SEEDLING GROWTH AND SURVIVAL OF RED AND WHITE FIR IN A SIERRA-NEVADA ECOTONE

Relative demographic performances (an integrated measure of germination and survivorship over time) suggest that: 1) open/xeric microhabitats within the ecotone favor white fir Abies concolor over red fir Abies magnifica; 2) both open/mesic and shaded/xeric microhabitats favor red fir over white fir; and 3) shaded/mesic microhabitats are equally favorable for both species. Red fir seedlings were consistently heavier than white fir seedlings, in part a result of the 2.5 × greater caloric content of red fir seed. Relative growth rates were similar for both. Allocation of photosynthate to roots was greater for red fir, a result contrary to the expected pattern, given that white fir occurs at more xeric, lower elevations than red fir. -Authors