Browsing Journal of Range Management, Volume 47, Number 2 (March 1994) by Subjects
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Germination and seedling establishment of spiny hopsage in response to planting date and seedbed environmentReestablishment of spiny hopsage (Grayia spinosa [Hook.] Moq.) in the shrub steppe requires development of appropriate seeding technology. We examined the effect of planting date and seedbed environment on germination and seedling establishment of 2 seed sources at 2 southwestern Idaho sites. Seedbeds were prepared by rototilling. In 1987-88, seeds collected in 1986 were drilled at 66 viable seeds m-1 of row at Birds of Prey in late fall, winter, and early spring and at Reynolds Creek in late fall, early spring, and late spring. Seeds collected in 1986 and 1988 were broadcast at 400 viable seeds m-2 at both sites in late fall, early spring, and late spring 1988-89. Seeds in nylon bags were also planted at each site in late fall, winter, and early spring in 1987-88 and in late fall, winter, early spring, and late spring in 1988-89. On each succeeding planting date and in early summer, 5 bags of each seed source from each of the earlier planting dates were recovered. Water content, viability, and germination were compared among seeds from previous plantings and control seeds stored in the laboratory. Each year, first-year seedling establishment at both sites was favored by late fall compared to other planting dates. In 1988, seedlings established only from late fall plantings at a density of 1 m(-2) st each site. In 1989, late fall planting at the 2 sites increased seedling establishment 6 (51 vs 8 m-2) and 20 (41 vs 2 m-2) times compared to early spring planting. Germination was generally greater for seeds incubated at field sites compared to controls. Germination total and rate increased 6-11 times and 13 days from late fall 1987 to early spring 1988, 1-6 times and 4 and 9 days from winter 1988 to early spring 1988, 17 times and 10-11 days from late fall 1988 to winter 1989, and 4-7 times and 11 days from winter 1989 to early spring 1989. Late fall or early winter planting is essential to permit early spring germination when surface soils are moist.
The effect of Quercus douglasii removal on understory yield and compositionThe canopy of Quercus douglasii H. & A. (blue oak) has been variously reported to enhance or suppress understory production. The effects of canopy removal have been reported only for the northern portion of blue oak's range. We removed all blue oaks from 6 plots in the central coast of California and found no significant change in understory biomass over 3 years. Understory herb cover averaged 32.6% on cleared plots, compared to 24.3% on uncut plots, but composition changed little with the exception of an increase in Erodium cicutarium (L.) L'Her. Clearing did not produce the distinctive species composition and forage enhancement under Q. douglasii canopy reported in other studies, an based on comparisons between unmanipulated canopy and adjacent grassland. Our results suggest that the canopy effect could instead be caused by differences in sites occupied by trees. Clearing of Q. douglasii in regions with 50 cm or less of mean annual precipitation is not recommended for increasing forage production.