Plant and fungal community responses to different methods of Brassica removal

Riley T. Pratt, Stephanie N. Kivlin, Jessica D. Pratt, Margaret B. Royall, Jennifer M. Talbot

Orange County Society for Conservation Biology

• Speaker Seminar Series• Field Trips• Restoration Projects & Research

www.ocscb.org

Upper Newport Bay Ecological Reserve: 752 Acres

4.8 ACRE SLOPE

COASTAL SAGE SCRUB

NATIVE GRASSLAND

INVASIVES: BRASSICA AND ERODIUM SPP.

Effects of Brassica Invasion on Ecosystems

• Alter structure and composition of coastal sage scrub (CSS)

• Disrupt native fungal communities on which many CSS plant species depend

Establishing experimental Brassica removal plots

4 treatments x 4 reps. = 16 plots

Treatments:1. Herbicide (2% glyphosate)2. Mow3. Hand-weed4. Control

Treatments applied in Mar & Dec 2009 and Dec 2010

Responses Measured (Spring 2010-2012):• Percent cover of all plant species• Fungal hyphal length in soil

Research Questions

How do different methods of Brassica removal impact:

1. Cover of Brassica species?2. Overall cover of native and exotic vegetation?3. Plant species composition?4. Fungal biomass in soil?

March 2010: Handweeding suppresses Brassica and promotes native plant cover more than controls

Native cover: F3,15 = 3.93, P=0.036; Brassica cover : F3,15 = 8.13, P = 0.003; Non-Brassica exotic cover: F3,15 = 11.65, P < 0.001

Removal Treatments

Mowing & handweeding ↓ Brassica and ↑ the native Deindandra fasiculata

MRPP T = -7.74, A=0.415, P < 0.0001

Removal Treatments

F3,15 = 3.343, P = 0.038

Brassica removal increases fungal biomass

Removal Treatments

March 2011: Handweeding suppresses Brassica and promotes native plant cover more than controls

Native cover: F3,15 = 0.8, P=0.511; Brassica cover : F3,15 = 2.22, P = 0.138; Non-Brassica exotic cover: F3,15 = 4.29, P =0.028

Removal Treatments

January 2012: Handweeding suppresses Brassica and promotes native plant cover more than controls

Native cover: F3,15 = 0.13, P=0.9397; Brassica cover : F3,15 = 7.2, P = 0.005; Non-Brassica exotic cover: F3,15 = 7.86, P =0.004

Removal Treatments

SummaryHerbicide• Reduced all plant cover types initially but currently has the

highest cover of Brassica• Initially increased soil fungi compared to the control

Mowing• Did not affect Brassica, native, or exotic plant cover• Resulted in the greatest initial increase of soil fungi

Hand-weeding• Most effectively reduced Brassica cover and increased

native plant cover.• Initially increased soil fungi compared to the control

Is hand-weeding worth the effort?

AcknowledgementsResearch, design, data collection: Steve Allison, Bob Reed, Kathleen Treseder, and Numerous OCSCB volunteers

Collaborators: Matt Yurko (CCC), Jeff Stoddard (DFG), County of Orange Park and Rec

Funding: Sonoran Joint Venture Foundation, Newport Bay Conservancy

www.ocscb.org

Soil fungi increase when soil nitrate declinesSoil hyphal length (m

m/g dry soil)

% Change in soil NO3- after 1 month

No treatment

Herbicide

Hand-weeding

Mowing

No treatment Herbicide Mowed Hand-weeded

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Pre-treatment

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No treatment Herbicide Mowed Hand-weeded

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