• Effects of Soil Disturbance on Plant Succession and Levels of Mycorrhizal Fungi in a Sagebrush-Grassland Community

      Doerr, T. B.; Redente, E. F.; Reeves, F. B. (Society for Range Management, 1984-03-01)
      A 5-year study was conducted to determine the effects of soil disturbance on plant succession and the relationship between plant succession and mycorrhizal inoculum potential (MIP) in a big sagebrush-grassland vegetation type. Disturbed plots, consisting of 4 levels of soil disturbance, were established in 1976, 1977, and 1979 to evaluate environmental fluctuations. Perennial grass canopy cover and aboveground biomass production were positively correlated with MIP and negatively correlated with disturbance treatments. Annual forb canopy cover (primarily nonmycorrhizal species) and aboveground biomass were negatively correlated with MIP and positively correlated with level of soil disturbance. Weather fluctuations had a greater effect on annual plants than perennial plants after the perennial species were established. MIP values appeared to be a general indicator of the type and rate of plant succession that will evolve following soil disturbance.
    • Lightning Fires in North Dakota Grasslands and in Pine-Savannah Lands of South Dakota and Montana

      Higgins, K. F. (Society for Range Management, 1984-03-01)
      Lightning strike fires which occurred between 1940 and 1981 were studied in mixed-grass prairie grasslands and in pine-savanna lands in the Northern Great Plains region. A majority (73%) of ignitions occurred during July and August, while a lesser number was recorded in April, May, June, and September. The April-September period is also the average time of the freeze-free period and approximates the average distribution period for thunder-storm activity in this region. The area burned by each of 293 lightning fires (most of which were suppressed) ranged from 0.004-1158.3 ha (mean = 10.8 ha). The frequency of lightning fires in mixed-grass prairie grasslands averaged 6.0/yr per 10,000 km2 in eastern North Dakota, 22.4/yr per 10,000 km2 in southcentral North Dakota, 24.7/yr per 10,000 km2 in western North Dakota, and 91.7/yr per 10,000 km2 in pine-savanna lands in northwestern South Dakota and southeastern Montana. The ecological role of lightning-set fires is discussed relative to the development of resource research and management plans and to the interpretation of historical records of natural fire occurrence in the Northern Great Plains region.