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, taking 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 by climate variation was estimated using empiric formulae, we obtained the part induced by human factors, i.e. the SLCP. The human induced part of NDVI change was considered as an approximation indicating the effect of the SLCP on the vegetation. Finally, we analyzed the NDVI 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.

De-farming and Ecological Restoration in the Loess Hilly-gully Region in Northern China

De-farming has been a powerful measure taken by the central and local governments of China for ecological restoration in the loess hilly-gully region since 2000. In years past, aid-based de-farming pattern was far and wide popularized in the region and terrace-based de-farming pattern demonstrated in a few small watersheds was also rather effective for ecological restoration. After summing up the features of three patterns (aid-based de-farming slope farmland more than 25°(AD25), aid-based de-farming slope farmland more than 15° (AD15) and terrace-based de-farming (TD)), this paper analyzed the regional difference of these patterns in de-farming area, ecological restoration, investment demand and so on. The results show that there are two crucial areas in the loess hilly-gully region for ecological restoration at the moment, the policies adaptation to the different areas should be constituted as soon as possible and the limited fund should be devoted to the two crucial areas.

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.

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

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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.

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.

Research on the Development Model of Ecological Agriculture in Loess Hilly-Gully Region of Northern Shannxi, China

On the Loess Plateau of China, facing the vulnerable environment, local people have to try their best to guarantee the security of food, and at the same time, to control the most serious soil erosion in the world. The paper introduces two typical models of ecological agriculture: ecological agriculture with commodity and agriculture with soil and water conservation. According to the local natural condition, the model of eco-agriculture with commodity could be characterized by the structure of “agriculture-byproduct”, “agriculture-fruit” or “agriculture-forestry-husbandry”. The development of agriculture with soil and water conservation has decreased the soil erosion rate from 12, 184 ton/kin^2 in 1980 to 458.4 ton/kin^2 in 1999, while the farmers' income has increasingly risen. Analyses on the two models' benefits both in terms of ecological and agricultural economy show that there is a great possibility to construct or restore good eco-environment with comprehensive control in the hilly-gully area of north Shannxi. Further more, the paper points out the potential problems of foodstuff production and stockbreeding development in forming ecological agriculture and eco-environmental restoration.

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.

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。

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.

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。

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。

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。

多源土地利用产品在黄土丘陵沟壑区的精度评估

[目的]为评估多源土地利用产品在黄土丘陵沟壑区的精度。[方法]以黄河二级支流关川河流域为例,基于高精度GCLUCC土地利用数据,从空间分布、面积特征、样本点精度和空间一致性4个方面评估空间分辨率为10,30 m的6种土地利用产品(WorldCover 10 m、ESRI 10 m、GLC_FCS30-2020、GlobleLand30、CNLUCC和CLCD)的准确性。GCLUCC数据是基于GF-2(0.8 m)、DEM(5 m)、野外采样点(6400个)和Google Earth样本点(2320个),采用面向对象法和人工目视解译,空间分辨率为1 m,整体精度超过95%。[结果](1)分类特征方面,多数产品能提取主要土地类别,但提取效率和准确度存在明显差异,特别是在耕地、林地和建设用地等地类的空间分布上。(2)面积一致性上,各产品与GCLUCC在不同地类的面积上存在显著差异。部分产品的草地面积是GCLUCC的2倍以上,而林地和水域面积仅占GCLUCC的0.13%~12.11%和1.41%~11.27%。(3)整体精度方面,GlobleLand30和WorldCover 10 m展现较高精度,空间图谱精度分别达到58.21%和50.19%。而CLCD和CNLUCC的准确性相对较低,其中,林地与草地、耕地与草地及建设用地与耕地间的分类混淆严重。(4)所有产品与实际地表间的空间误差显著,尤其在对乔木、灌木、裸地和水体分类上面临挑战。[结论]当前土地利用产品在黄土丘陵沟壑区精确表征地表覆盖特征方面存在挑战。未来的产品开发应更多地考虑地形和地理特征,并加强对特定土地利用类型的识别。研究结果可为黄土高原生态保护和地表信息获取提供理论参考。