Search results for "SYSTEMATICS"
showing 10 items of 6702 documents
Environmental determinants of chironomid communities in remote northern lakes across the treeline – Implications for climate change assessments
2016
Abstract Chironomids ( Diptera : Chironomidae ) in northern lakes are especially sensitive to climate change impacts. In addition, environmental factors other than direct temperature increase might play an important role in functioning of these keystone aquatic communities. We examined 31 lakes at the treeline ecotone in subarctic Finnish Lapland for their surface sediment chironomid fauna to assess the influence of different environmental factors on the communities. We aim to improve understanding of the climate-driven catchment and limnological factors, for the assessment of climate change impacts. Our results indicated that organic content of the sediment, total nitrogen, water depth and…
Understanding the uncertainty in global forest carbon turnover
2020
Abstract. The length of time that carbon remains in forest biomass is one of the largest uncertainties in the global carbon cycle, with both recent historical baselines and future responses to environmental change poorly constrained by available observations. In the absence of large-scale observations, models used for global assessments tend to fall back on simplified assumptions of the turnover rates of biomass and soil carbon pools. In this study, the biomass carbon turnover times calculated by an ensemble of contemporary terrestrial biosphere models (TBMs) are analysed to assess their current capability to accurately estimate biomass carbon turnover times in forests and how these times a…
An invasive species, Carassius gibelio, alters the native fish community through trophic niche competition
2019
Carbon and nitrogen stable isotope analyses were used to determine isotopic niche width of the invasive fish species Carassius gibelio to help assess the niche overlap and potential impact of this species on the native fish fauna in the Karamenderes River, northwest Turkey. C. gibelio had the highest niche area of the coexisting species. The greatest overlap of isotopic niche was between C. gibelio and Mugil cephalus in the river mouth. The freshwater species displayed similar patterns when taking into consideration their relative abundance and isotopic overlap. While C. gibelio is likely to outcompete some species at some localities, the species was found co-occurring with others by maximu…
Continuous cover forestry is a cost-efficient tool to increase multifunctionality of boreal production forests in Fennoscandia
2017
Abstract Earlier research has suggested that the diversification of silvicultural strategies is a cost-efficient tool to ensure multifunctionality in production forests. This study compared the effects of continuous cover forestry and conventional rotation forestry on ecosystem services and biodiversity in boreal forests in Finland. We simulated over 25,000 commercial forest stands for 100 years under continuous cover and rotation forest management. Forests without management were used as a reference. We compared the effects of silvicultural practices over space and time on ecosystem services, biodiversity indicators and multifunctionality. Our results revealed that continuous cover forestr…
Early Diagnosis of Vegetation Health From High-Resolution Hyperspectral and Thermal Imagery: Lessons Learned From Empirical Relationships and Radiati…
2019
[Purpose of Review] We provide a comprehensive review of the empirical and modelling approaches used to quantify the radiation–vegetation interactions related to vegetation temperature, leaf optical properties linked to pigment absorption and chlorophyll fluorescence emission, and of their capability to monitor vegetation health. Part 1 provides an overview of the main physiological indicators (PIs) applied in remote sensing to detect alterations in plant functioning linked to vegetation diseases and decline processes. Part 2 reviews the recent advances in the development of quantitative methods to assess PI through hyperspectral and thermal images.
Change in dominance determines herbivore effects on plant biodiversity
2018
Herbivores alter plant biodiversity (species richness) in many of the world’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis—that herbivore-induced changes in the competitive environment determine the response …
Stochastic models for phytoplankton dynamics in Mediterranean Sea
2016
Abstract In this paper, we review some results obtained from three one-dimensional stochastic models, which were used to analyze picophytoplankton dynamics in two sites of the Mediterranean Sea. Firstly, we present a stochastic advection–reaction–diffusion model to describe the vertical spatial distribution of picoeukaryotes in a site of the Sicily Channel. The second model, which is an extended version of the first one, is used to obtain the vertical stationary profiles of two groups of picophytoplankton, i.e. Pelagophytes and Prochlorococcus, in the same marine site as in the previous case. Here, we include intraspecific competition of picophytoplanktonic groups for limiting factors, i.e.…
Coastal Oceanic climate change and variability from 1982 to 2009 around South Africa
2010
Changes and fluctuations in sea surface temperature (SST) around the South African coast are analysed at a monthly scale from 1982 to 2009. There is a statistically significant negative trend of up to 0.5 °C per decade in the southern Benguela from January to August, and a cooling trend of lesser magnitude along the South Coast and in the Port Elizabeth/Port Alfred region from May to August. The cooling is due to an increase in upwelling-favourable south-easterly and easterly winds. There is a positive trend in SST of up to 0.55 °C per decade in most parts of the Agulhas Current system during all months of the year, except for KwaZulu-Natal where warming is in summer. The warming was attri…
Oxygen respiration rates of benthic foraminifera as measured with oxygen microsensors
2011
Abstract Oxygen respiration rates of benthic foraminifera are still badly known, mainly because they are difficult to measure. Oxygen respiration rates of seventeen species of benthic foraminifera were measured using microelectrodes and calculated on the basis of the oxygen fluxes measured in the vicinity of the foraminiferal specimens. The results show a wide range of oxygen respiration rates for the different species (from 0.09 to 5.27 nl cell−1 h−1) and a clear correlation with foraminiferal biovolume showed by the power law relationship: R = 3.98 10−3 BioVol0.88 where the oxygen respiration rate (R) is expressed in nl O2 h−1 and in μm3 biovolume (BioVol) (n = 44, R2 = 0.72, F = 114, p
Insights from sodium into the impacts of elevated pCO2 and temperature on bivalve shell formation
2017
Ocean acidification and warming are predicted to affect the ability of marine bivalves to build their shells, but little is known about the underlying mechanisms. Shell formation is an extremely complex process requiring a detailed understanding of biomineralization processes. Sodium incorporation into the shells would increase if bivalves rely on the exchange of Na+/H+ to maintain homeostasis for shell formation, thereby shedding new light on the acid-base and ionic regulation at the calcifying front. Here, we investigated the combined effects of seawater pH (8.1, 7.7 and 7.4) and temperature (16 and 22 °C) on the growth and sodium composition of the shells of the blue mussel, Mytilus edul…