Linkages Among Soil Properties, Invasive Earthworms and Plants In a Palouse Prairie Ecosystem.

The earthworm-plant-soil relationship is poorly characterized.  Understanding the dynamic linkages between earthworms and other ecosystem components is critical as it has been suggested that invasive earthworms may facilitate plant invasions.  Our purpose was to characterize relationships among earthworms, plants and key soil properties in a Palouse Prairie grassland.  A prairie remnant was divided into three sampling zones based on the plant community.  Zone 1 was dominated by Snowberry (Symphoricarpos albus), a native species and zones 2 and 3 were dominated by exotic species:Ventenata (Ventenata dubia) in zone 2 and Prickly Lettuce (Lactuca serriola) in zone 3.  Earthworm density was 52 individuals m^-2 in zone 1, 81.1 individuals m^-2 in zone 2 and 49.8 individuals m^-2 in zone 3.  Total earthworm biomass in zone 2 (53.5 g m^-2) was significantly greater than in zone 3 (14 .7 g m^-2) (P = 0.0384). Total soil N in the 0 to 10 cm and 30 to 50 cm depths was significantly greater in zones 1 and 3 (P = 0.0001and 0.01, P = 0.031 and 0.0056) compared to the same depths in zone 2 which had the highest exotic earthworm density.  Total carbon in the 0 to 10 and 30 to 50 cm depths was significantly greater in zone 1 and 3 than in zone 2 (P < 0.0001 and 0.0194, P = 0.0079 and 0.0289).  Zone 3 had highest plant diversity and native plant diversity and was the only zone where native earthworms were found.  Overall zone 3 had the lowest exotic earthworm density, highest plant diversity and native plant diversity, and the greatest concentrations of soil N and C.  These relationships should be futher characterized to gain a better understanding of processes contributing to and the consequences of earthworm invasion.