Abstract
Leaves of red mangrove ( Rhizophora mangle L.), needle rush ( Juncus roemerianus Scheele) and turtlegrass ( Thalassia testudinum Banks ex König) from litterbags were sampled by removal of pieces of measured volume, rather than, or in addition to, using the entire contents of bags as unit samples. Dead mangrove and turtlegrass leaves decomposed rapidly, approaching the point of full breakdown to fine-particulate and dissolved state within 6 months after litterbag placement. By contrast, net loss of dry matter from rush leaves after 2 years was about 50% or less. Net immobilization of nitrogen (0.1–0.7 mg cm −3 leaf month −1 ) occurred in mangrove leaves decaying in the summer, as established by use of the standard-volume sampling method. Rush and mangrove leaves decreased sharply in mean mass-ratio of carbon to nitrogen during decomposition, from about 75–125:1 to about 30–40:1. Turtlegrass leaves were consistently low in mean ratio of carbon to nitrogen (15–18:1). The measured-volume sampling, in comparison to whole-bag results, revealed that early losses of pieces of leaf by fragmentation were negligible for mangrove leaves. However, for turtlegrass leaves, which do not immediately die and decompose upon detachment, loss of leaf portions was apparently a major contributor to total dry-matter output. Rush leaves exhibited erratic rates of loss of dry matter as assessed with the measured-volume technique; significant increases in density of dry matter were recorded, apparently due to increases in ash content and to active infiltration by cyanobacteria.
Published Version
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