不同互花米草治理措施对植物与大型底栖动物的影响简

治理外来入侵植物互花米草(Spartina alterniflora)对保护河口湿地鸟类栖息地及生物多样性具有重要意义。研究在崇明东滩比较了\"淹水刈割\"、\"反复刈割\"及\"化学除草\"三种措施对大面积互花米草的治理效果及其对大型底栖动物与土著植物芦苇(Phragmites australis)的影响。结果表明,反复刈割措施对互花米草生长具有一定的控制作用,对底栖动物群落的影响较小;使用化学除草剂清除互花米草的效果不明显,对底栖动物群落的影响亦不明显;淹水刈割措施能长期有效地清除互花米草,但长期淹水对底栖动物群落的影响较大,同时亦对芦苇生长造成一定负面影响。因此,淹水刈割可能是在河口生态系统治理大面积互花米草最有效的方法,但是在后续管理中需要采取一定的措施来减小对底栖动物及土著植物的影响。     

基于遥感与GIS的海口市景观格局动态演化

城市地区包括建成区和郊区的农村,随着城市快速发展城市地区景观结构将发生深刻变化,由于人类活动对景观要素的作用方式,作用程度不同,其空间格局的转变模式在不同阶段出现一定程度差异,破碎度和分离度能描述景观破碎程度和景观要素斑块之间距离的变化,从而分析景观要素空间结构变化,多样性指数能分析景观要素的复杂情况,孔隙度指数能分析景观的尺度效应,从而分析不同尺度下景观要素的变化情况,能更好地分析景观要素变化的空间结构规律,利用1986,1996和2000年三期TM遥感图像得到海口市景观变化情况,在此期间海口市景观结构变化表现为林地,水体,沙地,农田等自然景观向城市,农村居民点和独立工矿建设用地等人文景观的变化。通过比较1986－1996和1996－2000年两个阶段景观要素的空间变化规律可以看出,林地在1986－1996年期间,由于人工林的增加,孔隙度指数减小,1996－2000年,林地开发较多,斑块趋于分散,水体在1986－1996年大面积的水体为主,1996－2000年以小面积为主,农田在两个阶段变化明显,1986－1996年,农田被城市,工矿建设用地开发区占用,斑块趋于分散,1996－2000年由于城市开发受到控制,未开发农田被恢复,斑块趋于集中,城市反映出国家宏观调控政策的影响,1986年,城市开发较为零乱,斑块较小,1996年,斑块趋于集中,2000年有进一步扩张的趋势,农村居民点规模较小,分布一直趋于分散,是一种不集约的用地形式,因此,利用景观生态学的数量方法,能很好地反映城市化过程中人类活动及政策对景观要素的影响,从而研究城市化过程中城市及其外围区域景观结构的动态变化过程。     

闽江口芦苇沼泽湿地土壤产甲烷菌群落结构的垂直分布

应用PCR-RFLP技术及测序分析对闽江口芦苇湿地土壤产甲烷菌群落结构的垂直分布特征进行了研究。在构建的6个克隆文库中,每个克隆文库随机挑选100个克隆进行菌落PCR验证,共得到591个阳性克隆。PCR产物经限制性内切酶MspⅠ进行RFLP分析后得到37个不同的分类操作单元(OTUs)。对37个克隆子进行了序列测定,与GenBank数据库中的序列进行比对,最近相似性在91%—99%之间。RFLP分析和系统发育分析表明,闽江口芦苇湿地土壤中产甲烷菌群落包括3大类群:甲烷杆菌目(Methanobacteriales)、甲烷微菌目(Methanomirobiales)和甲烷八叠球菌目(Methanosarcinales)。不同土壤深度中产甲烷菌群落的分布呈现出不同的特征。土壤表层(0—10 cm)优势产甲烷菌类群为Methanoregula,约占76%;10—20 cm土层主要的产甲烷菌类群为Methanolinea和Methanoregula,分别约占23%和29%;20—30cm土层优势的产甲烷菌类群为Methanolinea,约占66%。Shannon指数(H’)和Simpson多样性指教(D)表明,10—20cm土层产甲烷菌多样性高于土壤表层(0—10 cm)和20—30 cm土层。37个测序OTUs中有26个OTUs属于不可培养的产甲烷菌序列,表明闽江口芦苇湿地土壤中存在大量不可培养的产甲烷菌。     

生境片段化对千岛湖地表甲虫物种多样性的影响

在千岛湖片段化景观中选取20个陆桥岛屿和8个大陆样点,从2012年7月到2014年4月,按季度(春、夏、秋季)6次采用巴氏陷阱法收集地表甲虫,分析其物种多度、组成、多样性和季节动态,以及不同岛屿上的地表甲虫的物种多样性与岛屿面积和隔离度等岛屿空间特征的关系.结果表明: 共收集记录到地表甲虫26科101种3370头.大陆和大岛地表甲虫的物种丰富度有显著差异,且小岛地表甲虫密度显著高于大陆;大陆地表甲虫的物种组成变化较大,而岛屿上分布的地表甲虫的物种组成则变化较小.地表甲虫的物种丰富度与岛屿面积呈显著正相关,密度与隔离度呈显著正相关.夏季岛屿上地表甲虫物种丰富度高于春秋两季,岛屿与大陆样地的Shannon指数、Simpson指数和Pielou均匀度指数均在夏季最高、秋季最低.     

Landscape genetic structure of coastal tailed frogs (Ascaphus truei) in protected vs. managed forests

Habitat loss and fragmentation are the leading causes of species’ declines and extinctions. A key component of studying population response to habitat alteration is to understand how fragmentation affects population connectivity in disturbed landscapes. We used landscape genetic analyses to determine how habitat fragmentation due to timber harvest affects genetic population connectivity of the coastal tailed frog (Ascaphus truei), a forest-dwelling, stream-breeding amphibian. We compared rates of gene flow across old-growth (Olympic National Park) and logged landscapes (Olympic National Forest) and used spatial autoregression to estimate the effect of landscape variables on genetic structure. We detected higher overall genetic connectivity across the managed forest, although this was likely a historical signature of continuous forest before timber harvest began. Gene flow also occurred terrestrially, as connectivity was high across unconnected river basins. Autoregressive models demonstrated that closed forest and low solar radiation were correlated with increased gene flow. In addition, there was evidence for a temporal lag in the correlation of decreased gene flow with harvest, suggesting that the full genetic impact may not appear for several generations. Furthermore, we detected genetic evidence of population bottlenecks across the Olympic National Forest, including at sites that were within old-growth forest but surrounded by harvested patches. Collectively, this research suggests that absence of forest (whether due to natural or anthropogenic changes) is a key restrictor of genetic connectivity and that intact forested patches in the surrounding environment are necessary for continued gene flow and population connectivity.     

Impact of urban fragmentation on the genetic structure of the eastern red-backed salamander

Urban development is a major cause of habitat loss and fragmentation. Few studies, however, have dealt with fragmentation in an urban landscape. In this paper, we examine the genetic structure of isolated populations of the eastern red-backed salamander (Plethodon cinereus) in a metropolitan area. We sampled four populations located on a mountain in the heart of Montréal (Québec, Canada), which presents a mosaic of forested patches isolated by roads, graveyards and buildings. We assessed the genetic structure of these populations using microsatellite loci and compared it to the genetic structure of four populations located in a continuous habitat in southern Québec. Our results indicate that allelic richness and heterozygosity are lower in the urban populations. Exact differentiation tests and pairwise F _ST also show that the populations found in the fragmented habitat are genetically differentiated, whereas populations located in the continuous habitat are genetically homogeneous. These results raise conservation concerns for these populations as well as for rare or threatened species inhabiting urban landscapes.     

Divergent selection along climatic gradients in a rare central European endemic species,Saxifraga sponhemica

Background and Aims The effects of habitat fragmentation on quantitative genetic variation in plant populations are still poorly known. Saxifraga sponhemica is a rare endemic of Central Europe with a disjunct distribution, and a stable and specialized habitat of treeless screes and cliffs. This study therefore used S. sponhemica as a model species to compare quantitative and molecular variation in order to explore (1) the relative importance of drift and selection in shaping the distribution of quantitative genetic variation along climatic gradients; (2) the relationship between plant fitness, quantitative genetic variation, molecular genetic variation and population size; and (3) the relationship between the differentiation of a trait among populations and its evolvability.Methods Genetic variation within and among 22 populations from the whole distribution area of S. sponhemica was studied using RAPD (random amplified polymorphic DNA) markers, and climatic variables were obtained for each site. Seeds were collected from each population and germinated, and seedlings were transplanted into a common garden for determination of variation in plant traits.Key Results In contrast to previous results from rare plant species, strong evidence was found for divergent selection. Most population trait means of S. sponhemica were significantly related to climate gradients, indicating adaptation. Quantitative genetic differentiation increased with geographical distance, even when neutral molecular divergence was controlled for, and Q_ST exceeded F_ST for some traits. The evolvability of traits was negatively correlated with the degree of differentiation among populations (Q_ST), i.e. traits under strong selection showed little genetic variation within populations. The evolutionary potential of a population was not related to its size, the performance of the population or its neutral genetic diversity. However, performance in the common garden was lower for plants from populations with reduced molecular genetic variation, suggesting inbreeding depression due to genetic erosion.Conclusions The findings suggest that studies of molecular and quantitative genetic variation may provide complementary insights important for the conservation of rare species. The strong differentiation of quantitative traits among populations shows that selection can be an important force for structuring variation in evolutionarily important traits even for rare endemic species restricted to very specific habitats.     

Clustering Timber Harvests and the Effect of Dynamic Forest Management Policy on Forest Fragmentation

To integrate multiple uses (mature forest and commodity production) better on forested lands, timber management strategies that cluster harvests have been proposed. One such approach clusters harvest activity in space and time, and rotates timber production zones across the landscape with a long temporal period (dynamic zoning). Dynamic zoning has been shown to increase timber production and reduce forest fragmentation by segregating uses in time without reducing the spatial extent of timber production. It is reasonable to wonder what the effect of periodic interruptions in the implementation of such as strategy might be, as would be expected in a dynamic political environment. To answer these questions, I used a timber harvest simulation model (HARVEST) to simulate a dynamic zoning harvest strategy that was periodically interrupted by changes in the spatial dispersion of harvests, by changes in timber production levels, or both. The temporal scale (period) of these interruptions had impacts related to the rate at which the forest achieved canopy closure after harvest. Spatial dynamics in harvest policies had a greater effect on the amount of forest interior and edge than did dynamics in harvest intensity. The periodically clustered scenarios always produced greater amounts of forest interior and less forest edge than did their never clustered counterparts. The results suggest that clustering of harvests produces less forest fragmentation than dispersed cutting alternatives, even in the face of a dynamic policy future. Although periodic episodes of dispersed cutting increased fragmentation, average and maximum fragmentation measures were less than if clustered harvest strategies were never implemented. Clustering may also be useful to mitigate the fragmentation effects of socially mandated increases in timber harvest levels. Implementation of spatial clustering during periods of high timber harvest rates reduced the variation in forest interior and edge through time, providing a more stable supply of forest interior habitat across the landscape. Received 19 September 1997; accepted 6 August 1998.