Warming in the boreal forest of interior Alaska will have fundamental impacts on stream ecosystems through changes in stream hydrology resulting from upslope loss of permafrost, alteration of availability of soil moisture, and the distribution of vegetation. We examined stream flow in three headwater streams of the Caribou-Poker Creeks Research Watershed (CPCRW) in interior Alaska over a 30-year period to determine (i) how stream flow varied among streams draining watersheds with varying extents of permafrost and (ii) evaluate if stream hydrology is changing with loss of permafrost. The three streams drained subcatchments with permafrost extents ranging from 4% to 53%. For each stream, runoff data were analyzed by separating base and storm flow contributions using a local-minimum method and with analy- sis of flood recession curves. Mean daily runoff during the ice-free season did not significantly vary among streams (mean = 0.57 mmd -1 ), although the watersheds with lower permafrost had a greater contribution of base flow. Across years, flow was variable and was related with summer temperature in the watershed with low permafrost and with precipi- tation in the watershed with high permafrost. With climate warming and loss of permafrost, stream flows will become less responsive to precipitation and headwater streams may become ephemeral. Resume´ : Le rechauffement du climat dans la foret boreale de l'interieur de l'Alaska aura des impacts fondamentaux sur les ecosystemes lotiques par l'entremise de changements dans l'hydrologie des cours d'eau provoques par la disparition du pergelisol dans les pentes, la modification de la disponibiliteen eau du sol et la distribution de la vegetation. Nous avons etudiele debit de trois ruisseaux situes en amont du bassin experimental de Caribou Poker Creeks a l'interieur de l'Alaska sur une periode de 30 ans. L'etude avait pour but de (i )d eterminer de quelle facon varie le debit des ruisseaux qui drai- nent des bassins oule pergelisol occupe differentes superficies et (ii )evaluer si l'hydrologie des ruisseaux change avec la disparition du pergelisol. Les trois ruisseaux drainaient des sous-bassins oule pergelisol occupait de 4 % a ` 53 % de la su- perficie. Pour chaque ruisseau, les donnees d'ecoulement ont eteanalysees en separant la contribution du debit de base et celle du debit d'orage a l'aide de la methode du minimum local et de l'analyse des courbes de decrue. Le debit journalier moyen durant la saison ouil n'y avait pas de glace n'a pas variede facon significative entre les ruisseaux (moyenne = 0,57 mmj -1 ) mais les bassins ouil y avait le moins de pergelisol contribuaient davantage au debit de base. Le debit variait d'une anneeal'autre; il etait relieala temperature estivale dans le bassin ouil y avait peu de pergelisol et aux precipita- tions dans le bassin ouil y avait beaucoup de pergelisol. Avec le rechauffement du climat et la disparition du pergelisol, le debit des cours d'eau va devenir moins sensible aux precipitations et les ruisseaux de tete pourraient devenir saison- niers. (Traduit par la Redaction)
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