呼伦贝尔草原切沟形态发育特征与体积估算模型

呼伦贝尔草原是中国北方极其重要的生态屏障,过度放牧已导致该区域切沟不断形成和发育,加剧了草场退化和破碎化,但尚未见有关该区切沟侵蚀研究的报道。因此,该研究通过对呼伦贝尔草原核心区136.22 km²区域内所有切沟进行逐条野外实测,获取了切沟长度L、宽度TW、深度D、面积A、体积V、横断面积A_c、宽深比R_WD、长宽比R_LW等形态参数,研究了切沟形态特征及其体积估算模型。结果表明：切沟数量密度和沟壑密度G_D分别达1.15条/km²和0.27 km/km²,0.94‰的草场因沟蚀而消失。切沟整体表现为狭长、宽而浅形状,8个切沟形态参数的变化呈中、强度变异,平均L、TW、D、A、V、A_c、R_WD、R_LW分别为231.80 m、3.12 m、1.26 m、820.49 m²、1099.46 m³、3.39 m²、2.68、101.93,坡面沟和谷底沟的数量比为11:9,谷底沟8个形态参数是坡面沟的1.06～4.78倍。切沟TW、D、R_WD接近正态分布,L、A、V、A_c、R_LW呈偏左分布,这8个形态参数分别主要分布在1.0～4.0 m、0.5～1.2 m、1.0～3.5、0～200 m、100～600 m²、30～300 m³、0～3 m²、3.55～60范围,占比分别为77.9%、68%、77.9%、63.5%、56.4%、46.8%、57.7%、46.1%;沟蚀强度显著受地形影响,G_D和地表割裂度G_LD随坡度先增大后减小,9°时沟蚀最严重,阳坡和半阳坡G_D、G_LD分别是阴坡和半阴坡的4.3倍、3.7倍;V-A幂函数关系预测切沟体积优于V-L幂函数关系,建议作为呼伦贝尔草原切沟体积估算模型。研究可为呼伦贝尔草原沟蚀防治及草原可持续利用提供科学支撑。     

紫色丘陵区小流域土壤侵蚀产沙空间分布的 137Cs法初步研究

该文通过紫色丘陵区响水滩小流域不同土地利用类型、不同坡度和坡长、不同地貌部位土壤剖面中 ¹³⁷Cs含量的测定与分析，对其侵蚀空间分布进行了估算。研究结果表明：该流域 ¹³⁷Cs含量的背景值为1870 Bq/m²；流域内坡耕地、林地的年平均侵蚀强度分别为4468、1759 t/(km²·a)；土壤侵蚀量与坡长、坡度均指数相关；丘顶、丘坡和鞍部的年平均侵蚀强度分别为2125、4676、3625 t/(km²·a)。结果表明土地利用类型、坡长和坡度、地貌部位对土壤侵蚀量影响很大，坡耕地是该流域泥沙的主要来源。     

塔里木河下游植被耗水量的时空演变

[目的] 分析塔里木河下游天然植被耗水量,为其生态修复研究提供科学指导。[方法] 基于Landsat系列影像和日尺度气象数据,采用改进的Penman-Monteith公式法,在30 m空间分辨率上,对生态输水以来大西海子水库至阿拉干断面间植被耗水量的时空演变趋势进行了分析。[结果] ①研究区天然植被耗水量时空分布存在着明显的梯度化差异,高耗水区主要分布在主河道沿线及自然漫溢区,下游植被耗水量整体偏低,年内主要集中于植被生长中期。②2000—2020年天然植被平均耗水量为1.90×10⁸ m³/a,并以2.44×10⁷ m³/5 a的速率增长;同期大西海子水库至阿拉干断面间的河水消耗量为2.79×10⁸ m³/a;植被耗水量占河道消耗水量的68.23%,二者随输水进程均呈上升趋势。③天然植被面积以12.37%/5 a的速率增长,耗水量以12.82%/5 a的速率增长,植被面积与耗水量增长速率相匹配,天然植被的修复对输水的响应较为积极,继续输水仍会促进植被的快速恢复。[结论] 截至2020年,经过21 a的生态输水,塔里木河下游天然植被得到明显改善;但受既有输水方式固化的影响,加大了水面及浅埋深区的无效蒸发,生态耗水的时空分布仍存在优化的可行性和必要性。     

黄土丘陵区典型沟道侵蚀诱发的CO2通量估算

以黄土丘陵区典型侵蚀沟道为对象,基于沟道剖面有机碳和¹³⁷Cs数据,采用碳库重分布模型估算了典型沟道侵蚀诱发的CO₂通量,并通过检验模型预测效率、解析影响因子,提出了模型校正的思路。结果表明:(1)在长期侵蚀作用下,沟道侵蚀区和沉积区均表现为剧烈的侵蚀效应,侵蚀区侵蚀速率介于30.99~46.44 mm/a,沉积区侵蚀速率介于34.20~37.88 mm/a,沉积区土壤流失速率略小于侵蚀区;(2)碳库重分布模型估算显示,侵蚀区与沉积区均表现为较强烈的碳源效应,侵蚀区CO₂通量介于18.41~28.44 g/(m²·a),沉积区CO₂通量介于22.19~29.25 g/(m²·a);(3)侵蚀部位、土壤容重、有机碳含量、侵蚀量、沟道平均坡度、植被地上部与地下部生物量共同解释了碳库重分布模型预测效率的变异特征(R²=0.68),其中侵蚀部位、侵蚀量、有机碳含量、土壤容重、植被地下部对预测效率有强驱动效应;(4)引入被忽略的植被新输入有机碳库参数,有望校正碳库重分布模型,提升模型预测效率。该研究结果明确了碳库重分布模型在沟道侵蚀区相比沉积区有更高的CO₂通量预测效率,为进一步提高模型的预测精度,可以考虑引入植被输入有机碳库作为校正参数。     

近20年来西藏地区NPP时空变化及影响因素

[目的] 探究西藏地区植被净初级生产力(net primary productivity， NPP)时空变化规律以及与影响因素之间的关联，为该区绿色生态建设和国土资源开发提供科学依据。 [方法] 利用MOD17A3 NPP数据、气象数据和植被类型空间分布等数据，采用趋势分析、偏离分析、相关性分析法和地理探测器等方法，对西藏地区2000-2020年的NPP时空格局及影响因素进行分析。 [结果] ①西藏地区2000-2020年NPP总体呈增长趋势，均值为137.36 g/(m²·a)，波动范围为128.04～148.06 g/(m²·a)，总体分布具有明显的空间异质性，呈东南高西北低的趋势； ②不同植被类型的年均NPP差异明显，其中阔叶林最高，为1107.09 g/(m²·a)，荒漠最低，为29.76 g/(m²·a)，按NPP均值大小顺序排列为：阔叶林＞栽培植被＞针叶林＞灌丛＞草甸＞高山植被＞草原＞荒漠； ③NPP与气温和降雨均存在明显相关性，其中NPP与降雨多呈负相关，与气温多呈正相关； ④各影响因子对NPP空间分异性解释力依次排列为：降雨量＞海拔＞气温＞坡度＞植被类型＞土地利用类型，自然因子对NPP的影响力强于人为因子，双因子交互作用影响力强于单因子。 [结论] 西藏地区水热条件分布不均，NPP空间分布差异较大，整体生态系统呈改善趋势，局部生态系统较脆弱。     

甘肃省小陇山林区降雨型浅层滑坡汇水面积-坡度关系及其影响因素

沟头发生侵蚀的地形临界模型可有效预测侵蚀沟的形成条件,浅层滑坡失稳形成的洼地也是沟头形成的方式之一。为探究浅层滑坡临界起动模型的特点,以甘肃省天水市小陇山林区的降雨型浅层滑坡为研究对象,运用汇水面积-坡度关系,构建临界起动模型,与黄土高原典型侵蚀沟(浅沟、切沟)的临界起动模型进行对比分析,并探讨土地利用类型、植被类型和土壤质地对该模型的影响。结果表明:(1)浅层滑坡临界起动模型为S=3.50A_s^-0.34,其侵蚀阈值为3.50,大于黄土高原典型浅沟(0.96)和切沟(1.54)的侵蚀阈值。研究区浅层滑坡一般发生于土层较薄的陡坡地带,其平均坡度(S=1.26)大于浅沟(S=0.35)与切沟(S=0.46),单位汇水面积(A=89.08 m²/m)小于浅沟(A=920.93 m²/m)和切沟(A=1 129.82 m²/m)。(2)汇水面积与坡度平方的乘积(AS²)代表了沟头产生侵蚀的能量指标值。研究区浅层滑坡AS²值在269.1~5 703.2 m²,平均值为1 772.97 m²,黄土高原浅沟AS²值在4.74~892.66 m²,切沟在41~814 m²,启动能量值方面,浅沟<切沟<浅层滑坡。(3)土地利用类型、植被类型和土壤质地通过影响土壤的抗冲力、渗透性和黏粒含量,从而对浅层滑坡的起动难易程度产生影响。在不同的土地利用方式中,农地最易发生侵蚀,其次是林地。油松林附近浅层滑坡的抗侵蚀能力高于日本落叶松林。研究结果为探究浅层滑坡的起动条件提供理论依据。     

杨粮间作行距对小麦生长及产量的影响

对杨粮间作条件下小麦生长结果研究表明，杨树间作行距与土壤水分呈反比关系，即3～15m的行距范围内林木行距每扩大1m，土壤季平均含水量则降低1.0%，证明间作可有效减少土壤水分损失；同时林木行距与小麦叶绿素含量呈反比，说明一定程度的林木遮荫可提高小麦叶绿素含量。试验表明，小麦光合作用速率和蒸腾速率与林木行距呈正比，林木行距每增加1m，小麦的光合速率和蒸腾速率分别提高1.3μmol/m²·s和0.2μmol/m²·s，说明林木行距过小，则影响作物的光合作用，进而影响小麦的生物量和产量。通过计算，在该杨树4年林龄条件下小麦取得最大产量的行距为21～22m。     

黄土高原丘陵沟壑区淤地坝的淤地拦沙效益分析

根据皇甫川、窟野河、佳芦河、秃尾河、大理河5条支流内黄丘区小流域淤地坝的调查资料，分析了淤地坝单坝的淤积速度、拦沙指标和拦沙效益，以及与其影响因素之间的关系。研究结果表明，黄土高原丘陵沟壑区淤地坝的淤地拦沙效益与淤地坝的规格、流域的侵蚀产沙特征有着密切的关系。淤地坝的平均淤积库容在0.9～2.4万m³之间，平均淤地面积在0.14～0.45 hm²之间，与坝高、坝控面积、侵蚀产沙模数和泥沙粒径成正比；拦沙指标变化在500～760万t/km²之     

采煤沉陷对土壤侵蚀与土地利用的影响预测

中国新建和将建的煤矿区主要集中分布在生态脆弱的晋、陕、蒙区,生态环境压力大。正确预测采煤沉陷引发的人为加速土壤侵蚀与土地利用变化,可为生态脆弱煤矿区的生态恢复和重建提供依据。该文采用RS、GIS为手段进行信息提取和图形叠加,结合类比法和专家咨询法等,研究了山西大同塔山矿采煤沉陷引发的土壤侵蚀和土地利用的变化。结果表明：1)采煤后88.80%土地发生不同程度的沉陷。2)沉陷后土地年土壤侵蚀总量增加42.32～79.05万t,单位面积年侵蚀量增加了246.01～464.56 t/km²,侵蚀模数为2321.78～4335.64 t/(km²·a),部分地块沉陷后土壤侵蚀强度上升了一个等级。3)地表移动变形产生的裂缝、陷坑、塌方或小滑坡等,使农用地被分割而破碎、地块变小,其中,沉陷后旱地最小斑块面积为7.72 m²,有林地最小斑块面积为72.95 m²,灌木林地最小斑块面积为6.71 m²,疏林地最小斑块面积为75.79 m²,中覆盖度草地最小斑块面积为14.81 m²,低覆盖度草地最小斑块面积为9.44 m²。局部裂缝密集带,可造成土地毁坏。4)除工交用地和居民点用地外,原地貌沉陷后土地利用率,较原地貌降低10%的比例为14.05%,降低10%～20%(含10%)的比例为85.18%,降低20%(含20%)以上的比例为0.77%。     

灌溉对大麦/玉米带田土壤硝态氮累积和淋失的影响

以甘肃省河西走廊灌区为试验地点，分别在0、150、300 kg/hm²氮水平和816、1632 m³/hm²灌水量下，对3次灌水前、后大麦/玉米带田0～200 cm土壤NO^-₃-N含量变化和灌水后135 cm处渗漏液NO^-₃-N浓度进行了测定。结果表明：灌水明显影响土壤硝态氮累积量，随灌水次数增加，土壤硝态氮累积量降低，而且在高灌水条件下土壤硝态氮累积量变化比低灌水量时大。从渗漏液硝态氮浓度来看，大麦带和玉米带都是以第1次灌水最高，浓度分别为8.04～17.21和3.30～14.57 mg/L。3次灌水土壤硝态氮淋失量，玉米带以N 150 kg/hm²和灌水量1632 m³/hm²最高，平均为4.31 kg/hm²；大麦带以N 150 kg/hm²及灌水量1632 m³/hm²和N 150 kg/hm²及灌水量816 m³/hm²比较高，平均为6.82 kg/hm²。     

Gully development in the Moldavian Plateau of Romania

Gully erosion has been recognized as an important environmental threat in the Moldavian Plateau of Eastern Romania. The main objective of this study was to define the process-based gully development by providing quantitative information from long-term field measurements in small catchments.Three main areas of monitoring gullies were explored: aerial photographs of flights in 1960 and 1970, classical leveling and repeated survey through a particular close stakes grid after 1980. The Caesium-137 technique has been used effectively in the areas of deposition of gully sediments to obtain reliable information on dating specific levels of sediments and to provide chronological measures of gully development.Most of the discontinuous gullies exhibit both proper gullying, mainly if not exclusively by gully head advance, and aggradation of the gully basin floor. Results indicated that the mean gully head retreat was 0.92 m year^− 1 and the mean areal gully growth was 17.0 m² year^− 1. Both values indicate a slow erosion rate for this area. The average annual regime of gullying is pulsatory, one that is best described by great fluctuations. Conventional measurements on sedimentation over the period 1987–1997 indicate a higher rate of aggradation in the upper half of the gully floor. Information on the Caesium-137 depth profile was used to provide estimates of a mean sedimentation rate of 4.4 cm year^− 1 over the period 1963–1996 and 2.5 cm year^− 1 after 1986 for the short successive discontinuous gullies. A new classification of the discontinuous gullies based on two criteria, respectively, the field patterns and the rate of aggradation within the gully basin floor was established.For continuous gullies, linear gully head retreat, areal gully growth and eroded material rates were quantified for three periods (1961–1970, 1971–1980 and 1981–1990). Results indicate that gully erosion has decreased since 1960. This gullying decline is due to the rainfall distribution, and the increased influence of soil conservation practices. The mean gully head retreat of 12.5 m year^− 1 between 1961–1990 was accompanied by a mean areal gully growth of 366.8 m² year^− 1 and a mean erosion rate of 4168 t year^− 1. As with discontinuous gullies, continuous gullies showed pulsatory development.The critical period for gullying over 1981–1996 covers 4 months from Mid March to Mid July in an area with mean annual precipitation around 500 mm. Another main finding of this 16-year stationary monitoring was that 57% of the total gullying occurred during the cold season, with the remainder during the warm season. Of the total gully growth, 66% results from only four years (1981, 1988, 1991 and 1996), when a greater amount of precipitation fell.     

Short-term gully retreat rates over rolling hill areas in black soil of Northeast China

Soil loss has become one severe problem in black soil areas of Northeast China after several decades of cultivation. Gully erosion is one of its main components. In this study, short-term gully retreat was monitored from 5 active gullies selected in representative black soil area during April 2002 to June 2004, using differential global positioning system (GPS). With the support of geographic information system (GIS), multitemporal digital elevation models (DEM) were constructed from the data collected by GPS and then used for further analysis. This presents a new method to compute the retreat rate of gully heads and the rate of soil losses caused by gully erosion. The results indicate that the average volumetric retreat rate was 729.1 m³ year^− 1, corresponding with an average linear retreat rate of 6.2 m year^− 1 in gully head and planimetric changes of 323.6 m² year^− 1 during the two monitored years, but more erosion took place during the second and third monitored period compared to the first. The erosion by freeze thawing and snowmelt accounts for a large percent. And this will be emphasized when rainfall is added in spring. If only considering the third monitored period, the conservatively estimated retreat rate by freeze thawing and snowmelt (i.e. before rainy season) may even reach 8.6 m year^− 1 in gully head, with a volumetric rate of 120.9 m³ year^− 1 and planimetric changes of 173.6 m² year^− 1. These results reveal that gully erosion is a great threat in the study area and conservation measures are urgently needed. Based on the analysis of multi-temporal DEM, one conceptual model for gully developing in black soil of Northeast China is proposed, which is supported by the data.     

利用高分立体影像构建东北黑土山地丘陵区切沟体积估算模型

分析侵蚀沟形态特征并构建体积估算模型,对大空间尺度探究切沟侵蚀具有重要意义。该研究选取位于东北黑土山地丘陵区穆棱市的典型样区,基于WorldView-2高分立体像对影像(0.5m分辨率),利用ENVI5.3提取同分辨率DEM,选择45条切沟,在ArcGIS10.3中提取并计算切沟顶宽(TW)、底宽(BW)、沟深(D)、断面面积(CSA)、沟长(L)、面积(A)及体积(V)等参数,分析形态特征及相互关系,构建切沟体积估算模型。结果表明:1)切沟TW、BW、D、CSA、L、A及V均值分别为5.63 m、2.82 m、1.05 m、4.94 m~2、81.90 m、470.54 m~2、428.53 m~3。断面BW/TW均值为0.48,切沟以V～U型为主。TW/D全部大于1,均值为5.95,表明沟道横向侵蚀较下切侵蚀速率更快;2)切沟体积与沟长(V-L)、面积(V-A)间均有极显著幂函数关系,相比V-L关系模型,V-A关系模型具有更小的平均相对误差和更大的纳什系数,可更准确有效预测切沟体积,建议将其作为东北山地丘陵区切沟体积估算模型;3)与黄土高原及干热河谷地区相比,东北黑土区切沟体积与面积幂函数关系的指数更小,而区内山地丘陵区较漫川漫岗区更大,反映出山地丘陵区更加强烈的切沟发育状况;切沟形态特征影响V-A模型构建的精度,建议将狭长度(L/TW)作为切沟分类指标构建切沟体估算模型。研究结果可为东北黑土山地丘陵区大空间尺度切沟侵蚀的定量模拟提供方法和依据。     

A method for dendrochronological assessment of medium-term gully erosion rates

A method based on dendrochronology to estimate gully erosion rates was developed as an alternative of traditional methods for assessing medium-term gully retreat rates, such as field monitoring of headcuts or aerial-photo interpretation of gully retreat. The method makes use of trees or parts of a tree affected by gully erosion revealing information on the history of the erosion process by datable deviations of their normal growth pattern, hence defined as ‘datable objects’. These include roots exposed by erosion; browsing scars made by ungulates on exposed roots or on above-ground parts of fallen trees; exposed and dead root ends; root suckers; stems, branches and leading shoots of fallen trees; and a sequence of trees within a gully. The method is based on the differentiation between three main conditions depending on the relation between the dynamics of the datable object (part of the tree) and the development of the gully. The first condition implies that the datable object was created before erosion of the gully volume to be dated, e.g. exposed tree roots. According to the second condition, the datable object developed as an immediate consequence of the erosion event, e.g. growth reactions of a fallen tree. The third condition implies that the datable object was created some time after the erosion event took place, e.g. trees colonising the gully bed. Each principle has consequences for the accuracy and the correct interpretation of the estimated erosion rate, i.e. whether the true erosion rate is underestimated, exact or overestimated. In spite of methodological limitations and dendrochronological dating problems, the method was successfully applied in southeast Spain. Conservative estimations of gully-head retreat rate resulted in an average medium-term (3–46 years) value of 6 m³ year⁻¹ (n=9). For gully sidewall processes, the average minimum erosion rate per unit sidewall length amounted 0.1 m³ year⁻¹ m⁻¹ (n=9). A strong correlation was found between the headcut retreat rate (v_m(ortho), m³ year⁻¹) and the drainage–basin area (A, m²) of the gullies, expressed by v_m(ortho)=0.02A^0.57 (R²=0.93, n=9). Comparing the findings from this study with those obtained by short-term headcut retreat monitoring suggests a high reliability of the estimated retreat rates, supporting the applicability of the developed dendrochronological method.     

使用高分遥感立体影像提取黄土丘陵区切沟参数的精度分析

为了研究高分立体像对测量黄土丘陵区切沟参数的适用性,选取陕北黄土区合沟小流域,以三维激光扫描全站仪获取的数据为参照值,分析使用GeoEye-1高分遥感立体像对测量切沟参数的精度,得到如下研究结果.1)刃沟面积、周长、沟长和沟宽等线状和面状参数平均测量误差分别为3.58 m2,0.55 m,0.13m和-0.10 m,其中面积、周长和沟长的百分误差主要集中在5％以内,沟宽百分误差主要分布在10％以内.2)切沟三维参数沟底宽、最大沟深、平均沟深的平均测量误差分别为-0.67、0.14和-0.46 m.截面积和体积的平均误差分别为-6.30 m2和-54.01 m3.最大沟深的百分误差主要集中在30％以内,沟底宽、平均沟深、截面积和体积的百分误差则主要分布在50％以内;相较于三维激光扫描的切沟,立体像对提取的切沟沟底形态误差较大,主要是沟底宽和平均沟深偏小.3)切沟规模越大,切沟体积、截面积和沟底宽的测量值偏小的幅度越大.但是,切沟体积测量误差与切沟体积之间可以建立较好的线性回归模型,在缺少其他测量手段时,可以使用该模型对测量误差进行校正.总体上看,高分立体遥感为切沟线状和面状参数测量以及切沟体积测量提供了新的方法,为黄土丘陵区沟蚀监测提供了便捷、且相对可靠的数据源.     

基于Google Earth影像的横断山区沟蚀及侵蚀沟类型调查研究

[目的]探讨横断山区侵蚀沟的类型、分布特征及影响因素,为研究沟蚀对横断山区土壤侵蚀及土地退化的影响提供依据。[方法]基于Google Earth高清影像结合GIS的方法,基于可见性的基本原则,对横断山区开展侵蚀沟的抽样调查。共布设调查单元2 242个,每个单元尺寸1km×1km。[结果]共有571个调查单元发现有侵蚀沟分布,占调查单元总数的25.5%,平均沟壑密度为2.20km/km2。沟蚀在海拔低于1 500m的区域发育显著,沟壑密度随坡度增加而增长,与年降雨相关性较弱。草地是沟蚀发育的主要土地利用类型,燥红土的沟蚀分布率及平均沟壑密度显著高于其他土壤类型。通过总结国内外现有的侵蚀沟分类体系及其异同,结合调查结果,判定该次调查的横断山区侵蚀沟类型主要为切沟和冲沟(包括有泥石流事件的冲沟)。[结论]横断山区切沟和冲沟分布广泛,发育强烈,其分布受海拔、坡度、土地利用及土壤类型等因素的影响较为显著。     

东北典型黑土区侵蚀沟形态及分布特征

东北黑土区是中国最重要的粮食生产基地之一,同时也是中国四大水蚀区之一,其中沟道侵蚀是水蚀发生的主要形式,掌握东北黑土区沟道侵蚀的基本情况,剖析其形态及分布特征,对于分析东北黑土区沟道侵蚀的成因及水土流失治理至关重要。该研究以典型黑土区嫩江县为研究区域,利用航空遥感影像及1∶5万DEM对区域内侵蚀沟进行普查统计,并分析侵蚀沟的沟宽、沟长、纵比降等形态特征,以及海拔、坡度、坡向等地形因素对侵蚀沟分布的影响,为黑土区侵蚀沟的治理提供理论依据。研究结果表明:1)沟道侵蚀主要分布在丘陵区,沟道类型以切沟为主,冲沟影响面积仅次于切沟,研究区以小于500 m的侵蚀沟为主,数量及面积分别占总数的96.67%、61.99%;2)侵蚀沟的沟宽与沟长为正相关,纵比降与沟宽、沟长为负相关;3)坡向对各类型侵蚀沟的分布影响较小,坡度对侵蚀沟的分布有一定影响,细沟和浅沟主要分布在2~6°和6~15°的坡面上,而切沟和冲沟则主要分布在0~2°、2~6°的坡面上,90%以上的细沟和浅沟、80%以上的切沟、冲沟发生在耕地上;4)嫩江县冲沟地形阈值模型拟合表明嫩江县冲沟发生的临界坡度较小,较小的坡度就能对坡面形成冲刷,出现冲沟的发生发育,而模型中主导径流过程的参数数值较小,表明嫩江县冲沟的产生可能受到地下过程的影响。     

Estimating the rate and consequences of gully development,a case study of umbulo catchment in Southern Ethiopia

In southern Ethiopia wide and deep gullies are common features, significantly affecting farmers' livelihoods. Little action is being taken to address the problem despite farmers being knowledgeable about erosion and its control measures. A study was conduced to investigate the nature and rate of gully development in Umbulo catchment, southern Ethiopia, based on interviews with farmers and field measurements. The results indicated a rapid, down slope development of gullies over the last 30 years with average rate of soil loss from 11 to 30 t ha⁻¹ y⁻¹. The critical period of development of the gully system was estimated to be between 1974 and 1985, but since then the gully system has enlarged both in depth and width. Wide channels with deep, nearly vertical walls are typical. The trigger for gully initiation is believed to have been human, but the soil properties may have played an important role. Under the current situation agricultural production is unsustainable unless the gullies are controlled using integrated measures at the catchment scale. Copyright © 2008 John Wiley & Sons, Ltd.