Effects of nourishment on the form and function of an estuarine beach

Beach nourishment programs in estuaries can enhance shore protection, but they decrease habitat suitability by creating higher berms and wider backshores than would occur under natural conditions. Use of sediment sources from outside the area can result in sedimentary characteristics that differ from native sediments on the surface and at depth, altering conditions for both aeolian transport to dunes and interstitial fauna. Field data were gathered on an estuarine beach to determine differences in beach profile change, depth of sediment reworking, and potential for aeolian transport due to nourishment. Data were gathered over a 20-month period 6 months prior to nourishment, 3 days after nourishment, 6 months after nourishment, and 14 months after nourishment when the beach was mechanically graded to eliminate a vertical scarp in the foreshore. The nourishment consisted of 87,900 m³ of sediment emplaced to create a 1.34-km-long, 30-m-wide berm 2.3 m above mean tide level. Seven percent of the fill was removed from the profile within 6 months after nourishment, accompanied by 7 m in horizontal retreat of the artificial berm. The fill on the backshore remained above the zone of wave influence over a winter storm season and was separated from the active foreshore by the scarp. Nourished sediments on the intertidal foreshore were significantly different from native sediments to a depth of 0.20 m below the surface. A lag surface of coarse sediment formed by deflation on the backshore, resulting in a rate of aeolian transport <2% of the rate on the wave-reworked foreshore.Nourishing a beach to a level higher than would be created by natural processes can create a profile that compartmentalizes and restricts transport of sediment and movement of fauna between the foreshore and backshore. Mechanical grading can eliminate the scarp, allow for faunal interaction, and reestablish wave reworking of the backshore that will facilitate aeolian transport. Using an initial design to nourish the backshore at a lower elevation and allowing a dune to provide protection against flooding during major storms could prevent a scarp from forming and eliminate the need for follow-up grading.     

放牧对滩涂底栖动物的影响

于2005年5月（春季）和10月（秋季）,调查了放牧对上海市崇明东滩大型底栖动物的影响.调查采样设置3个样区,其中Ⅰ、Ⅱ样区在放牧区,Ⅲ样区在非放牧区,3个样区均在潮间带的中潮带,共计90个样方.采集到底栖动物13种,其中节肢动物7种,软体动物4种,环节动物2种.Ⅰ、Ⅱ和Ⅲ样区春季分别有6、8和10种,秋季6、8和12种.各样区秋季底栖动物的平均密度均高于春季,春、秋季各样区的平均密度又均以Ⅲ样区最高.生物量与密度变化大体相似,以Ⅲ样区最高.与Ⅰ、Ⅱ样区相比,Ⅲ样区的多样性指数、均匀度和丰富度均最高,说明放牧改变了底栖动物种类分布的格局,使底栖动物的密度、生物量均有不同程度的改变,且放牧对崇明东滩底栖动物的生物多样性产生了一定的负面影响.     

乙草胺和甲胺磷对农田黑土可培养真菌数量及种群结构的影响

应用传统及PCR-DGGE方法(denaturing gradient gel electrophoresis),分别对不同浓度乙草胺、甲胺磷胁迫下黑土中可培养真菌CFU(colony forming units)、种群丰富度(richness)及种群结构动态变化规律进行了研究.结果表明,在实验室微域条件下,乙草胺对黑土可培养真菌CFU的影响随处理浓度的增加而抑制作用增强,表现出由低浓度(50 mg·kg^-1)时的刺激生长到高浓度(250 mg·kg^-1)时的长期抑制效应;250 mg·kg^-1甲胺磷在8周处理过程中对土壤可培养真菌生长具有显著的刺激效应,使可培养真菌CFU比对照增加10倍,但50和150 mg·kg^-1甲胺磷处理对土壤可培养真菌CFU无显著影响.种群丰富度系数分析结果表明,高、中浓度乙草胺处理可使土壤可培养真菌种群丰富度不可逆地降低.土壤真菌rDNA特异PCR-DGGE聚类分析结果表明,不同浓度乙草胺、甲胺磷处理均不同程度地对土壤可培养真菌的种群组成和结构造成影响,其中甲胺磷尤为显著.     

周边不同生境条件对茶园蜘蛛群落及叶蝉种群时空结构的影响

为利用天敌实施害虫生态控制,田间调查了周边不同生境条件对茶园蜘蛛及叶蝉种群结构的影响。结果表明:小乔木生境茶园(Ⅰ)和相思树生境茶园(Ⅲ)影响下茶园蜘蛛及叶蝉聚集程度较强,茶园Ⅰ叶蝉聚集数最多,为692头,但与其他生境茶园间差异不显著(P0.05);茶园Ⅲ蜘蛛聚集数量最多,为1155头,并与稻田生境茶园(Ⅱ)、生活区生境茶园(Ⅳ)的差异达到显著水平(P0.05);从蜘蛛功能群聚集情况来看,结网型蜘蛛相对较少,为295头;游猎型蜘蛛最多,为2957头;其中,茶园Ⅰ与茶园Ⅲ蜘蛛多样性指数和丰富度数值较大,对叶蝉的跟随效应明显,并与Ⅱ、Ⅳ茶园有显著差异(P0.05)。多元数据分析结果显示,茶园Ⅰ和茶园Ⅲ均能够明显提高蜘蛛群落聚集的时空分布水平;蜘蛛群落的聚集密度时空分布大小表现为:茶园Ⅰ茶园Ⅲ茶园Ⅳ茶园Ⅱ。由此可知周边生境结构植物丰富和相对稳定的茶园能通过和谐的生态过程影响蜘蛛和叶蝉的时空格局,提高蜘蛛对害虫叶蝉的自然控制能力。     

Effects of connectivity and recurrent local disturbances on community structure and population density in experimental metacommunities

Metacommunity theory poses that the occurrence and abundance of species is a product of local factors, including disturbance, and regional factors, like dispersal among patches. While metacommunity ideas have been broadly tested there is relatively little work on metacommunities subject to disturbance. We focused on how localized disturbance and dispersal interact to determine species composition in metacommunities. Experiments conducted in simple two-patch habitats containing eight protozoa and rotifer species tested how dispersal altered community composition in both communities that were disturbed and communities that connected to refuge communities not subject to disturbance. While disturbance lowered population densities, in disturbed patches connected to undisturbed patches this was ameliorated by immigration. Furthermore, species with high dispersal abilities or growth rates showed the fastest post-disturbance recovery in presence of immigration. Connectivity helped to counteract the negative effect of disturbances on local populations, allowing mass-effect-driven dispersal of individuals from undisturbed to disturbed patches. In undisturbed patches, however, local population sizes were not significantly reduced by emigration. The absence of a cost of dispersal for undisturbed source populations is consistent with a lack of complex demography in our system, such as age- or sex-specific emigration. Our approach provides an improved way to separate components of population growth from organisms' movement in post-disturbance recovery of (meta)communities. Further studies are required in a variety of ecosystems to investigate the transient dynamics resulting from disturbance and dispersal.     

玉米秸秆还田对土壤线虫数量动态与群落结构的影响

通过大田玉米秸秆还田试验研究了其对农田土壤线虫数量动态、属的种类及群落结构等的影响。结果表明:2013—2014连续两年试验期间,蠡玉35玉米秸秆还田(CR)与不还田对照处理(CK)共鉴定到土壤线虫36个属(CR 36个属,CK 30个属);其中,植食性线虫12个属(CR 12属,CK 10属),食细菌线虫15个属(CR 15属,CK 14属),食真菌线虫5个属(CR 5属,CK4属),捕/杂食线虫4个属(CR 4属,CK 2属)。秸秆还田处理与不还田处理相比,植食线虫和食真菌线虫的相对丰度降低,而食细菌线虫和杂/捕食线虫的相对丰度提高,且食细菌线虫的相对丰度显著提高达42.95%。此外,秸秆还田处理土壤线虫总数高于不还田对照处理,但差异不显著;而秸秆还田处理可显著增加食细菌线虫数量,增幅高达16.3%—125.6%。与不还田处理对照相比,秸秆还田处理可显著提高土壤线虫群落多样性指数(H')、属类丰富度(S)和线虫通路指数(NCR),但对群落均匀度(J)、瓦斯乐斯卡指数(WI)和总成熟指数(∑MI)的影响不显著。可见,玉米秸秆还田具有重要的生态学意义,可在一定程度上增加土壤线虫数量和种类多样性,进而使土壤生态系统向稳定健康的方向发展。     

Habitat-dependent population regulation and community structure

Summary Density-dependence provides a causal link between processes acting at different levels of ecological organization. The linkage between density-dependent habitat use, population regulation and community organization is examined on the basis of qualitative and quantitative differences between habitats. These differences are expressed as characteristic shapes on isodars which are lines of equal fitness, and are plotted in density space as lines at every point of which the fitness of individuals in one habitat is equal to that of individuals in another. Isodars can be constructed for single species or modified to include the effects of interacting species. Isodars are easily analyzed by linear regression to differentiate between alternative modes of population regulation and to suggest patterns of community structure. Different isodars are causally related to different kinds of community structure, and suggest the existence of four new forms of community organization; equal, differential, switched and mixed preferences. A preliminary isodar analysis on a common rodent species demonstrates that population regulation depends upon habitat, and that mixed preferences probably organize the rodent community. Habitat-dependent population regulation has farreaching implications to studies of temporal and spatial scale, and to all ecological processes that are density-dependent.     

滨海沙滩珊瑚菜种群的空间格局及其对岸垄的响应

珊瑚菜(Glehnia littoralis)是国家Ⅱ级重点保护植物,天然分布在中国滨海沙滩潮上带。为认识珊瑚菜种群的更新机制及其对岸垄阻隔的响应,以青岛市胶南沙滩为例,调研沙垄前后珊瑚菜野生种群的分布和结构特征。结果表明:在分布格局上,垄前珊瑚菜在2.5 m的空间范围内呈聚集分布,成株与幼苗没有负关联性,而在更小尺度上表现明显的正关联性;垄后珊瑚菜表现出聚集范围变窄和聚集强度减弱的趋势,成株与幼苗的正关联性减弱,甚至有明显的负关联性;在种群结构上,垄前珊瑚菜的相对密度较高,幼苗较多,结实量较大,更新正常;相反,垄后珊瑚菜的密度、幼苗数量、结实量均降低或减少,更新过程明显受阻。据此推断,岸垄可能通过抑制潮水对种子的传播而阻碍珊瑚菜的天然更新。     

Dynamics of bacterial community exposed to hydrocarbons and oleophilic fertilizer in high-Arctic intertidal beach

Exposure of pristine microbial environments to hydrocarbon contamination stimulates growth of the initially small fraction of indigenous hydrocarbon-degrading bacteria. Custom-made oleophilic fertilizers have been demonstrated to promote oil bioremediation by boosting this proliferation. In the present study, the temporal dynamics of the bacterial community structure and the individual influences of hydrocarbons and an oleophilic fertilizer in shaping the community structure was explored during a 78 days bioremediation experiment in a high-Arctic intertidal beach environment. A combination of cultivation-independent 16S rRNA gene length-heterogeneity polymerase chain reaction (LH-PCR) profiling and identification of hydrocarbon-degrading isolates based on partial 16S rRNA gene sequences was employed. LH-PCR community profiles in the fertilizer alone and fertilized kerosene plots were largely indistinguishable throughout the experimental period, while kerosene alone plots showed a markedly different composition of dominant groups. This pointed to the fertilizer as the more decisive factor in shaping the community structure. Most prominent LH-PCR fragments which emerged after kerosene or fertilizer addition could be provisionally assigned to bacterial taxa through coinciding LH-PCR fragment lengths with hydrocarbon-degrading isolates obtained from the same type of experimental units. However, a few quantitatively significant LH-PCR groups had no counterparts among the cultivated bacteria. One of these was affiliated to a hitherto unspeciated subgroup within the Alkanindiges/Acinetobacter clade of Moraxellaceae by a 16S rRNA gene cloning approach.     

Colonization and divergence: phylogeography and population genetics of the Atlantic coast beach mice

Barrier island taxa provide an opportunity to investigate recent evolutionary processes, such as colonization and isolation of recently diverged taxa, and provide important insights into understanding contemporary diversity and the assessment of conservation units. Using rapidly evolving genetic markers (mitochondrial DNA and microsatellites), we studied the Atlantic coast beach mouse subspecies (Peromyscus polionotus decoloratus, P. p. niveiventris, and P. p. phasma). Our data indicate that each of the extant coastal subspecies (P. p. niveiventris and P. p. phasma) is comprised of unique haplotypes indicative of their isolation, while the extinct subspecies, P. p. decoloratus, contain a single haplotype, which was shared with P. p. phasma. Moreover, all the coastal haplotypes originate from a single mainland haplotype found in central Florida, USA. The microsatellite data indicated high levels of genetic structure among our sampled populations. Additionally, these data group the populations into three distinct genetic clusters, with each of the extant coastal subspecies belonging to their own cluster and the mainland individuals forming a separate cluster. The extant Atlantic coast beach mice are on separate evolutionary trajectories, thus representative of separate taxonomic units. Therefore, the data support that two extant subspecies on the Florida Atlantic coast fit the Distinct Population Segment designation and should be managed and conserved as two separate independent units.     

植物间正相互作用对种群动态和群落结构的影响:基于个体模型的研究进展

植物间的相互作用对种群动态和群落结构有着重要的影响。大量的野外实验已经揭示了正相互作用(互利)在群落中的普遍存在及其重要性。为了弥补野外实验方法的不足, 模型方法被越来越多地应用于正相互作用及其生态学效应的研究中。该文基于个体模型研究, 探讨了植物间正相互作用对种群动态和群落结构的影响。介绍了植物间正相互作用的定义和发生机制、植物间相互作用与环境梯度的关系。正相互作用是指发生在相邻的植物个体之间, 至少对其中一个个体有益的相互作用。植物通过直接(生境改善或资源富集)或间接(协同防御等)作用使局部环境有利于邻体而发生正相互作用。胁迫梯度假说认为互利的强度或重要性随着环境胁迫度的增加而增加, 但是越来越多的经验研究认为胁迫梯度假说需要改进。以网格模型和影响域模型为例, 介绍了基于个体的植物间相互作用模型方法。基于个体模型, 对近年来国内外正相互作用对种群时间动态(如生物量-密度关系)、空间分布格局和群落结构(如群落生物量-物种丰富度关系)影响的研究进行了总结。指出未来的研究应集中在对正相互作用概念和机制的理解, 新的模型, 新的种群、群落, 甚至生态系统问题, 以及在全球变化背景下进行相关的研究。     

杭州湾滩涂湿地植被群落演替与物种多样性动态

以杭州湾不同年份形成的滩涂湿地植被群落为研究对象,采用样线法结合样方法进行调查取样,并通过除趋势对应分析排序研究了群落演替的动态和方向,同时采用Pielou均匀度指数、Margalef丰富度指数、Shannon-Wiener多样性指数和Simpson多样性指数分析了物种多样性在群落演替过程中的动态变化.结果表明:该区域植被群落演替序列为海三棱藨草群落→芦苇群落→柽柳 芦苇群落→旱柳 白茅群落;随着演替的进行,群落物种丰富度显著增加,均匀度逐渐降低,物种多样性呈先增加后降低的趋势.     

Spatio-temporal structure of the suprabenthic community from Creixell beach (western Mediterranean)

A survey of the Creixell beach suprabenthos community was carried out from January 1991 to January 1992. The structural evolution of the suprabenthic community reflects the severe and fluctuating environmental conditions of this beach: dominance of a reduced number of peracarid species, low species richness and diversity indices and strong fluctuations of density values. The strong wave action in the surf zone is the main environmental factor of the beach. In relation to such action, the suprabenthic community has the typical features of an exposed and dissipative beach community: abundance of resident and endemic swimmer mysids, distinct bathymetric zonation patterns of populations and migrations related to storm/calm cycles.     

Effects of sandy beach cusps on wrack accumulation,sediment characteristics and macrofaunal assemblages

Beach‐cast marine macroalgae and seagrasses, collectively termed wrack, provide shelter and habitat for beach fauna and can often provide a large input of energy and nutrients to sandy beaches. Wrack deposition on sandy beaches varies spatially and could be affected by morphological features on the beach face such as cusps. This study tested a series of hypotheses regarding the differences in wrack deposits, sediments and macrofaunal assemblages between cusp bays and horns on two beaches in South Australia. Bays had greater cover and larger pieces of wrack than horns. Sediment organic matter content was greater on horns than in bays but mean particle size did not differ consistently between bays and horns. Macrofaunal diversity was higher in bays and this pattern was probably driven by differences in the cover of wrack between bays and horns. Cusp morphology thus influences the distribution of wrack on the beach face, which in turn influences the distribution of macrofauna. Studies of sandy beaches with cusps should therefore be explicitly designed to sample cusp features and associated wrack deposits.     

Effects of low temperature on the burrowing rates of four sandy beach molluscs

Burrowing rates have been measured as a function of size and temperature in four molluscs from warm temperate South African sandy beaches: two bivalves of the genus Donax and two whelks of the genus Bullia. Animals were acclimated to a summer temperature of 21 °C and then subjected to drastic temperature drops, aimed at simulating coastal temperatures recorded during local upwelling. Burrowing times increased from 6–16 s at 20 °C to 18-∞ s at 10 °C, the lowest temperature recorded during summer upwelling. The degree of retardation of burrowing that occurred at low temperature was inversely proportional to the height of penetration into the intertidal zone by the different species. Large animals burrowed more slowly than small animals but were less affected by lowered temperature. Comparison of burrowing rates at 10 °C against swash frequencies recorded under upwelling conditions suggests that under extreme conditions of upwelling, burrowing in three species may not be rapid enough to prevent some individuals being swept up the beach by the swash. The most dangerous time in this respect is at the high tide during choppy sea conditions.