. The ecology of delta marshes of coastal Louisiana : a community profile . 50 100 150 200 250 DAYS FROM START OF INCUBATION {JUNE 20) 7/10 8/7 9/15 10/15 11/7 12/6 1/18 2/25 DATE Figure 52. Disappearance of S_. patens litter from litter bags in the Pontchartrain-Borgne basin (data from Cramer and Day 1980). Both of these factors are probably re- flected in this graph. The histogram showing the changing rate for each succes- sive interval of time indicates that the initial rapid rate was declining as early as August before air tenperature dropped significantly. This implies a change in the kin
. The ecology of delta marshes of coastal Louisiana : a community profile . 50 100 150 200 250 DAYS FROM START OF INCUBATION {JUNE 20) 7/10 8/7 9/15 10/15 11/7 12/6 1/18 2/25 DATE Figure 52. Disappearance of S_. patens litter from litter bags in the Pontchartrain-Borgne basin (data from Cramer and Day 1980). Both of these factors are probably re- flected in this graph. The histogram showing the changing rate for each succes- sive interval of time indicates that the initial rapid rate was declining as early as August before air tenperature dropped significantly. This implies a change in the kind of material being decomposed. On the other hand, the rate began to increase again at the end of the experiment when the remaining materials would be most refractory; this coincided with the early spring increase in the ambient tempera- tures. Figure 53 shows mean loss rates of S_. al terniflora detritus from litterbags submerged but susoended off the bottom in a tidal stream, on the surface of a streamside marsh, and on the marsh surface further inland. Decomposition was fastest in flowing water, second where tidal flushing was vigorous, and slowest where the bags tended to be submerged most of the time in stagnant water. The figure also demonstrates the temperature (season- al) effect. Finally, Table 20 summarizes the species-dependency of the decomposition rate. Variability is high, hut I believe the means are fairly reliable indicators of the relative rates of decomposition of different species. S^. al terniflora is the most easily broken down of the grasses, but they all tend to be fairly fibrous and 58
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