Early Stages of Plant Succession Following Logging and Burning in the Western Cascades of Oregon

Abstract

Vegetative changes were documented for 7 years on permanent milacre plots located in three clearcut logged units in the western Cascade Mountains of Oregon. Plant cover and composition were observed the year prior to logging the old—growth Pseudotsuga menziesii forest, after logging but before burning, and during each of five growing seasons following broadcast slash burning. Total plant cover was 15.2 49.3, and 75.5% in the first, second and fifth years after slash burning, respectively. Invading herbaceous species dominated from the second through fourth growing seasons after burning but by the fifth year residual herbaceous species regained dominance. Differences in disturbance from logging and burning strongly influenced successional trends. In undisturbed soil areas, residual species, such as Acer circinatum, Oxalis oregana, and Gaultheira shallon, dominated. Areas disturbed by logging but unburned supported a wide variety of both residual and invader species. Light to severely burned sites were largely occupied by invaders such as Ceanothus velutinus, Epilobium angustifolium, and E. paniculatum. Although often obscured by varying degrees of disturbance, relationships between early stages of succession and prelogging plant community were discernible. For example, of the species considered characteristic of five undisturbed plant communities, only 13 percent were absent from the plots 5 years after burning. The invaders Ceanothus velutinus, Agoseris grandiflora, and Gnaphalium microcephalum var. thermale were restricted to sites previously supporting rather xeric communities; while Rubus leucodermis and Anaphalis margaritacea were found on plots characteristic of the more mesic communities.

Eighth-year response of Douglas-fir seedlings to area of weed control and herbaceous versus woody weed control

“…Whereas woody plant cover is likely correlated with past woody cover values, herbaceous cover in year five may be dramatically different from cover in years 1 and 2 [5,10,26]. Our results demonstrate that early differences in herbaceous cover can dramatically impact seedling size through year 8, with differences that are continuing to expand.…”

“…Summed cover for woody species in the check treatment increased from 7.5% to 13.4% to 71.3% in years one through three of the study at Summit and from 41.7% to 68.2% to 119.2% at Marcola [25]. We suspect that woody species capable of doing so did not start to reach dominance until years 4 to 5, which is a commonly observed successional trend [10,26,27]. A temporal shift in dominance from herbaceous to woody species would explain the observed increase in volume at year 8 resulting from the woody-only control at Summit absent in year 3.…”

The allelopathic potential of Rhododendron macrophyllum in a western Cascades clearcut

“…It is commonly the dominant species in the shrub stage of secondary succession on burnedover and logged sites (Franklin and Dyrness, 1973;Dyrness, 1973). It may often be present in these cleared areas as a residual species which has regrown from surviving roots (Dyrness, 1973).…”

“…It is commonly the dominant species in the shrub stage of secondary succession on burnedover and logged sites (Franklin and Dyrness, 1973;Dyrness, 1973). It may often be present in these cleared areas as a residual species which has regrown from surviving roots (Dyrness, 1973). As such it has the potential to have a large impact, through both competetion and allelopathy, on slower growing or later arriving species and ultimately on the rate of regrowth of conifer species and re-establishment of the forest.…”

Species composition on reclaimed ski runs compared with unseeded areas

“…Although physical erosion control features, like berms, are often constructed, the re-establishment of vegetative groundcover is critical in reducing runoff and soil loss as it binds soils and increases infiltration rates (Andreu et al 1995, Williams et al 1995, Oliver and Larson 1990, Marks and Bormann 1972. Natural re-establishment of indigenous vegetation in disturbed areas may take years (Curtin 1995, Dyrness 1973, dictating the need for artificial seeding to re-establish vegetative groundcover quickly. In many instances,…”