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Positive versus Negative Interactions in a High Alpine Block Field: Germination of Oxyria digyna Seeds in a Ranunculus glacialis Community
Arctic and Alpine Research
Vol. 25, No. 3 (Aug., 1993), pp. 201-206
Published by: INSTAAR, University of Colorado
Stable URL: http://www.jstor.org/stable/1551814
Page Count: 6
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Positive interactions within species aggregations have been suggested as particularly important for increasing germination and survival probabilities of plants in the adversive environment of high alpine block fields. One often-cited example is the elevated temperature and moisture levels in cushion plants, which increases the probability of germination as compared to open ground. However, it is not clear how this applies to plant communities with more erect species. Seeds of Oxyria digyna were sown in close proximity to resident Ranunculus glacialis individuals, and in cleared microsites to test whether positive or negative interactions occur in this kind of high alpine block field plant community. Seeds sown in 1988 showed a higher germination in cleared than in occupied microsites the year after, while no differences were seen for seeds sown in 1989. Ground surface temperature measured in 1990 showed a lower temperature under the resident individuals, which is proposed as a mechanism for the difference in germination found for seeds sown in 1988. Air temperature and precipitation data suggested that 1990 was a warmer and sunnier year than 1989, which could explain why the results from the 2 yr differed. The data show that interactions in this plant community vary from neutral to negative, whereas no evidence for positive interactions was obtained.