Degree Of Desertification Research Articles

Early-Warning System for Desertification Based on Climatic and Hydrologic Criteria

The United Nations’ convention on desertification encourages the participating countries to introduce criteria for developing Early-Warning Systems (EWS) in order to monitor and assess desertification. The objective of the present study was to establish an EWS for desertification assessment in Kashan plain, Iran, using the methodology of practical and general applicability. Designing EWS requires a model to identify the influential criteria and areas vulnerable to desertification. The Kashan Plain’s EWS relies on the Iranian Model for Desertification Potential Assessment (IMDPA) to establish desertification thresholds and generate desertification maps with Geographic Information Systems (GIS). The EWS of Kashan plain was designed to calculate hydrologic (groundwater level and electric conductivity of groundwater indices) and climatic (precipitation, Transeau aridity, and drought indices) criteria and assess the degree of regional desertification. Afterwards, the desertification intensity maps of criteria and indices were produced and overlapped. The EWS was developed in areas most bound to be threatened by desertification. EWS quantifies desertification data and thresholds to issue desertification assessments and warnings for management purposes. In the next step, Client–Server program was designed based on an algorithm defined by Java programming language and implemented as a data collection, analysis, and response management system. Whenever the thresholds exceed the defined limits, warning messages can be sent via SMS or internet to relevant system managers for appropriate action.

Analysis of the desertification dynamics of sandy lands in Northern China over the period 2000–2017

It is of great practical significance to thoroughly study the environmental changes and conduct desertification assessments of sandy lands to elucidate the formation and recovery mechanism of desertification. The purpose of this study is to evaluate the desertification process and its driving factors accurately and objectively, and compare the differences of desertification process in different areas. We used Moderate Resolution Imaging Spectroradiometer (MODIS) surface albedo (MCD43A3) and leaf area index (LAI) (MCD15A2H) products to calculate the desertification divided index (DDI) to reveal the spatial-temporal variation regularity of the four sandy lands in northern China during 2000–2017 as well as the correlation between desertification and precipitation. The results showed that the total desertification degree of sandy lands in northern China showed a downward trend during the study period. By grading the desertification level, it was found the decline trend of severe desertification and high desertification was relatively significant (p < 0.05). The spatial trend of the desertification level in sandy lands was significantly different, and the decreased area of severe desertification and high desertification in Mu Us sandy land was the largest (−0.042 × 104 km2 yr−1 and −0.052 × 104 km2 yr−1), while the interannual variation of the various desertification levels in Hulun Buir sandy land was small (±0.003 × 104 km2 yr−1). The precipitation and DDI were positively correlated in most areas (p < 0.05). Especially in Mu Us sandy land and Hunshandake sandy land, the proportional area of positive correlation between the precipitation and DDI was more prominent, accounting for 72.9% and 63.7%, respectively. This study had important decision-making significance for the effective management of sandy lands in arid/semiarid areas.

Potential biodiversity map of darkling beetles (Tenebrionidae): environmental characterization, land-uses and analyses of protection areas in Southern Patagonia

Different methodologies had been developed for species management and conservation based on modelling of potential biodiversity at regional scales. However, most of these models were fitted for umbrella species (e.g. big mammals) rather than micro-fauna. Beetles should be included to improve conservation strategies due to their functional roles and vulnerability in arid environments. The maps of potential biodiversity (MPB) based on different potential habitat suitability (PHS) maps are useful to indicate high biodiversity areas. Firstly, we aim to elaborate a MPB of darkling beetles (Coleoptera: Tenebrionidae) based on 10 species PHS maps inhabiting Santa Cruz Province (Argentina). Then, we analysed the MPB an environmental gradients and land-use variables. We explored 41 potential variables to develop PHS maps. The MPB was included into a GIS project, and was analysed considering climatic and topographic variables, ecological areas and soil organic carbon (SOC) stock, also sheep density, desertification and protected area network. The modelled showed great variability in their habitat requirements (e.g. temperature), where marginality (PHS differs from the available conditions) and specialization (environmental condition range of PHS) determined three species groups. MPB increased from grasslands in the NE to shrublands in the SE, and was higher with SOC, sheep density and desertification degree. Protection areas included lower MPB for darkling beetles, where provincial reserves have a major conservation role compared with national parks. MPB allowed us to understand the potential trade-offs with the environment and human uses. This gave us a tool to development new strategies (e.g. land-sparing) for management and conservation.

Fractal features of sandy soil particle-size distributions during the rangeland desertification process on the eastern Qinghai-Tibet Plateau

Fractal theory has been frequently applied to quantify soil particle-size distributions (PSDs) and evaluate soil degradation. Eolian desertification occurring on the eastern Qinghai-Tibet Plateau is threatening the ecological environment. It is essential to investigate the desertification process by adopting the concept of space as a substitute for time. Here, the fractal features of soil PSDs and their relationships with selected soil properties and wind erosion and deposition were studied. The tested soil samples were collected from rangelands with four different degrees of desertification (light, medium, severe, and extremely severe). Soil particle sizes were measured by a laser diffraction particle-size analyzer. Soil moisture and soil bulk density were determined by the soil weight difference before and after oven-drying for 8 h. Soil organic carbon was determined by the K2Cr2O7-H2SO4 oxidation method and soil total nitrogen was analyzed using the Kjeldahl digestion procedure. Wind tunnel experiments were conducted to simulate wind erosion and deposition during the desertification process. Values of the fractal dimension of soil PSDs were calculated using the volume-based fractal model. ANOVA with an LSD test and Pearson correlation analysis were used to analyze whether different parameters used in the fractal model influenced the results of the fractal dimensions and were reasonable to be applied. Different parameters, including the arithmetic mean size and the upper sieve size of two successive sieve sizes, values of Rmin, and the number of data points used in the fractal model, rarely influenced the results of the fractal dimensions (p > 0.05). The D values showed a significantly positive correlation with the clay and silt contents and a strong negative correlation with the sand contents. Along the degrees of desertification from light to extremely severe, the contents of clay, silt, and very fine sand decreased while the fine sand contents increased, and the D values decreased accordingly. Rangelands with heavier desertification and lower D values were more easily exposed to wind erosion, relating to the further loss of soil organic carbon, soil total nitrogen, and soil moisture and increased soil bulk density. The soil depth could affect soil PSDs and the selected soil properties of rangelands under light and medium degrees of desertification but rarely influenced those of severely and extremely severely desertified lands. Different parameters, including the arithmetic mean size, the upper sieve size, values of Rmin, and the number of data points used in the fractal model, had no impacts on the results of the fractal dimensions, and were reasonable to be applied. We suggest the fractal dimension as an effective indicator to evaluate soil environment changes induced by desertification.

Impact of desertification on soil and plant nutrient stoichiometry in a desert grassland

Grassland degradation resulting from desertification often alters the carbon (C), nitrogen (N) and phosphorus (P) cycles within grassland ecosystems. To estimate the effects of desertification on the C, N, and P concentrations and C:N:P stoichiometry of plants and soil, we examined C, N, and P concentrations in plant tissues (leaves, roots and litter) and soil across five degrees of desertification in the desert grassland of Ningxia, China (control, light, moderate, severe and very severe desertification stages). The C, N, and P concentrations and C:N:P stoichiometry of the leaves, roots and litter differed among the different desertification stages. Desertification resulted in opposing trends between the leaf N concentration and leaf C:N ratio. With the exception of the very severe desertification stage, the leaf N:P ratio decreased over the process of grassland desertification. The soil C, N, and P concentrations and soil N:P and C:P ratios decreased significantly along the grassland desertification gradient. In contrast, the soil C:N ratio remained relatively stable during desertification (10.85 to 11.48). The results indicate that desertification is unfavourable to C and N fixation and has a negative effect on the ecosystem structure and function of desert grassland.

Influences of 1.5 °C and 2.0 °C global warming scenarios on water use efficiency dynamics in the sandy areas of northern China

Water use efficiency (WUE) is an important variable used in hydrometeorology study to reveal the links between carbon-water cycles in sandy ecosystems which are highly sensitive to climate change and can readily reflect the effects of it. In light of the Paris Agreement, it is essential to identify the regional impacts of 0.5 °C of additional global warming to inform climate adaptation and mitigation strategies. Using the modified Carnegie-Ames-Stanford Approach (CASA) and Advection-Aridity (AA) models with global warming values of 1.5 °C and 2.0 °C above preindustrial levels from Inter-Sectoral Impact Model Intercomparison Project (ISIMIP2b) datasets, we conducted a new set of climate simulations to assess the effects of climate on WUE (the ratio of net primary productivity (NPP) to actual evapotranspiration (ETa)) in different sandy land types (mobile sandy land, MSL; semimobile/semifixed sandy land, SMSF; and fixed sandy land, FSL) during the period of baseline (1986–2005) and future (2006–2100). The spatiotemporal patterns of ETa, NPP, and WUE mostly showed increasing trends; the value of WUE decreased (6.40%) only in MSL with an additional 0.5 °C of warming. Meteorological and vegetation factors determined the variations in WUE. With warming, only the correlation between precipitation and WUE decreased in the three sandy land types, and the leaf area index (LAI) increased with an additional 0.5 °C of warming. The desertification degree comprehensively reflects the linkages among the standardized precipitation evapotranspiration index (SPEI), LAI and WUE. Simulation results indicated the sandy area extent could potential increase by 20 × 104 km2 per decade on average during 2016–2047 and that the increase could be gradual (2.60 × 104 km2 per decade) after 2050 (2050–2100). These results highlight the benefits of limiting the global mean temperature change to 1.5 °C above preindustrial levels and can help identify the risk of desertification with an additional 0.5 °C of warming.

Aeolian Material Migration in Transbaikalia (Asian Russia)

We revealed regional features of functioning of a large Transbaikalian aeolian morphodynamic system. Natural pre-conditions, current realities and factors of development of aeolian processes are investigated. The paper considers regularities of spatial distribution of deflation, transit, and aeolian accumulation zones. Main directions of aeolian migration of matter are determined. Pulsating nature of aeolian processes development in Holocene has been established. Identified are intrasecular cycles and Holocene dynamics of aeolian processes. We identified intrasecular (11, 27–35 years old), secular (80 year old) and Holocene (500, 2000 year old) cycles of aeolian process dynamics. The paper shows the influence of anthropogenic activity on the activation of aeolian migration of material for the historical period. It presents an overview of extreme aeolian events. Regionalization of Transbaikalia was carried out according to the degree of probable desertification of the territory due to development of aeolian processes. Areas of catastrophic manifestation of processes are highlighted. The results of long-term experimental observations of deflation and aeolian accumulation are presented. Particular attention is paid to the characteristics of the aeolian corridors. The important role of aeolian processes in the intensive material transport from Transbaikalia to the south and southeast to neighboring regions of Mongolia and China is shown.

鄱阳湖沙地蔓荆灌丛沙堆形态特征及空间分布格局

PDF HTML阅读 XML下载 导出引用 引用提醒 鄱阳湖沙地蔓荆灌丛沙堆形态特征及空间分布格局 DOI: 10.5846/stxb201809151998 作者: 作者单位: 南昌工程学院 水利与生态工程学院,南昌工程学院 水利与生态工程学院,南昌工程学院 水利与生态工程学院,南昌工程学院 水利与生态工程学院,南昌工程学院 水利与生态工程学院,南昌工程学院 水利与生态工程学院,南昌工程学院 水利与生态工程学院 作者简介: 通讯作者: 中图分类号: 基金项目: 水利部鄱阳湖水资源水生态环境研究开放基金（ZXKT201510）；国家自然科学基金项目（51669015）；南昌工程学院校级大学生科研训练项目（201508） Morphological characteristics and spatial distribution patterns of Vitex trifolia nebkhas in the Poyang Lake sand land Author: Affiliation: College of Water and Ecology Engineering,Nanchang Institute of Technology,College of Water and Ecology Engineering,Nanchang Institute of Technology,College of Water and Ecology Engineering,Nanchang Institute of Technology,College of Water and Ecology Engineering,Nanchang Institute of Technology,College of Water and Ecology Engineering,Nanchang Institute of Technology,College of Water and Ecology Engineering,Nanchang Institute of Technology,College of Water and Ecology Engineering,Nanchang Institute of Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:目前灌丛沙堆研究主要集中在干旱半干旱区的沙质草原和沙漠边缘，对亚热带湿润区灌丛沙堆的形成、演变过程并不清楚。以鄱阳湖沙地为研究区，通过样方调查和地统计学的方法，研究不同沙化程度下蔓荆灌丛沙堆的形态特征及分布格局。结果表明：鄱阳湖沙地蔓荆沙堆的形态以盾形为主，其冠幅变化幅度为1.2-18.2 m2，固定和半固定沙地显著高于流动沙地；对灌丛沙堆的形态参数来说，其长轴与短轴在固定和半固定沙地上呈极显著的线性相关关系，流动沙地上呈二次函数关系；半固定和流动沙地上沙堆底面积与沙堆高度呈二次函数关系（r>0.6）；3种类型沙地上灌丛底面积与沙堆体积之间极显著线性相关，其中半固定沙地线性函数的斜率最大；除固定沙地的沙堆高度和半固定沙地的灌丛高度外，3种沙地上蔓荆灌丛与沙堆的其他形态参数间均极显著相关，说明随着沙地的固定，蔓荆灌丛有利于沙堆水平尺度的增长；3种沙地上蔓荆沙堆均呈随机分布。 Abstract:Studies of nebkhas focus mainly on the vegetation of sandy grasslands or desert edges in arid and semi-arid areas, whereas the formation and development processes of nebkhas in subtropical humid areas remains unknown. The goal of this study was to reveal the morphological characteristics and distribution patterns of Vitex trifolia nebkhas under different degrees of desertification in the sandy areas of Poyang Lake. The nebkhas pile of V. trifolia was primarily shield shaped, and the crown breadth ranged from 1.2 m2 to 18.2 m2, and the breadth in shifting sands was smaller than that in both fixed and semi-fixed sands. Relationships between the long axis and the short axis of nebkhas were linear in the fixed and semi-fixed sands, but showed a quadratic relationship in shifting sands. The projected areas of nebkhas in semi-fixed and shifting sands were quadratically related with their heights (r > 0.6). For all types of sands, there was a an extremely significant linear correlation between the projected area of thickets and the volume of nebkhas, the slope of which was highest in semi-fixed sands. Except for the height of nebkhas in fixed sand and the thicket height in semi-fixed shrubs, there were significant correlations between the morphological parameters of the thickets and nebkhas in the three types of sands. The results showed that with sandy land being fixed, the shrub was advantageous to increases in the horizontal scale of V. trifolia nebkhas. V. trifolia nebkhas was randomly distributed on sandy lands. 参考文献 相似文献 引证文献

Variation of δ13C in plant-soil-cave systems in karst regions with different degrees of rocky desertification in southwest China

Variation of δ13C in plant-soil-cave systems in karst regions with different degrees of rocky desertification in southwest China

Quantitative Assessment of Desertification in an Arid Oasis Using Remote Sensing Data and Spectral Index Techniques

Desertification is an environmental problem worldwide. Remote sensing data and technique offer substantial information for mapping and assessment of desertification. Desertification is one of the most serious forms of environmental threat in Morocco, especially in the oases in the south-eastern part of the country. This study aims to map the degree of desertification in middle Draa Valley in 2017 using a Sentinel-2 MSI (multispectral instrument) image. Firstly, three indices, namely, tasselled cap brightness (TCB), greenness (TCG) and wetness (TCW) were extracted using the tasselled cap transformation method. Secondly, other indices, such as normalized difference vegetation index (NDVI) and albedo, were retrieved. Thirdly, a linear regression analysis was performed on NDVI–albedo, TCG–TCB and TCW–TCB combinations. Results showed a higher correlation between TCW and TCB (r = −0.812) than with that of the NDVI–albedo (r = −0.50). On the basis of this analysis, a desertification degree index was developed using the TCW–TCB feature space classification. A map of desertification grades was elaborated and divided into five classes, namely, nondesertification, low, moderate, severe and extreme levels. Results indicated that only 6.20% of the study area falls under the nondesertification grade, whereas 26.92% and 32.85% fall under the severe and extreme grades, respectively. The employed method was useful for the quantitative assessment of desertification with an overall accuracy of 93.07%. This method is simple, robust, powerful, and easy to use for the management and protection of the fragile arid and semiarid lands.

Total Runoff of Surface Waters in New Climatic Conditions on the Republic of Moldova’s Territory

Abstract Although it is considered that the socio-economic impact over the last decades on surface water quality is significant, the role of changing regional climate that is manifested by the intensification of desertification process is crucial. In this context, it is important to know the current trends of change in total runoff of surface of surface waters in the context of increase of desertification degree of the regional climate attested in recent years

石漠化程度对苔藓植物多样性及其结皮土壤化学性质的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 石漠化程度对苔藓植物多样性及其结皮土壤化学性质的影响 DOI: 10.5846/stxb201710181875 作者: 作者单位: 贵州师范大学贵州省山地环境信息系统与生态环境保护重点实验室,1.贵州师范大学贵州省山地环境信息系统与生态环境保护重点实验室 2.贵州省喀斯特山地生态环境国家重点实验室培育基地,贵州师范大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31160042，31760050，31760043）；贵州省国际科技合作项目（黔科合外G字2013-7016号） The effects of rocky desertification degree on bryophyte diversity and soil chemical properties of crusts Author: Affiliation: Key Laboratory forInformation System of Mountainous Area and Protection of Ecological Environment of Guizhou Province，Guizhou Normal University，,Key Laboratory forInformation System of Mountainous Area and Protection of Ecological Environment of Guizhou Province，Guizhou Normal University，, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以研究区域不同石漠化等级为代表，分析苔藓多样性特征及其结皮土壤化学性质变化规律，探索其对石漠化进程的响应机制。结果显示：（1）苔藓物种多样性：含苔藓14科29属84种，其中苔类2科2属2种；（2）多样性指数表现为：重度石漠化阶段 > 中度石漠化 > 轻度石漠化 > 极重度石漠化 > 无石漠化；其均匀度为：中度石漠化阶段 > 轻度石漠化 > 重度石漠化 > 极重度石漠化 > 无石漠化；（3）随着石漠化程度加剧，苔藓群落组成中混合群落比重下降而纯群落比重上升；群落生活型则呈现交织型递减而丛集型递增的规律。（4）结皮土壤中全氮、全磷和微生物量碳随石漠化加剧均都呈递减趋势。（5）通过Partial RDA分析发现密枝青藓（Brachythecium amnicolum）、褶叶藓（Palamocladium nilgheriense）和美灰藓（Eurohypnum leptothallum）等可用于石漠化生态修复。石漠化程度对苔藓多样性影响不显著，但对其群落特征和生活型影响显著。因此可以结合苔藓群落和生活型特征监测石漠化，同时也可使用苔藓作为先锋植物引进用于石漠化早期修复。 Abstract:Rocky desertification is one of the most serious economic and ecological problems encountered in the development of southwestern China. Understanding the characteristics of bryophyte diversity and soil chemical properties in different stages of rocky desertification, together with their response mechanisms to rocky desertification, is of vital importance in limiting further species loss and in the selection of species suitable for restoration and regeneration. Bryophyte species diversity, evenness, species richness, life forms, community characteristics and soil chemical properties were investigated in areas with differing levels of rocky desertification in Karst Park, Guiyang, Guizhou Province, China. Eighty-four bryophyte taxa from 29 genera and 14 families, were found in the study area; with the exception of 2 liverwort taxa from 2 genera and 2 families, all were mosses. The degree of rocky desertification in the study area was classified into five levels:nil-slight-moderate-severe -extreme. The order of species diversity of bryophytes in each of these categories was:severe (i.e. most species) > moderate > slight > extreme > nil (i.e. least number of species); the order of evenness index was determined as:moderate > slight > severe > extreme > nil. As the degree of rocky desertification increased, there was a corresponding decrease in the proportion of multi-species bryophyte communities and an increase in the proportion of single species communities. Wefts and turfs were the most commonly occurring life forms; with increasing rocky desertification, there was a corresponding increase in the proportion of turfs. Total nitrogen, total phosphorus, and microbial biomass carbon in the underlying soil, were markedly affected by rocky desertification, and decreased as the degree of rocky desertification increased. Partial redundancy analysis determined that three bryophyte taxa, Brachythecium amnicolum, Palamocladium nilgheriense, and Eurohypnum leptothallum, are suitable species for use in ecological restoration of areas affected by rocky desertification. The degree of rocky desertification did not significantly influence bryophyte diversity, but it did significantly affect community characteristics and life forms. Thus, monitoring changes in rocky desertification is possible by using characteristics of bryophyte communities and life forms. Suitable bryophytes can also be used as pioneer species for the restoration and recovery of areas of rocky desertification. 参考文献 相似文献 引证文献

Responses of soil physical and chemical properties to karst rocky desertification evolution in typical karst valley area

In order to reveal the differences of soil physical and chemical properties and their response mechanism to the evolution of KRD. The characteristics of soil physical and chemical properties of different grades of KRD were studied by field sampling method to research different types of KRD in the typical karst valley of southern China. Instead of using space of time, to explore the response and the mechanisms of the soil physical and chemical properties at the different evolution process. The results showed that: (1) There were significant differences in organic matter, pH, total nitrogen, total phosphorus, total potassium, sediment concentration, clay content and AWHC in different levels of KRD environment. However, these indicators are not with increasing desertification degree has been degraded, but improved after a first degradation trends; (2) The correlation analysis showed that soil organic matter, acid, alkali, total nitrogen, total phosphorus, total potassium and clay contents were significantly correlated with other physical and chemical factors. They are the key factors of soil physical and chemical properties, play a key role in improving soil physical and chemical properties and promoting nutrient cycling; (3) The principal component analysis showed that the cumulative contribution rate of organic matter, pH, total nitrogen, total phosphorus, total potassium and sediment concentration was 80.26%, which was the key index to evaluate rocky desertification degree based on soil physical and chemical properties. The results have important theoretical and practical significance for the protection and restoration of rocky desertification ecosystem in southwest China.

Potential biodiversity map of lizard species in Southern Patagonia: environmental characterization, desertification influence and analyses of protection areas

Abstract The distribution of biodiversity at the landscape level is shaped by biotic, abiotic and anthropogenic factors. Biodiversity maps provide the basis for defining management and conservation strategies that can minimize human impacts. The objective was to elaborate a map of potential biodiversity of lizards based on habitat suitability maps of individual species in Santa Cruz (Argentina). Also, we analysed desertification influence and the representativeness of the current network of protected areas on the lizard biodiversity. For this, we used a database of eight lizard species and we explored 41 potential explanatory variables to develop habitat suitability maps, which were combined to obtain one single map of the potential biodiversity. We analysed the outputs in a GIS project using the marginality and the specialization indexes and the normalized difference vegetation index of each species. Also, we characterized the potential biodiversity using the following variables: desertification, ecological areas and current network of protected areas. We detected differences in the occupied niches for the different species throughout the landscape. The map of potential biodiversity uncovered hotspots of biodiversity in the north-east study area, where the prevalence of unique climatic conditions showed a dry steppe and a high degree of desertification due to the human impacts (e.g. livestock). These results can be readily used as a support system for conservation and management strategies at different scale levels in areas with higher human impacts or to develop new protection areas.

Quantitative extraction of the bedrock exposure rate based on unmanned aerial vehicle data and Landsat-8 OLI image in a karst environment

In the karst regions of southwest China, rocky desertification is one of the most serious problems in land degradation. The bedrock exposure rate is an important index to assess the degree of rocky desertification in karst regions. Because of the inherent merits of macro-scale, frequency, efficiency, and synthesis, remote sensing is a promising method to monitor and assess karst rocky desertification on a large scale. However, actual measurement of the bedrock exposure rate is difficult and existing remote-sensing methods cannot directly be exploited to extract the bedrock exposure rate owing to the high complexity and heterogeneity of karst environments. Therefore, using unmanned aerial vehicle (UAV) and Landsat-8 Operational Land Imager (OLI) data for Xingren County, Guizhou Province, quantitative extraction of the bedrock exposure rate based on multi-scale remote-sensing data was developed. Firstly, we used an object-oriented method to carry out accurate classification of UAVimages. From the results of rock extraction, the bedrock exposure rate was calculated at the 30 m grid scale. Parts of the calculated samples were used as training data; other data were used for model validation. Secondly, in each grid the band reflectivity of Landsat-8 OLI data was extracted and a variety of rock and vegetation indexes (e.g., NDVI and SAVI) were calculated. Finally, a network model was established to extract the bedrock exposure rate. The correlation coefficient of the network model was 0.855, that of the validation model was 0.677 and the root mean square error of the validation model was 0.073. This method is valuable for wide-scale estimation of bedrock exposure rate in karst environments. Using the quantitative inversion model, a distribution map of the bedrock exposure rate in Xingren County was obtained.

The desertification process in the Silk Road Economic Belt in the past 15 years: A study using MODIS data and GIS analysis

The arid region in the northern part of China is a bridge between China and neighbouring countries in the Silk Road Economic Belt, and the severe desertification in this region restricts its sustainable development. In this paper, MODIS data, including albedo, reflectance, normalized vegetation index, and land surface temperature, were selected in 2000, 2005, 2010, and 2015 to construct a decision tree to extract spatio‐temporal information of the desertified land in the arid area. The trend in desertification and transfer directions was analysed by the GIS method, and the dynamic characteristics of the desertification at different units (provincial administrative unit and typical sandy land) and with different topographic factors (slope and aspect) are discussed. Our conclusions include (a) desertification in the arid region in the northern part of China showed improvement overall and local deterioration. The deteriorating areas were located primarily in the western region of the Hunshandake Sandy Land, the tectonic zone of the Taklimakan Desert, and the Qaidam Basin; (b) the degree of desertification transfer occurred primarily at adjacent levels; (c) the desertified area in each province showed a different trend in fluctuation, and Maowusu Sandy Land recovered better among the 4 large sands; and (d) the desertified area was distributed primarily along 0o–3o slopes and showed a rapid decline at increased slopes. The change in the degree of desertification in each aspect largely was a general reversal, and the area of the north aspect was larger than that of other areas of aspects. This study provides some theoretical support for the control of desertification in the Silk Road Economic Belt.

Assessment of desertification hazard, risk and development of management plans

About 80 percent of Iran is arid and semi-arid and about 35 percent of this area is susceptible to desertification hazard. Therefore desertification assessment and identification of the most important criteria for the assessment of risk and a basis for development of management plans is essential. This research was conducted in the semi-arid region of Agh-Band in the Golestan province, Iran with an area of 3062.5 km2 aiming at preparation of the desertification hazard and risk maps and development of various management plans to control the desertification. In this study, the IMDPA model and geomorphologic facies were used to evaluate the desertification hazard. The work units (geomorphologic facies) were defined based on geology and land use maps, satellite images and field surveys. The risk map was developed with a combination of desertification hazard intensity and hazard elements [A1] [A2] and degree of vulnerability maps using the total risk equation. Desertification management plan was developed based on four management strategies including: no plan, maintains the status quo, avoid the risk and implement the control measures. The results indicated that soil and vegetation criteria with magnitudes of 2.67 and 2.54 fall into sever desertification category (III) and other criteria are within medium class (II). The average value of degree of desertification in the study area was 2.03 (class II).

典型喀斯特石漠化生态系统土壤有机碳时空分布格局及其与环境的相关性

PDF HTML阅读 XML下载 导出引用 引用提醒 典型喀斯特石漠化生态系统土壤有机碳时空分布格局及其与环境的相关性 DOI: 10.5846/stxb201510152081 作者: 作者单位: 贵州师范大学喀斯特研究院,贵州师范大学喀斯特研究院,贵州师范大学喀斯特研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 贵州省社会发展攻关计划课题（黔科合SZ字[2014]3036号）；国家水利部公益性行业科研专项经费项目（201401050）；贵州省水利科技经费项目（KT201409）；贵州师范大学博士科研启动基金（202） Distribution of soil organic carbon related to environmental factors in typical rocky desertification ecosystems Author: Affiliation: Institute of South China Karst,Guizhou Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:选取中国西南3个典型喀斯特石漠化生态系统（贵州毕节鸭池高原山地石漠化区、贵阳红枫湖高原盆地石漠化区和关岭花江高原峡谷石漠化区）为研究区，广泛建立野外样地，开展石漠化生态系统土壤有机碳分布及其与石漠化等级、地形地貌、植被、土壤性质等环境因子的相关性研究。结果表明：1）喀斯特石漠化生态系统土壤有机碳含量较低，毕节鸭池、贵阳红枫湖和关岭花江3个石漠化生态系统平均值分别为23.42、25.78、26.03 g/kg，且3个不同地貌类型石漠化土壤有机碳含量无明显差异。2）土地覆被变化明显影响了土壤有机碳含量，原生森林土壤有机碳平均含量31.32 g/kg，是所有类型中最高的。随着土地覆被由原生森林至石旮旯地退化不断增加的过程，土壤有机碳含量显示先降低后增加的变化趋势。3）土壤有机碳与土壤特性有明显的相关性，与土壤总氮、水解氮、速效钾、总孔隙度、自然含水量、毛管持水量、田间持水量和上层渗透性存在极显著地正相关，与总磷、下层渗透性存在显著地正相关，与容重存在极显著地负相关。4）植物多样性的丰富度指数（R）和多样性指数（H）与土壤有机碳含量有明显的相关性，达到了极显著的水平。5）不同石漠化等级土壤有机碳含量有显著差异，随着石漠化干扰程度的递增，土壤有机碳含量显示了先减小后增加的趋势。研究结果对中国西南喀斯特森林生态保护、石漠化生态系统恢复重建以及应对全球气候变化碳循环的减源增汇具有重要的理论意义和实践指导价值。 Abstract:Karst rocky desertification is an important ecological issue hindering the socioeconomic development of the South China Karst region. In the present study, firstly, three typical rocky desertification regions-Bijie Yachi, Qingzhen Hongfenghu, and Guanling Huajiang, Guizhou Province, representing three different typical karst landforms-plateau mountain, plateau basin, and plateau gorge, respectively, were selected as experimental areas. Then, 90 sample plots with an area of 20 m×20 m each were established. The distribution of soil organic carbon (SOC) in relation to environmental factors (degree of rocky desertification, landform, vegetation, soil property, etc.) in these plots was determined using field measurements, laboratory detection, and mathematical statistics. The following results were obtained:1) The SOC content of karst rocky desertification ecosystems was low. The average content of the three experimental areas of Bijie Yachi (Plateau Mountain), Qingzhen Hongfenghu (Plateau Basin), and Guanling Huajiang (Plateau Gorge) was 23.42, 25.78, 26.03 g/kg, respectively. There was no significant (P=0.23) difference of SOC contents among the three different landform experimental areas. 2) Land cover change can affect the SOC content. The SOC content of virgin forest (31.32 g/kg) was the highest. With increased soil degeneration from virgin forest to gravel land, the SOC content first decreased and then increased. 3) The SOC content was correlated with soil physico-chemical properties. Specifically, the SOC content was extremely significantly positively correlated with total nitrogen content, hydrolyzed nitrogen content, available potassium content, total porosity, total phosphorus content, natural moisture capacity, field moisture capacity, capillary moisture capacity, and upper strata saturated permeability; significantly positively correlated with total phosphorus content and lower strata saturated permeability, and extremely significantly negatively correlated with soil bulk density. 4) The SOC content and plant diversity rich (R) and diversity (H) indices were extremely positively correlated. 5) There were significant differences of SOC contents between different degrees of rocky desertification. Along with increased degrees of rocky desertification, the SOC content initially decreased and then increased. Based on these results, the distribution pattern of the SOC content and its impact factors in karst rocky desertification ecosystems was clarified. These results have important implications for the protection of karst forest ecosystems, the reconstruction of rocky desertification ecosystems, and the response to global climate change. 参考文献 相似文献 引证文献

A spatial system dynamic model for regional desertification simulation – A case study of Ordos, China

A spatial system dynamic (SSD) model for simulating desertification was developed by integrating climate, soil water, population, economy, pasturage, and land use. Net Primary Production (NPP) was selected as an intermediate variable to measure the impacts of driving forces and desertification grades. Ordos in China was selected to test the model. Ten scenarios were designed to simulate desertification dynamics in Ordos from 2011 to 2030. The results showed that the SSD model was reliable, and the overall accuracy of desertification degree was approximately 83%. Climate factors had relatively higher sensitivities than other parameters. Although humid climate and sustainable development strategy would reduce desertified land area and desertification degree before 2025, the rapid increase in pasturage pressure would offset this trend. Arid climate and unsustainable development strategy would accelerate desertification expansion. For local government, it is necessary to persist in the present desertification prevention policy and completely banned grazing after 2025.

Integration of remote sensing techniques for monitoring desertification in Mexico

ABSTRACTDesertification is considered one of the most serious threats to arid, semiarid, and sub-humid environments. In this study, several remote sensing techniques were integrated for monitoring desertification in a semiarid region of the central Mexican plateau (state of Querétaro). Landsat TM images were used to compute the Normalized Difference Vegetation Index (NDVI), Bare-Soil Index (BSI), and albedo (α). A change vector analysis (CVA) examined changes in the direction and magnitude of indicators during the 1993–2011 period in order to detect degradations or improvements in land conditions over a period of time. In addition, a desertification degree index (DDI) was applied based on the NDVI–α relationship. The results indicated that in the semiarid zone of the state of Querétaro, 48.3% of land use corresponds with agricultural areas; 2.7% of the area does not present any degree of desertification, while 49% presents the following degrees of desertification: 5.5% extreme, 10.9% severe, 18.9% moderate, and 13.7% low. The DDI applied in this approach for evaluating this phenomenon at the regional and municipal level is an effective tool for identifying areas at risk of desertification, in addition to monitoring changes in the degree or direction of desertification.