MAP A: The three sides of Cerro Grande peak.
Amateur Naturalist: A stage called Cerro Grande PeakBy ROBERT DRYJA
Cerro Grande is one of the peaks that form the perimeter of the Valles Caldera volcanic crater. Two factors make the Cerro Grande one of the more interesting peaks to visit. It has three flanks. The positioning of these flanks has resulted in different kinds of forest growing on them. The second factor is the change in elevation from its base to its summit. This additionally results in several kinds of plant communities. The variations in plant communities in turn result in variations in the associated animal communities. The trail to the top of Cerro Grande Peak makes all this variety accessible.
Cerro Grande peak can be considered as a geologic stage. It will change only slowly over many thousands of years and is the setting for everything else that occurs. Forest fires are like the curtains for this geologic stage, opening up a new setting every several years.
Climate and weather are like stage lighting. Just as changing lighting levels have short term effects during a play, climate and weather have effects on plants and animals from month-to-month and year-to-year in between forest fires.
The three flanks of Cerro form roughly triangular areas. The western flank descends into the Valle Grande and had the densest forest of the three flanks before the Las Conchas fire. It also has felsenmeer boulder fields. The eastern flank slopes down to the Canon de Valle creek bed. The south facing flank has a wedge shaped central slope that becomes the Frijoles creek bed. There is a 1,600 foot change in elevation from the floor of the Valle Grande to the summit of Cerro Grande along the western flank. The elevation change is 1,200 when hiking up the south slope.
The south flank has the more distinctive plant communities. It has a grassy meadowland toward the summit, unlike the other two flanks. Water from rain and snow moisture becomes more abundant as it moves downward and accumulates toward Frijoles stream bed. This increased moisture supports more shrub and tree growth. The south facing slope also receives more direct sunlight compared to the other two slopes.
There have been two forest fires in the past eighteen years. Each has acted as an opening curtain for a new scene on Cerro Grande.
The Cerro Grande forest fire in 2000 started at the summit of the mountain in the grassy meadowland. It initially burned downhill with little breeze to strengthen it. The result was a low intensity fire passing through grasses and dispersed woodland. This however changed after a day. The fire entered the denser forest area at a lower elevation nearer Frijoles Creek. The wind speed additionally increased significantly. A moderate to high intensity fire developed in the area toward Highway 4 and Frijoles Creek. The resulting out-of-control wild fire became one of the largest and most damaging forest fires known.
MAP C: The Las Conchas fire in 2011 had little effect as a low intensity burn for the southern and eastern flanks of the Cerro Grande, (light/dark green areas). However it was a moderate to high intensity burn on the western flank. Trees that had not burnt in 2000 were growing more densely and the fire proceeded upslope into them, (arrow points yellow/red areas).The western flank of the Cerro Grande was not burnt in 2000. Instead it was burnt as part of the Las Conchas forest fire in 2011.
This was a medium to high intensity forest fire moving along the western flank. It changed to a low intensity fire as it passed over the southern flank. Plant communities were not growing in dense forests on the southern flank after the Cerro Grande fire and were not greatly changed by this second fire.
We will explore five ecological settings that are played out the Cerro Grande stage in our coming essays. These will be part of a play called “A Hike to the Top”.
MAP B: The fire in 2000 was a low intensity burn (blue) primarily on the eastern and southern flanks of the Cerro Grande, (solid arrow). Some moderate to high intensity burning (yellow/red) occurred on the southernmost flank in the area of Highway 4, (dashed arrow).