Climatic Effects on Regeneration Trends for Two Columnar Cacti in the Northern Sonoran Desert

Abstract

Abstract A traditional perception of desert vegetation is one of relatively slow change in a consistently harsh environment. More recent studies of population dynamics and paleoenvironmental reconstructions in arid environments have revealed the more dynamic nature of desert vegetation, in both a short-term and long-term perspective. This paper examines relationships of population dynamics to climatic fluctuation and anthropogenic factors in two columnar cactus species in the northern Sonoran Desert. The results underscore the responsiveness of desert plant populations to temporal variability in environmental stresses as well as the influence of temporal scale on our views of population dynamics. I use allometrically determined ages for 327 organ pipe cacti on hillslopes and 473 saguaros on flat sites in Organ Pipe Cactus National Monument, Arizona, to relate regeneration trends for each species to climatic variation in the last century. Residuals representing the deviation of the actual age distribution ...