Plant Diversity Response to Herbicides 



Like-herbicide plots pooled for all 4 sites 



1.4-r 



1.2- - 



1 -I- 



X 



(D 



■o 

 c 



S 0.8- 

 > 

 (0 



5 



CO 



0.6- 



0.4- 



0.2- - 



Pretreatment 



Check 

 Tordon 

 Stinger 

 Curtail 



Posttreatment 



88 

 Warm 



89 

 Cool 



-+- 



-+- 



90 90 

 Cool Warm 

 Season 



91 



Cool 



91 

 Warm 



Plant Diversity Response to Herbicides 



Like-herbicide plots pooled for all 4 sites 



c 



(D 

 O) 



re 



45 



40-- 



35-- 



30 



" 25-^ 



(D 

 Xi 



E 



20-- 



15- 



10 



Pretreatment 



Check 



■ Tordon 



■ Stinger 

 Curtail 



Posttreatment 



88 

 Warm 



89 

 Cool 



1 \ — 



90 90 

 Cool Warm 

 Season 



91 



Cool 



91 

 Warm 



Figure 1 — Average Shannon-Weaver diversity 

 index for check plots and herbicide-treated 

 spotted knapweed plots at four sites. 



Figure 2 — Average number of plant species 

 for check plots and herbicide-treated spotted 

 knapweed plots at four sites. 



Table 7 — Minimum and maximum soil herbicide residues (ppb-dry weight) pooled for all sites 

 and times of application^ 



Depth 



Curtail 

 2,4-D + Clopyralid 



Stinger 

 Clopyralid 



Tordon 

 Picloram 



Pooled 

 Sites + times 

 At 30 days 

 (1989) 



Pooled 

 Sites + times 

 At 1 year 

 (1990) 



Pooled 

 Sites -I- times 

 At 2 years 

 (1991) 



cm 

 0-5 

 5-25 

 25-50 



5 



25 



25-50 

 50-100 



5 



25 



52 - 535 -I- 28 - 243 

 nd - 31 -1- nd - 1 1 

 nd - 14 + nd 



nd-26* -I- nd - 14 

 nd - 1 -I- nd 

 nd + nd 

 ns 



ns 

 ns 



37 - 320 

 nd - 14 

 nd 



nd - 18 

 nd 

 nd 

 ns 



ns 

 ns 



42 - 470 

 20 - 270 

 10-26 



14-29 

 nd - 16 

 nd-t 

 nd 



nd-t 

 nd 



'nd = none detected; t = trace, but less than the method detection limit of 10 ppb; ns = not sampled 

 (residues unlikely); * 2,4-D at 1 year was detected at only one site. 



5 



