Keri Van Camp

Date of Award

12-2005

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Botany and Plant Pathology

Advisor

Christa R. Schwintzer

Second Committee Member

Ivan J. Fernandez

Third Committee Member

John D. Tjepkema

Abstract

The effects of environmental variables on establishment of Myrica gale were studied in seedlings grown on fen peat, poor fen peat, and bog peat collected from Caribou Bog in Maine and on mineral soils collected from the shore of nearby Mud Pond. For successful establishment, seedlings need to form nitrogen-fixing nodules early in development and become large enough to have sufficient carbon and nutrient reserves to survive dormancy and resume growth in the spring. The effect of availability of nutrients, infective Frankia, and water on plant growth and formation of nitrogen fixing nodules were examined in a growth chamber. The effect of sun and shade on plant growth was examined outdoors on fen peat. Plants grown with distilled water achieved substantial shoot mass in fen peat (0.048 f. 0.005 g; mean + SE) and mineral soil (0.028 + 0.004 g) indicating that nutrient availability in these soils are sufficient for establishment. However, plants grown in the poor fen peat with distilled water had much smaller shoot masses (0.010+ 0.001 g) indicating that nutrients in the poor fen peat are insufficient for establishment. Additional nutrients enhanced growth on all soils indicating that the nutrient levels were not optimal for growth. Infective Frankia was present in the fen peat and mineral soil because plants nodulated without additional inoculum. However, infective Frankia was not consistently present in the poor fen peat because plants formed nodules on uninoculated peat collected in the spring and did not fom nodules on uninoculated peat collected in the fall. Plants grown in the bog peat did not nodulate unless inoculum was added indicating that infective Frankia was not present. Plants grown in the sun were more than twice as large and had approximately 40% greater survivorship than plants grown in the shade. Establishment is probable in the sun if other factors are favorable. However, plants in the sun had a greater number of Carex spp. seedlings emerge from the peat than plants in the shade indicating that competition is greater in the sun than in the shade. The growth rate of Myrica gale decreased as water availability declined. Plants grew over 4 times larger with high water availability than with low water availability. Plants grown with high water availability had twice the survivorship and developed side shoots more frequently than plants grown with low moisture or plants that were exposed to incipient wilting. Heavy wilting resulted in approximately 90% of the leaves becoming damaged or dying in all treatments. The loss of such a large amount of leaf area makes establishment unlikely if heavy wilting occurs. Establishment is most probable when water availability is consistently high. In Maine, seedlings and isolated young plants have only been observed on stumps and logs in shallow water. Flooding, wave action, and ice cutting make germination and establishment unlikely on lakeshores and riverbanks. Stumps and logs probably play an important role in seedling establishment because they provide a stable substrate and some , protection from the harsh conditions of the shore.

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