. Bio-ecology. Plant ecology; Animal ecology; Botany; Ecology; Zoology. REACTION IN WATER 95 (c) emergent. These stages of the hydrosere may be assigned with ahiiost equal propriety to land or water, though developmentally they are an intrinsic part of land climaxes. Since this is largely an out- come of the shallowing effect of plant and animal matter, such accumu- lation has already been considered under land reactions. Reaction upon the medium belongs properly to the consideration of the w^ater. The same is true of influences on the bottom in sluggish rivers and the larger lakes with silt (
. Bio-ecology. Plant ecology; Animal ecology; Botany; Ecology; Zoology. REACTION IN WATER 95 (c) emergent. These stages of the hydrosere may be assigned with ahiiost equal propriety to land or water, though developmentally they are an intrinsic part of land climaxes. Since this is largely an out- come of the shallowing effect of plant and animal matter, such accumu- lation has already been considered under land reactions. Reaction upon the medium belongs properly to the consideration of the w^ater. The same is true of influences on the bottom in sluggish rivers and the larger lakes with silt (terrigenous) bottom. The small floating plants and animals are properly considered in relation to both bottom and the medium itself. Small Lakes and Ponds Accumulation and Decomposition. In its general features, accumu- lation in shallow still water resembles that on land, marsh and swamp. Pig. 19.—View in Little Barren (Mile 474, 760 kilometers from The Pas, Hudson Bay Railway), showing tundra vegetation over several feet of frozen sphagnum. (Photo by V. E. Shelford.) forming the connection between the two. However, there are several important differences, as is well known. One of these is that detritus is sometimes transported and deposited far beyond its place of origin, another that excrement plays a larger part in consolidation, and a third is the retarding of decomposition and the emphasis upon anae- robic processes. Furthermore, calcareous and chitinous skeletons may accumulate to the point of constituting a definite layer. The nature of the filling process is related to temperature and length of season and is different in different climates. Tundra may overlie deep sphagnum deposits resulting in part from failure of the dead plant bodies to decompose. An area of wet tundra is traversed by the Hudson Bay Railway, and the railway itself rests on frozen sphagnum extending to a depth of as much as 20 feet ( meters) near the southern tundra edge and to 7 or 8 feet (
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