Huanjiang County Research Articles

The Effects of Different Vegetation Restoration Models on Soil Quality in Karst Areas of Southwest China

Rocky desertification is a devastating process in Karst areas of Southwest China and induces serious fragmentation in ecosystems. Therefore, vegetation restoration and the scientific evaluation of soil quality are key restorative strategies in these areas. In this study, a natural closed forest and a disturbed forest with three restoration models, including an evergreen broad-leaved forest, mixed forest, and deciduous forest, were investigated in Huanjiang County. More than nineteen soil properties (including physical, chemical, and biotic properties) were analyzed across treatments, and principal component analyses (PCA) were combined with a minimum data set (MDS) applied to evaluate the soil quality. Our study sought to identify a vegetation restoration model to improve the soil quality in this area. We demonstrated that soil physical and chemical properties, microbial biomass, and enzyme activities significantly differed across all of the models. Soil water content, capillary porosity, total porosity, organic carbon, total phosphorus, available phosphorus, and urease activity were high in the mixed forest, leading to better physical soil properties. Also, relatively high soil total nitrogen, total potassium, available nitrogen, available potassium, microbial biomass C and N, catalase, sucrose, and alkaline phosphatase levels were observed in the deciduous broad-leaved forest, resulting in improved soil chemical properties. Based on the minimum data set (MDS) method, six indicators, including non-capillary porosity, organic carbon, total phosphorus, pH, microbial biomass nitrogen, and urease activity, were selected to evaluate the soil quality across the models. Our data showed that, among the five models, the deciduous broad-leaved forest had the highest soil quality index (0.618), followed by the mixed forest (0.593). Stepwise regression analysis showed that soil organic carbon explained 79.9% of the variations in the soil quality indices, suggesting it was a major factor affecting the soil quality. Thus, vegetation restoration models mainly comprised of native tree species effectively improved the soil quality in Karst rocky desertification areas, with deciduous broad-leaved forests displaying the best effects, followed by mixed forests.

 Coptishuanjiangensis, a new species of Ranunculaceae from Guangxi, China.

Coptishuanjiangensis, a new species of Ranunculaceae distributed in the valleys of Jiuwanshan National Natural Reserve in Huanjiang county (Guangxi, China), is described and illustrated for the first time based on morphological and plastome sequences data. It differs from C.chinensis, C.deltoidei and C.omeiensis mainly by having notably longer petiole, scape, bigger leaf blade with lobes obviously remote and robust rhizomes without stolons. Phylogenetic analyses support that C.huanjiangensis is sister to C.omeiensis and C.deltoidei.

Three new species of the subterranean genus Guiodytes from Guangxi, China (Coleoptera: Carabidae: Clivinini)

Three new species of the genus Guiodytes Tian, 2013 are described from the limestone caves of Guangxi Zhuang Autonomous Region, southern China: Guiodytes weii Huang & Faille sp. nov. and Guiodytes yueliangensis Huang & Tian sp. nov. from Dapo Dong and Huang Dong caves, respectively, in Huanjiang County, northernmost Guangxi; Guiodytes inexpectatus Tian & Zhou sp. nov. from the Zhuzhu Dong cave in Longzhou County, southwestern Guangxi. All of the six known species of Guiodytes are endemic to Guangxi, ranging from the southwest to the northernmost. A modified key to species and a distribution map for Guiodytes are provided.

The Variation in the Stoichiometric Characteristics of the Leaves and Roots of Karst Shrubs

Currently, vegetation restoration is being implemented in the ecologically fragile karst areas in southwest China; however, the stoichiometry of the dominant shrubs and their relationship with the environmental factors in the degraded habitats is still unclear. In this study, we investigated the stoichiometry of C, N, and P, their internal correlations, and influencing factors in 23 shrub species in the Huanjiang County in northwest Guangxi Province, China. We found that the mean contents of C, N and P in leaves were higher than those in roots. In addition, the N:P ratio in the leaves was significantly higher than that in the roots, but the opposite was observed for the C:N and C:P ratios. Except for Leaf C and Root C, significant positive or negative correlations were observed across the stoichiometry of the shrub leaves and roots. A factor analysis of variance demonstrated that the differences across species had higher explanatory power than the topography and soil nutrients in terms of the shrub leaf and root stoichiometry. Hence, our results can improve the understanding of the distribution patterns of these vital elements, as well as of the interactions and influencing factors in the different organs of the karst shrubs.

Rural–Urban Migration and Conservation Drive the Ecosystem Services Improvement in China Karst: A Case Study of HuanJiang County, Guangxi

Under the transformation from over-cultivation to ecological protection in China’s karst, how human activities affect ecosystem services should be studied. This study combined satellite imagery and ecosystem models (Carnegie-Ames-Stanford Approach (CASA), Revised Universal Soil Loss Equation (RUSLE) and Integrated Valuation of Ecosystem Services and Trade-offs (InVEST)) to evaluate primary ecosystem services (net ecosystem productivity (NEP), soil conservation and water yield) in a typical karst region (Huanjiang County). The relationships between human activities and ecosystem services were also examined. NEP increased from 441.7 g C/m2/yr in 2005 to 582.19 g C/m2/yr in 2015. Soil conservation also increased from 4.7 ton/ha to 5.5 ton/ha. Vegetation recovery and the conversion of farmland to forest, driven largely by restoration programs, contributed to this change. A positive relationship between increases in NEP, soil conservation and rural-urban migration (r = 0.62 and 0.53, P < 0.01, respectively) indicated decreasing human dependence on land reclamation and naturally regenerated vegetation. However, declining water yield from 784.3 to 724.5 mm highlights the trade-off between carbon sequestration and water yield should be considered. Our study suggests that conservation is critical to vegetation recovery in this region and that easing human pressure on land will play an important role.

Effect of Land Use and Land Cover Change on the Changes in Net Primary Productivity in Karst Areas of Southwest China: A Case Study of Huanjiang Maonan Autonomous County

Karst areas in southwest China have experienced significant land cover and land use change (LUCC) due to utilization for human activity and a comprehensive rocky desertification control project (RDCP) since 2008. It is important to quantify the effect of LUCC on ecosystem productivity in this region for assessing the overall benefit of this ecological restoration project. In this study, we used using MODIS land cover and NPP products to investigate the relative contribution of LUCC to the change in net primary productivity (NPP) during 2008–2013 in Huanjiang County, one of first one hundred pilot counties to implement RDCP. Our results show that NPP increased in 95.53% of the county, and the average growth of NPP in non-rocky desertification area was higher than in rocky desertification or potential rocky desertification areas. LUCC has an important contribution (25.23%) to the NPP increase in the county, especially in the LUCC area (70.97%), which increased the average NPP by 3.9% and 10.5%, respectively. Across the six RDCP regions in the county, the average increase in NPP for the vegetation restoration measure of governed karst area is significantly greater than in the ungoverned karst area, and the positive change in NPP increased with the increasing implementation area of the vegetation restoration measure.

Understanding the Rural Livelihood Stability System: The Eco-Migration in Huanjiang County, China

Immigrants are a special group whose livelihood stability is crucial to local sustainable development. To understand the positive effect of eco-migration policy on the immigrants, we innovatively selected the perspective of stability and quantified immigrants’ livelihood stability with relevant concepts, including livelihood capitals and strategies, response capacity, and land-use efficiency, which helped identify the problems and put forward suggestions to enhance livelihood sustainability, achieve better social integration, and promote the sustainable development of the rural resettlement areas. Huanjiang County was used as a study case as it is the largest and most representative eco-migrant resettlement county of the southwestern karst region, China. Aided by participatory rural appraisal (PRA), this paper explores the livelihood stability of immigrants and takes natives as the reference group. The results show that the livelihood stability values of immigrants were less than that of natives, but the gap was smaller than ten years ago; the natural, social, and other capitals owned by immigrants were almost the same as those of natives, demonstrating that the Chinese government’s poverty alleviation policies have benefitted immigrants. However, both immigrants and natives were found to have less natural and social capitals; high income dependency and an unbalanced proportion of income sources in addition to low land-use efficiency. Therefore, there are several suggestions put forward to achieve stable livelihood and rural sustainable development, and these items should be given increased consideration by both the government and households in resettlement areas.

Three new species of the aphaenopsian trechine genus Pilosaphaenops Deuve & Tian, 2008 from South China Karst (Coleoptera: Carabidae: Trechinae)

Summary Three new trechine species of the genus Pilosaphaenops Deuve & Tian, 2008, P. qianzhii n. sp. from cave Lubian Dong in Pingtang County, southern Guizhou Province, P. mengzhenae n. sp. and P. weiguofui n. sp. from cave Xia Dong in Nandan County, and cave Shenlong Gong in Huanjiang County respectively, northern Guangxi Zhuang Autonomous Region, are described and illustrated. A key to all known species of this genus is also provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:170C467F-5421-49AD-B1B1-091D8BD58B88

Land Functions, Rural Space Governance, and Farmers’ Environmental Perceptions: A Case Study from the Huanjiang Karst Mountain Area, China

Residents of rural areas live and depend on the land; hence, rural land plays a central role in the human–land relationship. The environment has the greatest direct impact on farmers’ lives and productivity. In recent years, the Chinese government carried out vigorous rural construction under a socialist framework and implemented a rural revitalization strategy. This study was performed in a rural area of Huanjiang County, Guangxi Province, China. We designed a survey to measure rural households’ perceptions of three types of rural spaces: ecological, living, and production spaces. The survey was administered to 379 farmers, and their perceptions and satisfaction with Ecological–Living–Productive spaces were evaluated with the use of structural equation modeling. Analysis of latent and observed variables indicates that: (1) Farmers’ overall satisfaction with Ecological–Living–Productive spaces was moderate. The average satisfaction score for production spaces was lowest (2.881) while that for living spaces was highest (3.468) and that for ecological spaces was in between (3.351). (2) The three most important exogenous observed variables associated with living space satisfaction were house comfort > domestic water supply > domestic sewage treatment. The three most important exogenous observed variables associated with production space satisfaction were irrigation water > cultivated land quantity > cultivated land fertility. The three most important exogenous observed variables associated with ecological space satisfaction were garbage disposal > vegetation cover > flood and waterlogging. Based on the requirements of the rural revitalization strategy and the results of our analyses of rural households’ spatial perceptions, we propose corresponding countermeasures and suggestions.

Emergy-based sustainability assessment of forest ecosystem with the aid of mountain eco-hydrological model in Huanjiang County, China

Abstract Comprehensive recognition and evaluation of ecosystem development are fundamental for sustainable decision-making and nature conservation. Using Huanjiang Maonan Autonomous (also named Huanjiang) County-a typical karst mountainous region as example, by coupling the emergy analysis and the mountain eco-hydrological model (MECH), the most suitable vegetation coverages for forest ecosystem sustainable development are obtained in different economic development levels. The results showed that the emergy of renewable resources (R), non-renewable resources (N) and economic feedback input (EFI) accounted for about 69.8%, 12.7%, and 17.5% of the total emergy (U) respectively from 2000 to 2015. Even though the forest ecosystem of Huanjiang maintained sustainable developing tendency; the decrease of the ratio of renewable resources emergy (R) to total emergy (U) resulted in the decrease of emergy self-support ratio (ESR), emergy yield ratio (EYR) and emergy sustainability index (ESI), which may threaten the system sustainability. The increase of vegetation coverage reduced soil loss and total runoff, increased economic feedback input. As the results, the renewability (R/U) and emergy investment ratio (EIR) presented an increase trend, while the emergy self-support ratio (ESR), emergy yield ratio (EYR) and environment loading ratio (ELR) showed a tendency of decrease. The system sustainability will reach the optimal state when the vegetation coverage increased by 30%, 20%, and 10% if the GDP value of the county in the future as those in the 10th, 11th, and 12th Five-year Plan in China . Coupling the emergy analysis and mountain eco-hydrological model provides a new approach to understand the harmonious development between forest ecosystem and human beings.

Quantitative analysis of the factors influencing spatial distribution of soil heavy metals based on geographical detector

With the rapid development of modern industry, heavy metals in the soil introduce the risk of serious pollution. To reduce this pollution risk, the following four research questions needed to be addressed: What are the main influencing factors of soil pollution? What is the degree of influence? Do factors operate independently or are they interconnected? Which regions have high pollution risk and should be paid more attention? The study area was in Huanjiang County, with 273 km2, and geographical detector proved to be a useful tool to solve these four problems. We found that mine activity and pH value were the primary influencing factors for total and water-soluble heavy metals. The interaction effects of mine activity and soil type, pH values, and normalized difference vegetation index (NDVI) for total heavy metals, as well as pH value and mine activity for water-soluble heavy metals, were greater than the sum effect of two factors. Zones with a high concentration of heavy metals were closer to the road and farther from the mine area, which had low NDVI, large slope, high terrain, and large pH values. Concentrations of total heavy metals were higher in calcareous soils and in dryland and forests. Zones with a higher concentration of water-soluble heavy metals were closer to the mine and river, which had lower DEM and pH values. The uncertainty of geographical detector was also analyzed on the basis of their interpolation accuracy and the stratification number of influencing factors, and we found that the existing sample numbers and the stratification number of influencing factors met the needs of geographical detector calculation. This study's conclusions are useful for soil pollution control and restoration.

Did the ecological engineering have a great impact on the land use change?

Overuse of land resources has increasingly contributed to environmental crises in China. To mitigate widespread land degradation, actions have been taken to maintain and restore the ecological environment through efforts such as ecological engineering. By analyzing trends in land use, the impact and effectiveness of ecological engineering can be determined. In this study, such changes in Huanjiang County in China were considered. In the early 1990s, an eco-immigration policy and "returning farmland to forest program" were implemented in the county, drastically impacting land use. Land use/land cover changes were detected and analyzed using remote sensing data recorded over 4years (1995, 2000, 2005, and 2010). Land transfer flow and the rate of land use change elucidated the extent of changes, while nuclear density analysis indicated spatial agglomeration. The results indicate that, over a period of 15years, farmland area increased, while forest area decreased initially before subsequently increasing. From 1995 to 2000, the highest transfer flow was observed in the grassland to farmland conversion (79.34%). From 2000 to 2005, the transfer flow of conversions was the highest for forest to farmland (56.79%). Land use changes were not prominent from 2005 to 2010. Direct drivers of land use change exert obvious impacts on land use, and indirect drivers impact direct drivers that are then channeled through direct anthropogenic drivers (e.g., land use policies). We found that ecological engineering has a very significant impact on land use change, and that impact varies from region to region.

Accumulation of Cd and Its Risks in the Soils of the Xijiang River Drainage Basin in Guangxi

To understand the distribution and risk of soil cadmium (Cd) in the Xijiang River drainage basin in Guangxi, a total of 2512 soil samples were collected nonferrous metal mining area, farmland (paddy soils and dryland soils) and the background soils, in the Xijiang River drainage basin in Guangxi.The results showed that Cd concentration was 0.514 mg·kg-1 in background soils significantly higher than previously resulted(0.148 mg·kg-1)and that in Guangxi background soil(0.267 mg·kg-1). The geometric average concentration of Cd in dryland soils, paddysoils and mining soils was 0.559, 0.787, 5.71 mg·kg-1, respectively, which were significantly higher than background soils. The Cd concentration exceeded the background soils and baseline by 51.2% and 35.2% in dryland soil, 66.7% and 39.6% in paddy soil, 77.8% and 71.4% in mining soil, high Cd concentration occurred in the Nandan County, Dahua County, Duan County, Huanjiang County and Yizhou City, as well as Liujiang County, These regions have developed severe and even extremely serious pollution, medium-high pollution accumulation and higher-extremely high potential ecological risks. The Cd-pollution in soils in agricultural and mining soils in upstream of Xijiang River in Guangxi is serious, due to mining activities and high Cd geological background. People in the mining area and surrounding areas who live on local crops, vegetables, may expose to the Cd-pollution. It is recommended to further develop a Cd risk assessment through a soil-plant-human system, taking appropriate measures to control risk.

Environmental impact assessment of ecological migration in China: a survey of immigrant resettlement regions

Implementation of ecological migration (eco-migration) policies may improve the fragile ecological environment of emigration areas; however, it also places enormous pressure on the human-environment systems in immigrant resettlement regions. Via the application of participatory rural appraisal (PRA) methods, ecological footprint (EF), and stochastic impacts by regression on population, affluence, and technology (STIRPAT) models, 21 villages of Huanjiang County in Guangxi Zhuang Autonomous Region, China were used in this research as a case study area for the environmental appraisal of eco-migration policies in immigrant resettlement regions. Results show: (1) In the past 20 years of implementing eco-migration policies, the EF per capita constantly increased, the biocapacity (BC) per capita constantly decreased, and the ecological deficit gradually increased, indicating an extremely negative impact of eco-migration projects on the ecological environment in the immigration areas. (2) Cropland and forest land are the most important components of the per-capita EF. The per-capita EF of cropland experienced overall a first increasing and then decreasing trend, and the per-capita EF of forest land constantly increased and showed the most rapid increase among all types of EF in the last two decades. (3) The proportion of per-capita EF of different types of productive land is in the order of forest land > cropland > carbon uptake land > built-up land > grazing land from high to low, and this is a significant change from the original order of cropland > forest land > carbon uptake land > grazing land > built-up land. (4) Because of unequal possession of ecologically productive resources, the overall per-capita EF, overall per-capita BC, overall per-capita ecological deficit of productive land use by migrants, and their component values of different types of productive land use are all lower than the corresponding values of the natives. The ecological deficit of natives is more severe than that of migrants. (5) Whereas population growth and overexploitation of resources lead directly to the increased pressure on the ecological environment in the immigration areas, increasing nonagricultural income and improving the consumption structure can reduce the dependence of farmers on the land, thus inhibiting the increase of EF.

Quantitative Analysis of the Factors Influencing Soil Heavy Metal Lateral Migration in Rainfalls Based on Geographical Detector Software: A Case Study in Huanjiang County, China

Quantitative analysis of the factors influencing heavy metal migration could be useful for controlling heavy metal migration. In this paper, a geographical detector was used to calculate the contributions of and interactions among factors in Huanjiang County, South China, covering an area of 273 km2. In this paper, nine factors were analyzed. The results showed that, among these factors, soil type was the main factor influencing the migration of As, Pb and Cd; the other eight factors did not have big differences and were lower than soil type. In addition, there were obvious synergistic effects between the soil type and concentration of water-soluble heavy metals (CWS) and the concentration of water-insoluble heavy metals (CWI) and NDVI. Therefore, these factors of the study area were especially focused on. Furthermore, the results of the key factor identification and the high-risk region identification in the nine factors were reliable, based on the geographical detector software. Therefore, the geographical detector software could be used as an effective tool to quantitatively analyze the contribution of the factors, and identify the high-risk regions for the factors influencing soil heavy metal lateral migration in rainfalls.

A review of the aphaenopsian ground beetle genus Uenotrechus Deuve et Tian, 1999 (Coleoptera: Carabidae: Trechinae)

Uenotrechus Deuve et Tian, 1999, one of the highly cave-adapted genera of the ground beetles, is reviewed. New record of the type species U. liboensis Deuve et Tian, 1999 and descriptions and illustrations of two remarkable new species are provided: Uenotrechus gejianbangi Tian et Wei, sp. n. (type locality: Cave Ji Dong, Neiwen Tun, Huanjiang County, northernmost Guangxi), Uenotrechus deuvei Tian et Chen, sp. n. (type locality: Cave Longmu Dong I, Du’an County, northern Guangxi). U. nandanensis bona sp. is proposed as an independent species. A distribution map and a key to all species of Uenotrechus are also given.

Migration and Accumulation of Cadmium in Paddy Soil

Soil samples were collected from a paddy field at Fulong village, Huanjiang County, and Cd concentrations in soils were determined. Soil Cd risk was evaluated using Nemerow index method. The results showed that the content of cadmium in soil layer of 0~20cm is 2 times than the level two standard values and 6 times than the background value of Huanjiang soil. In addition, the soil layer of 20~100cm in cadmium content did not exceed the national level two standard values, but is about 2 times the background value of soil in Huanjiang county. In addition, Cadmium pollution is mainly focused on the soil surface.

New records and a new species of the cavernicolous genus Guiodytes Tian, 2013 from Guangxi, China (Coleoptera: Carabidae: Scaritinae).

A new species of the genus Guiodytes Tian, 2013 is described from a limestone cave called Shuiku Dong in Huanjiang County of northernmost Guangxi, southern China. G. deharvengi n. sp. is the first depigmented species of Guiodytes. It is close to G. cavicola Tian, 2013, but easily recognized by its broader and yellowish brown body. In addition, new records for G. cavicola Tian, 2013 are provided from two caves in Du'an County of northern Guangxi, with description of the male genitalia. A key to all three known species and a distributional map of Guiodytes are also given.

A New Species ofGoniurosaurus(Squamata: Eublepharidae) from Libo, Guizhou Province, China

A new species of the genus Goniurosaurus is described from Libo County, Guizhou Province and Huanjiang County, Guangxi, China. Goniurosaurus liboensis sp. n. can be discriminated from other known congeners by its medium size, with adults measuring 103.2-110.3 mm snout-vent length; 23 precloacal pores in males; a posteriorly protracted nuchal loop six or seven scale rows in width; two or three internasals, eight or nine nasal scales surrounding nares; a greatly enlarged row of supraorbital tubercles; the granular scales of upper eyelids nearly equal in size as those on the top of head; deep axillary pockets; claws sheathed by four scales; chin, throat, thorax, and ventral surfaces of body and limbs white, immaculate; and three thin immaculate dorsal body bands between limb insertions. Natural history data and an expanded key to the genus Goniurosaurus are provided.

A new blind loach, Oreonectes elongatus sp. nov. (Cypriniformes: Balitoridae) from Guangxi, China

A new loach, Oreonectes elongatus sp. nov. is described based on collections from Mulun Township, Huanjiang County, Guangxi in China. It is distinguished from its congeners by the combination of the following characters: most elongate body (body depth/SL 8.62–10.68%), blind, a forked caudal fin, obvious adipose dorsal crest and ventral crest; entire body naked and de-pigmented. Although the new species has a similar distribution with O. macrolepis, it can be distinguished by scales (absent in O. elongatus vs. present in O. macrolepis), shape of snout (elongate vs. round), the opposite position of the dorsal and pelvic fins origins (behind vs. front). The new species shares the same possession of dorsal and ventral crests, a forked caudal fin, eyeless, naked body and incomplete lateral line with O. translucens, but can be distinguished from the latter by caudal fin crest (more developed and translucent in O. translucens), longer anterior nostril tube and barbel, extreme of pectoral fin reaching 2/3 of the distance between origin of pectoral and pelvic fins, more vertebrae (4 + 38–39 vs. 4 + 32).