Abstract: Sand fences made of punched steel plate (PSP) have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction. However, few studies have assessed the protective effect of PSP sand fences, especially through field observations. This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics (CFD) numerical simulation. The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8% and 70.8%, respectively. Moreover, the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8% and 81.1%, respectively. The sand-resistance efficiency of the double-row PSP sand fences was 65.4%. Sand deposition occurred close to the first-row sand fence; however, there was relatively little sand on the leeward side of the second-row sand fence. The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations, indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences. This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas. The output of this work is expected to improve the future application of PSP sand fences.

Abstract: During aeolian processes, the two most critical factors related to dust emissions are soil particle and aggregate saltation, which greatly affect the vertical profiles of near-surface dust concentrations. In this study, we measured PM10 concentrations at four different heights (0.10, 0.50, 1.00 and 2.00 m) with and without continuous and simultaneous aeolian saltation processes on a Gobi surface in northwestern China from 31 March to 10 April, 2017. We found that the vertical concentration profiles of suspended PM10 matched the log-law model well when there was no aeolian saltation. For the erosion process with saltation, we divided the vertical concentration profiles of PM10 into the saltation-affected layer and the airflow-transport layer according to two different dust sources (i.e., locally emitted PM10 and upwind transported PM10). The transition height between the saltation-affected layer and the airflow-transport layer was not fixed and varied with saltation intensity. From this new perspective, we calculated the airflow-transport layer and the dust emission rate at different times during a wind erosion event occurred on 5 April 2017. We found that dust emissions during wind erosion are primarily controlled by saltation intensity, contributing little to PM10 concentrations above the ground surface compared to PM10 concentrations transported from upwind directions. As erosion progresses, the surface supply of erodible grains is the most crucial factor for saltation intensity. When there was a sufficient amount of erodible grains, there was a significant correlation among the friction velocity, saltation intensity and dust emission rate. However, when supply is limited by factors such as surface renewal or an increase in soil moisture, the friction velocity will not necessarily correlate with the other two factors. Therefore, for the Gobi surface, compared to limiting dust emissions from upwind directions, restricting the transport of suspended dust in its path is by far a more efficient and realistic option for small areas that are often exposed to dust storms. This study provides some theoretical basis for correctly estimating PM10 concentrations in the Gobi areas.

Abstract: Dust emission and wind erosion are widespread phenomena in arid and semi-arid regions, which have far-reaching harmful effects to the environment. This study aimed to use microbial induced carbonate precipitation (MICP) method with Bacillus sphaericus to reduce soil losses that occur in a dust-producing area due to wind erosion in the Ilam Province, Iran. Soil samples at the 0–30 cm depth were used and sterilized in an autoclave for 2 h at 121°C and 103 kPa. Approximately 3 kg soils were weighed and poured in the 35 cm×35 cm×3 cm trays. Different treatments included two levels of B. sphaericus (0.0 and 0.5 OD), three levels of suspension volume (123, 264, and 369 mL), two levels of urea-chloride cementation solution (0.0 and 0.5 M), and two levels of bacterial spray (once and twice spray). After 28 d, soil properties such as soil mass loss, penetration resistance, and aggregate stability were measured. The results showed a low soil mass loss (1 g) in F14 formulation (twice bacterial spray+264 mL suspension volume+without cementation solution) and a high soil mass loss (246 g) in F5 formulation (without bacteria+264 mL suspension volume+0.5 M cementation solution). The highest (42.55%) and the lowest (19.47%) aggregate stabilities were observed in F16 and F7 formulations, respectively, and the highest penetration resistance (3.328 kg/cm2) was observed in F18 formulation. According to the final results, we recommended the formulation with twice bacterial spray, 0.5 M cementation solution, and 269 mL suspension volume as the best combination for soil surface stabilization. Furthermore, this method is environmentally friendly because it has no adverse effects on soil, water, and plants, thus, it would be an efficient approach to stabilize soil surface.

Abstract: Deserts are sensitive to environmental changes caused by human interference and are prone to degradation. Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand. However, the effects of grazing, which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification, on the greenhouse gas (GHG) fluxes from soils remain unknown. Herein, we investigated GHG fluxes in the Hobq Desert, Inner Mongolia Autonomous Region of China, at the mobile (desertified), fixed (vegetated), and grazed (re-desertified) sites from January 2018 to December 2019. We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential (GWP). CO2 was emitted at an average rate of 4.2, 3.7, and 1.1 mmol/(m2•h) and N2O was emitted at an average rate of 0.19, 0.15, and 0.09 µmol/(m2•h) at the grazed, fixed, and mobile sites, respectively. Mean CH4 consumption was as follows: fixed site (2.9 µmol/(m2•h))>grazed site (2.7 µmol/(m2•h))>mobile site (1.1 µmol/(m2•h)). GHG fluxes varied seasonally, and soil temperature (10 cm) and soil water content (30 cm) were the key micrometeorological factors affecting the fluxes. The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO2 and N2O emissions and decreased CH4 absorption. Grazing also significantly increased the GWP of the soil (P<0.05). This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage. These findings could be used to formulate informed policies on the management and utilization of desert ecosystems.

In semi-arid lands, vegetation is distributed in shrub patches immersed in a less vegetated interpatch matrix. Grazing affects perennial grass seed bank through a decrease in seed rain and an increase in seed predation and soil compaction. Nevertheless, some species with anchorage mechanisms in their seeds might overcome this, such as Nassella tenuis (Phil.) Barkworth. This is an important species in grazing paddocks because it has an intermediate palatability and its relatively tolerant to grazing. These characteristics allow N. tenuis to increase its abundance in grazed sites. Our objective was to assess how grazing affects the key palatable species from seeds to seedlings: i.e., seed rain, soil seed bank, and seedling recruitment in different microsites along a windward-leeward transect across shrub canopy. We hypothesized that: (1) the negative effects of grazing on N. tenuis fructification are reflected in its seed rain, soil seed bank, and seedling recruitment, especially in interpatches; (2) Nassella tenuis seed rain reduction, soil compaction by cattle in grazed sites, and removal of seeds by wind decrease its soil seed bank, especially in microsites exposed to the predominant wind; and (3) the decrease in N. tenuis soil seed bank and cover increase in annual species in grazed sites have negative effects on its seedling recruitment, especially in microsites exposed to predominant wind. We placed seed traps, collected soil samples, and monitored seedling recruitment in different locations around shrub canopy to address our hypotheses. Also, we established a manipulative experiment in which we sow N. tenuis seeds and followed its recruitment in different microsites. We compared the seed rain, soil seed bank, natural seedling recruitment, and sown seeds recruitment of N. tenuis between grazed and ungrazed sites. We analyzed differences between microsites along a windward-leeward transect across shrubs patches. Seed rain and soil seed bank had the same density in patches and interpatches both in ungrazed and grazed sites. But seed rain was higher, and soil seed bank was lower in ungrazed sites than in grazed sites. Almost all under-canopy microsites showed greater soil seed bank abundance and natural seedling recruitment in ungrazed sites. Sown seeds recruitment was the same between grazed and ungrazed sites, but it showed protective effects of shrubs in leeward microsites under grazed sites. As a conclusion, seed rain and soil seed bank are complementary under grazed sites.

为筛选苗期抗旱性较强的牧草，用于干旱半干旱地区的人工草地建植。采用盆栽法对6种牧草进行模拟
干旱试验，测定其株高（PH）、地上干重（SDW）、地下干重（RDW）、根冠比（RSR）、叶片相对含水量（RWC）、脯氨酸含
量（Pro）、可溶性蛋白含量（SP）、抗氧化酶活性等指标，计算单项指标抗旱系数，运用相关分析、主成分分析、隶属函
数法等方法对6种牧草进行抗旱性综合评价。结果表明：干旱胁迫对6种供试材料的生长和生理指标均有显著影
响。相关分析表明，PH、GR、RDW等12项指标之间呈正相关关系，但这12项指标均与丙二醛（MDA）含量呈负相关
关系。主成分分析表明，4个主成分贡献率可达98.40%，可代表6种供试材料绝大部分数据信息。结合隶属函数法
及权重，计算出6种供试材料的抗旱性综合评价值（D 值），得到供试材料的抗旱性能力顺序为：长穗偃麦草> 披碱
草>沙打旺>无芒雀麦>紫花苜蓿>扁穗冰草。D 值与PH（0.984**）、RDW（0.948**）、Pro（0.971**）和SP（0.959**）均呈显
著正相关，可作为相似材料苗期抗旱性评价的辅助指标。

：选取汾河流域为研究区，采用土地利用动态度、地学信息图谱、生态价值指数和植被覆盖度综合分析研究
区2000年、2005年、2010年、2015年及2018年土地利用变化及生态环境影响效应问题。结果表明：（1）2000—2018
年，流域建设用地、林地呈现增长趋势，增长面积分别为1350.90 km2、85.50 km2，增长率分别为92.83%、0.96%；耕地、
草地出现小幅下降趋势，缩减面积分别为729 km2、674.10 km2，缩减率分别为-5.02%、-7.63%；水域及未利用土地维
持多年平均水平，平均面积为297 km2、7.92 km2。空间格局呈现建设用地、耕地集中于流域核心区，草地、林地集中
于边缘区的分异特征。（2）各时序综合土地利用动态度、土地转移图谱、土地利用涨落势变化近似，显著变化区主要
位于流域盆地及其与山地过渡区，多年综合土地利用动态度为4.34%，单一土地利用动态度及土地利用涨势幅度最
高的是建设用地及林地。（3）基于不同的主导土地利用类型影响，生态价值指数时序演变呈现“下降-增长-下降”的
波浪状曲线特征；植被覆盖度经历“增长-下降-增长”的演变特征；空间格局上与土地利用变化区域呈现空间斑块
重叠。地形结构、用地标准、社会经济及环保政策等因子驱动下，未来流域土地利用变化或将加大，对生态环境的
胁迫增强。

研究耕地资源时空变化及驱动因子，对于提高区域粮食安全，严守耕地保护红线，制定耕地保护政策和措
施具有重要的实践意义。以甘肃省1995年、2005年、2015年和2020年4期土地利用数据为基础，在ArcGIS和Geo?
Da等技术的支持下，从栅格、格网和县域尺度全面分析了甘肃省近25 a耕地时空变化特征，并利用地理探测器对引
起耕地变化的主要驱动因子进行了探测。结果表明：（1）甘肃省1995—2020年间耕地减少幅度达1.6%，1995—
2005年耕地面积增加，2005—2020年耕地面积递减，且耕地主要流向草地、林地和建设用地，而未利用地主要向耕
地和草地转移。（2）耕地空间分布呈“东南多、西北少”的典型特征。耕地空间分布受自然因素和社会经济因素的共
同作用，其中，人口和土地开发强度的交互作用是1995年、2005年和2015年甘肃省耕地空间分布差异性的主要原
因，而2020年温度和降水的交互作用成为影响耕地的主导因素。研究结果可为甘肃省耕地保护管理提供科学依
据。

：利用延河流域1998年、2004年、2010年和2016年4期的Landsat遥感影像，计算遥感生态指数（Remote
Sensing Ecological Index，RSEI），对流域生态环境质量的时空变化进行分析和评价，利用CA-Markov模型对2022年
和2028年的生态环境进行模拟和预测。结果表明：（1）RSEI评价指数在延河流域具有较好的适用性，可用于监测
和评价流域生态环境的时空变化特征。（2）时间尺度上，RSEI均值从1998年的0.392变化为2016年的0.530，呈逐年
上升趋势，空间尺度上，RSEI从东南向西北逐渐增大。以0.2为间隔划分RSEI等级，发现流域生态环境质量等级以
较差和中等为主，占总面积的62.4%，主要分布于流域的山谷地带，优良等级的面积占比最小，约为8.1%，主要分布
于流域南部的山区地带。（3）自然和人为因素对流域生态环境质量变化的影响存在较大空间差异性。其中海拔在
1200~1800 m的区域，生态环境质量变化主要受自然因素影响；而海拔低于1200 m的区域，则主要受人类活动影
响。（4）预测到2028年，流域生态环境质量会持续提升，良好和优良等级的面积占比将达到66%，但是流域西北部
由于生态环境本底脆弱，仍存在较大的问题。

为探究荒漠灌丛对其沙堆土壤结构和养分空间异质性的影响，以白音恩格尔自然保护区的优势种红砂
（Reaumuria soongorica）灌丛沙堆为研究对象，对其土壤粒度组成及土壤养分积累特征进行分析。结果表明：（1）研
究区土壤粒径组成以细砂为主，含量为36.34%~65.31%，黏粒、粉粒含量均小于7.00%；（2）红砂灌丛沙堆沉积物趋
于细化，由背风侧、迎风侧到沙堆间空地土壤颗粒分选性依次变差，峰态逐渐宽平，分形维数逐渐变小，灌丛沙堆土
壤粒径组成含量分布较丘间空地更对称；（3）灌丛沙堆迎风侧和背风侧有机质（SOM）、碱解氮（AN）、速效磷（AP）、
速效钾（AK）含量分别较沙堆间空地增加29.37%和40.63%、23.49%和35.12%、62.72%和66.45%、30.10%和22.75%
（P<0.05），且相对作用强度（Relative Interaction Intense, RII），即RII>0。红砂灌丛起到防风滞沙和重新分选沙粒的
作用，并且在丛间地风蚀和植物反馈作用下养分向灌丛沙堆富集，形成“肥岛”效应。