Minqin Oasis Research Articles

Evaluation of energy balances and greenhouse gas emissions from different agricultural production systems in Minqin Oasis, China.

Agricultural production in Minqin Oasis, China, is commonly categorized as intensive crop production (ICP), integrated crop–livestock production (ICLP), intensive livestock production (confined feeding) (IFLP), and extensive livestock production (grazing) (EGLP). The objectives of the present study were to use a life cycle assessment technique to evaluate on-farm energy balances and greenhouse gas (GHG) emissions of agricultural production, and to compare the differences among the four systems. Data used in the present study were collected from published literature and face-to face questionnaires from 529 farms in eight towns (two towns per production system) within Minqin county. The ANOVA of averaged data from 2014 to 2015 indicated that the net energy ratio (Output/Input) for the EGLP system was significantly higher than that for any other system (P < 0.01), whereas the difference among other three systems were not significant. The EGLP system generated lower CO2-eq emissions per hectare of farmland than other systems (P < 0.01). Relating carbon economic efficiency to market values (US$) of agricultural products, indicated that the carbon economic efficiency (US$/kg CO2-eq) of the IFLP system was significantly greater than that of other systems (P < 0.01). The major GHG emission sources varied across the systems, that is, soil respiration is the dominant source in EGLP, while the main sources in IFLP are enteric methane and manure management; in ICLP major sources are enteric methane, soil respiration and fertilizer; and in ICP are soil respiration and fertilizer. The structural equation modelling analysis showed that livestock category was strongly linked to net income. The direct effects and total effects of water use efficiency, via its positive influence on energy balances and GHG emissions were much stronger than those of other dependent variables. The study provides important benchmark information to help develop sustainable agricultural production systems on energy balances and GHG emissions in northwestern China.

Derivation of salt content in salinized soil from hyperspectral reflectance data: A case study at Minqin Oasis, Northwest China

Soil salinization is a serious ecological and environmental problem because it adversely affects sustainable development worldwide, especially in arid and semi-arid regions. It is crucial and urgent that advanced technologies are used to efficiently and accurately assess the status of salinization processes. Case studies to determine the relations between particular types of salinization and their spectral reflectances are essential because of the distinctive characteristics of the reflectance spectra of particular salts. During April 2015 we collected surface soil samples (0–10 cm depth) at 64 field sites in the downstream area of Minqin Oasis in Northwest China, an area that is undergoing serious salinization. We developed a linear model for determination of salt content in soil from hyperspectral data as follows. First, we undertook chemical analysis of the soil samples to determine their soluble salt contents. We then measured the reflectance spectra of the soil samples, which we post-processed using a continuum-removed reflectance algorithm to enhance the absorption features and better discriminate subtle differences in spectral features. We applied a normalized difference salinity index to the continuum-removed hyperspectral data to obtain all possible waveband pairs. Correlation of the indices obtained for all of the waveband pairs with the wavebands corresponding to measured soil salinities showed that two wavebands centred at wavelengths of 1358 and 2382 nm had the highest sensitivity to salinity. We then applied the linear regression modelling to the data from half of the soil samples to develop a soil salinity index for the relationships between wavebands and laboratory measured soluble salt content. We used the hyperspectral data from the remaining samples to validate the model. The salt content in soil from Minqin Oasis were well produced by the model. Our results indicate that wavelengths at 1358 and 2382 nm are the optimal wavebands for monitoring the concentrations of chlorine and sulphate compounds, the predominant salts at Minqin Oasis. Our modelling provides a reference for future case studies on the use of hyperspectral data for predictive quantitative estimation of salt content in soils in arid regions. Further research is warranted on the application of this method to remotely sensed hyperspectral data to investigate its potential use for large-scale mapping of the extent and severity of soil salinity.

Glomalin-Related Soil Protein and Its Relationship with Organic Carbon and Nitrogen in Water-stable Aggregates in Abandoned Agricultural Lands

A large number of studies have shown that glomalin-related soil protein (GRSP) plays an important role in soil aggregate formation and soil carbon balance. However, to date, we lack understanding on the relationship between GRSP and water-stable aggregates (WSA) in abandoned agricultural lands of semi-arid region. We considered abandoned agricultural lands of different ages in Minqin Oasis as the research object. We discussed the changes of GRSP and the relationship between GRSP and WSA during land abandonment. The research results showed the following: the content of extractable glomalin-related soil protein (e-GRSP) and total glomalin-related soil protein (t-GRSP) is higher than that of traditional arable lands, and the content increases as the years of land abandonment increase. e-GRSP and t-GRSP contents are higher than the soil layer of 0–20 and 40–60 cm in terms of vertical section. The proportion ranges of e-GRSP and t-GRSP in soil total organic carbon (TOC) are 0.62%–2.0% and 1.97%–8.1% respectively in the abandoned agricultural lands. e-GRSP and t-GRSP also exhibit significant quadratic correlation with TOC (<i>P</i><0.05). e-GRSP and t-GRSP have significant positive correlation with mean weight diameter (<i>P</i><0.05). Significant and extremely significant positive correlations are observed between the e-GRSP and t-GRSP and the WSA with particle sizes between 0.25–1 and >2 mm and the organic carbon (OC) and nitrogen (N) existing in such sizes, respectively. In addition, significant and extremely significant negative correlation exist between the e-GRSP and t-GRSP and the clay and silt contents (<0.053 mm) and the OC and N in clay and silt. In general, land abandonment has raised the GRSP content. Moreover, the GRSP after land abandonment tends to promote large WSA formulation and organic matter enrichment in large aggregates. Organic matter accumulation in clay and silt was also inhibited. This phenomenon helps build a reasonable aggregate hierarchy and improve the stability of soil aggregates.

An Interval Quadratic Fuzzy Dependent-Chance Programming Model for Optimal Irrigation Water Allocation under Uncertainty

In this study, an interval quadratic fuzzy dependent-chance programming (IQFDCP) model is proposed for irrigation water management under uncertainty. This model can deal with the interval and fuzzy uncertainties encountered in optimal irrigation water resources allocation problems. It takes optimal credibility level of system revenue as the objective function for addressing the conflict between maximum system revenue and the credibility level of the system revenue. By providing three scenarios of precipitation, the optimal solutions are obtained. The developed model is applied to a case study for irrigation water allocation in Minqin Oasis, Wuwei city, northwest China. This study can help determine how much irrigation water should be allocated to different crops under the maximum credibility level of the system revenue. The optimal solutions can provide a certain credibility level of system revenue corresponding to different scenarios and mitigate the system-failure risk level of water shortages in arid areas. Moreover, because the IQFDCP can objectively reflect the interrelationship among crop irrigation water amount, system revenue, and system-failure risk level, the results are able to provide advices to decision makers for efficiently managing water resources in different scenarios.

Farmers’ livelihood adaptation to environmental change in an arid region: A case study of the Minqin Oasis, northwestern China

Adaption to global environmental change is a focus of sustainability research. Farmers face multiple environmental and social pressures due to global environmental change. Effective livelihood changes must be taken to decrease asset losses and to adapt to current or future environmental challenges. However, there are few studies that systematically understand and assess farmers’ livelihood adaptation. We developed an integrated analytical framework for livelihood adaptation and explored the relationships between adaptive capacity, adaptation outcomes, and farmers’ adaptation strategies. We applied this framework to a case study of the Minqin Oasis in China and assessed the livelihood adaptation of farmers facing environmental change and water scarcity. Household surveys and semi-structured interviews were used for data collection. We found that (1) farmers’ livelihood adaptation choices were limited due to current government policies and their own resources and (2) livelihood adaptive capacity (such as land, water resources, and social networks) and policy reform (water resource fees, and cultivated land compression) had a key impact on farmers’ adaptation. The factors representing a poor livelihood strategy and adaptation outcomes of the farmer include the following: (1) a low level of livelihood awareness among farmers (such as passive farmers), (2) a lack of livelihood assets, (3) government focus on environmental recovery, and (4) a weakened role of the market. To improve the adaptation of farmers’ livelihoods to environmental change, these measures must balance the relationship between environmental restoration and farmers’ livelihoods, consider a variety of key forces, and guide farmers to adopt effective strategies. This study facilitates the development of livelihood adaptation analysis methods for global change studies. Case-based research results can be used to improve local decision-making and can provide an assessment reference method for farmer adaptation to regional and global environmental change.

State corporatism and environmental harm: Tax farming and desertification in northwestern China

AbstractResearch on environmental governance in China has shown that centre–local relations often influence the implementation and efficacy of environmental regulations. By examining changes in resource allocation and rural development between 1982 and 2005 in the region worst affected by desertification in China—the Minqin oasis in Gansu—we argue that changes in macro‐level fiscal and commodity grain policies contributed to severe regional disparity and a reduction in local state capacity in hinterland China. Intergovernmental competition over fiscal revenue encouraged cash cropping and land reclamation, and the continuous decline of the oasis ecology further reduced legitimacy in rural governance. These institutional and ecological constraints shaped the behaviour of grassroots cadres and formed the conflicting interests of the state in resource distribution and environmental conservation that continued to exist until the implementation of a centralized conservation program in 2006. The data came from 157 interviews and 628 policy documents from local archives in Gansu.

The Treadmill of Taxation: Desertification and Organizational State Deviance in Minqin Oasis, China

Green criminology has long proposed a political economy approach towards the study of environmental harm. This paper engages with that emerging scholarship by examining how land reclamation and organizational state deviance contributed to severe desertification from 1986 to 2005 in Minqin County, China. Specifically, the study examines how macro-level tax reforms in post-socialist China provided the motive, opportunities, and operationality of social control that enabled the under-enforcement of conservation regulations in the Minqin oasis. The findings demonstrate that organizational state deviance was structured in an interwoven web of fiscal obligations and patronage relationships generated by the incessant tax burden imposed on grassroots state actors and local farmers. The data comes from 110 in-depth interviews of local farmers and grassroots actors as well as 7237 pages of policy reports gathered from regional and local archives in northwestern China.

民勤绿洲边缘梭梭林衰败过程中土壤种子库动态及其与地上植被的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 民勤绿洲边缘梭梭林衰败过程中土壤种子库动态及其与地上植被的关系 DOI: 10.5846/stxb201706141084 作者: 作者单位: 甘肃省治沙研究所 甘肃河西走廊森林生态系统国家定位观测研究站,甘肃省治沙研究所,甘肃省治沙研究所,甘肃省治沙研究所,甘肃省治沙研究所 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（31360203）；甘肃省创新群体项目（145RJIA335） Dynamic changes in soil seed banks and their relationships with aboveground vegetation during the decaying of Haloxylon ammodendron plantations at the edge of the Minqin oasis Author: Affiliation: Gansu Hexi Corridor Fores Ecosystem National Research Station & Gansu Desert Control Research Institute,Gansu Hexi Corridor Fores Ecosystem National Research Station,,, 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:为了探明民勤绿洲边缘梭梭林衰败过程中土壤种子库演变特征及其与地上植被的关系，以民勤西沙窝——勤治沙综合试验站1987年建植的未衰败（ND）、轻度衰败（SLD）、中度衰败（MD）以及重度衰败（SD）梭梭林为对象，通过野外调查及室内萌发的方法对林地土壤种子库物种组成、密度、物种多样性及其与地上植被的关系进行了研究。结果表明：1）梭梭林由未衰败向重度衰败演变过程中，种子库草本植物物种数先急剧增大再缓慢减小（峰值在SLD阶段），木本植物物种数先急剧减小再保持恒定；种子库优势种呈现出由沙生植物向沙旱生植物演替的趋势；大部分林地种子库与地上植被物种间存在较高的相似性。2）梭梭林衰败过程中，草本植物种子库密度呈现出急剧增大后缓慢减小趋势，SLD、MD及SD的密度分别是ND的2.57、2.32、2.28倍；木本植物种子库密度处于持续增大状态，SLD、MD、SD的密度分别是ND的5.25、11.38、14.74倍；种子库与地上植株密度间存在正相关关系，其中，草本植物为对数曲线，木本植物为二次函曲线。3）梭梭林从衰败初期（SLD）演变到后期（SD），种子库中草本植物物种多样性指数Dma、Dsim、H'、Jsw均呈现出先稳定后变化的状态，而木本植物的4种指数一直呈现出减小的趋势；种子库草本植物物种多样性指数变化趋势与其地上植被存在差异，但其变化幅度基本一致；种子库木本植物与地上植被的物种多样性指数变化趋势完全一致，其种子库的变化幅度小于地上植被。基于以上结果得出，民勤梭梭林衰败过程中林地植物群落发生了由沙生植物向沙旱生植物的演替，林地植被与土壤种子库间存在很强的依赖性，衰败梭梭林林地土壤种子库具有较高的植被恢复能力。 Abstract:The Minqin oasis is located in the northwest Hexi Corridor, and the northern, western, and eastern edges are surrounded by the Tengger and Badain Jaran deserts. To manage sand and prevent sandstorms, large tracts of Haloxylon ammodendron plantations were previously planted on the fixed and semi-fixed sand dunes of the Minqin oasis fringe. At present, parts of the H. ammodendron plantations, especially those close to the oasis, have presented with a degradation phenomenon due to multiple affecting factors. To ascertain the changes in soil seed banks and their relationships with aboveground vegetation during the degradation process of H. ammodendron plantations, some tracts of H. ammodendron plantations planted in 1987 were divided into no degradation (ND), slight degradation (SLD), moderate degradation (MD), and serious degradation (SD) stages, according to the growth status of these plants and their seedlings, as well as the coverage of biological soil crust. In the present study, the species composition, density, and species diversity of soil seed banks and their relationships with aboveground vegetation were studied, with field monitoring and indoor germination methods. The results showed that 1) with an increased degree of degradation of H. ammodendron plantations, the number of woody plants in the soil seed banks first decreased rapidly and then remained stable, and the number of herb plants in the soil seed banks, first increased rapidly and then decreased slowly, so that the peak emerged at the SLD stage. At the same time, dominant species in soil seed banks presented a succession trend from typical psammophytes to xerophytes, and the species similarity coefficients of soil seed banks and aboveground vegetation, as calculated by Jaccard's similarity coefficient, appeared to increase from ND to SLD and then decrease from SLD to SD. 2) The soil seed bank density of herb plants rapidly increased their stage of degradation from ND to SLD and slowly decreased from SLD to SD, while the soil seed bank density of woody plants has been increasing continuously and dramatically. The densities of herb plants and woody plants in the SLD, MD, and SD stages were 2.57 and 5.25, 2.32 and 11.38, and 2.28 and 14.74 times higher than that of ND, respectively. There was a positive correlation between the species in soil seed banks and aboveground vegetation, such that this relationship for herb plants can be described with a logarithmic curve of y=aln (x) + b (a ≠ 0), and for woody plants may be described with a quadratic curve of y=ax2 + bx + c (a ≠ 0). 3) With the evolution from the SLD stage in H. ammodendron plantations to the SD stage, some species diversity indices, such as Dma, Dsim, H', and Jsw, of herb plants in soil seed banks were initially obviously stable and then showed significant change, while the indices of woody plants showed continuous change. In addition, some obvious differences have been presented between trends of these indices in soil seed banks and in aboveground plants, while the degrees of change in soil seed banks were similar to those of aboveground plants. The changes in trend in the indices of woody species in soil seed banks were completely consistent with those in the indices of aboveground plants; however, the degrees of change in soil seed banks were smaller than those in the aboveground plants. These findings suggest that the degradation of H. ammodendron plantations is a succession from psammophytes to xerophytes, there is a strong interdependence between soil seed banks and aboveground vegetation, and soil seed banks in the degrading plantations will have a stronger potential for vegetation recovery due to the increase in seed bank stocks of some species, which is a response to increase the stability of the plant communities. 参考文献 相似文献 引证文献

The Treadmill of Taxation: Desertification and Organizational State Deviance in Minqin Oasis, China

Green criminology has long proposed a political economy approach towards the study of environmental harm. This paper engages with that emerging scholarship by examining how land reclamation and organizational state deviance contributed to severe desertification from 1986 to 2005 in Minqin County, China. Specifically, the study examines how macro-level tax reforms in post-socialist China provided the motive, opportunities, and operation of social control that enabled the under-enforcement of conservation regulations in the Minqin oasis. The findings demonstrate that organizational state deviance was structured in an interwoven web of fiscal obligations and patronage relationships generated by the incessant tax burden imposed on grassroots state actors and local farmers. The data comes from 110 in-depth interviews of local farmers and grassroots actors as well as 7,237 pages of policy reports gathered from regional and local archives in northwestern China.

Environmental policy evaluation from the perspective of farmers' perception in arid oasis ecosystem: Experiences of Minqin, Northwest China

Effective eco-environment rehabilitation is an essential policy issue in arid oasis ecosystem. Since 2007, a policy which focuses on environment restoration and protection was implemented in the Shiyang River Basin of Gansu Province, China. Using Minqin oasis as a case, the effectiveness of policy impacts based on farmers’ perception was evaluated. In addition, an ordinal logistic regression model was used to explore the potential factors affecting farmers’ perception of policy effectiveness. Data were collected from household heads or spouses and other adults (age&gt;18) separately in a random sample of 425 households. The results showed that positive outcomes were achieved, however, two policy measures—the water restrictions and the ecological migration project—were rated at a low level of satisfaction by the farmers. Moreover, 11 determinants were extracted by the logistic regression method, and indicating that economic factors including the ownership of the arable land and the availability of household income turned out to be the most significant. The results can help to establish eco-environmental restoration targets, encourage investments, and lead to the development of more applicable methods for assessing policy effects from the perspective of smallholders in ecologically fragile areas all over the world. Keywords: Environmental policy evaluation; Farmers’ perception; Ordinal logistic regression; Minqin oasis; Northwest China

The critical role of local policy effects in arid watershed groundwater resources sustainability: A case study in the Minqin oasis, China

Designed as a watershed groundwater restoration policy (WGRP), the Comprehensive Treatment Program of the Shiyang River Basin (CTSRB) was launched in 2006 to restore the groundwater resources in the Minqin oasis, northwestern China. This study sought to verify the recovery effects of CTSRB implementation from the perspective of groundwater depth. We reconstructed the spatio-temporal distribution of groundwater depth at interannual and pixel scales by using digital groundwater depth models (DGDMs), based on the ordinary kriging interpolation method. Using DGDMs data, various measures of the groundwater table (e.g., regional depths, surface areas, depletion cones, and conditions in irrigated regions including Ba, Quanshan, and Hu) were quantitatively analyzed and compared for the pre-CTSRB (2001–2006), CTSRB I (2006–2010), and CTSRB II (2010–2015) periods, for which spatial trends in the annual amplitudes of groundwater depth were compared. Finally, strategies that impacted the groundwater behavior before and during the CTSRB periods, possible indirect and adverse effects, and long-term strategies and prospects were discussed. The results showed that groundwater depth first declined sharply, before increasing slowly and stabilizing after implementation of the CTSRB. Areas of greater groundwater depth (<−20m) and four groundwater depletion cones expanded during the pre-CTSRB period, whereas variable shrinking trends were detected during the CTSRB period. Spatial analysis showed that groundwater recovery mainly occurred along the periphery of the three irrigated regions, among which recovery effects in Hu were more obvious than those in Quanshan and Ba, with pumping-well densities the main reason for the difference. Therefore, various strategies (increasing the surface water supply, reducing groundwater mining, and some other auxiliary measures) of CTSRB together supported groundwater recovery in the Minqin oasis. Overall, this research demonstrates an innovative perspective to verify the effects of WGRPs in arid and semi-arid areas.

Water shortage and inequality in arid Minqin oasis of northwest China: adaptive policies and farmers’ perceptions

ABSTRACTMinqin oasis, located at the lower reaches of the Shiyang River in northwest China, is one of the driest regions in the world. Severe water shortage has exacerbated the vulnerability of local ecosystems and the agricultural livelihood of farmers, and ecological failure threatens the environmental security of the region. Since 2007 China has implemented a range of strategic programmes and policies on water management which involve governments at all levels and include a diversity of adaptive actions in this region. However, rural households do not benefit equally from the policies and programmes. This study addresses two questions: first, how are inequality issues addressed in water-related policies and programmes? And second, what demographic and socio-economic factors at the household level are significantly related to the inequality in benefit sharing arisen from the implementation of these policies? The study employs a mixed method approach, integrating a qualitative approach that investigates policy documents with a quantitative approach that analyses primary data collected from a household survey in Minqin in 2012. The study finds that there are inadequate financial and instrumental resources put in place to address the causes of inequality. Unequal holdings of household capital, especially social capital and political status, significantly influences whether or not farmers can benefit from the water-related policies and schemes as practiced in the study area. Addressing the root causes of unequal benefits from water-related policies is urgent if China aims to achieve policy goals and sustainable development in this ecologically vulnerable region.

Suspended dust particle characteristics during an sandstorm on 29 February 2008 in Minqin area, China

Aeolian dust is one of the main aerosols in the troposphere, and plays an important role in the Earth’s climate system. In this study, detailed meteorological conditions and dust particle diameters were measured at three sites with different landscape characteristics in the Minqin oasis area of northwest China, on 29 February 2008. We show that as dust storms progressed through the desert into the oasis, variation in the character of the underlying land surface not only influenced the wind profile by modifying the frictional velocity of air (U∗), aerodynamic roughness length (Z0), horizontal sediment flux, and dust concentration of the near surface sublayer (1–49 m), but it also changed the vertical structure of the aeolian sediment transport pattern. The particle size frequency distributions at three distinct sites were all unimodal, comprising a large number of aeolian dust particles with sizes less than 63 μm (more than 65%). During transport, dust particle populations shifted to smaller sizes. Clearly, the influence of landform, windbreaks, and vegetation cover on horizontal sand-dust flux decreased with height as well as increasing particle size, with smaller aeolian particles being more easily captured by windbreaks, and vegetation.

Analysis of the Spatial Variation of Soil Salinity and Its Causal Factors in China’s Minqin Oasis

Land salinization and water resource deterioration negatively affect irrigated agriculture in arid and semiarid areas by limiting the area of arable land and reducing crop yields. The spatial variation of soil salinity is affected by many factors, and their interactions are complex. In this study, we utilized grey relational analysis to evaluate the factors that affect soil salinity in China’s Minqin Oasis and the interactions among them and then ranked the significance of their impacts on soil salinity for different land use and cover types. The data used in this study include data obtained from soil chemical analyses based on field sampling in 2015 and hydrological data obtained from local government agencies. We found that the main factors that affect soil salinity in the region’s sparse grassland are groundwater salinity and vegetation cover; the least important factor was the distance to the nearest irrigation canal. For cropland, the most important factors were the distance to irrigation canals and hydrological factors. By accounting for these factors, it should be possible to manage the region’s limited natural water and soil resources more efficiently, while allowing remediation of existing salinized land and helping to maintain sustainable agriculture in this arid land.

民勤绿洲边缘沙丘生物土壤结皮发育对浅层土壤质地、养分含量及微生物数量的影响

民勤绿洲边缘沙丘生物土壤结皮发育对浅层土壤质地、养分含量及微生物数量的影响

Residual plastic mulch fragments effects on soil physical properties and water flow behavior in the Minqin Oasis, northwestern China

The covering of complete plastic films on soil would affect physical and biochemical properties of the soil microenvironment. Residual plastic film fragments (RPFF), which is left behind after retrieving the most of plastic films, could affect the flow behavior in the arable layer. This study was designed to assess the potential effects of RPFF on soil physical properties, water infiltration and distribution in the soil. Treatments with and without residual plastic film fragments (RPFF and NRPFF, respectively) were performed. A dye tracer was introduced to track the water movement, and the physical properties of the soil and the dynamic behavior of water transport in the soil column of the arable layer (0–20cm) were determined. The initial gravimetric water content, bulk density, total porosity in 0–20cm was significantly different between RPFF and NRPFF treatment. The dark blue area in maize root and densely rooted zones under RPFF decreased by 99% and 4%, respectively, relative to that under NRPFF. The sharply changing state of infiltration and outflow indicated that water flowed along a preferential path, e.g., macro-pores in NRPFF and residual plastic film pieces in RPFF. After clearing the RPFF, the time of equilibrium in 0–5, 5–10, 10–15, and 15–20cm soil columns decreased by 48%, 50%, 49%, and 45%, respectively. Our results highlighted that the presence of RPFF significantly influenced soil physical properties, altered soil water distribution, and decreased the matching degree of the flow distribution region and the maize root (densely rooted) zone. The present study demonstrated that the importance of clearing the RPFF for irrigation water management in agriculture produces.

Agricultural Soil Alkalinity and Salinity Modeling in the Cropping Season in a Spectral Endmember Space of TM in Temperate Drylands, Minqin, China

This paper presents the potential of the four-image spectral endmember (EM) space comprising sand (SL), green vegetation (GV), saline land (SA), and dark materials (DA), unmixed from Landsat TM/ETM+ to map dryland agricultural soil alkalinity and salinity (i.e., soil alkalinity (pH) and soil electrical conductivity (EC)) in the shallow root zone (0–20 cm) using partial least squares regression (PLSR) and an artificial neural network (ANN). The results reveal that SA, SL, and GV fractions at the subpixel level, and land surface temperature (LST) are necessary independent variables for soil EC modeling in Minqin Oasis, a temperate-arid system in China. The R2 (coefficient of determination) of the optimized parameters with the ANN model was 0.79, the root mean squared error (RMSE) was 0.13, and the ratio of prediction to deviation (RPD) was 1.95 when evaluated against all sampled data. In addition to the aforementioned four variables, the DA fraction and the recent historical SA fraction (SAH) in the spring dry season in 2008 were also helpful for soil pH modeling. The model performance is R2 = 0.76, RMSE = 0.24, and RPD = 1.96 for all sampled data. In summary, the stable EMs and LST space of TM imagery with an ANN approach can generate near-real-time regional soil alkalinity and salinity estimations in the cropping period. This is the case even in the critical agronomic range (EC of 0–20 dS·m−1 and pH of 7–9) at which researchers and policy-makers require near-real-time crop management information.

Contents of soil organic carbon and nitrogen in water-stable aggregates in abandoned agricultural lands in an arid ecosystem of Northwest China

Soil organic matter content in water-stable aggregates (WSA) in the arid ecosystems (abandoned agricultural lands especially) of China is poorly understood. In this study, we examined the WSA sizes and stability, and soil organic carbon (OC) and nitrogen (N) contents in agricultural lands with abandonment ages of 0, 3, 12, 20, 30 and 40 years, respectively, in the Minqin Oasis of Northwest China. The total soil OC and N contents at depths of 0–20, 20–40 and 40–60 cm in abandoned agricultural lands were compared to those in cultivated land (the control). Agricultural land abandonment significantly (P<0.05) influenced the distribution of MWD (mean weight diameter), and OC and N contents. There were significant increases in MWD and the proportion of macroaggregates (sizes >0.25 mm) as the age of agricultural land abandonment increased. The effect of abandonment ages of agricultural lands on MWD was determined by the changes of OC and N accumulation in WSA sizes >2 mm. The total OC and N contents presented a stratification phenomenon across soil depths in this arid ecosystem. That is, both of them decreased significantly at depths of 0–20 and 40–60 cm while increased at the depth of 20–40 cm. The WSA sizes <0.053 mm had the highest soil OC and N contents (accounting for 51.41%–55.59% and 42.61%–48.94% of their total, respectively). Soil OC and N contents in microaggregates (sizes 0.053–0.25 mm) were the dominant factors that influenced the variations of total OC and N contents in abandoned agricultural lands. The results of this study suggested that agricultural land abandonment may result in the recovery of WSA stability and the shifting of soil organic matter from the silt+clay (<0.053 mm) and microaggregate fractions to the macroaggregate fractions. However, agricultural land abandonment did not increase total soil OC and N contents in the short-term.

民勤绿洲边缘2种生境红砂种群分形特征及影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 民勤绿洲边缘2种生境红砂种群分形特征及影响因素 DOI: 10.5846/stxb201504120741 作者: 作者单位: 甘肃省治沙研究所,甘肃省治沙研究所,国家林业局泡桐研究开发中心,浙江农林大学,甘肃省治沙研究所,中国林科院,甘肃省治沙研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划（2012CB723203）；国家自然科学基金资助项目（41161006）；国家科技支撑项目（2012BAD16B0203）；甘肃省青年基金（1308RJYA081）；甘肃省沙生植物保护利用科技创新团队资助项目（1207TTCA002） A study of fractal properties of spatial distribution of Reaumuria soongorica population and its influencing factors in Minqin Oasis Fringe Author: Affiliation: Gansu Desert Control Research Institute,Gansu Desert Control Research Institute,,,,, 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:以民勤绿洲边缘丘间低地和梭梭林固定沙丘2种生境下红砂种群为研究对象，采取空间替代时间和分形维数（计盒维数、信息维数和关联维数）研究了红砂种群的结构特征和空间格局的分形特征，并对其影响因素做了主成分分析，研究结果表明：（1）红砂种群在丘间低地生境下，主要集中在龄级Ⅰ，更新较好；在固定沙丘生境下，主要集中在龄级Ⅲ，更新受到很大的限制。（2）与梭梭林固定沙丘生境下相比，丘间低地生境下红砂种群个体间竞争较弱，但占据和利用空间能力较强且格局强度较大。红砂种群的计盒维数和信息维数对种群的个体数量、更新状况和分布情况反映灵敏，而且关联维数在干旱地区有其特定的生态学意义，即只表示种群竞争的强弱。（3）分形维数不仅与群落结构（密度、幼体数量等）有关，还与生境因子有关。主成分分析表明，土壤结皮类型是红砂种群格局分形维数的第一主成分，土壤含水量、土壤全盐量分别是第二和第三主成分，这三个主成分的累计贡献率为80.002%。（4）建议在防风固沙和植被恢复时，丘间低地生境下可以通过增大红砂Ⅰ小龄级个体的密度来提高整体的防风固沙能力和幼苗的成活量，但在梭梭林固定沙丘生境下如何提高红砂Ⅰ小龄级个体的成活率是保护和利用红砂的关键。 Abstract:Selecting the two ecological habitats (interdunal depression and fixed dunes) of the Minqin oasis fringe as our study area, the chronosequence method, fractal dimension (including box-counting dimension, information dimension and correlation dimension) analyses, and principal component analysis were used to study the population structure and spatial heterogeneity of Reaumuria soongorica, as well as the primary factor influencing these characteristics. The results were as follows:(1) R. soongorica individuals in the interdunal depression, which were mainly in age class Ⅰ, regenerated more readily than those of age class Ⅲ growing on the fixed dunes. (2) The intraspecific competition within R. soongorica was not intense in the interdunal depression, but the population occupied and utilized relatively larger ecological spaces here and exhibited higher levels of spatial heterogeneity when compared to those in the fixed dunes habitat. In addition, the box-counting dimension and information dimension methods were sensitive to individual number, renewal ability, and spatial pattern, while the correlation dimension was often used to illustrate the potential for intraspecific competition in arid regions. (3) Besides community structure (which includes the population density and seedling abundance), environmental factors affected the fractal dimensions. The principal component analysis suggested that soil crust type was the primary principal affecting the fractal dimension, followed by soil water content and soil salt content, which together accounted for 80.002% of the variance within the fractal dimension. (4) When these ecological projects (such as windbreak, sand-fixation, and vegetation rehabilitation) were conducted, it was advised that the windbreak, sand-fixation, and survival rate of seedlings were improved by increasing the individual density of R. soongorica plants in age class Ⅰ growing in the interdunal depression. Thus, strategies for facilitating increase in the survival rate of R. soongorica seedlings have become a key part of utilizing and protecting the R. soongorica population growing on fixed dunes. 参考文献 相似文献 引证文献

The protective effects of nebkhas on an oasis

Oases are of great importance to the sustainable development of economies and societies in desert regions. Thus, it is important to understand how many oases have survived for hundreds and even thousands of years. Oases in Northwest China include nearly all of the types found across the world. Among these oases, the Minqin Oasis, surrounded by mobile sandy deserts, is a stereotypical natural oasis that has been developed for more than 2000 years, making it ideal for a case study. Our investigation indicates that the nebkhas belt at the fringe of the Minqin Oasis, which consists of three sub-belts semi-mobile, semi-fixed and fixed nebkhas from desert to the oasis, plays a key role in its stability. The fractional speed-up ratio (δs) of wind generally fell within the range of −0.15 to −0.55 below the height of 0.6 m. Above the height of 0.6 m, wind velocity in the semi-mobile nebkhas was 5–27% weaker with a maximum reduction of 65% in the other two sub-belts. When wind carrying sand and dust from the desert passes through each sub-belt, its velocity is weakened by vegetation and dunes, and almost all sand and dust is deposited in the nebkha belt incrementally by grain size, ranging from coarse to fine. As such, nebkhas serve as a protection belt and ensure the existence of oases.