Spotted knapweed (Centaurea maculosa)

Transcription

1 Spotted knapwee d and songbirds: understanding the natu ure of invader impacts Yvette Ortega and Dean Pearson Rocky Mountain Research Station

2 Strong Invaders Spotted knapweed (Centaurea maculosa)

3 Targeted by Weed Control Programs

4 Weed management goals often go beyond invader suppression to inclu ude relief of invader impacts

5 pre-invasion invaded

6 pre-invasion invaded

7 Suppressing the Invader Doesn t Ensure Relief of Impacts? pre-invasion invaded

8 Need to Understand Nat ture of Invader Impacts pre-invasion invaded

9 Need to Understand Nat ture of Invader Impacts pre-invasion invaded to identify management strategies that best address problem and ultimately measure effectiveness of our actions

10 Impa cts of Spotted Knapweed

11 Key Qu uestions Which native plant groups are impacted by knapweed and to what degree? How do shifts in plant communities affect higher trophic levels, including songbirds? Do common weed cont trol measures alleviate invader impacts?

12 Study Sites 250 m

13 Study Sites Knapweed Native

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15 Insects

16 Chipping Sparrows

17 Pathways of Plan nt Invader Impact food nest predation

18 Chipping Sparrows nest primarily in trees

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22 Results

23 Impacts of Knapweed Invasion on Native Plants differed by fun nctional group

24 Shift in Native Plant Communities pp. co ver (% %) Na ative s PF AF PG Knapweed cover (%)

25 Does Shift in Plant Com mmunities Affect Insects? expect to see declines in prominent groups

26 Fewer Grasshoppers in Kn napweed vs. Native Habitat 7,000 Knapweed 6,000 Native No. ad dults 5,000 4,000 3,000 2,000 1,000 0 GOMP OEDI CYRT weed effect P <

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28 Delayed Breeding in Knap pweed vs. Native Habitat No. ne ests. 22 Knapweed Native weed effect Week of nest initiation P = 0.01

29 Delayed Breeding Reduces Reproductive Success songbirds have a very limited breeding season delays furth er shorten it

30 Reduced Reproductive Success Impacts Site Fidelity fewer adults return between breeding seasons

31 Reduced Site Fidelity in Knapweed vs. Native Habitat 40 Return No Return 35 No. territor rial bird ds Knapweed Native weed effect P =

32 Reduced Site Fidelity Impacts Age Structure prevalence of vs. yearling birds

33 Native Habitat with Low Turnover old der yearling

34 Native Habitat with Low Turnover YEAR 2 old der yearling

35 Native Habitat with Low Turnover YEAR 2 old der

36 Native Habitat with Low Turnover YEAR 2 old der

37 Native Habitat with Low Turnover YEAR 2 yearl ling

38 Knapweed Habitat with High Turnover yearling yearling yearl ling

39 Knapweed Habitat with High Turnover YEAR 2 yearling yearling yearl ling

40 Knapweed Habitat with High Turnover YEAR 2 yearling yearl ling

41 Knapweed Habitat with High Turnover YEAR 2 yearling yearl ling

42 Knapweed Habitat with High Turnover YEAR 2

43 Knapweed Habitat with High Turnover YEAR 2 yearling yearl ling yearling

44 Increased Turnover Affects Song Learning

45 Chipping Sparrow Song

46 Each Male has a Distinct Song Kept for Life

47 Yearlings Acquire Song from Neighbors? yearl ling

48 Native Habitat: Maintenance of Local Tradition yearl ling

49 Knapweed Habitat: Lack of Local Tradition?? yearling? yearl ling yearling

50 Knapweed Habitat: Lack of Local Tradition yearling yearl ling yearling

51 Reduced Song Similarity in Knapweed vs. Native Habitat weed effect (song similarity index): P = 0.008

52 Impa cts of Spotted Knapweed

53 pre-invasion invaded

54 Use Understanding to Evalu uate Management Options? pre-invasion invaded

55 Weed Control: Broadcastast Spraying of Tordon

56 Weed ControlwithTordon: Suppression of Knapweed

57 Weed ControlwithTordon: Release of Native Grasses

58 Weed ControlwithTordon: Release of Exotic Grasses

59 Weed ControlwithTordon: Negative Effects on Native Forbs

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61 Impa cts of Spotted Knapweed

62 Invader impacts can be complex and far-reaching Need dto dfi define pathways of fimpact: implications & management Strategies aimed at restoration must co onsider pathways of impact If goal is restoration, weed suppression alone is unlikely to suffice

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