Nutrient Budgets of Marsh Plants: Efficiency Concepts and Relation to Availability
1984
Shaver, Gaius R. | Melillo, Jerry M.
The effects of variable N and P availability on nutrient uptake, nutrient recovery from dying leaves, and biomass production in three species of marsh graminoids were studied in a growth chamber experiment. "Availability" was defined as the total amount of N or P added to each pot over the duration of the experiment. The species were Carex lacustris, Calamagrostis canadensis, and Typha latifolia. Responses were evaluated in terms of three "efficiencies": (1) efficiency of uptake, or the proportion of available N or P taken up by the plants; (2) efficiency of recovery, or the removal of nutrients from dying leaves as a proportion of the N or P content of mature leaves; and (3) efficiency of use, or the ratio of total biomass of total N or P mass in the whole plant. In all three species, as N or P availability increased, all three efficiency indexes decreased. There was evidence for N ° P interaction in regulating efficiency of N or P uptake, but not the other two indexes. Implications for ecosystem nutrient cycling are discussed, with the conclusion that, as nutrient inputs to an ecosystem increase, nutrient losses from the system and nutrient turnover in the vegetation should also increase.
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