Inter and intra‐population phenotypic and genotypic structuring in the European whitefish Coregonus lavaretus,a rare freshwater fish in Scotland

This study revealed between‐lake genetic structuring between Coregonus lavaretus collected from the only two native populations of this species in Scotland, U.K. (Lochs Eck and Lomond) evidenced by the existence of private alleles (12 in Lomond and four in Eck) and significant genetic differentiation (F_ST = 0·056) across 10 microsatellite markers. Juvenile C. lavaretus originating from eggs collected from the two lakes and reared in a common‐garden experiment showed clear phenotypic differences in trophic morphology (i.e. head and body shape) between these populations indicating that these characteristics were, at least partly, inherited. Microsatellite analysis of adults collected from different geographic regions within Loch Lomond revealed detectable and statistically significant but relatively weak genetic structuring (F_ST = 0·001–0·024) and evidence of private alleles related to the basin structure of the lake. Within‐lake genetic divergence patterns suggest three possibilities for this observed pattern: (1) differential selection pressures causing divergence into separate gene pools, (2) a collapse of two formerly divergent gene pools and (3) a stable state maintained by balancing selection forces resulting from spatial variation in selection and lake heterogeneity. Small estimates of effective population sizes for the populations in both lakes suggest that the capacity of both populations to adapt to future environmental change may be limited.     

Continental‐scale syntheses of Australian pyromes – misclassification of south‐western eucalypt woodlands misinforms management

Global and continental‐scale analysis of ecological phenomena can offer important insights through the identification of patterns and associations not detectable at smaller scales. However, using proxies for ecological phenomena, such as vegetation mapping for spatially projecting fire regime niches and post‐fire plant responses, require critical examination of predictions to determine utility. Using local studies in south‐western Australia, we demonstrate that while this approach has been largely successful in mallee woodland and shrubland, it has failed in eucalypt woodland, with the consequence that values for a range of fire‐related parameters from the continent‐wide approaches, if adopted in informing management, would result in undesirable conservation outcomes for the world's largest extant temperate woodland.     

Environmental change and rain forests on the Sunda shelf of Southeast Asia: drought, fire and the biological cooling of biodiversity hotspots

Environmental change during the Quaternary period has caused changes in the composition and structure of vegetation on the Sunda shelf of Southeast Asia. Climatic conditions drier than the present, particularly during the peak of the last ice age, led to a reduction in the extent of rain forests. Most recently, there has been a close association between drought and the occurrence of major, rain forest fires. Although many rain forest trees show adaptations to periodic drought, this is not the case for frequent or intense fires. Over evolutionary time-scales, major fires may thus have been largely confined to driver vegetation types, such as monsoon and deciduous forests, and only infrequently penetrated rain forest areas. Continental-scale distribution patterns for rain forest species reveal a number of biodiversity hotspots that are consistent for a broad range of taxonomically unrelated taxa. These biodiversity hotspots account for a relatively small part of the total extent of rain forest; they may also represent ecologically relatively stable areas. This paper discusses the location and extent of biodiversity hotspots on the Sunda shelf within the context of past and present environmental change. It finds that whatever the history of biodiversity hotspots, they are increasingly threatened by contemporary environmental change, notably a trend towards increasingly frequent and intense fires. The paper concludes that the trend is likely to continue, without major changes in those activities that degrade and precondition to fire remaining areas of rain forest.     

Uncertainty Is Part of Making Decisions

Advances in computer technology and applied statistics have provided the opportunity for the non-statistician to investigate uncertainty in a quantitative manner. The following discussion argues, notwithstanding the possible misuse of uncertainty analysis, that uncertainty is always present and that decisions based on human or ecological risk assessment would benefit from disclosure of uncertainty in the estimated risks.     

Patch to landscape patterns in post fire recruitment of a serotinous conifer

Obligate seeding species are highly specialized to fire disturbance and many conifers such as cypress, which are adapted to high intensity stand-replacing fires, have canopy seed banks stored in serotinous cones. Resilience of these trees to fire disturbance is a function of disturbance frequency and one focus of this study was to determine the effect of patch age on postfire recruitment. A second focus was to determine the extent to which fire induced a landscape level change in the location of the forest boundary. Prior to a fire in 1994, a large Cupressus sargentii forest was a mosaic landscape of different aged patches of nearly pure cypress bordered by chaparral. Patches less than 60 years of age were relatively dense with roughly one tree every 1–2 m² but older patches had thinned to one tree every 3–15 m². Older trees had substantially greater canopy cone crops but the stand level seed bank size was not significantly correlated with stand age. Fire-dependent obligate seeding species are sensitive to fire return interval because of potential changes in the size of seed banks – facing both a potential `immaturity risk' and a `senescence risk'. At our site, C. sargentii regeneration was substantial in stands as young as 20 years, suggesting that fire return interval would need to be shorter than this to pose any significant risk. Reduced seedling recruitment in stands nearly 100 years of age may indicate risk from senescence is greater, however, even the lowest density seedling recruitment was many times greater than the density of mature forests – thus this cypress would appear to be resilient to a wide range of fire return intervals. Changes in landscape patterning of forest and chaparral are unlikely except after fire. Factors that inhibit tree establishment within the shrubland, as well as factors that affect shrub establishment within the forest border likely affect the `permeability' of this ecotone. After the 1994 fire this boundary appeared to be stable in that cypress recruited best within the shadow of burned canopies and cypress were weak invaders of adjacent shrublands.     

Roles of succession,light, nutrients and disturbance on population vigor and maintenance of the rare plant Solidago shortii (Asteraceae)

Results of field and glasshouse experiments on Solidago shortii, and our observations on this species over many years, were used to construct a conceptual model of the roles of succession, light, soil nutrients and disturbance on population vigor and maintenance of this federal-endangered species. As cover of woody vegetation increased at a population site between 1986 and 1992, number of flowering ramets of S. shortii significantly decreased but number of vegetative ramets remained nearly constant. Adult plants transplanted into a redcedar thicket and those shaded in a glasshouse produced many fewer flowering ramets and capitula per flowering ramet and less biomass and had higher mortality than those in the open. Seedlings/juveniles shaded in a glasshouse had significantly less dry biomass; lower RGR, NAR, leaf area and root/shoot ratio and higher LAR, SLA and LWR than nonshaded ones. In a field site and glasshouse, fertilized plants (NPK) consistently had more flowering ramets and capitula per flowering ramet than nonfertilized ones. Hierarchy of dry weight of plants grown in a glasshouse in soils derived from five types of bedrock was phosphatic limestone > calcareous shale > sandstone > black shale = dolomite. Flowering and biomass production in the field-fertilizer and soil-type experiments were associated closely with levels of P. Number of flowering ramets significantly increased in plants transferred from shaded to nonshaded glasshouse conditions, but no such increase occurred after opening the canopy above plants in a thicket. Both high light and high nutrient levels apparently are necessary to maintain high vigor of S. shortii. In areas subject to invasion by woody plants, periodic high intensity disturbance may be required to prevent population extirpation.     

Studies on Wood Anatomy of Eucalyptus globulus Under Different Habitats

Wood anatomy of Eucalyptus globulus Labill. under different habitats was comparatively studied under light and scanning electron microscope. According to the eleven major quantitative perimeters of wood characteristics of E. globulus viz: vessel frequency, percentage of solitary vessels, vessel diameter, vessel member length; tracheid length and diameter; fibre tracheid length and diameter; libriform fibre length; ray frequency and ray height, the plants under different habitats have been made a comparison. The results showed that growth ring was indistinct, and there was a positive correlation between the quantitative characters of most wood constituent members were positively correlated with the latitude except for some of vessel frequency decreased. The decrease in effects of annual rainfall on the structure of the wood of E. glotrulus were evaluated.     

我国主要类型生态系统结构功能与提高生产力途径研究──KJ85－06项目1991～1995研究进展简介

KJ 85-06项目是“八五”期间由中国科学院资助的最大的生态学研究计划.19个研究所、20个试验站、530余名科技人员参加了该项计划,5年总经费1000万元.研究工作取得了重大进展,迄今已发表论文450余篇、专着3部,尚有大量论文与多部专着将陆续出版.本文简要介绍了有关主要研究进展,并就生态系统优化管理研究和生态过程、人类活动影响联网研究提出了两点主张.