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21xx1 was churtctcnrcd by an untuwlly Harm and do spring, and plant growth stage :tppe:uLd a be <br />sonx:\\hat ad\'anCOd, a5 COmp,lrcd 10 lIIC Olhu 1'CarS Of ll1C Slady' Ik7n51N Of tax aUS pllnls IS SUIIICCt t0 <br />Icss year to yrar \arlrtion due to chtnatc. gmrmg. and other uncontrolled \anablcs than is c0\cr, :utd is a <br />mme pa~cisc tool for :tsscssing success of control eRons on target spctlcx In llkll, a numlx:r of thisUc <br />plants within Rcfcrcrtec Arra w l wcrc nand ro he infested by the Ltnac of the p:tmtcd lady' twucrlly, but <br />the percurtage of plants with I:uvac was much lower In Referrncc Area w 1 than in Refercncc Arc;l d2 and <br />adjacent arras <br />Figure 2 - Sutoy Reforonce Area Y1 Noxious <br />Species Density <br />c <br />~ 20 ~ <br />m 15 ~ tThistle <br />a <br />~ 10 <br />to --+}-Thistle d <br />~ S <br />Houndstongue <br />0 ~ - Combined <br />1998 1999 2000 2001 <br />From 1998 to 2tNl l , absolute cover of noxtous spaics arxl non-raxious fofis dcchnrd, whUc gross co\ cr <br />Incrraad 2(x11 towl vcgctaunn crn'cr wars srgnificatuly lower Ulan in I'r»t, because Ux mcrr.~xr m grass <br />cover did nol offset the rktiline in forb:md noxious species co\cr (Figure ~ I <br />Figure 3 -Sutey Reference Area p2 Absolute <br />Cover Trends; 1998-2001 i <br />m 60.0% ~ ~ Total Vegetation <br />c 50.0% - - Cover <br />~ 40.0% - - ~- Non-noxious Forb <br />~ 30.0% ~ -- Cover <br />20.0°~, ~ ~ .-Grass Cover <br />a 10.0% -- - <br />~ ~ Noxious Species <br />0.0% -• ' <br />1998 1999 2000 2001 <br />1'aMe 5 lists 2rxll absolute and rclau\c coca M spocla and retcgon' '1'ublc 6 pracnts absolute artd <br />rclnu\c coca sample ntGtns by wtcgon atxl year, 199x through 2(xil Absolute co\cr of noxious species <br />dcchncd from 11.G'~6 to 2.6%mtr the xtlrsc of the study, whde at+solutc cover of perennial grassy <br />mcrcaxti liom 14°~a to 20.2°'a Total xcgcution co\cr rcnctias low, at only 2x°.-6 Non-noxiota Forb co\'cr <br />dcchnod from 371`5 in 1998, l0 5.2"i° in 21x1 I <br />At thr mdixldual species Ic\rl, cxrccr of the noxious plumclcss thisUc dcchn~d fmm'Lr~!° in ltrihi, to us", <br />in 2(xl I Intpu~ts a other, lax abund:mt noxious spcct\s were ncx c\idcnt from the cover drta. Of the vast <br />common pcrcnnl:d forts, ciccr mdl:ecteh (: LcrrnKnlux aver) dcelincd from 17.6%to 22°/w yarrow <br />