169,890 research outputs found
Optimizing sampling effort and information content of biodiversity surveys: a case study of alpine grassland
No full textAims: Current rates of biodiversity loss do not allow for inefficient monitoring. Optimized monitoring maximizes the ratio between information and sampling effort (i.e., time and costs). Sampling effort increases with the number and size of sampling units. We hypothesize that an optimal size and number of sampling units can be determined providing maximal information via minimal effort. We apply an approach that identifies the optimal size and number of sampling quadrats. The approach can be adapted to any study system. Here we focus on alpine grassland, a diverse but threatened ecosystem. Location: Gran Paradiso National Park, Italy. Methods: We sampled nine 20 m × 20 m-plots. Each plot consisted of 100 2 m × 2 m-subplots. Species richness and Shannon diversity were quantified for different sizes and quantities of subplots. We simulated larger subplot sizes by unifying adjacent 2 m × 2 m-subplots. Shannon's information entropy was used to quantify information content among richness and diversity values resulting from different subplot sizes and quantities. The optimal size and number of subplots is the lowest size and number of subplots returning maximal information. This optimal subplot size and number was determined by Mood's median test and segmented linear regression, respectively. Results: The information content among richness values increased with subplot size, irrespective of the number of subplots. Therefore, the largest subplot size available is the optimal size for information about richness. Information content among diversity values increased with subplot size if 18 or less subplots were considered, and decreased if at least 27 subplots were sampled. The subplot quantity consequently determined whether the smallest or largest subplot size available is the optimal size, and whether the optimal size can be generalized across richness and diversity. Given a 2 m × 2 m size, we estimated an optimal quantity of 54. Given a size of 4 m × 4 m, we estimated an optimal number of 36. The optimal number of plots can be generalized across both indices because it barely differed between the indices given a fixed subplot size. Conclusions: The information content among richness and diversity values depends on the sampling scale. Shannon's information entropy can be used to identify the optimal number and size of plots that return most information with least sampling effort. Our approach can be adapted to other study systems to create an efficient in-situ sampling design, which improves biodiversity monitoring and conservation under rapid environmental change
Variability of clonal growth of European grass species in climate change experiments.
No full textWe investigate the impact of climate change phenomena such as drought and warming on the clonal growth of European key grass species (Alopecurus pratensis, Arrhenatherum elatius, Festuca pratensis, and Holcus lanatus
Climatic suitability of Aedes albopictus in Europe referring to climate change projections: comparison of mechanistic and correlative niche modelling approaches
No full textThe Asian tiger mosquito, Aedes albopictus, is capable of transmitting a broad range of viruses to humans. Since its introduction at the end of the 20th century, it has become well established in large parts of southern Europe. As future expansion as a result of climate change can be expected, determining the current and projected future climatic suitability of this invasive mosquito in Europe is of interest. Several studies have tried to detect the potential habitats for this species, but differing data sources and modelling approaches must be considered when interpreting the findings. Here, various modelling methodologies are compared with special emphasis on model set-up and study design. Basic approaches and model algorithms for the projection of spatio-temporal trends within the 21st century differ substantially. Applied methods range from mechanistic models (e.g. overlay of climatic constraints based on geographic information systems or rather process-based approaches) to correlative niche models. We conclude that spatial characteristics such as introduction gateways and dispersal pathways need to be considered. Laboratory experiments addressing the climatic constraints of the mosquito are required for improved modelling results. However, the main source of uncertainty remains the insufficient knowledge about the species ́ ability to adapt to novel environment
Differences in gene expression of drought-stress candidate genes across natural populations of Quercus pubescens Willd. in Italy. IUFRO 2012 Genetics of Fagaceae and Nothofagaceae. Poster abstracts. Bordeaux.
No full textUnderstanding plant species acclimation and adaptation to climatic changes is one of the
most interesting challenges at the interface of ecology, physiology and genetics. In this
context, the investigation of functional genetic diversity related to stress tolerance of natural
populations in a contrasting climatic context is a promising approach. Plant responses to
drought stress are complex, involving a number of genes which contribute to drought
adaptation.
Here we use 30 candidate genes involved in drought-stress response in Q. robur (Brendel,
Kremer, Le Provost, pers. com.). These candidate genes are involved in processes such as
transpiration regulation, stomatal development, stomatal light response, cuticle biosynthesis,
and water use efficiency. We tested for differential gene expression in natural populations of
Quercus pubescens Willd. at mesic and xeric sites in Central and Southern Italy. For this
purpose, RNA was extracted from leaf material of 100 individuals. We aimed to identify
markers for climatic acclimation and adaptation of natural populations.
Results of SIMPER analysis for dissimilarity revealed that four out of 30 candidate genes
appear as main factors which differentiate the samples. In detail, significant differences in
gene expression were most obvious between the most mesic (central Italy) compared to the
most xeric (S Italy) site.
It will be a challenge for future research to tackle if these markers reappear in the droughtstress
response in other tree species or plants in general
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The concept of potential natural vegetation: an epitaph?
No full textWe discuss the usefulness of the concept of Potential Natural Vegetation (PNV), which describes the expected state of mature vegetation in the absence of human intervention. We argue that it is impossible to model PNV because of (i) the methodological problems associated to its definition and (ii) the issues related to the ecosystems dynamics.We conclude that the approach to characterizing PNV is unrealistic and provides scenarios with limited predictive power. In places with a long-term human history, interpretations of PNV need to be very cautious, and explicit acknowledgement made of the limitations inherent in available data
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Data on alpine grassland diversity in Gran Paradiso National Park, Italy
No full textThe diversity of alpine grassland species and their functional traits constitute alpine ecosystem functioning and services that support human-wellbeing. However, alpine grassland diversity is threatened by land use and climate change. Field surveys and monitoring are necessary to understand and preserve such endangered ecosystems. Here we describe data on abundances (percentage cover) of 247 alpine plant species (including mosses and lichens) inside nine 20 m by 20 m plots that were subdivided into 2 m by 2 m subplots. The nine plots are located in Gran Paradiso National Park, Italy. They cover three distinct alpine vegetation subtypes (‘pure’ natural grassland, sparsely vegetated ‘rocky’ grassland, and wetland) in each of three valleys (Bardoney, Colle de Nivolet and Levionaz) between 2200 and 2700 m a.s.l., i.e. above the treeline. The vegetation survey was conducted in 2015 at the peak of vegetation development during August. The dataset is provided as supplementary material and associated with the research article “Optimizing sampling effort and information content of biodiversity surveys: a case study of alpine grassland” [1]. See [1] for data interpretation
Murgia Alta: Ailantus altissima invasive species presence map (2012)
No full textAn Ailanthus altissima invasive species presence map in "Murgia Alta" PA, for 2012, obtained by a two stage algorithm [1]. The first stage considers the deciduous vegetation layer obtained by a multiclass knowledge-based classification of 4 multi-seasonal VHR Worldview-2 images. In the second stage an SVM classifier was used to detect, in a two-classes problem, the Ailanthus invasive species within the deciduous layer vegetation boundaries overimposed on 2 VHR Worldview-2 images. The Worldview-2 images were dated May 19th, 2011, October 10th, 2011, January 22th, 2012 and July 6th, 2012. The October and July images were considered in the second stage.
The map was produced at 2 meters spatial resolution and projected in WGS84/UTM33N.
The map has binary values where value 1 indicates Ailanthus altissima pixels whereas value 0 indicates No Ailanthus altissima.
The Overall Accuracy (OA) of the map was: OA=97.96%±0.14%.
[1] C. Tarantino, F. Casella, M. Adamo, R. Lucas, C. Beierkuhnlein, P. Blonda. (2018). “Ailanthus altissima mapping from multi-temporal very high resolution satellite images”, ISPRS Journal of Photogrammetry and Remote Sensing, 147, 90-103, https://doi.org/10.1016/j.isprsjprs.2018.11.01
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