Search results for "Species richnes"

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…

Size matters in studies of dead wood and wood-inhabiting fungi

2011

Abstract Because biased biodiversity surveys may result in ineffective use of conservation or research resources it is important that measures for biodiversity are accurate. In forest ecosystems wood-inhabiting fungi are an ecologically important species group. We addressed the question whether or not the traditional methodology to survey only coarse woody debris provides accurate estimates of the assemblages of wood-inhabiting fungi or the dead wood itself. In this study, we included all dead wood pieces irrespective of the diameter. Our results showed that the chosen minimum size of studied dead wood pieces has crucial importance for species recordings of wood-inhabiting fungi and for rec…

Quantifying the Indicator Power of an Indicator Species

2009

Biodiversity indicator species are needed for classifying biotopes and sites for conservation, and a number of methods have been developed for determining indicator species for this purpose. Nevertheless, in addition to site classification, there is sometimes a need to define an indicator species that indicates the occurrence of another species. For example, when a species of interest (target species) is difficult to detect or identify, a reliable indicator species can function as a tool that saves time and money. We derived a method that provides a quantitative measure of the indicator power (IP) of an indicator species for the target species or any species assemblage. We calculated the me…

Effects of Local Disturbance of Tropical Forests on Frugivores and Seed Removal of a Small-Seeded Afrotropical Tree

2008

Small-scale, local disturbance of tropical forests, for example from selective logging, is widespread, but its effects on biodiversity and ecosystem function have rarely been studied. In 3 East African tropical rainforests, we investigated the effect of different levels of local forest disturbance on the frugivore community and on tree visitation and fruit removal rates of the small-seeded tree Celtis durandii. We quantified birds and primates in little and heavily disturbed sites, distinguishing between forest specialists, forest generalists, and forest visitors. We quantified frugivorous tree visitors and seed removal rates of C. durandii trees in the same sites. Forest disturbance reduce…

2015

Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the extent and determinants of such coupling remains a topical area of ecological research and is largely unknown in oligotrophic high-latitude lakes. We analyzed food-web structure and resource use by a generalist top predator, the Arctic charr Salvelinus alpinus (L.), in 17 oligotrophic subarctic lakes…

How livestock grazing affects vegetation structures and small mammal distribution in the semi-arid Karoo

2000

In this study we investigated vegetation changes superimposed by grazing and their effect on small mammals in the Karoo (South Africa) on grazed farmland and an adjacent, 10-year livestock enclosure. Plains and drainage line habitats were compared by monitoring vegetation height and cover, and small mammal species composition and abundance along transects. Animals were captured by live trapping. Vegetation cover was low on the grazed compared to the ungrazed study site, but vegetation height did not differ. The number of small mammal individuals and the number of species captured was higher at the ungrazed study site. Two species of climbing rodents captured in the ungrazed drainage line we…

Mapping floristic diversity: a case study in Sicily

2021

This paper presents an operational methodology to map and analyze the floristic richness of “target species” in Natura 2000 sites, making use of G.I.S. tools and procedures. A Floristic diversity map (scale 1:50,000), covering an area of 612 km2, was produced by a team of experts as part of the management plans of “Madonie Mountains” Sites of Community Importance (SCIs), located in Sicily (Italy). The primary grid map represents the richness of “target species”, which include species of Community interests, taxa on the National Red List, endemic and threatened, species protected under International Conventions, taxa of phytogeographic importance. Secondary data frames include a three-dimens…