Drought Influence over Radial Growth of Mexican Conifers Inhabiting Mesic and Xeric Sites

Abstract

Drought is a major constraint of forest productivity and tree growth across diverse habitat types. In this study, we investigated the drought responses of four conifer species growing within two locations of differing elevation and climatic conditions in northern Mexico. Two species were selected at a mesic site (<i>Cupressus lusitanica</i> Mill., <i>Abies durangensis</i> Martínez) and the other two species were sampled at a xeric site (<i>Pinus engelmannii</i> Carr., <i>Pinus cembroides</i> Zucc.). Using a dendrochronological approach, we correlated the radial-growth series of each species and the climatic variables. All study species positively responded to wet-cool conditions during winter and spring. Despite the close proximity of species at a mesic site, <i>A. durangensis</i> had high responsiveness to hydroclimatic variability, but <i>C. lusitanica</i> was not responsive. At the xeric site, <i>P. engelmannii</i> and <i>P. cembroides</i> were very responsive to drought severity, differentiated only by the longer time scale of the response to accumulated drought of <i>P. engelmannii</i>. The responsiveness to hydroclimate and drought of these tree species seems to be modulated by site conditions, or by the functional features of each species that are still little explored. These findings indicate that differentiating between mesic and xeric habitats is a too coarse approach in diverse forests with a high topographic heterogeneity.