- Native prairies of the Willamette Valley are considered among the rarest of
Oregon’s ecosystems and are in critical need of conservation. Management strategies for
increasing the abundance of native species are urgently needed, particularly those
strategies that promote the regeneration of native species from seed. Fire may be an
important factor in promoting regeneration of native species from seed because of its
historical role in maintaining the prairie landscape.
The study objectives were (1) to determine the effect of prescribed burning on
regeneration of native species from seed, and (2) to establish predictive relationships
between easily measured plant traits and seedling establishment rates in the field. The
general approach was to sow seeds of target wetland prairie species during the fall into
experimental field plots already established at the Danebo Wetland, Eugene, OR.
Seedling establishment rates were then compared between burned and unburned plots the
following spring. To establish predictive relationships these seedling establishment rates
were related to selected seed and seedling traits measured under laboratory conditions.
Overall seedling establishment rates showed no significant differences between
burned (7.0%) and unburned plots (8.7%), although for the seven species showing
positive responses to prescribed burning, the increase was approximately doubled in the
burned plots. Burning significantly increased the seedling establishment rates of three
species, Wyethia angustifolia, Grindelia integrifolia, and Danthonia californica.
Seedling establishment significantly decreased with burning for one species, Sidalcea
campestris. For three of the four endangered, threatened or rare species, Aster curtus,
Horkelia congesta, and Sidalcea cusickii var. purpurea, seedling establishment rates were
smaller in the burned plots compared to the unburned plots, although the differences were
not significant. Lomatium bradshawii had no seedlings establish in either the burned or
the unburned plots.
Plant weight 7 days after germination was the best trait at predicting field seedling
establishment rates for both the burned plots and the unburned plots, explaining a
significant amount of variation in establishment rates: 70% for the burned plots and 45%
for the unburned plots. This model could be used by managers to choose species for sowing in burned and unburned prairies or to estimate seeding rates at burned and