共查询到20条相似文献，搜索用时 218 毫秒
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马尾松毛虫是我国南方主要森林病虫害之一。以往防治大多在扩散危害的四月至十月进行,在这期间,松毛虫经历了三代,虫量迅速增加,形成治不胜治的被动局面。十一月至翌年三月为松毛虫的越冬期,虫体处于几乎不危害的越冬状态。据我们观察,松 相似文献
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笔者设计了幼虫期发育指数法,对江山县和睦标准地(省测报点)的松毛虫越冬代、第一、二代测报资料进行了统计分析。统计分3个步骤,①将幼虫发育进度百分率换算为幼虫发育指数。换算公式为: 相似文献
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马尾松毛虫在我国每年发生近2,000万亩,严重影响了马尾松和几种国外引种松的生长,是我国最重要的森林害虫之一。了解和掌握松毛虫蛹期及成虫期的生物学特性,对于开展性信息素工作的研究及遗传防治等,有一定的帮助。1977年第三代,1978年越冬代和第一代,我们对松毛虫蛹期及成虫期的生物学特性进行了连续的观察,现将结果整理如下: 一、蛹 期 相似文献
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根据上杭县4个乡镇1992~2006年连续15 a间马尾松毛虫发生期观察调查的历史资料进行统计和分析,计算松毛虫发生期各阶段平均期距和估计区间,作为今后同期预测松毛虫发生期的期距值;将松毛虫发生期与历史同期气温建立回归方程,建立了龙岩市松毛虫回归预测数学模型,经检验证明结果准确,为生产提供参考和借鉴。 相似文献
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Algirdas Augustaitis Ingrida Augustaitienė Almantas Kliučius Gintaras Pivoras Dalia Šopauskienė Raselė Girgždienė 《European Journal of Forest Research》2010,129(3):431-441
The multiple-stressor effects of air pollution, nutrient and water availability are the key issues of present forest ecosystem
research. However, too little is known about the seasonal effect of pollutants on tree crown defoliation and their interaction
with changes in climate. Therefore, data on seasonal variation in air pollution, including surface ozone, deposition of acidifying
compounds and meteorological conditions, were tested against pine defoliation to identify the periods when the effect of the
considered contaminants is most pronounced. The findings of the study revealed that a higher level of air concentrations of
acidifying pollutants and their deposition was observed during the dormant period, with the exception of only ΣNH4+ air concentrations and their monthly deposition. An increase in precipitation over the vegetation period and mean monthly
temperature from September to December, as well as a decrease in temperature and precipitation over the remaining months of
the dormant period represented the climate change condition over the 14-year period in the observed region. Detected changes
in the considered parameters during the dormant period were found to be most significant to changes in pine crown defoliation.
Therefore, we concluded that climate changes, if they occur by the detected scenarios, should mitigate the negative effect
of air pollutants and acid deposition on pine crown condition. 相似文献
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我国南方五省区湿地松木材的密度、晚材率和各项力学强度,随纬度的增加,呈递减状态。纬度与气干容重之间的直线回归方程为:G=1.28—0.027L,相关系数r=0.984.产生此现象的主要原因是,木材的管胞宽度和厚度随着纬度的增加逐渐变窄、变薄。产地的年平均气温和年降水量对湿地松树木的年轮宽度和晚材带宽度影响较大;年轮和晚材带的平均宽度随产地自北向南依次增加,随着山地海拔的升高而减小。 相似文献
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Net photosynthesis was measured under field conditions in 23-year-old slash pine (Pinus elliottii Engelm. var. elliottii) trees to determine how it was affected by fertilization and climate. There was only a small decrease in rates of net photosynthesis from late summer through winter demonstrating that appreciable carbon gain occurs throughout the year in slash pine. Although fertilization substantially increased leaf area and aboveground biomass, it only slightly increased the rate of net photosynthesis. Simultaneous measurements of gas exchange in fertilized and unfertilized (control) plots allowed the detection of a small, but statistically significant difference in average net photosynthesis of 0.14 micro mol m(-2) s(-1). Irradiance, and to a lesser extent air temperature, were the environmental factors that exerted the most control on net photosynthesis. The highest rates of net photosynthesis occurred between air temperatures of 25 and 35 degrees C. Because air temperatures were within this range for 46% of all daylight hours during the year, air temperature was not often a significant limitation. Soil and atmospheric water deficits had less effect on photosynthesis than irradiance or air temperature. Although the depth to the water table changed during the year from 10 to 160 cm, predawn and midday xylem pressure potentials only changed slightly throughout the year. Predawn values ranged from -0.63 to -0.88 MPa in the control plot and from -0.51 to -0.87 MPa in the fertilized plot and were not correlated with water table depth. There was no correlation between xylem pressure potentials and net photosynthesis, presumably because water uptake was adequate. Although vapor pressure deficits reached 3.5 kPa during the summer, they had little effect on net photosynthesis. Over a vapor pressure deficit range from 1.0 to 3.0 kPa, net photosynthesis only decreased 21%. No differences in responses to these environmental factors could be attributed to fertilization. 相似文献
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马尾松木材在高温干燥中的水分扩散性 总被引：9，自引：0，他引：9
对马尾松木材在高温干燥过程中的水分非稳态扩散进行了研究 ,结果表明当含水率高于纤维饱和点时 ,水分扩散系数随含水率的降低而增加 ;当含水率低于纤维饱和点时 ,水分扩散系数随含水率的下降而减少。马尾松木材的径向扩散系数大于弦向扩散系数。随着温度的升高和相对湿度的降低 ,木材的横向水分扩散系数增大 相似文献
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木材可压缩流体渗透中滑流的研究 总被引：1，自引：0，他引：1
在气体平均压力倒数为1.4-48atm~(-1)范围内测定了长白鱼鳞云杉和红松木材可压缩流休渗透中滑流效应及影响滑流的因素,论述了木材中流体流动形态和机理。研究表明,两种木材可压缩流体渗透中均产生滑流,但长白鱼鳞云杉中滑流高于红松。前者滑流渗透性与真渗透性百分比、比名义渗透性与真渗透性比、滑流因素分别为69.39％、1.69、0.356atm;后者分别为37.64％、1.376、0.197atm。滑流的大小与木材有效毛细管半径、真渗透性和气体平均压力有高度紧密相关。木材有效毛细管半径愈小,真渗透性愈低,或气体平均压力愈低,则滑流效应愈大。 相似文献
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油松人工林不同大小林隙环境因子差异性比较 总被引：1，自引：0，他引：1
【目的】油松Pinus tabulaeformis是我国北方地区主要造林树种。旨在阐明油松人工林抚育间伐24 a后形成的不同等级林隙间环境因子的差异,探讨林隙的形成对环境因子的影响以及环境因子间的相关关系。【方法】在油松人工纯林选择4种等级的林隙,即林隙直径和冠层平均树高(即林分平均高)之比分别为L-Ⅰ(0.75 H)、L-Ⅱ(1.00 H)和L-Ⅲ(1.25 H)(H为冠层均高)和对照(CK,林冠下),测量了生长旺季的环境因子(光合有效辐射、空气温度、空气湿度、土壤温度和土壤湿度),在此基础上,分析了不同林隙等级间和林隙内不同区域的环境因子的差异性以及环境因子间的相关关系。【结果】1)不同等级林隙间光合有效辐射和土壤温度均达到了显著差异(P <0.05),最大差值分别达到了167.94μmol/m^2s和0.7℃,且随着林隙面积的增大而增大。2)3个面积等级的不同区域间光合有效辐射均表现出了显著的差异,土壤温度仅在L-Ⅱ面积等级林隙中达到了显著差异(P <0.05),在林隙中心区域光合有效辐射和土壤温度具有最大值。3)除了L-Ⅲ面积林隙等级外,其余的林隙等级和对照内光合有效辐射与土壤温度之间均有显著的正相关性(P <0.05)。【结论】在油松人工林内,抚育间伐24 a后,间伐产生的不同等级林隙和林隙区域会对光合有效辐射与土壤温度产生显著影响,对其他环境因子的影响不大。 相似文献
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油松对松毛虫危害的反应 总被引：9，自引：0，他引：9
为弄清油松对松毛虫危害有无自控能力，利用植物的生态控制力防治松毛虫，减少浓药的用量，采用蒽酮分光光度法测定不同失叶强度下油松干基糖分含量，结果表明：在人工模拟摘叶和松毛虫自然危害条件下，油松具有补偿和超补偿能力；在２—３年生针叶失叶较多的情况下，油松可将干部贮藏的营养物质供一年生针叶的正常生长。即使在连续三年２—３年生针叶失叶较多的情况下，油松也不致死亡，仍能正常生长。 相似文献
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Stanislav Vacek Pavla Hejcmanová Michal Hejcman Zdeněk Vacek 《European Journal of Forest Research》2013,132(5-6):801-813
Plant communities with Dwarf pine (Pinus mugo var. pumilio) form characteristic vegetation in the subalpine belt of the Giant Mountains (Krkono?e, Karkonosze and Riesengebirge, Czech Republic). This “island” of arcto-alpine tundra represents the northernmost edge of Dwarf pine natural range. We asked how concentration of sulphur in needles, growth, healthy status and fructification changed over three decades (1981–2011) with different air pollution in differently aged (45–120 years) autochtonous and allochtonous (introduced from the Alps) Dwarf pine stands. Different Dwarf pine stands above the alpine timberline were able to withstand 1980s, the period of heavy air pollution, without any decrease in growth rate or remarkable decrease in healthy status. Dwarf pine is thus highly tolerant to deposition of sulphur compounds. High concentration of SO2 in the air positively affected sulphur concentration in needles and eliminated thus sulphur deficiency. Higher germination rate of seeds in 2000s in comparison with 1980s indicate that the air pollution could decrease germination ability of seeds. High insect outbreaks (by Thecodiplosis brachyntera and Neodiprion sertifer) in 1990s and 2000s caused decrease in needle year classes. As there was a gradual increase in mean annual temperature over years 1981–2011, Dwarf pine stands can be more and more endangered by insect outbreaks in the future. There was no remarkable difference between autochtonous and allochtonous stands in all measured growth, healthy status and fructification characteristics. To determine real effects of air pollution and insect outbreaks on Dwarf pine stands from year to year fluctuations, decade-long monitoring is necessary. 相似文献
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Growth and gas exchange characteristics were studied in pine (Pinus sylvestris L.) and spruce (Picea abies Karst.) seedlings grown in hydroponic culture in the presence of N (50 mg l(-1)) and transferred at the start of their second growing season to tap water at 5, 8, 12, 16 or 20 degrees C (air temperature between 18-20 degrees C) for 3 weeks (pine) or 5 weeks (spruce). Root growth of both species was completely inhibited at root temperatures of 5 and 8 degrees C, but increased almost exponentially as root temperature increased. Shoot growth was maximal at 12 degrees C in both pine and spruce and decreased at low root temperatures. In both species, CO(2) uptake was decreased at low root temperatures and appeared to be influenced by the pattern of nitrogen retranslocation. In pine seedlings, as root temperature increased, an increasing proportion of the total nitrogen pool was retranslocated to the new shoot, whereas in spruce seedlings nitrogen was retranslocated to the roots. Differences in the retranslocation of nitrogen in the two species were reflected in the amount of soluble protein in needles, which at the end of the experiment increased with increasing root temperature in pine, but decreased in spruce. Our data suggest that in spruce, but not pine, CO(2) uptake was limited by the amount of Rubisco. 相似文献