Inter-specific transpiration differences between aspen, spruce, and pine in a sky-island ecosystem of the North American Great Basin

•Tree transpiration response to drought may change by species in sky-island ecosystems.•Sap flow decline of aspen under soil droughts was linked to shallow soil moisture.•Cool-season precipitation reduced growing-season sap flow decline of conifers.•Spruce and pine rapidly downregulated canopy conductance with decreasing soil water.•Aspen canopy conductance was insensitive to soil drying compared to spruce and pine.