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20 <br />• component and forbs were significantly more productive on 15 cm <br />than any of the deeper topsoil depths. <br />The response of individual seeded species varied over time as <br />shown in Table 6. Several grass species such as crested wheatgrass <br />(Aaropvron cristatum), bluebunch wheatgrass (A. snicatum) and green <br />needlegrass (Sti a viridula) showed highly consistent responses <br />over time, regardless of the depth of topsoil. Aboveground biomass <br />of intermediate wheatgrass (ASropvron intermedium) declined <br />dramatically between 1985 and 1990 to levels far below those <br />observed in 1983. Western wheatgrass (Agrooyron smithii) also <br />declined during this same time period but to levels similar to <br />those estimated in 1983. Smooth brome responded with the largest <br />increase in production over the course of the study and went from <br />• a subdominant in 1983 to a dominant by 1990 on all topsoil depths. <br />Giant wildrye showed increases in production on most topsoil depths <br />between 1983 and 1985 and then increased significantly on all <br />topsoil treatments by 1990. The final grass that was present in <br />ecologically significant amounts was Kentucky bluegrass. This <br />species increased on the 15 and 30 cm treatments but did not show <br />any significant change on the deeper topsoil depths between 1983 <br />and 1985. Between 1985 and 1990 there were no changes in <br />production for Kentucky bluegrass on any of the topsoil treatments. <br />Cicer milkVetch and small burnet (Sanguisorba minor) were the <br />two forbs seeded in this study. These species responded in <br />different ways as shown in Table 6. Cicer milkvetch responded in <br />a similar way as Kentucky bluegrass by showing greater production <br />increases on shallow topsoil depths than on deeper depths. Small <br />