Temporal dynamics of acoustical signatures associated with alternative managment and natural ecosystems

Six Kellogg Biological Station (KBS/LTER) ecosystems where monitored in 2005, 2006 and 2007 for their acoustical properties. Hydrophones where placed 30 cm above ground and on the soil surface in the: conventionally tilled wheat/corn/soybean rotation, no-input wheat/corn/soybean rotation, coniferous forest, successional fields or deciduous forest ecosystems. The sounds were recorded on laptop computers at: sunrise, midmorning, noon, afternoon, sunset and midnight. Each recording was done for 30 seconds and repeated multiple times in July and late August. At sundown and midnight there were differences between the above ground sounds of the native ecosystems (deciduous forest and successional fields) and the agricultural ecosystems. At midnight, the forest and succession ecosystems where full of insect sounds such as: tree crickets (Grillidae) and katydids (Tettigoniidae); while the agricultural ecosystems where equally silent throughout the day and night. There were no differences among the ecosystems for the sounds at the soil surface in 2005 and 2006, so in 2007 only the above ground sounds were measured. Also it was observed that insect sounds in forest and succession ecosystems increased as darkness increased in the evening, increasing in a sine wave manner (i.e. the relationship between the time and intensity of sound for successional field insect sounds in late August had a cubic regression R2 of 95.5%). In summary, we conclude that different ecosystems have different acoustical temporal dimensions, and that acoustics can be a useful, nondestructive tool to access ecosystem biodiversity and activity.