The amount of rain and snow is influenced by elevation. More moisture occurs toward the higher elevations when considered on an average over hundreds to thousands of years as a part of a climatic time scale. Moisture can be considered as influencing the pattern for plant growth spread over several decades when considered on an ecological time scale.
Grasses, forbs and trees were burnt during the La Mesa fire in 1977. Photo by Terry Foxx
Although first to grow back, different species of grasses and forbs may come to dominate over several years. For example false tarragon was not initially present in surveyed sections of Burnt Mesa. It then became the most commonly seen forb during the next thirty years. In contrast a species of geranium remained present but relatively uncommon throughout these years. Finally, Bahia dissecta is a plant that stands out with its yellow flowers but has disappeared in many areas.
One lone tree (right side of photograph) was growing 21 years after the forest fire in what otherwise was an open field. Photo by Terry Foxx
Ponderosa were the most commonly seen tree prior to the La Mesa forest fire. The extensiveness and intensity of the forest fire varied from area to area and this determined the survival potential of the trees. Trees growing closely together in clusters were killed during the fire. A partially burnt tree may have taken several years to die.
Twenty to 30 years passed for most of the trees to be clearly replaced by fields of grasses and forbs.
The dominant species of grasses and forbs had changed by 2011, 34 years after the forest fire. However young ponderosa trees now are beginning to grow in the area. Five trees can be seen in the distance. Photo by Terry Foxx
However young ponderosa trees now are becoming visible after thirty years and are scattered across grassy fields. Trees may become the dominate species in another hundred years.
Instead of occasional trees scattered among grasses, occasional grasses may be scattered among trees in a maturing forest. Future climate, forest fires, and elk population will influence the pace of this change back to forest.