Autumn burning to maintain remnant wet prairies benefits the endangered Bradshaw's desert parsley Lomatium bradshawii and other early flowering species in Willamette Valley, Oregon, USA

  • Published source details Pendergrass K.L., Miller P.M., Kauffman J.B. & Kaye T.N. (1999) The role of prescribed burning in maintenance of an endangered plant species Lomatium bradshawii. Ecological Applications, 9, 1420-1429


Less than 1% of prairie present prior to Euro-American settlement remains in Willamette Valley, Oregon (northwest USA). Responses of the endangered Bradshaw's desert parsley Lomatium bradshawii (a perennial herb) to prescribed autumn burns for maintaining remnant wet prairies were evaluated in two areas of the Valley. As it is spring-flowering, this suggests that L. bradshawii might respond positively to autumn season burns.

Areas supporting L. bradshawii were treated with two or three autumn burns. During May and June 1988, 3 blocks (each about 2 ha) were laid out at Rose Prairie (A, B and C). Treatments were randomly assigned to each block, one of each burn treatment (A and B, see blow) and an unburned control (C). At Fisher Butte, there were five treatment blocks (each about 4 ha), with two replicates of each burn treatment (A, B, D and E) and a control.
On 11 October 1988, burns (strip head burning) were conducted on all assigned blocks. On 19 September 1989, block B at Rose Prairie and blocks D and E at Fisher Butte were reburned. All burn treatments were reburnt in autumn 1991.
Foliar crown area, height, umbellets (secondary umbels) and schizocarps (fruit) of 150 L. bradshawii at Rose Prairie and 250 at Fisher Butte, and recruitment and density in 2 x 2 m plots, were recorded during 1988-1996.

Burning initially enhanced schizocarp production at both sites; schizocarps declined 1-2 years after burning but remained much higher than in controls until 1996. Overall, L. bradshawii foliar crown area, height, umbellets and number of schizocarps per plant initially responded positively to burning, but increases were not consistent across years or sites. Burning accentuated differences in L. bradshawii size and reproductive capacity between the sites and differentially affected recruitment and density.

Autumn burning gave a competitive advantage to early flowering species (such as L. bradshawii) having set seed and stored underground reserves for the next year prior to burns; late-flowering species were disadvantaged. Burning also reduced encroaching woody vegetation height, thus benefiting smaller species, e.g. L. bradshawii, whose flowering otherwise declines rapidly under increasing shade.
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