February 2017 Reference Conditions and...



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Category: Ecological Research

Title: Fact Sheet: Reference Conditions and Historical Fine-Scale Spatial Dynamics in a Dry Mixed-Conifer Forest, Arizona, USA.

Author: Rodman, K.C.

Subject: Reference Conditions, Spatial Dynamics

Abstract: Reference conditions of forests — including the stand densities, species compositions, and tree spatial patterns prior to Euro-American settlement — are useful to silviculturists and other forest managers when developing pre- scriptions and assessing the efficacy of restoration treatments. Dry mixed-conifer forests cover up to 3 million acres in the southwestern United States, and active management within these systems is commonplace. However, little is known about reference conditions and the natural ranges of variability (NRV) within southwestern dry mixed-conifer forests, particularly with respect to fine-scale spatial patterns. Fine-scale (less than 10 acres) patterns in many southwestern forests are often referred to as a “shifting mosaic” made up of isolated single trees, groups of trees with interlocking crowns, openings, and grassy interspaces. These spatial patterns are dynamic, and are likely driven by the location of safe sites for tree regeneration due to local moisture availability, reduced competition with the herbaceous understory, or small patches of overstory mortality. Tree spatial patterns also influence numerous ecological processes including fine-scale disturbance dynamics (e.g. wildfire and bark beetle-induced tree mortality), tree regeneration, and variability in the understo- ry microclimate (reviewed by Reynolds et al. 2013). In this study, we quantify reference conditions within four dry mixed-conifer stands on the Mogollon Rim, Arizona, improving knowledge of the NRV for these important and biodiverse forests. In a landscape adjacent to the study plots, it was found that wildfires were frequent histor- ically, but widespread fires have not occurred since 1879 due to Euro-American influences, promoting substan- tial changes in forest structure and composition (Huffman et al. 2015).

Date: 2017

Type: Fact Sheet

Source: ERI - Fact Sheet

Identifier: 2 p.

Publisher: Ecological Restoration Institute/NAU

Format: PDF

Language: English