Category: Ecological Research
Title: Posttreatment Tree Mortality After Forest Ecological Restoration, Arizona, United States
Author: * Fule, P.Z. , * Roccaforte, J.P. , * Covington, W.W.
Subject: Mortality, Ecological Restoration, Fire ecology, Fuels, Gambel Oak (Quercus gambelii), Ponderosa pine (Pinus ponderosa), Tree thinning
Abstract: Pineoak forests are of high ecological importance worldwide, but many are threatened by uncharacteristically severe wildfire. Forest restoration treatments, including the reintroduction of a surface fire regime, are intended to decrease fire hazard and emulate historic ecosystem structure and function. Restoration has recently received much management attention and short-term study, but little is known about longer-term ecosystem responses. We remeasured a replicated experimental restoration site in the southwestern United States 5 years after treatments. Basal area, tree density, and canopy cover decreased in the treated units at a faster rate than in controls. Delayed mortality, not evident right after treatment, decreased density modestly (13(percent) in treated units and 10(percent) in controls) but disproportionately affected large trees (large ponderosa pines were those with diameter at breast height [dbh] 37.5 cm; other species dbh 20 cm). In treated units, 10.9 large trees ha1 died, whereas 6.2 trees ha1 died in control units. Compared with reference conditions, the experimental blocks remained higher in pine density and, in three of the four blocks, in basal area. Pine trees grew significantly faster in treated units than in controls, enough to reach the reference level of basal area in 6 years. Although mortality of large trees is a concern, the treated units have vigorous growth and low density, indicating that they will be relatively resistant to future drought and fire events. Similar treatments may be beneficial in many areas of the United States and in related pine-oak ecosystems elsewhere.
Source: Environmental Management
Publisher: Springer New York