Halpern, Charles B.; Franklin, Jerry F. 1989. Understory development in Pseudotsuga forests: multiple paths of succession. In: Ferguson, Dennis E.; Morgan, Penelope; Johnson, Frederic D., comps. Proceedings--land classifications based on vegetation: applications for resource management; 1987 November 17-19; Moscow, ID. Gen. Tech. Rep. INT-257. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station: 293-297.
Vegetation changes after catastrophicdisturbance commonly follow multiple pathways,reflecting variation in initial community composi-tion, intensity of disturbance, or availability ofpropagules. In this paper we examine patterns ofunderstory development during 21 yr of successionin logged and burned Pseudotsuga forests in thewestern Cascade Range, Oregon. We use detrendedcorrespondence analysis ordination to assess thesuccessional pathways of six forest communitiesexposed to a gradient in disturbance. We then useEuclidean distances between pre- and post-disturbance samples in ordination space to evaluatethe resistance and resilience of communities.DCA ordination reveals multiple paths ofsuccession characterized by 1) initially rapidfloristic change away from pre-disturbancecomposition, followed by gradual return and 2)increasing compositional change with disturbanceintensity. Community resistance and resiliencereflect interactions between disturbanceintensity and the life history traits of dominantresidual and invading species.