130,943 research outputs found
Coomes, D. A., Burslem, D. F. R. P. & Simonson, W. D. (eds).— Forests and global change. Ecological Reviews, Cambridge University Press, Cambridge & New York, 2014
No full textErard Christian. Coomes, D. A., Burslem, D. F. R. P. & Simonson, W. D. (eds).— Forests and global change. Ecological Reviews, Cambridge University Press, Cambridge & New York, 2014. In: Revue d'Écologie (La Terre et La Vie), tome 70, n°1, 2015. pp. 92-93
Assessing the impacts of fragmentation on plant communities in New Zealand: scaling from survey plots to landscapes
No full textAim Few studies have attempted to assess the overall impact of fragmentation at the landscape scale. We quantify the impacts of fragmentation on plant diversity by assessing patterns of community composition in relation to a range of fragmentation measures.
Location The investigation was undertaken in two regions of New Zealand – a relatively unfragmented area of lowland rain forest in south Westland and a highly fragmented montane forest on the eastern slopes of the Southern Alps.
Methods We calculated an index of community similarity (Bray–Curtis) between forest plots we regarded as potentially affected by fragmentation and control forest plots located deep inside continuous forest areas. Using a multiple nonlinear regression technique that incorporates spatial autocorrelation effects, we analysed plant community composition in relation to measures of fragmentation at the patch and landscape levels. From the resulting regression equation, we predicted community composition for every forest pixel on land-cover maps of the study areas and used these maps to calculate a landscape-level estimate of compositional change, which we term ‘BioFrag’. BioFrag has a value of one if fragmentation has no detectable effect on communities within a landscape, and tends towards zero if fragmentation has a strong effect.
Results We detected a weak, but significant, impact of fragmentation metrics operating at both the patch and landscape levels. Observed values of BioFrag ranged from 0.68 to 0.90, suggesting that patterns of fragmentation have medium to weak impacts on forest plant communities in New Zealand. BioFrag values varied in meaningful ways among landscapes and between the ground-cover and tree and shrub communities.
Main conclusions BioFrag advances methods that describe spatial patterns of forest cover by incorporating the exact spatial patterns of observed species responses to fragmentation operating at multiple spatial scales. BioFrag can be applied to any landscape and ecological community across the globe and represents a significant step towards developing a biologically relevant, landscape-scale index of habitat fragmentation
Airborne laser scanning of New Zealand reveals the influences of wind on forest carbon
No full textBackground: Forests are a key component of the global carbon cycle, and research is needed into the effects of
human-driven and natural processes on their carbon pools. Airborne laser scanning (ALS) produces detailed 3D maps
of forest canopy structure from which aboveground carbon density can be estimated. Working with a ALS dataset
collected over the 8049-km2 Wellington Region of New Zealand we create maps of indigenous forest carbon and
evaluate the influence of wind by examining how carbon storage varies with aspect. Storms flowing from the west are
a common cause of disturbance in this region, and we hypothesised that west-facing forests exposed to these winds
would be shorter than those in sheltered east-facing sites.
Methods: The aboveground carbon density of 31 forest inventory plots located within the ALS survey region were
used to develop estimation models relating carbon density to ALS information. Power-law models using rasters of
top-of-the-canopy height were compared with models using tree-level information extracted from the ALS dataset. A
forest carbon map with spatial resolution of 25 m was generated from ALS maps of forest height and the estimation
models. The map was used to evaluate the influences of wind on forests.
Results: Power-law models were slightly less accurate than tree-centric models (RMSE 35% vs 32%) but were
selected for map generation for computational efficiency. The carbon map comprised 4.5 million natural forest pixels
within which canopy height had been measured by ALS, providing an unprecedented dataset with which to examine
drivers of carbon density. Forests facing in the direction of westerly storms stored less carbon, as hypothesised. They
had much greater above-ground carbon density for a given height than any of 14 tropical forests previously analysed
by the same approach, and had exceptionally high basal areas for their height. We speculate that strong winds have
kept forests short without impeding basal area growth.
Conclusion: Simple estimation models based on top-of-the canopy height are almost as accurate as state-of-the-art
tree-centric approaches, which require more computing power. High-resolution carbon maps produced by ALS
provide powerful datasets for evaluating the environmental drivers of forest structure, such as wind
Canopy spectral responses of temperate forests to late spring frost and hot drought events assessed with Sentinel-2 NDVI time series
No full textExtreme climatic events (ECEs) are projected to increase due to climate change, but we still have limited understanding of how these events affect the functioning of forest ecosystems. Each species may react differently to ECEs, depending on their ecology, but we lack a regional perspective on these responses. Here we tracked intra-annual changes in the canopy greenness (i.e. NDVI from Sentinel-2 imagery) of 16 tree species growing within 3000 km2 of forests of the Italian Alps. The study region was subject to a late spring frost event in May 2019, and a hot drought in July 2022, allowing us to quantify species responses to ECEs by comparison of seasonal trends in NDVI observed over the period 2018–2024. The effects of 2019 frost were very localized and mainly affected the canopy spectral response and phenology of Fagus sylvatica L. in areas around 1000 m a.s.l.. There, trees had developed buds and some juvenile leaves when frost occurred, resulting in the wilting or dropping of the earliest leaves, and slower green-up phase but no lasting impacts. The hot drought had its largest impact on Quercus ilex L. forests growing at low elevations: there was a clear decrease in canopy greenness from July onwards in 2022, but no residual impacts were observed the following years. At higher elevations, some species had unusually green canopies in response to the heatwave suggesting they benefitted from warmer condition
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
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
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Scholarly Communication and Publishing Lunch and Learn Talk #11: The ULS Open Access Author Fee Fund
No full textAt the May 2014 talk, you will learn about the ULS Open Access Author Fee Fund--what it is, why we do it, how it works, and how the program is going so far
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