Energy allocation patterns of a sprouting and nonsprouting species of Arctostaphylos in the California chaparral

The r- and K-selection theory was used to generate testable hypotheses about patterns of energy allocation in two chaparral shrubs of different reproductive strategies. Terminal-branchlet vegetative and reproductive biomass of the nonsprouting Arctostaphylos glauca and the sprouting A. glandulosa were sampled in a 23-year-old and a 90-year-old stand of chaparral to test the predictions that: (1) the terminal vegetative growth (g dry weight/m² of areal coverage) would be equal in the two species, in both stands; (2) oven dry weight (g) of reproductive parts/m² of areal coverage would be greater in A. glauca than in A. glandulosa in both aged populations; (3) allocation to reproductive parts by the shrubs in the 23-year-old stand would be greater than (or equal to) that of the 90-year-old shrubs. The amount of terminal vegetative growth was equal for both species in the 23-year-old and the 90-year-old stands. There was no statistically significant difference in the weight of fruits produced by the two species in the 23-year-old stand. However, fruit production by A. glauca was significantly greater than by A. glandulosa in the 90-year-old stand. Fruit production was also significantly greater for the older A. glauca shrubs than for those in the 23-year-old stand. The relationships of rainfall pattern and age of shrubs to fruit production are discussed.