Litterbags, leaf tags, and decay of nonabscised intertidal leaves

Like most plants with perennial rhizomes and annual shoots, Spartina alterniflora does not abscise its leaves. This brings into question the appropriateness of commonly used litterbag methods for study of natural decomposition of S. alterniflora shoots. We compared decay phenomena for S. alterniflora leaves that were either (i) tagged and left in the natural standing position or (ii) cut and placed in litterbags on the marsh sediment at the same site. Rates of loss of mass and leaf area were similar between standing and cut leaves, but distinct differences were detected between leaf types for the carbon to nitrogen ratio and measures of microbial mass and activity. For example, bacterial standing crop was 4 to 67 times greater for cut leaves (though bacterial cells were 9 to 22 times less active ( 3 H-thymidine incorporation/cell)), and fungal living standing crop (ergosterol content) was 5 to 9 times greater for standing leaves. In areas such as southern temperate zones, where shoots are not pushed onto the sediment by ice and snow, it is better to avoid altering the natural positioning of leaves that are not abscised in studies of shoot decay because (i) standing-dead shoots can harbour active microbial assemblages and (ii) shunting directly to the sediment phase can yield an artificial image of microbial–chemical dynamics.