Autecology of Empetrum nigrum and Empetrum eamesii on the Avalon Peninsula, Newfoundland

Dupuis, Sylvie Mona (1988) Autecology of Empetrum nigrum and Empetrum eamesii on the Avalon Peninsula, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Empetrum nigrum L. is a common evergreen shrub in Newfoundland where it forms extensive coastal heathland communities. Empetrum eamesii Fern. & Wieg. is an endemic to the Gulf of St. Lawrence and is most abundant in Newfoundland; this dwarf shrub species forms subarctic heath communities on the most elevated and windswept areas in Newfoundland. -- A comparative autecological study was undertaken for these two Empetrum species on the eastern Avalon Peninsula. Although E. nigrum has been studied extensively, little is known ecologically of E. eamesii. I investigated phenology, shoot growth, germination success and microhabitat of both Empetrum species. Attempts were made to relate these variables to the distribution patterns of E. nigrum and E. eamesii on the Avalon Peninsula. -- Phenological development of the two species coincided. The blooming period occurred from mid- to late April and was followed by fruit formation from the beginning to late May. Fruit maturation was initiated at the beginning of July and all development ceased in mid-late August. -- Shoot growth was significantly greater for E. nigrum in both the field and greenhouse monitoring programs. The mean annual growth of E. nigrum in the field was 15.0 mm and in the greenhouse 77.5 mm. E. eamesii grew less than E. nigrum, and measurements were carried out only in the field for E. eamesii since propagation of this species in the greenhouse was unsuccessful. The mean annual shoot growth of E. eamesii was 8.5 mm. The differences were related to microhabitat conditions such as windspeed and soil nutrient availability at the sites. -- Germination experiments conducted in the laboratory showed that E. eamesii had an overall significantly greater germination success than E. nigrum at 10° and 5°C. This may be related to the variation in sites and microhabitats. Both E. nigrum and E. eamesii had optimal germination at 25°C. -- A Discriminant Function Analysis was performed on the microhabitat variables. The microhabitat differences were found to be generated from an exposure gradient, that is windspeed and elevation contributed the most to interspecific variation. The remaining microhabitat variables, air and soil temperature, available soil nutrients, soil pH, and organic matter concentration of the soil contributed little to the interspecific difference between E. nigrum and E. eamesii. -- A stepwise Multiple Regression was performed to explain the distributions of E. nigrum and E. eamesii based on their abundance and microhabitat variables. A regression for E. eamesii showed windspeed to be negatively related to abundance. These results indicate that windspeed is a major factor influencing to Empetrum distribution on the Avalon Peninsula. Empetrum nigrum grows in relatively more protected areas, whereas E. eamesii occurs in more exposed and windswept sites.

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