Using ecological niche modeling to predict the distributions of two endangered amphibian species in aquatic breeding sites |
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Authors: | Lior Blank Leon Blaustein |
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Institution: | (1) Centre for Ecology & Hydrology, Bush Estate, Penicuik, Edinburgh, Midlothian, EH26 0QB, UK;(2) School of Conservation Sciences, Bournemouth University, Poole, Dorset, BH12 5BB, UK |
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Abstract: | Waterfowl can cause substantial reductions in plant standing crop, which may have ecological and economic consequences. However,
what determines the magnitude of these reductions is not well understood. Using data from published studies, we derived the
relationship between waterfowl density and reduction in plant standing crop. When waterfowl density was estimated as individuals
ha−1 no significant relationship with reduction in plant standing crop was detected. However, when waterfowl density was estimated
as kg ha−1 a significant, positive, linear relationship with reduction in plant standing crop was found. Whilst many previous studies
have considered waterfowl species as homologous, despite large differences in body mass, our results suggest that species
body mass is a key determinant of waterfowl impact on plant standing crop. To examine relative impacts of waterfowl groups
based on species body mass, a measure of plant biomass reduction (R
s) per bird per hectare was calculated for each group. Comparison of R
s values indicated some differences in impact between different waterfowl groups, with swans having a greater per capita impact
than smaller-bodied waterfowl groups. We present evidence that this difference is linked to disparities in individual body
size and associated differences in intake rates, diet composition and energy requirements. Future research priorities are
proposed, particularly the need for experiments that quantify the importance of factors that determine the magnitude of waterfowl
impacts on plant standing crop. |
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