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.

Land-use changes in the small watershed of the Loess Plateau,hilly-gully region, China

As more and more farmland is converted to forestry, the need for effective decision support regarding the use of land in the fragile ecological environment of the Loess Plateau hilly-gully area. The Luoyugou watershed was chosen as the study area to calculate the single dynamic degree, integrated dynamic degree, and change indexes of land use, as well as the land-use type transition matrix. This was done by interpreting the TM and SPOT images of the Luoyugou watershed in 1986, 1995, and2004 and making statistical analysis. The results of ou statistical analysis show that the conversion of slope farm land to terrace and forest land plays a dominant role in land-use changes in the Luoyugou watershed from 1986 to2004. The land-use changes are mainly driven by popula tion growth, socio-economic development, consume spending, and investment in forest ecology.

Dynamic Land Use /Cover Change and Analysis of Landscape Pattern in the Hilly and Gully Region of Loess Plateau: A Case Study of Pengyang County in Southern Ningxia

The quantitative evaluation on land use /cover change as well as its influence on landscape pattern under the background of returning grain plots to forestry is significant to the sustainable utilization of land resources and ecological environment reconstruction in the southern Ningxia.Based on multi-temporal remote sensing data from four periods of Landsat TM /ETM,and combination of ecological quantity analytical method with GIS,the change of land use /cover and landscape pattern in Pengyang County of Ningxia Province were analyzed.The conclusions showed that the amount of each land use type was changed with different degrees,the area of forest /grass land increased,while farmland and unused land decreased.The change of landscape pattern was characterized as that the degree of landscape fragmentation,mixed distribution of patches,diversity index and evenness index increased gradually and then decreased,the connectivity between patches decreased gradually and then increased,and landscape shape presented irregular.

The characteristics of gully erosion over rolling hilly black soil areas of Northeast China

In this study,short-term gully retreat was monitored from the active gullies selected in representative black soil area,using differential global positioning system(GPS).With the support of geographic information system(GIS),multi-temporal digital elevation models(DEM) were constructed from the data collected by GPS and used for further analysis.Based on the analysis of multi-temporal DEM,we discussed the erosion-deposition characteristics within gully and a developing model for black soil gully area of Northeast China was proposed.The results are:(1) The analysis of the monitored gully data in 2004 indicated that the retreat of gully head reached more than 10 m,gully area extended 170-400 m2,net gully eroded volume 220-320 m3,and gully erosion modulus 2200-4800 t?km?2?a?1.(2) Compared with the mature gully the initial gully grows rapidly,and its erosion parameters are relatively large.The erosion parameters have not only to do with flow energy,but also with the growth phase.(3) There are significant seasonal differences in gully erosion parameters.The extension of gully area and width dominates in winter and spring without marked net erosion while changes mainly occur in gully head and net erosion in rainy season.(4) It is remarkable for freeze-thaw erosion in the black soil area of NE China.The gully wall of SG2 extended 0.45 m under freeze-thaw effect in 2004,and the distance of gully head retreated maximally 6.4 m.(5) Due to freeze-thaw action and snowmelt,gully is primarily in the interior adjustment process in winter and early spring.There are much more depositions compared with that during rainy season,which can almost happen throughout the gully,while erosion mostly occurs near head,esp.for gullies having a relatively long history of development.On the other hand,the process of energy exchange with exterior dominates in rainy season.It is considered that this cyclic process is an important mechanism for gully growth in high latitude or/and high attitude regions.

A comparison between different ecological de-farming modes in the loess hilly-gully region in China

The eco-environmental restoration has been a chief task of the western development strategies carried out by the central and local governments of China since the late 1990s, and the ecological de-farming has been regarded as a powerful measure for the ecological restoration in the Loess Plateau and the upper reaches of the Yangtze River. "Relieving and de-farming" (RD) and "rebuilding terrace and de-farming" (RTD) are two more mature ones among various de-farming modes. Taking the loess hilly-gully region as a case, this paper summarized the basic characteristics of RD and RTD modes, calculated the sizes of de-farming slope farmland, rebuilt terraces, enlarged garden plots and restored vegetation, and compared the differences of two modes in terms of de-farming area, ecological reestablishment index, investment demand amount and benefits. The results showed that RTD mode has many advantages, including suitable investment, sufficient grain supply and great benefits, and will be the best ecological reestablishment mode in the loess hilly-gully region, and RD mode which is being carried out in this region should be replaced by RTD mode as soon as possible.

Characteristics of Soil Respiration of Terraces and Slope Farmland in Loess Hilly and Gully Regions

Soil CO_2 emissions of terraces and slope farmland in loess hilly and gully regions were measured by using Infra Red Gas Analysis(IRGA),and the diurnal variation characteristics of soil respiration rate in different slope positions of terraces and slope farmland were analyzed.The results show that the diurnal variation curves of soil respiration rate of terraces and slope farmland in loess hilly and gully regions had a single peak.The soil respiration rate of terraces reached the peak during 13:00-15:00,while the soil respiration rate of slope farmland reached the peak from 11:00 to13:00,and it was the lowest at next 07:00.The daily average of soil respiration rate in slope farmland was 0.86μmol/(m^2·s),accounting for 93.48% of that of terraces.The daily average of soil respiration rate in different slope positions of terraces and slope farmland is shown as follows:the bottom of the slope>the middle of the slope>the top of the slope.At the top of the slope,the daily averages of soil respiration rate in terraces and slope farmland were the same;at the middle and bottom of the slope,the daily average of soil respiration rate in terraces was larger than that of slope farmland.

Soil erosion types in the loess hill and gully area of China

ＳｏｉｌｅｒｏｓｉｏｎｔｙｐｅｓｉｎｔｈｅｌｏｅｓｓｈｉｌｌａｎｄｇｕｌｌｙａｒｅａｏｆＣｈｉｎａＦｕＢｏｊｉｅ（ＲｅｓｅａｒｃｈＣｅｎｔｅｒｆｏｒＥｃｏ－ＥｎｖｉｒｏｎｍｅｎｔａｌＳｃｅｉｅｎｃｅｓ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｅｉｅｎｃｅ...

SOC Vertical Distribution Pattern of Economic Plants in the Loess Gully Areas of China

Three economic plants from the loess gully areas in China to explore the changing vertical distribution characteristics of soil organic carbon.The results showed that:(1) with the increase of depth,the average SOC content of economic plants decreased from 13.98 to 1.39 g/kg on the 0-100 cm soil profile,in the form of a power function;(2) the constructed depth spatial distribution models for different plants could help accurately assess the spatial distribution pattern of soil organic carbon;(3) compared with traditional agricultural planting,the carbon sink function for walnut and grape at a soil depth of 100 cm increased by 92.8±8.98 t/hm^(2) and 45.7±7.7 t/hm^(2),respectively.The adjustment of agricultural planting structure increases the content of soil organic carbon,and economic plants are of great significance to enhance the carbon sink function of the agricultural ecosystem in the loess gully area.

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.

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.

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.

罗玉沟流域水沙变化趋势及影响因素

[目的]探讨小流域水沙变化趋势及影响因素,为黄土高原丘陵沟壑区水土流失治理和水土保持措施布设提供参考依据。[方法]采取Spearman秩次相关检验方法、累积距平法和双累积曲线法等对黄土丘陵沟壑区罗玉沟流域1986—2016年降水量、径流量和输沙量变化趋势和演变过程进行分析。[结果](1) 1986—2016年罗玉沟流域年降水量趋势性变化不显著;流域年径流量和年输沙量变化具有明显的阶段性,以1993年为界,年径流量和年输沙量呈显著降低趋势。(2)降水和水土保持措施影响罗玉沟流域年径流量和输沙量,不同降水水平年,降水和水土保持措施对流域水沙变化的影响不同,水土保持措施使流域枯水年份径流量和输沙量减少最为显著。(3)水土保持措施对年径流量和年输沙量的减少贡献率分别为83.50%和80.97%。[结论]降水量变化不显著的情况下,水土保持措施对罗玉沟流域年径流量和年输沙量的减少起主导作用,水土保持综合治理对枯水年径流量和输沙量的影响幅度最大。

富水沟谷区浅埋煤层导水裂隙演化特征

富水沟谷区域下浅埋煤层赋存条件特殊,采场上覆岩层导水裂隙发育演化特征复杂。为了揭示沟谷区浅埋煤层在回采扰动作用下覆岩裂隙演化规律,以朱家峁煤矿1305-2工作面过沟谷区回采阶段为工程背景,采用理论分析、物理相似模拟、数值模拟与现场效果验证的方法,建立了覆岩裂隙−渗流场概念模型,开展了覆岩结构发育与微震能量演化研究,分析了覆岩变形与塑性破坏分布特征,提出了针对沟谷区下浅埋煤层导水裂隙防治措施,并应用于现场工程实践。结果表明:开采扰动下裂隙−渗流场模型呈“梯台”结构,并依次划分为初渗区域、稳渗区域、紊渗区域3个区域;将所研究矿井的工况数据代入模型结构,计算出各个渗透区域范围,并根据计算结果对矿井的稳渗区域采取注浆措施。工作面回采至沟谷区段,覆岩裂隙域形态呈现“拱形-梯形-复合梯形”的扩展演化特征,裂隙纵向发育高度达到163 m,并与沟谷区地表贯通。随工作面推进,地表裂隙依次经历“滑移-挤压-撕裂”过程;沟谷区域位移云图呈现出滞后开采“高位梯形”破断形态,在沟底处下沉位移最大,达3.47 m。针对开采导致的裂隙大范围扩展贯通,提出在地面进行采动裂缝注浆处理,在工作面上覆岩层进行注浆封堵,实现过沟谷区开采“井上−井下”联合防治,保证安全开采。该研究结果可为浅埋煤层的过沟谷区开采、采动裂隙防治及富水区“保水采煤”提供新的科学依据。

黄土高原河谷城镇“川—沟”融合单元发展路径研究

通过分析黄土高原河谷城镇独特的城乡关系与发展困境,认为川道与次沟空间结构一体化、功能结构差异化发展是振兴黄土高原丘陵沟壑区的重要突破口,由此提出“川—沟”融合单元的概念内涵与划定方法。以榆林市绥德县为例,打破镇域行政边界和小流域镇村体系,基于川道城镇和次沟乡镇的空间关联关系划定10个融合单元,并从用地形态结构、产业经济地理、服务设施配置等方面对融合单元的空间构型、功能类型和服务水平进行剖析,探讨川道与次沟协同视角下以融合单元为抓手推动黄土高原河谷城镇高效发展和管控治理的新路径。

黄土丘陵沟壑区村庄生态系统服务对人类福祉的影响机理——以陕西省米脂县为例

[目的]在生态脆弱区,探究村庄生态系统服务对人类福祉的影响机理,为推动区域可持续发展提供参考。[方法]以黄土丘陵沟壑区陕西省米脂县为例,基于生物物理指标、人类需求理论分别评估村庄服务与福祉,分析了两者的空间分布。基于结构方程模型揭示了村庄禀赋视角下村庄服务对福祉的影响机理。[结果](1)作物和肉类空间分布相近,水果供给呈集中分布;高土壤保持村庄分布于南部丘陵,水源涵养和生境质量均西部高于东部;景观美学东部高于西部,高休闲娱乐村庄集中于城镇区。(2)村庄各需求、福祉空间分布差异较大。高福祉村庄包括川道村、多数乡镇中心村、乡村振兴示范村;低福祉村庄主要位于东西部丘陵,需政府重点关注。(3)村庄服务对福祉产生正向影响,作物、肉类、水源涵养是影响村庄福祉的关键服务。村庄禀赋对服务、福祉产生正向影响,且村庄禀赋通过提高村庄ES间接改善村庄福祉水平。高程是关键的自然禀赋,非文盲率和老龄化率是关键的社会禀赋;距县城距离是关键的区位禀赋。[结论]村庄服务与福祉空间差异明显,禀赋—服务—福祉的影响路径显著。依据空间差异与路径差异施策,是提升生态系统服务福祉贡献的要求。

北洛河上游流域植被覆盖度时空变化及其地形分异特征

[目的]揭示退耕还林还草工程实施前后黄土丘陵沟壑区流域植被恢复过程,阐明流域植被恢复的地形分异效应,进而为黄土丘陵沟壑区制定适宜的流域生态建设和保护对策提供科技支撑。[方法]基于北洛河上游流域1990—2019年4期Landsat影像及数字高程模型数据,利用像元二分模型结合GIS技术,开展了退耕还林还草工程实施前后该流域植被覆盖度变化地形分异特征研究。[结果](1)流域植被覆盖度在空间上呈现东南高、西北低的分异特征。1990—2019年流域年均植被覆盖度呈持续上升趋势,在退耕还林还草工程实施以后高等级植被覆盖度面积占比大幅提升,1990年、2000年、2010年、2019年高等级植被覆盖度面积占比分别为0.97%,6.96%,42.17%,64.18%。(2)在工程实施的各个时期,流域植被覆盖总体持续改善,但西北局部地区植被退化。研究期间,流域植被覆盖度结构改善明显,中高及高植被覆盖度面积以转入为主,中低及低植被覆盖度面积以转出为主。(3)流域植被覆盖度在地形上存在明显分异特征,植被覆盖度随高程的增加呈减小趋势,植被覆盖度与坡度呈正相关,坡度越陡,植被覆盖度越大,植被覆盖度随坡向遵循阴坡>半阴坡>平地>半阳坡>阳坡的分布规律。[结论]实施退耕还林还草工程对增加北洛河上游流域植被覆盖度起到了关键作用,但部分区域植被退化严重,未来该流域应重点关注城市空间扩展以及气候变化对植被建设的影响,以应对环境演变下植被生态系统可持续发展面临的挑战。

浅埋煤层过沟开采覆岩破坏特征及水害防治技术研究

黄土沟壑区溃水水害是浅埋煤层开采的主要灾害之一。安山煤矿煤层埋藏浅、局部沟道所在区域5-2煤层顶板距离地表不足30 m,为了解决黄土沟壑区工作面过沟开采可能遇到的水害问题,通过数值模拟的手段研究了工作面过沟开采时的覆岩破坏特征,提出了研究区过沟开采时冒裂安全性分区标准,并基于分区结果提出了预防工作面过沟开采发生溃水水害事故的防治技术,过沟开采防治技术包括采前筑坝截流引流,采后工作面地表裂缝修复等,并在工作面过沟开采区域成功地进行了防治应用,应用结果表明,防治技术能够有效预防工作面过沟开采溃水水害。研究成果对榆神矿区工作面安全、绿色高效过沟开采具有一定的借鉴意义。

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。

黄土丘陵沟壑区梯田的碳汇作用及其变化特征

[目的]定量分析和探讨梯田碳汇作用与其特征,为明确梯田的碳汇作用、巩固和提升生态系统碳汇能力、研编梯田碳汇方法学等提供科学参考。[方法]选取黄土丘陵沟壑区的陕西省吴起县1~7 a(T_(5)),8~12 a(T_(10)),13~17 a(T_(15)),18~22 a(T_(20)),23~27 a(T_(25))这5个年份区间的梯田作为研究对象,以未实施水土保持措施的坡耕地为对照,研究不同年份梯田保碳、减排、增汇等能力与其变化规律。[结果]①坡耕地修建为梯田后可发挥保碳、减排、增汇等碳汇作用,梯田年均保碳量、减排量、增汇量(0-100 cm)分别为0.26,0.05,1.36 t/(hm^(2)·a)。②梯田各土层均发挥了一定的增汇效益,表层土壤(0-40 cm)和深层土壤(40-100 cm)增汇效益分别占0-100 cm整个土层的61.50%和38.50%。③随着运行年份的增加,梯田表层土壤增汇效益显著增加,深层土壤的增汇效益稍有提升但总体上保持平稳。表层土壤增汇率从T_(5)的16.30%提升至T_(25)的51.34%,深层土壤从T_(5)的14.00%提升至T_(25)的23.66%。[结论]黄土丘陵沟壑区梯田发挥着良好的保土保碳、减蚀减排和土壤增汇等碳汇作用。在修建27 a内,梯田增汇作用的比例最大,且表层土壤增汇更为显著;随着运行年份增加,梯田保碳作用的比例将逐渐增大。

人类活动对延河流域生态地质环境承载力影响研究

目的为探究治沟造地和平山造城重大工程对延河流域生态地质环境承载力(ecogeological environment carrying capacity,EGCC)的影响,方法利用分形理论和信息量模型构建研究区EGCC评价模型,揭示延河流域环境承载力时空模式及流转态势,构建人类活动强度指数,采用最小二乘法和皮尔逊相关系数探讨人类活动与EGCC之间的关系。结果结果表明:延河流域1990—2018年EGCC整体状况明显改善,平均值从−0.299上升至−0.197;EGCC分布多年来呈“中部最高,东南次之,西北最低”格局;人类活动强度从1990年成片分布逐渐发展到2018年“单核辐射”分布,高强度区主要分布在延河流域中部;人类活动强度与EGCC相关度较高,一定范围内呈正向促进关系;受平山造城工程活动影响,2010—2018年高水平和较高水平承载力面积分别增加了1.610,3.164 km2;EGCC变化趋势因治沟造地工程所处乡、镇地理位置和发展侧重不同而存在差异。结论人类活动与生态地质环境承载力呈较强的正相关关系,治沟造地和平山造城工程对EGCC具有一定积极影响。