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1.
Spatial variability of throughfall under a single tree: Experimental study of rainfall amount, raindrops, and kinetic energy 总被引：2，自引：0，他引：2
Kazuki Nanko Yuichi OndaAkane Ito Hiromu Moriwaki 《Agricultural and Forest Meteorology》2011,151(9):1173-1182
To evaluate the spatial variability of throughfall amount, raindrops, and erosivity under a single canopy during calm meteorological conditions, indoor experiments were conducted using a 9.8-m-tall transplanted Japanese cypress (Chamaecyparis obtusa) and a large-scale rainfall simulator. Drop size distribution, drop velocity, and kinetic energy of throughfall varied spatially under a single canopy as did throughfall amount and rain rate. Compared with throughfall rain rate, the variability was similar in drop size distribution, lower in drop velocity, and higher in kinetic energy. The results suggest that the spatial distribution of throughfall amount was dominated by the canopy shape and position of branches inside the canopy, and thus the spatial distribution was correlated with the radial distance from the trunk. Throughfall amount and rate were lower at the midway point between the trunk and the canopy edge. Throughfall drop size indices (drop size distribution, drop velocity, and unit kinetic energy) varied spatially while did not differ significantly. On the other hand, time-specific throughfall kinetic energy was correlated with the radial distance from the trunk. The dependence the throughfall kinetic energy on the radial distance from the trunk was dominated by the spatial distribution of throughfall amount. The trend in the spatial distribution of throughfall revealed in this study will aid in modelling canopy water processes and in predicting soil erosion on the bare forest floor. 相似文献
2.
种植大豆地表土壤溅蚀效应及其空间分布特征 总被引：4，自引：0，他引：4
为系统研究种植大豆条件下农地溅蚀速率变化特征并建立简单易用的模型,评价大豆种植对土壤溅蚀的影响,采用室内模拟降雨的方法,测定了不同降雨强度(40 mm h-1和80 mm h-1)、不同大豆生长阶段(始花期、盛花期、结荚期和始粒期)下的穿透雨强度和溅蚀速率,分析了大豆冠下溅蚀速率与叶面积指数和穿透雨强度的关系,探讨了冠下溅蚀速率的空间分布特征.结果表明:与裸地相比,在大豆全生育期,大豆冠下平均溅蚀速率在设计雨强40 mm h-1和80 mm h-1下,分别减少了62.85％和60.74％.冠下平均溅蚀速率随叶面积指数增加呈显著的增加趋势,且随降雨强度的增大而显著增加.冠下各点溅蚀速率受相应各点的穿透雨强度影响在80 mm h-1设计雨强下较为显著,随穿透雨强度的增加而增加.大豆冠下溅蚀速率的空间分布与穿透雨的分布具有一定的对应性,即冠下穿透雨较为集中的区域会在一定程度上增加溅蚀的发生,并导致冠下溅蚀速率分布不均,大豆冠下穿透雨是冠下溅蚀产生和分布的主要能量来源.该研究提出的大豆冠下溅蚀速率模型可为坡耕地土壤侵蚀防治和农田灌溉有效利用提供理论支持. 相似文献
3.
为系统测定玉米不同生长阶段冠下的溅蚀速率及其空间分布特征,采用室内人工降雨的方法,系统测定了不同降雨强度、不同生长阶段玉米冠下的穿透雨强度和溅蚀速率,分析了玉米冠下溅蚀速率与叶面积指数和穿透雨强度的关系,探讨了冠下溅蚀速率的空间分布特征。结果表明:玉米在其不同生长阶段冠下平均溅蚀速率较裸地减少了约43%～77%;冠下溅蚀速率随叶面积指数变化规律不显著,但是随降雨强度的增大而显著增加。冠下各点溅蚀速率随相应各点的穿透雨强度的增加而增加。玉米冠下溅蚀速率的空间分布与穿透雨的分布具有较好的对应关系,冠下穿透雨强度较大的区域会导致较高的溅蚀量。该研究揭示的玉米冠下溅蚀速率特征可为坡耕地土壤侵蚀防治提供理论指导。 相似文献
4.
溅蚀研究进展 总被引：6，自引：0，他引：6
溅蚀是水蚀的初始阶段,是雨滴对地表击打直接作用的结果,是一个动能减少,地表土壤颗粒发生位移的过程。溅蚀主要发生在坡面产生径流之前和刚产生径流时,是水蚀的主要形式之一。国内外学者对溅蚀的影响因素的研究主要集中在降雨特征、土壤特性以及地形因素等方面,其中主要影响因子包括:坡度、降雨特征、植被覆盖和土层结构。溅蚀量随坡度的增大逐渐增多,但是坡度超过临界坡度时,随坡度增大而减小;随降雨强度和雨滴大小增大而增大;地表植被对降雨有直接的再分配的过程,主要表现为截流、透流和干流3方面,当地表覆盖物超过1cm时,溅蚀可以完全消失;不同级配的土壤颗粒抗溅蚀能力不同,粒径在0.15mm附近的颗粒最容易被溅蚀,溅蚀同时随着土壤结皮厚度增大,土壤抗溅蚀能力增强。然而目前国内外对溅蚀的研究主要是在实验室模拟条件下完成的,较少有野外实地的研究,更缺乏在实际农业生产条件下的研究。所以需要在前人的基础上结合我国有些地方坡耕地较多的情况,在不同作物、作物生产方式和土地耕作方式等条件下,探讨坡耕地溅蚀规律。 相似文献
5.
为了探究沈阳地区天然降雨雨滴特征与产沙量的关系,在天然降雨条件下,使用滤纸色斑法计算雨滴特征,利用野外径流小区（长8 m,宽1 m）采集沙样。运用相关分析法、灰色关联分析法和模糊贴近度分析法分析了降雨强度、雨滴动能、雨滴中值粒径、雨滴终点最大速度和雨滴质量与产沙量的关系。结果表明:经过相关分析和灰色关联分析,影响坡面产沙量的顺序为降雨强度 > 雨滴动能 > 雨滴中值粒径 > 最大雨滴终点速度 > 雨滴质量,模糊贴近度分析表明降雨强度对坡面产沙量的影响最大,降雨动能其次,雨滴质量影响最小。坡面产沙量分别与降雨强度、雨滴中值粒径、雨滴动能呈幂函数关系;天然降雨雨滴中值粒径与降雨强度呈幂函数关系;雨滴中值粒径和雨滴质量是雨滴动能的主要影响因子。 相似文献
6.
为探究雨滴击溅对表层土壤结构和入渗特征的影响,揭示土壤微结构与入渗间的深层关联,以黄土高原土为对象,采用模拟降雨、同步辐射CT扫描和入渗试验,系统地分析了不同雨滴击溅作用下土壤结构变化与入渗速率间的关系。结果表明:(1)击溅土壤结构发生变化,团聚体数量和三维分形维数显著增加,孔隙体积和大孔隙率显著减小。雨滴直径越大,击溅后的团聚体破碎程度越强,孔隙堵塞率最高达46.40%。(2)雨滴击溅下,破碎的团聚体堵塞孔隙,在土壤表层形成致密低渗的结皮层,结皮强度随雨滴直径和击溅次数的增加逐渐增加。(3)土壤入渗速率随雨滴直径和击溅次数的增加逐渐减小,经过3次雨滴击溅后减渗效应最高可达91.81%。(4)土壤稳渗速率与雨滴直径和土壤结构特征参数呈显著指数关系变化。研究表明,雨滴直径显著影响表层土壤结构和入渗特征,雨滴直径越大,土壤结构越分散,土壤入渗能力越低。 相似文献
7.
基于粒子成像瞬态测量技术的雨滴微物理特性及降雨动能研究 总被引：1，自引：1，他引：0
雨滴微物理特性及降雨动能是揭示降雨物理本质的重要特征量,亦是开展侵蚀定量分析与建立侵蚀量预报模型的基础。采用粒子成像瞬态测量可视化技术观测自然降雨雨滴,结合计算机视觉识别技术解算雨滴微物理特性参数,同时采用虹吸式自记雨量计记录自然降雨降雨强度。研究表明:该次降雨雨滴以中等粒子为主,雨滴直径均值为1.52 mm,降落末速度均值为3.47 m/s,其中直径在1.00~3.00 mm范围内的雨滴占样本总数的87.21%。雨滴直径和降落末速度呈显著的对数关系。基于实测的雨滴微物理特性和降雨强度估算降雨动能,该结果与传统的经验模型估算结果相对误差均值为7.28%。该方法得到的降雨动能较以往的经验模型能更真实的反应雨滴降落过程中的做功大小,为准确计算降雨过程中雨滴所造成的溅蚀量奠定基础。 相似文献
8.
雨滴击溅对耕作层土壤团聚体粒径分布的影响 总被引：7，自引：4，他引：3
为研究不同雨滴直径的降雨对耕作层团聚体的破碎及其粒径分布特征的影响,该文选取4个雨滴直径(2.67~3.79 mm)对耕层土壤(0~20 cm)团聚体进行雨滴击溅试验,每次试验各滴5 000滴,每1 000滴收集1次溅蚀团聚体。结果表明:1)所有收集次序中雨滴直径3.79 mm溅蚀量最大,累积雨滴数为2 000、3 000和4 000时,溅蚀量与雨滴直径均呈显著的指数函数关系。2)各雨滴直径的溅蚀量随粒径减小呈增大-减小-增大趋势,2 mm粒径的溅蚀量几乎为0,0.053 mm粒径的溅蚀量随雨滴直径增大而增大。3)相同雨滴直径不同累积雨滴数之间平均重量直径值差异不显著,相同累积雨滴数不同雨滴直径之间平均重量直径值差异不显著(P0.05)。4)不同雨滴直径溅蚀团聚体富集率随粒径变化一致,1 mm粒径溅蚀量团聚体富集率值接近0,0.053~1 mm粒径团聚体富集,1 mm粒径团聚体主要破碎成0.053~1 mm粒径团聚体,且粒级越小,富集率越高。研究可为黄土高原地区水土保持提供理论依据。 相似文献
9.
定量分析植被对降雨的再分配过程和植被影响雨滴溅蚀的方式,并比较了它们在被分配前后的击溅侵蚀能量。植被对降雨的再分配主要有3种形式:截流、透流和干流,其中,只有透流能溅蚀地面。再分配减少了溅蚀地面的雨量,但增加了雨滴直径。经过比较,结论如下:1)枯落物覆盖度与溅蚀能量呈线性负相关,枯落物覆盖度越大,溅蚀能量越小;2)在降雨量达到透流(经枝叶聚集部分)临界雨量以后,植被高度是所有植被特性中影响溅蚀能量贡献率最大的因子,植被越高,溅蚀能量越大;3)在降雨量达到透流(经枝叶聚集部分)临界雨量以后,雨滴终速度越大,植被所能减少的溅蚀能量越多。 相似文献
10.
滇中高原常绿阔叶林对天然降雨雨滴动能的影响 总被引：2，自引：0，他引：2
为探究滇中高原优势群落常绿阔叶林植被对降雨雨滴动能的影响,于2016年和2017年5—9月,在天然降雨条件下运用自计雨量计和滤纸色斑法,通过定位监测磨盘山常绿阔叶林林外降雨和林内穿透雨特征及其雨滴特性,针对不同降雨条件研究了常绿阔叶林对雨滴动能等特征的影响。结果表明:林外的雨滴个数比林内降雨的雨滴个数多61.7%;随着雨量的增大,雨滴直径分布规律也呈逐渐增大的趋势;在小雨条件下,0.5mm林外降雨雨滴直径数量占总雨滴数的40.85%,而同径级雨滴林内仅占总数的12.22%,且以0.5~3.5mm的雨滴数量所占比例较大;当林外降雨雨滴直径超过4.5mm,雨滴终点速度稳定在9.34m/s;林内降雨雨滴直径超过4.1mm,雨滴终点速度稳定在7.05m/s;同一雨滴径级下,暴雨条件下的雨滴动能比小雨时的动能大98.29%,且随降雨量的增大而增大,林内累积雨滴动能的峰值达到林外降雨的20.68%。随着雨滴直径的增大,穿透雨势能、降雨总势能及林冠截留势能均呈逐渐增大的趋势,缓冲势能比穿透雨势能大46.59%,占总势能的65.18%。林冠层对小雨具有截持和增大林内降雨雨滴直径的作用,且造成林内降雨的滞后性,林冠对天然降雨的降雨速度、势能及动能起到明显的缓冲作用。 相似文献
11.
Shmuel Yariv 《Geoderma》1976,15(5):393-399
The mechanisms for the detachment of soil particles by raindrops can be described by a model based on three stages. In the first stage, the soil is still dry and detachment of particles results from collisions of elastic bodies. In the second stage, the soil is fluidized and impacting raindrops cause the splash of drops of the fluidized soil. In the third stage, the fluidized soil is covered by an overland flow and drops of fluidized soil may disintegrate in the overland flow. High hydration energies of soil minerals of small particle size lead to high chemical interactions between raindrop water and soil particles and a consequent decrease of detachment of particles during the first stage. During the second and third stages, high hydration energies of minerals lead to high surface tension of fluidized soil and reduce the splashing of droplets of this fluid. The present model gives an explanation for the observed fact that the rate of particle detachment is greatest in coarse- and medium-sand-size material and is reduced at either larger or smaller particle sizes. It appears that high hydration energies are responsible for the low relative detachability of small particles. 相似文献
12.
Characterization of the drop-size distribution and velocity-diameter relation of the throughfall under the maize canopy 总被引：1，自引：0，他引：1
Renato Prata de Moraes Frasson Witold F. Krajewski 《Agricultural and Forest Meteorology》2011,151(9):1244-1251
In this study, we used a pair of optical disdrometers, one under and one outside the maize canopy, to measure the drop-size and the velocity distribution of hydrometeors during 12 storms and identified four distinct regions by examining how the fraction of drops recorded on the throughfall changed with respect to the drop diameter. The first region, containing drops with diameters smaller than 0.5 mm, showed an elevated number on the throughfall. Their numbers were comparable to the numbers of drops that lacked enough energy to adhere to the leaf. The second region, featuring drops with diameters larger than 0.5 mm and smaller than 3 mm, had a number ratio very close to the canopy gap fraction, indicating that their most likely origin was direct throughfall. The third region entailed drops with diameters ranging from 3 mm to 5.5 mm that featured a high throughfall to rainfall count ratio, with one of the diameter classes having higher counts under the canopy than outside of it. Through simplified calculations, we showed that drop weights in this region should exceed surface tension forces and lead to their detachment. In the fourth and final region, the throughfall to rainfall ratio decreased converging to the canopy gap fraction. By comparing the number of drops on each of the 440 diameter/velocity classes under and outside of the canopy, we were able to identify preferential drop sizes on the throughfall, i.e. classes of drop diameters with higher drop-size distributions under the canopy. The drop classes presenting higher counts under the canopy had diameters ranging from 3.25 mm to 5.75 mm with velocities between 1.4 m s−1 and 5 m s−1. We were able to trace the origin of those drops to heights of between 0.10 m and 1.05 m within the canopy, confirming that these drops constitute the indirect throughfall. The capability to estimate the detachment height of drops allows us to reconstruct the drop-size distribution at different levels of the canopy and offers unique insight into the mechanics of interception, indirect throughfall formation and re-interception of raindrops by the maize canopy. 相似文献
13.
晋西黄土区单株油松树下穿透雨空间分布特征研究 总被引：3，自引：1，他引：3
为了更好地解析黄土高原森林水文过程,为基于生态过程的森林水文模型的发展与参数化提供基础,在单株尺度上探讨了晋西黄土区典型油松林穿透雨的空间分布特征。在选取的2棵油松标准木的两侧树冠下,根据离树干的不同距离布置自记雨量计各7个,研究期间共观测了15场不同降雨和穿透降雨量。利用统计学方法分析了林外降雨和冠层结构特征与穿透雨之间的关系。结果表明：(1)部分观测点出现穿透雨率大于100%的状况,最大的穿透雨率达155.8%,这主要是因为降雨在冠层的作用下发生了聚集效应;(2)穿透雨量与降雨量呈显著正相关关系(p <0.05),穿透雨率与降雨强度也呈正相关关系,但其影响未达到显著水平;(3)距树干距离对穿透雨的影响是多重因素综合作用的结果,并且在穿透雨的空间分布中起到主导作用;(4)穿透雨率与郁闭度和冠层厚度呈负相关关系。 相似文献
14.
Splash droplet characteristics were studied using cine-photography and a simple droplet collection method. Two sizes of falling drop, two heights of fall and a number of target materials including soil, sand, water and rotating sandpaper were used. For a 6 mm drop falling at near terminal velocity about 5000 splash droplets were collected ranging in size from 10 um to more than 3 mm in diameter. The amount of soil material carried by splash droplets was much less in the presence of surface water and increased with the size of water stable aggregates. The energy and momentum balance showed a higher proportion of impact energy and momentum in the resulting splash droplets as the impact energy increased. This suggests that kinetic energy is not a reliable indicator of the erosivity of rain drops. 相似文献
15.
坡度对降雨溅蚀影响的研究 总被引：2，自引：0，他引：2
利用可以分别收集不同方向溅蚀土样的土槽装置,选取9个坡度(5°~45°),采用北京的普通褐土,借助人工模拟降雨手段研究了降雨溅蚀的发生过程及溅蚀量与坡度的关系。结果表明,随着坡度的不同,各方向的溅蚀过程呈现三种形式:(1)产流前溅蚀率较小,产流后迅速达到峰值,之后逐渐减小并逐渐达到稳定,峰值与稳定溅蚀率相差2倍以上;(2)产流前溅蚀率最大,产流后迅速减小并趋于稳定;(3)整个降雨过程中没有明显起伏。各个坡度下,次降雨溅蚀量均为上坡最小,下坡最大。上坡和侧坡溅蚀量与坡度成负相关,可分别用直线和指数函数拟合。下坡溅蚀量、溅蚀总分散量和溅蚀净搬运量均随着坡度的增大而先增大后减小,且为线性关系,临界坡度为35°。本研究将有助于深入理解降雨溅蚀侵蚀机理,并可为布设水土保持措施提供理论依据。 相似文献
16.
模拟降雨条件下塿土的溅蚀特征试验研究 总被引：1，自引：0，他引：1
溅蚀在破坏土壤表层结构的同时为后续侵蚀提供丰富材料,以黄土高原典型土壤塿土为试验用土,通过模拟降雨试验,根据溅蚀速率、溅蚀前后土壤颗粒组成及表面强度变化指标,系统研究塿土的溅蚀特征。结果表明,溅蚀速率随降雨历时呈现幂函数变化,分为迅速降低、缓慢降低、趋于稳定3个阶段。土盘表面松散颗粒及利于溅蚀的粒级范围内颗粒的消耗、团聚体破碎及超渗产生的水层消耗雨滴能量、结皮的形成和发育分别是3个阶段的主要影响因素。在90mm/h的雨强下,塿土颗粒富集与耗损的临界粒径是0.05mm,雨滴打击分离粒级0.05mm颗粒,富集迁移粒级0.05mm颗粒。当含水率相等时,降雨历时越长贯入深度越浅。塿土表面强度随降雨历时增加,0~30min是塿土结皮形成的关键时期。塿土溅蚀过程是表土颗粒组成不断变化和表面强度逐渐完善的过程。 相似文献
17.
土壤溅蚀过程和研究方法综述 总被引：2，自引：0，他引：2
土壤溅蚀是土壤侵蚀过程的开始,是指由于降雨雨滴打击土壤表层,引起土壤颗粒分散和迁移的一种侵蚀过程,是导致坡面水蚀的一个重要威胁因子。因此,土壤溅蚀是土壤侵蚀的重要形式和组成部分,具有重要的研究意义。土壤溅蚀过程和研究方法是土壤溅蚀领域研究的核心内容。论文根据有关资料,综述了国内外土壤溅蚀过程和研究方法方面的主要成果,并对将来的研究方向进行了展望,以期推动我国在该领域的研究工作。国内外研究表明,土壤溅蚀是土壤侵蚀的主要过程之一,是各种水文过程、水力过程和生态过程的综合表现,是复杂的降雨因子和土壤因子共同作用的结果,涉及一系列关于降雨雨滴与地表间的能量转换过程。测量土壤溅蚀的方法主要有溅蚀杯、溅蚀板和溅蚀盘。进一步的研究应致力于土壤溅蚀的力学过程和森林土壤溅蚀过程方面的探讨。 相似文献
18.
Y. Cao Z. Y. Ouyang H. Zheng Z. G. Huang X. K. Wang H. Miao 《Land Degradation \u0026amp; Development》2008,19(3):321-330
To evaluate the effects of different forest plantations on rainfall redistribution, we measured throughfall, stemflow, interception loss, surface runoff and soil loss from July 2004 to September 2005 in the three types of forest plantations Eucommia ulmoides, Vernicia fordii and Pinus massoniana. The results showed that differences in throughfall and stemflow between the three forest plantations were significant (p < 0·05). Throughfall was highest in the V.fordii plantation and stemflow was highest in the E.ulmoides plantation. Throughfall plus stemflow below the E.ulmoides canopy was greater than that underneath the other forest types. Moreover, significant spatial variation in throughfall was observed. Throughfall in P.massoniana was 28·0–39·7% higher at a stem distance < 60 cm or 11·5% lower at a stem distance > 120 cm than in the other forests, but the difference was not significant between E.ulmoides and V.fordii. Moreover, the difference in throughfall at stem distances 60–120 cm was not significant between the different forest plantations. For E.ulmoides, throughfall under the peripheral crown part was 16·1% higher than that close to the stem. In contrast to E.ulmoides, P.massoniana had 26·8% lower throughfall under the peripheral crown part than close to the stem. No significant difference was found in throughfall for the various stem distances underneath V.fordii. Stemflow in E.ulmoides was 2–3 times higher than in the other forests (p < 0·01). Interception loss accounted for 19·9% of gross rainfall for E.ulmoides, 20·8% for V.fordii and 27·2% for P.massoniana. Surface runoff and soil loss differed considerably among the three types of forest plantations. Annual runoff and total soil loss were lowest in the P.massoniana forest and highest in the V.fordii forest. This study indicated that P.massoniana, as a reforestation tree species, had the most positive effect on soil and water conservation among the three forest plantations. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
19.
森林对降雨的分配是森林生态水文和生物地球化学循环中的重要过程之一。通过对黄土丘陵区2种典型林分(刺槐林和辽东栎林)生长季降雨分配过程的实地监测,探究2种林分的降雨分配特征及其主要影响因素。结果表明:试验期间,刺槐林和辽东栎林降雨分配各组[JP]分均表现为穿透雨量(325.0,295.1 mm)＞冠层截留量(39.8,73.6 mm)＞树干径流量(25.8,21.9 mm),同时穿透雨率(83.2%和75.6%)＞冠层截留率(10.2%和18.8%)＞树干径流率(6.6%和5.6%)。次降雨量是影响降雨分配的关键因子,穿透雨量和树干径流量与次降雨量间呈现极显著线性关系,冠层截留量与次降雨量间呈现极显著对数函数关系;穿透雨率和树干径流率与次降雨量间呈现显著对数函数关系,冠层截留率与次降雨量间呈现极显著指数函数关系。刺槐林和辽东栎林产生穿透雨的次降雨阈值分别为1.0,1.3 mm,产生树干径流的次降雨阈值分别为5.9,5.4 mm。刺槐林产生的穿透雨量和[JP]树干径流量均大于辽东栎林,而冠层截留量小于辽东栎林。研究结果为黄土丘陵区森林生态水文过程的研究提供基础数据,对该地区植被恢复过程中植被类型的选择具有指导意义。 相似文献
20.
《国际水土保持研究(英文)》2014,2(3):67-73
A raindrop impact power observation system was employed to observe the real-time raindrop impact power during a rainfall event and to analyze the corresponding rainfall characteristics. The experiments were conducted at different simulated rainfall intensities. As rainfall intensity increased, the observed impact power increased linearly indicating the power observation system would be satisfactory for characterizing rainfall erosivity. Momentum is the product of mass and velocity (Momentum=MV), which is related to the observed impact power value. Since there is no significant difference between momentum and impact power, observed impact power can represent momentum for different rainfall intensities. The relationship between momentum and the observed impact power provides a convenient way to calculate rainfall kinetic energy. The value of rainfall kinetic energy based on the observed impact power was higher than the classic rainfall kinetic energy. The rainfall impact power based kinetic energy and the classic rainfall kinetic energy showed linear correlation, which indicates that the raindrop impact power observation system can characterize rainfall kinetic energy. The article establishes a preliminary way to calculate rainfall kinetic energy by using the real-time observed momentum, providing a foundation for replacing the traditional methods for estimating kinetic energy of rainstorms. 相似文献