Factors influencing understory seedling establishment of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) in southeast Wyoming

Publisher Website
Google Scholar
Abstract
Although seedlings of A. lasiocarpa are generally more abundant than those of P. engelmanni in the understory of mature spruce-fir forests throughout the central and northern Rocky Mountains, little information exists concerning environmental or plant factors that may influence the establishment of these 2 conifers. Field measurements in the Medicine Bow Mountains of southeast Wyoming showed that seedlings of A. lasiocarpa had greater photosynthetic rates at low understory light levels and required lower levels of incident radiation for saturation of photosynthesis compared with those of P. engelmanni. However, both conifers occurred in understory locations where total daily solar radiation was equally low (< 2 MJ .cntdot. m-2 .cntdot. day-1) and thus, a lack of light did not appear to be responsible for the low number of P. engelmanni seedlings in the understory. In contrast, seedlings of P. engelmanni were substantially more abundant at locations with thinner litter layers compared with those of A. lasiocarpa. Also, laboratory studies showed that the smaller seeds of P. engelmanni germinated more rapidly and at lower temperatures than seeds of A. lasiocarpa although growth of tap roots on A. lasiocarpa seedlings was greatly initially (.simeq. 200% longer in 2 wk old seedlings) as well as for 10 wk old seedlings (50% longer). The deeper penetrating tap root of A. lasiocarpa seedlings may enable this conifer to establish more abundantly on thick, rapidly drying litter layers that are characteristic of mature spruce-fir forests. In contrasts, establishment of P. engelmanni seedlings may be limited to microsites without a thick layer such as disturbed areas or decomposing wood, where surface drying may occur more gradually throughout the summer. These results are discussed in terms of the potential effects of seedling establishment on the observed patterns in climax vegetation of central and northern Rocky Mountain subalpine forests.

This publication has 2 references indexed in Scilit: