原子力显微镜定量测定采后蘑菇的表面粗糙度(英文)

蘑菇表面的失水情况是评价采后蘑菇质量的重要指标。我们提出用原子力显微镜定量测定蘑菇表皮的粗糙度来表示表面的皱缩程度,用算术平均粗糙度和平方根粗糙度表示。双孢蘑菇(Agaricus bisporus(Lange)Sing)贮藏前的算术平均粗糙度为(34.033±5.116)nm,经过2d贮藏,在2℃、25℃和动态温度自发气调贮藏下,其算术平均粗糙度分别为(40.139±3.359)nm、(65.356±8.253)nm和(43.670±9280)nm。平方根粗糙度值与算术平均粗糙度值有相似的变化趋势,两者均随贮藏时间的延长和温度的增加而增大。表皮的三维图像直观地表示出水分的蒸发过程,变化趋势符合粗糙度值的变化,特别是在贮藏的早期阶段(0～2d)。由粗糙度分析的结果可以区别不同的贮藏条件表明,原子力显微镜测定的粗糙度指标可有效地表示采后蘑菇的表面失水情况。     

Relevance of exotic pine plantations as a surrogate habitat for ground beetles (Carabidae) where native forest is rare

Plantation forests are of increasing importance worldwide for wood and fibre production, and in some areas they are the only forest cover. Here we investigate the potential role of exotic plantations in supporting native forest-dwelling carabid beetles in regions that have experienced extensive deforestation. On the Canterbury Plains of New Zealand, more than 99% of the previous native forest cover has been lost, and today exotic pine (Pinus radiata) plantations are the only forest habitat of substantial area. Carabids were caught with pitfall traps in native kanuka (Kunzea ericoides) forest remnants and in a neighbouring pine plantation, grassland and gorse (Ulex europaeus) shrubland. A total of 2,700 individuals were caught, with significantly greater abundance in traps in young pine, grassland and gorse habitats than in kanuka and older pine. Rarefied species richness was greatest in kanuka, a habitat that supported two forest specialist species not present in other habitat types. A critically endangered species was found only in the exotic plantation forest, which also acts as a surrogate habitat for most carabids associated with kanuka forest. The few remaining native forest patches are of critical importance to conservation on the Canterbury Plains, but in the absence of larger native forest areas plantation forests are more valuable for carabid conservation than the exotic grassland that dominates the region.     

Slow understory redevelopment after clearcutting in high mountain forests

Besides natural tree regeneration itself, the development of the forest understory community is highly indicative of the ecological recovery of forest stands post-harvesting, and therefore of the sustainability of forest management. High mountain forests might show particularly slow recovery of the understory plant community because of harsh environmental conditions. We compared understory community richness and composition among three age classes of forest stands in the subalpine Engelmann Spruce–Subalpine Fir zone in the interior of British Columbia, Canada. Species composition was found to differ significantly between mature stands (>110 years old and never harvested) and both recent clearcuts (5–8 years old) and the oldest clearcuts present in the study area (second growth: 24–28 years old). A non-metric multidimensional scaling (NMDS) ordination revealed no unidirectional return of species composition in harvested stands towards that of mature forest; indeed, plots in recent clearcuts and second growth stands were similar to one another and clearly separated from the mature stands. Indicator Species Analysis revealed that moss species were particularly indicative of mature forest, with four moss species being common in mature stands but absent from both younger stages. Compared to what has been reported for lower elevation coniferous forests, e.g. in the U.S. Pacific Northwest, redevelopment of the understory appears to be slow after harvesting in these high elevation mountain forests. Rotation intervals that consider the natural temporal pattern of species turnover and the occurrence interval of major natural disturbances (here: fire) should provide effective approaches to sustainable forest management of these forests.     

Large-scale occurrence patterns of red-listed lichens and fungi on old oaks are influenced both by current and historical habitat density

Current occurrence patterns of species associated with ancient trees may reflect higher historical habitat densities, because the dynamics of the habitat and the colonisation-extinction processes for many inhabiting species are expected to be slow. We tested this hypothesis in southeast Sweden by analysing species occurrence per parish for twelve redlisted lichen species and nine redlisted fungus species in relation with current density of big oaks, the density of oaks in the 1830s and connectivity with parishes with the species present. For most species, the occurrence was positively related with current density of habitat (for 18 species out of 21) and parish area (for 16 species). Historical habitat density was positively related with occurrence for 11 species, while connectivity with current occurrences in the surroundings was positive for the occurrence of 12 species and negative for the occurrence of two. For lichen species the connectivity measure that best explained the variation was at a larger spatial scale as compared to fungus species. Even if the density of old oaks remains in the future, inhabiting species will most likely decline because their distribution patterns are not in equilibrium with the current habitat density. Therefore, to allow long-term persistence of inhabiting species the number of old oaks should be increased. Areas where such an increase is most urgent could be identified based on species occurrence data and current habitat density, but because species data will always be incomplete data on the historical habitat distribution is valuable.     

Conservation of protists: is it needed at all?

Protists have scarcely been considered in traditional perspectives and strategies in environmental management and biodiversity conservation. This is a remarkable omission given that these tiny organisms are highly diverse, and have performed as key ecological players in evolutionary theatres for over a billion years of Earth history. Protists hold key roles in nearly all ecosystems, notably as participants in fluxes of energy and matter through foodwebs that centre on their predation on microbes. In spite of this, they have been largely ignored in conservation issues due to a widespread, naive belief that protists are ubiquitous and cosmopolitanously distributed. Nevertheless, recent research shows that many protists have markedly restricted distributions. These range from palaeoendemics (Gondwanan-Laurasian distribution) to local endemics. Our ignorance about the ultimate and proximate causes of such acute disparities in scale-dependent distributions of protists can be flagged as a singular reason to preserve these more cryptic participants in ecological and evolutionary dynamics. This argument is disturbing when one considers anthropogenic modifications of landscapes and the very poorly understood roles of protists in ecological processes in soils, not least in agroecolandscapes and hydrological systems. Major concerns include host specific symbiotic, symphoric and parasitic species which become extinct, unseen and largely unknown, alongside their metazoan hosts; change or loss of habitats; massive change or loss of type localities; and losses of unique genetic resources and evolutionary potential. These concerns are illustrated by examples to argue that conservation of protists should be integral to any strategy that traditionally targets vascular plants and animals. The ongoing decline in research capacity to inventory and classify protist diversity exemplifies a most acute symptom of the failures, at local, national and international levels, to support scientific responses to the biodiversity crisis. Responsible responses to these severe problems need to centre on the revival of natural history as the core discipline in biology. F. P. D. Cotterill: Formerly Principal Curator of Vertebrates, Natural History Museum of Zimbabwe, P.O. Box 240, Bulawayo, Zimbabwe Special Issue: Protist diversity and geographic distribution. Guest editor: W. Foissner     

Interspecific Pollen Transfer: Magnitude,Prevalence and Consequences for Plant Fitness

Interspecific pollen transfer (IPT) is one of the mechanisms underlying potential competition among plants for pollinators, and it refers to movement of pollen between different plant species by pollinators that visit their flowers simultaneously. Two components of IPT, related to each other, are distinguished: (a) heterospecific pollen deposition (HPD) on conspecific stigmas, which may interfere with fertilization by conspecific pollen; and (b) conspecific pollen loss (CPL) on heterospecific flowers, which may reduce the amount of pollen transferred between conspecific flowers. Thus, IPT may lead to reciprocal losses for male and female functions of the plant, with potentially important ecological and evolutionary consequences. In this review, we explore the magnitude and prevalence of IPT, examining documented mechanisms and evaluating such potential ecological and evolutionary consequences. We compiled existing evidence of interspecific pollinator sharing and interspecific pollinator switching between flowers of different species in natural communities. We evaluated the relative importance of both HPD and CPL from studies comparing these variables in pure vs. mixed floral neighborhoods, analyzing evidence for the claim that IPT is an evolutionary force promoting character displacement in habitat affinity, flowering times, and floral morphology. We also examined the findings of hand-pollination experiments carried out to reveal different mechanisms by which heterospecific pollen can affect performance of native pollen. Finally, we review evidence for impacts of alien plant species on native species' reproduction, and briefly comment on risks of crop-to-wild gene flow imposed by the release of genetically modified (transgenic) crops through IPT.     

The effect of footrot on weight gain in sheep

Footrot is a highly contagious bacterial disease of sheep affecting the interdigital skin and surrounding soft and hard horn of a hoof, often resulting in severe lameness. This study was aimed at estimating the effect of footrot on weight gain of affected animals, and characterising the variation between animals in terms of phenotypic, environmental and genetic components. A general approach was developed describing the relationship between the disease and weight gain, defining new traits such as the maximum weight loss as a result of disease and the time after infection that this occurs. In two trials, 1267 Merino sheep were artificially challenged with footrot when 10 months old and re-infected through exposure to footrot on pasture 33 weeks later. Their feet were scored for footrot and live weights were measured approximately every 3 weeks. From data on animals that were not affected by footrot throughout each trial, normal growth curves were calculated and applied to affected animals to predict their growth had they remained healthy, so that weight loss as a result of footrot could be predicted. Animals with average footrot severity in the two trials suffered weight losses of 0.5 to 2.5 kg live weight, but most animals regained lost live weight later in the trials as footrot healed following vaccination. The estimates of the heritabilities of weight loss, adjusted for the severity of footrot, were about 0.30 and 0.15 in the experimental and natural challenge groups, respectively. Animals with higher genotypic values for weights at the start of each trial appeared to cope better with infections, in terms of lower weight losses. The time of highest footrot score and the time of maximum weight loss after infection had only very small genetic components.