Taxonomic uniformitarianism: The problem with shoot/root ratios of peats
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The ratio of shoot to root debris is readily measured in both ancient and modern peats. Several ecological causes of shoot-poor peats have been suggested, but these are based on comparisons between taxonomically dissimilar peat-forming swamps. Here we evaluate the ecological significance of shoot/root ratios in taxonomically similar, yet ecologically variable communities: mangrove swamps. Our preliminary data indicate that all mangrove peats are shoot-poor regardless of environment of deposition. The shoot-poor nature of mangrove peats may be the result of some factor which is universally present in mangrove swamps and does not vary with local environment. We discuss the possibility that the growth habit of mangroves species themselves may account for the scarcity of aerial debris in mangrove peats. For example, mangrove species tend to have a larger portion of their living biomass as roots when compared to non-mangrove tree species. Further, mangrove species tend to form root mats which would serve to exclude aerial debris from sub-surface layers until aerobic degradation is complete. Neutral pH, which occurred in both the freshwater and saline mangrove localities studied, may also contribute to the production of shoot-poor peats. Since freshwater, shoot-rich peats do occur, we conclude that processes of peat formation vary. Universal statements correlating environments of deposition to peat characteristics should be applied with caution. 1989.
