Correlation between soil characters and forest types: a study in multiple discriminant analysis

Multiple discriminant analysis is a useful multivariate technique in vegetation studies that can be employed for several purposes, even if the underlying statistical assumptions are not satisfied. An example of application of this method is discussed: multiple discriminant analysis was successfully used for evaluating the predictivity of forest types defined by numerical classification of vegetation data with respect to soil variables.Species nomenclature follows Pignatti (1982) for vascular plants and Augier (1966) for mosses.The research has been supported by the IDROSER (Bologna, Italy) and by the Italian C. N. R. (Grant no. 83.02548.04, resp. Prof. A. Pirola). We wish to thank Prof. E. Feoli, Prof. E. van der Maarel, Prof. L. Orlóci and Prof. A. Pirola for suggestions. We are also indebted to Dr N. Filippi who analyzed the soil samples.     

链格孢属(丝孢纲)数值分类研究初探

聚类分析树状图上Alternarla与其相似属Ulocladium、Stemphylium的种明确地分为三个表观群。36个OTU's,23个链格孢属的种,进一步形成四个清晰的亚表观群,恰与椐分生孢子喙的特征而划分的组,即无喙组、假喙组、真喙组和锥状真喙组相吻合。本试验系统中,相似属间、种间和种内的相似性值是在具体试验条件下确定的。其意义在于通过对大量有用分类信息的综合比较分析,以相似性值的形式,为不同等级单位分类地位的确定提供相应定量化的标准,从而能够比较全面地评价一个分类单位.根据研究结果,建议将Alternariamali Roberts作为细链格孢的一个分化型,即Alternarin tenuis C.G.Nees f.sp.,mali。     

Modeling impacts of Yangtze River water transfer on water ages in Lake Taihu, China

To improve water quality and alleviate eutrophication in Lake Taihu, the third largest freshwater lake in China, a Yangtze River water transfer project was initiated in 2002 to bring water from the Yangtze River to Lake Taihu to dilute and divert pollutants out of the lake. We used a three-dimensional numerical model, Environmental Fluid Dynamics Code, to study the impacts of water transfer on the transport of dissolved substances in the lake by using the concept of water age. In particular, the influences of inflow tributaries and wind forcing on water age were investigated. Model results showed that the effect of water transfer on transport processes in the lake is strongly influenced by hydrodynamic conditions induced by wind and inflow/outflow tributaries. During the simulation year (2005), the water ages in Lake Taihu were highly variable both spatially and temporally, with a mean of approximately 130 days in summer and 230 days in the other seasons. Southeasterly winds—dominant in the summer—could improve the quality of water by reducing the water age in the eastern areas of the lake, which are used as a drinking water source, and in Meiliang Bay, the most polluted bay. In terms of dilution, the most efficient flow rate for transferred water was predicted to be approximately 100 m³/s. The spatial distribution of water ages showed that water transfer may preferentially enhance exchanges in some areas of the lake unless nutrient concentrations in the transferred water are reduced to a reasonable level. This study provides useful information for a better understanding of the complex hydrodynamic and mass transport processes in the lake, which is important for developing and implementing effective ecological restoration strategies in the region.     

Modeling aggregation and growth processes in an algal population model: analysis and computations

 Aggregation, the formation of large particles through multiple collision of smaller ones is a highly visible phenomena in oceanic waters which can control material flux to the deep sea. Oceanic aggregates more than 1 cm in diameter have been observed and are frequently described to consist of phytoplankton cells as well as other organic matter such as fecel pellets and mucus nets from pteropods. Division of live phytoplankton cells within an aggregate can also increase the size of aggregate (assuming some daughter cells stay in the aggregate) and hence could be a significant factor in speeding up the formation process of larger aggregate. Due to the difficulty of modeling cell division within aggregates, few efforts have been made in this direction. In this paper, we propose a size structured approach that includes growth of aggregate size due to both cell division and aggregation. We first examine some basic mathematical issues associated with the development of a numerical simulation of the resulting algal aggregation model. The numerical algorithm is then used to examine the basic model behavior and present a comparison between aggregate distribution with and without division in aggregates. Results indicate that the inclusion of a growth term in aggregates, due to cell division, results in higher densities of larger aggregates; hence it has the impact to speed clearance of organic matter from the surface layer of the ocean. Received 1 July 1994; received in revised form 23 February 1996     

Geographical variation in frond size,rootstock density,and sexual reproduction in <Emphasis Type="Italic">Matteuccia struthiopteris</Emphasis> populations in Norway

The main aim of this study was to quantify differences in the structure of dense Matteuccia struthiopteris (L) Todaro among geographically separated populations in Norway, and to relate these differences to variation in environmental variables. A stratified random sampling procedure was applied to select 4 m² quadrats restricted to populations dominated (>75% cover) by the fern. This dimorphic fern can produce three types of leaves (fronds): fertile (sporophyll) and sterile (trophophyll), and in addition also intermediate fronds. In all, 178 populations from different parts of the country were analysed, and in total 9,346 rootstocks were measured. Fifteen percent of the rootstocks were fertile, each producing from one to eight sporophylls, and 2.0% had developed intermediate fronds. Rootstocks with five or more sporophylls were mainly found in Southern Norway. Within the plots, there were major variations in density (10–112), number of small (new) ramets (0–58), total number of sporophylls (0–94) and estimated total fern wet-weight (0.33–22.8 kg). All new additions to the populations were connected to a mother plant (ramets), and none were of sexual origin (genets). The main environmental variables associated with the variation in population structure were mean July temperature (highly correlated with altitude and latitude), mean precipitation and density of the canopy cover. The density of small ramets and number of intermediate fronds increased from south to north. The latitudinal variation in sporophyll development and maximum trophophyll height was best explained by a unimodal model. There were statistically significant differences in the population structure between the eight studied geographic areas in Norway.     

Mediterranean hay meadow communities: diversity and dynamics in mountain areas throughout the Iberian Central Range (Spain)

This paper reports a phytosociological study on managed hay meadow communities in the main mountains of the Spanish Central Range. Multivariate techniques (Cluster analysis and CA-ordination) were applied in the classification of the relevés and ordination of vegetation units and species. Clusters were related to the following associations: Agrostio castellanae–Arrhenatheretum bulbosi, Festuco amplae–Cynosuretum cristati, and F. amplae–Agrostietum castellanae. The scattergram suggested that the dynamic patterns between communities are associated with soil nutrient content and moisture. We propose a new subassociation: F. amplae–A. castellanae gaudinietosum fragilis that includes Salmantincensean Agrostis castellana communities growing in regions with lower supramediterranean thermotype.     

芍药品种的数量分类研究

将数量分类方法应用于芍药品种的分类。选取了５６个性状,对６０个品种进行烽量分类,结果表明,由于组成花朵的单花数量不同,芍药品种首先分成了单花类和台阁花类两大类,有２朵花乃至数朵花叠合构成台阁花类。由于花瓣来源不同,各类中的芍药品种又分成了两个亚类;以花瓣自然增多为主形成的千层亚类和以雄蕊瓣化为主形成的楼子亚类,最后由于花部基本结构的差异及重瓣程度不同将艾药品咱分成了１４个花型。对芍药品种的因子分析     

Impacts of environmental scenarios on chlorophyll-a in the management of shallow, eutrophic lakes following biomanipulation: An application of a numerical model

Accurate prediction of species changes in lake ecosystems following biomanipulation measures is of paramount importance in view of water quality management. The temporal variation of phytoplankton biomass as chlorophyll-a and transparency as Secchi depth measurements are studied in the Lake Bleiswijkse Zoom, The Netherlands, with a comprehensive structural dynamic model. In the formulation of the biological model, phytoplankton as several species, zooplankton, detritus, planktivores and benthivores, and piscivores are considered to be major contributing state variables for the model. The primary goal of this paper is to describe the possible impacts of several environmental scenarios on chlorophyll-a biomass qualitatively as it would help lake and environmental managers and relevant authorities elucidate the processes of eutrophication and biomanipulation in a broad way. Some of the scenarios that have been studied by this model are: (1) The effect of fixed stoichiometry in terms of internal nitrogen and phosphorus that are tied up within algal cells; (2) the effects of external phosphorus limitation; (3) light limitation and external nitrogen limitation on algal growth; (4) probable consequences that have taken place within the chlorophyll-a biomass due to change in biomasses of various aquatic organisms; and (5) possible changes of chlorophyll-a biomass due to higher temperatures caused by global warming.     

核素迁移的二维非平衡吸附数值模式研究

为了进一步研究核素在孔隙介质中的迁移规律,本文将水动力弥散方程与核素在孔隙介质中非平衡吸附关系式相耦合,建立了非平衡吸附数值模式,并给出了非平衡吸附数值模式中吸附解吸速率参数的获取方法．为了检验所建模式与编制的程序的正确性,利用试验场（８５）Ｓｒ迁移的野外试验资料进行了计算,并与核素迁移平衡吸附数值模式的计算结果进行了对比．结果表明,二维非平衡吸附核素迁移数值模式能够更好地描述核素迁移实际．