Dispersal of vascular plants by game in northern Germany. Part I: Roe deer (<Emphasis Type="Italic">Capreolus capreolus</Emphasis>) and wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis>)

The endozoochorous and epizoochorous dispersal of vascular plant species by roe deer (Capreolus capreolus) and wild boar (Sus scrofa) was investigated in forest areas of Schleswig-Holstein and Lower Saxony, Germany. The primary aim of this study was to learn about which plant species and in what numbers diaspores are dispersed by the two wild ungulate species. In particular, the significance of zoochory for species composition and biodiversity of forests was evaluated. Fresh faecal pellets were collected from April–November 2001 in the forests of the two study areas. In addition, the coats and hooves of shot roe deer and wild boar were brushed out. The number of viable seeds was determined by greenhouse germination (seedling emergence method). The samples were spread in trays over sterilized soil from the study forests and were kept under controlled conditions in the greenhouse for 12 months. A total of 2,473 individuals from 77 vascular plant species were recorded. While roe deer exceeded wild boar concerning seed contents in the faeces, the significance of roe deer for epizoochorous dispersal was relatively low compared with wild boar. An analysis of the habitat preference of the vascular plant species dispersed by the two ungulate species revealed a high proportion of species growing in forests as well as in the open landscape, and also of non-forest species, while woody plants and herbaceous species closely tied to forest habitats were severely underrepresented. We also discuss consequences for forest ecology and nature conservation.     

Geochemical tracing and spatial evolution of the sediment bed load of the Romaine River,Québec,Canada

A four-reservoir hydroelectric complex which is projected on the Romaine River, in eastern Québec, Canada, will likely lead to the complete settling of the sand-size bed load of the river. In order to characterise the present river bed load sources, sediment transport and sedimentary connectivity, a study was conducted to document the compositional continuum of the lower 300 km portion of the river. Bed load samples were collected during the late summer low water period and ICP-MS geochemical analyses of the light and heavy mineral portions were conducted. Principal component analysis of the results successfully identified a series of distinctive geochemical domains. Multivariate Euclidean distance coefficients were also calculated between consecutive samples along the river revealing major bed load compositional breaks. These results indicate a longitudinal fractionation of the bed load along the 300 km course of the river. This is further supported by the sedimentary budget calculated from the annual sedimentary input derived from erosion rates of the river banks, from sediment bed load measurements at three gauging stations and from calculated bed load transport capacity at these three locations. It appears that significant sediment accommodation space is available on the upper course (250 km) of the Romaine River, in spite of the fact that this river has drained highly sediment-laden meltwaters from the receding Laurentide Ice Sheet, some 10 ka ago. This accommodation space leads to the renewal of the bed load due to recurrent partial to complete sedimentation. The major part of the bed load reaching the Romaine River mouth originates from the lower 50 km of the river course.     

南京东郊生物多样性保护核心绿地分析方法研究

以南京东郊绿地系统为对象,在ArcGIS 9.2、连通性分析软件conefor sensinode 2.2的支持下,以2005年南京东郊SPOT 5卫星影像、2005年南京快速交通矢量化文件为主要信息源,采用巧合概率指数(LCP)、整体连通性指数(IIC)、可能连通性指数(PC)和重要值(dI)等评价指标,分析研究区内的绿地斑块等级、连通性和空间结构。在此基础上,利用连通性指数确定生物多样性保护核心绿地区域。结果表明:以青龙山为主的24个绿地斑块,面积占研究区绿地斑块总面积的35%,构成了研究区域生物多样性保护的核心绿地;核心绿地斑块平均大小、最大斑块占景观面积比例2项指标分别比研究区高出0.31、59.46,景观边缘密度、景观形状指数2项指标分别比研究区低13.55、6.59;宁杭公路和沪宁高速2条快速通道对核心绿地的屏障作用最大。提出快速交通影响下南京东郊生物多样性保护核心绿地的管理对策。     

图的平均边连通度

证明了-K（G）≤-λ（G）≤-δ（G），给出了给定顶点数、边数、边连通度的图的最大平均边连通度的计算公式．     

Surface Disturbance and Erosion by Pigs: A Medium Term Assessment for the Monsoonal Tropics

Introduced pigs (Sus scrofa ) are recognised as having significant environmental impacts. Here, we quantify the effect of feral pigs in a catchment (undisturbed by Europeans) in the monsoonal tropics of northern Australia. Field data collected over a 5‐year period showed that the areal extent of pig disturbance ranged from 0·3 to 3·3% of the survey area (average 1·2%, σ = 0·9%). Mass of exhumed material was considerable and ranged from 4·3 to 36·0 Mg ha⁻¹ y⁻¹ (average 10·9 Mg ha⁻¹ y⁻¹). The excavations produce surface roughness which acts as sediment traps. Over the 5‐year study period, there was no evidence to suggest that pigs produce any rill or gully erosion. There does not appear to be any relationship between rainfall amount and area disturbed or volume of material exhumed. However, a significant positive relationship was observed between number of disturbances and rainfall. The location of any disturbance appears to be random and has no relationship with topography or geomorphic attributes such as slope, upslope contributing area or wetness indices derived from a high‐resolution digital elevation model of the site. While pigs are disturbingly relatively large volumes of soil, there is no clear evidence to support any increase in local erosion and soil structural change may be occurring slowly and only be observable over the long term. Copyright © 2016 John Wiley & Sons, Ltd.     

Genetic analysis of landscape connectivity in tree populations

Genetic connectivity in plant populations is determined by gene movement within and among populations. When populations become genetically isolated, they are at risk of loss of genetic diversity that is critical to the long-term survival of populations. Anthropogenic landscape change and habitat fragmentation have become so pervasive that they may threaten the genetic connectivity of many plant species. The theoretical consequences of such changes are generally understood, but it is not immediately apparent how concerned we should be for real organisms, distributed across real landscapes. Our goals here are to describe how one can study gene movement of both pollen and seeds in the context of changing landscapes and to explain what we have learned so far. In the first part, we will cover methods of describing pollen movement and then review evidence for the impact of fragmentation in terms of both the level of pollen flow into populations and the genetic diversity of the resulting progeny. In the second part, we will describe methods for contemporary seed movement, and describe findings about gene flow and genetic diversity resulting from seed movement. Evidence for pollen flow suggests high connectivity, but it appears that seed dispersal into fragments may create genetic bottlenecks due to limited seed sources. Future work should address the interaction of pollen and seed flow and attention needs to be paid to both gene flow and the diversity of the incoming gene pool. Moreover, if future work is to model the impact of changing landscapes on propagule movement, with all of its ensuing consequences for genetic connectivity and demographic processes, we will need an effective integration of population genetics and landscape ecology.     

Effect of historic landscape change on the genetic structure of the bush-cricket Metrioptera roeseli

This study investigates the impact of past and present landscape structure on the current genetic structure of the bush-cricket Metrioptera roeseli (Orthoptera, Tettigoniidae) in a rural landscape in Germany. Assuming that land-use types, such as grassland, arable land and forest, as well as linear structures, mainly roads, differentially affect the connectivity of the bush-cricket's habitat and therefore migration and gene flow, we correlated landscape parameters between sampling locations as derived from GIS-maps with genetic similarities between individual bush-crickets as estimated by RAPD-PCR. Fifty bush-crickets were sampled with distances between sampling locations varying between 15 m and 2 km. Corresponding landscape configurations were recorded in 8 years between 1945 and 1998. Landscape configuration 50 years ago appeared to have influenced the present genetic structure of the bush-cricket (R ² = 0.18). Crossing roads and land use other than grassland along the transect between sampling locations tended to decrease genetic similarity, whereas grassland and parallel roads tended to increase genetic similarity between bush-crickets. Following shifts in land use during 1953–1973 the correlation between landscape and present genetic structure decreased gradually. Our study suggests that it needs time for the landscape to build a visible effect on the genetic structure of the bush-cricket population, and that this effect cannot be detected if the landscape changes faster than the genetic structure responds to it.     

Is landscape connectivity a dependent or independent variable?

With growing interest in landscape connectivity, it is timely to ask what research has been done and what re mains to be done. I surveyed papers investigating landscape connectivity from 1985 to 2000. From these papers, I determined if connectivity had been treated as an independent or dependent variable, what connectivity metrics were used, and if the study took an empirical or modeling approach to studying connectivity. Most studies treated connectivity as an independent variable, despite how little we know about how landscape structure and organism movement behaviour interact to determine landscape connectivity. Structural measures of connectivity were more common than functional measures, particularly if connectivity was treated as an independent variable. Though there was a good balance between modeling and empirical approaches overall – studies dealing with connectivity as a dependent, functional variable were mainly modeling studies. Based on the research achieved thus far, fu ture landscape connectivity research should focus on: (1) elucidating the relationship between landscape struc ture, organism movement behaviour, and landscape connectivity (e.g., treating connectivity as a dependent variable), (2) determining the relationships between different measures of connectivity, particularly structural and functional measures, and (3) empirically testing model predictions regarding landscape connectivity.This revised version was published online in May 2005 with corrections to the Cover Date.     

On the seasonal effect of landscape structure on a bird species: the thorn-tailed rayadito in a relict forest in northern Chile

Forest bird species exhibit noticeable seasonal behavioral changes that might lead to contrasting effects of landscape pattern upon species abundance and performance. We assessed if the effect of patch and habitat attributes on the landscape use of thorn-tailed rayaditos (Aphrastura spinicauda), a forest bird in a relict patchy forest in northern Chile, varied temporally in association with changes in the behavior of individuals linked to breeding vs. non-breeding conditions. We also assessed the relationship between nest success and patch and habitat attributes, as nest success might be associated to the density rayaditos during the breeding season. We found that density of rayaditos was affected by patch size and functional connectivity but not by habitat structure and that the magnitude of the effect of patch size was greater during the non-breeding season, thus supporting the existence of a temporally variable effect of landscape pattern. Similarly, the nest success of rayaditos was positively affected by functional connectivity and negatively by structural connectivity. We hypothesize that these results emerged from the interaction among territorial behavior, resource limitation and predation risk. Despite the variable intensity of the effect of patch size upon density, however, this landscape attribute, in addition to connectivity, is essential for the persistence of rayaditos at this relict patchy forest landscapes.