Soil and Nitrogen Loss from Oregon Lands Occupied by Three Subspecies of Big Sagebrush

Abstract

Measurements of runoff and soil loss from simulated highintensity rainstorms are reported for shrub interspaces of 3 sites occupied by each of 3 subspecies of Artemisia tnihhztu (big sagebrush) in each of 4 locations in eastern Oregon. A. tridentrrto ssp. wyomihgensis sites as a group had signlflcantly higher soil loss than A. LridcnteCo ssp. vaseyona sites. Comparisons of means within locations showed nonsignificant differences between land supporting big sagebrush subspecies except at Frenchglen. Soil loss was positively correlated with runoff, percent bare ground, and vesicular soil porosity; but it was negatively correlated with medium and coarse sand and coarse fragments in the surface soil and with organic ground cover. Aridisols lost more soil than Mollisols. Habitat types did not appear useful for indexing soil loss from these sites. Surface soil morphology, however, correlated with large significant differences in soil loss and may be a useful index. Organic and ammonium nitrogen loss was not correlated with a subspecies of A. tridenlatu, but did correlate with soil erosion and many of the soil features that affect soil erosion. Amounts of nitrogen lost do not appear to be critical.

SPATIAL AND TEMPORAL INFLUENCE OF SOIL FROST ON INFILTRATION AND EROSION OF SAGEBRUSH RANGELANDS1

“…Infiltration capacity was significantly greater in coppice soils than in interspace soils for all sample dates except March 1 and 3 (Figure 1). Similar results have been reported for unfrozen soils by Blackburn (1975), Swanson and Buckhouse (1984), Johnson and Gordon (1988), Thurow et al (1986), and Wood et al (1987), and for frozen soils by Blackburn and Wood (1990). Infiltration capacities for both coppice and interspace soils were greater when unfrozen and well drained in April and June than in February and March when the soils were frozen or recently thawed.…”

“…The spatial influence of shrub coppice dune (coppice) and dune interspace (interspace) soils on infiltration of unfrozen soil was originally established by Blackburn (1975) and verified by numerous other investigators (Johnson and Gordon, 1988;Swanson and Buckhouse, 1984;Thurow et al, 1986;Wood and Blackburn, 1981;Wood et al, 1987). Blackburn and Wood (1990) hypothesized that coppice and interspace soils would respond differently to soil freezing and thawing due to differences in vegetation cover and surface soil characteristics, thus imposing a spatial and temporal response in infiltration and soil erosion.…”