Epizootiology of Amblyospora connecticus (Microsporida) in Field Populations of the Saltmarsh Mosquito, Aedes cantator, and the Cyclopoid Copepod, Acanthocyclops vernalis

The natural ecology of a heterosporous microsporidium, Amblyospora connecticus was investigated at three different salt marsh habitats during 1986–1989. The parasite has a well-defined seasonal transmission cycle that occurs regularly each year and intimately involves the primary mosquito host, Aedes cantator, and the intermediate copepod host, Acanthocyclops vernalis. In the spring, the microsporidium is horizontally transmitted from the copepod, where it appears to overwinter, to the mosquito via the ingestion of haploid spores produced in the copepod. Mosquitoes develop a benign infection, and females transmit the microsporidium transovarially to their progeny via infected eggs. Oviposition occurs during the summer and infected eggs hatch synchronously in the fall causing widespread epizootics. Infected larvae die, and the cycle is completed when meiospores are released into the pool and subsequently are eaten by A. vernalis, which reappears in the fall and early winter. Amblyospora connecticus thereby persists by surviving in one of two living hosts throughout most of its life cycle rather than in the extra-corporeal environment. This represents an important survival strategy for A. connecticus as results show the salt marsh habitat to be a relatively unstable environment that is subject to periodic flooding and drying. The adaptive significance of utilizing an intermediate host in the life cycle is discussed as it directly facilitates transmission and enhances survival of the microsporidium.     

Vegetation development in abandoned gravel pits: effects of surrounding vegetation,substrate and regionality

Abstract. Vegetation development in 68 abandoned gravel pits and their surroundings in five regions in Sweden is described by means of classification and ordination. Most pits were less than 10 yr old, but some pits in central Sweden were up to 100 yr old. For 26 pits in central Sweden the results of mechanical and chemical soil analyses are presented. Vegetation in young pits is more homogeneous than the vegetation in the surroundings. The surrounding vegetation type strongly affects pit vegetation. There are regional differences in pit vegetation between pits in coniferous forests in different parts of Sweden. Old gravel pits are clearly distinguished from young ones and show more resemblance to the surrounding vegetation. Tree layer cover and nitrogen content increase, whereas C/N ratio and pH decrease with age. Species richness of the gravel pits was not related to their size.     

Riverain vegetation in the Nile valley in Upper Egypt

Abstract. Naturaland semi-natural plant communities occurring in the Nile Valley in Upper Egypt are described and their position in the zonation along the river bank interpreted. With the help of ordination and classification methods relationships among the 13 community types and their distribution along the predominating moisture gradient are elucidated. The vegetation of the Nile Valley can be described as a series of discrete plant community types on the basis of their floristic composition, structural components and habitat conditions. The communities can be grouped into four higher units, considered as formations: swamp, meadow, thorn-bush and riverain woodland.     

Pharmaceuticals from cultured algae

Summary An algae screening program, including cultured macroalgae, cultured cyanobacteria and cultured eukaryotic microalgae has been undertaken. Methods for the isolation, purification, preservation and cultivation of axenic cyanobacteria and eukaryotic cultures have been developed. Screening of these groups for biologically active components has lead to the isolation of pachydictyol and caulerpenyne from cultured macroalgae, while a series of hapalindoles and an antifungal depsipeptide have been isolated from cyanobacteria.     

Unified classification of European natural forests: the approach of the vegetation map of Europe

With the aim of evaluating the accessible data on vegetation structure and composition for the Vegetation Map of Europe as far as possible, a reasonable classification of natural vegetation has been proposed which facilitates the identification of vegetation units used in different Schools of vegetation science. The proposed universal classification makes full use of several different principles. The highest units are based on physiognomic-ecological features and correspond to formation units of different rank. The European natural forest vegetation (including shrubs) has been divided into 10 formation units. Each formation is further divided into subunits according to the most important features. Ecological and functional interpretation has priority in the hierarchic structure of the system which was used in the legend to the Vegetation Map of Europe. The resulting system shows the most important features of latitudinal (vegetation zones and subzones), longitudinal (oceanic to continental analogues) and altitudinal (vegetation belts) regularities, further azonal vegetation types and their differentiation as well as the edaphic, geographic and florogenetic varieties of the natural plant cover. This arrangement constitutes a framework in which the vegetation units of different Schools can be classed.     

The Finnish forest site type approach: ordination and classification studies of mesic forest sites in southern Finland

A.K. Cajander's forest site type classification system is based on definition of plant communities typical to certain climatical and edaphical site conditions, but the structure and composition of the tree stands in Finland are considered sensitive to random variation and are therefore not used as primary classification criteria. The system has often received criticism, usually that the effects of the tree stand and successional stage of the stand have been underestimated. Most of the present-day forest stands in Finland represent young successional stages and are subjected to intensive management. This should result in an additional difficulty in the application of the forest site types in the field.The present study is based on three independent data sets representing forests on mineral soil in southern part of Finland. TWINSPAN classification, DCA ordination and canonical correspondence analysis (CCA) techniques were applied in successive stages of the data analysis. It was found that the definition of the intermediately fertile, mesic site types was clearly confused by the effects of the tree species and age of the stand. The analyses also revealed that the succession pathways on mesic forest sites are largely determined by the tree species composition. In stands dominated by Pinus sylvestris, the succession follows the competitive hierarchy model, whereas in stands dominated by Picea abies, severe shading of the tree canopy governs the development of understorey vegetation.Abbreviations CCA Canonical correspondence Analysis - DCA Detrended correspondence Analysis - TWINSPAN Two-way indicator species analysis     

Tests of four hypotheses on soldier production,by using wild colonies ofPheidole fervida F. Smith (Hymenoptera: Formicidae)

Following four hypotheses on the production of soldiers were tested in the Pheidole fervida colonies collected in the natural field:

1. The proportion of new soldiers is primarily dependent on the population size of old workers.
2. The abundance of old soldiers reduces the proportion of new soldiers.
3. The production of sexuals reduces the proportion of new soldiers.
4. The number of soldiers is correlated with the size of defense zone.

The present test suggested that the last idea was most likely to the wild colonies of P. fervida.     

The population dynamics of the large pine aphid,Cinara pinea (Mordv.)

The large pine aphid, Cinara pinea lives exclusively on Pinus species, where it feeds on the foliated shoots of the current and previous year. The paper describes the development of a computer model designed to simulate the aphid's population dynamics on saplings in the controlled environment of the laboratory, i.e. in the absence of natural enemies. The model was able to account for about 80% of the variation in aphid numbers within and between trees over a three month period. Sensitivity analysis revealed that the number of pine aphids is limited primarily by nymphal emigration, the operation of which is sensitive both to density and to plant quality as reflected in aphid growth rates. Of secondary importance are changes in reproduction acting through increased reproductive delay, again a result of altered growth rates and adult size. Development, too, has an important secondary influence. Contrary to expectation and conventional belief, however, alate production proved to be of negligible importance, either in limiting or regulating population numbers. Alatae are produced in too few numbers and for too short a period to significantly alter the pattern of population change.     

演替理论与植被恢复

《昆明-蒙特利尔全球生物多样性框架》提出要高质量保护和恢复各30%的土地,最大化地实现保护生物多样性和缓解气候变化的目标,而演替理论和植被恢复可以为实现30%的保护和恢复目标服务。演替理论是植被生态学中的核心理论,演替是指在一个地点上由一群不同物种组成的生命体的结构或组成随时间而变化的过程; 植被恢复是以植物种植、配置为主,恢复或重建植物群落或天然更新恢复植物群落的过程,植被恢复是生态系统结构和功能从简单到复杂、从低级向高级变化的过程,最终目的是建立健康稳定的植物群落。演替是植被恢复的基础,植被恢复被视为对演替过程的操纵,以达到恢复受损植被生态系统的目标。演替理论可以指导植被恢复,而植被恢复对演替理论的发展有益。演替按裸地性质可以分为原生演替和次生演替,有研究建议将恢复过程视为第三演替,这将有助于理解通过人为干预促进植被恢复成功的管理选择,特别是通过强调退化生态系统中的环境和生物遗存的管理选择。此外,该文还提出了植被恢复理论和演替理论未来可能重点关注的科学和技术问题。     

The legacy of harvest and fire on ecosystem carbon storage in a north temperate forest

Forest harvesting and wildfire were widespread in the upper Great Lakes region of North America during the early 20th century. We examined how long this legacy of disturbance constrains forest carbon (C) storage rates by quantifying C pools and fluxes after harvest and fire in a mixed deciduous forest chronosequence in northern lower Michigan, USA. Study plots ranged in age from 6 to 68 years and were created following experimental clear‐cut harvesting and fire disturbance. Annual C storage was estimated biometrically from measurements of wood, leaf, fine root, and woody debris mass, mass losses to herbivory, soil C content, and soil respiration. Maximum annual C storage in stands that were disturbed by harvest and fire twice was 26% less than a reference stand receiving the same disturbance only once. The mechanism for this reduction in annual C storage was a long‐lasting decrease in site quality that endured over the 62‐year timeframe examined. However, during regrowth the harvested and burned forest rapidly became a net C sink, storing 0.53 Mg C ha⁻¹ yr⁻¹ after 6 years. Maximum net ecosystem production (1.35 Mg C ha⁻¹ yr⁻¹) and annual C increment (0.95 Mg C ha⁻¹ yr⁻¹) were recorded in the 24‐ and 50‐year‐old stands, respectively. Net primary production averaged 5.19 Mg C ha⁻¹ yr⁻¹ in experimental stands, increasing by < 10% from 6 to 50 years. Soil heterotrophic respiration was more variable across stand ages, ranging from 3.85 Mg C ha⁻¹ yr⁻¹ in the 6‐year‐old stand to 4.56 Mg C ha⁻¹ yr⁻¹ in the 68‐year‐old stand. These results suggest that harvesting and fire disturbances broadly distributed across the region decades ago caused changes in site quality and successional status that continue to limit forest C storage rates.