Ecotonal changes and altered tree spatial patterns in lower mixed-conifer forests, Grand Canyon National Park, Arizona, USA
The authors looked at species specific patch development, establishment, and the effects of climate and/or disturbance regimes, including fire suppression, within ecotones of mixed-conifer and ponderosa pine ecosystems.
The authors found that along the mixed-conifer/ponderosa pine ecotone there has been a shift toward increasing mixed-conifer forest, especially white fir and other shade-tolerant and fire-intolerant species in historical ponderosa pine stands due to fire suppression. Pole-sized white fir were clumped at all patch sizes due to a lack of thinning by fire. This has caused dense thickets of white fir that do not permit ponderosa pine seedlings from regenerating.