不同除草方式对浙西南柑橘园杂草群落及其多样性的影响

于2005年6月—2008年5月在浙江衢州市柑橘主产区,运用群落生态学方法研究了化学除草、人工除草和化学除草+人工除草3种方式对果园杂草群落及其多样性的影响.结果表明:化学除草试验区杂草为17科46种,人工除草试验区杂草为20科59种,化学除草+人工除草试验区杂草为18科51种,对照区杂草为25科75种.化学除草处理的杂草物种丰富度指数、Shannon多样性指数和Shannon均匀度指数最低,人工除草处理最高,表明化学除草对果园杂草多样性的影响最大.在浙西南柑橘园既要防除杂草,又要维持果园杂草的多样性,建议采取化学除草+人工除草的方式.     

宠物重要疫病免疫与监测

宠物疫病特别是人兽共患病严重危害着宠物健康和公共卫生安全。通过对我国宠物疫苗研发和应用现状进行分析,提出关于开展疫苗质量监控技术和免疫抗体检测技术研究,以建立宠物疫苗质量监控体系和免疫抗体监测体系的建议。免疫试纸快速检测技术是一种敏感、快捷的一步法检测技术,适用于多种分析物的快速、低成本即时检测。本实验室建立了抗原、抗体和半抗原3类靶标物的免疫试纸快速检测技术体系,研制成功动物疫病抗原、抗体快速检测试纸系列产品,真正实现了长期以来人们在检测技术领域所追求的＂特异、敏感、快速、简便＂的目标,为实现动物疫病快速诊断和实时监测提供技术支撑。     

The effects of flooding,plant traits,and predation on purple loosestrife leaf‐beetles

Classical biological weed control is based on the premise that introducing specialized natural enemies from the native range re‐establishes herbivore control of plant invaders, ultimately leading to negative population growth rates. Evidence from past biocontrol programs suggests that herbivores are not solely responsible for shaping plant demography. Diverse environmental conditions in the introduced range may not only affect demography, but also influence top‐down control of target plants. We investigated how flooding affects impacts of predators (top‐down) and plant quality (bottom‐up) on performance of two leaf‐beetles, Galerucella calmariensis L. and Galerucella pusilla Duftschmid (Coleoptera: Chrysomelidae: Galerucini), released in North America as biocontrol agents of purple loosestrife, Lythrum salicaria L. (Lythraceae). Predation and flooding regime have been linked to low leaf‐beetle recruitment at sites where insects failed to attain outbreak populations. Predator exclusion experiments at adjacent flooded and non‐flooded sites indicated a positive effect of flooding on leaf‐beetle survival for all developmental stages, whereas predator exposure had little effect. There was no difference in predation rates at sites with successful or failed purple loosestrife control, questioning the importance of predation in limiting growth and impact of these biocontrol agents’ populations. Effect of flooding on purple loosestrife quality was evaluated in a common garden study where plants were grown under different flooding treatments. Plants grown in flooded soil had higher water content and lower tannic acid concentration than plants grown in well‐drained soil. Consistent with field observations, leaf‐beetle oviposition rate and survival were higher on flooded plants. Results indicate that both bottom‐up and top‐down forces operate on Galerucella populations, yet their relative strength is mediated by flooding regime. Ignoring intricacies of plant‐herbivore and trophic interactions in the introduced range appears to be a major handicap for the improvement of weed biocontrol programs.     

A modelling approach to estimate the effect of exotic pollinators on exotic weed population dynamics: bumblebees and broom in Australia

The role of mutualisms in contributing to species invasions is rarely considered, inhibiting effective risk analysis and management options. Potential ecological consequences of invasion of non‐native pollinators include increased pollination and seed set of invasive plants, with subsequent impacts on population growth rates and rates of spread. We outline a quantitative approach for evaluating the impact of a proposed introduction of an invasive pollinator on existing weed population dynamics and demonstrate the use of this approach on a relatively data‐rich case study: the impacts on Cytisus scoparius (Scotch broom) from proposed introduction of Bombus terrestris. Three models have been used to assess population growth (matrix model), spread speed (integrodifference equation), and equilibrium occupancy (lattice model) for C. scoparius. We use available demographic data for an Australian population to parameterize two of these models. Increased seed set due to more efficient pollination resulted in a higher population growth rate in the density‐independent matrix model, whereas simulations of enhanced pollination scenarios had a negligible effect on equilibrium weed occupancy in the lattice model. This is attributed to strong microsite limitation of recruitment in invasive C. scoparius populations observed in Australia and incorporated in the lattice model. A lack of information regarding secondary ant dispersal of C. scoparius prevents us from parameterizing the integrodifference equation model for Australia, but studies of invasive populations in California suggest that spread speed will also increase with higher seed set. For microsite‐limited C. scoparius populations, increased seed set has minimal effects on equilibrium site occupancy. However, for density‐independent rapidly invading populations, increased seed set is likely to lead to higher growth rates and spread speeds. The impacts of introduced pollinators on native flora and fauna and the potential for promoting range expansion in pollinator‐limited ‘sleeper weeds’ also remain substantial risks.     

Sheep grazing vs. cutting: regeneration and soil nutrient exploitation of the grassland weed Rumex obtusifolius

Broad-leaved dock (Rumex obtusifolius L., Polygonaceae) is an agronomically important perennial weed causing decreases in pasture yields and fodder quality. Non-chemical control measures for dock are often limited to frequent pulling and cutting, additionally it is usually avoided by grazing animals. Here, the regeneration of R. obtusifolius in a Rumex-infested grassland grazed by a sheep breed that explicitly feeds on dock (Ovis aries L. cv. East Prussian Skudden) was compared to cutting. Therefore, regeneration of 90 R. obtusifolius plants of three different size classes was monitored in three plots during three grazing and cutting cycles. Plant height and number of fruit-stands of regrown R. obtusifolius was significantly lower, number of leaves significantly higher after grazing than after cutting, while plant diameter was unaffected. Initially medium and large-sized plants (>40 cm diameter) were significantly more sensitive to grazing or cutting than initially smaller sized plants. Soil nitrate and ammonium concentrations in the vicinity of R. obtusifolius correlated with some regrowth parameters but were not affected by grazing or cutting. Sheep-grazed grassland communities comprised fewer legumes (p = 0.002), more grasses (p = 0.010) and fewer sward gaps (p = 0.025) than cut grassland. At the end of the experiment, abundance of R. obtusifolius in sheep grazed plots was lower than in cut plots (p = 0.089) suggesting that regrowth potential of this weed was depleted by continuous grazing and higher sward density. In conclusion, these data suggest that sheep could be considered in grassland management schemes to both directly and indirectly control Rumex infestations.     

The Effects of Habitat on Dispersal Patterns of an Invasive Thistle, Cynara Cardunculus

Dispersal of offspring is a critical step in the spread of invasive species, yet dispersal patterns are seldom well studied, inhibiting effective management and ecological understanding of invasions. Dispersal patterns can be affected by characteristics of the parent plant and by climatic or site characteristics, including community vegetation structure, but these factors have not been studied in the context of plant invasion processes. Cynara cardunculus (L.) is a polycarpic perennial thistle invasive in coastal grasslands in California that produces large numbers of wind-dispersed seeds. This study quantified and compared C. cardunculus dispersal patterns in an exotic grassland (vegetated site) and an agricultural field (non-vegetated site). Seed size variation in C. cardunculus was also quantified within inflorescences, between inflorescences, and between years of production, and compared across dispersal distances. Results indicate that dispersal distance increased dramatically from less than 20 m in the vegetated site to more than 40 m in the non-vegetated site. Plants producing fewer seeds produced heavier seeds and dispersal distance decreased over time, but seed size was not related to dispersal distance, which may serve to spread the risk to seeds or seedlings across the environment. C. cardunculus has great potential for dispersal in open areas such as agricultural fields or disturbed sites, but may be limited in highly structured natural communities. Management of C. cardunculus and other wind-dispersed plant invasions may be improved by prioritizing populations with open or disturbed areas downwind and minimizing the removal of vegetation during dispersal.     

The Impact of the Weed Chrysanthemoides monilifera ssp. rotundata on Coastal Leaf Litter Invertebrates

In coastal areas of Australia, there are extensive infestations of the environmental weed Chrysanthemoides monilifera ssp. rotundata (bitou bush). This study looked at the impact of long-term infestations on the abundance and assemblage composition of leaf litter invertebrates. Assemblages were compared in weed infested and native shrublands along the New South Wales coastline over 12 months. The total abundance was not significantly reduced in the weedy habitat but the abundance of mites, thrips, spiders, ants, and centipedes was reduced at many sites. The invertebrate assemblages also differed between habitats, with the C. monilifera supporting a lower diversity of beetles. However, the millipedes, amphipods, earthworms, pseudoscorpions and isopods appeared to respond positively to the invasion, occurring in higher abundance and detected more frequently in the weedy areas. This has been partially attributed to a change in microclimate within the C. monilifera infestations. It is generally moister and darker, which these invertebrates tend to prefer. Secondly, C. monilifera produces less leaf litter of higher quality, and possibly higher palatability than the native sclerophyllous vegetation, which may encourage species that consume litter.     

Is Hybridization Responsible for Invasive Growth of Non-indigenous Water-milfoils?

Heterosis, or hybrid vigor, has recently been proposed as a factor promoting invasive growth of some non-indigenous aquatic plant species, particularly those capable of spreading rapidly within and among lakes through clonal reproduction. We tested this hypothesis for variable-leaf water milfoil (Myriophyllum heterophyllum), a non-indigenous aquatic plant that has become a major management and conservation concern in New England. Using nuclear ribosomal DNA, we looked for F₁ hybrid populations of invasive M. heterophyllum in 25 New Hampshire (NH) lakes. In contrast to a previous study that found F₁ hybrid lineages of invasive M. heterophyllum in Connecticut, we did not find hybrids in our study lakes. This result has two implications: (1) pure lineages of M. heterophyllum are also capable of invasive growth, and (2) the distribution of invasive M. heterophyllum lineages (hybrid vs. pure) may be spatially structured across New England. We stress the importance of more detailed distributional and ecological studies for understanding the invasive potential of this species.     

Comparative Population Dynamics of an Invading Species in its Native and Novel Ranges

Although the ecology of many exotic invaders has been intensively examined in the novel range, few studies have comparatively explored how population dynamics differ in native and novel parts of an invading plants’ range. The population dynamics of mile-a-minute weed, Polygonum perfoliatum L., was explored in both the native (Japan) and novel (northeastern USA) portions of its range and evaluated using periodic matrix models. Projected per capita population growth rate (λ) varied within and between native and novel range populations. Surprisingly, five of the six populations in the novel range were projected to fail to replace themselves (λ<1) while only two of the four native range populations were projected to decline, although these projections had wider confidence intervals than in the novel habitat. While changes in germination, survivorship, fecundity and seed banking would have equivalent effects on population growth in the invasive habitat, small increases in plant survivorship would greatly increase λ in native populations. The differences between native and novel population growth rates were driven by lower adult survival in the native range caused by annual flooding and higher fecundity. Simulation analyses indicated that a 50% reduction in plant survival would be required to control growing populations in the novel range. Further comparative studies of other invading species in both their native and novel ranges are needed to examine whether the high per capita population growth and strong regulatory effects of adult survival in the native habitat are generally predictive of invasive behavior in novel habitats. Sachiko Araki: (Deceased)