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Keywords:

  • Demography;
  • Desert shrub;
  • Ephedra;
  • Larrea;
  • Lifespan;
  • Opuntia;
  • Repeat photography
  • Hickman (1993)

Abstract. The demography of woody desert plants along the Colorado River in Grand Canyon, Arizona, USA, was analyzed using 355 pairs of replicated photographs taken as long ago as 1872. Longevity, recruitment, and mortality were determined for 38 species characteristic of ungrazed desert scrub. Individual plants that survived 100 yr or more included Acacia greggii, Ambrosia dumosa, Atriplex canescens, A. confertifolia, Echinocactus polycephalus, Ephedra spp., Fouquieria splendens, Larrea tridentata, Lycium andersonii, Opuntia acanthocarpa, O. basilaris, O. erinacea, Pleuraphis rigida, and Yucca angustissima. This is the first evidence of long lifespan for most of these species, particularly the succulents. Most of the long-lived species registered overall increases in population during the past century. Only four species with lifespans ≥ 100 yr had a net loss of individuals between 1889 and the present, and only two decreased between 1923 and the present. It seems likely that climatic fluctuations over the past century are largely responsible for these recruitment and mortality patterns; however, nurse plants, predation refuges and other biotic factors may also play a role.