studies were initiated at the INEEL in 1950 with the establishment
of 99 permanent sample plots at 1.6-km intervals along two
perpendicular lines that transect the area from southwest to
northeast and from southeast to northwest.
Seven plots were destroyed by farming or range seeding
prior to 1957; data
from the remaining plots were collected in 1957, 1965, 1975, 1985,
and 1995. Data from a
35-plot subsample were collected in 1978, 1983, and 1990.
Data from these permanent transect plots form the basis for
numerous publications and reports (INEEL
1957, several clusters of additional permanent plots were
established in some community types that inadvertently had been
missed by the original transects (see Harniss 1968).
These plots have not been examined on a regular basis.
Between 1955 and 1959, 16 25-m2 permanent
quadrats were established to evaluate effects of periodic
radioactive contamination on natural vegetation (McBride et al.
1978). Eleven of
these quadrats were re-examined in 1976 by French and Mitchell
(1983). Earlier maps
depicting major vegetation types at the INEEL were prepared by
Harniss and West (1973) and McBride et al. (1978).
Over the past two decades, numerous vegetation studies have
been conducted at the Idaho National Environmental Research Park (INEEL
The data from
the permanent transects and from other studies (e.g. Floyd 1982)
show that plant communities at the INEEL form continuously
varying, complex patterns. This
complexity is readily apparent in the vegetation map (Vegetation
species composition and structure of individual assemblages
depends on local soils and topography, availability of propagules,
disturbance history, herbivore impacts, and outbreaks of insects
or pathogens. Coupled
with this spatial heterogeneity is temporal variability in
climate, which, over periods of years to decades, can cause
significant change within a local patch of vegetation.
Data from the permanent plots show that cover of shrubs and
perennial grasses may fluctuate by as much as 100% and 500%,
respectively, over the span of a few decades in the absence of any
major disturbance (Anderson and Inouye 1988).
Average species richness per plot has increased over the
past 45 years, as has the variability in species composition among
plots that were very similar in 1950.
The increase in richness reflects an increase in the size
and distribution of populations, especially perennial grasses,
that were depleted in 1950 as a result of extended drought in the
1930ís and 1940ís (ibid.).