Grasshoppers, grass, and grazing: a report from Arianne in China

update from the Inner Mongolia grassland by Arianne:

Livestock overgrazing in the Eurasian grassland has become an increasing concern in recent decades. It is often sited as the primary driver for steppe degradation – a major socioeconomic issue. One question that we have been addressing this summer is how does livestock grazing influence grasshopper distribution and abundance. Specifically, we’ve found outbreaks of Oedaleus asiaticus exclusively in overgrazed pastures. [For more information on outbreaks and migratory polyphenism in this grasshopper, see our recent publication: link:

http://dx.doi.org/10.1016/j.jinsphys.2010.05.020%5D.

Making a living as a grasshopper in Inner Mongolia is harder than you think!

We’re investigating how anthropogenic impacts on plant communities (overgrazing) then impacts insect herbivores. In addition to clear differences in plant structure (e.g. open bare ground in overgrazed fields), differences in plant chemistry may also be contributing to grasshopper distribution. Grasses in long-term grazed fields often have a lower nitrogen content due to loss of top soil and available organic nitrogen as compared to ungrazed fields. Over the past three summers, we found that O. asiaticus growth performance decreases as host-plant nitrogen increases (decreasing C:N) and that this hopper prefers host-plants from heavily grazed areas. I’ll be presenting this data at ESA (afternoon of Aug 4): “Too much nitrogen? Host-plant N enrichment negatively impacts locust Oedaleus asiaticus performance”

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