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)     

The Spatial Structure of Variability in a Semi-arid, Fluvial Ecosystem

The arrangement and composition of flowpath types within a given network are thought to govern its functioning. This concept assumes that different flowpath types are functionally distinct. We investigated this assumption in a fluvial ecosystem by comparing the riparian zone, parafluvial zone (in-channel gravel bars), and surface stream. We hypothesized that differences in advection, uptake, and sorption would render material cycles more (a) open and (b) mutable in the surface stream, whereas the converse would occur in the riparian zone, and an intermediate state would be seen in the intervening parafluvial zone. To test our first hypothesis, we predicted that spatial heterogeneity in solute concentrations would be least in the surface stream, greater in the parafluvial zone, and greatest in the riparian zone. Using a null model, we ascertained that this pattern was shown by all solute species we examined (nitrate, ammonium, total dissolved inorganic nitrogen [DIN], dissolved organic N, total dissolved N, soluble reactive phosphorus, dissolved organic carbon, and chloride). To test our second hypothesis, we predicted that temporal change in spatial heterogeneity would be greatest in the surface stream, less in the parafluvial zone, and least in the riparian zone. Nitrate, DIN, and chloride showed this pattern. In particular, surface stream inorganic N was less spatially variable following months of high rainfall. According to an extant hypothesis, these results suggest that inorganic N processing may be a stable function in this ecosystem. Other solute species did not support our second prediction, perhaps because their retention and release dynamics are influenced principally by geochemistry. Generally, our findings indicate that a geomorphic template can generate spatial patterns in ecosystem function, warranting an expansion of the spiraling framework to a variety of flowpath types.     

Indicators of the Ecological Impact of Bottom-Trawl Disturbance on Seabed Communities

The Ecosystem Approach to Fisheries requires that managers take account of the environmental impacts of fishing. We develop linked state and pressure indicators that show the impact of bottom-trawling on benthic communities. The state indicator measures the proportion of an area where benthic invertebrate biomass (B) or production (P) is more than 90% of pristine benthic biomass (B _0.9) or production (P_0.9). The pressure indicator measures the proportion of the area where trawling frequency is sufficiently high to prevent reaching predicted B_0.9 or P_0.9. Time to recovery to B_0.9 and P_0.9 after trawling, depending on the habitat, was estimated using a validated size-based model of the benthic community. Based on trawling intensity in 2003, 53.5% of the southern North Sea was trawled too frequently for biomass to reach B_0.9, and 27.1% was trawled too frequently for production to reach P_0.9. As a result of bottom-trawling in 2003, in 56% of the southern North Sea benthic biomass was below B_0.9, whereas in 27% of the southern North Sea benthic production was below P_0.9. Modeled recovery times were comparable to literature estimates (2.5 to more than 6 years). The advantages of using the area with an ecological impact of trawling as a pressure indicator are that it is conceptually easy to understand, it responds quickly to changes in management action, it can be implemented at a relevant scale for fisheries management, and the necessary effort distribution data are centrally collected. One of this approach’s greatest utilities, therefore, will be to communicate to policy makers and fishing enterprises the expected medium- to long-term ecological benefits that will accrue if the frequency of trawling in particular parts of fishing grounds is reduced.     

Synchrony of Seed Dispersal, Hydrology and Local Climate in a Semi-arid River Reach in California

The temporal availability of propagules is a critical factor in sustaining pioneer riparian tree populations along snowmelt-driven rivers because seedling establishment is strongly linked to seasonal hydrology. River regulation in semi-arid regions threatens to decouple seed development and dispersal from the discharge regime to which they evolved. Using the lower Tuolumne River as a model system, we quantified and modeled propagule availability for Populus fremontii (POFR), Salix gooddingii (SAGO), and Salix exigua (SAEX), the tree and shrub species that dominate near-channel riparian stands in the San Joaquin Basin, CA. A degree-day model was fit to field data of seasonal seed density and local temperature from three sites in 2002–2004 to predict the onset of the peak dispersal period. To evaluate historical synchrony of seed dispersal and seasonal river hydrology, we compared peak spring runoff timing to modeled peak seed release periods for the last 75 years. The peak seed release period began on May 15 for POFR (range April 23–June 10), May 30 for SAGO (range May 19–June 11) and May 31 for SAEX (range May 8–June 30). Degree-day models for the onset of seed release reduced prediction error by 40–67% over day-of-year means; the models predicted best the interannual, versus site-to-site, variation in timing. The historical analysis suggests that POFR seed release coincided with peak runoff in almost all years, whereas SAGO and SAEX dispersal occurred during the spring flood recession. The degree-day modeling approach reduce uncertainty in dispersal timing and shows potential for guiding flow releases on regulated rivers to increase riparian tree recruitment at the lowest water cost.     

Simulation of Rapoport's rule for latitudinal species spread

Rapoport's rule claims that latitudinal ranges of plant and animal species are generally smaller at low than at high latitudes. However, doubts as to the generality of the rule have been expressed, because studies providing evidence against the rule are more numerous than those in support of it. In groups for which support has been provided, the trend of increasing latitudinal ranges with latitude is restricted to or at least most distinct at high latitudes, suggesting that the effect may be a local phenomenon, for example the result of glaciations. Here we test the rule using two models, a simple one-dimensional one with a fixed number of animals expanding in a northern or southerly direction only, and the evolutionary/ecological Chowdhury model using birth, ageing, death, mutation, speciation, prey-predator relations and food levels. Simulations with both models gave results contradicting Rapoport's rule. In the first, latitudinal ranges were roughly independent of latitude, in the second, latitudinal ranges were greatest at low latitudes, as also shown empirically for some well-studied groups of animals.     

Spatial Segregation of Congeneric Invaders in Central Pennsylvania, USA

Carduus acanthoides and Carduus nutans (plumeless and musk thistles) are among the most noxious weeds in the United States of America, presenting a serious challenge in cropping and pasture systems. Unfortunately, a lack of detailed spatial distribution information hampers both our ability to understand the factors affecting their invasive success, and the effectiveness of monitoring and management efforts. To examine patterns of distribution and co-occurrence at a local level, we sampled a 5000 km² area of central Pennsylvania that cut a transect across known areas of C. acanthoides and C. nutans infestation. A number of potential environmental explanatory variables were recorded and analyzed to examine whether they correlated with observed species distribution patterns. Patterns of forest density and spatial aggregation of the thistles were the primary covariates that significantly impacted both species’ distributions. The survey established that the frequency of sightings for each species diminished as the ranges converged, with only brief overlap: the two species are strongly negatively correlated in space. Understanding environmental correlates of infestation and the pattern of spatial dissociation of these two invasive species is an important step towards an improved understanding of the mechanisms underlying their invasive potential, and hence towards effective weed control.     

应用性遗传模式选育香菇优良菌株——中香68杂交菌株选育报告

根据香菇四极性异宗配合的性遗传特性,通过亲本的选择,采用孢子单核体的对称杂交育种手段,实现基因重组,从中选育出广温型优良菌株中香68,介绍了中香68菌丝生长和子实体特征及其新菌株的鉴别方法。同时讨论了香菇单孢杂交育种的种质资源和育种工艺。     

Restoration principles applied to cultural landscapes

Restoration models and practise to date have been applied mainly to ecosystems. More recently, there has been a focus on the “landscape perspective” of ecosystem restoration in order to improve nature conservation and management effectiveness.

Here, we clarify some of the differences between ecosystem- and landscape-oriented restoration, and propose four components that should be considered in planning and conceptualising: (a) landscape composition and configuration; (b) traditional land management techniques; (c) linear and point features; and (d) other heritage features. We further discuss the concept of reference landscapes, and the contrasts between restoration and rehabilitation. Spatial approaches to restoration are explored, comparing small areas with complete restoration (“museum landscapes”) from large areas with rehabilitation of landscape physiognomy or point and linear features. The linkages with nature conservation and the sustainable use and management of natural resources are examined in the context of a rapidly changing world.     

体外肿瘤微血管生成模型的建立

本研究以体外微血管培养模型为基础,用鼠尾胶原包埋大鼠动脉环,并将包埋的动脉环转移到种有人肺癌A549细胞单层的培养皿中,用MCDB 131无血清培养液对动脉环和肿瘤细胞进行共培养,从而建立肿瘤微血管体外生成模型。大鼠动脉环于培养后第3天从血管壁长出微血管芽,第6至10天长成微血管丛,两周后新生微血管开始萎缩;没有肿瘤细胞刺激的条件下,大鼠动脉环新生微血管数量明显减少。结果表明人肺癌A549细胞能够促进血管生成。体外大鼠动脉环肿瘤微血管培养模型操作简单、灵敏度高,适合研究肿瘤血管新生及其机制。     

马铃薯吸附干燥特性及模型拟合

在实验的基础上研究了马铃薯的干燥特性,考察了温度、湿度、风速和粒子大小对马铃薯的干燥特性的影响。对马铃薯的干燥特性进行模型拟合结果表明:马铃薯吸附式低温干燥过程分为调整、恒速和降速3个阶段。含水率从76.88%变化到65.44%这段为调整阶段;从65.44%变化到47.34%这段为恒速阶段,主要是去除非结合水;从47.34%降到27.7%为降速阶段,主要脱除非结合水及部分结合水,干燥速度下降。温度是影响干燥的主要因素,温度越高,湿度越小,介质流速快,干燥速度越快。Page模型能够较好地拟合马铃薯干燥过程的特性。