Rocky Desertification Research Articles

Extraction of Rocky Desertification Information in the Karst Area Based on the Red-NIR-SWIR Spectral Feature Space

The complex topography, severe surface fragmentation and landscape heterogeneity of the karst region of southwest China make it extremely difficult to extract information on rocky desertification in the region. In order to overcome the disadvantages of the surface parameter-based feature space approach, which is difficult to construct and apply, this study uses the reflectance of Landsat 8 Operational Land Imager (OLI) in the red (Red), near-infrared (NIR) and shortwave infrared (SWIR) bands as the feature variables, and establishes a two-dimensional SWIR-NIR, Red-NIR and SWIR-Red reflectance spectral feature space. The three models of perpendicular rocky desertification index 1 (PRDI1), perpendicular rocky desertification index 2 (PRDI2) and perpendicular rocky desertification index 3 (PRDI3) were also constructed based on the variation of the degree of rocky desertification in each spectral feature space. The accuracy of the rocky desertification extracted by these three index models was verified and compared with the karst rocky desertification index (KRDI) and rocky desertification difference index (RSDDI), which are constructed based on the surface parameter feature space. The results show that: (1) The waveband reflectance-based feature space model provides a new method for large-scale rocky desertification information extraction, characterized by easy data acquisition, simple index calculation and good stability, and is conducive to the monitoring and quantitative analysis of rocky desertification in karst areas. (2) The overall accuracy and Kappa coefficient of PRDI1 are 0.829 and 0.784, respectively, both higher than other index models, showing the best applicability, accuracy and effectiveness in rocky desertification information extraction. (3) According to the results extracted from PRDI1, the total area of rocky desertification in Huaxi District of Guizhou province is 320.44 km2, with the more serious grades of rocky desertification, such as severe and moderate, mainly distributed in the southwestern, western and southeastern areas of Huaxi District. This study provides important information on the total area and spatial distribution of different degrees of rocky desertification in the study area, and these results can be used to support the local government’s ecological and environmental management decisions. The method proposed in this study is a scientific and necessary complement to the characteristic spatial methods based on different surface parameters, and can provide important methodological support for the rapid and efficient monitoring of karstic rocky desertification over large areas.

Could the Sloping Land Conversion Program Promote Farmers’ Income in Rocky Desertification Areas?—Evidence from China

The Sloping Land Conversion Program (SLCP) is a significant measure to achieve the Sustainable Development Goals (SDGs) proposed by the United Nations in 2015. SLCP plays an important role in poverty alleviation and income increase for farmers in poor areas. The purpose of this study is to analyze whether the income of farmers has increased after participating in SLCP, and whether SLCP has released the agricultural labor force to obtain non-agricultural income by participating in non-agricultural work. Based on the field investigation in Luocheng County and Longsheng County of Guangxi, Libo County, and Dushan county of Guizhou, this paper uses the method of propensity score matching (PSM) to explore the impact of SLCP on the income of farmers in rocky desertification areas. According to our research, it is found that: (1) SLCP has a positive effect of 5.2% on the average annual net income of farmers, a positive effect of 43.2% on agricultural income, and a negative effect of 9.8% on non-agricultural income, but all of the effects are insignificant. Selective deviation will overestimate the impact of SLCP on farmers’ total income and agricultural income and underestimate the impact on non-agricultural income. SLCP failed to promote the transformation of farmers into secondary and tertiary industries. The mechanism of SLCP to increase farmers’ income is complex. (2) Farmers’ participation in SLCP is influenced by work experience and education level in human capital, participation in skills training in social capital, and owning durable consumer goods in physical capital. Although SLCP will promote economic development under the condition of improving the ecological environment in the future, it is not advisable to exchange farmers’ livelihood for ecological construction at present. The implementation of SLCP should consider not only the overall ecological benefits, but also the short-term social and economic benefits.

Dynamic Changes in Agroecosystem Landscape Patterns and Their Driving Mechanisms in Karst Mountainous Areas of Southwest China: The Case of Central Guizhou

Puding County in central Guizhou is a typical karst ecologically vulnerable area integrating rural, mountainous, and ecological migration areas. It is essential to study the dynamic trajectory and direction of its agroecosystems (AESs) transformation to promote sustainable land use development in karst mountain areas. Based on high-resolution remote sensing images from 2004 to 2020, this study analyzes the transformation characteristics, typical landscape patterns, and their driving forces of AESs using the landscape pattern index, moving window method, and Geodetector model. The results show that: (i) The overall landscape pattern of AESs in the study area developed towards complexity and diversification from 2004 to 2020. The overall trend of woodland and grassland (WGL) is increasing, the slope cultivated land (SCL) is shrinking, the construction land (CL) is spreading and expanding along the vicinity of the town, and the economic and fruit forests (EFF) are increasing significantly. (ii) Three typical patterns are concluded according to the main transformation directions of AESs: WGL restoration type, CL growth type, and EFF growth type; middle and high mountains are dominated by the WGL restoration type with increased ecological functions, and the concentration of the new WGL increases with the increase in elevation; low mountain areas are dominated by the CL growth type with enhanced living functions, and the concentration of the new CL decreases with the increase in slope and elevation; valleys and hills are dominated by the EFF growth type with enhanced ecological and economic functions, and the concentration of the new EFF increases with the decrease in slope and elevation. (iii) Socio-economic factors are the dominant drivers of AES transformation. The WGL restoration type is dominated by slope and elevation, the CL growth type is mainly influenced by slope and urbanization rate, and the EFF growth type is primarily influenced by soil organic matter, slope, urbanization rate, and resident population. The study results have implications for rural land use, rural development, and ecological restoration of rocky desertification in karst mountain areas and other similar mountainous areas.

Evaluation of Soil Rocky Desertification in Karst Region Based on Deep Belief Network

Abstract Dynamic features from remote sensing photos may be successfully extracted using deep learning and symmetric network structure, which can then be used to direct them to carry out accurate classification. The DBN model can more effectively extract features from photos since it uses unsupervised learning. It can be reduced to the many symmetric Restricted Boltmann Machines (RBM) training problem. In this paper, a soil rocky desertification (RD) assessment model based on a deep belief network (DBN) is created in light of the complicated influencing aspects of Karst RD risk assessment encompassing several geographical elements. The model builds upon the conventional RBM framework and incorporates the influence layer of related elements as an auxiliary requirement for retrieving Geographic Information System (GIS) score data. Then, in order to forecast the level of soil rocky desertification, it learns the features of many elements. The experimental results show that the proposed model proposed in this paper has better prediction performance and faster convergence speed, and its classification results for different degrees of RD are more consistent with the actual risk assessment results.

Effects of bedrock strata dip on soil infiltration capacity under different land use types in a karst trough valley of Southwest China

The dip of bedrock has a great influence on the infiltration of water into soil, and can control the spatial distribution of rainwater in fragile karst rocky desertification regions. Thus, it is necessary to scientifically assess the soil infiltration capacity of dip and anti-dip slopes in karst trough valleys. In this study, we comprehensively evaluated the soil infiltration capacity of dip and anti-dip slopes under different land use types using the cutting ring infiltration method. The results showed the following. i) Compared with the anti-dip slope, the dip slope had a higher bulk density, noncapillary porosity and pH and a lower soil water content, capillary porosity and soil organic carbon content (p < 0.05). In addition, the soil infiltration capacity of grassland was the highest among the studied land use types except for abandoned land. ii) Both the bulk density and the total soil porosity could be treated as indicators of the infiltration properties of dip and anti-dip slopes.iii) Based on the coefficient of determination, R2, the common experience model was the most suitable for describing the characteristics of the soil infiltration rate. iv) Based on the principal component equation, the soil infiltration capacity and organic matter of the grassland on dip slopes and anti-dip slopes were higher than those of other land use types with vegetation, but not higher than those of abandoned land without vegetation. The results of this study provide a reference for the selection of the restoration method and the assessment of the soil infiltration capacity of dip and anti-dip slopes in karst trough valleys and other karst landforms with the same geological background.

Evaluation on the adaptability of Yunnan karst ecosystems based on “rock-soil-water-vegetation”

Because of its fragile nature, the karst ecosystem is prone to instability and gradual degradation of the key elements with “rock-soil-water-vegetation” under the continuous interference of human unreasonable activity, resulting in the final formation of the rocky desertification landscape. Based on the research of the structure of karst critical zone, it was proposed to establish the concept of karst ecosystem adaptability with the evaluation system of “rock-soil-water-vegetation”. At the same time, the analysis of the stress and coupling relationship was conducted in combination with the analysis of human activity intensity in Yunnan karst rocky desertification areas. The results showed that: (1) On the county scale, the karst ecosystem adaptability mainly fell into Level 2–3 (0.10 < Ake ≤ 0.30). The contribution degree of indicators followed the order of annual precipitation > proportion of waterbody area, biological abundance index > rock outcrop rate > wetness index, vegetation cover > soil erosion index. (2) The synergistic relationship between karst ecosystem adaptability and human activity intensity was mainly characterized by ecological priority type (S ≥ 1.20), which was mainly found in West, Northwest and Southwest Yunnan. The development priority type (0 < S ≤ 0.80) was mainly centered around Kunming City, extending eastward to Qilin District of Qujing City, southward to Hongta District of Yuxi City, and further to Gejiu-Mengzi-Kaiyuan of Honghe Prefecture and Wenshan City of Wenshan Prefecture. (3) The coupling relationship between the karst ecosystem adaptability and human activity intensity was mainly in the running-in coupling state (0.50 < C ≤ 0.80). The coupling centers were mainly in Kunming City, Yuxi City, Qujing City and Honghe Prefecture (a high-level coupling, 0.80 < C < 1.00). (4) The coordination relationship between the karst ecosystem adaptability and human activity intensity mainly fell into the imbalanced development category, mostly moderately and mildly imbalanced development (0.20 ≤ D < 0.40). The coordinated development center was mainly centered in Kunming City of Central Yunnan (a coordinated development, D ≥ 0.5), which widely extended southward to Hongta-Jiangchuan-Chengjiang -Tonghai in Yuxi City and slightly spread eastward to Qilin District in Qujing City. The research results can provide effective ways and evaluation basis for enhancing the resilience and stability of the karst ecosystem and repairing damaged links, and also provide theoretical support for further studies on sustainable development of karst rocky desertification areas.

The Characteristics of Soil C, N and P and Stoichiometric Ratios as Affected by Land-Use in a Karst Area, Southwest China

Chemometric analysis is often used as an effective indicator of the supply capacity of nutrients in soil–plant systems and their biogeochemical cycles. Understanding ecological stoichiometric characteristics of C, N and P in soils under various land uses is crucial to guide ecological restoration and agricultural cultivation in karst rocky desertification region. However, data on ecological stoichiometry at different land uses in karst areas is limited. This study aimed to evaluate the effects of different land uses on soil ecological stoichiometric ratios and further identify the factors that influence soil ecological stoichiometric ratios. The topsoil from forest, shrub and cultivated land (paddy field and dry land) both in a karst area and non-karst area (as a reference) of Mashan County was sampled to investigate the spatial variance of the ecological stoichiometric characteristics of C, N and P under different land uses. The results show that: (1) Land-use types significantly determined the spatial heterogeneity of soil ecological stoichiometry in karst areas. (2) Soil organic carbon (SOC) was not significantly different between shrubs in the karst area and forests in the non-karst area (p = 0.595), but there were virtual differences in total nitrogen (TN), total phosphorus (TP), C:N, C:P and N:P between shrubs in the karst area and forests in the non-karst area (p &lt; 0.01). (3) The contents of SOC, TN, and C:P, N:P in the study area were all generally higher in forests than those in cultivated land, and the content of TP was lower in forests than cultivated land, while C:N in cultivated land was higher than in shrubs in karst areas, and C:N was higher in forests than in cultivated land in non-karst areas. (4) Available nitrogen (AvN) was the main factor influencing stoichiometry in shrubs in karst areas, while pH, AvN, available phosphorus and elevation were the main factors in forests in non-karst areas, indicating that these factors significantly affect the soil ecological stoichiometric ratio during land-use changes. This study helps to understand the variations in soil ecological stoichiometric ratios under land-use changes. It provides guidance for the sustainable management of revegetation in karst regions in southwest China.

Storage infiltration of rock-soil interface soil on rock surface flow in the rocky desertification area

Rock surface flow, formed from the rock surface of outcrops after receiving rainwater, has become a main form of runoff in rocky desertification ecosystems with frequent regional and seasonal droughts. However, as a main flow path of rock surface flow into the surrounding soil of outcrops, how much the rock-soil interface soil can store and infiltrate the rock surface flow from outcrops is not well known. The goals of this study were to explore the storage-infiltration effect of soil at the rock-soil interface on rock surface flow in rocky desertification areas. Hence, a typical rocky land with large bulk rock outcrops, of which the surrounding soil has experienced five years of rock surface flow, and three special rock surfaces with shapes of convex, straight, and concave with different hydrological paths were selected in a typical rocky desertification county of China. Field investigation, ring knife soaking and infiltration methods were applied to indicate the difference in storage-infiltration between rock-soil interface soil and non-rock-soil interface soil on the rock surface flow in these different rock surface shapes. The results showed that the rock-soil interface soils around outcrops with different rock surface shapes exhibited different storage-infiltration capabilities for rock surface flow. The space of soil carrying water at the rock-soil interface showed the order of the convex shape, the straight shape and the concave shape, in which the non-rock-soil interface soil around the convex shape had greater space, followed by the rock-soil interface soil. The rock-soil interface soil of all three shapes had higher water storage performance than the non-rock-soil interface soil in terms of the field capacity and usable storage, where the rock-soil interface soil at the soil depth of 0–10 cm of the concave shape had lower water storage and lower conservation capacity than the 10–20 cm depth, and this was of positive significance for retaining the rock surface flow. The soil infiltration rate at the rock-soil interface with only the concave shape was greater than that at the non-rock-soil interface, where the concave shape had the greatest soil infiltration rate at the rock-soil interface. The results from this study can be used to understand the influence of outcrops on the soil properties of karst ecosystems.

Rhizospheric soil organic carbon accumulated but its molecular groups redistributed via rhizospheric soil microorganisms along multi-root Cerasus humilis plantation chronosequence at the karst rocky desertification control area.

Though the relationships between the microorganism communities and the edaphic factors in rhizosphere soil along the plantation chronosequence have been widely reported, few researches have appeared on the interrelationship about rhizospheric soil microorganism community and soil organic carbon (SOC) under multi-root Cerasus humilis plantations of different age. In our study, the rhizospheric soil microbial communities, soil physicochemistry, and SOC molecular groups in plantations of 1-, 3-, and 5-year-old Cerasus humilis were investigated in karst rocky desertification control area of southwest China. It was found that karst rhizospheric soil moisture, total nitrogen, available potassium, and 46-60ppm N-alkyl/methoxyl C decreased; however, SOC and fungal:bacterial ratio decreased along multi-root Cerasus humilis plantation chronosequence. Proteobacteria, Actinobacteriota, Acidobacteriota, and Ascomycota were recognized as the top 4 phyla in the karst rhizospheric soil microbial co-occurrence network. Moreover, Cerasus humilis plantations exerted significantly direct effect on rhizospheric soil microbial communities and soil physicochemical properties exerted significantly direct effects on SOC molecular groups. Our results suggested that the increased Cerasus humilis plantation years will promote C sequestration (e.g., SOC) with the continued input of root litter, root exudates, and plant litter. The inputted and activated C can be preferentially consumed by rhizospheric soil microorganisms and converted into microbial-derived compounds, which are finally incorporated into recalcitrant SOC pools. Hence, Cerasus humilis redistributed SOC molecular groups via rhizospheric soil microorganisms, and increased ratio of fungi:bacteria in rhizosphere was associated with C sequestration which could not be regarded as a widespread rule. Though our study is the first attempt to recognize the interaction between rhizospheric soil microbial community and SOC molecular groups at the karst rocky desertification control area, it provides a baseline for further research that ecological restoration can promote soil C sequestration via soil microorganisms in the early period of eco-restoration at karst area.

Ecological restoration projects enhanced terrestrial carbon sequestration in the karst region of Southwest China

The karst region of southwest China showed a significant increase in vegetation cover and vegetation carbon stocks under the implementation of a series of ecological restoration projects. However, the relative contribution of ecological restoration projects to terrestrial carbon sequestration in the context of climate change has yet to be well quantified. Here, we used the Community Land Model (CLM4.5) to investigate the trend of net ecosystem productivity (NEP) and attribution to multiple environmental factors in the karst region of southwest China during 2000–2018. The result showed that ecosystems with a significant increasing trend of NEP covered about 46% of the study region, which were mainly located in the peak forest plain region, colliculus region, peak cluster depression region, and middle-high hill region. The simulation experiments suggested that land use change associated with ecological restoration projects caused a large contribution of 53% to the increasing NEP trend, followed by CO2 fertilization (72%), while climate factors and nitrogen deposition showed minor negative effects. Especially, the NEP trend induced by land use change in the 100 pilot counties with the implementation of rocky desertification control project was significantly higher than that in the other karst area. Moreover, moderate and high levels of restoration efforts invested into recovery led to a larger increasing trend (0.66 gC/m2/yr2 and 0.48 gC/m2/yr2) in NEP than the low efforts level (0.22 gC/m2/yr2). Our results highlight the important role of ecological restoration projects in the enhanced terrestrial carbon sequestration in the karst region of southwest China, and recommend a comprehensive assessment of ecological restoration projects for policymaking.

Vulnerability assessment of urban remnant mountain ecosystems based on ecological sensitivity and ecosystem services

Urban remnant mountains (URMs) are precious natural green habitat patches that can provide a series of ecosystem services for multi-mountainous cities. The increase in ecological sensitivity and degradation of ecosystem services affected by urban expansion and climate change have led to an increasing vulnerability of urban remnant mountain ecosystems (URMEs). To explore the vulnerability of URMEs, taking the central urban built-up area of the Guiyang city as the study area and URMs as the research object, the vulnerability of URMEs under natural factors and human disturbance was analyzed based on the Pressure-State-Response (PSR) model. The results showed that: (1) Karst rocky desertification, human disturbance, and road density within the buffer zones around URMs were the most important factors affecting the vulnerability of URMEs. Karst rocky desertification was the most likely eco-environmental problem of URMs, and carbon storage was the most important ecosystem service of URMEs. (2) Characteristics of fragile karst habitats in URMs and unreasonable human activities led to high ecological vulnerability, mainly with moderate and severe vulnerability predominating, and the low vulnerability of URMEs when they had moderate park utilization. (3) The ecological vulnerability of small URMs and those distributed in the urban center is higher, and the invulnerable URMEs and the slightly vulnerable URMEs are mainly distributed in the urban edge. The results of this study could provide references for ecological restoration and protection of URMs, and offer a basis for improving the resilience of multi-mountainous cities.

The difference in leaf color quality of Cotinus coggygria during the coloration peak period affected by soil and topographic heterogeneity

Leaf color quality that measures the gorgeous degree of plant’s foliage with a specific color during a coloration period, has been related to the biological function of colored plants and the development of ecotourism. The difference in leaf color quality of Cotinus coggygria and its key environmental factors during the coloration peak period in a karst area were explored based on leaf color parameters (i.e., L*, a*, b*, and c*), pigment indices (i.e., chlorophylls, carotenoid, anthocyanin, myricetin, quercetin, and kaempferol), and environment variables (i.e., soil properties, topography, and vegetation community characteristic) by principle component analysis, random forest model, and hierarchical cluster analysis. The results indicated that the leaf color quality index based on the minimum data set including the total chlorophyll, anthocyanin, and quercetin could accurately reveal the difference in leaf color quality of Cotinus coggygria in our study area. The coefficient of variation in leaf color quality index was 25.47%, which suggested that the leaf color quality of Cotinus coggygria had spatial heterogeneity. This heterogeneity was closely related to soil properties (e.g., total phosphorus, total potassium, and available potassium) and topographic variables (e.g., slope height and elevation). Specifically, the leaf color quality of Cotinus coggygria was higher in the middle- and low-elevation areas with less soil nutrients (i.e., total phosphorus, total potassium, and available potassium) and higher slope height, but lower in the high-altitude areas with more soil nutrients and lower slope height. Moreover, the leaf color quality of Cotinus coggygria in shrubbery was higher than that in mixed forest, suggesting that the vegetation community characteristic is another important factor of the leaf color quality in the study area. These results can provide a theoretical basis to quantify the difference in leaf color quality of colored plants during the coloration peak period and improve the ornamental value of colored plants in rocky desertification areas.

Influence of Different Planting Combinations on the Amino Acid Concentration in Pericarp of Zanthoxylum planispinum ‘Dintanensis’ and Soil

In this study, the effect of different planting combinations on the amino acid concentration in the pericarp of Zanthoxylum planispinum ‘dintanensis’ (hereafter referred to as Z. planispinum) was studied, and the response of amino acid concentration to soil factors was clarified. The aim of this study was to screen optimal planting combinations and provide a theoretical basis for improving pericarp quality. Five planting combinations of Z. planispinum in a karst rocky desertification area were selected as the research objects, and the concentration and accumulation of free amino acids in the pericarp of Z. planispinum were analyzed. Then, combined with existing soil quality data, the pericarp quality of Z. planispinum was comprehensively evaluated by principal component analysis, and the effect of soil factors on amino acid concentrations was clarified by redundancy analysis. The results are as follows: (1) except for arginine, serine, proline, alanine, tyrosine and cystine, the concentrations of other free amino acids significantly differed among the five planting combinations. In general, the planting combination has a great influence on the concentration of free amino acids in the pericarp of Z. planispinum, especially essential amino acids; (2) free amino acid concentration in the pericarp of Z. planispinum mostly increased in combination with Sophora tonkinensis Gagnep. (hereafter referred to as S. tonkinensis) and decreased in combination with Prunus salicina Lindl; (3) principal component analysis showed that the concentration of free amino acid in the pericarp of Z. planispinum was generally at a high level when combined with S. tonkinensis or Lonicera japonica Thunb. (hereafter referred to as L. japonica). Among them, the amino acids in the pericarp of Z. planispinum with S. tonkinensis were closer to the ideal protein standard of FAO/WHO; (4) soil-available potassium, available phosphorus, microbial biomass nitrogen, available calcium and microbial biomass phosphorus in soil factors had significant effects on amino acid concentration after a redundancy analysis. It can be seen that the available nutrients and soil microbial biomass contribute greatly to the amino acid concentration of the pericarp. According to the soil quality and the amino acid quality of the pericarp, planting with L. japonica can improve the amino acid quality of the pericarp of Z. planispinum, as well as selecting Z. planispinum + L. japonica as the optimal planting combination.

Water Retention Evaluation of Slab Trench on Rocky Desertification Slope in a Karst Area of Southwest China

Soil erosion and water loss are serious problems on the rocky desertification slopes in the karst dynamic system of southwest China. The lack of soil and shortage of water restrict the ecological restoration of the regional slopes and utility of water resources. Therefore, a new slab trench capable of storing soil and water in layers on rocky desertification slopes is introduced in this paper to promote vegetation restoration. To explore the water-storing and -holding capacity of the new type of vegetated slab trench, five groups of model experiments were carried out on the vegetated slab trench under different rainfall intensities and different numbers of plants. Under rainfall and then following dry conditions, the effects of rainfall intensity and the number of plants on the water-storing and -holding capacity of vegetated slab trench models were compared and analyzed. Water-storing and -holding capacity was further explored in three groups of models with single planting or combinations of plants including water stored only in succulent root plant, only in succulent stem plant, or in mixed plants. The test results show that the new type of vegetated slab trench can effectively help to store and hold water. In the rainfall period, due to the runoff of the rainfall not being considered, the greater the rainfall intensity, the higher the water storage efficiency; the more vegetation implanted, the greater the blocking effect of the plant canopy during falling rainwater, and the more reduction is induced on the water storage efficiency of the vegetated slab trench. In the following dry period, both the succulent root plant and succulent stem plant have strong water storage capacity, but the succulent root plant has a stronger capacity for water storage. The growth status of the mixed plants was better than that of single planting, which may be due to the water complementarities between the succulent root plant and succulent stem plant in a mixed planting manner. This study is important for solving the problem of soil erosion and water loss in rocky desertification slopes, and it helps to restore the ecological environment of the area.

Spatiotemporal distribution and attribution of carbon sequestration in karst rocky desertification land in southern China

&lt;p&gt;To mitigate the intensification of desertification and land degradation in karst areas of southern China, since the late 1990s, the Chinese government has implemented a series of ecological restoration projects. In the past couple of decades, the carbon sequestration potential of karst rocky desertification land increased significantly. However, few studies have explored the characteristics and driving mechanisms of carbon sequestration in karst areas. This study aimed to quantify the spatiotemporal patterns, trends, and drivers of carbon sequestration in the Huajiang River Basin, a typical karst basin, in southern China during 2000-2020 and its five geographic zones via the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. The five zones of the karst basin exhibited the following characteristics: (I) good natural background condition with positive feedback human intervention; (II) poor natural background condition with increased negative and decreased positive feedback human interventions; (III) poor natural background condition with increased positive and decreased negative feedback human interventions; (IV) non-karst land; and (V) poor natural background condition with no significant positive and negative feedback human interventions and with heavy reliance on natural ecosystem recovery. The results were four-fold. First, the Huajiang River Basin showed a significant increasing trend of carbon sequestration. The spatiotemporal variation of carbon sequestration significantly differed among the five zones (Ⅴ &amp;gt; Ⅲ &amp;gt; Ⅳ &amp;gt; Ⅱ &amp;gt; Ⅰ). The stability of carbon sequestration was lowest in zone III. Second, a 20-y&lt;span style="font-family: 'Times New Roman';"&gt;ear&lt;/span&gt; land-use/cover change directly affected the level of carbon sequestration. The conversion of cropland, grassland, and woodland to shrubland was the main reason for the increased carbon sequestration in zone I. Third, carbon sequestration was negatively correlated with the desertification level of karst rocky areas. The spatial distributions of moderate, serious, and extremely strong desertification levels in zone II showed an increasing trend. Zones I, III, and V exhibited no significant desertification. Finally, the integrated ecological management against desertification increased carbon sequestration. Negative feedback human interventions (e.g., quarrying) exerted a significant disturbing impact on carbon sequestration that needs to be addressed in the formulation of management practices.&lt;/p&gt;

Study on the Regulation Mechanism of 1-MCP Combined with SO2 Treatment on Postharvest Senescence of Bamboo Shoots (Chimonobambusa quadrangularis) in Karst Mountain Area

Fresh bamboo shoots (Chimonobambusa quadrangularis) are subjected to senescence (e.g., lignification and browning) during postharvest storage. This study investigated the effects of 1-MCP and SO2 treatment on bamboo shoot senescence and its regulation mechanism in order to extend bamboo shoot storage time. 1-MCP and SO2 treatments significantly inhibited the browning and lignification of fresh bamboo shoots during storage, according to the results. Its lower browning index and lignin content are directly related to its lower lignin content compared to the CK control group. The browning index and lignin content of the 1-MCP + SO2 treatment during the late storage period were 90.55% and 81.50% of the CK treatment, respectively. The result of the in-depth analysis suggested that 1-MCP and SO2 treatments reduced nutrient loss and maintained the nutritional value of bamboo shoots by inhibiting respiration and physiological metabolism. The PPO activity was inhibited to inhibit the browning process. Moreover, the scavenging ability of ROS was enhanced, the accumulation of MDA was inhibited, and the senescence of bamboo shoots was delayed after higher contents of total flavonoids and ascorbic acid were maintained and the activities of ascorbic acid peroxidase and superoxide dismutase were stimulated. Furthermore, lignin biosynthesis was hindered, and the lignification of bamboo shoots was delayed after the activities of POD and PAL were inhibited. In brief, 1-MCP + SO2 treatment is capable of inhibiting the physiological metabolism, browning, and lignification of bamboo shoots, maintaining good quality during storage, and delaying the senescence of bamboo shoots. Clarifying the senescence mechanism of bamboo shoots is of great significance for expanding the bamboo shoot industry and slowing down rocky desertification in karst mountainous areas.

Long-term responses in different karst agricultural production systems to farm management and climate change: A comparative prefecture-scale study in Southwest China

Rapid shifts have occurred in the agricultural production systems of the karst regions in Southwest China to meet increasing food demands. The responses of agricultural production vary under different degree of rocky desertification. However, the interactive effects of related driving factors on the food production sustainability of local crops are unknown. In this study, we quantified the impacts of seven key indicators—population, cropland area, multiple cropping index, irrigation area, fertilizer use, temperature and precipitation—on agricultural production in three rocky desertification grade regions from 1960 to 2011. We also classified these indicators into three categories: population, farm management and climate change. The results showed that farm management and population were the main drivers of increased food crop production, contributing 79.7% and 17%, respectively. In contrast, climate change had a limited influence on agricultural production. With increases in crop yield, the influences of some indicators were enhanced, and the negative impact on the environment was also increased; therefore, the sustainability of agricultural production systems could be adversely affected in the future. The agricultural production systems in mild rocky desertification areas (Zunyi) could meet the current food demands, while the areas with moderate and severe rocky desertification (Bijie and Qianxinan, respectively) are faced with substantial pressure. Although continuous improvements in agricultural production efficiency due to advances in modern science, technology and management have partly mitigated environmental pressure, rocky desertification poses a challenge to the sustainable development of agriculture in Southwest China. These findings provide a reference for adjusting farm management practices and climate change countermeasures in regions with different degrees of rocky desertification to achieve agricultural production sustainability in the future.

Research on the Resilience Assessment of Rural Landscapes in the Context of Karst Rocky Desertification Control: A Case Study of Fanhua Village in Guizhou Province

The ecological rehabilitation project has greatly curbed the serious problem of karst rocky desertification (KRD) in southern China and significantly changed the ecological environment and landscape pattern of the karst rocky desertification control areas (KRDCA). As one of the most important social–ecological fragile areas in the world, rural landscapes in KRDCA still show a strong sensitivity to disturbance. To reduce risks and improve the resilience of landscapes, this paper constructs a framework for assessing rural landscape resilience in KRDCA from the three dimensions of ecology, engineering, and social culture, based on the concept of resilience defined by the United Nations International Agency for Disaster Reduction. Considering the characteristics of rural landscapes in KRDCA, we select typical villages for empirical study. The results show the following: (1) The KRDCA is highly sensitive to natural disasters due to its special dual geomorphic structure characteristics. The disaster preparedness capacity of villages is the key factor determining the resilience of rural landscapes. The analysis of the disaster preparedness capacities of rural landscape structures with different vulnerability characteristics can be used as an effective means of evaluating the resilience level of rural landscapes in KRDCA. (2) Based on the empirical analysis of Fanhua village, which is a typical KRDCA in southern China, we found that the ecological system and engineering system of the village landscape have high resilience, while the resilience of the social and cultural systems are weak. This is due to the fact that the large number of rural population emigration in recent years has resulted in villages being at the key node of the reorganization of the social and cultural value system. The unstable sociocultural value system reduces the ability of rural landscapes to adapt to disturbance or environmental change. The study results could guide improvement strategies for subsequent landscape planning and inspire new ideas and methods for the implementation of rural revitalization strategies and the improvement of landscape resilience in KRDCA.

Changes in Plant Diversity and Soil Factors under Different Rocky Desertification Degrees in Northern Guangdong, China

Revegetation is an important restoration strategy for the control of rocky desertification. However, few studies have focused on the effects of different rocky desertification degrees (RDDs) on plant diversity and soil fertility in northern Guangdong over long periods of time. In this study, variance analysis, correlation analysis, and canonical correlation analysis (CCA) were used to examine plant diversity, soil physicochemical properties, and their correlations in various rocky desertification areas in northern Guangdong. The results showed that the Pinaceae, Lauraceae, and Fagaceae species were relatively abundant in the rocky desertification areas of northern Guangdong. Additionally, Cinnamomum camphora, Schima superba, Pinus massoniana, Quercus stewardiana, and Acer camphora could be used as indicators for rocky desertification. There were significant differences in plant community compositions and diversity characteristics between the five RDDs, and the vegetation exhibited the trend of initial destruction and then gradual improvement and stabilization. There were significant differences in soil bulk density, mechanical composition, organic matter, total nitrogen, alkaline hydrolysis nitrogen, and available potassium between the different RDDs. Except for pH, the soil chemical characteristics all had clear aggregation effects. Soil organic matter, total nitrogen, total potassium, and alkaline hydrolysis nitrogen all exhibited degradation–improvement cycles. The correlation analysis revealed that there was a significant correlation between soil physicochemical properties and species diversity. The CCA analysis showed that the most important soil factors affecting plant community structures were total phosphorus and available phosphorus. In conclusion, some achievements have been made in the restoration of rocky desertification in northern Guangdong; while the plant community structure improved, some soil nutrients also improved. Vegetation and soil have a strong coupling relationship. In the later stages of recovery, suitable species for rocky desertification could be considered in varying degrees and P and K could be supplemented appropriately. Our study will have implications for the revegetation of rocky desertification.

Soil aggregate stability and its response to overland runoff–sediment transport in karst peak–cluster depressions

Karst peak–cluster depressions are ecologically fragile, and slope runoff is a cause of severe soil erosions. However, the runoff–sediment pattern and influencing factors of typical lithologies slope erosion are still unclear. This study investigated the soil aggregate stability of limestone and dolomite and their effects on interrill erosion using rainfall tests. The dolomite soil aggregates were smooth with fine, tightly arranged particles. The limestone soil aggregates were rough with regularly shaped flocculent granular bodies. Soil aggregates of limestone had a higher microporosity than that of dolomite. The contents of macroaggregate with a particle size > 0.25 mm (WSA0.25) were significantly higher in limestone soils than in dolomite soils (P < 0.05). The mean weight diameter (MWD) trend was consistent with the WSA0.25 value. The MWD value for forest soil of limestone was the highest among all soil types, 5.65 mm. With the Le Bissonais (LB) method, the MWD values followed the order of limestone > dolomite soils. The organic matter, Ca and Mg contents were highly significantly correlated with the aggregate stability (P < 0.01). During rainfall, the trend for soil runoff rates mainly indicated three stages: 0 ∼ 10 min, rapidly increasing; 10 ∼ 30 min, fluctuating; and 30 ∼ 60 min, essentially stable. The stable runoff rates of limestone soils were lower than that of dolomite soils. At a slope of 10°, the soil loss rate of dolomite forest was 0.16 g/(min·m2) higher than that of limestone. The sediment concentrations of dolomite soils were higher than those of limestone soils. The sediment aggregates were dominated by macroaggregates. The content of macroaggregates in dolomite soils ranged from 49.54% to 64.84% at 30 min of runoff and ranged from 51.60% to 69.88% in limestone soils. In general, limestone soils experienced less erosion than dolomite soils because of the difference in soil aggregate stability. The results of this study could provide a theoretical reference for karst rocky desertification management and ecological restoration.