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Hardwood-Conifer Forest Contact Zone in Itasca Park, Minnesota

1945; University of Notre Dame; Volume: 34; Issue: 2 Linguagem: Inglês

10.2307/2421130

1938-4238

Murray F. Buell, William E. Gordon,

Tree-ring climate responses

Which, if either, of these communities can logically be considered climax in the Park area has not been clearly determined. Lee (1924) noted that hard maple (Acer saccharum) is limited to heavier soils and hence, though able to reproduce itself, could not become the climax. Of the spruce-fir (Picea-Abies) type he wrote: . . it seems both possible and probable that it may develop into the true climax of the region. Kell (1938) supported the polyclimax view stating that there are three climax communities: these are: 1. ash-elm-fir on peat, 2. sugar maple-basswood on fine-textured mineral soils, and 3. sprucefir-birch on coarse-textured mineral soils. Pertinent to consideration here also is the fir-basswood climax of Grant (1934), 80 miles east in Itasca County and much farther within the realm of the northern conifer climax. The problem is complicated first of all by the complex of non-climatic factors involved. Sharp, glacial-induced variations in physiography and soil prevail almost everywhere. Disturbing factors, first of fire and later of overgrazing by deer, have left an obvious mark on almost all the plant communities. These factors combine to produce very few areas with a degree of maturity and stability sufficient to warrant climax designation. Superimposed upon this complex of non-climatic factors is the factor of climate itself which complicates the determination and particularly the interpretation of the climax. It seems probable that both forest communities are approaching their climatic limits. By the law of limiting factors, therefore, both communities would hence be more responsive to small changes in climate than would be the case deeper within their respective climatic regimes. As a consequence, the history of the communities can be expected to reflect even the small climatic fluctuations of reecnt time, some of which may have been sufficient to change the successional trend favoring first one community and then the other. The relative immaturity of the area and the responsiveness of the communities to climatic factors together render the usual developmental approach of limited use in determining the climax and may account in part for the variance in conclusions among those who have studied the problem. In the final analysis, the answer to the question of which may be considered climax under the present climatic regime lies not so much in the distribution as in the relative competitive ability of the two communities. Specifically, can one reproduce itself and invade the other under conditions of soil and physiography sufficiently stable to warrant climax designation? With this ques433