ORIGINAL ARTICLE Twentieth century demographic changes in cirio and cardón in Baja California,

Aim Our purpose was to discern long-term large-scale patterns of survivorship and recruitment of two dominant, charismatic and useful desert plants, cirio [Fouquieriaceae; Fouquieria columnaris (Kell.) Kell. ex Curran] and cardón [Cactaceae; Pachycereus pringlei (S.Watson) Britton & Rose], and to evaluate the effects of physical and human factors. Location The study included 77 sites distributed over c. 13,200 km2 in the northern Vizcaı́no Region of the Sonoran Desert, state of Baja California, México. Method Censuses used identified individuals (n 3780 cirio and 2246 cardón) and were based on repeat photography. Time intervals between censuses ranged from 29 to 96 years, ending in 1996–2002. Earlier repetition (1963) of old photographs at 14 sites allowed analysis of temporal variation. The effect of elapsed time was modelled with Weibull functions for survivorship and linear functions for recruitment. To explain the residual variations, we tested categorical and continuous variables related to substrate, geomorphology, climate an