Effects of landscape patterns on species density and abundance of trees in a tropical subdeciduous forest of the Yucatan Peninsula

Most studies of the effects of fragmentation and landscape patterns on plant communities focus on particular patches and on local species richness (α-diversity), while few studies examine different patch-types at the whole landscape level and address effects on abundance and composition of species or functional groups. The present study aims to identify and characterize relationships between patch-type metrics and species density and abundance of trees using four tropical subdeciduous forest landscapes in the Yucatan Peninsula considering the entire landscape as the unit of study. Species density and abundance of different groups of tree species resulting from hierarchical clustering were related to landscape patterns of patch-types (area, edge, shape, similarity and contrast) using regression analysis and Akaike Information Criterion (AIC). The abundance of tree species in the oldest stages of succession was associated with percentage of land of a patch-type. Total area may favor the establishment of shade-tolerant tree species in the study area because as the area of forest patches increases, the area of forest interior conditions also increases. Conversely, the abundance of species at early and intermediate stages was related to total edge contrast and edge density, respectively. Fragmentation increases the proportion of edge zones of a patch-type, creating contrasting microclimate conditions that could promote the establishment of pioneer and light-demanding species. Thus, the combined effect of total area and edge length of a patch-type may enhance total tree species richness in the study area by favoring species with different life-history strategies. The appearance of area, shape, edge and contrast in most of the regression models suggests that some generalization can be made about the effects of spatial geometry of patch-types on species composition and abundance of tropical trees. Understanding associations between landscape metrics and species density and abundance of objectively derived groups or guilds of species can provide important insights on the effects of fragmentation and landscape pattern on these guilds and on overall α-diversity, as well as guidelines for their conservation and management.     

Forecasting vole population outbreaks in forest plantations: The rise and fall of a major mammalian pest

Voles of the genera Microtus and Myodes feed on tree seedlings planted on cutover forest land in temperate and boreal forests of North America and Eurasia. This damage may have serious economic implications as well as limit regeneration of appropriate tree species in certain forest ecosystems. Prediction of vole population outbreaks and feeding damage to forest plantations, across even a limited geographic range, has yet to be achieved in North America. Thus, a major objective was a detailed analysis of changes in population dynamics of long-tailed voles (Microtus longicaudus), and to test three hypotheses (H) that vole populations would: (H₁) rise and fall in accordance with the abundance of herbaceous plants (grasses and forbs) during early vegetative succession after forest harvesting, (H₂) be positively associated with grass-seeded sites; and (H₃) incidence of feeding damage to seedlings would be positively associated with vole abundance. Voles were live-trapped for 6 years (2004–2009) from the time of harvesting on intensive sites, as well as surveyed over a range of extensive sites. Population numbers were related to habitat characteristics and tree damage in young forest plantations near Golden, British Columbia, Canada.     

Modelling exploration of the future of European beech (Fagussylvatica L.) under climate change—Range,abundance, genetic diversity and adaptive response

We explored impacts of climate change on the geographic distribution of European beech by applying state of the art statistical and process-based models, and assessed possible climate change impacts on both adaptive capacity in the centre of its distribution and adaptive responses of functional traits at the leading and trailing edge of the current distribution. The species area models agree that beech has the potential to expand its northern edge and loose habitat at the southern edge of its distribution in a future climate. The change in local population size in the centre of the distribution of beech has a small effect on the genetic diversity of beech, which is projected to maintain its current population size or to increase in population size. Thus, an adaptive response of functional traits of small populations at the leading and trailing edges of the distribution is possible based on genetic diversity available in the local population, even within a period of 2–3 generations.     

褐家鼠体表蚤类流行分布预测（摘要）

[目的]预测褐家鼠体表蚤的感染率。[方法]在云南省的23个县（市）进行现场抽样,采集褐家鼠体表蚤,运用包涵平均感染度及方差的流行性模型。[结果]蚤感染率与感染度的对数值成线性相关,蚤感染率的预测值与实际值成线性相关。[结论]褐家鼠体表蚤的平均感染度可以预测其感染率。     

合肥地区草履虫丰度与水质关系的研究

[目的]研究合肥地区部分湖泊中草履虫丰度与水质的关系。[方法]对4个采样点的草履虫丰度和水质综合评价指数进行了相关分析和回归分析。[结果]草履虫丰度和水质综合评价指数之间呈正相关,即草履虫丰度越小,水质越好。[结论]草履虫丰度可以反映水质情况。     

氮肥对稻田土壤反硝化细菌群落结构和丰度的影响

以氮肥田间定位试验为研究对象,利用PCR-DGGE(聚合酶链反应变性梯度凝胶电泳)和荧光定量PCR(real-time PCR)技术,通过对反硝化细菌nirS基因的检测,分析了定位试验第2年稻田反硝化细菌群落结构和丰度的变化。DGGE图谱及依据其条带位置和亮度数字化数值进行的主成分分析(PCA)结果均显示:在氮肥定位试验第2年,与不施肥对照(CK)比较,在水稻各个生育期(分蘖期、齐穗期和成熟期)内,施用氮肥[150kg(N)·hm-2]的稻田根层土或表土中的反硝化细菌群落结构均无明显变化;且稻田根层土或表土中的反硝化细菌群落结构在水稻各个生育期间也均无明显差异。荧光定量PCR结果显示,在水稻生长发育过程中,施用氮肥的稻田根层土或表土中的反硝化细菌nirS基因拷贝数始终显著(P<0.05)高于其对应的不施肥对照。此外,无论施用氮肥与否,根层土中的反硝化细菌nirS基因拷贝数在水稻成熟期时都会显著(P<0.05)降低;但表土中的nirS基因拷贝数在水稻各生育期间无明显变化;且水稻成熟期时施用氮肥和不施肥的稻田表土中nirS基因拷贝数都显著(P<0.05)高于根层土。同时,与对照比较施用氮肥可促进水稻增产44%。研究表明,短期定位试验中施用氮肥能够显著提高稻田土壤反硝化细菌的丰度,但对其群落结构没有明显影响。     

Termites promote soil carbon and nitrogen depletion: Results from an in situ macrofauna exclusion experiment,Peru

We present results from one of the first in situ soil termite exclusion experiments using translocated soil that was not colonised by termites prior to the experiment. Macrofauna were excluded or included using fine (0.3 mm) and coarse (5 mm) mesh, respectively. We found that termites were the most dominant macrofauna in the macrofauna-included samples throughout the sampling period. Additionally, C and N depletion rates were consistently higher in samples with macrofauna than without macrofauna despite the seasonal decline of termites at the start of the wet season. This suggests that the presence of termites in soil promotes C and N depletion that may be linked to the passage of soil through the termite gut and the affect termites have on bioturbation and nutrient distribution.     

商洛学院绿化植物调查研究

依据商洛学院绿化植物的实地调查,统计分析了校园植物科属种数目,分析了其乔木、灌木、藤本以及草本植物的科属种及其百分比。通过裸子植物和被子植物的使用比例,分析了商洛学院绿化植物的丰富度,并概述了学院绿化特色,指出了在绿化中存在的问题和相应的改进建议。     

Analysis of SSR in Citrus Sequences from EMBL Database

Abundance of simple sequence repeat (SSR) in Citrus sequences from EMBL database was investigated by using computer program MISA (MIcroSAtellite), which aimed to provide useful information for the development of SSR markers.Among 32 896 sequences of Citrus, 4987 SSRs were found in 4167 sequences and the average distance between SSRs was approximately 3.5 kb. Mononucleotide repeats (50.6%) were the most abundant repeats. And di-, tri-, tetra-, penta- and hexa-nucleotide repeats were 22.8, 25.2, 1, 0.08, and 0.36%, respectively. The most abundant motif was A/T followed in descending order by AG/CT, AC/GT, AT/TA. AAT/ATT, AAG/CTT, AGC/CGT, ACG/CTG and C/G. They comprised about90% of all microsatellites. Ten primer pairs were designed, and three of them produced clear visible bands among Citrus and its related genera.     

福建浮宫红树林区的硅藻组成研究

[目的]初步分析了福建九龙江浮宫红树林区的硅藻组成。[方法]此次研究分析鉴定了浮宫红树林区6个表层样和1个柱状样的硅藻属种组成。[结果]①浮宫红树林沉积硅藻植物群属种多样性强,共鉴定出硅藻34属103种(含不定种),大部分为中心纲的圆筛属;②红树林区底泥中硅藻数量丰富。[结论]沉积硅藻种群以浮游的海水种和咸水半咸水种为主,说明浮宫红树林处于以海水作用为主的沉积环境中。