云南丽江地区铁杉球蚜发生与环境因子的关系

铁杉球蚜Adelges tsugae Annand(Hemiptera:Adelgidae)是铁杉的主要害虫,在北美造成铁杉成片死亡。为有效地寻找控制铁杉球蚜的天敌,作者于2005年8~2006年12月,在云南省丽江地区的河源、牦牛坪、黑水河3个地点对铁杉球蚜的发生进行6次调查,统计不同树枝方位、不同树冠层次、不同取样地点、不同取样时间的铁杉球蚜的为害率。在多数情况下,铁杉北向和南向树枝上的球蚜为害率高于西向和东向;树冠下层的铁杉树枝上的球蚜为害率高于树冠上层;5月树冠上层球蚜为害率反而高于下层,树冠层次球蚜密度随着时间而变化的现象,与铁杉球蚜第2代发生高峰期相吻合。3个地点的每株树铁杉球蚜为害率平均为24.6%,河源的球蚜为害率又高于牦牛坪和黑水河。对来自3个地点的12块样地的每样地铁杉球蚜为害率与环境因子进行偏相关分析表明,坡向、年均相对湿度、年均降雨量与铁杉球蚜发生呈显著正相关。在调查铁杉球蚜的发生或采集球蚜天敌昆虫时,应在不同时间依据树枝方位和树冠层次来分别进行。在选择调查采集地点时,应以林区坡向、相对湿度、降雨量等环境因子为依据。     

斑翅肩花蝽对铁杉球蚜的捕食作用

室内用铁杉球Adelges tsugae Annand(Hemlock woolly adelgids)蚜卵、1～4龄若虫、成虫饲养斑翅肩花蝽Tetraphleps galchanoides Ghauri,研究斑翅肩花蝽对铁杉球蚜Adelges tsugae Annand(Hemlock woolly adelgids)的捕食效应。结果表明,斑翅肩花蝽对铁杉球蚜的捕食功能反应属于HollingⅡ型反应,对球蚜密度的捕食干扰反应可能存在种内的干扰作用。对于同一发育期同一密度猎物,斑翅肩花蝽成虫或若虫在高密度条件下的日均捕食量均显著高于低猎物密度下的日均捕食量;而对于不同发育期不同密度猎物,斑翅肩花蝽在低猎物密度时对测定的铁杉球蚜6个不同虫态无明显选择性;在中、高密度时斑翅肩花蝽对测定的铁杉球蚜的不同虫态表现出明显喜好性差异,若虫最喜好食铁杉球蚜卵和1龄若虫,成虫最喜好食铁杉球蚜4龄若虫和成虫。为评价和利用斑翅肩花蝽对铁杉球蚜防治作用进行了讨论。     

麦长管蚜空间分布型及抽样技术的研究

本文运用4年调查资料,通过丛生指标、聚块性指标的测定,阐明了麦长管蚜空间分布为聚集分布。并进一步用Taylor的幂法则,-M回归分析法,-M模型的改进型测定分布格局的内在结构。得出当t=1、D=0.2时的理论抽样数为:n=130.9325/m+7.075。如果防治指标为10头/株,得出复合序贯抽样的累积虫量界限为:T_0(N)=10N±8.9818 N~(1/N),T(N)=exp(6.7024—0.3506lnN)。它比单纯的序贯抽样提高了工作效率。     

中国特有植物长苞铁杉的生物学特性及其保护

长苞铁杉（Tsuga longibracteata）属松科铁杉属,长苞铁杉组（Sect．Heopence Keng et Keng f.）, 为我国特有树种;现正处在濒危状态,已被列为国家三级保护植物。本文比较系统地综述了长苞铁杉的 生物学特性,包括其外部形态、内部结构、染色体核型、地理分布、生长特性及材性、生态学和群落特性 等。关于长苞铁杉的分类位置,一直争论不休。作者在比较了各种分类观点后,根据上述特性的分析结 果,支持建立长苞铁杉属（Nothotsuga）的主张。最后,文章分析了可能引起长苞铁杉濒危的原因,并提出 了两点保护措施。     

江西武夷山珍稀濒危植物南方铁杉种群动态与空间分布

明晰江西武夷山国家级自然保护区内180年生的珍稀濒危植物南方铁杉(Tsuga chinensis var.tchekiangensis)的种群特征,并提出针对性的保护策略,对南方铁杉种群的就地保护具有现实意义。通过分析保护区内6.4 hm~2动态监测固定样地的南方铁杉种群数据,编制了静态生命表,绘制了存活曲线、死亡率和消失率曲线、生存函数曲线,采用了时间序列模型对种群数量特征进行未来预测;同时,运用点格局分析Ripley′s K函数中的成对相关函数g(r)判断不同生长阶段的南方铁杉种群在不同尺度下的空间分布格局。结果表明：(1)南方铁杉种群的年龄结构呈“金字塔”型,属于衰退型种群;各龄级间的数量变化动态关系显示该种群在当前阶段呈增长型,但是种群的天然更新能力较差;(2)南方铁杉种群的存活曲线表现为Deevey-I型,种群个体在进入生理死亡阶段后产生一定的波动;(3)南方铁杉种群的生存率随龄级增加而逐渐下降,累积死亡率逐渐递增;死亡密度整体偏低,在第1—2龄级较高,总体波动幅度较小;危险率曲线总体呈现上升的趋势;(4)在经过不同龄级的时间后,南方铁杉幼龄树数量降低,中龄树和老龄树数量持平...     

珍稀濒危植物长苞铁杉的分布格局

应用聚集度指标,Ｉｗａｏ方程和Ｔａｙｌｏｒ幂法则模型等测定方法研究珍稀濒危植物长苞铁杉的空间分布格局。结果表明,长苞铁杉的空间分布呈随机分布。文中还研究Ｉｗａｏ的Ｍ与ｘ的回归方程,计算长苞铁杉在不同密度和允许误差下的理论抽样面积。     

长苞铁杉的生态生物学特性

长苞铁杉(Tsuga longibracteata Cheng)是我国特有的珍稀树种,第四纪冰川期遗留下来的古老、孑遗植物,是大果铁杉组(Sect.Hesperopeuce)分布于中国的唯一代表种类,国家重点保护植物[1,2].零星见于福建、江西、广东、广西等省区的局部地区.     

苹果绵蚜在苹果树上空间分布型的研究

采用6种空间分布型聚集度指标,测楚了苹果绵蚜在苹果树新梢、侧枝、树干(环剥处)和根部的空间分布型。结果表明均呈聚集分布,据此提出了适宜的调查取样技术。     

应用BioMod集成多种模型研究物种的空间分布——以铁杉在中国的潜在分布为例

新型统计方法和多源、多尺度空间信息数据的产生促进了物种空间分布模型的快速发展。不同的物种空间分布模型在生态学理论的运用以及前提假设上存在差异。选用不同的模型方法和输入数据会带来预测结果的不确定性。对比并集成多个物种空间分布模型,同时利用多组输入数据可降低预测的不确定性,提高物种分布模拟的精度。本文以中国特有种铁杉（Tsuga chinensis）为例,运用基于R语言开发的BioMod软件包对比9个物种空间分布模型对铁杉的模拟效果。最后以曲线下面积（ROC）为权重集成9个模型的模拟结果,产生和筛选最佳的铁杉潜在空间分布图。研究发现随机森林模型（RF）的模拟效果最好,其次是多元适应回归样条函数模型（MARS）和广义相加模型（GAM）,模拟效果最差的是表面分布区分室模型（SRE）。模型集成结果显示,最适宜铁杉分布的区域集中在中国的西南及四川盆地周围,其次零星分散于华南和台湾部分地区。这一结果与前人对铁杉自然分布的描述和研究结果较为吻合。研究进一步表明,通过模型的集成能有效地降低由于单个模型所带来的模拟结果不确定性,从而提高模拟的精度和效果。     

Recovery of Sasajiscymnus tsugae,released against hemlock woolly adelgid,Adelges tsugae,in the southern Appalachians

Eastern hemlock in the Great Smoky Mountains National Park is currently threatened by the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae). As part of a management plan against this invasive insect pest, about 350,000 adults of the predatory beetle Sasajiscymnus tsugae (Sasaji and McClure) (Coleoptera: Coccinellidae) were released at ca. 150 sites in the Park from 2002 to 2007. Of these adult release sites, 33 were sampled in 2008 and 2009 using beat-sheet sampling for 4 man-hours. Sasajiscymnus tsugae adults (n=78) and/or larvae (n=145) were recovered from seven sites (21.2% of the release sites sampled). Recovery of S. tsugae was significantly associated with older release sites, with the most beetles recovered from 2002 release sites. These results indicate that S. tsugae may require more time (i.e., 5–7 years) than anticipated for population densities to reach readily detectable levels in some areas.     

Factors affecting settlement rate of the hemlock woolly adelgid,Adelges tsugae,on eastern hemlock,Tsuga canadensis

1 We assessed the importance of several factors potentially affecting the settlement rate of the invasive hemlock woolly adelgid Adelges tsugae (Hemiptera: Adelgidae) on uninfested foliage of the eastern hemlock, Tsuga canadensis. We conducted our experiments in Massachusetts (U.S.A.) with overwintering sistens adelgids, and applied standard densities of infested foliage to uninfested branches in a planned multiple‐comparison design. 2 Settlement rates of progrediens crawlers produced by the overwintering sistens were highest when adelgid‐infested foliage was loosely attached to uninfested foliage and both branches were then enclosed in a mesh sleeve. 3 Early‐emerging crawlers settled at a higher rate than did late‐emerging crawlers. 4 Increasing the density of infested branches did not affect settlement rates. 5 We also tested whether less severe winter conditions improved settlement, and found that overwintering infested foliage in a refrigerator decreased settlement rate relative to foliage overwintered outdoors. 6 Our results suggest a protocol for adelgid inoculations that could substantially increase the success rate of experimental manipulations and encourage additional research on the population dynamics of this pest.     

Establishment and coexistence of two predators,Laricobius nigrinus and Sasajiscymnus tsugae,introduced against hemlock woolly adelgid on eastern hemlock

The coexistence of two introduced predatory species, Laricobius nigrinus Fender and Sasajiscymnus tsugae (Sasaji and McClure), and a native predator, L. rubidus LeConte, on eastern hemlock was documented for the first time. Details of their coexistence and implications to management of hemlock woolly adelgid, Adelges tsugae Annand, are discussed.     

Spatiotemporal distribution of the hemlock woolly adelgid predator Laricobius nigrinus after release in eastern hemlock forests

• 1 Post‐release distributions of Laricobius nigrinus, a biological control predator of hemlock woolly adelgid Adelges tsugae Annand, were evaluated at eight hemlock forests in the eastern U.S.A.
• 2 Vertical dispersal of F₁ and F₂L. nigrinus were assessed from within three crown strata (<7, 7–15 and >15 m) at four release sites.
• 3 Horizontal distributions of L. nigrinus within the forest surrounding central release areas were observed in two separate studies, which included (i) release and monitor to capture parent and F₁ movement by sampling the immature life stages of the offspring, and (ii) assessment of F₃ to F₆ generations where beetles were previously determined to be established.
• 4 Laricobius nigrinus, released on lower crown branches, oviposited within the upper crown stratum and were slow to disperse from release trees. Monitoring L. nigrinus only from the lower crown would likely underestimate its presence because 86% of the F₂ generation were detected above 15 m.
• 5 By the fifth generation, the frequency distributions of larvae increased at increasing distance from release areas; larvae were recovered at a maximum distance of approximately 400 m and the spread rate was approximately 39 m/year.
• 6 Slow dispersal of L. nigrinus and uninterrupted recovery of six generations in the presence of fluctuating prey density support its continued release as part of the A. tsugae biological control programme. These data contribute toward improved release strategies and monitoring for this biological control agent.

     

Seasonal synchrony of life cycles between the exotic predator,Pseudoscymnus tsugae (Coleoptera: Coccinellidae) and its prey,the hemlock woolly adelgid Adelges tsugae (Homoptera:Adelgidae)

1 The seasonal synchrony between the exotic predator, Pseudoscymnus tsugae and its prey, the hemlock woolly adelgid, Adelges tsugae, was investigated in field cages and in the forest in Connecticut, U.S.A. from 1997–1999. 2 In early spring, egg to adult development took 45 d at 18.7 °C, 39.7 d at 20.2 °C and 31.5 d at 22.7 °C. Earliest emerging F1 adults mated and oviposited in the same year. whereas F1 and F2 females emerging later in the summer mated and reserved most of their egg complement for the following year. 3 A second generation of P. tsugae is possible in Connecticut but may be delayed by cool mid‐spring temperatures. Individuals of three generations of P. tsugae, including overwintering survivors, may coexist in July and August and adults can be found year‐round with A. tsugae in infested hemlock forests. 4 A linear regression model for development from egg to adult under field temperatures gave good agreement with results from constant temperature findings. The model predicted a lower development threshold of 9.5 °C and a sum of effective temperatures of 405 day °C. Development time of P. tsugae is shorter relative to its prey A. tsugae and generation time ratios of predator to prey was 0.16–0.5, with an advantage conferred on the coccinellid. 5 Overwintering ability and behaviour were determined in 1998–1999 and adults remained on infested hemlock branches throughout a mild winter, becoming reproductively active in mid‐April. Peak oviposition period extended from April to July, in synchrony with peak oviposition and developing stages of two generations of A. tsugae.     

The tree crown distribution of hemlock woolly adelgid, Adelges tsugae (Hem., Adelgidae) from randomized branch sampling

Abstract:  An exotic insect, the hemlock woolly adelgid, Adelges tsugae Annand (Hem., Adelgidae), is spreading through eastern North America, killing hemlock trees [ Tsuga canadensis (L.) Carrière], and thereby impoverishing ecosystems. Adelges tsugae , like many alien invasive insects, is difficult to monitor or sample in the forest. Monitoring of A. tsugae has been hampered by lack of information about its distribution within tree crowns. In order to assist future monitoring and biocontrol of A. tsugae , this study investigates the crown distribution of A. tsugae by sampling from the entire height of mature hemlock trees in a forest with an established infestation. In addition to A. tsugae , sampling includes scale insects, which are another group of important pests on hemlock trees. This study demonstrates the utility of a randomized branch sampling (RBS) plan for monitoring both invasive insects as well as native insects that are difficult to sample. Results from the RBS show that in trees with high populations of A. tsugae , branches from the lower crown have slightly higher densities of A. tsugae than upper crown branches. In trees with low A. tsugae populations, the upper crown may have higher A. tsugae densities than the lower crown. North pointing branches also have higher densities of A. tsugae than branches pointing in other cardinal directions. Future sampling efforts for A. tsugae can take advantage of higher densities in certain portions of the crown to increase accuracy.     

Competitive interactions among two specialist predators and a generalist predator of hemlock woolly adelgid, Adelges tsugae (Hemiptera: Adelgidae) in south-western Virginia

1 Competitive interactions among two specialist predators, Laricobius nigrinus and Sasajiscymnus (Pseudoscymnus) tsugae, and a generalist predator, Harmonia axyridis Pallas, of hemlock woolly adelgid, Adelges tsugae were evaluated in hemlock stands in south‐western Virginia. The two specialist predators are part of a biological control program for A. tsugae, and the potential for competition among these species and previously established generalist predators in the field is unknown. 2 Adult predators were evaluated in branch cages during spring and summer at two field sites infested with A. tsugae. Using females only in 2003 and sexual pairs in 2004, predator survival and net reproduction were examined, as well as their feeding and impact on A. tsugae when present alone and in conspecific and heterospecific groupings. 3 Predator survival was not affected by the presence of additional predators. Total feeding was greater for all species when placed in predator groupings, suggesting that interactions do not significantly interfere with feeding activity. Net reproduction per predator was negatively affected by conspecifics, but unaffected by heterospecifics, indicating that direct or indirect intraspecific interference may occur. In spring, L. nigrinus showed the greatest impact on A. tsugae, and H. axyridis had the greatest impact during summer. 4 These results suggest that it would be beneficial to utilize multiple predator species combinations over single species when implementing biological control for A. tsugae. Low‐density releases are also recommended to reduce intraspecific interference.     

Changes in the regional abundance of hemlock associated with the invasion of hemlock woolly adelgid (Adelges tsugae Annand)

Since its introduction, the non-native hemlock woolly adelgid (Adelges tsugae) has spread to infest hemlock (Tsuga spp.) in at least 18 states in the eastern USA. Previous studies have documented highly variable rates of hemlock mortality among infested stands making it difficult to estimate regional impacts. Here data from the US Forest Service Forest Inventory and Analysis program collected from 432 eastern U.S. counties reveals several surprising and conflicting regional patterns. First, median live and dead hemlock basal area has generally increased over the last two decades across the eastern U.S. This has generally been the case in both infested and uninfested counties. Second, the median percentage of hemlock which is alive has decreased over the past ~20 years, again in both infested and uninfested counties. Third, the ages of infestations are negatively correlated with the percentage of live hemlock, as might be expected given the known impact adelgids can have on a stand through time; however this relationship depends on the exclusion of uninfested counties, as counties infested >12 years and uninfested counties have similar percentages of live hemlock. Combined, these data suggest increasing tree density associated with the past century of reforestation and succession in the eastern U.S. may currently be overwhelming the negative impacts of the adelgid at the regional scale, however, the long-term stability of this situation is not known, and data from long-infested counties suggest the landscape may be at a “tipping point”.