. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Figure 101. — Fires in Pinus ponderosa forests on the east slope of Oregon's Cascade Range may give rise to communities domi- nated by sclerophyllous shrubs such as Arctostaphylos patula and Ceanothus uelutinus. Figure 102. — Dense, stagnated thickets of Pinus pon- derosa saplings are common on shal- low, stony soils in the Pinus ponderosa Zone; these are frequently attributed to the exclusion of periodic, natural wildfires during the last 50 years. 5$; _ __ fti- -4-. ated by burning aids in germin
. Vegetation of Oregon and Washington. Botany Oregon Ecology; Botany Washington (State) Ecology. Figure 101. — Fires in Pinus ponderosa forests on the east slope of Oregon's Cascade Range may give rise to communities domi- nated by sclerophyllous shrubs such as Arctostaphylos patula and Ceanothus uelutinus. Figure 102. — Dense, stagnated thickets of Pinus pon- derosa saplings are common on shal- low, stony soils in the Pinus ponderosa Zone; these are frequently attributed to the exclusion of periodic, natural wildfires during the last 50 years. 5$; _ __ fti- -4-. ated by burning aids in germination of seeds of these species (Gratkowski 1962; Johnson 1961). In the absence of fire, these species apparently perpetuate themselves, at least in pumice soil areas, by vegetative regeneration (Dyrness 1960). Dense, stagnated stands of Pinus ponderosa saplings are common throughout the zone (fig. 102), especially on shallow, stony soils of low productivity. These stands have been at- tributed to fire exclusion during the past half century (Weaver 1955, 1959, 1961). It is claimed that, previously, periodic fires regu- lated amounts of advance regeneration and re- sulted in the open, grassy, parklike stands that early settlers described. However, Daubenmire and Daubenmire (1968) feel that the dense, patchy, episodic reproduction in their grassy Pinus ponderosa associations cannot be com- pletely attributed to fire control since a patchy structure is absent in Pinus/Symphori- carpos and Pinus/Physocarpus stands. Fur- thermore, it is possible that many Pinus pon- derosa thickets actually originated with fires. Brayshaw (1965) observed that burning im- mediately preceding a heavy seed year assisted establishment of unusually numerous pine seedlings by greatly reducing competition from other vegetation. West (1968) reported that at least 15 percent of Pinus ponderosa seedlings develop from unrecovered rodent caches in central Oregon (fig. 103). In many areas, there is a strong
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