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Spiders contribute essentially to the arthropod community of forests and are known to be distributed in non-random pattern according to environmental, structural, competitive, and predacious conditions. The aim of the study was to investigate the effects of the distance to trees on the distribution pattern of soil-dwelling spiders. We verified the hypothesis that stem-close and stem-distant microhabitats differ with respect to taxonomical and ecological characteristics of spider assemblages, hence, functional significance on a small spatial scale. Ground-dwelling spiders were collected with pitfall traps in positions close (20–30 cm) and distant (2 m) to the stem bases in mature forests of different stand types (spruce, Douglas fir, beech-spruce, oak-beech). To identify significant drivers of spider assemblage composition, environmental parameters were assessed in relation with the arrangement of pitfall traps. The study documented significant variability in the composition of spider assemblages of stem-close and stem-distant pitfall traps within each of the study sites. The position of traps strongly affected species richness, species composition, activity density, and dominance structure. Thus, sampling at both positions revealed that the species richness of spiders is spatially restricted. Moreover, spider assemblage structure differed in the classification of species to size and ecological preference. Those results implicate potential consequences for their functional role in forests in relation to the distance to the trees.
Community ecologists have become increasingly interested in analyzing the phylogenetic diversity of species assemblages. Species that co-occur in the same habitats often share a common phylogenetic history such that at coarse spatial scales a species assemblage with a locally clustered phylogenetic structure is usually associated with the presence of habitat filtering mechanisms. However, more recently it has been hypothesized that environmental filters act primarily on the relative abundance of species rather than on their simple presences and absences, reducing the species’ probabilities to persist in given environmental conditions. This process may produce a non-random distribution of species abundances in the regional phylogeny even in the absence of a locally clustered phylogenetic structure. In this paper, using data from the urban flora of Brussels (Belgium) we tested for the presence of non-randomness in the distribution of abundances among the species phylogenetic structure. We argue that the observed pattern of low species phylogenetic distinctiveness at increasing species abundances is compatible with environmental filtering processes.
Ad hoc decisions during fieldwork reduce the accuracy and reliability of vegetation maps. A method is proposed to objectify vegetation (thematic aspects) mapping (spatial aspects) for monitoring (temporal aspects). The most accurate and reliable description of the vegetation is a list of all plant species found within a plot. Therefore, the proposed method is an interpolation of a spatially representative sample of permanent plots combined with aerial photo interpretation. The method is objective because surveyors do not have to make decisions during fieldwork based on their personal judgement. Moreover, it is flexible, because the classification and interpolation methods can be adapted to specific views or needs depending on the aim of a study. The method was applied to an area in the north of the Netherlands in 1998. A sampling design with a density of 1 plot/ha was used, and interpolated with a perpendicular bisector. In 2002, the number of plots/ha was doubled. The influence of sample density on the mapping results was studied because it is an important decision to be made before fieldwork. Two plots/ha seem to be sufficient in order to obtain reliable information on patterns of plant species composition and vegetation types of the area, and their change over time. However, in patches where vegetation varies on a very small spatial scale this plot density was insufficient.
Abstract
Two complimentary spectroscopic techniques, X-ray absorption and fluorescence spectroscopy have been conducted at spatial scales of 1 to 25 μm on uranium contaminated soil sediments collected from two former nuclear materials processing facilities of the DOE: Fernald, OH and Savannah River Site, SC. A method of imbedding particles in a non-reactive Si polymer was developed such that individual particles could be examined before and after extraction with a wide range of chemicals typically used in sequential extraction techniques and others proposed forex situ chemical intervention technologies. Using both the micro-X-ray fluorescence (XRF) and micro-X-ray Absorption Near Edge Structure (XANES) techniques, both elemental and oxidation state distribution maps were generated on individual particles before and following chemical extraction. XANES can determine the relative proportion of U(VI) and U(IV) in phases comprising individual particles before and after extraction and showed that greater than 85% of the uranium existed as hexavalent U(VI). Fluorescence spectra of contaminated particles containing mainly U(VI) revealed populations of uranyl hydroxide phases and demonstrated the relative efficacy and specificity of each extraction method. Correlation of XAS and fluorescence data at micron scales provides information of U oxidation state as well as chemical form in heterogeneous samples.
In this paper we present an implementation of the natural capital index (NCI), a highly aggregated policy-relevant biodiversity indicator for Hungary, based on the MÉTA database, a detailed field-based vegetation database with a habitat quality attribute. To this end, we introduce two different weighting schemes for the field-estimated MÉTA values, both rooted in the concept of ecosystem services: a linear “equal steps” (NCI lin ) and an exponential (NCI exp ) weighting scheme. The natural capital index of Hungary and its physical geographical regions are calculated and presented from both aspects. The national NCI lin is 9.9% (indicating an overall 90% loss in the availability of the major supporting ecosystem services), and NCI exp is 3.2% (indicating an even greater degree of loss in terms of the conservation of rare species). The geographical regions of Hungary exhibit considerable spatial variation, which reveals important information on their basic characteristics (e.g. agricultural potential) and land use history. As NCI can be calculated on any spatial scales from local to national, this indicator may become a useful tool for policy development and evaluation purposes, including environmental impact assessments (EIA) and strategic environmental assessments (SEI). However, due to several conceptual limitations (e.g. disregard for rarity, spatial structure and cultural values, questions of recency and repetition) NCI should not be regarded as a self-sufficient universal tool, and strategic decisions should be based on careful consideration of all potentially relevant factors.
We review the population ecology of Allium ursinum according to its life history, phenology, demography, dispersal, and population dynamics. Spatial distribution is reviewed on two spatial scales. First, on a broad scale over Europe, in relation to the habitat requirement of the species. Second, on a fine scale of individual patches, presenting some results about the local processes of density regulation and patch formation. We conclude that A. ursinum has a distinct, hitherto non-described, strategy for monopolizing space and dominating the forest floor. This Clan-of-Clones strategy has the following attributes. 1) Most of the seeds are dispersed close to the parent. 2) Seedling establishment is facilitated by the surrounding adults. 3) Allocation to vegetative reproduction is relatively small; its main role is to prolong local persistence. 4) The genet is not integrated physiologically, except for a transient connection between parent and offspring. An important consequence of the Clan-of-Clones strategy is that occupied patches can be fine-grained mosaics in terms of genetic composition and age groups.
Abstract
Terrestrial ecosystems across the world experience large-scale and widespread urbanization, causing a sharp decline, fragmentation and segregation of natural landscapes. Nevertheless, fragments of natural habitats that are found within the largest cities may still be capable of preserving high species diversity that amount to a large portion of the regional biodiversity. Knowing which variables of the urban landscape promote the conservation of species' assemblages in large cities helps us to implement measures that support biodiversity conservation. We sampled the butterfly assemblages of eight urban forest fragments in Curitiba (Southern Brazil), from September 2015 to April 2016. At each site, richness, diversity and composition of butterflies were estimated and then correlated to nine landscape variables measured at two spatial scales (buffers of 250 and 750m). A total of 298 species were recorded in these fragments, representing 53.7% of all species known to occur in the city. Despite of great difference in the size of the fragments (between 27 and 56.3 ha), there were no significant differences in species richness among the fragments. On the other hand, some significant correlations were observed between landscape variables and butterfly composition other than the fragment itself, such as the paved area and total forested area present around the fragments. These results reinforce the idea that the conservation of natural fragments in urban areas requires public policies that enhance not only the habitat quality of the fragment itself, but also enrichment of the landscape around them.
The on-going Biodiversity Monitoring in Switzerland Programme (BDM) has monitored vascular-plant species richness since 2001. This long-term programme focuses on two indicators at different spatial scales. First, the local diversity indicator monitors changes of species richness within habitats or types of land use (within-habitat diversity). Second, the landscape diversity indicator is utilized to describe landscape diversity (i.e., within-habitat mosaic diversity). Here we examine if the reproducibility of the BDM methods is sufficiently precise to detect future changes in species richness. We demonstrate that systematic methodical errors are negligible. Random errors that make changes more difficult to detect are also small. We calculate the Minimum Detectable Difference (MDD) for selected BDM strata using the variance of measured values. Then we deduce the MDD values for paired samples using data from grasslands and forests in the Canton Argovia. With 2.4 and 1.6 species they are promisingly precise. We develop a simple scenario for possible changes in species richness and show that they surpass the deduced MDD values by a factor four to six. We conclude that the BDM methods are appropriate for detecting future changes in species richness.
, J.M. and M.A. Leibold. 2002. Spatial scale dictates the productivity-biodiversity relationship. Nature 416:427-430. Spatial scale dictates the productivity-biodiversity relationship Nature
Invasion by alien plant species may be rapid and aggressive, causing erosion of local biodiversity. This is particularly true for islands, where natural and anthropogenic corridors promote the rapid spread of invasive plants. Although evidence shows that corridors may facilitate plant invasions, the question of how their importance in the spread of alien species varies along environmental gradients deserves more attention. Here, we addressed this issue by examining diversity patterns (species richness of endemic, native and alien species) along and across roads, along an elevation gradient from sea-level up to 2050 m a.s.l. in Tenerife (Canary Islands, Spain), at multiple spatial scales. Species richness was assessed using a multi-scale sampling design consisting of 59 T-transects of 150 m × 2 m, along three major roads each placed over the whole elevation gradient. Each transect was composed of three sections of five plots each: Section 1 was located on the road edges, Section 2 at intermediate distance, and Section 3 far from the road edge, the latter representing the “native community” less affected by road-specific disturbance. The effect of elevation and distance from roadsides was evaluated for the three groups of species (endemic, native and alien species), using parametric and non-parametric regression analyses as well as additive diversity partitioning. Differences among roads explained the majority of the variation in alien species richness and composition. Patterns in alien species richness were also affected by elevation, with a decline in richness with increasing elevation and no alien species recorded at high elevations. Elevation was the most important factor determining patterns in endemic and native species. These findings confirm that climate filtering reflected in varying patterns along elevational gradients is an important determinant of the richness of alien species (which are not adapted to high elevations), while anthropogenic pressures may explain the richness of alien species at low elevation.
