Temporal dynamics of acoustical signatures associatedwiht alternative management and natural ecosystems

Quintanilla, M., G. Bird, and S. Gage

Presented at the All Scientist Poster Reception (2006-05-09 )

Four KBS/LTER ecosystems where monitored in 2005 for their acoustical properties. Hydrophones where placed 30 cm above ground and on the soil surface in the: conventionally tilled corn-soybean rotation, organic-tilled corn soybean rotation, coniferous forest and deciduous forest ecosystems. The acoustical signatures were recorded on laptop computers, at 6 a.m., 9 a.m., noon, 4 p.m., 8:30 p.m. and midnight. Each recording was done for 30 seconds and repeated seven times for four days in late August. At midnight there were differences between the above ground sounds of the forest and the agricultural ecosystems. At midnight, the forest ecosystems where full of insect sounds such as: tree crickets, cicadas and katydids, while the agricultural ecosystems where equally silent throughout the day and night. There were no differences among the four ecosystems for the acoustical signatures at the soil surface, probably because of the lack of a specific activation event. To test this hypothesis, the acoustics of compost and sterilized compost where analyzed in the presence and absence of water used as a pulsing agent. Compost (200 cm3) with its natural biota (earthworms, isopods, collembola, staphilinid beetles, nematodes and other microscopic organisms) was placed in two 400 ml glass containers. One was sterilized by placing it in a microwave for 2 minutes. A hydrophone was place on a 35○ angle on the surface of both containers and the sounds recorded for 30 seconds in a sound chamber. This was repeated five times. Subsequently, 50 ml of water was added to both composts and the resulting acoustics recorded for 30 seconds five times. With the addition of water the non-microwaved compost became active and the sound intensity increased significantly compared to the three other treatments. We concluded that soil is a place where organism are often dormant and can be activated with a pulsing agent such as water. In summary we conclude that different ecosystems have different acoustical temporal dimensions, that acoustics can be a useful, nondestructive tool to access ecosystem biodiversity and that acoustics is a useful and nondestructive method for evaluating soil biological activity.

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