Search results for "Richness"
showing 10 items of 447 documents
Risk factors for Lyme disease : A scale-dependent effect of host species diversity and a consistent negative effect of host phylogenetic diversity
2021
Biodiversity can influence disease risk. One example of a diversity-disease relationship is the dilution effect, which suggests higher host species diversity (often indexed by species richness) reduces disease risk. While numerous studies support the dilution effect, its generality remains controversial. Most studies of diversity-disease relationships have overlooked the potential importance of phylogenetic diversity. Furthermore, most studies have tested diversity-disease relationships at one spatial scale, even though such relationships are likely scale dependent. Using Lyme disease as a model system, we investigated the effects of host species richness and phylogenetic relatedness on the…
Effects of Canopy Gap Disturbance on Forest Birds in Boreal Forests
2013
We studied the effects of small-scale disturbance on breeding, forest passerine birds in an old-growth and managed boreal forests in northern Finland. Small-scale disturbance (< 2 ha) in an old-growth and managed forests originated from wind falls and small clear cuts. Continuous forest without gaps was used as a control for both management types (old-growth and managed forests). Passerines' response to disturbance was examined by estimating species richness and abundance of different ecological groups. Species richness and the total abundance of birds did not differ between gap and non-gap plots, neither did the abundance of most ecological groups. Management type or study year were the mo…
Plankton biodiversity in a landscape of shallow water bodies (Mediterranean coast, Spain)
2003
A large spatial heterogeneity was detected in La Safor, a coastal area with different kinds of small and shallow water bodies. The area exhibits a sharp gradient in eutrophication (0.004–20 mgP l−1; 0.6–457 μg Chl a l−1) and varied water body features (morphology: size, depth; hydrology; vegetation, etc.). These factors result in a high diversity of aquatic habitats within the area. One hundred and twenty eight species of microalgae were identified in the 32 sampling stations studied (in the wet and dry periods). The phytoplankton richness varied between 1 and 21 species, the Shannon-Wiener index range was 0–3 bits, the index of floral originality (IFO) range was 0.1 – 0.6. A total number o…
Tardigrades of Finland: new records and an annotated checklist
2020
Species checklists are powerful and important tools of communication between taxonomists and applied environmental biologists, which in turn lead to well-planned and successful conservation strategies and ecological studies. Despite this, only recently the interest on compiling systematic checklists is growing among taxonomists who study tardigrades—micrometazoans that inhabit almost every habitat worldwide. As the Finnish records of tardigrades (a.k.a. water bears) species are incomplete, outdated and no checklist has ever been compiled for this country, an easy-to-consult checklist is here reported. This checklist covers all Finnish tardigrade taxa identified in the past and in the 13 sam…
Fuzzy Quantification of Common and Rare Species in Ecological Communities (FuzzyQ)
2020
Abstract1. Most species in ecological communities are rare whereas only a few are common. This distributional paradox has intrigued ecologists for decades but the interpretation of species abundance distributions remains elusive.2. We present Fuzzy Quantification of Common and Rare Species in Ecological Communities (FuzzyQ) as an R package. FuzzyQ shifts the focus from the prevailing species-categorization approach to develop a quantitative framework that seeks to place each species along a rare-commonness gradient. Given a community surveyed over a number of sites, quadrats, or any other convenient sampling unit, FuzzyQ uses a fuzzy clustering algorithm that estimates a probability for eac…
Resources, recruitment limitation and invader species identity determine pattern of spontaneous invasion in experimental grasslands
2009
Summary 1 A number of experimental studies have supported the hypothesis that diversity increases invasion resistance, but several mechanisms were proposed to explain this relationship. We studied spontaneous invasion in experimental grasslands varying in species richness (1–16 (60)) and plant functional group richness and identity (1–4; grasses, legumes, tall herbs small herbs) during the first 3 years after establishment on large-area plots of 20 × 20 m size. 2 Invader species number, biomass and density decreased with increasing community species richness. The identity of successful invaders changed through time as the relative importance of external invaders (= species not belonging to …
Changes in community composition determine recovery trajectories from multiple agricultural stressors in freshwater ecosystems
2020
AbstractPesticides have been identified worldwide as a threat for aquatic biodiversity due to their widespread use in agriculture and their capacity to reach freshwater ecosystems. Very little is known about the consequences of pesticide mixtures targeting different organism groups on community dynamics. Especially, how horizontal changes within one trophic level are propagated vertically across the food web has been rarely investigated. To get insight on the effects of pesticide mixtures on community dynamics, we performed a mesocosm experiment manipulating three common agricultural stressors: chlorpyrifos (an insecticide), diuron (an herbicide) and nutrients. The results of this study sho…
Effects of hard frost and freeze-thaw cycles on decomposer communities and N mineralisation in boreal forest soil
2003
Abstract Decomposition and mineralisation rates generally increase with increasing moisture and temperature. The expected global climate change may enhance precipitation and raise the temperatures at boreal latitudes, but absence of snow together with occasional low temperatures may cause disturbances in soil processes and faunal communities. To test the effects of disturbances such as hard frosts and freeze-thaw cycles on decomposer populations and N mineralisation, we performed two experiments. In the field experiment, carried out in a pine forest, we induced low soil temperatures by preventing snow covering the ground. In the laboratory test we established three “winter” temperature regi…
Woody plants and the prediction of climate-change impacts on bird diversity.
2010
Current methods of assessing climate-induced shifts of species distributions rarely account for species interactions and usually ignore potential differences in response times of interacting taxa to climate change. Here, we used species-richness data from 1005 breeding bird and 1417 woody plant species in Kenya and employed model-averaged coefficients from regression models and median climatic forecasts assembled across 15 climate-change scenarios to predict bird species richness under climate change. Forecasts assuming an instantaneous response of woody plants and birds to climate change suggested increases in future bird species richness across most of Kenya whereas forecasts assuming str…
Energy density and its variation in space limit species richness of boreal forest birds
2012
Aim An area’s ability to support species may be dependent not only on the total amount of available energy it contains but also on energy density (i.e. available energy per unit area). Acknowledging these two aspects of energy availability may increase mechanistic understanding of how increased energy availability results in increased species richness. We studied the relationship between energy density, its variation in space and boreal forest bird species richness and investigated two possible mechanisms: (1) metabolic constraints of organisms, and (2) increased resource availability for specialists. Location Protected areas in Finland’s boreal forest. Methods We tested whether bird spe…