Observations of Well-Developed Podzols on Tundra and of Patterned Ground Within Forested Boreal Regions

Аннотация

In most, if not all, papers and monographs dealing with patterned ground there appears to be an implicit assumption that polygonal and patterned ground phenomena are exclusively characteristic of tundra regions. In rather extensive vegetational sampling in the forest, forest/tundra ecotone, and tundra of central northern Canada, it has been my observation that patterning is a relatively frequent characteristic of soils in at least the northern portion of the boreal forest in that region. This has escaped wider notice simply because the phenomenon is obscured by the thick layer of moss peat and living mosses and lichens, as well as herbaceous species, usually found under a boreal forest canopy. J. C. F. Tedrow (personal communication, September 1971) indicates that he also has observed patterning under forest in northern Canada and northern Scandinavia although the literature on this subject is either very brief or non-existent. At a site some few miles north of Inuvik, I observed during the 1971 summer field season an example of patterned ground formed beneath black spruce forest that had been exposed as a result of a recent fire (probably within the past 5 to 6 years as deduced from the initial stage of vegetational regeneration) .... Although Tedrow's extensive work in arctic soils clearly indicates that podzolization processes are at work in soils of regions northward of the continental forest borders, he indicates that very often these are not as clearly apparent as in the forested regions simply because of the absence or minimal development of the light coloration of the A2 horizon characteristic of well-developed northern forest podzols. That such minimal coloration is not without exception is demonstrated by the soil profiles shown in Figs. 2 and 3; the first from an area about 12.9 km inland (toward the northeast) at the north arm of Pelly Lake (66°02'N, 101°07'W) some 400 kilometres or more north of the forest border at the present day; the second from Winter Lake (64°29'N, 113°10'W) at the northern edge of the forest/tundra ecotone about 200 kilometres northeast of Yellowknife, Northwest Territories. These observations demonstrate clearly that patterning is not exclusively a property of tundra soils nor is podzolization (with a light-colored A2 horizon) an exclusive property of northern forest soils. Much remains to be learned about both processes in the forest, forest/tundra ecotone, and tundra regions, but it is clearly apparent that soil characteristics cannot be taken alone as definitive or conclusive evidence of the former existence of forest or tundra vegetation (i.e., as basis for inferences concerning past climates from data employed in paleoclimatological interpretation). In such instances it is apparent that at least corroborative evidence in the form of macrofossils of tree species or arctic plant species of good climatic indicator value3 should also be used.