HYDROLOGICAL RESPONSE OF THE MONTEZUMA CYPRESS IN THE FOREST GALLERY OF THE SAN PEDRO MEZQUITAL RIVER, DURANGO

Abstract

Cypress is the dominant species in the San Pedro Mezquital River (SPMR). In Mexico there is a lack of information about the response of cypress to a modified stream volume, as is the case of the SPMR, where dams were built from 1950 to 1989. The gauge stations located in the tributaries of the SPMR are recording artificial flows from dam releases in the growing season. The objective of this study was to analyze the association between annual radial growth and seasonal flow. A ring-width chronology was developed from increment cores collected in a 20 km transect along the SPMR. A significant association was observed between the “El Saltito” gauge station and the cypress ring-width chronology (r = 0.72, n= 16, 1967-1986, p<0.001) during the March-September period. A similar response function was obtained for other close gauge stations. If the climatic response of the cypress is to the accumulated March-September flow, then this could suggest a strong capability of the species to adjust its physiology to water availability in that period. Given the availability of hydrological infrastructure for irrigation purposes linked to socio-economical interests, it seems very difficult to return to “natural” flow conditions; however, it should be allowed an ecological stream flow to ensure the functioning of the riparian ecosystem and promote protection and restoration measurements when required.