Vegetation 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 Studies). In 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 Studies).

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 Map).  The 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 1930’s and 1940’s (ibid.).