Spatial and seasonal dynamics of soil loss ratio in mountain rangelands of south-western Kyrgyzstan

Vegetation cover is the main factor of soil loss prevention.The C-factor of the RUSLE(Revised Universal Soil Loss Equation) was predicted with NDVI,ground data and exponential regression equation for mountain rangelands of Kyrgyzstan.Time series of C-factor,precipitation and temperature were decomposed into seasonal and trend components with STL(seasonal decomposition by loess) to assess their interrelations.C-factor,precipitation and temperature trend components indicated significant lagged correlation,whereas seasonal components indicated more complex relations with climate factors which can be promoting as well as limiting factors for vegetation development,depending on the season.Rainy springs and hot summers may increase soil loss dramatically,whereas warm and dry springs with rainy summers can decrease it.Steep slopes indicated higher soil loss ratio,whereas flat areas were better protected by vegetation.

Effects of Soil C/N Ratio on Apple Growth and Nitrogen Utilization,Residue and Loss

Soil C /N ratio is an important influencing factor in soil nitrogen cycling. Two-year old apple trees( Borkh. cv. ‘Fuji'/Malus hupehensis) were used to understand the effect of soil C/N ratio [6. 52( CK),10,15,20,25,30,35 and 40]on apple growth and nitrogen utilization and loss by using15N trace technique. The results showed that,with the increasing of soil C/N ratio,apple shoot length and fresh weight increased at first,and then decreased; the higher apple shoot length and fresh weight appeared in C/N = 15,20 and 25 treatments,and there were no significant differences among these three treatments,but significantly higher than the other treatments. Statistical analysis revealed that there was significant difference in nitrogen utilization rate between the different treatments,the highest N utilization rate was occurred in soil C/N = 25 treatment which value was 22. 87%,and there was no significant difference between soil C/N = 25 and C/N = 20 treatments,but both the two treatments were significantly higher than the other treatments; Soil C/N = 40 had the lowest N utilization rate which value was 15. 43%,and this value was less than CK( 16. 65%). The proportion of plant absorption nitrogen from fertilizer was much higher when the value of soil C/N ratio in the range of 15- 25,but the percentage of plant absorption nitrogen from soil was much higher when the soil C/N ratio was too low( < 15) or high( < 25). Amount of residual nitrogen in soil increased gradually with the soil C/N ratio increasing,the amount of residual nitrogen in C/N = 40 treatment was 1. 32 times than that in CK. With the increasing of soil C/N ratio,fertilizer nitrogen loss decreased at first,and then increased,fertilizer nitrogen loss was the minimum in C/N = 25 treatments( 49. 87%) and the maximum were occurred in CK( 61. 54%). Therefore,regarding the apple growth and nitrogen balance situation,the value of soil C/N ratio in the range of 15- 25 would be favorable for apple growth and could increase effectively nitrogen fixed by soil,reduce nitrogen loss,and improve the nitrogen utilization ratio.

Combined Effects of Water Quality and Furrow Gradient on Runoff and Soil Erosion in North China

Irrigation-induced soil erosion seriously affects the sustainability of irrigated agriculture. The effects of irrigation water quality and furrow gradient on runoff and soil loss were studied under simulated furrow irrigation in laboratory using a soil collected from an experimental station of China Agricultural University, North China. The experimental treatments were different combinations of irrigation water salt concentrations of 5, 10, 20, and 30 mmol c L-1 , sodium adsorption ratios (SAR) of 0.5, 5.0, and 10.0 (mmol c L-1 ) 0.5 , and furrow gradients of 1%, 3%, and 5%, with distilled water for irrigation at 3 furrow gradients as controls. The experimental data indicated that total runoff amount, sediment concentration in runoff, and total soil loss amount generally decreased with increasing salt concentration in irrigation water but increased with its sodicity and furrow gradient. The effects of water quality and furrow gradient on soil loss were greater than those on runoff, and the increase of furrow gradient decreased the influence of water quality on soil loss. When the salt concentration increased from 5 to 30 mmol c L-1 at SAR of 10.0 (mmol c L-1 ) 0.5 , total runoff amount, sediment concentration, and total soil loss amount decreased by 3.89%, 52.1%, and 53.92%, and 10.57%, 38.86%, and 42.03% at the furrow gradients of 1% and 5%, respectively. However, they respectively increased by 3.37%, 45.34%, and 55.36%, and 3.86%, 10.77%, and 13.91% when SAR increased from 0.5 to 10.0 (mmol c L-1 ) 0.5 at the salt concentration of 5 mmol c L-1 . Irrigation water quality and furrow gradient should be comprehensively considered in the planning and management of furrow irrigation practices to decrease soil loss and improve water utilization efficiency.

Estimation of soil erosion and sediment yield in Wadi El Hachem watershed(Algeria)using the RUSLE-SDR approach

One of the most common types of soil degradation is water erosion.It reduces soil quality at the erosion site and may cause sedimentation issues at the deposition site.This phenomenon is estimated using a variety of models.The Revised Universal Soil Loss Equation(RUSLE)model is the most often used,due to its consistence and low data requirement.It is useful for estimating annual soil loss at the watershed scale.To investigate the relationship between soil erosion and sediment deposition,the combined RUSLE and Sediment Delivery Ratio(SDR)models are used.The Wadi El Hachem watershed is a coastal and mountainous Mediterranean basin with rugged topography and high degree of climatic aggressiveness.Both of these characteristics can have an immediate effect on soil erosion and sediment yield.This research includes estimating the Average Annual Soil Loss(A)and Sediment Yield(SY)in the Wadi El Hachem watershed,mapping different RUSLE factors as well as A and SY,and studying the influence of rainfall erosivity(R)on A and SY in dry and rainy years.The A results vary from 0 to 410 t·ha^(-1)·yr^(-1)with an annual average of 52 t·ha^(-1)·yr^(-1).The Renfro's SDR model was selected as the best model for estimating SY,with standard error,standard deviation,coefficient of variation,and Nash–Sutcliffe efficiency(NSE)values of 0.38%,0.02,0.07%,and 1.00,respectively.The average SY throughout the whole watershed is around 27 t·ha^(-1)·yr^(-1).The SY map for the entire Wadi El Hachem watershed revealed that sediment production zones are mainly concentrated in the Northeast of the basin,at the basin’s outlet,and in the tributaries of the dam.The simulation results of soil loss and sediment yield in dry and rainy years revealed that R is one of the main factors affecting soil erosion and sediment deposition in the Wadi El Hachem watershed.The mean difference in R factor between dry year and rainy year is 671 MJ·mm·ha^(-1)·h^(-1)·yr^(-1).As a result of this fluctuation,the soil loss and sediment yield have increased by 15 and 8 t·ha^(-1)·yr^(-1),respectively.The results of this research can be used to provide scientific and technical support for conservation and management strategies of the Wadi El Hachem watershed.

西安市生产建设项目水土流失评价

[目的]探明西安市城市生产建设项目水土流失特征及不同水土保持措施效应,进而为改善西安市水土流失环境、制定更加精确有效的政策及措施提供科学依据。[方法]以西安市2022年84个生产建设项目为例,构建包含水损失比、土壤侵蚀比和绿地比3个指标在内的城市生产建设项目水土流失评价体系,采用TOPSIS法对不同项目水土流失风险进行评估。[结果]①城市生产建设项目的地表变化主要以农村宅基地、草地、空闲地和耕地向建设用地转变,其中,以农村宅基地的转出为主,约占总转变面积的70%。②83%的生产建设项目绿地比有所增加;61%的生产建设项目径流损失呈现减少趋势并表现为:新建房地产<商业服务<教育医疗<市政设施<城中村改造项目;54%的生产建设项目土壤侵蚀风险降低,并在耕地、草地、空闲地中新建项目减轻土壤侵蚀的程度尤为突出,而城中村改造会加剧区域土壤侵蚀程度;所有项目的水损失量平均减少3.58×10^(4)m^(3),年土壤侵蚀量平均减少了169.05 t。③西安市生产建设项目水土流失风险可划分为高、中等、较低、低4个等级。低和较低等级项目占总数的69%并以城中村改造类项目为主;高风险等级项目均为占用草地项目。[结论]西安市生产建设项目的水土流失防治效果显著,但仍有较大提升空间,未来应进一步加强项目水土流失风险管理。

强漏失地层塑性混凝土防渗墙关键技术研究

混凝土防渗墙是水利水电工程、市政工程较为常见的一种地下连续墙,具有防渗性能好、结构耐久性高、能适用于各种复杂地质等优点,但是在海上抛石堤中应用防渗墙防止冷热水循环并不多见。本文重点从强漏失地质条件下的施工工艺质量控制和塑性混凝土工作性能方面研究塑性混凝土防渗墙施工关键技术,解决了防渗墙在强漏失地层易漏浆、两侧水压不均衡易塌孔、塑性混凝土工作性能不能满足设计及施工要求的难题,给类似工程提供了经验,具有较高的推广价值。

秸秆覆盖对三峡库区坡面侵蚀的影响

[目的]分析农作物秸秆不同覆盖处理对坡面产流、产沙影响,为三峡库区坡耕地水土保持措施优化提供技术支持。[方法]利用人工模拟降雨技术,分析了5种不同雨强下不同秸秆覆盖处理的径流、泥沙过程。[结果]坡面覆盖秸秆能推迟坡面初始产流。在小雨强时,秸秆覆盖推迟初始产流显著,但随着雨强的增加,推迟初始产流的作用降低。在坡面下坡段覆盖秸秆推迟初始产流效果优于在坡面上坡段覆盖秸秆。对于产流产沙而言,在坡面上坡段覆盖秸秆与无覆盖差异不显著,但在坡面下坡段覆盖秸秆时径流模数和侵蚀模数为无覆盖的61.57%~69.1%和14.54%~18.31%,且减少地表径流和泥沙流失效果优于在坡面上坡段覆盖。秸秆覆盖后土壤流失比（SLR）介于0.022~0.611之间,且随着覆盖率的增加而降低,在坡面下坡段覆盖秸秆SLR值在上坡段的1/4。[结论]合理选择农作物秸秆在坡面覆盖的坡位及覆盖度,能有效降低坡面产流与侵蚀产沙,产生较好的水土保持效应。

黄土高原土壤侵蚀作物覆盖因子计算

土地利用方式以及不同农作物对土壤流失有明显的影响 ,定量评价不同作物在土壤流失中的作用 (作物覆盖因子 )是土地利用和水土保持规划的重要依据。研究的目的在于计算黄土高原主要农作物不同生长阶段的土壤流失强度与裸露地的比率 ,为计算土壤侵蚀作物覆盖因子应用。通过对甘肃天水和陕西安塞水土保持试验资料的分析 ,计算了 7种主要作物 6个农作期的土壤流失比率表 ,并对黄土高原 7种作物覆盖因子进行了计算 ,其值在 0 .2 3～ 0 .74之间 ,按此方法计算的作物覆盖因子值与观测多年平均土壤流失比率基本一致。但该方法的优势在于可以根据土壤流失比率表和不同的降雨侵蚀力分布曲线计算不同地区的 C值 。

川中紫色土区小流域土地利用与土壤流失关系

根据长江上游水土流失重点防治工程总结报告,建立小流域土壤流失量、轻度以上侵蚀土地面积与农地、林地、荒地、其他用地面积无截距多元回归模型,以及小流域土壤流失量与不同侵蚀强度土地面积无截距多元回归模型,分析不同类型土地的侵蚀模数、土壤流失率、土壤流失比、土壤流失面积比,不同侵蚀强度土地侵蚀模数、土壤流失比。结果表明:(1)农地、林地、荒地、其他用地的土壤侵蚀模数分别为2353、2319、12162、-2750t/km2·a;前三者的土壤流失比分别为56%、25%、19%,水土流失的首要用地类型是农地,但在个别小流域,林地或荒地也会是产生土壤流失的首要用地类型,其他用地对土壤流失起到抑制作用;(2)农地、林地、荒地的土壤流失率分别为52%、34%、100%,土壤流失面积比分别为72%、16%、12%,农地流失面积比远高于其他用地类型,但在个别小流域,林地流失面积比大于农地;(3)无明显侵蚀、轻度侵蚀、中度侵蚀、强度以上侵蚀土地土壤侵蚀模数分别为-481、2500、484、8068t/km2·a;轻度侵蚀、中度侵蚀、强度以上侵蚀土地土壤流失比分别为8%、33%、59%,强度侵蚀土地是水土流失的主要来源。

黄土高原不同植被类型与降水因子对土壤侵蚀的影响研究

根据辛店沟 195 5年到 195 9年坡面径流小区的观测资料 ,分析了不同植被 (高粱豇豆、苜蓿、草木樨 )被覆度与降水 (包括雨量 (P)、雨强 (I)以及 PI乘积 (PI30 ) )与侵蚀速率的关系。结果表明土壤侵蚀速率随雨量 ,雨强及PI乘积的增加呈幂函数增加 ,但随被覆度的增加呈下降趋势。在 PI30 相同时 ,不同植被对土壤侵蚀速率的影响也不同。应用 U SL E(The U niversal Soil L oess Equation)分别模拟了三种不同植被被覆度与降水因子对土壤侵蚀的关系方程和辛店沟全流域的水土流失方程 ;

高原湖相泥炭土渗透特性研究及机制分析

为明确高原湖相泥炭土渗透特性并建立渗透模型,采用固结-渗透联合试验装置对取自6个场地20余组土样天然状态及一维压缩过程中渗透系数进行测定,并分析了加载时长、应力水平以及烧失量、残余纤维含量等因素对其渗透性的影响。试验结果表明:分别加载条件下,泥炭土渗透系数k_v随加载时长T增大而减小并趋于稳定,稳定时长在10 d左右;分级加载条件下,k_v随固结应力σ′_v的增大呈非线性减小,k_v-vlgσ′关系曲线为反S型;高原湖相泥炭土渗透模型可用e-lgk_v表示,其渗透指数C_k与初始孔隙比e_0满足关系式C_k=0.25e_0;初始渗透系数k_v0和烧失量iw、残余纤维含量w_f及e_0关系较为离散,C_k和w_i、w_f及初始含水率w_0有一定的正相关性。通过电镜扫描试验,从土中孔隙特征角度探讨了高原湖相泥炭土渗透特性的机制。

红壤坡地侵蚀定位土芯Eu中子活化示踪研究

利用野外人工模拟降雨和径流小区观测相结合的方法,研究了Eu定位土芯的布设、取样和分析方法.结果表明,Eu定位土芯中子活化分析技术可以准确测定不同地形、部位土壤侵蚀量.利用Er-Es的经验模型可以描述坡面单位面积流失量的变化趋势,预测坡面土壤流失量,最大误差为7.671t/hm2.不同土地利用方式下坡面泥沙的输移比(SDR)也不相同.顺坡种植作物后,泥沙输移比(SDR)与休闲裸坡地相比减少了30%左右,从而使植被覆盖下坡面泥沙流失减少.

坡地土壤侵蚀与养分流失过程的研究

本文采用人工降雨室内试验,研究了坡地土壤侵蚀与有机质、全氮和有效磷养分的流失过程。坡度、雨强对其流失过程的影响;比较分析了裸露坡地及沙网覆盖两种处理的土壤侵蚀与养分流失过程。结果表明:随坡度,雨强增大,养分流失量也增加;试验小区覆盖纱网消除雨滴动能后,土壤养分流失量比裸露坡地减少60%左右;养分流失量与土壤流失量呈正相关,多数泥沙样中有效养分的含量高于土壤中养分含量,尤以有效磷更为显著。

川中丘陵小流域水土流失特征与调控研究

通过１９８８～１９９５年对响水滩等小河站和因子径流场的监测，研究了小流域水土流失的时空分布，重新评估了流域侵蚀模数，指出前人研究结果与目前川中区小流域侵蚀情况不相吻合；确认坡地壤中流损失为本区径流损失的重要途径；初步探讨了小流域悬推比与输移比等输沙特性；并认为在逐宁组地区，裸岩侵蚀是流域的主要侵蚀源，坡耕地为主要输沙源；研究提出了农耕地治理的调控措施及其适宜范围。

不同沙土配比对盆栽平邑甜茶的生长及^(15)N吸收、利用和损失的影响

以当年生盆栽平邑甜茶为试材,应用15N同位素示踪技术研究不同沙土配比(不加沙、沙/(沙+土)=20%、40%、60%、80%、纯沙)对植株的生长及15N吸收、利用和损失的影响。结果表明:不同的沙土配比处理,平邑甜茶植株具有不同的生长状况及氮素吸收、利用和损失。沙土配比20%处理的植株生长量(株高、茎粗和总干重)最大(37.54 cm,3.457 mm和16.20 g),60%处理的全氮和15N吸收量最大,分别为189.31,32.39 mg,20%～60%处理下的生长量与氮素吸收、利用要显著高于不加沙和高沙处理(沙土配比>60%)。各处理的Ndff值和15N分配率均为地上部>地下部,20%～80%处理的植株各部分Ndff值随沙土配比的增大而增大。土壤中15N残留量与土壤沙土配比大小呈负相关,随着沙土配比增大,氮素总损失呈现增大的趋势。平邑甜茶植株生长和养分吸收、利用与土壤质地密切相关,适宜的沙土配比有利于植株的生长和氮素吸收、利用,较高的沙土配比加剧了土壤氮素损失。

天津地面沉降区土水比论述

天津市地面沉降分布广,沉降速率大。本文针对当前地面沉降研究和防治过程中所遇到的勘查资料严重缺乏、禁采难以全面实现等难题,提出了土水比指标量。通过概念分析和对多年数据的分析,认为土水比可以检验地下水开采量数据的统计精度,指示地下水资源补给及土层释水条件,并表明沉降的严重程度,反映地下水资源的保障程度。建议在沉降防治工作中,以土水比作为指标,通过相关分析模型来制定压采量。

植大豆对坡耕地径流侵蚀产沙的影响

作物是坡耕地最重要的地被物,为了解作物覆盖下坡面土壤侵蚀的发生发展,以大豆(Glycine max)作物为对象,采用人工模拟降雨方法,对大豆不同生育期坡面的产流产沙进行研究。结果表明,与裸地相比,大豆在其全生育期内平均可减少径流量31.43%,减少土壤流失量54.84%。大豆覆盖下坡面产流产沙量随大豆生长逐渐降低,其产流产沙过程的波动性逐渐降低并趋于稳定。大豆植株的存在可使坡面稳定入渗速率较裸地平均提高了约109%,有效增强了坡面土壤的入渗能力。通过对坡面土壤流失比率的计算,表明种植大豆条件下的土壤流失比率由幼苗期的0.79降低至始粒期的0.24,其与大豆叶面积指数呈指数函数关系。大豆对坡面土壤侵蚀具有较强的抑制作用,且对泥沙的拦截作用强于对径流的拦蓄作用。

土壤C/N对苹果植株生长及氮素利用的影响

土壤C/N是土壤氮素循环的重要影响因素。本研究以2年生＂富士＂/平邑甜茶为试验材料,应用15N示踪技术研究了不同土壤C/N[6.21（CK）、10、15、20、25、30、35和40]对苹果植株生长及氮素利用和损失的影响。结果表明：随着土壤C/N比值的逐渐增大,苹果新梢长度和植株鲜重均呈先升高后降低的变化趋势,C/N=15、20和25的3个处理苹果新梢长度和植株鲜重最大,三者间无显著差异,但均显著高于其他处理。不同C/N处理间植株15N利用率存在差异,土壤C/N=25时,植株15N利用率最大,为22.87%,与C/N=20的处理间无显著差异,但两者均显著高于其他处理;土壤C/N=40时,植株15N利用率最低,仅为15.43%,低于CK处理的16.65%。土壤C/N处于15~25时,植株吸收的氮素来自于肥料氮的比例较高;而土壤C/N较低（〈15）或太高（〉25）时,植株吸收的氮素来自于土壤氮的比例较高。土壤氮素残留量随土壤C/N的增大逐渐增加,C/N=40处理的土壤氮素残留量是CK的1.32倍。随着土壤C/N比值的逐渐增大,肥料氮损失量呈先减少后增加的变化趋势,以C/N=25时最少,仅为施氮量的49.87%,而对照最大,为61.54%。因此,综合土壤C/N对苹果植株生长及氮素平衡状况来看,土壤C/N为15~25时,能促进植株的生长发育,降低氮肥损失,提高肥料利用率。

植被类型对黄土高原土壤侵蚀的影响研究

根据辛店沟1955～1959年坡面径流小区的观测资料,分析了不同植被(高粱豇豆、苜蓿、草木樨)被覆度对土壤侵蚀的影响,主要为被覆度(C)与侵蚀速率的关系。结果表明土壤侵蚀速率随被覆度的增加呈指数下降。不同植被对土壤侵蚀速率的影响不同,应用USLE(The Universal Soil Loess Equation)分别模拟了3种不同植被被覆度对土壤侵蚀的关系方程,探讨了植被被覆度对土壤侵蚀的作用规律。

基于RUSLE和SDR的香溪河流域土壤流失脆弱区识别

基于修正的通用土壤流失方程RUSLE和分布式泥沙输移比SDR函数,构建了由降雨侵蚀力因子、土壤可蚀性因子、坡度坡长因子、植被覆盖因子和泥沙输移因子组成的流域土壤流失脆弱性评估模型。针对三峡库区香溪河流域,在GIS和RS技术支持下,利用流域降雨、土壤类型分布、DEM及NDVI数据,评估了流域土壤流失脆弱性并对其进行了区划,识别出了香溪河流域内对于土地利用和水土保持等人类活动更为敏感的土壤流失脆弱区。结果显示,香溪河流域土壤流失脆弱区面积为326.33 km2,占流域总面积的10.53%;5个子流域中,土壤流失脆弱区分布比例从高到低依次为:湘坪河子流域、古夫河子流域、湘坪河口—峡口区间、峡口以下区域和高岚河子流域,其中前2个子流域土壤流失脆弱区分布比例超过全流域的平均值。研究结果可为香溪河流域土地利用方式的调整和水土保持提供科学依据。