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Individual Highlight

Remnant Old-growth Ponderosa Pine Forests Provide Insights on Spatial Patterns

Photo of A Ponderosa pine stand in the southwestern U.S.
A Ponderosa pine stand in the southwestern U.S. Snapshot : Researchers are increasingly recognizing that ponderosa pine forests naturally occur in clumps of trees with isolated single trees in a matrix of non-forested openings. This spatial pattern is important in sustaining ecological processes such as fire spread, tree growth and regeneration, and creates biodiversity and wildlife habitat; yet, most past studies have examined spatial patterns on small plots, which underestimates the sizes of tree groups and openings.

Principal Investigators(s) :
Sieg, Carolyn H. Iniguez, Jose
Baggett, Scott 
Research Location : Long Valley and Fort Valley Experimental Forests, Arizona, USA??
Research Station : Rocky Mountain Research Station (RMRS)
Year : 2019
Highlight ID : 1582


The spatial pattern of trees and open spaces influences many ecological processes in dry conifer forests. Understanding and replicating historical spatial patterns is important to create forests that are resilient to fire and other disturbances. USDA Forest Service scientists stem-mapped all ponderosa pine trees that were greater than 40-centimeters (about 16 inches) diameter breast height within two large old growth ponderosa pine study sites (Long Valley: 73 hectares, about 180 acres; and Fort Valley: 32 hectares, or about 79 acres) with different soils and tree densities in northern Arizona. Trees were clumped into different sized groups. Most tree groups were small, two-to-four trees, with a few large groups of up to 113 trees. When tree densities were equal, the spatial patterns were very similar between the two sites, suggesting that tree spatial pattern variability is a function of tree densities and only indirectly related to site productivity. Although both sites were dominated by small openings, most of the open area was found within a few large openings. The large plots allowed the scientists to capture a larger range of tree and opening spatial patterns compared to previous studies to provide new insights on spatial heterogeneity that can inform management of this important forest type.

Forest Service Partners

External Partners

  • James Fowler, RMRS (volunteer)

Program Areas