Natural variability in forests of the Grand Canyon, USA
The authors reconstructed historical forest tree structure of ponderosa pine-dominated sites in the Grand Canyon to current species composition, tree structure and regeneration. They also considered the interacting effects of climate, fire, grazing, and other disturbance on any changes in forest structure and composition.
Both climate fluctuations, fire suppression, and land use (i.e. grazing, timber harvest, etc.) have increased the tree densities of forests in Grand Canyon National Park., although the patterns of composition and regeneration varied along fire regime and elevational gradients. In forests where fire has been suppressed long-term, sites are dense and dominated by seed-reproducing conifer species, whereas more frequent fire site regeneration is dominated by sprouting species in the understories of open pine forest.