试论人工林下乡土树种定居限制问题

人工林的生态系统服务功能比天然林差,多数人工林林下难以有乡土树种入侵并定居,如何改造并促进这些人工林向天然林或次生林演替并提高生态效益,已成为制约区域林业可持续发展的关键问题.在阐述定居限制原理的基础上,本文从种类特性、限制发生时间、影响定居的内外因素等方面概括了森林更新或恢复中的定居限制问题,认为人工林林下乡土树种的定居限制主要由种子的可到达性及环境条件所决定.基于恢复生态学中有关森林恢复的理论,提出应对不同时空尺度上植物更新过程中的种子和幼苗存活的影响因素进行整合.     

海南濒危树种保育圃白木香与降香黄檀幼苗根部真菌谱系与生态型多样性比较

【背景】根部真菌是影响植物幼苗存活、定植和生长的重要因子之一,但是苗圃培育的幼苗根部真菌物种组成与生态学特性尚不清楚。【目的】研究苗圃培育的白木香(Aquilaria sinensis)与降香黄檀(Dalbergia odorifera)幼苗根部真菌群落谱系与生态型多样性,以及宿主植物对根部真菌群落结构的影响。【方法】采集幼苗根尖样品提取基因组DNA,用真菌通用引物与丛枝菌根真菌(AMF)特异性引物扩增真菌r DNA-ITS区,经克隆、测序、序列分析鉴定真菌。通过基于核酸与Metadata数据关联分析的FUNGuild软件,划分根部真菌的营养型和共位群。采用非公制多维尺度分析法(NMDS)研究幼苗根部真菌群落物种组成差异与宿主植物物种及形态指标的关系。【结果】白木香与降香黄檀幼苗根部真菌物种丰富,达51个OTU;谱系多样性较高,涉及毛霉菌门(Mucoromycota,51%)、子囊菌门(Ascomycota,43%)以及担子菌门(Basidiomycota,6%)。这些根部真菌涉及不同的营养型与共位群,包括共生型真菌29种,频度较高的如Glomeromycetes sp.2、Rhizophagus irregularis等,二者均属于AMF共位群;腐生营养型真菌5种,如Talaromyces pinophilus、Rhizopycnis vagum等;病原型真菌2种,是Mycoleptodiscus sp.和Fusarium phaseoli;还有15种其生态类型不确定。NMDS分析结果表明,宿主植物物种、株高、地径、叶面积对根部真菌群落物种组成的影响不显著。然而,株高对AMF群落的物种组成有较弱的影响。【结论】本苗圃条件下,土壤中本土性根部真菌繁殖体较为充足,白木香与降香黄檀幼苗根部真菌群落谱系多样性较高,多种营养型与共位群的根部真菌共存;此外,采用真菌通用引物对ITS1F/ITS4研究根部真菌群落物种多样性时,AMF多样性可能会被极度低估。     

Changes in fish assemblages in catchments in north‐eastern Spain: biodiversity,conservation status and introduced species

1. North‐eastern Spain is a hot spot for the introduction of alien fish species, and its native fish fauna is one of the most endangered worldwide. We used an extensive data set from 2002 to 2003 and historical information from the area to characterize fish diversity and establish conservation priorities in river catchments. 2. Diversity indices were used to characterize fish diversity at the basin scale. An index of conservation status was applied for each species, which considers the occurrence, abundance and endemicity of each taxon. We used indirect ordination methods to test the relationship among basin features and to identify those variables most correlated with each other. To identify physical, biotic and environmental characteristics that seem to make a basin particularly susceptible to invasion, we performed a step‐wise multiple regression to examine the relationship between the number of native, translocated and introduced fish species (including the original native species richness of each basin), and landscape variables. 3. Over a period of approximately 50 years, the mean range size of native fish species has decreased by 60%. The greatest decline occurred in Gasterosteus gymnurus, Anguilla anguilla and Salaria fluviatilis, for which species over 75% of the original distribution area has been lost. The species with the highest conservation index were Gasterosteus gymnurus and Salaria fluviatilis. 4. Basin area and the catchment type explained 70% of variation in native species richness, whereas the number of dams and basin area accounted for more than 80% of variation in the number of introduced species. 5. The original native species richness and the number of introduced species at basin scale were not related, and thus there was no evidence of “biotic resistance” to invasion. The restoration of natural hydrologic processes and the development of specific management tools to protect native species, such as the prioritization of areas for fish conservation and the eradication of local populations of exotic species, are required to restore native fish fauna in these catchments.     

外来树种对本地林业虫害的诱发作用

白蜡窄吉丁、萧氏松茎象、光肩星天牛、黄斑星天牛、云斑天牛和桑天牛等林业害虫均为我国本地林业生态系统中的昆虫种类,在北美白蜡树、北美松树和北美黑杨派杨树等外来树种引入和大量栽培之前,一直没有形成严重的危害,以至于白蜡窄吉丁和萧氏松茎象都没有引起人们的关注。这些重要林业害虫在我国的发生都是伴随着敏感外来树种的引进和大量不合理的种植而逐渐严重起来的。本文对外来树种的引进与本地林业虫害的发生之间的关系进行了分析,提出了外来树种的不合理引进可能诱发本地林业新虫害的观点,并对其发生机理以及相应的研究和治理对策进行了讨论。     

Individual variability in life-history traits drives population size stability

Understanding how population sizes vary over time is a key aspect of ecological research.Unfortunately,our understanding of population dynamics has historically been based on an assumption that individuals are identical with homogenous life-history properties.This assumption is certainly false for most natural systems,raising the question of what role individual variation plays in the dynamics of populations.While there has been an increase of interest regarding the effects of within populatien variation on the dynamics of single populations,there has been little study of the effects of differences in within population variation on patterns observed across populations.We found that life-history differences (clutch size) among individuals explained the majority of the variation observed in the degree to which population sizes of eastern fence lizards Sceloporus undulatus fluctuated.This finding suggests that differences across populations cannot be understood without an examination of differences at the level of a system rather than at the level of the individual [Current Zoology 58 (2):358-362,2012].     

激流植物群落生态学研究

本文根据6年定位研究结果,讨论了北温带山溪激流植物群落生态学方面的问题.文中分析了激流群落的种类组成、数量特征、外貌、结构、分布格局、动态与功能等.根据种-面积曲线确定样地最小面积;分析群落自然高度与绝对高度的相关性;探讨了群落的垂直分层与水平镶嵌;划分了群落的生态种组和生态差型;建立了群落的物候型谱和生物量成层模型;阐述了群落的建成过程和演替类型;最后,按照水毛茛对于扰的适应机制分析了其繁殖策略;提出了内陆黑潮并分析了其对群落演替所发生的影响.     

Ecological aspects,explosive range extension and impact of a mass invader,Corophium curvispinum Sars, 1895 (Crustacea: Amphipoda), in the Lower Rhine (The Netherlands)

A few years after it invaded, the amphipod Corophium curvispinum Sars appeared to be the most numerous macroinvertebrate species in the River Rhine. From 1987 to 1991 the densities of this species on the stones of groins in the Lower Rhine at a depth of 0.5 m increased from 2 to 200000 specimens per m². In the Lower Rhine and its branches the densities of C. curvispinum increased with increasing current velocities and with increasing water depths. So far, a maximum population density of 750000 specimens per m² has been found in the Lower Rhine, which is many times the densities recorded elsewhere. Population parameters, densities and distribution of C. curvispinum were studied in the Lower Rhine and its branches, using artificial substrates and sampling stones from groins. The success of this immigrant is related to its competitive strategy, which shows several aspects of a r-strategy. In addition, the heavily eutrophicated Lower Rhine provides abundant food (phytoplankton, suspended organic matter) for this opportunistic filter-feeder. The increased salinity and water temperatures in the Lower Rhine resulting from industrial discharges have contributed to the current success of this southern species originating in brackish waters. The very high densities of C. curvispinum might have an enormous impact on the river ecosystem by changing food webs.     

Community‐level effects of co‐occurring native and exotic ecosystem engineers

1. Non‐indigenous ecosystem engineers can substantially affect native biodiversity by transforming the physical structure of habitats. In the Great Lakes–St. Lawrence River system, introduced dreissenid mussels (Dreissena polymorpha and D. bugensis) and the native benthic macroalga Cladophora act as ecosystem engineers by increasing substratum complexity and providing interstitial habitat for benthic macroinvertebrates. 2. We manipulated the topography and perimeter‐to‐area ratio of patches of dreissenid mussels in a series of colonisation experiments conducted at two sites in the St. Lawrence River. Experimental substrata were variably colonised by Cladophora, prompting us to examine (i) how the topography of Dreissena patches affects benthic macroinvertebrate diversity and (ii) the extent to which the effects of Dreissena are altered by the presence of another habitat‐modifying organism (Cladophora). 3. The results of our first experiment suggested that a patchy distribution of dreissenid mussels is an important driver of benthic diversity at small spatial scales. The results of our second and third experiments suggested that a native habitat engineer, Cladophora, modifies the impact of Dreissena on benthic macroinvertebrate communities. 4. While macroalgal blooms have been linked to the large‐scale impacts of Dreissena on light and nutrient availability, Dreissena shells inhibited Cladophora growth at our experimental scale. These findings demonstrate that the interactions between habitat‐modifying species can complicate efforts to predict the community‐level effects of an invasion.