A harvest failure approach to assess the threat from an invasive species

We present the idea of using potential infringements on annual allowable harvest targets as an approach to estimate threats from invasive species to the forest products sector. The approach uses present-day harvest levels as a reference level to estimate when and where the impact of a nonnative forest pest could become economically damaging. We use a generic model that simulates spread and damage by nonnative invasive species, basic harvest and forest growth through time. The concept is illustrated with a case study of a new nonnative invasive pest, Sirex noctilio Fabricius on pine resources in eastern Canada. Impacts of invasion on wood supply, in particular, the point at which present-day harvest levels are not attainable, were identified for 77 non-overlapping geographical regions that delimit the primary wood supply areas around large mills and wood processing facilities in eastern Canada. The results identify the minimum area of a pest outbreak that could trigger harvest shortages (approximately 12.5–14 M ha of pine forests in Ontario and Quebec). Beyond this level, the amount of host resource available for harvesting in any given year declines rapidly. The failure to sustain broad-scale harvest targets may be an attractive and intuitive indicator for policy makers and regulators interested in developing control and “slow-the-spread” programs for non-native forest pests.     

Movement distances enhance validity of predictive models

Including the distance species are able to move in predictive models improves conservation practice. Bird inventory projects carried out from 1993 to 2004 in Taiwan provide an opportunity to investigate the relationships among species distribution, movement distance, and the environment. We compared projected distributions of 17 Taiwanese endemic bird species using what we called the Standard Method (i.e. movement distance is zero) and what we called the Buffer Method (i.e. movement distance is longer than zero) in three presence-only models (GARP, MAXENT and LIVES). The Standard Method used species original occurrence records directly while the Buffer Method expanded the occurrence of species to areas 1 km² around each recorded location. We first tested the efficacy of the Buffer Method using ten common species of the 17, and then applied the method to two rare species of the 17. For both the common and rare species, the distributions predicted by the two methods showed slight but important differences. The Buffer Method for all species had a higher average predictive probability, while the Standard Method had a higher maximum predictive probability. Most of the values for the area under the curve (AUC) were over 0.8 with the exceptions of Taiwan Barbet (Megalaima nuchalis) and Taiwan Hwamei (Garrulax taewanus), which have recently separated from Indochinese Barbet (Megalaima annamensis) and Chinese Hwamei (Garrulax canorus), and since 2008 and 2006 have been regarded as species endemic to the study area. Kappa values showed good performance for all species using both methods. The Buffer Method, however, resulted in significantly higher sensitivity and accuracy values for all models of species (p < 0.05). We conclude that when modeling species distribution including the area where the species was censused along with areas within the minimum movement areas better defines the surrounding areas that might supplement core habitat requirements. Therefore, using the Buffer Method, species surrounding distribution can be obtained which provides a better understanding of the species distributions. Given that distribution size is a key to the conservation of species, we suggest the Buffer Method can be used in conservation planning.     

高寒草原菌根围细菌数量对丛枝菌根真菌物种多样性的影响

基于丛枝菌根真菌(Arbuscular mycorrhizas fungi,AMF)孢子形态学鉴定,研究了藏北高寒草原主要建群植物菌根围细菌数量对AMF物种多样性的影响.结果表明:1)细菌数量1.02×106～2.96×106、3.01×106～6.06×106个/g范围内,Glomus、Acaulospora均为优势属,Scutellospora则均为最常见属;AMF孢子密度、分离频度、相对多度、重要值和种的丰度(SN、SR)均呈Glomus>Acaulospora>Scutellospora属的趋势.2)细菌数量较低时(<3.0×106个/g),AMF各属孢子密度、种的丰度(SR)相对较高,Shannon-Weiner指数、物种均匀度指数亦较高,分别达1.774和0.127.3)不同细菌数量条件下,孢子密度随细菌数量的增加而均呈微弱下降,菌根侵染率、侵染强度、丛枝丰度则均呈不同程度的提高.细菌数量>3.0×106个/g时,菌根侵染率、侵染强度和丛枝丰度随细菌数量增加而提高的趋势尤为明显.4)不同细菌数量条件下,AMF种的构成呈共有种、共有优势种较多(Glomus属均占绝对比重),特有种、稀有种较少,以及不同优势种孢子密度、相对多度和重要值差异均较悬殊的分布特征.图6表3参25     

祁连山青海云杉群落物种组成及α多样性垂直分布

通过对祁连山自然保护区青海云杉群落物种组成及α多样性垂直分布格局的研究,结果表明：祁连山自然保护区青海云杉群落内有维管植物25科51属96种,其中乔木4种,灌木29种,草本62种;植物种相对集中分布于海拔2 680～2 890 m的阴坡;随海拔梯度升高,群落内植物种数减少,且相邻样地的共有种数呈不明显的先减少而后增加的趋势,Margalef指数、Shannon-Wiener指数和Pielou指数呈降低趋势;不同林型的植物种的丰富度依次为：青海云杉混交林〉草类-青海云杉林〉苔藓-青海云杉林〉灌木-青海云杉林〉马先蒿-青海云杉林。     

鼎湖山20公顷森林样地单个物种对群落的构建

大型固定监测森林样地已成为研究森林群落组织机制的一个重要平台。群落里个体之间的相互作用对群落的构建有相当重要的作用。以往的研究主要针对于物种之间的相互作用,而用群落里单个物种与其它所有个体之间相互关系来解释群落构建的研究还很少。采用单个物种-面积关系（ISAR）这一指标对鼎湖山20 hm2样地和BCI 50 hm2样地数据分析,来研究不同样地单个物种是如何对森林群落进行构建的。结果显示,与BCI样地和Sinharaja样地不同,鼎湖山样地大树对周围其它个体的作用几乎是中性的;而对于小树（胸径小于10 cm）来说,鼎湖山样地和BCI样地一样,随着尺度的增加＂吸引型＂物种减少,而＂中性＂物种增加。说明了不同的群落在不同的发育阶段,单个物种对群落结构的构建有重要的作用不同,将来的研究应该结合群落其它方面的因素来分析群落内个体之间相互作用,例如从时间尺度的谱系和空间因素去分析。     

不同地理分布区中国林蛙的身体特征变异

采用形态比较学和数值分类相结合,对中国山西、辽宁、内蒙古等地的中国林蛙各居群的身体特征进行探讨.通过对大量标本的测量分析,结果认为:随着地理经纬度的变化和生境的转移,林蛙的各项身体特征表现出一定程度的变异.愈靠近东北林蛙分布区,其个体愈大,各项数据比对差异明显,从而可初步界定中国林蛙与东北林蛙的分界线.     

温带阔叶红松林中不同树种和倒木对土壤性质的影响

以长白山温带阔叶红松林为研究对象,通过野外采集土壤样品,综合研究老龄树及倒木对周边表层土壤性质的影响。研究结果显示,在本研究样地条件下,不同树种周边的表层土壤性质存在显著性差异,红松（Pinus koraiensis）周边土壤中水溶性有机碳WSOC的质量分数和特征吸光系数SUVA254值都高于紫椴（乃砌amurensis）和水曲柳（Fraxinus mandshurica）,但是土壤水溶性总氮WSTN和交换性无机氮的质量分数却是红松低于紫椴和水曲柳。对倒木影响的森林表层土壤性质的研究结果显示,倒木下方森林表层土壤中WSOC、WSTN以及交换性矿质氮的质量分数都明显地高于林间土壤,说明在小尺度空间区域内,倒木可能是森林表层土壤活性碳、氮库的重要输入源。此外,本研究还利用主成分分析探讨了受树种影响的森林表层土壤不同性质之间的关联性,并对树种和倒木影响周边土壤性质的可能性机制进行分析。     

基于景观中性模型的不同竞争力外来种入侵对栖息地毁坏的响应

栖息地毁坏和生物入侵被认为是全球物种多样性的两大威胁,也是当前研究的热点。同时,两者的共同作用将比单独作用所带来的物种多样性丧失更大。本文基于竞争-扩散均衡机制,考虑了外来种的不同竞争力,结合景观中性模型和元胞自动机模型,模拟了外来种入侵对栖息地毁坏（栖息地破碎和面积丧失）的响应。研究结果表明：1）外来种入侵成功将首先威胁竞争力与其相邻的弱物种;2）栖息地毁坏与种间竞争共同决定着外来种入侵的成功与否。当栖息地破碎促进了与外来种竞争力相邻的本地强物种时,将会抑制入侵;当其抑制了与外来种竞争力相邻的本地强物种时,则会促进入侵。当栖息地丧失促进了外来种相邻的本地强物种时,将会抑制入侵;当栖息地丧失抑制了外来种相邻的本地强物种,将一定程度地促进入侵,但随着丧失面积的增加,则转为抑制。因此,为了抑制不同竞争力的外来种入侵,应采取不同的栖息地保护策略,并保护和促进其竞争力相邻的本地强物种。     

不同粒径纳米TiO2对大型溞的毒性效应及腐殖酸的调控作用

为评估纳米TiO₂在环境水体中的暴露风险,选用大型溞作为模式生物,研究了不同粒径纳米TiO₂（20、40、60和100 nm）对大型溞毒性效应的影响,并探究了腐殖酸对不同粒径纳米TiO₂毒性效应的调控作用.结果表明,粒径是影响纳米TiO₂颗粒毒性效应的重要因素,以大型溞半数致死时间（LT₅₀）为指标,不同粒径纳米TiO₂对大型溞的毒性作用强弱顺序依次为：20 nm颗粒 > 40 nm颗粒 > 60 nm颗粒 > 100 nm颗粒（p<0.05）.腐殖酸的存在可以显著降低纳米TiO₂颗粒对大型溞的毒性作用,腐殖酸对小尺寸纳米TiO₂颗粒的毒性抑制作用更为明显（p<0.05）.大型溞体内ROS水平与抗氧化系统相关酶活分析表明,纳米TiO₂导致大型溞体内活性氧自由基（ROS）浓度升高是其产生毒性作用的重要原因,腐殖酸的存在可以显著降低大型溞体内由于纳米TiO₂暴露而引起的ROS浓度上升（p<0.05）,进而减轻纳米TiO₂对大型溞的毒性作用.此外,腐殖酸可以减小不同粒径纳米TiO₂之间的毒性差异.本研究结果可为纳米TiO₂在环境水体中的暴露风险评估提供参考依据.     

氮磷比对湖泊富营养化模型参数敏感性的影响

运用Morris方法研究了蓝藻暴发期不同氮磷比条件下,巢湖富营养化模型中蓝藻、溶解有机碳、营养物和溶解氧的参数敏感性.结果表明：蓝藻的敏感参数随氮磷比不同有显著差异;氮缺乏情况下,蓝藻对氮转化过程相关参数较敏感;磷缺乏情况下则反之.在任何氮磷比条件下,溶解有机碳、营养物和溶解氧等非生物变量都是对直接参与其自身转化过程的参数最为敏感,它们在不同氮磷比情况下的敏感参数差异较小.相比较蓝藻生长过程的参数,基础代谢过程的参数对所有变量的影响都更强.此外,各个参数的敏感性与它们的相互作用强度呈显著正相关,且这种相关性在极端氮或磷缺乏情况下尤为显著.本研究的结果有助于深入理解湖泊富营养化现象、改善富营养化模型模拟效果和精度.