Abstract:
Since the 1930's, many fields on the Crooked River National grasslands have been
seeded to crested wheatgrass (Agropyron desertorum). While some of these fields
remain dominated by crested wheatgrass others had a greater presence of deep
rooted native perennial grasses such as bluebunch wheatgrass (Pseudoroegneria
spicata). Twenty eight fields previously seeded to crested wheatgrass were
sampled to determine vegetation composition, soil nutrient status, and depth to the
restrictive layer. Fourteen of the fields had a greater presence of native grasses and
fourteen remain dominated by crested wheatgrass. In addition, root samples were
collected from 10 of the 28 fields to determine the percent of root length colonized
by mycorrhizae for crested wheatgrass and bluebunch wheatgrass. Soil samples
from a random sample often fields were used to determine the genera of
mycorrhizal fungi present. Vegetation and soil data were analyzed using
multivariate methods. Results indicated that the two field types were different with
respect to species composition confirming the appropriateness of the site selection
criteria. The associated soil environmental variables also differed between field
type. The strongest association was that of soil particle size. Fields with a greater
presence of native grasses were positively associated with soils having a higher
percent of clay and silt. Fields where crested wheatgrass remained dominant were
strongly associated with soil having a higher percent sand. Other soil
environmental variables that were positively associated with each field type were
exchangeable magnesium, percent organic matter for the fields with a greater
presence of native grasses and exchangeable potassium and extractable phosphorus
with the crested wheatgrass fields. The data for percent of root length colonized by
mycorrhizae were analyzed using a one way analysis of variance. The results
indicated that there was no difference in percent root length colonized between
crested wheatgrass and bluebunch wheatgrass. There were 4 genera of mycorrhizal
fungi present on the 10 fields evaluated and none of these genera were exclusive to
either field type. The crested wheatgrass fields with a greater presence of native
grasses were different from those remaining dominated by crested wheatgrass with
respect to vegetation and soils characteristics. Further work needs to be done to
establish membership of the mycorrhizal community.
