Category: Ecological Research
Title: Comparison of Historical and Contemporary Forest Structure and Composition on Permanent Plots in Southwestern Ponderosa Pine Forests
Author: Moore, M.M., * Fule, P.Z. , * Covington, W.W. , * Crouse, J.E. , * Huffman, D.W.
Subject: Ponderosa pine (Pinus ponderosa), Spatial Dynamics, Stand Treatment, Pre-settlement
Abstract: We compared historical (19091913) and contemporary (19971999) forest structure and composition on 15 permanent plots in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) forests of Arizona and New Mexico. We used the same sampling methods as in the early 1900s and compared stand density, diameter distributions, species composition, and broad age classes from the two periods. Stand density (trees - 9.14 cm dbh) significantly (P 0.001) increased on plots from an average of 77.4 trees per plot (s = 49.9) at plot establishment in 19091913 to 519.1 trees per plot (s = 252.3) at remeasurement in 19971999. Basal area significantly (P 0.001) increased from 8.0 m2 per plot (s = 3.5) to 28.5 m2 per plot (s = 10.1). Contemporary tree diameter distribution shifted toward smaller size classes as demonstrated by a significant (P = 0.001) decrease in quadratic mean diameter from 38.5 cm (s = 7.5) in 19091913 to 28.6 cm (s = 7.1) in 19971999. Broad age classes yielded an average of 61.5 (s = 49.5) residual live trees classified as blackjack ponderosa pine (P. ponderosa 150 years) and 13.3 (s = 11.9) yellow pine (P. ponderosa 150 years) in 19091913. In 19971999, 416 live trees (s = 229.6) were blackjack and 57.2 (s = 28.5) trees on average were yellow pine. Twelve of the 15 plots were not invaded by other tree species (remained pure ponderosa pine type), while composition shifted slightly on three plots toward more shade-tolerant and fire-intolerant species. Ninety-one percent of the historically (19091913 or older) mapped tree structures (live trees, snags, logs, stumps, etc.) were relocated, which suggested that the forest reconstruction field techniques are reliable within 10(percent). Dramatic increases in tree densities may represent an increased potential for bark beetle epidemics and stand replacing wildfire over large areas in the Southwest.
Source: Forest Science
Publisher: Society of American Foresters, http://www.safnet.org/