不同林分类型樗蚕自然种群动态规律

该文研究了３种林分类型樗蚕Ｐｈｉｌｏｓａｍｉａ ｃｙｎｔｈｉａ自然种群动态。结果表明：樗蚕世代内种群数量吴不断减少趋势；在各虫期中，１～２龄幼虫存活率最低，卵期存活率最高；不同世代间，第１代存活率高于第２代；在不同林分类型中枣粮间作存活率最低，而是椿片最高。在不同世代间各虫期的死亡原因和死亡率及变异程度有所不同，在不同年度间以蛹期死亡率变异最大；在不同林分类型中枣粮间作类型中樗蚕世代总死亡率及各虫期死亡率高于臭椿片林和臭椿行道树。     

樗蚕发生规律及其防治

本文详细调查了樗蚕 (PhilosemiacynthiaWalkeretfelder)的生物学特性、危害习性、形态特征、生活史、寄主植物 ,进行了防治试验 ,提出了综合防治措施。     

樗蚕的发生规律与综合防治

樗蚕Ｐｈｉｌｏｓａｍｉａｃｙｎｔｈｉａ危害椿树及泡桐、石榴。在河间市一年可发生２～３代,１代历期为８０～９０天,以幼虫危害寄主叶片,总食叶量可达到４０６．８６ｃｍ２／头。樗蚕的发生程度主要取决于气候条件,特别是温、湿度适宜与否。其次是受越冬蛹基数、寄主树种的多寡以及天敌数量的影响,在防治上应采取综合防治的措施,如人工消灭越冬蛹和大龄幼虫法、灯光诱杀成虫法,以减少幼虫发生量。药剂防治必须掌握在幼虫孵化盛期至３龄前这一关键期。     

樗蚕的发生规律与综合防治

樗蚕Ｐｈｉｌｏｓａｍｉａｃｙｎｔｈｉａ危害椿树及泡桐，石榴，在河间市一年可发生２～３代，１代历期为８０～９０天，以幼虫危害寄生叶片，总食叶量可达到４０６．８６ｃｍ＾２／头，樗蚕的发生程度主要取决于气候条件，特别是温，湿度适宜与否，其次是受越冬蛹基数，寄主树种的多寡以及天敌数量的影响，在防治上应采取综合防治的措施，如人工消灭越冬蛹和大龄幼虫法，灯光诱杀成虫法，以减少幼虫发生量，药剂防治必须掌握在幼虫     

樗蚕预测预报技术研究

该文通过对樗蚕大量的室内和野外调查，对其发生期和发生量进行了研究，建立了越冬代成虫羽化始盛期和以蛹重估计卵量的预测模型，从而为确定防治适期，预测发生程度，提供了可靠的技术方法。     

樗蚕生物学特性与防治

樗蚕在荆州市1年发生2代,以蛹越冬.第一代幼虫期6月上旬～7月中旬,危害盛期为6月下旬;第二代幼虫期8月下旬～10月上旬,危害盛期为9月中旬.人工剪除越冬茧蛹,成虫羽化盛期使用黑光灯和杀虫灯诱杀,可降低虫口基数.在低虫口密度时,采取生物制剂防治和保护利用天敌的措施,可以有效控制樗蚕的发生和危害;在高虫口密度时,使用高效、低毒、低残留的无公害药剂喷雾防治,可以迅速压低虫口密度.     

樗蚕生物学特性的研究

樗蚕（ＰｈｉｌｏｓａｍｉａｃｙｎｔｈｉａＷａｌｋｅｒｅｔＦｅｌｄｅｒ）在保定１ａ发生２～３代,以２代为主,以蛹在茧内于树上越冬。越冬代成虫羽化高峰期为５月８日,第１代成虫羽化高峰期为７月１６日。４龄幼虫排粪量为２６粒／头。４龄幼虫期平均抓着力为４２ｇ,５龄幼虫平均抓着力为１９５ｇ。樗蚕性比为雌∶雄＝１∶１０３。在河北省主要寄主植物有臭椿、臭檀、花椒、枣树、泡桐等,另外有１３种植物,共１８种,分别隶属于１６科。     

樗蚕的防治试验研究

通过对樗蚕幼虫的防治试验，确定了对其防治的有效方法。采用１０００倍液的乙基１６０５对体长５ｍｍ的幼虫有良好的防治效果；采用７００倍液的乙基１６０５或５００倍液的甲胺磷对体长８ｍｍ的幼虫有良好的防治效果，采用４００倍液的乙基１６０５对大龄幼虫有较好的防治效果。即随着幼虫体积的逐渐增长，所用药液的浓度也逐渐提高。     

樗蚕的发生与防治

近年来,樗蚕（Philosamia cynthia Walker etfelder）在蒙城县连续发生,对臭椿生长造成了不同程度的危害。县林业部门对樗蚕进行了调查、观察和防治试验,现已初步掌握该虫发生规律及防治要点。本文对樗蚕发生、危害特点及生物学特性进行了阐述,提出了以物理和生物方法为主要手段的可持续控制技术。     

越冬代樗蚕羽化始盛期预测初步研究

樗蚕(Philosamia cynthia Walker et Fetder)属鳞翅目大蚕蛾科。自1991年以来,在沧州市南皮县大量发生,1992年迅速扩散至全市各县及邻近地市,并暴发成灾,对重要乡土的绿化树种——臭椿造成严重的危害,个别地段树叶被吃光,影响了椿树的生长和环境美化,给林业生产和绿化事业造成严重损失,在食料不足时还可为害枣树、泡桐、石榴等树种。作者自1992年起对其越冬代成虫羽化情况进行调查,并对越冬代樗蚕羽化始盛期预测进行了研究,以对该害虫的有效防治提供依据。     

不同寄主树种樗蚕蛹重差异分析

运用野外随机取样与室内观测相结合的方法 ,系统研究了以臭椿、泡桐、枣树、石榴为寄主树种樗蚕蛹重之间的差异 ,初步探讨了樗蚕对寄主的适应性     

樗蚕生物学特性研究

樗蚕属磷翅目大蚕蛾科 ,是一种食量大、食性杂的暴发性害虫。通过 3年的试验研究 ,弄清了该虫在沧州市椿树上 1年发生 2～ 3代 ,且 8月 18日前化蛹的樗蚕可产生第 3代 ,以后化的蛹可直接越冬 ;枣树和其它寄主植物上的樗蚕 1年仅发生 2代 ,没有世代分化现象 ;同时摸清了各世代卵、幼虫、成虫的发生时期和历期 ,为科学防治提供了依据     

Estimating leaf area index in different types of mature forest stands in Switzerland: a comparison of methods

Leaf area index (LAI) was estimated at 15 sites in the Swiss Long-Term Forest Ecosystem Research Programme (LWF) in 2004–2005 using two indirect techniques: the LAI-2000 plant canopy analyzer (Licor Inc.) and digital hemispherical photography, applying several exposure settings. Hemispherical photographs of the canopy were analysed using Hemisfer, a software package that offers several new features, which were tested here: (1) automatic thresholding taking the gamma value of the picture into account; (2) implementation of several equations to solve the gap-fraction inversion model from which LAI estimates are derived; (3) correction for ground slope effects, and (4) correction for clumped canopies. In seven broadleaved stands in our sample set, LAI was also estimated semi-directly from litterfall. The various equations used to solve the gap-fraction inversion model generated significantly different estimates for the LAI-2000 measurements. In contrast, the same equations applied in Hemisfer did not produce significantly different estimates. The best relationship between the LAI-2000 and the Hemisfer estimates was obtained when the hemispherical photographs were overexposed by one to two stops compared with the exposure setting derived from the reading of a spotmeter in a canopy gap. There was no clear general relationship between the litterfall and the LAI-2000 or the hemispherical photographs estimates. This was probably due to the heterogeneity of the canopy, or to biased litterfall collection at sites on steep slopes or sites subject to strong winds. This study introduces new arguments into the comparison of the advantages and drawbacks of the LAI-2000 and hemispherical photography in terms of applicability and accuracy.     

Natural hybridization in seed stands of seven Mexican Pinus species

New Forests - Natural hybridization can manifest different evolutionary results, such as accelerating differentiation and facilitating speciation through the rapid origin of new biochemical...     

不同类型黑松混交林土壤微生物土壤酶和土壤养分含量的研究

对 3种类型黑松混交林及纯林的土壤微生物、土壤酶及土壤养分因子进行了测定和分析 ,结果表明 :各土壤类型土壤微生物数量、土壤酶的活性均表现出差异 ,混交林的土壤养分含量均高于纯林 ,尤以黑松×刺槐、黑松×麻栎混交林显著 ;土壤微生物数量、土壤酶活性与土壤养分含量之间呈显著相关关系     

封育柞蚕场蒙古栎林不同恢复阶段种群结构与群落多样性研究

采用空间代替时间的方法,以柞蚕场蒙古栎在平茬后经不同时间(9年、12年、57年)封育保护而形成的蒙古栎次生林及对照柞蚕场蒙古栎林(3年生)为研究对象,对辽东山区蒙古栎次生林不同恢复阶段的种群结构与群落多样性进行了深入分析。研究结果表明:随封育林龄的增长,乔木层蒙古栎种群所占的重要值比例在降低,蒙古栎林在恢复演替进程中不断向阔叶混交林的方向发展;灌木物种间的重要值差距在减小;草本层植物种类在不断减少;蒙古栎林优势种群径阶分布宽度增加,径阶分布趋向于正态分布。在封育不同恢复阶段,羊胡苔草重要值均表现为最大,是草本群落最主要的物种。不同恢复阶段林分乔木层、灌木层物种多样性表现为随封育林龄的增长而增大,草本层多样性表现为随封育林龄的增长而减小。     

浙江凤阳山不同林地类型土壤微生物季节动态

在浙江凤阳山自然保护区选取7个不同林地类型(常绿阔叶林、针叶林、针阔混交林、杉木林、毛竹林、柳杉林以及灌草林)采集土壤样品,分析了土壤细菌、真菌、放线菌在不同林地类型、不同土层及不同季节间的变化规律.结果表明:在不同林地类型间土壤微生物数量差异较大,三大类群微生物数量关系为细菌＞放线菌＞真菌;不同林地间,细菌数量以毛竹林土壤为最高,针叶林的最低;真菌数量以毛竹林最高,针阔混交林最低;放线菌数量以杉木林为最高,针叶林为最低.不同季节各林地土壤微生物类群数量的差异很大,其数量变化具有一定的季节性,细菌、放线菌表现出夏季＞秋季＞春季＞冬季的规律,而真菌则表现为秋季＞夏季＞春季＞冬季的规律.在土壤剖面上,随土层深度加深,土壤微生物类群数量呈现出减少的规律,表层土壤微生物含量最高.     

Natural regeneration in patch clear-cutting in Picea abies stands in Southern Finland

Abstract

The success of natural regeneration on patch clear-cuts in Norway spruce stands in Southern Finland was examined in terms of stocking and tree height. The experiment was established in mature spruce stands in the submesic Myrtillus (MT) site type. In each of the eight study sites, three plots were treated with clear-cutting and planting, clear-cutting with partial tree retention and planting, and patch clear-cutting without site preparation, respectively. In three of the study sites, one plot with patch clear-cutting and site preparation was established. Each plot was 1 ha, out of which three patches of 40×40 m were clear-cut in the patch treatments. 10–11 years after cutting, the patches had on average 1316 crop trees ha^–1, of which 91% were spruces. Some 27% of the stands were up to the target stocking level (≥1600 ha^?1), and 36% were at least satisfactory (≥1300 ha^?1). Site preparation did not yield greater stocking levels on patches, but that result is ambiguous due to a difference in initial stocking. The average spruce tree height in the patches (0.76 m) was much smaller than in the case of clear-cutting and planting (2.42 m). In conclusion, the patches had been restocked tolerably well with spruce and birch for practical purposes during the 10- to 11-year period, but the regeneration process had been very slow compared to clear-cutting and planting.     

不同坡向对栓皮栎耗水规律的影响

利用热扩散探针配合自动气象站,于2004年度在北京林业大学妙峰山试验林场对不同立地条件下栓皮栎的水分运移规律进行了研究.结果表明：栓皮栎水分运移规律受天气状况和立地条件的影响很大.在晴天,阳坡的液流峰值达到0.007 cm/s,是阴坡液流峰值0.001 5 cm/s的5倍;在阴天,阳坡栓皮栎的液流峰值为0.000 2 cm/s,而阴坡为0.000 3 cm/s,坡向的影响减小.林木的耗水量受到树种本身的遗传因素和外界气候因子的制约,其中太阳辐射、大气温度、风速与液流呈正相关,空气相对湿度、土壤温度对液流的影响表现为负向相关.