Fire enhances weed invasion of roadside vegetation in southwestern Australia

Abstract

We documented the invasion of native vegetation by exotic species after fire. The study was conducted in linear remnants of sclerophyll woodland along a highway in southwestern Australia. Weeds spread into the remnants mainly from the roadside, while their expansion was less marked from the opposite direction (fenceside). The number of weed species, and their frequency and cover increased after the fires, while the abundance of native species often decreased. The impact of the fires was still evident 7 years later, while the unburnt controls remained almost unchanged. The most abundant weeds were the perennial grasses Eragrostis curvula and Ehrharta calycina. Since grasses are an insignificatn component of sclerophyll vegetation, their abundance is likely to increase the fire proneness of the vegetation. We advocate restrictions on the frequency of burning and on further narrowing of these corridors.