Soil erosion is a serious problem in hilly and mountainous areas, and hedgerows provide dual ecological and economic benefits. However, the effects of specific hedgerow species on soil erosion control and hydrodynamic processes remain unclear. In situ inflow experiments were performed in fields with five hedgerow species (Paspalum notatum, Melilotus officinalis, Festuca arundinacea, Medicago sativa, and Spiraea thunbergii) on hillslopes with 3o, 6o, 9o, and 15o slope gradients under an inflow intensity of 1.0 L m−2 min−1. The results indicate that, in terms of decreasing runoff rates and soil erosion rates, F. arundinacea performed best on the 3o and 6o hillslopes, P. notatum performed best on the 9o and 15o hillslopes, and M. officinalis and M. sativa performed moderately, while S. thunbergii performed worst. Compared with those on the other hillslopes, the runoff rates and soil erosion rates on the 6o hillslope decreased the most. Additionally, compared with the CK, M. sativa (6o and 15o hillslopes) and S. thunbergii (3o and 9o hillslopes) caused the greatest decreases in τ (shear stress), whereas F. arundinacea exhibited optimal regulation effects for V (mean flow velocity), Re (Reynolds number), Fr (Froude number), f (resistance coefficient), ω (stream power), and φ (unit stream power) on all the hillslopes. The greatest decreases in V above and below the hedgerows occurred on the 6o (27.5%) and 3o (61.2%) hillslopes, respectively, whereas the greatest decrease in τ occurred on the 15o hillslope, decreasing by 27.4% and 14.0%, respectively. Furthermore, V (R2 = 0.78) and φ (R2 = 0.73) presented the highest predictive accuracy for runoff rates, whereas V, τ, ω, and φ (R2 > 0.90) presented the highest predictive performance for soil erosion rates. Therefore, F. arundinacea (<6o slope gradient) and P. notatum (>6o slope gradient) are the most effective at controlling soil erosion.

Black soil with high fertility is a valuable soil resource, which plays an important role in guaranteeing regional food security and ecological security. Straw return is also a widely recognized way of straw resource utilization. However, it is still not clear which corn straw return method is more suitable for the Chinese black soil region with cold characteristics. The objectives of this study were to classify rainfall patterns (I—light rain with long duration, II—heavy rain with short duration, III—moderate rain with moderate duration; T1 and T2—special rains) and reveal the effects of furrow corn straw mulch—a new straw return—on soil erosion and organic carbon loss. Natural runoff plots (a planned size of 100 m2 and dimensions of 20 m × 5 m for each one) with or without the furrow corn straw mulch, which had slope gradients of 3°, 6° and 9°, were applied for natural rainfalls. Runoff and sediment samples were collected after each erosive rainfall to measure runoff, sediment, and organic carbon concentration. The results showed that when comparing treatments with the furrow corn straw mulch to control treatments, runoff coefficients, sediment concentration, and mean ratios of organic carbon loss in sediment to total carbon loss decreased by 48.0–97.7%, 45.6–99.7%, and 4.7–12.9%, respectively. Furthermore, the ratios of <0.053 mm sediment increased but the ratios of >0.25 mm sediment generally decreased. The mean organic carbon concentration both in runoff and sediment decreased in the following order: II > III > I > T1 > T2. Rainfall pattern II induced greater ratios of organic carbon loss. Therefore, the furrow corn straw mulch measure, which effectively decreased soil erosion and regulated organic carbon loss from the black soil, is suitable for the farmlands in the black soil regions.

土壤侵蚀与土壤物理特性、抗蚀性密切相关,研究放牧强度对荒漠草原地表土壤颗粒组成及其可蚀性的影响,可为阐明放牧强度与土壤可蚀性间的响应机制提供科学依据,并可为科学利用草地提供参考.文中以苏尼特右旗荒漠草原5种强度放牧小区为研究对象,运用野外调查取样与室内试验相结合的方法,测定不同放牧强度小区的土壤颗粒粒径体积分数及有机碳含量,计算土壤可蚀性K值,探究放牧强度对K值的影响影响.通过数据分析表明,各放牧小区土壤颗粒以砂粒为主,粉砂次之,黏粒最少;砂粒随放牧强度增大而减少;粉砂则相反.有机碳含量随放牧强度增大而先减后增.不同放牧强度小区土壤可蚀性K值主要集中在低可蚀性至中可蚀性,且K值与放牧强度、粉砂、黏粒体积分数呈正相关关系(P＜0.05);与砂粒体积分数、有机碳含量呈负相关关系(P＜0.05),相关性大小依次为:砂粒＞粉砂＞放牧强度＞粘粒＞有机碳;K值平均值与放牧强度Gi呈显著正相关关系,其关系可表达为K=0.01Gi +0.015,轻度放牧可减小土壤的可蚀性.

为探究印度梨形孢和高丹草在镉胁迫下的响应机制,以高粱与苏丹草杂交的一年生草本植物高丹草(Sorghum hybrid sudangrass)为实验材料,通过水培实验,研究不同浓度Cd胁迫(0、5、10、30、50、100mg/L)下接种印度梨形孢(Piriformospora irdica,简称P)对高丹草生长状况、光合参数、渗透调节物质和抗氧化酶活性的影响.结果表明:1)接种P菌能够促进高丹草生物量的积累,缓解叶片发黄现象,改善生长状况.2)接种P菌能有效降低镉对叶肉细胞的损害,改善高丹草的光合作用,提高净光合速率和蒸腾速率.3)接种P菌提高了高丹草在镉胁迫下的抗性生理指标.接菌提高了高丹草可溶性蛋白、可溶性糖含量以及酶活性,降低了丙二醛含量.综上,印度梨形孢能够有效降低镉对高丹草生长的抑制作用和毒性损伤.

为探究植物和微生物联合修复对镉(Cd)的作用效应,以一年生草本植物高丹草(Sorghum Hybrid Sudangrass)为试验材料,通过水培试验,研究印度梨形孢(Piriformospora indica)在不同浓度Cd胁迫(0、5、10、30、50、100 mg·L-1)下高丹草生长和生理特性,以及重金属Cd在高丹草植物体内转运、富集和分布特征.结果表明:在5 mg·L-1低Cd浓度下,高丹草株高、叶片数、生物量均有一定程度的增加;随着浓度的增加,高丹草株高、叶片数减少,生物量降低,黄叶数增加,生长受到抑制,接菌后能够促进高丹草生物量的积累,缓解叶片发黄现象,改善生长状况.接菌提高了高丹草在Cd胁迫下的抗性生理指标.随着浓度的增加,高丹草未接菌组的可溶性糖、可溶性蛋白、丙二醛、超氧化物歧化酶、过氧化氢酶活性总体上逐渐升高,过氧化物酶活性逐渐降低.接菌提高了可溶性蛋白、可溶性糖含量以及酶活性,降低了丙二醛含量.不同Cd浓度条件下,高丹草体内Cd含量呈根>叶>茎的分布,且含量随着浓度增加而增加,接菌后高丹草地下部Cd含量增加,地上部Cd含量降低,接菌减少了Cd从地下部向地上部的转移,减轻了Cd对高丹草地上部的毒害.研究表明印度梨形孢能有效降低Cd对高丹草生长的抑制作用和毒性损伤.

为探究液态环保抑尘剂对生产建设项目内临时堆土坡面水土流失防治效益,为抑尘剂生产实践应用提供科学依据,也为临时堆土水土流失防治提供新的思路与材料.采用人工模拟降雨试验,研究临时堆土常见坡度(20°、30°),"尘克"液态环保抑尘剂不同喷施浓度(0、1/100、1/75、1/50)下坡面产流产沙过程.结果表明:施加抑尘剂后具有明显的减沙作用(9.24％-76.33％),但增强了坡面径流(7.41％-30.19％).相较于坡度,抑尘剂浓度是影响临时堆土产流、产沙速率的首要因素.抑尘剂浓度显著影响降低初始产流时间、产沙速率、产沙量,显著增强流速、产流速率、产流量.在三种抑尘剂浓度配比中,1/75配比抑尘剂能显著降低坡面侵蚀程度,是临时堆土坡面水土流失防治的最优化配比.

为定量评估放牧对草原土壤入渗的影响,了解和防治放牧造成的水土流失,科学评估草原水文调节功能,采用双环入渗法研究了放牧对典型草原土壤入渗性能的影响,并收集影响土壤入渗的环境特征变量.结果表明:(1)土壤入渗能力均受到放牧活动的干扰,随着放牧强度的增加,土壤初渗速率、稳渗速率减小,达到稳渗时的历时缩短,而轻度放牧对土壤入渗性能却具有增强作用,LG的初渗速率(5.12 mm/min)、稳渗速率(1.93 mm/min)、2 h累积入渗量(213.42 mm)均较好,快速入渗至稳渗阶段历时延长.(2)不同放牧强度下,放牧强度与土壤初渗速率、稳渗速率、累积入渗量呈显著负相关关系,相关系数分别为-0.646,-0.770,-0.531.植被盖度、砂粒体积百分数、孔隙度均与土壤入渗速率呈正相关关系,而土壤容重则相反.土壤容重、总孔隙度、毛管孔隙度对土壤入渗速率的影响最为显著.适度放牧(LG,1.5羊/(hm2·月))会改善土壤特征参数及植被生长情况,提高土壤的入渗性能.(3)通过土壤入渗模型分析,Horton模型对土壤入渗速率及土壤累积入渗的拟合效果均表现为最好.研究结果可为放牧条件下典型草原的土壤入渗及水文调节功能的定量评估提供参考.

揭示风沙土复配其他固沙材料后的土壤质量变化及改良效应对研发防沙固沙新材料具有重要的指导意义.以乌兰布和沙漠风沙土为对照(CK),采用粉煤灰、脱硫石膏、牛粪3种固沙材料按干质量比15％,25％与风沙土进行复配,研究了不同材料与配比复配土壤对机械组成、养分含量、金属含量的改良效应,运用最小数据集构建、隶属度计算与土壤质量指数计算等方法评价了复配土壤质量.结果表明:(1)不同复配土壤的机械组成均发生了改变,粉粒、粗砂等难蚀、较难蚀颗粒体积分数增加,易蚀的细砂体积分数降低.(2)除石膏复配土壤各养分指标与CK相近外,其余复配土壤有机碳含量较对照提高1.2～10.4倍,牛粪复配土壤在提高养分含量方面显著高于其他材料;以牛粪和石膏为材料的复配土则分别增加或降低了沙土中的金属含量,而粉煤灰复配土的Cr,As较CK下降.(3)不同复配土对土壤理化性质作用影响各异,粉煤灰在粒径改良方面较优,牛粪在养分提升方面效果显著,石膏在重金属含量降低方面作用明显,粉煤灰石膏混合复配则综合了二者的优势.(4)3种固沙材料均在不同程度上提高了复配土壤的质量,但复配土壤质量仍处于较低水平.综上,不同复配比例组合中,15％粉煤灰复配土壤质量得分指数最高为0.545,对风沙土的改良效果最好,其次为15％脱硫石膏(0.537),15％牛粪(0.506)和25％粉煤灰与脱硫石膏(0.484)复配组合.

为了解不同放牧强度对内蒙古放牧草原植物群落特征及土壤有机碳的影响,本研究以希拉穆仁草原为研究对象,分析不同放牧强度下植物群落特征及0～20 cm土壤有机碳含量和密度变化,定量评估放牧、植物群落特征对土壤有机碳的影响.结果表明:随着放牧强度的增强,克氏针茅(Stipa krylovii)、阿尔泰狗娃花(Heteropappus altaicus)的重要值降低,银灰旋花(Convolvulus Ammannii)、羊草(Leymus chinensis)和冰草(Agropyron cristatum)的重要值提升,物种多样性指数均呈增长趋势,且在重度放牧强度下差异显著,但覆盖度和地上生物量显著降低;土壤有机碳含量在5～10 cm土壤层最高,重度放牧草场土壤有机碳密度显著高于轻度、中度放牧草场和禁牧草场.通过结构方程得出,对于干旱贫瘠的希拉穆仁草原,放牧造成地上生物量的减少对土壤有机碳密度的影响相对较小,土壤物理性质显著影响土壤有机碳密度.本研究结果对合理增强放牧草原的碳汇能力具有实际指导意义.

为揭示牧草种植改良盐碱地的效果,更好地开发利用后备土地资源.以黄河三角洲滨海盐碱地为研究对象,采用小区试验、野外取样、室内测试相结合的方法,研究了高丹草、甜高粱和墨西哥玉米3种一年生牧草在1个生长期内对黄河三角洲盐碱地土壤物理、化学和酶活性改良效果的动态变化,并依据土壤质量指数综合评价了改良效果.结果表明:(1)土壤含水量、pH和电导率随生长时间增加呈下降趋势,高丹草和墨西哥玉米在生长旺盛期对土壤pH的降低效果最明显,甜高粱在收获期降低pH的效果最好.3种牧草土壤电导率较CK均显著降低,对20-40 cm 土层的降低效果优于0-20 cm 土层,其中墨西哥玉米效果最好.(2)种植不同牧草对土壤养分含量有明显改善,其中土壤有机质、速效氮、速效磷含量有显著提升,但对土壤速效钾含量影响不大.(3)3种牧草在不同生长期内对土壤酶活性的影响不同,在生长旺盛期土壤酶活性最强,均显著增强土壤过氧化氢酶、蔗糖酶和脲酶的活性,其中甜高粱对过氧化氢酶和蔗糖酶活性影响最大.(4)不同牧草对盐碱土壤改良指标的贡献值存在差异,综合土壤理化性质、养分含量和土壤酶活性作为土壤评价指标,种植不同牧草后土壤质量从高到低依次为甜高粱＞高丹草＞墨西哥玉米＞CK.研究结果可为黄河三角洲地区盐碱地的植物修复技术和筛选及引进国内外具有高效生态经济效益的耐盐植物提供理论依据和重要参考.

内蒙古荒漠草原由于地表植被覆盖度低,土壤颗粒分散,极易发生土壤风蚀现象.土壤水分能够增强土壤抗侵蚀能力,但其影响程度目前尚不明确.基于此,文中以内蒙古苏尼特右旗选择短花针茅(Stipa breviflora Griseb.)荒漠草原原状土为研究对象,根据研究区风季的风速数据及测定的土壤质量含水量情况,设置1.5％、2.5％、3.5％三个水分梯度与10、13、17m/s三个风速梯度,开展了不同土壤含水量条件下的土壤起动风速,不同土壤含水量及风速交互作用下的土壤风蚀率、风沙流垂直分布的风洞模拟试验,以探究土壤含水量、风速及其交互作用对土壤风蚀特征的影响.结果表明:1)土壤含水量的增加能够增大起动风速,从而提高土壤抗风蚀能力,土壤含水量对风蚀率的作用随着风速的增大逐渐减小.2)低风速下土壤含水量的增加显著降低土壤风沙流沙物质含量,随着风速的增加,近地表风蚀输沙量比例逐渐升高.3)含水量通过与风速的交互作用起到降低风蚀的作用,但影响程度较低,研究区土壤含水量条件下的风速影响阈值为13m/s,风速超过13m/s,土壤含水量对于风蚀率的影响不明显.因此,风速是研究区土壤风蚀的主导因素,但在一定的风速范围内适当增加土壤含水量能够有效减少苏尼特右旗荒漠草原土壤风蚀.

植物群落是维持草原稳定和提供生态系统服务的关键要素.为探究放牧对希拉穆仁草原植物群落及种间联结的影响,文中以禁牧草场、轻度放牧草场、中度放牧草场、重度放牧草场为研究样地,系统调查分析了植物群落组成、物种多样性、物种生态位及种间联结性,并进一步探究其相互关系及土壤肥力的影响.结果表明:除重度放牧草场外,其余放牧强度草场的植物群落均以糙隐子草(Cleistogenes squarrosa)、阿尔泰狗娃花(Heteropappus altaicus)、克氏针茅(Stipa krylovii)为优势种,但放牧改变了物种的相对重要值.重度放牧草场以糙隐子草、羊草(Leymus chinensis)、银灰旋花(Convolvulus Ammannii)、冰草(Agropyron cristatum)为优势种.重度放牧显著增加了群落物种的多样性,但增加的物种重要值普遍较小,且地上生物量显著降低.放牧强度的增强降低了原始优势种的生态位宽度,禁牧草场和重度放牧草场种间联结总体呈显著负联结,轻度放牧草场和中度放牧草场呈显著正联结.随放牧强度的增强种间联结指数逐渐升高,群落内物种间联系紧密,重度放牧草场存在较多种间竞争.土壤C:P比值与Pielou均匀度指数显著正相关,土壤磷含量影响希拉穆仁草原植物群落分布.

为明确黄泛沙地不同林龄杨树人工林对土壤团聚体及有机碳的影响,以山东省国有东明林场3 a,5 a,8 a,10 a生杨树人工林土壤为研究对象,采用野外取样、室内试验与湿筛法分析了土壤团聚体组成与稳定性,并分析土壤有机碳含量与储量的变化特征.结果表明:(1)不同林龄杨树人工林团聚体分布均以大团聚体(>0.25 mm)为主,在表层土层(0—20 cm)中,随林龄的增加,大团聚体含量呈先显著降低后增加再略减的趋势;而在20—40 cm土层中,土壤大团聚体含量为5 a>8 a>3 a>10 a;在40—60 cm土层无显著差异;(2)在0—20 cm土层中,有机碳含量表现为3 a>5 a>10 a>8 a;在20—60 cm土层,呈先增后减的趋势,且无显著差异.土壤稳定性与团聚体的形成和有机碳密切相关,有机碳含量与GMD值呈极显著正相关关系;(3)不同林龄杨树人工林有机碳储量均呈现一定程度表聚性,在0—20 cm各林龄碳储量占总碳储量的59.17％～74.26％.在3 a到5 a阶段由于土壤淋溶作用,可能导致有机碳储量发生转移,从表层土层(0—20 cm)向底层土层(20—60 cm)转移,而在8 a到10 a阶段,有机碳储量从底层土层向表层土层发生转移.研究结果为揭示黄泛沙地杨树人工林土壤团聚结构形成与有机碳提升提供了参考.

It remains unclear how long-term and different intensities of grazing affect the soil infiltration process, total nitrogen (TN), organic carbon (SOC), and grain size of desert steppes of Inner Mongolia, China. We quantified the effects of consecutive years of grazing from 2004 to 2018 on the soil particle size distribution (PSD, using the American soil classification system), mean soil infiltration rate (r), and cumulative infiltration volume (VC), in addition to the contents of SOC and TN, and their ratio (C/N). We defined grazing intensity at four levels, as non-grazed enclosure (NG, 0-), light (LG, 0.15-), moderate (MG, 0.30-), and heavy grazing (HG, 0.45 sheep per month per hectare steppe). The annual grazing period lasted from May to November. We established twelve adjacent experimental plots containing three replications for each grazing intensity. In July 2018, we collected 600 soil samples (0-40 cm soil depth: 4 depths with a 10-cm interval) in the plots (50 per plot) in a sigmoid configu-ration, to determine the PSD, SOC, TN, and C/N. Grazing evidently changed the PSD in diameter ranges of 20-150 (fine particles) and 200-500 mu m (coarse particles). Grazing significantly decreased the uniformity and distribution range of PSD but increased its dispersion, and these changes were most pronounced in the topsoil (0-10 cm depth). LG promoted r and VC, whose augmentation was evident within the initial 10 min of the infiltration process. The Kostiakov infiltration model was better at dynamically and quantitatively fitting the changing process of r than either the Horton or Philip model. Compared with NG, LG and MG significantly increased both SOC and TN (p < 0.01) whereas these were significantly decreased under HG (p < 0.01). Across differing grazing intensities, topsoil SOC contents can be well predicted by the range and heterogeneity of PSD, as well as the fraction of fine soil particles. These results are helpful for better understanding how continuous grazing impacts soil characteristics and for specifically enacting reasonable grazing scenarios to mitigate desertification on vulnerable desert steppes.

Soil organic carbon (SOC) pool within different agroforestry systems is less documented. This study therefore investigated the relationships between soil parameters, concentrations of SOC pools, and soil erodibility under four agroforestry systems (Chinese ash (Fraxinus chinensis Roxb) forestland (CK), Chinese ash forestland and soybean (Glycine max (Linn.) Merr.) farmland (AS), Chinese ash forestland and peanut (Arachis hypogaea Linn.) farmland (AP), and Chinese ash forestland and chrysanthemum (Arachis hypogaea Linn.) farmland (AC)) in Yellow River Flood Plain in China. Among the compared agroforestry systems, AS had the highest easily oxidizable carbon (1.69 g kg−1), particulate organic carbon (1.60 g kg−1), dissolved organic carbon (30.23 g kg−1) and microbial biomass carbon (17.71 g kg−1), AC had the lowest (1.09 g kg−1, 0.82 g kg−1, 22.29 g kg−1, and 12.34 g kg−1, respectively). The non-easily oxidizable carbon (NOC) and mineral-associated organic carbon of AS (respectively, 5.71 g kg−1 and 5.96 g kg−1) were the greatest, whereas both were far lower under AC (respectively, 2.40 g kg−1 and 2.48 g kg−1). The ranking for soil carbon fractions concentrations was AS > CK > AP > AC. Structural equation modeling analysis revealed that soil capillary porosity and the active SOC pool (Ca) had positive effects on soil erodibility factor (K) (standardized coefficient = 0.27 and 0.33, respectively), while pH, the ratio of carbon to nitrogen (C/N), and the resistant SOC pool (Cr) each negatively affected K (standardized coefficient = − 0.46, − 0.33 and − 0.59, respectively). Further, the redundancy analysis results supported a decisive role for soil parameters and carbon fractions in determining soil erodibility. The result of this study implies that agroforestry can strengthen soil erodibility resistance. Altogether, these findings suggest the effects of the resistant SOC pool warrants explicit consideration when studying the dynamics of soil erosion resistance.

放牧是草原生态系统退化的重要驱动力,为揭示放牧强度对荒漠草原土壤理化性质的影响,本文以四子王旗重度(HG)、中度(MG)、轻度(LG)和封育禁牧(CK)4种放牧强度下短花针茅荒漠草原0～ 40cm土壤为研究对象,探讨土壤多重分形特征及理化性质对放牧强度的响应.结果 表明:4种放牧处理不同土层多重分形谱图并不完全重合,0 ～ 10 cm土层颗粒细化及分散程度(谱形)除CK外均正响应于放牧强度变化;土壤颗粒分布范围(谱宽)表现为MG＞LG＞HG＞CK,各土层粒径分布谱形最大的土层并不严格对应于谱宽最广的土层;放牧强度间不同土层容重及含水量的变化均呈HG＞ MG＞ LG＞ CK(P ＜0.05),而孔隙度变化则与之相反;不同放牧处理的w(有机C)、w(速效N)、w(速效P)变化规律相同,均呈LG最大,HG最小,且均随土层深度的增加而降低.土壤理化性质均在LG时有所提升,轻度放牧有助于遏制荒漠草原的土壤退化.

Remote sensing phenology retrieval can remedy the deficiencies in field investigations and has the advantage of catching the continuous characteristics of phenology on a large scale. However, there are some discrepancies in the results of remote sensing phenological metrics derived from different vegetation indices based on different extraction algorithms, and there are few studies that evaluate the impact of different vegetation indices on phenological metrics extraction. In this study, three satellite-derived vegetation indices (enhanced vegetation index, EVI; normalized difference vegetation index, NDVI; and normalized difference phenology index, NDPI; calculated using surface reflectance data from MOD09A1) and two algorithms were used to detect the start and end of growing season (SOS and EOS, respectively) in the Tibetan Plateau (TP). Then, the retrieved SOS and EOS were evaluated from different aspects. Results showed that the missing rates of both SOS and EOS based on the Seasonal Trend Decomposition by LOESS (STL) trendline crossing method were higher than those based on the seasonal amplitude method (SA), and the missing rate varied using different vegetation indices among different vegetation types. Also, the temporal and spatial stabilities of phenological metrics based on SA using EVI or NDPI were more stable than those from others. The accuracy assessment based on ground observations showed that phenological metrics based on SA had better agreements with ground observations than those based on STL, and EVI or NDVI may be more appropriate for monitoring SOS than NDPI in the TP, while EOS from NDPI had better agreements with ground-observed EOS. Besides, the phenological metrics over the complex terrain also presented worse performances than those over the flat terrain. Our findings suggest that previous results of inter-annual variability of phenology from a single data or method should be treated with caution.

探究放牧强度对草原土壤物理特性尤其土壤粒度特征的影响,有助于了解和防治草原水土流失,科学管理草原生态系统.文中以希拉穆仁典型草原为主要对象,研究放牧对不同深度土壤粒径的组成特征及单重分形维数的影响和交互关系.研究表明:放牧强度的增加对土壤质地有恶化趋势,土壤粒径逐渐变粗,土壤类型由砂质壤土向壤质砂土转变.放牧主要影响0～10cm土层,尤其在0～5cm土层,土壤粒度特征值与单重分形维数值均随放牧强度增加而逐渐恶化;5～10cm土层,适度放牧使土壤粒度特征值、单重分形维数值均表现最好.轻度放牧对表层土壤粒度特征及单重分形维数的影响最小,采取轻度放牧可较好地权衡草地的生态与生产功能.

探究水流驱动下土壤剥蚀特征对阐明土壤侵蚀机制和规避水土流失风险具有重要意义.通过野外放水冲刷试验,以砒砂岩区灌丛分别位于坡下(SL)、坡中(SM)、坡上(SU)的灌草坡面和草地坡面(GL)为对象,裸坡(BL)作为对照,探讨了该区坡面土壤剥蚀和水动力参数对不同灌草格局的响应特征及其相互关系,结果表明:(1)不同灌草格局可以通过削弱径流过程中的水流动能来降低坡面土壤的剥蚀程度,砒砂岩区坡面土壤剥蚀率整体介于0.055～0.469 g/(m2·s),其中SL格局土壤剥蚀率最低[均值0.098 g/(m2·s)],是降低土壤剥蚀程度的最佳植被布设措施.(2)不同格局土壤剥蚀率、水流功率及单位水流功率整体呈现出BL>GL>SU>SM>SL的趋势,水动力参数中水流功率与土壤剥蚀率的拟合效果最优,可以较好地描述该区坡面土壤剥蚀特征.研究可为砒砂岩区土壤侵蚀预测模型的构建提供科学依据.

The characteristics of soil holding capacity for different shrub-grass patterns are important to research the mechanisms regulating vegetation on slopes. The objective of this study was to describe the characteristics and mechanisms of soil erosion and hydraulic parameters under different vegetation patterns in the Pisha sandstone area of Inner Mongolia on lands of 8° slope gradient. We carried out field scouring experiments on five different shrub-grass patterns as treatments, viz no shrubs (GL), shrubs on the upper part of the slope (SU), middle part of the slope (SM) and lower part of the slope (SL). We designated bare slope (BL) as the control. We employed three different water flow rates (15, 20, 30 L·min −1 ). Our results showed that the contribution of plant root systems to slope sediment reduction ranged from 64 to 84%. The root systems proved to be the main contributing factor to reduction of erosion by vegetation. The relationship between soil detachment rate, stream flow power, and flow unit stream power under different scouring discharge rates showed that soil detachment declined in rank order as: BL > GL > SU > SM > SL. The SL pattern had the lowest soil detachment rate (0.098 g·m −2 ·s −1 ), flow stream power (2.371 W·m −2 ), flow unit stream power (0.165 m·s −1 ) and flow shear stress (16.986 Pa), and proved to be the best erosion combating pattern. The results of decision coefficient and path analysis showed that stream power was the most important hydraulic parameter for describing soil detachment rate. The combination of stream power and shear stress, namely Dr = 0.1 ω − 0.03 τ − 0.56 (R 2 = 0.924), most accurately simulated the soil detachment characteristics on slopes. Our study suggests that the risk of soil erosion can be reduced by planting shrub-grass mixes on these slopes. Under the conditions of limited water resources and economy, the benefit of sediment reduction can be maximized by planting shrubbery on the lower parts of slopes.