Vulnerability to drought-induced cavitation of riparian cottonwoods in Alberta: a possible factor in the decline of the ecosystem?

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Abstract
Vulnerability of xylem to loss of hydraulic conductivity caused by drought-induced cavitation was determined for three riparian cottonwood species in Lethbridge, Alberta: Populus deltoides Bartr., P. balsamifera L., and P. angustifolia James. These species suffered 50% loss of hydraulic conductivity in one-year-old stem segments when xylem pressure potential fell to –0.7 MPa for P. deltoides and –1.7 MPa for P. balsamifera and P. angustifolia, making them the three most vulnerable tree species reported so far in North America. The possible contribution of drought-induced xylem dysfunction to the decline of riparian ecosystems in dammed rivers is discussed.