Recovery patterns of three chaparral shrub species after wildfire

Abstract

In a mature, even aged stand of mixed chaparral, Rhus laurina (facultative resprouter) had consistently higher water potentials and deeper roots than Ceanothus spinosus (facultative resprouter) and Ceanothus megacarpus (obligate seeder). For two years following a wildfire, the same stand of chaparral had resprouts with higher survivorships, predawn water potentials, stomatal conductances, photosynthetic rates and shoot elongation rates than seedlings. Supplemental irrigation of seedlings during summer months removed differences between resprouts and seedlings suggesting that the cause of such differences was limited water availability to the shoot tissues of seedlings. After two years of postfire regrowth, mean seedling survivorship for the obligate seeder (C. megacarpus) was 42%, whereas seedling survivorship for facultative resprouters was only 18% (C. spinosus) and 0.01% (R. laurina). Our results are consistent with the hypothesis that lack of resprouting ability among obligate seeders is offset by an enhanced ability to establish seedlings after wildfire, allowing obligate seeders to maintain themselves in mixed populations through many fire cycles.

Keywords: Ceanothus; Chaparral; Rhus; Root depth; Seedling survival.