The effects of some environmental influences on big sagebrush, Artemisia tridentata Nutt., reinvasion
Year: 1966
Type: dissertation
Abstract: Twenty areas in southwestern Montana were chosen to examine several environmental factors thought to influence big sagebrush reinvasion.Fifteen of the areas were chemically sprayed and five were plowed and reseeded.The earliest year of treatment was 1957 and the latest was 1964, The factors examined for their influence on reinvasion were wind-borne sagebrush seed, the success of the brush control project, nonsagebrush vegetational competition, soil textural differences, yearly and seasonal precipitation patterns and totals, and date of plowing in relation to sagebrush seed maturity.Field data were gathered along interrupted belt transects with paired plots at regular predetermined intervals.From three to 23 transects each 150 meters long were used in each of the 20 locations with 114 to 734 paired plots examined in every location.Data gathered at the paired plots were recorded on IBM Port-a-punch cards in the field and later transferred to standard 80 column cards for analyses.Arithmetic manipulation, regression, and correlation were used to evaluate the factors thought to influence reinvasion.Eight locations were examined for wind-borne seed as a factor affecting sagebrush reinvasion.Adjacent non-treated sagebrush areas were found not to influence reinvasion.The extent to which reinvaded sagebrush was found in association with treatment-surviving sagebrush shows reinvasion was inversely related to the initial success of the eradication.The correlations were low indicating a confounding of factors may have existed.Non-sagebrush vegetation, as determined by basal intercept, was found not to influence reinvasion.Data to evaluate the influence of nonsagebrush vegetation on yearly reinvasion were collected in 1965. Had the collections been made yearly, the correlations may have been quite different.The effects of surface soil texture, exposure, slope, and erosion on reinvasion and on basal cover by vegetation were analyzed.All factors, except exposure, showed very little influence on reinvasion.These results may be attributable in part to experimental procedure.The exposures to the north had greater reinvasion and basal cover by vegetation than did other exposures.This variation probably has more meaning in suggesting different exposures support different quantities and/or types of vegetation than an implication for planned sagebrush control.Precipitation, both yearly and growing season, and sagebrush reinvasion rates were examined to determine if precipitation influenced reinvasion.No relationship was found for any of the three locations examined separately or for all the locations examined collectively.This shows factors other than precipitation precluded sagebrush survival.It is felt the unknown yearly death rate of reinvaded sagebrush, as well as probable changes in serai community-competition, and other factors may have masked possible relationships between precipitation and reinvasion.
Author: James R. Johnson
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
SDG: Life on land
Open Access status: green
OpenAlex ID: W170944937