduced multi-scale geographical weighted regression to explore its influencing factors. The results show that Anshun City's older people population proportion (OPP) is generally high with more than 7% of the older people there, making it part of an aging society. The OPP appeared high in the east and low in the west in spatial distribution; the older people population density (OPD) revealed a gradually increasing trend from south to north. At the township scale, both the OPP and the OPD showed significant spatial positive correlation, and the spatial agglomeration characteristics were obvious. OPD and OPP have a positive spatial correlation at the global level, and townships with similar OPP or OPD were spatially adjacent. The spatial distribution characteristics of population aging are the consequence of complex contributions such as natural, social, economic, and karst factors. Further, the spatial distribution pattern of aging is determined by a variety of influencing factors, which have different directions and intensities. Therefore, it is necessary to formulate and implement corresponding policies and strategies to deal with the aging problem in the future.

Afforestation enhances glomalin-related soil protein content but decreases its contribution to soil organic carbon in a subtropical karst area

Afforestation on degraded croplands has been proposed as an effective measure to promote ecosystem functions including soil organic carbon (SOC) sequestration. Glomalin-related soil protein (GRSP) plays a crucial role in promoting the accumulation and stability of SOC. Nevertheless, mechanisms underlying the effects of afforestation on GRSP accumulation have not been well elucidated. In the present study, 14 pairs of maize fields and plantation forests were selected using a paired-site approach in a karst region of southwest China. By measuring soil GRSP and a variety of soil biotic and abiotic variables, the pattern of and controls on GRSP accumulation in response to afforestation were explored. The average content of total GRSP (T-GRSP) and its contribution to SOC in the maize field were 5.22 ± 0.29 mg g−1 and 42.33 ± 2.25%, and those in the plantation forest were 6.59 ± 0.32 mg g−1 and 25.77 ± 1.17%, respectively. T-GRSP content was increased by 26.4% on average, but its contribution to SOC was decreased by 39.1% following afforestation. T-GRSP content decreased as soil depth increased regardless of afforestation or not. Afforestation increased T-GRSP indirectly via its positive effects on arbuscular mycorrhizal fungi biomass, which was stimulated by afforestation through elevating fine root biomass or increasing the availability of labile C and N. The suppressed contribution of T-GRSP to SOC following afforestation was due to the relatively higher increase in other SOC components than T-GRSP and the significant increase of soil C:N ratio. Our study reveals the mechanisms underlying the effects of afforestation on T-GRSP accumulation, and is conducive to improving the mechanistic understanding of microbial control on SOC sequestration following afforestation.

Afforestation alters soil microbial community composition and reduces microbial network complexity in a karst region of Southwest China

AbstractSoil microbial community plays important roles in altering ecological processes and biogeochemical cycles in ecosystems. However, little is known about how afforestation influences the diversity, composition, and ecological network of soil microbial community in karst regions. In this study, soil samples were collected from one farmland (FL) and three afforestation lands including one bamboo forest (BA), one landscape tree planting forest (LAT), and one orange orchard (ORO) in a karst region of Southwest China. The bacterial and fungal communities were characterized using the high‐throughput sequencing approach, and soil properties including soil organic carbon, pH, soil water content, and soil total and available nutrient contents were measured under different land use treatments. Results showed that conversion from FL to BA and LAT significantly reduced the Shannon diversity of bacterial community. At the phylum level (top 10), genus level (top 30), and operational taxonomic units (OTUs) level, afforestation from FL resulted in significant changes in nine phyla, 24 genera, and 31.32% OTUs of bacterial community, and in three phyla, 13 genera, and 11.62% OTUs of fungal community. The number of nodes, number of negative edges, connectivity, average degree, and relative modularity of the microbial network under afforestation lands decreased by 9.33%–18.66%, 47.98%–72.75%, 0.45%–5.93%, 14.73%–22.29%, and 6.46%–23.50%, respectively, compared with FL. The soil organic carbon, total potassium and total phosphorus were identified as the key soil properties affecting the microbial community. Compared with LAT and ORO, the changes in bacterial and fungal communities under BA were more obvious because of the higher contents in soil organic carbon (13.48%) and total potassium (27.18%). In conclusion, afforestation significantly changed compositions and ecological network complexity of soil microbial community in karst regions, and conversion from FL to BA had stronger influences on the changes of soil microbial community than other afforestation lands in Southwest China. These findings provide the context necessary to evaluate the responses of soil microbial community to land use changes in karst regions.

Soil thickness influences the control effect of micro-topography on subsurface runoff generation in the karst hillslope critical zone

Topography plays a crucial role in predicting rainfall-runoff processes under climate change, as it affects the spatial distribution of water flow pathways. However, understanding the potential impact of high micro-topography heterogeneity on runoff generation remains challenging. We conducted high-resolution monitoring of soil moisture, instantaneous water table, and subsurface runoff in two 3D plots with different soil thicknesses (66 cm vs. 35 cm) in the karst region of southwest China. The topographic features were characterized by the soil thickness, relative elevation, and topographic wetness index obtained from a 1 × 1 m grid. The topography of the shallow-soil plot (SSP) exhibited a higher level of complexity, with a greater variability (approximately 80.0 %) in soil thickness compared to that of the deep-soil plot (DSP; approximately 61.5 %). Additionally, the SSP was prone to forming a micro-topography characterized by a combination of exposed bedrock and soil cover. In DSP, the variation in soil moisture was strongly controlled by surface topography, with elevation contributing to 52 % and 81 % of the explanation for the soil moisture at 30 cm and soil–bedrock interface, respectively. In SSP, the contribution of topography to the variation in soil moisture did not exceed 31 %. The controlling effect of topography on runoff is highlighted in SSP, with the contribution rates of surface and bedrock relative elevation reaching 79% and 97%, respectively.The weaker water storage capacity of the SSP resulted in a higher volume of subsurface runoff (161 t vs. 116 t) and frequency of runoff events (2248 vs. 1994) compared to the DSP. Accordingly, this study emphasizes that the soil–bedrock spatial heterogeneity will control the relationship between soil moisture, subsurface runoff, and terrain, which will contribute to providing a basis for flood prediction and model simulation in regions with complex topography.

Assessing rainfall erosivity changes over China through a Bayesian averaged ensemble of high-resolution climate models

Spatiotemporal variation in rainfall erosivity resulting from changes in rainfall characteristics due to climate change has implications for soil erosion in developing countries. To promote soil and water conservation planning, it is essential to understand past and future changes in rainfall erosivity and their implications on a national scale. In this study, we present an approach that uses a Bayesian model averaging (BMA) method to merge multiple regional climate models (RCMs), thereby improving the reliability of climate-induced rainfall erosivity projections. Our multi-climate model and multi-emission scenario approach utilize five RCMs and two Representative Concentration Pathways (RCP4.5 and RCP8.5) scenarios for the baseline period (1986–2005) and future periods (2071–2090) to characterize the spatiotemporal projection of rainfall erosivity and assess variations in China. Our results indicate that the two models outperform other models in reproducing the spatial distribution and annual cycle of rainfall erosivity in China. Moreover, we found an increasing trend in the annual rainfall erosivity from the baseline climate up to the RCMs for all models, with an average change in erosivity of approximately 10.9% and 14.6% under RCP4.5 and RCP8.5, respectively. Our BMA results showed an increase in the absolute value of rainfall erosivity by 463.3 and 677.0 MJ·mm·hm−2·h−1, respectively, in the South China red soil region and the Southwest China karst region under the RCP8.5 scenario. This increase indicates that climate warming will significantly enhance the potential erosion capacity of rainfall in these regions. Additionally, our study revealed that the Southwest China karst region and the Northwest China Loess Plateau region are more sensitive to radiation forcing. To mitigate the risk of soil erosion caused by climate change, it is necessary to consider changes in rainfall erosivity, local soil conditions, vegetation coverage, and other factors in different regions and take appropriate soil and water conservation measures.

Characteristics and influencing factors of farmland abandonment in the karst rocky desertification area of Southwest China

Owing to rocky desertification, farmland abandonment in karst areas is different from that in normal landforms. Aiming at the phenomenon of large-scale farmland abandonment in the karst region of Southwest China, this study investigated the characteristics of farmland abandonment in different rocky desertification control areas of typical counties. We interpreted land use changes in the study area using high-resolution images (5 m) in 2010 and 2020 through human–computer interaction. After removing patches of converted farmland to forests, we extracted the spatial distribution of abandoned farmland. The study area was found to have a high abandonment rate (24.83 %), with dryland showing 2–3 times higher abandonment rate than paddy fields. The abandoned area in rocky desertification dryland accounts for 50.57 % (499.04 km2) of the abandoned area of karst dryland. It is worth noting that the abandonment rate of non-rocky desertification dryland in the karst dryland is the lowest (22.45 %), while the abandonment rate of dryland shows no significant difference among other rocky desertification grades, with an average of 28.00 %. In addition, with the change of rocky desertification level, the index of abandonment degree showed a trend of initial increase followed by a decrease. Slope, lithology and soil type have a joint effect on karst dryland abandonment. Slope is the core factor affecting karst dryland abandonment, and the interaction between slope and soil type is the dominant factor affecting its change. The results of this study show that farmland abandonment is serious in karst rocky desertification areas, primarily occurring in rocky desertification dryland. The government should take targeted management measures based on the current status of abandoned drylands at different levels of rocky desertification, especially in sloping farmland areas.

Effect of Vegetation Restoration on Soil Humus and Aggregate Stability within the Karst Region of Southwest China

This study aims to investigate the impact of vegetation restoration on soil humus and aggregate stability within the karst region of Southwest China. This study focused on soils at five vegetation succession stages (abandoned land, grassland, shrub rangeland, shrubland, and secondary forest) in the typical karst region, and the aggregate stability was determined using wet sieving and the Le Bissonnais method. Simultaneously, the Pallo method and separation extraction were used to determine the humus composition, aiming to analyze the distribution of humus content in the soil aggregates and its effect on aggregate stability. The results revealed the following: (1) The mean weight diameter of soil aggregates significantly increased with vegetation restoration stages. Soil water-stable aggregates at each vegetation stage mainly included particles over 2 mm in size. (2) The humic acid and fulvic acid contents consistently increased with vegetation restoration, and the precipitation quotient value of the humification degree showed an increasing trend. At each vegetation restoration stage, the percentage of each humus component was, from highest to lowest, as follows: insoluble HM, fulvic acid, humic acid, clay-bound HM, and iron-bound HM. (3) Through stepwise regression analysis, humic acid content in >2 mm aggregates, fulvic acid and clay-bound HM contents in 1–2 mm aggregates, and insoluble HM content in <0.25 mm aggregates were the dominant factors affecting soil aggregate stability in the karst region. These results aim to provide novel insights for a more in-depth comprehension of the restoration and rehabilitation of vegetation within the karst region of Southwest China, thereby laying a robust foundation for scientific theories and further investigations.

Characterization of controlling factors for soil organic carbon stocks in one Karst region of Southwest China.

Soil organic carbon (SOC) contributes the most significant portion of carbon storage in the terrestrial ecosystem. The potential for variability in carbon losses from soil can lead to severe consequences such as climate change. While extensive studies have been conducted to characterize how land cover type, soil texture, and topography impact the distribution of SOC stocks across different ecosystems, little is known about in Karst Region. Here, we characterized SOC stocks with intensive sampling at the local scale (495 representative samples) via Random Forest Regression (RF) and Principal Component Analysis (PCA). Our findings revealed significant differences in SOC stock among land cover types, with croplands exhibiting the lowest SOC stocks, indicating that management practices could play a crucial role in SOC stocks. Conversely, there was little correlation between SOC stock and clay percentage, suggesting that soil texture was not a primary factor influencing SOC at a local scale. Further, Annual Precipitation was identified as the key driving factor for the dynamics of SOC stocks with the help of RF and PCA. A substantial SOC deficit was observed in most soils in this study, as evaluated by a SOC/clay ratio, indicating a significant potential in SOC sequestration with practical measures in the karst region. As such, future research focused on simulating SOC dynamics in the context of climate change should consider the controlling factors at a local scale and summarize them carefully during the up-scaling process.

Dynamic Changes of Soil Microbial Communities During the Afforestation of Pinus Armandii in a Karst Region of Southwest China

Clarifying the response of soil microbial communities to vegetation restoration is essential to comprehend biogeochemical processes and ensure the long-term viability of forest development. To assess the variations in soil microbial communities throughout the growth of Pinus armandii plantations in the karst region, we utilized the “space instead of time” approach and selected four P. armandii stands with ages ranging from 10 to 47 years, along with a grassland control. The microbial community structure was determined by conducting Illumina sequencing of the 16 S rRNA gene and the ITS gene, respectively. The results demonstrated that afforestation with P. armandii significantly influenced soil microbial communities, as indicated by notable differences in bacterial and fungal composition and diversity between the plantations and the control. However, soil microbe diversity did not display significant variation across stand ages. Moreover, the bacterial community exhibited higher responsiveness to age gradients compared to the fungal community. Soil physicochemical factors play a critical role in elucidating microbial diversity and community composition variations during restoration processes. TN, AN, TP, AP, SOC, AK, and pH were the most significant influencing factors for the composition of bacterial community, while TC, SOC, pH, and TCa were the most significant influencing factors for the composition of fungal community. Our findings indicate substantial changes in soil bacterial and fungal communities across successive stages of development. Additionally, the changes in dominant bacteria and fungi characteristics across the age gradient were primarily attributed to variations in the prevailing soil conditions and chemical factors.

Effects of rainfall, sediment source–sink landscape, and hydrological connectivity on runoff more than sediment in a karst basin

AbstractUnderstanding the mechanisms underlying soil and water loss in karst basins is beneficial for water resources management and soil and water loss conservation. However, the effects of rainfall, sediment source–sink landscape, and hydrological connectivity on runoff sediment characteristics in karst basins are unclear. This study used sediment source–sink landscape and hydrological connectivity theories and a generalized additive model to analyze the changes and combined effects of sediment source–sink landscape patterns, hydrological connectivity, and rainfall on runoff sediment from 2000 to 2020 in the Yeji River basin in the karst region of southwest China. The results indicated that the average sediment transport modulus and runoff modulus in the Yeji River basin during 2000–2020 were 144 t·km−2·a−1 and 15 L·s−1·km−2, respectively. The karst surface and subsurface double‐layer hydrological structure resulted in a lower sediment transport modulus than in non‐karst areas. The sediment‐source landscape area decreased, sediment‐sink landscape area increased, and sediment source–sink landscape load ratio index slightly increased. Hydrological connectivity exhibited a decreasing trend over time, but the overall change was small. Changes in source–sink landscape patterns significantly affected hydrological connectivity. As the main affecting factor, rainfall and its combined effects with sediment source–sink landscape patterns and hydrological connectivity explained 85% and 95% of the variances in runoff, and 40% and 63% of the variances in sediment, respectively. These results suggest that a rational layout of the sediment source–sink landscape can effectively improve hydrological connectivity and regulate the soil and water loss process. Our findings have important implications for karst basin ecological restoration and protection.

[Main sources of soil phosphorus and their seasonal changes across different vegetation restoration stages in karst region of southwest China].

Investigating the main sources of soil phosphorus and their seasonal variations across different vegetation restoration stages in karst region of southwest China can deepen our understanding of soil phosphorus cycling during vegetation restoration, and provide scientific reference for the controlling of rocky desertification. Taking the typical karst ecosystems at different vegetation restoration stages in Guilin, Guangxi as the research objects, we conducted a one-year field experiment with three treatments: vegetation restoration for about 10 years (R10), 30 years (R30) and 50 years (R50). We collected rainfall based on precipitation frequency, as well as soil, fresh litter and root samples in each season to measure the concentrations of total phosphorus (TP) in rainfall, the contents of TP and available phosphorus (AP) in soil, and the contents of TP in fresh litter and roots. In combination with litter phosphorus storage and soil microbial biomass phosphorus (MBP), we analyzed the contributions of phosphorus input to soil from different phosphorus sources. The results showed that soil TP content increased initially and then decreased with vegetation restoration, with a seasonal pattern of autumn > summer > spring > winter. Soil AP content was low in all treatments, with higher levels in summer and winter than in spring and autumn. Soil MBP content increased with vegetation restoration, with a seasonal variation pattern of spring >autumn > summer > winter. The annual phosphorus input from rainfall was 0.78 kg·hm-2 with the highest value in spring. The annual phosphorus input from fresh litter in the R10, R30, and R50 treatments was 2.42, 10.64 and 5.03 kg·hm-2. Phosphorus storage in litter was 1.23, 5.32 and 3.45 kg·hm-2. The annual phosphorus input from plant roots was 5.18, 12.65, and 5.96 kg·hm-2, respectively. The highest levels of the above parameters always occurred in the R30 treatment. There was a significant positive correlation between soil TP content and plant root phosphorus input, and a significant negative correlation between soil AP content and rainfall phosphorus input. In summary, the contribution of phosphorus input from different sources to soil phosphorus pool varied across different vegetation restoration stages in the karst region of southwest China. Roots are the main source of soil phosphorus, followed by litters. Phosphorus entering the soil through wet deposition is very limited. Soil microorganisms also contribute to soil phosphorus reserve.

Planting Year- and Climate-Controlled Soil Aggregate Stability and Soil Fertility in the Karst Region of Southwest China

The effects of long-term monocropping systems combined with climate on soil water aggregate stability (WSA) and soil fertility in the karst region of Southwest China (KRSWC) are unclear. Our research was conducted in the KRSWC, wherein tobacco (Nicotiana tabacum) production is characterized by heavy fertilization and continuous monocropping. The tobacco fields in the study area have similar soil types and fertilization and tillage practices and are spread over an area of 11,500 km2. A total of 568 topsoil samples were collected in 2021. Soil fertility was reflected using the soil fertility index (SFI), which was calculated using the minimum data set method with six soil fertility-related factors, namely, soil pH, soil organic matter, cation exchange capacity, available nitrogen, available phosphorus, and available potassium. Results showed that long-term planting generally promoted soil fertility levels and WSA content. WSA and SFI had inconsistent spatial distribution patterns likely due to different climate-driven effects. WSA variability was greatly controlled by precipitation (Spearman correlation coefficient [r] = −0.49, p < 0.01), whereas SFI variability was mostly dominated by temperature (r = −0.36, p < 0.01). The levels of SFI and WSA were optimal under conditions of low temperature and precipitation and poor under conditions of high temperature and precipitation. Moreover, long-term planting could alleviate the negative effects of climate on SFI and WSA in the KRSWC. The results of this study could provide valuable information on fertilization and climate-adapted strategies for tobacco fields in the KRSWC.

An analysis of the spatiotemporal evolution and driving force of cultivated land green utilization in karst region of southwest China

Optimizing the green use efficiency of cultivated land in the karst region of southwest China is crucial for promoting sustainable development of land resources and achieving harmony between humans and nature. Based on the epsilon-based measure model and geographically and temporally weighted regression methods, this paper investigated the spatio-temporal variation and influencing factors of cultivated land green utilization efficiency. The results indicated that: i) Cultivated land green utilization efficiency had slightly increased from 0.842 in 2000 to 0.866 in 2020. ii) The spatial pattern of cultivated land green utilization efficiency showed a significant positive correlation, with a “hotspot-not significant-coldspot” from north to south. iii) Its spatial heterogeneity had increased during the observation period, with high-efficiency areas shifting from northeast to north. iv) The proportion of agricultural economy, general public budget revenue, per unit cultivated land value had a positive impact on the cultivated land green utilization efficiency, while urbanization rate, per capita cultivated land area, land replanting index, average altitude had a negative impact. Moreover, the driving factors exhibited significant spatiotemporal heterogeneity. Therefore, it is necessary to promote technological progress and scientific research, implement funds and policies, leverage the leading role of high-efficiency areas, formulate differentiated development strategies, and thereby improve the green use efficiency of cultivated land.

Monitoring the evolution process of karst desertification and quantifying its drivers in the karst area of Southwest China.

Karst desertification (KD) is a unique desert ecological phenomenon occurring in the karst region of Southwest China (KRSC). Studying the KD evolution process and distinguishing the influences of human activities and climate factors on KD are essential for restoring KD areas. This article is based on MODIS remote sensing data and ERA5-Land data. Additionally, multiple linear regression models, correlation analysis, and residual analysis are utilized to analyze the spatiotemporal evolution characteristics of KD in the southwest region of China from 2000 to 2020. This study aims to differentiate the impacts of human activities and climate change on the desertification process in karst areas. (1) In the southwest region of China, the overall KD shows an intensifying trend at both ends of the study area and an ameliorating distribution pattern in the central region. In particular, Guizhou province, which is located in the center of the study area, demonstrated significant suppression in the KD process from 2000 to 2020. (2) In the southwest karst region, there are significant spatial differences in the correlation between the KD process and precipitation, temperature, and radiation. Temperature is significantly negatively correlated in most parts of Yunnan. (3) According to the residual analysis, approximately 89.62% of the karst areas in the southwest are influenced by climate, while 10.38% are influenced by human activities. Climate change has a relatively small impact on the ability to improve KD compared to the disruptive influence of human activities. Some human activities, such as afforestation, in which grassland and cultivated land are converted to forest, play a substantial role in inhibiting the KD process. Conversely, the rapid expansion of urban areas tends to exacerbate KD in adjacent regions. Therefore, this study of the evolution process of KD in Southwest China can provide a scientific basis for monitoring and controlling KD and provide theoretical support for coping with the challenges posed by KD to China's ecological environment.

Spatial variations in soil erodibility induced by rock outcropping on sloping cropland in the karst region of Southwest China

Sloping croplands in karst areas of Southwest China usually contain a multitude of rock outcrops with diameters larger than 25 cm. Rock outcrops and spatial location have substantial effects on soil properties and thus likely affect soil erodibility. Moreover, rock outcropping is a indicator of rocky desertification and has an important impact on soil erosion and soil formation processes. However, the potential effects of spatial location and rock outcrops on the soil erodibility of sloping cropland in karst areas are still unclear. This study was performed to explore the variations in soil erodibility reflected by saturated hydraulic conductivity (KS), mean weight diameter (MWD), soil structural stability (SSI), soil erodibility factor (K) and soil organic carbon content (SOC) at three spatial locations in sloping cropland with rock outcrops on the karst hillside. The results showed that the soil erodibility indicators KS, MWD, SSI and SOC declined with increasing soil depth for all tested sites. SSI and SOC were predominant factors contributing to the variation in soil erodibility, which were 34.9 % and 35.1 % at the upper spatial location, 31.4 % and 30.9 % at the middle spatial location, and 32.1 % and 32.6 % at the lower spatial location, respectively. There were significant variations in the K factor between the sloping cropland with rock outcrops and the control group. The variations in soil erodibility indicators with rock outcrops and spatial locations were attributed to the changes in soil particle distribution, soil bulk density and SOC. There was a significant linear correlation between the K factor and spatial location, slope gradient, coverage and height of rock outcrops. These results indicated that rock outcrops and their characteristics can reduce soil erosion intensity by redistributing precipitation and runoff, thus further affecting infiltration and soil erodibility. These findings are helpful to comprehend the processes and mechanisms of the spatial variation in soil erosion on sloping cropland with rock outcrops.

Lithology‐mediated soil erodibility characteristics after vegetation restoration in the karst region of Southwest China

AbstractEcological restoration projects have significantly increased global vegetation cover and reduced soil erosion. However, it is very challenging to clarify the complex soil erosion mechanisms of limestone and dolomite in the southwest karst region and to identify the key factors affecting erosion. The study site has a subtropical monsoon climate with precipitation concentrated during the rainy season from May to September. In this study, four plantation restoration measures with a recovery time of approximately 16 years were selected, which included arbor forest, orchard, grassland, and cropland (control). Soil physical–chemical properties and soil erodibility K values were used to evaluate the soil erosion characteristics. The results showed that both limestone and dolomite exhibited lower soil bulk density as well as higher capillary porosity, and soil water‐stable aggregates after revegetation. The limestone and dolomite K values were reduced by 12%–15% and 15%–17%, respectively. However, the K value of limestone was 17.9% higher than that of dolomite, indicating that dolomite exhibited a higher stability. Through redundancy analysis and structural equation modeling, revegetation was found to reduce soil erosion by influencing the soil particle composition. The silt was the key factor influencing soil erosion, accounting for 84.4% and 78.2% of the variation in the limestone and dolomite K values, respectively. These findings suggest that vegetation restoration enhances soil erosion resistance; however, the effectiveness of restoration is controlled by the lithology in the southwest karst region. These findings provide a reference for soil and water management and vegetation restoration.

Carbon Sink Trends in the Karst Regions of Southwest China: Impacts of Ecological Restoration and Climate Change

Southwest China (SWC) holds the distinction of being the world’s largest rock desertification area. Nevertheless, the impacts of climate change and ecological restoration projects on the carbon sinks in the karst area of Southwest China have not been systematically evaluated. In this study, we calculated carbon sinks by utilizing the Carnegie–Ames–Stanford Approach (CASA) model, and the actual measurements, including the net primary productivity (NPP) data and soil respiration (Rs,) were calculated to obtain carbon sink data. Our findings suggest that the carbon sinks in the karst areas are displaying increasing trends or positive reversals, accounting for 58.47% of the area, which is larger than the overall average of 45.08% for Southwest China. This suggests that the karst areas have a greater carbon sequestration potential. However, approximately 10.42% of carbon sinks experience negative reversals. The regions with increasing and positive reversals are primarily located in the western parts of Guizhou and Guangxi, while negative reversals are observed in the eastern parts of Chongqing, Guangxi, and Guizhou. Ecological restoration projects are the main driving factors for the carbon sinks with increasing trends. Increased humidity and ecological restoration management are the main reasons for the positive reversals of carbon sinks. However, warming and drought shift the carbon sinks from increasing to decreasing in Chongqing, east of Guangxi and Guizhou. The findings of this study highlight the significant role of ecological restoration projects and reexamine the impact of climate change on carbon sequestration.

Comparison of Soil Microbial Community between Managed and Natural Vegetation Restoration along a Climatic Gradient in Karst Regions

Managed and natural vegetation restorations are two vital measures of land restoration; however, their effects on soil microbial communities at a large scale are not clearly understood. Hence, changes in the microbial community composition after 15 years of vegetation restoration along a climatic gradient in the subtropical karst region of Southwest China were assessed based on phospholipid fatty acids (PLFAs) profiles. Managed (plantation forest) and natural (naturally recovered to shrubbery) vegetation restoration types were compared, with cropland and mature forest serving as controls. Soil microbial community abundance was significantly higher under the two vegetation restoration types than in the cropland; however, it was lower than in the mature forest. The abundance, composition, and structure of soil microbial communities did not differ significantly between plantation forest and shrubbery. Soil organic carbon or total nitrogen was the primary factor positively affecting soil microbial abundance, whereas the mean annual temperature (MAT) was recognized as the primary factor contributing to the variation in the soil microbial community structure. Moreover, temperature had opposite effects on different indicators of microbial community structure. That is, it positively and negatively affected the ratios of gram-positive to gram-negative bacterial PLFAs (GP:GN) and fungal to bacterial PLFAs (F:B), respectively. Our results show that both vegetation restoration types have the ability to improve soil productivity in karst areas. Furthermore, shifts in soil microbial community structure (GP:GN and F:B ratios) induced by warming are likely to lead to a higher proportion of labile carbon, which is sensitive to soil tillage. Hence, more attention should be paid to ecological restoration in warmer karst areas to alleviate the severe loss of soil carbon in croplands.

Vegetation restoration in South China’s karst region under geological background constraint: Forest or non-forest

Over the past two decades, the karst region in southern China has emerged as a critical area for ecological conservation and restoration, attracting global attention for its efforts in ‘greening.’ However, particular areas face challenges transitioning into forests due to the carbonate bedrock constraint, which likely undermines sustainability of greening efforts in karst regions. This study overviews the significant achievements in vegetation restoration in the karst region of southwest China, emphasizing the potential of short-term ecological restoration in effectively sequestering carbon, a valuable approach to achieving carbon neutrality in the region. However, combating rocky desertification remains difficult due to geological limitations that hinder large-scale afforestation. Additionally, variations in soil and rock composition impact the success and quality of vegetation restoration, leading to some areas failing to establish forests. Therefore, establishing the goals for rocky desertification control in different regions (enhancement, degradation, or reduction) should be based on current conditions and the evolutionary characteristics of rocky desertification. To facilitate precise afforestation and grass planting in the karst region, factors such as climate, rock conditions, and human-environment relationships should be considered in regional divisions, including natural restoration zones, artificial afforestation zones, grass planting zones, and protected zones.

Identification of priority areas to provide insights for ecological protection planning: A case study in Hechi, China

The prolonged disregard for the Gross Ecosystem Product (GEP) has limited the effectiveness of regional ecological conservation. However, identifying and safeguarding areas with high GEP, and optimizing their distribution and spatial structure, are of great immense for preserving ecosystem services (ESs). Our goal is to refine the spatial configuration of ecological network (EN), and subsequently augment and sustain the stability of ESs. We have specifically chosen Hechi City, situated in the Karst region of southwest China, as our case study. Firstly, we devised a GEP evaluation system to pinpoint crucial areas as ecological sources. Subsequently, we utilized the circuit theory and minimum cumulative resistance model to construct the preliminary EN. Through the circuit theory model identified the key nodes in the EN and optimized the EN. Finally, by combining complex network analysis methods, we evaluated the robustness and topological characteristics of the EN. Our results showed that the area of ecological sources increased from 71 to 161 after optimization. The number of corridors increased from 161 to 423, resulting in an overall increment of 8.8% in the source area. The connectivity and stability of the optimized EN can be significantly enhanced. The addition of new nodes increases the overall importance of the network, making the importance of each node more balanced. Additionally, the complex network analysis method provided a detailed understanding about the spatial topology of the overall and local elements of the EN. The study results can provide a valuable reference for optimizing, restoring and evaluating ENs in karst areas.