黑沙蒿根系的易损部位及易损荷载类型

以鄂尔多斯及神木县采煤塌陷区的沙漠治理植物黑沙蒿为研究对象,采用TY8000伺服式强力机研究其根系的易损部位及易损荷载类型。结果表明:在1~5 mm径级范围内,黑沙蒿直根及侧根分支处的抗拉力、抗折力均与根径呈幂函数正相关,抗拉强度、抗折强度均与根径呈幂函数负相关。在各部分试验根中,平均根径分布规律均为:相邻上级直根侧根分支处相邻下级直根,其抗拉强度、抗折强度的差异均表现为:相邻下级直根侧根分支处相邻上级直根,在2种受力形式下,侧根分支处抵抗外力能力均优于相邻上级直根,弱于相邻下级直根。黑沙蒿直根及侧根分支处的抗拉力均大于抗折力,抗拉强度均大于抗折强度,说明,黑沙蒿直根及侧根分支处抵抗轴向拉力的能力均优于抵抗径向折力,其易损荷载类型为径向折力。     

加载速度对直根段、侧根分支处抗折强度的影响

以3~4年生柠条、沙柳、沙棘、白沙蒿为研究对象,选取直径1.5~2 mm和3~3.5 mm 2个径级根系,采用TY-8000伺服式强力机测定相同径级的直根段和侧根分支处对于加载速度的响应。研究结果表明:4种植物同径级直根段抗折强度均大于侧根分支处抗折强度,且抗折强度随加载速度增加而增大。最大加载速度与最小加载速度下抗折强度差异性显著。当加载速度为860 mm/min和10 mm/min,根径1.5~2 mm,柠条直根段、侧根分支处的抗折强度分别为63.79 Mpa、39.20 Mpa和50.76 Mpa、27.40Mpa;沙柳分别为25.54Mpa、26.05Mpa和19.22 Mpa、14.55 Mpa;沙棘分别为9.65 Mpa、6.76 Mpa和6.17 Mpa、4.28 Mpa;白沙蒿分别为6.40 Mpa、2.67 Mpa和4.96 Mpa、2.35 Mpa。同样,根径3~3.5 mm时,柠条直根段、侧根分支处的抗折强度分别为53.42 Mpa、33.00 Mpa和41.17 Mpa、19.38 Mpa;沙柳分别为20.03 Mpa、16.22 Mpa和16.60 Mpa、10.60 Mpa;沙棘分别为7.76 Mpa、3.47 Mpa和5.41 Mpa、2.27 Mpa;白沙蒿分别为5.33 Mpa、2.39 Mpa和3.26Mpa、1.58 Mpa。     

根长和加载速度对单根抗拉特性的影响

以准格尔煤田黑岱沟露天煤矿排土场生态恢复植被重建中3种4龄人工沙棘(Hippophae rhamnoides),柠条(Caragana microphylla)和紫花苜蓿(Medicago sativa)的根系为对象,进行室内拉伸试验,研究加载速度和根长对3种植物单根抗拉力学特性的影响。结果表明：紫花苜蓿的极限抗拉力和抗拉强度随着加载速度的增加而增加,沙棘单根则随着加载速度的增加,呈单峰型变化趋势,柠条随着加载速度的增加无明显变化规律。柠条和沙棘单根极限抗拉力和抗拉强度,随着根长的增加,呈递减的趋势,即单根长度越短,极限抗拉力和抗拉强度越大,紫花苜蓿单根极限抗拉力和抗拉强度随着根长的增加变化幅度不大,极限抗拉力变动幅度在33.3～38.85 N,极限抗拉强度变动幅度在27.19～31.73 MPa之间。     

黑沙蒿根系抗拉敏感性初探

以黑沙蒿根径1~5 mm根系为研究对象,使用TY8000式伺服控制材料试验机,探究直根和分叉根的轴向抗拉力与敏感性的关系。结果表明:黑沙蒿根系可缓冲和调节自身所受轴向拉力;不同径级下粗根敏感性均值强于细根,径级越大敏感性越稳定,相同径级下直根敏感性均值强于分叉根,直根敏感性更稳定;黑沙蒿根系敏感性最大值与径级呈幂函数负相关,直根:y=4.0804x^-1.061,R^2=0.9508,P<0.05;分叉根:y=5.5672x^-1.141,R^2=0.9393,差异性显著(P<0.05)。     

四川山矾根系分支节点对根系固土效益的影响

【目的】研究根系形态学参数和力学参数对固土效果的影响,进一步了解根-土相互作用机制和固土机制。【方法】利用改装过的万能试验机测定四川山矾根系的抗拉强度、杨氏模量、摩擦力等力学特性,利用自制的大盒直剪装置测定含根土样本的抗剪强度。分析根系形态学参数与力学特性参数的关系。【结果】1)四川山矾的根直径与根长、抗拉强度、杨氏模量和拔出力都符合幂函数关系。其中,根直径与抗拉强度和杨氏模量呈负相关,根直径与根长、拔出力呈正相关。2)四川山矾根系分支节点数的增加,可显著提高根系拔出力,但分支节点对单位根长度拔出力的影响较小。3)四川山矾根系分支节点的增加,可显著提高根系的土壤加固效果,每存在1个分支节点可提高根系附加抗剪强度约50%。分支节点的增加可显著提高单位根长和根直径的附加抗剪强度。4)主成分分析发现,对根系附加抗剪强度的极值影响最大的参数为根长之和,而对根系附加抗剪强度的屈服值影响最大的参数为根直径之和。【结论】四川山矾根系分支节点的存在对根系的拔出强度和最终的固土效果都有显著影响,是根系固土效果定量研究中的重要参数,这对理解和分析边坡植物根系加固土壤的机制有重要意义。     

浙南山区6种优势乔木植物根系的力学特性研究

为研究乔木植物固土护坡的力学机制,以中亚热带常绿阔叶林为例,对浙江南部的山体滑坡、泥石流易发区内优势植物:苦槠(Castanopsis sclerophylla)、甜槠(C.eyrei)、枫香(Liquidambar formosana)、南酸枣(Choerospondias axillaris)、马尾松(Pinus massoniana)和杉木(Cunninghamia lanceolata)6种乔木植物根系进行室内力学比较试验。结果表明:不同植物根系具有不同的抗拉力与抗拉强度;所有植物的单根抗拉力都随着直径增加而增大,其中杉木的抗拉力最低,甜槠、枫香和马尾松居中,苦槠和南酸枣的较高;6种植物直径与抗拉力间的拟合函数中以幂函数最为适合,并且6种植物直径与抗拉力间成幂函数正相关关系;6种植物根系的抗拉强度随着直径增加而降低,并且所有植物抗拉强度与其直径成幂函数负相关关系,其中杉木的抗拉强度明显低于其它树种;苦槠和南酸枣的固土护坡作用较大,枫香、甜槠、马尾松居中,而杉木的则最差。     

轴向反复荷载下灌木分叉处根段强度及变形特性研究

以神府-东胜煤田采煤塌陷区常见固土植物小叶锦鸡儿和北沙柳为研究对象,采用TY8000伺服控制试验机测定其1～4 mm根径范围内分叉处根段抗拉强度、延伸率等,研究此根段承受反复拉伸后的力学特性.结果表明:2种灌木分叉处根段的极限抗拉强度与根径呈负相关关系,极限抗拉力与根径呈正相关关系;小叶锦鸡儿的平均极限抗拉强度(25....     

台湾西南部优势竹类箣竹根力之研究

箣竹为台湾西南部泥岩地区早期主要造林树种,约占该地区绿蔽率之80%,形成极优势之植物。近年来因竹材价格低落,竹林之经营管理减少,其更新造林及其对坡面之保育功能之评价渐受重视。因此本研究为针对箣竹其根力特性,特进行根系与根域范围调查、根段拉力与植株引拔试验等,推估其坡面保育功效。研究结果为箣竹之根段拉力强度(Y)与其直径(X)成指数正相关,而箣竹之引拔抗力(F)与其胸高直径(D)成指数正相关。     

流动沙丘常年移植差戈巴蒿的初步探讨

差戈巴蒿(Artemisia haladendron Turcz ex Bess)属于菊科蒿属半灌木,它抗风蚀,耐沙压,耐瘠薄,耐干旱。萌蘖性强,丛状匐伏生长,复盖度大,根幅大,侧根发达,须根多。韧性大,生命力强。因此,它是优良的先锋固沙植物。在内蒙古自治区东部,凡有流动沙丘和半流动沙丘的地方都能生长。为了加速“三北”防护林的建设,固     

基于连续断裂过程的根系黏聚力Wu氏模型修正系数的确定

【目的】研究根系黏聚力Wu氏模型的修正系数,可提高Wu氏模型的精确度,进而提高造林边坡稳定性评价的准确性。【方法】针对Wu氏模型对根系黏聚力的高估问题,以刺槐和侧柏根系为研究对象,应用复合材料学的连续破坏理论,阐述根系的渐进失效过程,提出基于连续断裂过程的根系黏聚力Wu氏模型修正系数,即断裂修正系数,并研究不同算法间修正系数的差异性以及修正系数与根截面积比之间的关系。【结果】根系断裂修正系数随算法(P0.001)、树种(P0.001)和土层深度(P0.001)的变化而有显著差异;位移控制式算法引入的修正系数显著高于由拉力控制式算法引入的修正系数(P0.001);断裂修正系数随深度的增加而增加,表层30 cm内的修正系数显著低于深层根系(P0.001);根截面积比与断裂修正系数的负相关性存在阈值,当根截面积比小于阈值时(刺槐0.14,侧柏0.11),断裂修正系数随着根截面积比的增加而减少;当根截面积比大于阈值时,断裂修正系数的根截面积比效应不显著。【结论】根系断裂修正系数随算法和树种不同而变化,随土壤深度增加而增大,且在根截面积比阈值范围内(刺槐0.14,侧柏0.11)与根截面积比呈负相关关系。研究结论能为评价造林边坡的稳定性、揭示植物护坡的力学机理提供理论基础,并为水土保持工程植物措施的选择提供科学依据。     

沙棘绕实蝇的生物学习性

[目的]沙棘绕实蝇严重危害沙棘果实,使沙棘种植地蒙受巨大经济损失。研究其生物学习性,可以为有效监测和控制沙棘绕实蝇提供理论指导。[方法]通过室内人工饲养和野外观察,研究沙棘绕实蝇的羽化、交尾、产卵、化蛹等生物学习性和野外发生动态。[结果]沙棘绕实蝇成虫在野外从6月中旬至8月上旬均可见到,发生量受天气影响较大;成虫主要集中在6:00—10:00羽化,羽化量占当日羽化量的81.3%,羽化高峰出现在8:00—9:00;化蛹时间主要集中在凌晨0:00—6:00,尤其是3:00—6:00钻出果实化蛹的幼虫数量较多,与其它时间段有明显差异;交尾时间主要集中在白天光照比较强的时间段,一天当中有两次交尾高峰,分别出现在12:00—13:00和16:00—17:00,交尾平均持续时长为239±11.86 min;沙棘绕实蝇产卵期沙棘果长径6.65±0.28 mm,宽径5.47±0.40 mm,一果只产一卵。[结论]沙棘绕实蝇在内蒙古磴口地区一年发生一代,幼虫钻蛀果实,蛹隐藏在地下,成虫期较短,防治工作应集中在成虫期进行。     

Variations of root hydraulic conductance of Fraxinus mandshurica seedlings in different concentrations of NH4NO3 solution

Absorbing water from soil by roots in vascular plants is an important physiological function and plays an essential role on their water balance. The root hydraulic conductance (L _P) determined by radical water transport inside the root is a major influence on the shoot water status, plant growth, and development. However, a few studies have focused on the effect of different substances on L _P of roots, and the role of radical water transport was poorly understood. Based on the pressure-flux approach, this study used the roots of Fraxinus mandshurica seedlings with different treatments, i.e., distilled water, NH₄NO₃ solution, and HgCl₂ to determine the effect of various substances on L _P of roots. The objectives are: 1) to evaluate the difference in L _P occurred between distilled water and NH₄NO₃ solution with various concentrations; and 2) to examine the changes of L _P under distilled water and NH₄NO₃ solution with various concentrations after HgCl₂ treatment. The results showed that L _P of roots were 18.85×10⁻⁸ m/(s·MPa) in distilled water, 31.25–34.15×10⁻⁸ m/(s·MPa) in four NH₄NO₃ solutions (2, 4, 8 and 16 mmol/L), 14.69×10⁻⁸ m/(s·MPa) in distilled water after HgCl₂-treated, and 9.63–13.57×10⁻⁸ m/(s·MPa) in four NH₄NO₃ solutions after HgCl₂-treated, respectively. Aquaporins play an important role in regulating water uptake and transport in roots. NH₄ ⁺ and NO₃ ⁻ could stimulate activity of aquaporins, and L _P of roots in NH₄NO₃ solution was distinctly 77% higher than in distilled water. Nevertheless, Hg²⁺ can inhibit activity of aquaporins, and and L _P of roots decreased 22% in distilled water and 68% in NH₄NO₃ solution after treatment by HgCl₂ respectively. These evidences suggested that both Hg²⁺-sensitive aquaporins and ion channels existing in the protoplasm and vacuole membranes could regulate root water uptake, transport, and integral plant water balance. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(5): 706–712 [译自: 植物生态学报, 2005, 29(5): 706–712]     

Distribution and tensile strength of Hornbeam (Carpinus betulus) roots growing on slopes of Caspian Forests, Iran

Biomechanical characteristics of the root system of hornbeam (Carpinus betulus) were assessed by measuring Root Area Ratio (RAR) values and tensile strength of root specimens of eight hornbeam trees growing on hilly terrain of Northern Iran. RAR values of the roots were obtained using profile trenching method at soil depth of the top 0.1 m. In total 123 root specimens were analyzed for tensile strength. Results indicate that in general, RAR decreases with depth, following a power function. The RAR values in up and down slopes have no significant statistical differences. In most cases, the maximum RAR values were located in soil depth of the top 0.1 m, with maximum rooting depth at about 0.75 m. The minimum and maximum RAR values along the profiles were 0.004% and 6.431% for down slope and 0.004% and 3.995% for up slope, respectively. The number of roots in the up and down slope trenches was not significantly different. In the same manner as for RAR, number of roots distributing with depth was satisfactorily approximated a power function. The penetration depths of above 90 percent of the roots were at soil depths of 50 cm and 60 cm for up and down slopes, respectively. Results of Spearman’s bivariate correlation showed no significant correlation between the RAR value with tree diameter and gradient of slope and number of roots. The mean value of root tensile strength was 31.51 ± 1.05 MPa and root tensile strength decreased with the increase in root diameter, following a power law equation. Using ANCOVA, we found intraspecies variation of tensile strength. Biography: Ehsan Abdi (1978– ), Male, Ph.D candidate, in the Department of Forestry, University of Tehran, Karaj 31585-3314, Iran.     

植被恢复对高寒沙区土壤性质的影响

[目的]明确高寒沙区不同植被类型对土壤性质改良效果的差异,探讨各植被区沙地土壤恢复过程的异质性和人工林木的可开发利用潜力。[方法]以沙珠玉治沙试验林场内不同生长年限的人工植被为研究对象,分析高寒沙区6种植被类型区(乌柳、青杨、赖草、柠条、沙棘、柽柳)以及3个对照区(农田、流动沙丘、丘间沙地)土壤的机械组成、p H值、有机质及全N、全P、全K等理化性质指标。[结果](1)植被恢复生长51年后,从黏粒和粉砂粒增加的比例角度分析,土壤质地改良顺序为沙棘(206.3%)柠条(108.5%)青杨(70.5%)乌柳(56.8%)赖草(54.1%)柽柳(42.3%);从全N、全P和全K增加的比例角度分析,土壤养分改良顺序为青杨(198.2%)柠条(166.7%)沙棘(155.3%)乌柳(82.6%)赖草(75.4%)柽柳(53.9%),土壤全P含量偏低,平均0.42 g·kg-1;(2)植被恢复生长51年后,柠条、沙棘、青杨、赖草、乌柳和柽柳林下0 30 cm土壤有机质含量依次为20.19、18.25、30.81、23.57、22.13和10.62 g·kg-1,比流动沙丘或丘间沙地相应的提高了766.7%、702.4%、689.8%、517.4%、491.5%和343.9%。[结论]随着植被恢复年限的增加,土壤质地和养分状况得到显著改善,但土壤p H值的变异系数较小;各样地土层间有机质含量差距不断扩大,表聚性越来越明显,并且随深度增加各土层恢复效果存在滞后性。柠条和沙棘适宜在共和盆地推广种植,建议实施适当地抚育管理措施,以促进高寒沙区林场实现可持续经营发展。     

Organic matter contribution to soil fertility improvement and maintenance in red Alder （Alnus rubra） silvopastoral systems

An investigation was conducted to quantify fine roots and roots nodules over the four seasons in forestry and agroforestry alder (Alnus rubra) stands in North Wales. Soil samples collected in each season were excavated at three sampling points (0.30 m, 0.57 m and 1.00 m distance from the base of each tree) from nine trees of the agroforestry and forestry plots. Result showed that the density of live fine root had significant differences in between seasons and treatments (P ＜ 0.001). The mean weight density of live fine root over the four seasons in agroforestry and forestry was 0.27±0.01 kg·m-3 and 0.54±0.03 kg·m-3, respectively. Weight density of dead root in each system remained constant throughout the year. The mean weight density of dead root was also significantly different (P ＜ 0.01) between forestry and agroforestry systems. Weight density of live and dead root nodule was both constant throughout the year and between the different sampling distances. The mean weight densities of live and dead root nodule over the four seasons were 0.09±0.03 kg·m-3 and 0.05±0.03 kg·m-3 in agroforestry and 0.08±0.02 kg·m-3 and 0.03±0.01 kg·m-3 in the forestry plots, respectively.     

Root Ecological Niche Index and Root Distribution Characteristics of Artificial Phytocommunities in Rehabilitated Fields

In the implementation phase of the Conversion of Cropland to Forest and Grassland (CCFG) project in China, it is important, from a scientific point of view, to recognize phytocommunities’ characteristics, species compatibility, and ecological function. The ecological niche that roots occupy, their abundance and distribution, and the factors that affect them must be acknowledged. Following the methodology of community ecology, the total root mass of a phytocommunity is measured as cubic volume. Root biomass, length, and the number of roots in every diameter class, for each soil layer and for each plant species, are regarded as observation variables. In the first instance therefore, a new method to calculate the root ecological niche index (RENI) is proposed, embracing the entire phytocommunity of plantations. Using the new method, the roots of phytocommunities in Datong County, Qinghai Province (one of the counties selected for the national CCFG experiment), are dealt with in this paper. The results show that most of the vertical distributions of plant roots belong to the type wherein the roots are concentrated in the topsoil layer (0–20 cm), far more than those in the lower soil layers. The RENI of phytocommunities is higher than that of pure stands or monocultures. The distribution of RENI by root diameter can be divided into four types: J-type, inverse J-type, recumbent S-type, and U-type. RENI is positively correlated with the wet biomass of aboveground level stems, branches, and plant leaves, and with the species richness of phytocommunities. Although the RENIs of plantations in rehabilitated fields are a little lower than those of natural forests, they are higher than those of cultivated crops. The RENIs of three community types (Picea crassifolia + Hippophae rhamnoides ssp. sinensis, H. rhamnoides ssp. sinensis, and P. crassifolia) in rehabilitated fields benefit greatly from the restoration project. The implementation of the CCFG project is important for the increase in RENI and the multiple functions of plant roots. Translated from Acta Ecologica Sinica, 2005, 25(3) (in Chinese)     

短期NaCl胁迫对西伯利亚白刺幼苗Na~+、K~+分配和平衡的影响

[目的]为探究西伯利亚白刺盐适应机制。[方法]以1年生西伯利亚白刺水培幼苗为材料,研究不同浓度NaCl(0、200、300 mmol·L-1)胁迫24 h后根系Na~+、K~+离子流的动态变化(利用扫描离子选择微电极技术,SIET)及植株各器官中Na~+、K~+含量的静态变化(利用电感耦合等离子体光谱仪,ICP-OES)。[结果]表明:(1)短期NaCl胁迫显著提高了西伯利亚白刺根、茎、叶中Na~+含量,其中,叶中Na~+含量是根中的3倍以上;西伯利亚白刺根、茎、叶中K~+含量保持稳定或上升;(2)盐胁迫下,西伯利亚白刺根、茎、叶中K~+/Na~+呈下降趋势,其中,在200、300 mmol·L-1NaCl胁迫下,根中K~+/Na~+差异不显著;(3)离子流结果显示,NaCl胁迫显著提高了西伯利亚白刺根系Na~+的外流;对照和200 mmol·L-1NaCl胁迫下,K~+净流量分别为156、159 pmol·cm-2·s-1,差异不显著;300 mmol·L-1NaCl胁迫显著提高了K~+的内流,净流量为-370 pmol·cm-2·s-1。[结论]综合分析认为,西伯利亚白刺通过叶片对Na~+区隔,加强根系对Na~+的外排和K~+内流,进而维持植株根系K~+/Na~+的相对平衡,以此适应盐渍环境。     

Cu、Zn制剂对油橄榄容器苗生长和根系的影响

[目的]针对油橄榄容器苗存在主根较为粗大、须根极少、根系盘绕等现象开展化学制剂控根试验,找出适宜油橄榄容器苗的化学控根试剂,从而解决根系畸形导致的油橄榄苗木质量差等问题。[方法]采用4种不同浓度的CuSO_4制剂及ZnSO_4制剂对油橄榄2年生容器苗进行控根试验,测定苗高、地径及地上部、下部生物量,通过根系扫描仪分析根系生长特点,探讨各项生长指标以及生理指标对控根效果的影响。[结果]显示:(1)20 g·L~(-1)和60 g·L~(-1)的Cu制剂可提高容器苗的地上部分生长量;60 g·L~(-1)和200 g·L~(-1)的Cu制剂可显著增加生物量的积累。(2)200 g·L~(-1)的Cu制剂对苗木新根着生效果最为显著;120 g·L~(-1)的Cu制剂对根系的直径、表面积和体积有良好的促进作用;而不同ZnSO_4控根制剂处理对苗木侧根的各指标产生抑制作用。(3)枝条生长量与侧根长度呈显著正相关性;地径、枝条生长量与侧根表面积呈极显著正相关关系。(4)120 g·L~(-1)的Cu制剂处理后叶片的可溶性蛋白质含量最高,Cu制剂浓度为20 g·L~(-1)时,叶片的叶绿素含量增加。[结论]试验发现质量浓度为120 g·L~(-1)和200g·L~(-1)CuSO_4制剂控根效果良好,可运用于实际生产。     

两种接种方式下角倍蚜虫瘿对寄主盐肤木枝叶生长的影响

[目的]明确两种接种方式(自然迁飞和人工挂袋)下角倍蚜虫瘿的数量和分布及其对寄主盐肤木枝叶生长的影响。[方法]在自然迁飞和人工挂袋形成虫瘿的盐肤木林内,按随机区组设计设置样地,在样地内随机选取有虫瘿树和无虫瘿树,分别测量和统计盐肤木及虫瘿的生长指标,采用方差分析虫瘿对盐肤木生长的影响。[结果]在自然迁飞和人工挂袋两种接种方式下,盐肤木单株虫瘿数没有显著差异。但人工挂袋时,单片复叶的平均虫瘿总体积为170.92±14.85 cm~3、小叶总面积为616.26±32.73 cm~2,显著高于自然迁飞形成虫瘿的总体积85.82±9.40cm~3和小叶总面积482.81±28.51 cm~2。表明人工挂袋接种可以增加虫瘿的总体积,从而提高角倍产量;同时,较大体积的虫瘿还促进了盐肤木小叶的生长,使小叶面积增大。[结论]角倍蚜虫瘿对寄主盐肤木的枝叶生长具有促进作用,且这种生长促进与虫瘿的体积呈正相关。与自然迁飞接种相比,人工挂袋接种更能发挥盐肤木的生长和结倍潜力,提高角倍产量。     

Field investigation on Salix psammophila plant morphology and airflow structure

The field investigation was undertaken to determin the characteristics of Salix psammophila plant morphdogy and airflow structure of single-line S. psammophila on the southern edge of the Mu Su sandland. The results showed that artificially cultivated single-line S. psammophila could accumulate sand because the plant decreased the windward and leeward wind velocity. There was a significant correlation (R = 0.696) between accumulated sand volume (V ₂) and plant volume (V ₁). The wind velocity was 6 m/s at a 4 m height of single-line S. psammophilahedge row. The wind velocity decreased at 3 H windward and increased at 2 H to windward. The wind velocity then steeply decreased to leeward and reached its lowest value at 1 H to leeward and gradually recovered to the open field velocity. The protection distance of the single-line S. psammophila was about 17 H′ and the effective protection distance was about 13 H′. Single-line S. psammophila had few effects on the wind velocity when the wind was above the plant height. __________ Translated from Chinese of Applied Ecology, 2005, 16(11) [译自: 应用生态学报, 2005, 16(11)]