共查询到20条相似文献,搜索用时 62 毫秒
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落叶松自20世纪70年代末引入六盘山地区开始荒山造林,造林后充分显示了其适应性。目前,落叶松在人工林中占的比重极大。但是,近年来由于气候异常,大部分又以纯林为主,所以造成叶蜂严重危害,影响了落叶松的生长。 相似文献
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我区落叶松红腹叶蜂猖獗的原因 总被引:1,自引:0,他引:1
近年来,由于多方面环境因子的干扰,使得原来是次要害虫的落叶松红腹叶蜂,逐渐成为我区落叶松人工林的主要害虫,其种群密度之大,足以使成片的落叶松人工林在短期内失去全部叶片,并且危害的面积也在逐年扩大。造成这种次要害虫上升为主要害虫的原因是多方面的,但主要... 相似文献
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在林业养护管理阶段,防治病虫害是重要的工作内容之一.明确常见病害的生物学特性方能拟编出针对性更强、实用价值更高的防治方案.落叶松叶蜂为落叶松生长阶段的常见虫害,在东北、西北等诸多地区均有分布,大规模成灾时将会啃食大片落叶松林针,严重时造成落叶松枯死.在解读红腹叶蜂生物学特性的基础上,探究几点较为有效的防治技术办法,以供... 相似文献
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一、调查分析宁陕县国有上坝河林场于七十年代中后期引进了华北落叶松,现有落叶松纯林、混交林四、五百亩。1990年6月下旬至7月上旬和2001年6月下旬至7月上中旬在堆窝坪对面、华家湾口右侧三队对面、 相似文献
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林带对太湖地区农业非点源的控制效应研究 总被引:1,自引:0,他引:1
太湖地区是高度发达的农业生产区之一,大量使用化肥和杀虫剂加重该地区的环境污染水质污染。本研究选择以油菜-水稻和小麦-水稻为轮作方式的两片农田为农田生态系统,5年生的杨树林带和8年生的水杉林带为研究对象,通过采集水体、作物、林地下的氮和磷的样本,对农田生态系统中 N、P等(主要水污染物)迁移和淋失进行了研究,并对林带作对农业非点源污染的控制效应进行了分析。结果表明:农田生态系统中 N、P等迁移、淋失状况随轮作方式、作物种类及施肥状况而变化;农田与沟渠间的缓冲林带具有截留和净化土壤径流中的N、P等物质的作用,从而在一定程度上控制农业非点源污染。研究表明:当农田与林带宽度比例为100∶40时,在油菜-水稻轮作方式下,50.05%流失N和29.3% 的流失P可以被林带所吸收, 在小麦-水稻的轮作方式下,30.98 %流失N和86.73% P可以被林带所吸收;当农田与林带宽度比例为150∶40,在油菜-水稻轮作方式下, 33.7%流失N和19.58%P可以被林带吸收,在小麦-水稻的轮作方式下,20.65%流失N和57.82% 流失P可以被林带所吸收。因而,农田与林带宽度比例100∶40或150∶40较为合理,这种模型既能少占耕地,又能净化水质、保护生态环境。杨树生长快、用途广,适于太湖地区营造水环境保护林带。图2表4参8。 相似文献
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The varying (local) parameter(s) in site index models can be treated as fixed or random. Two primary subject-specific approaches to height modeling, the dummy variable method (fixed individual effects) and the mixed model method (random individual effects), were compared using Chapman–Richards type models fitted to second-rotation loblolly pine (Pinus taeda L.) data from a designed experiment. For height prediction of new growth series, tested on our validation subset data, the mixed model provides a new (local) parameter prediction method (termed as mixed predictor), which generally performed better than the traditional method of recovering local parameters (the least squares (LS) predictor we used). However, using the LS predictor, both the dummy variable estimation method and mixed model estimation showed almost identical prediction results. With multiple pairs of height–age measurements, no big difference was found in empirical site index prediction between the LS and mixed predictor. Theoretically, one main advantage of the mixed model approach is the ability of its mixed predictor to predict several local parameters using a single height–age pair. However, our empirical results failed to support this point. 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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对杨干象的几种不同防治方法的防治效果进行对比试验调查,找出杨干象的操作简便、效果最佳的防治方法,更好地指导杨干象的防治工作。结果表明:采用2.5%溴氰菊酯350mL加10奴废机油混合制剂硬毛刷点涂蛀入孔和排粪孔,然后薄膜封缠蛀蚀干部的方法防治杨于象,药效持续时间长,防治效果较好,被害杨树伤口愈合较快。其次是注射2.5%溴氰菊酯350mL加10kg水混合制剂防治方法,适合幼虫期的杨干象防治,防治效果表现最佳。刀针锥刺法在滦平县最适合在5月上中旬的幼虫期,对表皮相对光滑坚硬的杨树树种进行杨干象防治,防治效果较好。杨干象成虫防治在成虫始化期采取2.5%溴氰菊酯350mL加10kg废机油混合制剂涂毒环阻隔法防治效果较好。 相似文献
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抗冲性是土壤生态系统在抵抗面状侵蚀和线状侵蚀过程中所表现出的一种重要性能,主要受植物群落和土壤特征的影响。通过采用索波列夫抗冲法试验,结果表明:①退耕还林3年后,林地10、30、50 cm三个土层的平均产流历时比坡耕地延长1.2、0.87、0.52 s,地表迳流量比坡耕地减少5.216、4.286、2.613 L/m2,土壤抗冲性比坡耕地增强0.277、0.255、0.206 kg/(m2.min);②土层越深,退耕还林对土壤产流历时的延长效应就越短,对土壤产流量的减弱效应就越小,对土壤抗冲性的强化效应就越低;③退耕还林对坡面产流历时的延长效应、对坡面产流量的减弱效应及对土壤抗冲性的强化效应随土壤母质的不同而差别很大。 相似文献
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福州国家森林公园的森林绿量(叶面积)为847.6万m2,每天固定CO2310t,放出氧气226t。可供福州市目前1/3,人口呼吸耗氧。
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