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Remnant old-growth ponderosa pine forests provide insights on spatial patterns

Date: August 06, 2019

Some of the last remaining old-growth ponderosa pine occurs in Long Valley and Fort Valley Experimental Forests in Arizona. Research quantifying the spatial patterns of both trees and openings provides valuable insights for managers designing restoration


Old-growth ponderosa pine forests in Long Valley and Fort Valley Experimental Forests provide a window into historical spatial patterns of trees and non-forested openings.
Old-growth ponderosa pine forests in Long Valley and Fort Valley Experimental Forests provide a window into historical spatial patterns of trees and non-forested openings.

Background

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.

Research

We stem-mapped all ponderosa pine trees >40 cm (~16 in.) diameter breast height (DBH) within two large old growth ponderosa pine study sites (Long Valley (73 ha) and Fort Valley (32 ha)) with different soils and tree densities in northern Arizona, USA. Trees were clumped into different sized groups. Most tree groups were small (2-4 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. Our large plots allowed us 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.

Key Findings: 

  • Large remnant old-growth ponderosa pine forests within Arizona experimental forests revealed that trees occur in variable-sized groups up to 122 trees and scattered single trees.
  • Non-forested openings were mostly small, but most of the open area was found within a few large openings.
  • Understanding spatial patterns of groups of trees, single trees and non-forested openings provides insights on incorporating this variability in restoration projects.

Featured Publications

Iniguez, Jose ; Fowler, James F. ; Moser, W. Keith ; Sieg, Carolyn H. ; Baggett, Scott ; Shin, Patrick , 2019