Shannon Claeson USDA Forest Service, PNW Research Station, Olympia, WA Olympic Knotweed Working Group Nov 16, 2011

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1 Shannon Claeson USDA Forest Service, PNW Research Station, Olympia, WA Olympic Working Group Nov 16, 2011

2 Perennial Dense monocultures Moist soil, partial sunlight Disturbed sites (rivers, roads) Allelopathic biochemicals Displaces native vegetation

3 Very difficult; several years of persistent treatment Large patches Herbicides Foliar application of 1% Habitat or Polaris AQ (Imazapyr) Stems > ½ inch; injection of 100% AquaMaster (glyphosate) Control efficacy Measure of reduced knotweed. Goal is passive reestablishment of native plant assemblages.

4 Study objectives Are knotweed control methods in riparian areas successful in meeting the restoration goal? Do riparian areas previously treated for knotweed have: Native plant assemblages? Similar plant assemblages to areas that never had knotweed (no treatment)?

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6 Cook R. 7 knotweed sites treated annually: Elk Cook Porter Stony Elk R. 5 knotweed sites Porter R. 11 knotweed sites Treatment methods: 2004 Stem injection with 100% Aquamaster Either stem injection (as above) or foliar spray with 2% Aquamaster & 1% Habitat Foliar spray with 1% Habitat or Polaris AQ Stony R. 12 knotweed sites

7 Satsop River 12 knotweed sites treated annually: Treatment methods: Foliar spray with 1% Habitat or Polaris AQ

8 Stony 16 - Stony 16 - Plant species % cover (with overlap) 20m 2 per site surveyed K & R paired sites (47 pairs) Pairs have similar: Aspect Geomorphology Canopy cover within 50m of each other Elk 02 - Elk 02 -

9 Species categorized as either: o Native or Exotic (USDA Plants list) o o Invasive or Noninvasive (WA state & county weed lists) moss, grass, forb, shrub, tree Linear regression paired analysis Treatment effect vs. Response variables: Taxa Richness: Invasive, Exotic, Native % Cover: Invasive, Exotic, Native % Cover: forbs & shrubs, trees 1m 2 survey plot along Satsop River

10 NATIVE & NOT-INVASIVE: 73 forbs, 9 grasses, 19 shrubs, 21 trees. NATIVE & INVASIVE: 3 forbs (cleavers bed straw, cow-parsnip, manroot). EXOTIC & NOT-INVASIVE: 30 forbs, 9 grasses, 1 shrub (dog rose). EXOTIC & INVASIVE: 20 forbs, 1 grass, 4 shrubs. Natives Exotics Invasives Shade tolerant Intolerant Intolerant Perennial Annual N-fixing Toxic Toxic Plant species associated with sites: bull thistle Ex/In foxglove Ex/In creeping buttercup Ex/In Himalayan blackberry Ex/In tansy ragwort Ex/In fringed willowherb Nt thimbleberry Nt red elderberry Nt

11 # Exotic species bull thistle reed canarygrass common yarrow # Exotic species Exotic Taxa Richness Cook/Elk/Porter/Stony Satsop Knot>Ref p < Knot=Ref p > 0.05

12 % cover (log) foxglove % cover (log) Exotic % cover Forbs & Shrubs Cook/Elk/Porter/Stony dog rose creeping buttercup Satsop Knot>Ref p < Knot>Ref p =

13 # Invasive species cow parsnip herb robert / stinky bob # Invasive species reed canarygrass Invasive Taxa Richness Cook/Elk/Porter/Stony Satsop Knot>Ref p < Knot=Ref p > 0.05

14 % cover (log) % cover (log) Invasive % cover Forbs & Shrubs Cook/Elk/Porter/Stony Satsop Himalayan blackberry tansy ragwort cleavers bedstraw Knot>Ref p < Knot>Ref p =

15 # Native species horsetail monkey flower palmate coltsfoot red elderberry # Native species Native Taxa Richness Cook/Elk/Porter/Stony Satsop Knot=Ref p > 0.05 Knot<Ref p =

16 Native Taxa Richness Native Taxa Richness Native Taxa Richness Native Taxa Richness Satsop Knot<Ref p = Cook/Elk/Porter/Stony Knot=Ref p > Distance from water (meters) Knot<Ref p = PHAR % cover Canopy Cover %

17 Pacific ninebark % cover (log) piggy-back & fringe cup lady fern salmonberry % cover (log) Native % cover Forbs & Shrubs Cook/Elk/Porter/Stony Satsop Knot<Ref p = Knot<Ref p =

18 Western red cedar % cover big leaf maple seedling Sitka willow red alder % cover Native % cover Trees Cook/Elk/Porter/Stony Satsop Knot=Ref p > 0.05 Knot<Ref p =

19 % cover % cover Native % cover Trees Cook/Elk/Porter/Stony Satsop Knot=Ref p > 0.05 Knot<Ref p = Canopy Cover % Canopy Cover %

20 Exotic taxa richness & % cover: sites > sites Invasive taxa richness & % cover: sites > sites Native taxa richness: sites sites Cook/Elk/Porter/Stony: - reed canarygrass cover Satsop: + Canopy cover, - Distance from water Native % cover: sites > sites Trees: + Canopy cover

21 No detectable influence of different control methods: Methods changed over time for all streams (i.e., no time effect). Study not designed to test this specific question. No detectable differences in current plant assemblages among knotweed sites due to: Number of years treated (4-7 year range) Patch size ( m 2 ) Stem count ( stems)

22 removal opens habitat for colonization by both native & exotic plants. often replaced by other invasive plants. Good natural recovery potential of native plants at riparian sites: With established large trees providing canopy cover, No or few other invasives (e.g., reed canarygrass).

23 Reiterate importance of maintaining riparian canopy cover! Prioritize areas for knotweed control or native re-plantings? Post-knotweed removal, monitor & control secondary invasive species (while abundance is low)? Can we control multiple invasive plants at same time? April 2009: TNC planted willow stakes August 2011: Same site, willow growing

24 Funding provided by: - U.S. Fish & Wildlife Service - U.S. Forest Service Site access & treatment history: - April Boe and Laurel Carver, formerly with TNC-Olympia (in June 2011, TNC transitioned to The Center for Natural Lands Management) Center for Natural Lands Management Field surveys & plant identification: - Lara Boyd & Christine Davis, USFS

25 Ecological reasons why goal may not be achieved: 1. Another underlying driver of ecological change (e.g., altered hydrology), 2. Native species are dispersal limited, not competition limited (e.g., isolated patches of native plants), 3. has altered the habitat & the habitat is inhospitable for native species (e.g., altered soil chemistry, erosion).