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521.
The use of species distribution models (SDMs) to predict potential distributions of species is steadily increasing. A necessary
assumption when projecting models throughout space or time is that climatic niches are conservative, but recent findings of
niche shifts during biological invasion of particular plant and animal species have indicated that this assumption is not
categorically valid. One reason for observed shifts may relate to variable selection for modelling. In this study, we assess
differences in climatic niches in the native and invasive ranges of the Greenhouse frog (Eleutherodactylus planirostris). We analyze which variables are more ‘conserved’ in comparison to more ‘relaxed’ variables (i.e. subject to niche shift)
and how they influence transferability of SDMs developed with Maxent on the basis of ten bioclimatic layers best describing
the climatic requirements of the target species. We focus on degrees of niche similarity and conservatism using Schoener's
index and Hellinger distance. Significance of results are tested with null models. Results indicate that the degrees of niche
similarity and conservatism vary greatly among the predictive variables. Some shifts can be attributed to active habitat selection,
whereas others apparently reflect variation in the availability of climate conditions or biotic interactions between the frogs'
native and invasive ranges. Patterns suggesting active habitat selection also vary among variables. Our findings evoke considerable
implications on the transferability of SDMs over space and time, which is strongly affected by the choice and number of predictors.
The incorporation of ‘relaxed’ predictors not or only indirectly correlated with biologically meaningful predictors may lead
to erroneous predictions when projecting SDMs. We recommend thorough assessments of invasive species' ecology for the identification
biologically meaningful predictors facilitating transferability. 相似文献
522.
Xiaoliang Wang Curtis Robbins S. Kent Hoekman Judith C. Chow John G. Watson Dennis Schuetzle 《Frontiers of Environmental Science & Engineering in China》2011,5(3):320-330
Thermochemical biomass gasification, followed by conversion of the produced syngas to fuels and electrical power, is a promising
energy alternative. Real-world characterization of particulate matter (PM) and other contaminants in the syngas is important
to minimize damage and ensure efficient operation of the engines it powers and the fuels created from it. A dilution sampling
system is demonstrated to quantify PM in syngas generated from two gasification plants utilizing different biomass feedstocks:
a BioMax?15 Biopower System that uses raw and torrefied woodchips as feedstocks, and an integrated biorefinery (IBR) that
uses rice hulls and woodchips as feedstocks. PM2.5 mass concentrations in syngas from the IBR downstream of the purification system were 12.8–13.7 μg·m−3, which were significantly lower than the maximum level for catalyst protection (500 μg·m−3) and were 2–3 orders of magnitude lower than those in BioMax?15 syngas (2247–4835 μg·m−3). Ultrafine particle number concentration and PM2.5 chemical constituents were also much lower in the IBR syngas than in the BioMax?15. The dilution sampling system enabled
reliable measurements over a wide range of concentrations: the use of high sensitivity instruments allowed measurement at
very low concentrations (∼1 μg·m−3), while the flexibility of dilution minimized sampling problems that are commonly encountered due to high levels of tars
in raw syngas (∼1 g·m−3). 相似文献
523.