Category: Ecological Research
Title: The Role of Fire in the Establishment and Spread of Nonnative Plants in Arizona Ponderosa Pine Forests: A Review
Author: * McGlone, C.M. , * Egan, D.
Subject: Ecological Restoration, Invasive, Ponderosa pine (Pinus ponderosa)
Abstract: Arizona ponderosa pine (Pinus ponderosa) forests have undergone dramatic changes since the late nineteenth century. Management practices such as fire exclusion have resulted in increased surface and tree crown fuel loads. Consequently, large and severe wildfires have been occurring more frequently in the ponderosa pine forests of Arizona. Furthermore, prescribed fire, both with and without tree thinning, is being applied to ponderosa pine forests to mitigate the risk of wildfire. Increasingly, nonnative plant species are spreading into burned forests regardless of fire type. In this article, we review recent literature on nonnative establishment in the post-fire plant community. Current research suggests an increasing risk of nonnative establishment is associated with increasing fire severity. Furthermore, wildfires seem more likely to promote nonnative species establishment than prescribed fires. The results are inconsistent, however, with some high-severity fires having few nonnatives and some prescribed fires strongly promoting invasion. Further research is needed to understand the mechanisms of invasion. In the 23 studies we examined, a total of 43 nonnative plant species were reported in post-fire communities. Of these, only three species were listed as noxious in Arizona: field bindweed (Convolvulus arvensis), Dalmatian toadflax (Linaria dalmatica), and Scotch cottonthistle (Onopordum acantium). Cheatgrass (Bromus tectorum), Kentucky bluegrass (Poa pratensis), and common mullein (Verbascum thapsus) were the most commonly observed species in burned areas, regardless of natural or anthropogenic ignition. Generally, nonnative presence increased after fire, but abundance of these species remained low (< 10% cover). Changes in nonnative populations reported in Arizona are consistent with those seen in ponderosa pine forests of other regions, with nonnatives tending to increase with increasing fire severity.
Source: Journal of the Arizona-Nevada Academy of Science
Publisher: Arizona-Nevada Academy of Science, http://www.geo.arizona.edu/anas/janas.html