Effects of single-tree and group selection harvesting on the diversity and abundance of spring forest herbs in deciduous forests in southwestern Ontario

Selection harvesting, by mimicking natural disturbance regimes of eastern deciduous hardwood forests, has been applied as a sustainable management practice that combines wood production with biodiversity conservation. However, the effects of this technique on understory herbs are unclear, particularly for spring ephemerals which have been suggested as sensitive to disturbance. Here, we experimentally assess the immediate effects of single-tree and group selection harvesting on spring ephemeral richness, diversity and abundance in deciduous forests of southwestern Ontario, Canada. Spring herbs were quantified in 4 m² plots before and one growing season after harvesting and compared to similar uncut, reference stands. The percent of species lost was significantly higher in reference than harvested plots. Mean species richness significantly increased after harvesting, predominately due to an increase in spring–summer species. Increases in the diversity of early spring flowering species were significantly greater in the group selection plots than reference plots. At the community level, no species appeared to be vulnerable to harvesting, and ordination analysis indicated that post-harvest communities were primarily determined by pre-harvest community composition. Furthermore, no species declined in abundance in response to harvesting, and overall percent cover increased proportionately more in single-tree selection plots than in group selection or reference plots. While harvesting appears to have negligible effects on spring ephemerals immediately following harvest, we recommend additional studies over longer time frames to assess possible successional effects and to discriminate treatment induced changes from naturally high yearly variation in species composition.     

有效微生物菌群(EM)对蟹鲈混养模式下养殖水体菌群结构的影响

为探究定期添加有效微生物菌群(EM)对蟹鲈混养养殖水质和菌群结构的影响,实验对混养水体进行了Ⅰ期(4月10号)、Ⅱ期(4月20号)、Ⅲ期(4月30号)和Ⅳ期(5月10号)的监测,并通过水质理化指标、16S rRNA基因高通量测序技术分析了每个时期的水质和菌群结构.高通量测序结果显示,实验期间水体主要优势菌门为变形菌门、...     

The impacts of Phalaris arundinacea (reed canarygrass) invasion on wetland plant richness in the Oregon Coast Range, USA depend on beavers

Invasive plants can threaten diversity and ecosystem function. We examined the relationship between the invasive Phalaris arundinacea (reed canarygrass) and species richness in beaver wetlands in Oregon, USA. Four basins (drainages) were chosen and three sites each of beaver impoundments, unimpounded areas and areas upstream of debris jams were randomly chosen in each basin for further study (n = 36). Analysis of covariance (ANCOVA) showed that the relationship between Phalaris and species richness differed significantly (p = 0.01) by site type. Dam sites (beaver impoundments) exhibited a strong inverse relationship between Phalaris and species richness (b_D = −0.15), with one species lost for each 7% increase in Phalaris cover. In contrast, there was essentially no relationship between Phalaris cover and species richness in jam sites (debris jam impoundments formed by flooding; b_J = +0.01) and unimpounded sites (b_U = −0.03). The cycle of beaver impoundment and abandonment both disrupts the native community and provides an ideal environment for Phalaris, which once established tends to exclude development of herbaceous communities and limits species richness. Because beaver wetlands are a dominant wetland type in the Coast Range, Phalaris invasion presents a real threat to landscape heterogeneity and ecosystem function in the region.     

Arbuscular mycorrhizal fungal communities in changing environments: The effects of seasonality and anthropogenic disturbance in a seasonal dry forest

The landscape of Mexican seasonal dry forests is affected by various periodic (long and drastic drought) and random (elimination of the forest coverage for agricultural purposes) disturbance events. The community of arbuscular mycorrhizal fungi (AMF) responds to these changes, sporulating and reducing its activity during the dry season, and slowly reestablishing itself following abandonment of cultivated fields. To determine the dynamics of the AMF community in response to natural phenomena and anthropogenic disturbances, we collected soil samples during the wet and dry seasons from plots with different time periods since abandonment of agricultural activity, categorized as early (less than 5 years), middle (11–23 years), and late (over 30 years) age plots. From each plot, AMF spores were isolated and identified in order to estimate abundance, richness and diversity. In addition, the number of infective propagules and value of mycorrhizal inoculum potential were calculated for each plot. Twenty-three species were recorded, for which Glomeraceae and Acaulosporaceae were the most commonly represented families. Significant differences were found in AMF species richness among plots and seasons and the diversity index of AMF was higher than 1.0 in most cases. There were no significant differences in spore abundance. Viable propagules were observed in all soil samples, with fluctuations relating mainly to time since abandonment. Overall, seasonality has a strong influence on AMF diversity but not on AMF infectivity, while time since abandonment had a more important impact.     

青海大通北川河源区自然保护区主要植物群落的物种多样性特征研究

本文通过样地和样方的方法进行群落学调查,调查了北川河源区自然保护区19个典型样地,计算分析北川河源区自然保护区主要植物群落的物种丰富度、物种多样性指数、物种多样性指数和物种均匀度指数在群落梯度上的分布特征,揭示了为本地区植物群落物种多样性的变化规律,为植被及其恢复更新评价提供资料和理论依据。     

安徽岭南森林群落物种多样性的研究

在安徽岭南自然保护区内4种群落类型中进行样地调查的基础上,采用物种丰富度指数、多样性指数、均匀度指数对保护区森林群落物种多样性进行了研究,发现自然恢复的群落中植物种类多,分布均匀,优势种不明显;人工更新的林分中植物多样性低,优势种明显;群落结构上,4种类型多样性的大小顺序是灌木>乔木>草本。     

Differential effect of arbuscular mycorrhizal fungal communities from ecosystems along management gradient on the growth of forest understorey plant species

Arbuscular mycorrhizal fungi (AMF) are important functional components of ecosystems. Although there is accumulating knowledge about AMF diversity in different ecosystems, the effect of forest management on diversity and functional characteristics of AMF communities has not been addressed. Here, we used soil inoculum representing three different AM fungal communities (from a young forest stand, an old forest stand and an arable field) in a greenhouse experiment to investigate their effect on the growth of three plant species with contrasting local distributions - Geum rivale, Trifolium pratense and Hypericum maculatum. AM fungal communities in plant roots were analysed using the terminal restriction fragment length polymorphism (T-RFLP) method. The effect of natural AMF communities from the old and young forest on the growth of studied plant species was similar. However, the AMF community from the contrasting arable ecosystems increased H. maculatum root and shoot biomass compared with forest inocula and T. pratense root biomass compared to sterile control. According to ordination analysis AMF inocula from old and young forest resulted in similar root AMF communities whilst plants grown with AM fungi from arable field hosted a different AMF community from those grown with old forest inocula. AMF richness in plant roots was not related to the origin of AMF inoculum. G. rivale hosted a significantly different AM fungal community to that of T. pratense and H. maculatum. We conclude that although the composition of AM fungal communities in intensively managed stands differed from that of old stands, the ecosystem can still offer the ‘symbiotic service’ necessary for the restoration of a characteristic old growth understorey plant community.     

Biological crusts as a model system for examining the biodiversity-ecosystem function relationship in soils

Despite that soils may be the greatest repository of biodiversity on Earth, and that most terrestrial ecosystem functions occur in the soil, research on the role of soil biodiversity in ecosystem function has lagged behind corresponding research on aboveground organisms. Soil organisms pose special problems to biodiversity-function research, including the fact that we usually do not know their identity nor what they do in soil ecosystems, cannot easily estimate their biodiversity, and cannot culture the majority of the organisms for use in manipulative experiments. We propose here that biological soil crusts (BSCs) of deserts and many other ecosystems may serve as a useful model system for diversity-function research because the species concept is relatively well-defined within BSC organisms, their functional attributes are relatively well-known, and estimation and manipulation of biodiversity in experiments are feasible, at least within some groups of BSC biota. In spite of these features, there is a pronounced lack of research on biodiversity-function using these organisms. At least two complementary approaches are possible: experiments using artificially-constructed BSCs, and observational studies which statistically control for the effects of other factors which are likely to covary with biodiversity. We applied the latter to four observational datasets collected at multiple spatial scales in Spain and the United States using structural equation models or path analysis using ecosystem function indicators relating to hydrology, trapping and retention of soil resources, and nutrient cycling. We found that, even when total BSC abundance and key environmental gradients are controlled for, direct and approximately linear relationships between species richness and/or evenness and indicators of ecosystem functioning were common. Such relationships appear to vary independently of region or spatial scale, but their strength seems to differ in every dataset. Functional group richness did not seem to adequately capture biodiversity-function relationships, suggesting that bryophyte and lichen components of BSC may exhibit low redundancy. More research employing the multi-trophic, multi-functional, and manipulable BSC system may enable more rapid understanding of the consequences of biodiversity loss in soils, and help enable a biodiversity-function theory that is pertinent to the numerous ecosystem services provided by soil organisms.     

5种典型荒漠植物群落的物种多样性研究

[目的]探究5种典型荒漠植物群落的物种多样性,为荒漠植物资源的保护和利用提供依据。[方法]通过调查古尔班通古特沙漠的5种典型群落,利用多样性指数、优势度指数、丰富度指数和均匀度指数研究荒漠植物的物种多样性。[结果]5个群落的丰富度指数(Ma)从大到小依次为白梭梭、白刺、柽柳、沙拐枣、梭梭;优势度指数(C)从大到小依次为沙拐枣、梭梭、白刺、柽柳、白梭梭;群落多样性指数(D)从大到小依次为白梭梭、柽柳、白刺、梭梭、沙拐枣;均匀度指数(Jsw)从大到小依次为梭梭、沙拐枣、柽柳、白刺、白梭梭。[结论]同时提高荒漠植物的丰富度和均匀度,可以提高荒漠生态系统的生物多样性。     

高原作物青稞根及根际内生细菌群落结构的高通量分析

利用高通量测序技术分析了西藏青稞主栽品种藏青2000根及根际内生细菌的16S V4变异区序列,同时应用UparseRON、KA等软件整理和统计样品序列数和操作分类单元（OTU）数,分析物种丰度及Alpaha多样性等指标。获得的用于分析青稞根部内生细菌的有效序列和OTUs为55 192/3 613,用于分析青稞根际土壤内生细菌的有效序列和OTUs为62 181/4 399;根部及根际土壤Chao1指数分别为3 443.4290和4 632.5820,shannon多样性指数分别为8.542和9.967。在门水平对代表性OTU进行注释发现,青稞根及根际土壤内生细菌主要是变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）、放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、厚壁菌门（Firmicutes）。在属水平上主要是假单胞菌属（Pseudomonas）、链霉菌属（Streptomyces）、土地杆菌属（Pedobacter）、黄杆菌属（Flavobacterium）、红游动菌属（Rhodoplanes）。结果显示,青稞根及根际内生细菌具有丰富的多样性,且二者的优势菌属一致。