Human causes of soil loss in rural karst environments: a case study of Guizhou, China

Bacterial composition and physicochemical characteristics of sorghum based on environmental factors in different regions of China

The fermentation process for Jiang-flavored baijiu using sorghum as the raw material involves a variety of microorganisms. However, the specific physicochemical characteristics of sorghum and microbial composition on its surface have not been fully elucidated. We aimed to perform a comprehensive comparative analysis of the variations in physicochemical properties and surface microflora in waxy sorghum samples from three prominent production regions in China (Renhuai, Jinsha, and Duyun). Multivariate statistical assessments were conducted that incorporated local soil and climate variables. The results showed that Cyanobacteria, unclassified bacteria, Proteobacteria, Firmicutes, and Bacteroidota were the dominant bacteria in these regions. These bacteria were associated with ethyl acetate, ethyl caprylate, ethyl lactate, and butyl groups, which synergistically produce flavorful compounds. The surface bacterial communities were affected by soil total phosphorus, altitude, diurnal temperature range, monthly mean temperature, precipitation, and effective accumulated temperature. The findings of this study provide a new perspective on microorganisms related to Jiang-flavored baijiu and can help establish a reference for the stability of liquor quality.

An investigation into the response of the soil ecological environment to tourist disturbance in Baligou

The purpose of this study is to understand the response patterns of the soil ecological environment of the Macau Wetland Park to different levels of tourist interference and to provide a scientific basis for the rational development of the Bali Gou ecological tourism plan and the protection and management of the scenic area's ecological environment. Combine the methods of field collection and laboratory physical and chemical data analysis to analyze the impact of the strength of tourism disturbance on the soil ecological environment of Baligou. During the tourist activities in Baligou, the human factors in the process have an impact on the physical aspects of the scenic area's soil, such as soil bulk density, color tone, porosity, compactness, capacity, and leaf litter. In addition, pH value, soil enzyme activity, organic matter, and heavy metals in the soil have caused some interference. The overall data show that the dynamic of soil indicators is background area < buffer area < disturbed area,where the sample area is affected by human trampling and infrastructure construction and other disturbances leading to regular changes in the content of Pb and Cr in the sample soil, while the content of other heavy metals is lower than the national standard.The range of the most extreme values of the SRI integrated soil ecological response evaluation index was A1 disturbance area = 4.679 and C1 background area = 1.263, respectively. The larger the value of the SRI response index, the greater the impact and negative effect of the disturbance influence of tourism activities on the soil ecological environment of the scenic area, and the higher the level of response of the soil ecological environment of the scenic area to the disturbance of tourism activities. Moderate and reasonable tourism development activities play a role in promoting soil quality in scenic areas. Therefore, it is suggested to carry out reasonable ecological environment planning and take certain macro-measures to prevent the deterioration of the soil ecological environment, so as to achieve a win-win situation of ecological environmental protection while developing the tourism economy in scenic areas.

Construction and optimization strategy of ecological security pattern based on ecosystem services and landscape connectivity: a case study of Guizhou Province, China

Rapid urbanization and irrational human activities have induced in numerous environmental problems, seriously threatening regional ecological security. The establishment and optimization of ecological security patterns (ESPs) were considered as a nature-based solution and an effective way for sustainable development. In this study, the Guizhou Province, a representative karst mountainous region in the southwest of China, was used as the study region. The ecological sources were identified and optimized through integrating ecosystem services and landscape connectivity, and the ecological resistance surface was corrected by representative features of karst areas. The circuit theory was adopted to extract the ecological corridors and barriers. We found that the three ecosystem services (i.e., water conservation, biodiversity maintenance, and soil conservation) had remarkable spatial heterogeneity. The area of optimized ecological sources was enlarged 4752.14 km². The number of corridors was reduced from 73 to 47 after optimization, with a total length decreased by 1251.97 km. The optimized ecological network structure considerably enhanced ecological connectivity, among the γ index increased by 0.0014, the β index reduced by 0.0833, while the α index did not change significantly. We concluded that quantitatively exploring the impacts of ecological source optimization are significant for enhancing ecological connectivity. The approach of our study proposes a novel idea into the ESP construction that can provide a meaningful reference for ecological protection and restoration.

Accumulation and risk assessment of heavy metals in rice: a case study for five areas of Guizhou Province, China

In the present study, the concentration and accumulation abilities of five heavy metals (Cd, Hg, As, Pb, Cr) in rice were assessed and their human health risk to local citizens had been evaluated. Soil and rice samples (125 samples) were collected from Guiyang (GY), Qiannan (QN), Bijie (BJ), Tongren (TR), and Zunyi (ZY) in Guizhou Province. Heavy metals were measured by inductively coupled plasma-mass spectrometry (ICP-MS) after microwave digestion. The mean concentrations of Cd, Hg, As, Pb, and Cr were 0.58, 0.65, 12.31, 38.70, and 87.30 mg/kg in soil and were 0.05, 0.005, 0.11, 0.07, and 0.34 mg/kg in rice, respectively. The bioconcentration factors (BCF) decreased with the order Cd > Hg > As > Cr > Pb. Non-carcinogenic risk in this study was evaluated using the method of the hazard quotient (HQ) and hazard index (HI). The mean HQ values for Cd, Hg, Pb, and Cr were all lower than the standard limit (1.0) for children and adults, except As with the mean HQ for children of 2.79. The mean HI values for children and adults were 4.22 and 1.42, which exceeded 1.0. The mean carcinogenic risk (CR) values of As and Pb for children and adults were higher than the upper limit of the acceptable range (1 × 10^-4) established by the United States Environmental Protection Agency (USEPA). In a conclusion, the non-carcinogenic and carcinogenic risks induced by heavy metals for children were higher than that for adults. This study revealed that consumption of rice in study areas may pose potential non-carcinogenic and carcinogenic risks to humans, and As was the largest contributor.

Sustainable Agricultural Development Models of the Ecologically Vulnerable Karst Areas in Southeast Yunnan from the Perspective of Human–Earth Areal System

Rocky desertification in ecologically-fragile karst areas limit regional socio-economic development in the face of significant human–earth conflict. Coordination of ecological restoration and agricultural development is critical for sustainable development in karst areas. From the perspective of the human–earth areal system, the framework of sustainable agricultural development was proposed in typically karst areas. We integrated principles of ecological vulnerability, resource and environmental carrying capacity, agricultural foundation, suitability of agricultural land, and the farmers’ willingness. In this study, we found the ecological vulnerability of Guangnan County was slight, but the proportion of moderate and severe vulnerability areas was high, with significant differences between the two sides of the line “Zhe (Zhetu)-Lian (Liancheng)-Yang (Yang Liu-jing)-Ban (Banbang)”. Then, we divided Guangnan County into three ecologically vulnerable zones. Following that, we proposed sustainable agricultural models for various zones. In slightly to mildly vulnerable zones, we propose constructing economic–ecological agricultural models, including woody oil, plateau characteristic fruiting forest, ecological tea plantations, suburban agriculture, and cultural–ecological tourism. In moderately to severely vulnerable zones, we recommend developing a stereoscopic agriculture model that combines planting and breeding, vegetation restoration, and herbivorous animal husbandry. In extremely vulnerable zones, we suggest constructing an ecologically natural restoration model and an agricultural ecological–tourism model. Our research provides references for ecological restoration, agricultural development, poverty alleviation consolidation, and rural revitalization in ecologically vulnerable karst areas of southeast Yunnan and similar regions.

The environmental, economic, and social development impact of desertification in Iraq: a review on desertification control measures and mitigation strategies

The threat of desertification is considered a global concern that occurs in many environments in different parts of the world, where extensive lands are transformed gradually into desert or semi-desert areas, and this causes economic and health issues. Iraq and many other parts of the Middle East are facing desertification threats in the last twenty years. Despite the significance of this issue, relevant reviews are scarce. The removal of vegetation cover, overgrazing, deforestation in times of war, poor irrigation practices and water scarcity are some of the main causes of desertification in Iraq. Fighting desertification requires cooperative efforts including the utilization of innovative practices, biotechnological approaches, restoration of oases, continuous reforestation, and rehabilitation of agricultural lands. The objective of this review article is to discuss the causes of desertification and land degradation in Iraq, highlighting the main natural and human factors involved, and the consequent impact on the national security, economy, society, and health. In addition, it suggests recommendations for policies and actions that can be integrated to mitigate this problem.

The Impact of Tourism on Ecosystem Services Value: A Spatio-Temporal Analysis Based on BRT and GWR Modeling

The healthy development of the ecosystem and tourism in destinations plays an essential role in sustainable development. Taking Shennongjia as an example, we analyzed the spatial–temporal variation in the ecosystem services value (ESV) and investigated the impacts of tourism on ESV and their spatial heterogeneity using the geographically weighted regression (GWR) and boosting regression tree (BRT) models. The results showed that (1) the types of ecosystem services (ESs) were dominated by climate regulation and biodiversity. The ESV increased from 3.358 billion yuan to 8.910 billion yuan from 2005 to 2018 and showed significant spatial divergence, maintaining a long-term distribution pattern of high in the center and low at the border. (2) The GWR and BRT results showed that the Distance to Scenic Spots (DSS) and the Distance to Residential Areas (DRA) are important factors influencing ESV, with the Distance to Hotels (DH) and the Distance to Roads (DR) having a relatively weak influence on ESV. (3) The influencing factors presented positive and negative effects, and the degree of influence has spatial heterogeneity. The DRA and DH inhibited the increase in ESV in nearby areas, while DR was the driving factor for increasing ESV. The assessment results of DSS vary according to the models.

Sources and migration of heavy metals in a karst water system under the threats of an abandoned Pb-Zn mine, Southwest China

Water quality is of great concern under the threats of an abandoned Pb-Zn mine within a vulnerable karst area. This study focuses on tracing the sources, migration and relevant geochemical controls of heavy metals along with surface- and groundwater flow, and assessing their hazards posed to the environment by indexes of heavy metal pollution (HPI) and ecological risks (ERI). We analyzed the concentrations of lead (Pb), zinc (Zn), cadmium (Cd) and copper (Cu) in filtered and digested surface water (SW) and groundwater (GW) samples. Whilst sulfate concentrations, δ³⁴S_SO4 isotope, and other physical-chemical parameters were measured in filtered SW and GW. Clearly elevated concentrations of Zn and Cd have been observed in the upstream of the Sidi River (max. 1540.3/1676.7, and 19.9/19.4 μg/L, for filtered/digested contents, respectively), and that of digested Pb and Cu (max. 17.8 and 114.6 μg/L, respectively) in the downstream karst groundwater. Zn and Cd are likely introduced by the Sidi River which is found mostly in the dissolved phase. While Pb and Cu are sourced from the remobilization of upper lying polluted soil which mostly existed in the particulate phase. Zn and Cd concentrations in the karst groundwater peak at the losing section while Pb and Cu in the river peaks at the gaining section as a result of metals transport with SW-GW exchange. Dilution significantly decreases total metals concentration in the non-karst area. Due to the buffer effect caused by carbonates dissolution and bacterial sulfate reduction, a steady neutral pH can reduce the concentrations of the dissolved metals in the karst area. The ERI and HPI assessments show an acceptable level for surface- and groundwater. A long-term observation on the contents of undissolved metals needs to be conducted in karst areas which are threatened by metal(s) mines.

Effects of hydrogeochemical conditions on the distribution of pesticides in the karst river system

Karst aquifer systems are tended to be polluted compared to other types of aquifers because pollutants are able to enter aquifers through developed conduit systems. To identify the effects of hydrogeochemical conditions on the distribution of pesticides in a karst river system in Kaiyang, southwest China, a typical pollution mode combining intermittent infiltration with intrusion was constructed. Twelve aqueous samples were collected along the karst river, and a total of 24 pesticides were detected. The results showed that the pesticide ubiquity and the dominant organophosphate (40%) and organonitrogen pesticides (49%) were both observed. Based on the spatial distribution, the attenuation of pesticides was found in the underground conduit and surface river. The wastewater treatment plant and the rural dump were the two important point sources releasing pesticides. In addition, ten core pesticides were identified by clustering analysis and regional characteristics of three types of pesticides in Songnen Plain, North China Plain, and Southwest karst areas were also summarized. With correlation analysis between pesticides and environmental factors, the significant correlations of pesticides with ammonium ion and dissolved oxygen were found, which indicated that rapid developing urbanization and long-term agricultural practices could remarkably affect the spatial distribution of pesticides. The calculation of ecological risk quotients showed that organophosphate pesticides had the highest risk to invertebrate, followed by organonitrogen pesticides, and finally organochlorine pesticides. Invertebrates were the most vulnerable aquatic organisms. These findings fill a gap in the multiple pesticides' pollution in the karst areas of China. Graphical abstract.

An Assessment of Soil’s Nutrient Deficiencies and Their Influence on the Restoration of Degraded Karst Vegetation in Southwest China

The distribution of karst landscapes over the Earth’s surface, to a large extent, follows the distribution of carbonate (limestone and dolomite) and gypsum rocks and together these make up about 12% of the Earth’s land area, and the largest karst region in to world is in Southwestern China. Characterized by a unique set of landforms, these geographical areas also differ from other geomorphic regions by the presence of cave systems in the subsurface. Unfortunately, due to human disturbances, such as deforestation, agricultural expansion, livestock overgrazing and fire, these regions have been affected by varying degrees of degradation, which could also be worsened if water and soil erosion phenomena typical of these areas are considered. Therefore, there is a need to implement measures and strategies to protect these karst areas and develop plans to restore vegetation in this region. To support local and national authorities to achieve this goal, this study aims to characterize nutrient deficiencies in degraded areas and estimate what could be the thresholds required to facilitate the restoration of vegetation in karst areas in southwest China. The results obtained confirm that the total element concentrations for Soil Organic Carbon (SOC), N, K, Ca, P, S and Mg were relatively high in the study karst area in southwest China. However, the total amounts of soil nutrients stored were very low due to the limited amount of soil identified as a consequence of previous deforestation processes undertaken within this study area and this aspect needs to be taken into consideration if aiming at a positive success of future restoration processes.

Anthropogenic Disturbances and Precipitation Affect Karst Sediment Discharge in the Nandong Underground River System in Yunnan, Southwest China

In fragile karst environments that have seen past and current human exploitation of agricultural and forest resources, the quantification of underground riverine sediment has been widely used to evaluate subterranean stream basin erosion. These measures are highly influenced by both precipitation and anthropogenic factors; therefore, soil erosion control measures must be urgently designed and applied. In this study, 17 years of sediment discharge across the Nandong underground river system in southwest China was monitored. To achieve this goal, the Mann–Kendal mutation test and proxy indicators were used to estimate the general influence of human activities and precipitation on sediment discharge. The results showed that: (1) Both anthropologic disturbance and rainfall have impacted the sediment discharge, although the influence of the anthropologic factor on sediment discharge was greater (61.53%), and (2) rainfall showed a hysteresis effect on sediment discharge. We obtained three different stages based on the mutation points and variation characteristics of the studied sediment discharge resulting from different driving forces, from 1998 to 2014. Prior to 2004, in the whole basin, the decrease of sediment yield was the result of the Natural Forest Protection Project. During the period from 2004 to 2008, due to continuous droughts, flood disasters, and intensive cultivation practices on the steeper hillslopes, the total sediment discharge of the whole basin increased. After 2009, the sediment discharge decreased due to the development of soil conservation projects and mushrooming reservoirs. These findings are expected to provide insights into watershed management and ecological restoration in fragile karst ecosystems, specifically, in southwestern Chinese river systems. More research must be conducted to monitor, with in situ measurements and observations, possible extreme events that can determine the exact erosion control measures that need to be designed and applied.

A Vulnerable Environment Study in Karst Regions between 1991 and 2017: A Bibliometric Analysis

In order to understand the research hotspots and the development directions in the field of vulnerable karst environment, we undertook bibliometrics citation analysis on 5425 contributions to the literature written in the range from 1991 to 2017 based on the “Web of Science” core collection citation index database. Hopefully, this work will help to set up a scientific foundation for further studies. This research considered the following factors: keywords frequency, influence of author, research hotspot, reference citation network, research institution and the evolution of research topic. It was revealed that the research interests were focused on water, cave, and soil environments and implicated trends switching from a water environment to cave and eco-environment and from ecological restoration and rehabilitation to karst rocky desertification. A European-American-Chinese centered cooperation network has shown its initial form. This research will offer researchers a bird’s eye view of the global vulnerable karst environment and point out the directions of further study.