Element resorption dynamics were studied in three understory species that dominate a well-developed guild of perennial shrubs in a nutrient poor oak forest in Rhode Island, USA. Mean guild resorption efficiencies for nitrogen (N), phosphorus (P), iron (Fe), copper (Cu), and zinc (Zn) were 43%, 40%, 19%, 10%, and 4%. Within the guild, resorption varied markedly among Gaylussacia baccata, Quercus ilicifolia, and Vaccinium vacillans. Efficiency of N and P resorption in Quercus (70%, 59%) was twice that of Gaylussacia (33%, 33%) or Vaccinium (26%, 28%). Variation in resorption efficiency was lowest in Quercus, among species, and lowest in N, among elements. The factors most highly related to resorption were the specific mass and element concentrations of presenescent leaves. Microsite soil fertility was not related to the resorption of any of the elements studied. Because foliar N and P concentrations and absolute contents differed markedly among species before the onset of senescence, but were similar after senescence, a model was developed suggesting the existence of a threshold below which none of the guild species could further reduce foliar N and P levels. The role of niche diversification in the evolution and maintenance of interspecific resorption differences was evaluated.
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Killingbeck et al. (1988) studied this question.