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POPULATION DYNAMICS OF AMBIENT AND ALTERED EARTHWORM COMMUNITIES IN ROW-CROP AGROECOSYSTEMS IN OHIO, USA
Citation:
Shuster**, W., M. Shipitalo, P. Bohlen, S. Subler, AND C. A. Edwards. POPULATION DYNAMICS OF AMBIENT AND ALTERED EARTHWORM COMMUNITIES IN ROW-CROP AGROECOSYSTEMS IN OHIO, USA. Presented at 7th International Symposium on Earthworm Ecology, Cardiff, Wales, AUSTRALIA, September 01 - 07, 2002.
Impact/Purpose:
To inform the public.
Description:
Although earthworms are known to influence agroecosystem processes, there are relatively few long-term studies addressing population dynamics under cropping systems in which earthworm populations were intentionally altered. We assessed earthworm communities from fall 1994 to spring 1997 in plots with ambient communities and plots to which earthworms had been added in chisel (CS, Corn-Soybean) and ridge-till (CSW, Corn-Soybean-Wheat) agroecosystems in south-central Ohio (USA). Earthworm communities were altered by adding predominantly a deep-burrowing anecic species in the spring and fall of each year beginning in the fall of 1994 and ending in the spring of 1997. We evaluated the abundance of the predominant species from epigeic (Lumbricus rubellus Hoffmeister), endogeic (Octolasion tyrtaeum Savigny), and anecic (L.terrestris Linnaeus) ecological groups. Our analyses indicated that adding populations of anecic species resulted in small increases in anecic populations (7 ind. m-2) compared to numbers in semiannual additions (100 m-2). In plots to which earthworms were added, establishment of anecic species was apparently at the expense of epigeic species, which declined four and two-fold in CS and CSW systems, respectively, in plots with added anecic earthworms. Although populations of endogeic species were slightly greater in CSW than CS systems, these species were not affected by the earthworm additions. Earthworm additions were discontinued after spring 1997 and we returned five years later to assess populations. These recent results indicated that anecic species persisted only in ridge till (CSW) plots, suggesting that conditions in the CS cropping systems were unfavorable for establishment and persistence of anecic species. The previously observed decrease in L. rubellus populations in plots with added anecic worms was no longer evident providing further evidence of potential competition between populations of L. rubellus and L. terrestris in these agroecosystems.