Succession of boreal forest spider assemblages following wildfire and harvesting
To test whether spider succession following harvest differed from succession following wildfire, spiders were collected by pitfall trapping and sweep netting over two years in aspen-dominated boreal forests. Over 8400 individuals from 127 species of spiders were identified from 12 stands representing three age-classes (stand origin in 1995, 1982, and 1968) and two disturbance types (wildfire and harvesting). The diversity of spider assemblages tended to be higher in fire-origin stands than in harvest-origin stands; the youngest fire-origin stands also supported more even distributions of spider species. Spider assemblages responded quickly to wildfire and harvesting as open habitat specialists colonized stands within one year after disturbance. Many web-building species common to older forests either survived harvesting, or re-colonized harvest-origin stands more rapidly than they re-colonized fire-origin stands. Cluster analyses and DCA ordination show faunal convergence by ca 30 years after wildfire and harvesting; trajectories in re-colonization, however, differed by disturbance type as the succession of spider assemblages from fire-origin stands lagged behind spider succession in harvest-origin stands. Comparison with cluster analyses using vegetation data and abiotic site conditions suggest spider assemblages recover from harvesting and fire more rapidly than do a variety of other site characteristics. Several spider species (e.g. Gnaphosa borea Kulczyński, Pirata bryantae Kurata, Arctosa alpigena (Doleschall)) appear dependent on some of the conditions associated with wildfires as they were absent or rarely collected in harvest-origin stands.
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Document Type: Original Article
Publication date: August 1, 2000