直接为害温室黄瓜的自然灾害

一、风害 大风袭击对温室造成的为害主要有：①倒塌。原因是最后一排立柱向北倾斜度不够，固定性差。②风鼓毁膜。棚膜上如有严重破洞或修补得不结实，风一吹马上出现大的破口。     

速生桉树抗逆性调查分析

对霞浦杨梅岭国有林场柳窿桉、赤桉8号和2号3种桉树引种状况进行调查,表明3种桉树均具有较强的抗风害能力;在霞浦沿海海拔300~400m的山地引种赤桉8号和2号,冻害对其生长不致于造成危害。而柳窿桉应在200m以下山地发展。     

去冬今春金华市柑桔寒风害调查分析及应对措施

柑桔寒风害是一种与冻害既有区别又有联系的气象灾害，寒风对柑桔的为害主要是较大的风速和低温：而冻害是由于0℃以下的低温引起柑桔细胞组织受冻，其主要原因是植物细胞冰晶形成使生物膜破坏和蛋白质变性而产生的伤害作用。     

台风对沿海地区梨树生长的影响及对策

台风是发生在太平洋西部海洋和南海海上的热带气旋，是一种强烈的风暴，登陆时带来的强风暴雨往往对沿海的农业造成极大破坏，近两年来，台风在浙江、福建一带活动频繁，并呈现出强度大，持续时间长、影响范围广等特征，如2004年“云娜”、“艾利”、2005年“麦莎”、“海棠”，均对浙、闽、沪等沿海地区梨树生产带来巨大损失，台风已成为我国沿海地区发展梨业最大的制约因素。     

蔬菜大棚生产中风害的气候分析及预防措施

20世纪 90年代中后期 ,随着种植结构的新一轮调整 ,大棚设施不仅被广泛应用于蔬菜作物冬春季栽培、促成栽培和反季节栽培 ,而且在秋季蔬菜延后栽培、种苗繁育以及避雨或遮阴栽培中也普通使用。但是 ,在大棚生产期间风灾频繁 ,常毁坏大棚设施 ,棚中作物受大风影响不仅产生机械损     

Effects of thinning on wind damage in Pinus thunbergii plantation ——Based on theoretlcal derlvation of risk—ratios for assessing wind damage

Based on paper of “Theoretical derivation of risk-ratios for assessing wind damage in coastal forest“,wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investigated for four successive growing seasons.Besides wind damage,the wind profiles outside and inside the coastal forest stand and the distributions of optical stratification porosity (OSP) were also observed.Based on these data,risk-ratios of wind damage for both individual trees and stands were estimated according to the methods developed in “Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest“.The results showed that risk-ratios of wind damage,which were calculated from the meen height and diameter only and from the combination of wind and stand sructure profiles,accurately predicted wind damage in the plantation.Relationships between different thinning ratios and incidence of wind damage showed that stand stability decreased soon after the thinning.This was due to the immediate effects of thinning on increasing the canopy roughness and wind load,and on decreasing the sheltering effects from surrounding trees.However,thinning strategies could improve the stability by long-term effects on growthand development of trees against extreme wind.Only canopy damage was recorded during the experimental period,no stem damage was found,even though the maximum 10-min wind speed outside the coastal forest attained 30.2m s^-1.The results obtained in this study indicate that thinning is the most effective silvicultural strategy available for managing coastal forest despite the increased probability of wind damage soon after thinning.     

冬枣树自然灾害及其防御

<正> 冬枣树是结果早,产量高,效益好的经济树种,被当地农民称为“摇钱树”,但是仍受自然灾害的制约。1 旱害1.1 干旱对冬枣树生理的影响 当土壤中过于缺乏水分时,冬枣树叶即出现卷曲或调萎,缺水时间一旦持久,即可造成严重的旱害,尤其有些地方土壤持水量低,浇水条件差     

粤东滨海城市绿化树种抗风性评价与筛选

在地处广东省沿海的汕头市市区设置固定风口调查小区,分别在2003年第13号台风"杜鹃"、2005年第10号强热带风暴"珊瑚"、2006年第1号强台风"珍珠"过后进行绿化树种风害调查;以灾后风害木恢复原景观的修复投入比例综合专家咨询确定权重,采用改良加权评分法分析城市绿化树种的抗风性,结果表明:汕头市区66个常见绿化树种,可以划分为4个抗风级别,其中Ⅰ级树种36个,抗风性较强;Ⅱ级树种19个,抗风性一般;Ⅲ级树种7个,抗风性较差;Ⅳ级树种4个,不抗风.     

梨树防风害

我国北方风大.因大风引起的梨树生长、开花、结果异常,称为梨树风害.沿海地区受台风侵袭.梨树也可能引起风害.我区是梨树发展面积较大的地区,有必要加强对梨树风害的认识与防御.大风对梨树的危害可分为直接危害和间接危害两类.直接危害可造成机械损伤,轻者导致不同程度的落果,影响当年产量,重者树叶被吹落或破损,树枝折断,甚至整株折断死亡.间接危害是大风吹动枝叶,相互摩擦、冲撞,致使枝叶受伤,病菌易侵入,导致梨树发生病虫害.有人曾作过统计,在梨树开花坐果期和果实成熟期,若遇7级以     

试论园林绿化树种保护管理要点

文章主要阐述了林业工人对树木做防护管理的6个要点。