7Roberts L M,McCulley R L,Burke I C,et al.Indications of deep soil water usage by limber pine (Pinus flexilis) and skunkbush sumac (Rhus aromatica) in Northeastern Colorado:an oxygen isotope study[J].American Midland Naturalist,2004,152:178-182.
8Zavarin E,Cool L G,Snajberk K.Geographic variability of Pinus flexilis xylem monoterpenes[J].Biochemical Systematicas and Ecology,1993,21:381-387.
9Schoettle A W,Rochelle S G.Morphological varination of Pinus flexilis(Pinaceae),a bird-dispersed pine.across a range of elevations[J].American Journal of Botany,2000,87:12,1797-1806.
10Van de water P K,Leavitt S W,Betancourt J L.Trends in stomatal density and 13C/12C ratios of Pinus flexilis needles during last glacial-interglacial cycle[J].Science,1994,164(5156):239-143.