Phenology of Larrea divaricata in the Tucson Region

Yang, Tien; Abe, Y.

Phenologies of sample populations of the characteristic warm desert shrub, Larrea divaricata Cav., were studied at several field stations between the Tanque Verde Mountains and the Silver Bell Mountains. Weekly, biweekly, monthly, and quarterly observations made since June, 1972 were recorded under (1) leaf initiation, (2) stem elongation, (3) flower buds, (4) flowering, (5) maturing fruits, (6) mature fruits, and (7) foliage condition. When this information is appraised against the fluctuating temperature- precipitaton regime at each station, a pattern of specific phenological attributes emerges for the species. Vegetatively, Larrea continues to initiate new leaves and apical stem growth throughout the year regardless of temperature and moisture extremes. The presence of flower buds is nearly continuous but varies greatly site jo site. Generally, their initial appearance in winter spring seems to be more closely associated with populations which have sustained the greatest loss of foliage. The frequency, duration, and abundance of flowering are apparently temperature controlled in the spring and moisture controlled in the summer. Maturing and mature fruits may be found on individuals of some populations during most of the year. However, their presence and number are not necessarily indicative of the amount of viable embryos and mature seeds they contain.

Phenology of Larrea divaricata in the Tucson Region

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