宁南黄土丘陵区不同生态恢复与重建中的土壤水分变化研究

针对宁南黄土丘陵区存在的生态脆弱、环境恶化的突出问题,对黄土丘陵区不同生态恢复过程中的土壤水分变化进行了研究。研究结果表明:在退化山地的植被恢复过程中,0￣60cm土层,土壤水分含量随恢复年限的增长而增加,在60cm土层以下,土壤含水量随着退耕年限的不断增长不断减小;对于不同恢复方式的土壤水分含量,88542水平沟>人工草地>鱼鳞坑>天然草地;对于不同植被类型的土壤水分含量,草地>灌木地>林地;对于不同地形的土壤水分含量,阴坡>半阴坡>阳坡,坡下部>坡中部>坡上部,并且随着坡度的不断增加,土壤水分含量不断减小。

Analysis of debris flow control effect and hazard assessment in Xinqiao Gully,Wenchuan M_(s)8.0 earthquake area based on numerical simulation

Xinqiao Gully is located in the area of the 2008 Wenchuan M_(s)8.0 earthquake in Sichuan province,China.Based on the investigation of the 2023"6-26"Xinqiao Gully debris flow event,this study assessed the effectiveness of the debris flow control project and evaluated the debris flow hazards.Through field investigation and numerical simulation methods,the indicators of flow intensity reduction rate and storage capacity fullness were proposed to quantify the effectiveness of the engineering measures in the debris flow event.The simulation results show that the debris flow control project reduced the flow intensity by41.05%to 64.61%.The storage capacity of the dam decreases gradually from upstream to the mouth of the gully,thus effectively intercepting and controlling the debris flow.By evaluating the debris flow of different recurrence intervals,further measures are recommended for managing debris flow events.

Hierarchy structure characteristics analysis for the China Loess watersheds based on gully node calibration

A land surface region can be decomposed into a series of watershed units with a hierarchical organizational structure. For loess landform, the watershed is a basic spatial–structural unit that can express natural landforms, surface morphology characteristics, spatial organization and developmental evolution. In this research we adopted the concept of node calibration in the watershed structure unit, selected six complete watersheds on China Loess Plateau as the research areas to study the quantitative characteristics of the hierarchical structure in terms of watershed geomorphology based on digital elevation model(DEM) data, and then built a watershed hierarchical structure model that relies on gully structure feature points. We calculated the quantitative indices, such as elevation, flow accumulation and hypsometric integral and found there are remarkably closer linear correlation between flow accumulation and elevation with increasing gully order, and the same variation tendency of hypsometric integral also presented. The results showed that the characteristics of spatial structure become more stable, and the intensity of spatial aggregation gradually enhances with increasing gully order. In summary, from the view of gully node calibration, the China Loess watershed structure shows more significantly complex, and the developmental situation variation of the loess landforms also exhibited a fairly stable status with gully order increasing. So, the loess watershed structure and its changes constructed the complex system of the loess landform, and it has the great significance for studying the spatial pattern and evolution law of the watershed geomorphology.

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.

黄土丘陵沟壑区不同植被恢复类型昆虫群落结构及多样性的研究

为探讨黄土高原植被恢复过程中植物与昆虫群落的关系,评价人工植被和自然恢复植被种类搭配的合理性,为退化生态系统的植被恢复提供依据。采用样地调查法,在黄土丘陵沟壑区纸坊沟流域研究比较了不同植被恢复类型昆虫群落组成、结构及多样性的变化。结果表明,2种不同植被恢复类型区昆虫有189种(含蜱螨目),分别隶属13目84科。而不同植被恢复类型昆虫群落的物种数、丰富度、多样性、均匀度及优势度指数值均有明显差异。以20a自然封育植被恢复区昆虫群落的物种数、丰富度、多样性、均匀度指数值均较高,其值分别为160、21.17、1.4914和0.6918。优势度则以人工治理区(0.7251)>自然封育区(0.5845)。说明从人工治理区到自然封育区,随着植被种类增加,昆虫种类相应增加,优势种由突出降至不明显,昆虫群落稳定性提高。

黄土丘陵小流域景观空间格局动态分析——以固原市上黄试区为例

为黄土高原土地资源合理利用及区域可持续发展提供参考,以上黄试区为例,在地理信息系统支持下获得计算景观多样性的有关参数,选取斑块大小及数量、分维数、斑块伸长指数、多样性、优势度、均匀度和破碎度等指标,对黄土丘陵小流域10年来景观多样性动态变化进行分析。结果显示:1995—2004年,该试区总斑块数增加了6个,斑块变化明显的主要表现为:坡耕地及天然草地斑块分别减少19个和12个,人工草地斑块及梯田分别增加15个和9个;平均斑块面积及平均斑块周长分别下降了0.14hm2和185.36m2;梯田、天然草地、疏林地、园地及居民点用地分维数,都有不同程度的下降,而坡耕地、人工草地、灌木林地及未利用地景观的分维数有所上升,水浇地、川台地、乔木林地、水域景观分维数保持不变;上黄试区景观异质性特征表现为:均匀度指数下降5.86,景观破碎度指数上升0.002,人为干扰度增加1.95,景观类型多样性指数下降0.25,优势度指数上升0.25。目前,试区从耕地及草地为主的景观生态系统,转变为以林地和草地景观为主的高度异质化的景观生态系统,人类活动的干预,是驱动该试区景观空间格局变化的主要驱动因素。

陕北黄土丘陵区乡村聚落土壤水蚀观测分析

通过2004年6月至10月,在陕北对降雨形成的乡村聚落土壤侵蚀的定位观测,其结果表明:①乡村聚落的平均径流系数为0.335,其中延安最大,为0.44;榆林和绥德较小,分别为0.293、0.272。同时,道路和庭院的径流系数较大,分别为0.39、0.377,户间空地较小,为0.277;②径流平均含沙量以户间空地最大(52.54g/l),次为户间道路(41.42g/l),而院落径流含沙量较小(17.78g/l);③乡村聚落的平均侵蚀强度为5434.3t/km2,已达强度级侵蚀,其中户间道路、户间空地侵蚀较大,分别为7348t/km2、6873t/km2,庭院相对较小,为2081.7t/km2;④乡村聚落土壤侵蚀的变化,受人为影响更加突出。说明黄土高原乡村聚落土壤侵蚀较严重,并且具有特殊性,不可忽视,应加强研究和防治。

黄土丘陵区达乌里胡枝子人工草地生产力与土壤水分特征研究

对黄土丘陵区川地和坡地达乌里胡枝子(Lespedezadavurica)人工草地生产力与土壤水分状况的季节变化动态进行比较研究。结果表明,川地达乌里胡枝子人工草地生产力显著高于山坡地,单位面积干重约为山坡地的3倍。不同立地下达乌里胡枝子耔实部分约占地上部分最终生物量得到30%￣40%。川地与山地叶片水分利用效率相近,因而川地达乌里胡枝子在维持高生产力情况下,260cm以下土壤层出现雨季期间及休闲期后均不能够恢复的稳定低湿层。

黄土丘陵沟壑区退耕地自然恢复植被特征及其与土壤环境的关系

为给黄土高原退耕地的植被恢复和重建提供科学依据,以黄土高原丘陵沟壑区的安塞县为例,用系统聚类和逐步多元回归的分析方法,对退耕地自然恢复植被的演替阶段进行划分,并定量分析群落演替过程中的植被特征及其与土壤环境的关系。结果表明:黄土丘陵沟壑区退耕地自然恢复草地的演替,依次经历猪毛蒿群落→赖草群落→长芒草群落、铁杆蒿群落、达乌里胡枝子群落→白羊草群落。随着退耕地植被恢复的不断进行,Gleason指数、Margalef指数等丰富度指数以及群落Pielou指数,都呈现出先减小后增大的趋势,Simpson指数在演替初期及平衡阶段较大,群落生态优势度与物种丰富度的变化趋势相反。在群落的演替过程中,土壤有机质、全N、有效N和速效K的含量不断增加,土壤pH值和速效P含量不断减小,土壤表层密度变小,孔隙度变大。A层土壤全N、有效N含量、土壤pH值和C层土壤全N含量与物种丰富度呈显著正相关,A、C层土壤有机质含量和B层土壤速效K含量与其关系相反;B层土壤速效P的含量与群落生态优势度呈显著正相关;A、B层土壤速效K含量与植被群落盖度呈正相关关系,B层土壤速效P含量与其关系相反。

黄土丘陵沟壑区城市森林生态网络体系建设——以延安市为例

以延安市为例对黄土丘陵沟壑区城市森林生态体系建设进行了分析,提出从处于不同空间格局的市区中心、城郊结合部、郊区农村的社会功能、人为活动影响、生态条件等方面的差异出发,城市森林建设从市区中心到郊区应建立3个绿化生态圈,第一圈是城市防污调气美化生态圈,第二圈是近郊美化、防护、农林果生产带生态圈,第三圈是远郊水源涵养、水土保持、风沙防护、林果生产林生态圈。

Magnitude-frequency relationship of debris flows in the Jiangjia Gully, China

The magnitude-frequency(MF) relationship of debris flows is the basis for engineering designs and risk quantification. However, because of the lack of debris flow monitoring data, research progress in this area has been relatively slow. The MF relationship of debris flows in Jiangjia Gully, Yunnan Province was evaluated based on a regression analysis of 178 debris flow events that occurred from 1987-2004. The magnitude-cumulative frequency(MCF) relationship of the debris flows in the Jiangjia Gully is consistent with the linear logarithmic transformation function. Moreover, observed data for debris flows in Hunshui Gully of Yunnan Province and Huoshao Gully, Liuwan Gully, and Niwan Gully of Gansu Province were used to verify the function. The results showed that the MCF relationship of highfrequency debris flows is consistent with the power law equation, although the regression coefficients in the equation are considerably different. Further analysis showed a strong correlation between the differences in the constants and the drainage area and daily maximum precipitation.

不同分辨率SRTM-DEM的数字地形分析比较研究

以通化地区为试验区,利用Arc/Info软件,将原始的SRTM数据生成等高线,再插值生成不同分辨率的DEM数据,提取了高程差、坡度、坡向、地形阴影数字地形信息,并根据D8算法,对流域信息进行提取。结果表明:不同分辨率的DEM在描述地形的整体变化上存在的差异很小,但高分辨率的DEM可以更好地反映出地形的细微变化;在水文模拟方面,流域网络的数量及沟壑密度与DEM的分辨率成正相关的关系,但由于高分辨率的DEM信息冗余,在水文模拟方面,提取流域网络的时候会出现生成伪沟谷的现象。

Effect of Terrestrial LiDAR Point Sampling Density in Ephemeral Gully Characterization

Gully erosion can account for significant volumes of sediment exiting agricultural landscapes, but is difficult to monitor and quantify its evolution with traditional surveying technology. Scientific investigations of gullies depend on accurate and detailed topographic information to understand and evaluate the complex interactions between field topography and gully evolution. Detailed terrain representations can be produced by new technologies such as terrestrial LiDAR systems. These systems are capable of collecting information with a wide range of ground point sampling densities as a result of operator controlled factors. Increasing point density results in richer datasets at a cost of increased time needed to complete field surveys. In large research watersheds, with hundreds of sites being monitored, data collection can become costly and time consuming. In this study, the effect of point sampling density on the capability to collect topographic information was investigated at individual gully scale. This was performed through the utilization of semi-variograms to produce overall guiding principles for multi-temporal gully surveys based on various levels of laser sampling points and relief variation (low, moderate, and high). Results indicated the existence of a point sampling density threshold that produces little or no additional topographic information when exceeded. A reduced dataset was created using the density thresholds and compared to the original dataset with no major discrepancy. Although variations in relief and soil roughness can lead to different point sampling density requirements, the outcome of this study serves as practical guidance for future field surveys of gully evolution and erosion.

Simulation of unmanned survey path planning in debris flow gully based on GRE-Bat algorithm

Unmanned aerial vehicle(UAV)paths in the field directly affect the efficiency and accuracy of payload data collection.Path planning of UAV advancing along river valleys in wild environments is one of the first and most difficult problems faced by unmanned surveys of debris flow valleys.This study proposes a new hybrid bat optimization algorithm,GRE-Bat(Good point set,Reverse learning,Elite Pool-Bat algorithm),for unmanned exploration path planning of debris flow sources in outdoor environments.In the GRE-Bat algorithm,the good point set strategy is adopted to evenly distribute the population,ensure sufficient coverage of the search space,and improve the stability of the convergence accuracy of the algorithm.Subsequently,a reverse learning strategy is introduced to increase the diversity of the population and improve the local stagnation problem of the algorithm.In addition,an Elite pool strategy is added to balance the replacement and learning behaviors of particles within the population based on elimination and local perturbation factors.To demonstrate the effectiveness of the GRE-Bat algorithm,we conducted multiple simulation experiments using benchmark test functions and digital terrain models.Compared to commonly used path planning algorithms such as the Bat Algorithm(BA)and the Improved Sparrow Search Algorithm(ISSA),the GRE-Bat algorithm can converge to the optimal value in different types of test functions and obtains a near-optimal solution after an average of 60 iterations.The GRE-Bat algorithm can obtain higher quality flight routes in the designated environment of unmanned investigation in the debris flow gully basin,demonstrating its potential for practical application.

Spatiotemporal variations in ecosystem services and their trade-offs and synergies against the background of the gully control and land consolidation project on the Loess Plateau,China

Studying the spatiotemporal variations in ecosystem services and their interrelationships on the Loess Plateau against the background of the gully control and land consolidation(GCLC)project has significant implications for ecological protection and quality development of the Yellow River Basin.Therefore,in this study,we took Yan'an City,Shaanxi Province of China,as the study area,selected four typical ecosystem services,including soil conservation service,water yield service,carbon storage service,and habitat quality service,and quantitatively evaluated the spatiotemporal variation characteristics and trade-offs and synergies of ecosystem services from 2010 to 2018 using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.We also analysed the relationship between the GCLC project and regional ecosystem service changes in various regions(including 1 city,2 districts,and 10 counties)of Yan'an City and proposed a coordinated development strategy between the GCLC project and the ecological environment.The results showed that,from 2010 to 2018,soil conservation service decreased by 7.76%,while the other three ecosystem services changed relatively little,with water yield service increasing by 0.56% and carbon storage service and habitat quality service decreasing by 0.16% and 0.14%,respectively.The ecological environment of Yan'an City developed in a balanced way between 2010 and 2018,and the four ecosystem services showed synergistic relationships,among which the synergistic relationships between soil conservation service and water yield service and between carbon storage service and habitat quality service were significant.The GCLC project had a negative impact on the ecosystem services of Yan'an City,and the impact on carbon storage service was more significant.This study provides a theoretical basis for the scientific evaluation of the ecological benefits of the GCLC project and the realization of a win-win situation between food security and ecological security.

黄土坡面的土壤侵蚀波动性

通过对黄土高塬沟壑区不同土地利用情况下土壤侵蚀的137Cs法研究,发现从坡顶到坡脚,土壤剖面的137Cs含量呈现强、弱交替的波动变化。通过对土壤侵蚀波动性的分析以及与其他研究成果的对比分析,发现随着坡长的增加,土壤侵蚀在坡面上总是呈现出一定的波动性,并由坡面细沟侵蚀的变化规律所决定。坡面土壤侵蚀的波动性可分为2种类型:一种是受人类活动影响较大的耕作型;另一种是受人类活动影响较少的自然型。

The morphological characteristics of gully systems and watersheds in Dry-Hot Valley, SW China

Gully systems and watersheds are geomorphic units with clear boundaries that are relatively independent of basin landscapes and play an important role in natural geography. In order to explore the morphological characteristics of gully systems and watersheds in the Dry-Hot Valley [South West(SW) China], gullies are interpreted from online Google images with high resolution and watersheds are extracted from digital elevation model at a scale of 1:50,000. The results show that:(1) There are17,382 gullies(with a total area of 1141.66 km2) and 42 watersheds in the study area.(2) The average gully density of the study area(D) is 4.29 km/km2, gully frequency(F) is 14.39 gullies/km2, the branching ratio(B) is 5.13, the length ratio(L) is 3.12, and the coefficient of the main and tributary gullies(M) is 0.06. The degree of gully erosion isstrong to extremely strong, the main development intensity of gully erosion ranges from intense to moderate, and the type of gully system is tributary.(3) The watershed areas(A) are between 0.39 and 96.43 km2, the relief ratio(R) is from 0.10 to 0.19, the circularity ratio(C) is from 0.30 to0.83, the texture ratio(T) is from 0.82 to 39.35, and the dominant geomorphological texture type is fine.(4) There is a quantitative relationship between F and D:F = 0.624 D2(R =0.84) and T is closely related to D, F, M(R2[ 0.7). A,R and C are related to M(R2[ 0.5). The development of gully systems is the result of coupling effects between multiple factors. In this area, the degree of erosion and the condition of the main and tributary gullies can be controlled by the degree of topographic breakage in the watershed, which provides some theoretical basis for the evaluation of gully erosion by the latter. In addition, the scale, relief, and shape have a significant impact on the locations of the main and tributary gullies. For tributary gullies, attention should be paid to the interception and control of runoff and sediment in the small confluence branches in order to prevent gully expansion and head advance. These features can inform the development of targeted measures for the control of soil erosion.

Effect of coir geotextile and geocell on ephemeral gully erosion in the Mollisol region of Northeast China

The unique geomorphological features and farming methods in the Mollisol region of Northeast China increase water catchment flow and aggravate the erosion of ephemeral gully(EG).Vegetation suffers from rain erosion and damage during the growth stage,which brings serious problems to the restoration of grass in the early stage.Therefore,effects of coir geotextile and geocell on EG erosion under four confluence intensities were researched in this study.Results of the simulated water discharge erosion test showed that when the confluence strength was less than 30 L/min,geocell and coir geotextile had a good effect on controlling EG erosion,and sediment yield of geocell and coir geotextile was reduced by 25.95%–37.82%and 73.73%–88.96%,respectively.However,when confluence intensity increased to 40 L/min,protective effect of coir geotextile decreased,and sediment yield rate increased sharply by 189.03%.When confluence intensity increased to 50 L/min,the protective effect of coir geotextile was lost.On the other hand,geocell showed that the greater the flow rate,the better the protective effect.In addition,with the increase in confluence intensity,erosion pattern of coir geotextile developed from sheet erosion to intermittent fall and then to completion of main rill,and the protective effect was gradually weakened.In contrast,the protective effect of EG under geocell was gradually enhanced from the continuous rill to the intermittent rill and finally to the intermittent fall.This study shows that coir geotextile and geocell can prevent EG erosion,and the effect of geocell is better than that of coir geotextile on the surface of EG.

Assessment of Factors Affecting Ephemeral Gully Development in Badland Topography: A Case Study at Garbheta Badland (Pashchim Medinipur,

Gully erosion in the Paschim Medinipur district of West Bengal, Indiahas been an issue of anxiety, formed by the amputation of soil from narrow channels through the accretion of surface runoff. Here, we attempted to investigate the erosion variability of gully in a micro catchment area, and also scrutinized the gully cross-sectional areas as distinct components of gully volumes. Twelve gullies were randomly selected in different slopes. To determine the geometric growth of the gully dimensions and soil loss, the initial length of gully, the width of the gully and depth of respective gullies was monitored in different seasons. Univariate analysis was conducted to measure the association between gully head retreat and vegetation coverage, slope, rainfall volume and runoff contributing area. We found strong and significant relation between the slope of gully head and linear retreat in the pre monsoon (p 0.008) and post monsoon (p 0.024) season respectively. Conversely, rainfall volume and gully head retreat showed a strong relationship in the pre monsoon (r = 0.80), monsoon (r = 0.66) and post-monsoon period (r = 0.94);while meager relationship was observed with rainfall intensity (r = 0.06). Results also illustrated that the overall retreat of gully head had very strong and positive relationship with the runoff contributing area (r = 0.89, p 0.001), and maximum gully erosion was observed in the monsoon period (55.67%). These results indicate that slope, rainfall and runoff contributing area have a strong positive influence on gully erosion in Paschim Medinipur district, since the initiation of the gully.

黄土高原不同类型区梯田蓄水拦沙指标的分析与确定

为客观、科学地评价水土保持措施的蓄水拦沙效益,从确定梯田蓄水拦沙指标的约定和基本原则出发,结合不同类型区的实际情况,分析确定了黄土丘陵沟壑区第1、2副区和黄土高塬沟壑区梯田在不同降水条件下、不同质量等级的蓄水拦沙指标。结果表明:1)蓄水指标最大值出现在黄土高塬沟壑区,特别是较高质量(1、2级)梯田,在丰水年份,其蓄水效益最大,并且该类型区蓄水指标值随降水条件变化的幅度最大,丘1区的亚区2,是蓄水指标最小的地区;2)拦沙指标最大值,主要在丘1区的亚区1和丘2区,尤其是丰水年份及处于平水年的1、2级梯田,其值较其他类型区大多偏大20～70t/hm2;3)高塬沟壑区的拦沙指标值最小。