Grasshopper (Orthoptera: Acrididae) communities respond to fire,bison grazing and weather in North American tallgrass prairie: a long-term study |
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Authors: | Jayne L Jonas Anthony Joern |
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Institution: | (1) Division of Biology, Kansas State University, Manhattan, KS 66506, USA |
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Abstract: | Because both intrinsic and extrinsic factors influence insect population dynamics, operating at a range of temporal and spatial
scales, it is difficult to assess their contributions. Long-term studies are ideal for assessing the relative contributions
of multiple factors to abundance and community dynamics. Using data spanning 25 years, we investigate the contributions of
weather at annual and decadal scales, fire return interval, and grazing by bison to understand the dynamics of abundance and
community composition in grasshopper assemblages from North American continental grassland. Each of these three primary drivers
of grassland ecosystem dynamics affects grasshopper population and community dynamics. Negative feedbacks in abundances, as
expected for regulated populations, were observed for all feeding guilds of grasshoppers. Abundance of grasshoppers did not
vary in response to frequency of prescribed burns at the site. Among watersheds that varied with respect to controlled spring
burns and grazing by bison, species composition of grasshopper assemblages responded significantly to both after 25 years.
However, after more than 20 years of fire and grazing treatments, the number of years since the last fire was more important
than the managed long-term fire frequency per se. Yearly shifts in species composition (1983–2005), examined using non-metric
multidimensional scaling and fourth-corner analysis, were best explained by local weather events occurring early in grasshopper
life cycles. Large-scale patterns were represented by the Palmer Drought Severity Index and the North Atlantic Oscillation
(NAO). The NAO was significantly correlated with annual mean frequencies of grasshoppers, especially for forb- and mixed-feeding
species. Primary grassland drivers—fire, grazing and weather—contributing both intrinsic and extrinsic influences modulate
long-term fluctuations in grasshopper abundances and community taxonomic composition.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Fire frequency Konza Prairie Long-Term Ecological Research Program Weather Insect populations |
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