Regional differences in gully network connectivity based on graph theory:a case study on the Loess Plateau,China

Material exchange frequently occurs in gullies,and thus the relationship between a gullynetwork structure and sediment transport potential has attracted considerable interest.However,previous researches ignored the difficulty of material transport from sources to sinks,and did not quantify the connectivity of a network structure.In this study,we used a graph model structure to model gully networks of six typical sample areas in the Loess Plateau of China and quantified gully network connectivity using four indexes:average node strength,accessibility from sources to sinks,potential flow,and network structural connectivity index.Results show that:(1)Reflected by different quantitative indexes,the trends of gully network connectivity in different regions are similar.From north to south,the connectivity of a sample area first increases and then decreases.(2)The more mature gullies have stronger network connectivity.Small resistance is conducive to material transport in the gullies.(3)The node connectivity index of the gully network shows a significant aggregation distribution in space,and node connectivity on the main channel is often stronger than that on the branch trench.These results not only deepen the understanding of the process and mechanism of loess gully geomorphic development and evolution but also provide a reference for geomorphic studies.

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.

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.

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.

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.

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.

Optimizing field management to promote the ecologicalization of agriculture in loess hilly-gully region,China

Scientific field management is an important path to realize ecological production and sustainable development of agriculture.As the main content of field management,nitrogen(N)management is the key to balance the economic and ecological benefits of agricultural production.In the loess hilly-gully region,for the fragile ecological and social system,ecologicalization of agricultural production is an important direction to promote sustainable agricultural development.However,irrational fertilization has been one of the main constraint factors,hindering the ecologicalization of local agriculture.In order to solve the problem and prove the practical significance of field management to ecologicalization of agriculture,this study aimed at evaluating the effects of different N fertilization rates and timing using Root Zone Water Quality Model(RZWQM)and then optimizing the N management.Experiments were conducted from 2018 to 2019 in Yangjuangou watershed,loess hilly-gully region,to calibrate and validate the model.The root mean square error(RMSE)of soil water content,nitrate N concentration,above-ground biomass,leaf area index ranged from 10.5-13.5 mm,2.96-3.80 mg·kg^(−1),730.3-1273.9 kg·ha^(−1)and 0.26-0.38,respectively,with the agreement index(d)between observed and simulated values ranging between 0.88 to 0.98.Simulation results showed that N leaching in semi-arid areas was also quite high due to concentrated rainfall and loose soil,which had previously been neglected.When the fertilization rate decreased by 35%(applying the chemical fertilizer at rate of 245.7 kg N ha^(−1))of typical fertilization(applying the chemical fertilizer at rate of 378.0 kg N ha^(−1)),the leaching and residual N decreased by 72.2%-75.4%and 35.6%-50.9%,respectively,while NUE increased by 41.5%-45.2%with no reduction in maize yield.Additionally,compared with applying additional N at seedling stage in one batch,applying at seedling and jointing stages in two batches further decreased N leaching and improved NUE.Thus,a 35%reduction of typical fertilization rate combined with applying additional N at seedling and jointing stages is recommended.From the perspective of N management,this study demonstrated optimizing field management can play a positive role in the ecologicalization of agriculture,and more field management measures should be explored.

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。

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。

传统村落的活态评价与适应性保护发展研究——以陇中黄土丘陵沟壑区3个典型传统村落为例

面对传统村落多维度失活,通过重新识别村落活态因子,研判失活、衰退主导因素,能够进一步为传统村落可持续发展提供新的思路。以陇中黄土丘陵沟壑区3个典型传统村落为例,立足本土地域环境,综合考虑村落活态发展因素,构建3层共28项活态性评价指标体系。研究发现:(1)3个传统村落均有失活现象,但在失活程度上有所分化。金崖和黄家庄村处于“微失活”,失活程度较轻,保护与发展的适应性、可持续性一般;古城村处于“失活”,失活现象较明显,保护与发展的适应性、可持续性较弱。(2)3个传统村落的村落治理、地域环境失活贡献率占比较高,对传统村落的活态发展影响较大;村落治理、经济发展和地域环境在失活指数上占比较高,对村落失活的影响较显著,可判断出陇中黄土丘陵沟壑区传统村落的适应性发展受村落治理、地域环境因素影响较大。(3)活态总分上,金崖村(71.63)>黄家庄村(68.58)>古城村(58.88),这与调研结果相吻合。村落失活是多因素综合、内外动力共同作用的结果,因此适应性、永续性的保护发展方式是村落振兴和活态化发展的关键。

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。

Eco-environment Restoration and Regional Differentiation Characteristics Based on “Building Terrace and Returning Slope Farmland to Forests and Grass”

Based on the scientific and technological achievements in the past decade in the Loess Hilly-gully Region and the successful demonstration experience in Yan'an Yangou watershed, we summarize the characteristics of eco-environment restoration pattern based on "building terrace and returning slope farmland to forests and grass". According to the data on land use, slope farmland and the agricultural population in 1999, we calculate the area of new terrace that needs to be built, the area of garden plot that needs to be extended, vegetation restoration area and investment demand in counties (cities, districts). Establishing and using some indicators, such as basic farmland extension indicator, garden plot extension indicator, vegetation restoration index and investment demand density, we conduct type classification and analysis of regional differentiation characteristics in 55 counties (cities, districts). The results show that in the Loess Hilly-gully Region, 691 600 hm2 of new terrace needs to be built, 792 000 hm2 of economic forests and orchards need to be extended, 5 410 200 hm2 of vegetation needs to be restored, and the total investment demand is 15.82 billion yuan; in terms of geographical distribution, obviously there are two key areas for eco-environment restoration (one is located in the border area between northern Shaanxi and northwestern Shanxi, and the other is located in the eastern Gansu and southern Ningxia area); the classified regional guidance policies should be formulated as soon as possible, and the limited funds should be concentrated in the key areas.

人地关系视角下黄土丘陵沟壑区乡村公服设施布局优化探析——以陕西子洲县为例

城镇化水平的不断提高,使得乡村社会的发展认知由“底线思维”向“发展思维”转变,村民需求由“生存型”向“品质型”转变。加之近年来国家关于公共服务均等化政策的落实与深化,乡村公服设施建设的“量与质”都有了较大提升,但由于忽视了村庄的地域特征、人口发展、村民需求等因素,使得现有乡村公服设施配置出现使用效率低下、空间品质不佳、功能关联性较差等问题。基于此,本文通过陕西省榆林市子洲县乡村公服设施空间布局分析,采用田野调查、POI数据分析等方法进行深入研究,总结子洲县公服设施问题主要体现在需求供给错配、空间布局错位,功能行使错用三方面。最后基于人地关系视角,探寻人口流动与地理空间对公服设施配置的影响,并提出黄土高原丘陵沟壑区乡村公服设施优化布局策略,以期为提高我国乡村地区的发展能力,推进城乡一体化建设,早日实现乡村振兴提供参考。

宁南黄土丘陵区侵蚀沟不同部位植物多样性与土壤养分

[目的]探明宁南黄土丘陵区侵蚀沟不同部位植物多样性与土壤养分的关系,为侵蚀沟的水土保持及防护提供依据。[方法]以宁夏彭阳县玉洼流域3个稳定侵蚀沟的沟头、沟床、沟岸为对象,通过野外植被调查,同时采集0—10,10—25,25—40,40—55,55—70 cm土样,在室内测定土壤有机碳、土壤全氮、土壤全磷含量,分析了侵蚀沟不同部位(沟头、沟床、沟岸)的植物多样性及土壤养分特征。[结果]侵蚀沟沟头植物隶属3科6属,禾本科4属4种,伞形科和豆科各1属1种;沟床植物隶属5科12属,禾本科4属4种,菊科5属5种,豆科、茜草科和伞形科各1属1种;沟岸植物隶属3科7属,禾本科4属4种,豆科2属2种,伞形科1属1种。侵蚀沟各部位植物种数表现为:沟床>沟岸>沟头,均以禾本科植物为主。生活型上,各部位均以多年生草本植物搭配一、二年生草本植物为主。侵蚀沟的地上生物量、Shannon-Wiener指数、Patrick指数和Margalef指数均表现为:沟床>沟岸>沟头;Simpson指数表现为:沟头>沟床>沟岸;Pielou指数表现为:沟头>沟岸>沟床。侵蚀沟各部位平均土壤有机质、土壤全磷和土壤全氮含量均表现为:沟床>沟岸>沟头,且主要集中在0—10 cm和55—70 cm。侵蚀沟沟头和沟岸的地上生物量与土壤有机碳呈极显著正相关(p<0.01)、与土壤全磷呈显著正相关(p<0.05);侵蚀沟沟床的Shannon-Wiener指数与土壤全磷呈显著负相关(p<0.05),地上生物量与土壤有机碳呈极显著正相关(p<0.01)。[结论]侵蚀沟沟头易崩塌且土壤养分条件较差,应配置根系发达、茎干粗壮、耐冲性强的乡土树种,沟床、沟岸养分较高可优先配置碳、氮、磷含量需求较大的草本或灌木。

黄土丘陵沟壑区现代沟道农业及其可持续发展

现代沟道农业是黄土丘陵沟壑区人地耦合发展形成的一种新兴农业地域类型,其可持续发展对于区域农业高质量发展、“三生”空间优化和乡村振兴具有重大现实意义。从人地系统科学认知出发,对现代沟道农业的内涵、可持续发展方向、典型发展模式和保障体系进行了探讨,并进行了相关研究展望,为系统认识黄土丘陵沟壑区沟道农业模式,推进农业可持续发展提供了理论参考。主要结论:①沟道农业是乡村地域系统的重要功能类型,具有多尺度、多层次的特点,其可持续发展应从微观、中观和宏观3个层面,协同解决土壤生态系统、农田生态系统和农业地域系统的可持续发展问题。②保障粮食安全和生态安全,积极推进农业结构调整,发展多功能农业,通过“3C”模式,即农业自身内循环、农业外循环、基于农业多功能的农业大循环,实现生产结构优化、产业链条延伸和城乡功能互补。③创新推广土地综合整治带动模式、农业结构调整带动模式、特色资源综合开发模式和土地流转规模生产模式,有助于农业提质增效和农业高质量发展。④拓展地理学与其他学科的交叉研究,深化“理论−实践”贯通式研究,探索建立涵盖技术研发与应用、人才培养、政策制度支撑等内容于一体的农业生产保障体系,全面提升沟道农业资源利用效率和综合生产效益,推动沟道农业现代化。

黄土丘陵沟壑区村域客观福祉评估及其对农民主观福祉的影响——以陕西省米脂县为例

探究黄土丘陵沟壑区村域客观福祉及其对农民主观福祉的影响对完善乡村地区人类福祉研究、推动乡村振兴具有重要意义。研究以该区域陕西省米脂县为例,基于人类需求理论评估村域客观福祉空间分布,从认知维与情感维评估农民主观福祉,利用多层次模型揭示村域客观福祉对农民主观福祉的影响。结果如下:(1)村域各需求维度与客观福祉空间分异明显;川道村、乡镇中心村、乡村振兴示范村是各需求满足程度与客观福祉较高的村庄。(2)生活满意度与情感健康呈显著正相关;男性、身体健康者、年长者以及年收入较高农民的主观福祉较高;主观福祉对教育程度不敏感。(3)住房、村卫生室、医疗参合率、集体经济、信息通达度、农技培训、休闲设施面积、村庄整洁等与农民主观福祉呈显著正相关,地质灾害与主观福祉呈显著负相关。

高质量发展背景下黄土沟壑区乡村流域空间治理:目标、困境与实现路径

高质量发展阶段,黄土沟壑区乡村治理的空间范畴、配置动力、行动主体已发生变化。面向生态安全到生态持续、经济脱贫到经济高效、社会稳定到社会公平的目标变化,针对乡村治理载体、治理动力、治理主体呈现的空间要素分散治理、资本价值诉求冲突、参与治理意愿减弱等问题,基于乡村空间流域化特征,依托次沟流域构建乡村治理单元,文章提出功能协同、价值协调、主体协作3大治理路径,以促进乡村空间要素、资本要素和行动主体之间的良性互动。

陇东黄土丘陵沟壑区森林生态服务功能及其价值评估

探讨陇东黄土丘陵沟壑区森林资源生态服务功能价值,为该区域生态修复保护及森林生态服务功能评估提供可推广、可复制的范式。以泾川县2018年森林资源二类调查数据及相关文献资料为基础,依据《森林生态系统服务功能评估规范》,选取4方面10个指标构建评估体系,采用市场价值法、价格替代法等方法,评估陇东黄土丘陵沟壑区森林生态服务功能价值。结果表明,2019年泾川县森林生态系统总服务价值为283600.0万元。涵养水源服务价值最大,占总服务价值50.76%;文化旅游服务价值最小,占总服务价值的0.0025%;生态林以涵养水服务价值为主,经济林以供给服务价值为主,生态林年服务功能价值为经济林的3.8倍。涵养水源、固碳释氧、产品供给3种价值占总服务价值的80.21%,是主要的生态服务功能价值。因地制宜营造培育混交林,加强现有林分修复改造、提升森林资源质量、创新经营策略成为该区域森林资源管理的重点。