Mechanism of formation of sliding ground fissure in loess hilly areas caused by underground mining

Based on a shallow-buried coal seam covered with thick loose layers in hilly loess areas of western China,we developed a mechanical model for a mining slope with slope stability analysis, and studied the mechanism of formation and development of a sliding ground fissure by the circular sliding slice method.Moreover, we established a prediction model of a sliding fissure based on a mechanical mechanism,and verified its reliability on face 52,304, an engineering example, situated at Daliuta coal mine of Shendong mining area in western China. The results show that the stress state of a mining slope is changed by its gravity and additional stress from the shallow-buried coal seam and gully terrain. The mining slope is found to be most unstable when the ratio of the down-sliding to anti-sliding force is the maximum, causing local fractures and sliding fissures. The predicted angles for the sliding fissure of face 52,304 on both sides of the slope are found to be 64.2° and 82.4°, which are in agreement with the experimental data.

Impacts of Sloping Land Conversion Program on the vegetation in loess hilly and gully area of northern Shaanxi

Aiming at alleviating the serious soil erosion, the Chinese government initiated the Sloping Land Conversion Program （SLCP） in 1999. Now; after 8 years of project implementation, the ecological recovery effects of the SLCP have become the hot issue of academic circle. This paper; raking the loess hill and gully area of northern Shaanxi as an example, presents a methodology for assessing the vegetation restoration effect of SLCP with normalized difference vegetation index （NDVI）. The key components include calculation of the Growing Season NDVI （GSNDVI）, and estimation of the NVDI change induced by climate and SLCP, respectively. Based on the method, the NDVI change between 2000 and 2006 was obtained using the GSNDVI that excluded the noise from snow and ice. After the part of total NDVI change caused to： climate variation was estimated using empiric formulae, we obtained the part induced by human factors, i.e. the SLCP The human induced part of ND VI change was considered as an approximation indicating the effect of the SLCP on the vegetation. Finally, we analyzed the ND VI change characters of the whole study area, different slope lands and different land use types by spatial statistics method. Results show that the vegetation condition is significantly improved by the SLCP, particularly land types that directly involved in the SLCP, such as steeply slope farmlands, degraded grasslands, etc.

The effects of land use and its patterns on soil properties in a small catchment of the Loess Plateau

Due to relatively strong human activities in the hilly area of Loess Plateau, the natural vegetation has been destroyed, and landscape pattern based on agricultural land matrix was land use mosaic composing of shrub land, grassland, woodland and orchard. This pattern has an important effect on soil moisture and soil nutrients. The Danangou catchment, a typical small catchment, was selected to study the effects of land use and its patterns on soil moisture and nutrients in this paper. The results are as follows: The comparisons of soil moisture among seven land uses for wet year and dry year were performed: (1) the average of soil moisture content for whole catchment was 12.11% in wet year, while it was 9.37% in dry year; (2) soil moisture among seven land uses was significantly different in dry year, but not in wet year; (3) from wet year to dry year, the profile type of soil moisture changed from decreasing type to fluctuation-type and from fluctuant type to increasing type; (4) the increasing trend in soil moisture from the top to foot of hillslope occurred in simple land use along slope, while complicated distribution of soil moisture was observed in multiple land uses along slope. The relationships between soil nutrients and land uses and landscape positions were analysed: (1) five nutrient contents of soil organic matter (SOM), total N (TN), available N (AN), total P (TP) and available P (AP) in hilly area were lower than that in other areas. SOM content was less than 1%, TN content less than 0.07%, and TP content between 0.05% and 0.06%; (2) SOM and TN contents in woodland, shrub land and grassland were significantly higher than that in fallow land and cropland, and higher level in soil fertility was found in crop-fruit intercropping land among croplands; (3) soil nutrient distribution and responses to landscape positions were variable depending on slope and the location of land use types.

An applied research on remote sensing classification in the Loess Plateau

Dae to complex terrain of the Loess Plateau, the classification accuracy is unsatisfactory when a single supervised classification is used in die remote sensing investigation of the sloping field. Taking the loess hill and gully area of northern Shaanxi Province as a test area, a research was conducted to extract sloping field and other land use categories by applying an integrated classification. Based on an integration of supervised classification aad unsupervised classification, sampling method is remarkably unproved. The results show that the classification accuracy is satisfactory by the method and is of critical significance in obtaining up-to-date information of the sloping field, which should be helpful in the state key project of converting farmland to forest and grassland on slope land in this area. This research sought to improve the application accuracy of image classification in complex terrain areas.

水足迹视角下黄土丘陵区农业水土资源匹配格局——以山西省和顺县为例

从水足迹视角出发,运用CROPWAT及标准差椭圆模型分析2010—2019年山西省和顺县乡镇域主要农作物生产水足迹和耕地面积的时空变化,运用基尼系数及空间失配指数深入研究2010年、2014年、2019年乡镇域农业水土资源时空匹配格局,并明确调控方向。结果表明,研究期间,和顺县作物生产水足迹、蓝水足迹、绿水足迹和耕地面积总体上均呈下降趋势;绿水足迹对各区域作物生产水足迹的构成贡献最大,占比均超过62.0%;和顺县西部地区作物生产水足迹和耕地的空间聚集性不断增强;和顺县作物生产水足迹、蓝水足迹、绿水足迹与耕地之间的空间失配均逐渐加剧,中部和东部地区农业水土资源分别为中度失配和重度失配,是和顺县未来农业水土资源调控的重点地区;可以将县域10个乡镇分别划分为水源涵养调蓄、水土优化调控与引水节水灌溉3个调控区。总的来说,受社会经济、生产要素投入和气候条件的影响,和顺县农业水土资源匹配协调水平处于失衡状态,但在调控区划分的基础上,有针对性地进行人工调控,仍可实现农业水土资源匹配协调水平的较大提升。

The effect of land use structure on the distribution of soil nutrients in the hilly area of the Loess Plateau,China

The irrational land use is one of the main reasons for the soil erosion and nutrient loss in the loess hilly area of China. In this project, 4 types of typical land use structure of sustain ment for about 15 years in the loess hill slope are selected to study the effect of land use structure on the distribution of soil nutrients. From hill bottom to hill top, the patterns of land use types are:, grassland-slope farmland-forest, slope farmland-grassland-forest, terrace-grassland-forest and slope farmland-forest-grassland. By measuring the contents of the total N, total P, available N, available P and organic matter of soils, the results show that the land use structure types of slope farmland-grassland-forest and terrace-grassland-forest have a better capacity to maintain the soil nutrients.

黄土丘陵区农村空心化演化机理研究——基于人口迁移理论视角

农村聚落空心化是在快速工业化、城镇化进程中农村宅基地出现规模化闲置废弃的现象,是全面实施乡村振兴战略亟待破解的难题。该文基于人口迁移视角,从城市吸引力、农户迁移意愿、宏观政策环境3个维度构建农村人口迁移的理论框架,解析人口迁移对农村空心化的作用机制,并通过构建农村空心化指数定量剖析黄土丘陵区案例村(D村)空心化演进规律与驱动机理。研究表明:①随着宏观经济发展与政策环境变化,D村聚落空间经历了居民点内部迁移、村庄快速扩张、新村旧村分化、闲置宅基地盘活4个阶段,对应聚落空心化出现期、发展期、兴盛期、稳定期。②D村空心化是在人口迁移这一核心因素驱动下,由聚落内部迁移演替与农村人口流失两方面因素共同作用的结果。从时序上看,村落空心化初期主要受住宅更新的显性作用影响,表现为宅基地成片空心化;在建房需求饱和后显性作用逐渐弱化,以人口持续流失造成的隐性作用成为空心化的主导因素,空心化程度逐渐加剧。③受乡村发展内能与外部支持条件的影响,农村空心化可能出现再实心化、稳态的空心化、发展的空心化等差异化趋势,可通过制度改革、基本投资、发展产业等手段调控空心化进程与演化方向。

Structure and governance model of rural social space quality:A case study of Longxi County in the Loess Hilly Area of China

The rural social space quality is an important indicator to measure the living standard and thinking ideas and so forth of rural residents in a certain region.In this paper,213 administrative villages in Longxi County of the Loess Hilly Area,China are taken as evaluation units to construct the evaluation model of the rural social space quality.This paper deeply analyzed the variation patterns and their formation mechanism of the rural social space quality at a village scale,and proposed a governance model based on the rural social space quality.The results show that:(1)the social space quality levels of individual administrative villages show a gradually decreasing trend from the township seats to outward.The eastern part of Longxi County has a relatively high education level and living standard,and the western part has a relatively high population stability level and income level.(2)The rural social space quality is mainly in a ring structure,supplemented by the interlaced structure.The core area is the towns and their surrounding areas,while the transition area,marginal area,and other areas are expanded around the core area.(3)Social forces and spatial effects jointly shape the variation of the rural social space quality.Social organizations provide a driving force for the allocation of elements,and interweaving with the spatial effects lead to the differences in the social space quality.(4)The governance models of the rural social space quality are constructed based on the principles of retaining the rural“people”,optimizing the rural“land”,and developing the rural“industry”,so as to improve the rural centripetal force,core force,inner thrust,and source power.

黄土高原丘陵沟壑区玉米新品种引种比较综合评价

通过研究不同玉米品种在黄土高原丘陵沟壑区的稳产性及丰产性,以期为该区玉米新品种的筛选及推广提供科学依据。以引进10个玉米品种为试材,对参试各玉米品种的农艺性状、产量及产量特征等指标进行综合分析评价。结果表明,强盛399、伊丹131、金穗1915折合产量高,分别为11850.1、11605.0、11411.9 kg/hm2,较对照品种金穗702分别增产14.54%、12.17%、10.30%;并单39、丰田101、敦玉9号折合产量较低,分别较对照品种金穗702减产3.76%、10.86%、30.76%。利用综合评价法对参试玉米品种进行综合评价并结合产量结果表明,强盛399、金穗306、伊丹131、金穗702表现出良好的丰产性与稳产性,同时表现出静态稳定性高、品质优异、生态适应性强的特点,是适用于黄土高原丘陵沟壑区种植的玉米新品种,建议予以推广。金穗1915、FT806、强盛388综合评价居中,建议继续引种观察。敦玉9号、丰田101、并单39号综合评价较差,建议淘汰。

黄土丘陵沟壑区挖填造地工程勘察的探索与实践

黄土丘陵沟壑区挖填造地工程会遇到众多岩土工程问题。为保证类似工程建设的安全,避免相关工程事故的发生,依托某黄土丘陵沟壑区挖填造地工程实践,归纳了挖填造地工程前原场地勘察要点、研究方法和评价思路,分析了黄土丘陵沟壑区挖填造地工程面临的主要工程地质问题,并给出了建议措施。结果表明:填方区勘察重点为湿陷性黄土和其它覆盖土层的分布以及在高压力条件下工程性质,挖方区勘察重点为土石材料工程性质和土石比;主要工程地质问题涉及地下水环境变化及其对工程的影响、高填方场地沉降与不均匀沉降、填挖边坡稳定性、湿陷性黄土地基增湿变形、软弱淤积土地基问题、不良地质作用等。

不同土地利用类型对豫西黄土丘陵区坡面产流产沙的影响

[目的]分析豫西黄土丘陵区不同土地利用类型及不同坡度条件下土壤侵蚀产流产沙规律,为土壤侵蚀定量评价、水土流失综合防治提供科学依据。[方法]基于河南省嵩县胡沟小流域水土保持监测点2011—2020年12个坡面径流小区观测数据,揭示了不同土地利用类型下产流产沙规律,采用相关分析研究了降雨特征、坡度、土地利用与产流产沙的关系。[结果](1)与裸地小区相比,草地小区的减流减沙效益最大。草地的多年平均减流效益变化为78.6%~85.9%,减沙效益最高可达100%。林地的减流效益为32.9%~51.3%,减沙效益为55.3%~78.9%。(2)各径流小区产流产沙次数、大小与坡度关系密切,10°与15°的产流产沙差别不大,25°的坡度上产流产沙明显增加。此外,随着坡度的增加,林草地的水土保持效益也在降低。(3)径流小区径流深与最大30 min雨强(I_(30))、土壤流失量与降雨侵蚀力相关性最为显著。[结论]在豫西黄土丘陵区缺少径流泥沙定位观测的区域,一定的坡度和植被状况下,可用降雨过程资料来估测坡面径流量和土壤流失量。

山西黄土丘陵区荒山造林技术研究

为了改善山西省生态环境,实施对黄土丘陵区生态系统的全方位改造,加强荒山造林技术应用,攻克黄土丘陵区造林难题,对山西省黄土丘陵区荒山造林工作开展状况进行研究、整理和分析,阐述了山西省黄土丘陵区荒山造林面临的现实困境,从前期规划、整地、造林、抚育管理、日常养护等多个环节提出黄土丘陵区荒山造林技术应用优化策略,以重塑黄土丘陵区绿色生态,推动绿色发展战略目标实现,为相关工作人员提供理论参考。

半干旱黄土丘陵区典型植被土壤养分含量及其分布特征

以甘肃定西龙滩流域8种典型植被为研究对象,对其3个土层深度的土壤有机质、全氮、全磷、全钾、碱解氮、速效磷、速效钾和pH值进行测定,探讨植被与土壤养分间的关系。结果表明:植被类型主要影响土壤全磷、全钾和速效钾含量及分布,且不同植被间差异显著(p<0.05);土层深度主要影响土壤有机质、全氮、碱解氮和速效钾的含量及分布,而且在不同土层间差异显著(p<0.05)。不同植被间土壤养分分布规律不明显,但不同土层间土壤养分表层聚集效应明显,总体上随土层深度的增加而不断下降。在不同植被和不同土层下土壤养分变异性差异很大,其变异系数由大到小依次为速效磷(>45%)>有机质、全氮、碱解氮(>30%)>速效钾(>15%)>全磷、全钾(<4%)>pH值(<2%)。相关分析表明,pH值与土壤有机质、全氮、碱解氮呈极显著负相关关系(p<0.01),而有机质、全氮、碱解氮相互间呈极显著正相关关系(p<0.01)。在半干旱黄土丘陵区,植被类型和土层深度对土壤pH值和土壤养分含量及分布均有影响,但不同植被对各养分的影响效果并不一样;在今后植被恢复中,应多采用草灌林结合来建人工植被,以使黄土丘陵区复杂多样的土壤生态系统得到健康、持久的发展。

黄土丘陵区植被类型对土壤微生物量碳氮磷的影响

选择黄土丘陵区延河流域4种典型植被类型下的土壤为研究对象,测定了土壤微生物量碳、氮、磷和相关基本理化性质。结果表明,在此流域的典型天然草地、人工灌木林、人工乔木林和农地中土壤微生物量碳(MBC)的含量范围分别为315.15—400.89、246.56—321.25、267.76—347.05和118.96—245.14 mg/kg,土壤微生物量氮(MBN)的含量范围分别为35.87—47.63、27.63—42.89、24.66—36.20和15.64—22.56 mg/kg,土壤微生物量磷(MBP)的含量范围分别为14.14—22.96、12.89—19.75、11.54—14.40和7.23—11.59 mg/kg;土壤微生物量总体呈现出天然草地最高、人工乔、灌木林次之,且均显著高于农地的趋势,表明退耕还林还草对土壤微生物生物量有明显的促进作用。不同植被类型下,土壤微生物量碳氮比和碳磷比的变化范围分别为7.49—10.87和16.27—24.11,土壤微生物量碳、氮、磷占土壤有机碳(SOC)、全氮(TN)、全磷(TP)百分比的范围分别为2.70%—4.85%、2.56%—4.45%、2.08%—5.34%。其中天然草地、人工灌木林和农地土壤的微生物量碳氮比、碳磷比均显著小于人工乔木林(P<0.05);MBC/SOC在不同植被类型下的差异不显著,MBN/TN和MBP/TP均呈现出天然草地>人工灌木林>人工乔木林和农地的趋势,且差异显著(P<0.05)。微生物量碳、氮、磷与土壤有机碳、全氮和土壤含水率呈现极显著或显著相关性,与土壤pH值呈现出不同程度的负相关性,表明植被类型对这些与土壤微生物量紧密相关的理化性质也有显著影响。

黄土丘陵区小流域植被建设的土壤水文效应

以纸坊沟流域为研究对象,研究了植被恢复后不同植被对土壤水分的影响情况,得出如下结论:①草地土壤水分含量大于灌木林地,灌木林地土壤水分含量大于乔木林地;②选用乡土树种油松造林对土壤的干化程度较轻,选用刺槐造林时要考虑立地条件和造林密度,林草隔带种植可以减轻土壤干化程度;③灌木林下阴坡土壤干层并不比阳坡干层程度轻。土壤干化程度和植被种类直接相关。此外,受种植密度及人为干扰影响;④和以前人们的认识不同,天然草本植被也会形成土壤干层,其中白羊草和长芒草形成有利于自身群落稳定的干层,但茭蒿形成的干层则对自身稳定不利,在植被建设上应引起足够重视。

黄土丘陵区小流域植被恢复的土壤养分效应研究

研究了安家坡小流域荒草地、山杏林地、农地、油松林地、灌木林地、弃耕地等地类的土壤养分特征。结果表明,植被系统具有较强的养分表层富集功能;不同植被恢复类型对土壤养分含量有明显的影响,主要表现在不同土层土壤有机质、速效磷、速效钾、硝态氮和铵态氮含量在不同植被类型间存在显著的差异性;人工灌木植被对土壤的培肥作用高于乔木植被;农地弃耕(撂荒)有一定的土壤培肥作用;对水土流失极为严重的黄土丘陵沟壑区来说,在退耕还林还草时应优先考虑恢复灌木和草本等先锋植被;在土壤质量改善到一定程度时,再进行乔木的间植;农地弃耕是一种节省人力物力而其生态环境效应又很好的双赢途径。

基于参与性调查的农户对退耕政策及生态环境的认知与响应

采用参与性农户评估方法(PRA)对黄土丘陵区107户农户进行了分层随机抽样调查,并根据研究区内地形等条件将所调查农户分为旱地农户和川水地农户两组,就目前农户对退耕还林还草政策的态度及农户对生态环境的意识及行为的异同进行分析比较。尝试从农户行为角度研究区域发展问题,并基于对农户行为的分析,对区域相关政策制定、实施以及生态环境建设等提出相关建议。研究表明:研究区农户对于土地依赖性较大,旱地农户表现尤为突出,大多数农户对于退耕持支持态度。农户进行的相关水土保护措施,很大程度上并不是农户经过决策后有意识的自觉行为,而是农户为了保证基本农业生产,采取的相应的对策所产生的效应。在土地管理及水土保护措施方面,除了相关的种植措施外,旱地农户更多倾向于通过工程措施来获取好的回报,而川水地农户更多注重于现有土地质量的管护,来进一步提高现有耕地的质量。农户对于环境重要性的认识较为明确,川水地农户认识要比旱地农户更充分一些。与10a前相比,近80%的农户认为当地的生态环境有所好转,然而近45%的农户在生产活动过程中根本不考虑对生态环境的影响,两组农户之间差异不大。超过55%的农户认为生态环境恶化首要原因是气候的影响,干旱是关键因子,其次是过度放牧(24.5%)和水土流失(22.5%)等,两组农户对于生态环境恶化原因的认识具有较大的差别,旱地农户认为生态环境的恶化主要原因是干旱和水土流失,而川水地农户认为生态环境的恶化主要原因是干旱和过度放牧。

不同植被恢复模式对黄土丘陵区土壤抗蚀性的影响

提高土壤抗蚀性是防治土壤侵蚀、促进生态恢复的有效途径之一。以退耕1a撂荒地作为对照,该研究通过对恢复30a的刺槐、柠条、油松与刺槐-紫穗槐、油松-紫穗槐5种不同植被恢复模式进行土壤抗蚀性的探索研究,结果表明,与对照相比,不同植被恢复模式的土壤抗蚀性均明显增强,土壤有机质含量、土壤黏粒含量以及土壤颗粒间团聚程度显著提高。采用土壤有机质含量、水稳性团聚体含量、水稳性团粒平均质量直径、团聚度和分散系数等指标计算该区土壤抗蚀性,进行抗蚀性等量评价。不同植被恢复模式土壤抗蚀性大小顺序为:油松(PC16)、刺槐(RP21)、柠条(AK18)、油松-紫穗槐(PA17)和刺槐-紫穗槐(RA20),纯林土壤抗蚀性强于混交林。该区采用油松、刺槐和柠条纯林恢复模式效果要优于油松-紫穗槐和刺槐-紫穗槐混交模式。

晋西黄土区林地坡面土壤水分异质性研究

经过多年观测,研究了晋西黄土区林地坡面土壤水分异质性的变化规律,通过不同数学方法分析土壤水分与环境因子的关联,探讨坡面尺度上的土壤水分空间异质性的影响因子。结果表明,晋西黄土区林地坡面土壤含水量呈现出明显的剖面与时间变化规律;土壤平均含水量在100cm以内,从表层开始随着土层深度的增加而减少,变异系数也相应减小;土壤含水量与前期降雨呈现出显著的线性关系;变异系数在降雨后迅速减小,并随着干旱天数的增加而增加。通过灰色关联与多元回归分析得出在坡面尺度上土壤水分是地形因子、植被因子等多重因子共同作用的结果,对于不同土层土壤水分来说,影响因素所起的作用也不相同。在坡面尺度上气象因子对土壤水分的空间异质性影响不大。

黄土丘陵区人工灌木林恢复过程中的土壤微生物生物量演变

采用时空互代法,以黄土丘陵区生态恢复过程中不同年限的人工柠条和沙棘林为研究对象,选取坡耕地和天然侧柏林为对照,分析了植被恢复过程中土壤微生物生物量、呼吸强度、代谢商(qCO2)及土壤理化性质的演变特征.结果表明:生态恢复过程中人工柠条林土壤理化性质得到明显改善,微生物生物量随恢复年限的增加变化显著,柠条栽植7a后微生物生物量碳较坡耕地显著增加,随后每5～7a的变化均达到显著水平;微生物生物量氮和微生物生物量磷在前13a无显著变化,20～30a处于基本稳定期,较坡耕地显著增加,但明显低于天然侧柏林;呼吸强度随恢复年限的增加逐渐升高,20～25a达到最大值,随后开始下降,30a时达到最低值;qCO2在恢复初期较坡耕地显著升高,随后迅速降低,30a后回落至坡耕地之下,但仍显著高于天然侧柏林;不同灌木林对土壤质量的改善作用不同,恢复年限相同的沙棘林土壤微生物生物量、呼吸强度明显高于柠条林,但qCO2无显著差异.相关性分析显示,微生物生物量碳、氮、磷、qCO2与土壤养分和恢复年限显著相关.黄土丘陵区人工灌木林可通过生物的自肥作用恢复土壤肥力和增加微生物生物量,但要恢复到破坏前该地区顶级群落时的土壤微生物生物量和理化指标,必须加强林地管理,促进植物群落的拓殖与更替,且此过程相对于生态破坏过程要漫长的多.