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On Competition Between Galium Saxatile L. (G. Hercynicum Weig.) and Galium Sylvestre Poll. (G. Asperum Schreb.) On Different Types of Soil

A. G. Tansley
Journal of Ecology
Vol. 5, No. 3/4 (Dec., 1917), pp. 173-179
DOI: 10.2307/2255655
Stable URL: http://www.jstor.org/stable/2255655
Page Count: 7
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On Competition Between Galium Saxatile L. (G. Hercynicum Weig.) and Galium Sylvestre Poll. (G. Asperum Schreb.) On Different Types of Soil
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Abstract

1. Galium sylvestre germinates on calcareous soil, sandy loam and acid peat, most freely on calcareous soil and least freely on acid peat. It also establishes itself on all the soils employed, even on acid peat, though there reduced to a subordinate position. Some plants maintain themselves on peat in competition with the dominant Galium saxatile for at least six years. 2. Galium saxatile germinates on all the soils employed, but the percentage germination is on the whole lower than is the case with G. sylvestre. The germination rate is lowest on calcareous soils, and of the seedlings produced all become chlorotic and many die. Those which survive and become normally green do not survive competition with G. sylvestre. 3 On acid peat the growth of the seedlings of both species is slow. When more vigorous growth begins that of G. saxatile distinctly surpasses that of G. sylvestre. 4. On sandy loam from a heathy woodland both species germinate freely. In the first set of experiments G. saxatile grew more vigorously than G. sylvestre, when the two were mixed, and became dominant. The relations of the two species resemble those obtaining on peat, but the growth of both species is stronger during the first year. 5. On calcareous soil the growth of G. sylvestre is normal and vigorous from the first, while that of G. saxatile is very slow. All seedlings of the latter species become "chlorotic" and many die. Those which survive recover and establish themselves, but do not survive prolonged competition with G. sylvestre. 6. Competition appears to work through the direct suppression of the shoots of one species by those of the other as a result of the more vigorous growth of the species which is growing on its "preferred" soil. Shoot competition acting in this way appears to be adequate as the cause of the suppression of one species by the other. 7. No evidence of root competition was found, but the experiments are not decisive against it, though the case of the plant of G. saxatile which flourished on the corner of the box of calcareous soil, where its shoot escaped the competition of the shoots of the dominant G. sylvestre, is pro tanto evidence against the effectiveness of root as opposed to shoot competition.

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