Date of Award

8-2011

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Ivan J. Fernandez

Second Committee Member

Michael E. Day

Third Committee Member

G. Bruce Wiersma

Abstract

Annual developmental events in biological systems are dependent, in part, on environmental conditions. They are valuable bio-indicators of shifting climate, making the science of phenology an essential component of climate change research. Many studies have been done on the effects of temperature and photoperiod on phenophases, but fewer have explored the consequences of nutrient availability in terrestrial ecosystems. The Bear Brook Watershed in Maine (BBWM) provides an opportunity to evaluate morphological and chemical phenology as influenced by decadal-scale experimental ecosystem acidification and nitrogen (N) enrichment. BBWM is a paired watershed study designed to assess responses to a changing chemical and physical climate. The West Bear (WB) watershed has been treated bimonthly with (NH4)2SO4since 1989; the East Bear (EB) watershed serves as a reference. Significant differences have been found between the WB watershed and the EB watershed with respect to biogeochemical cycles affecting essential plant nutrients. Phenophases of Acer rubrum, Acer saccharum, and Picea rubens in both watersheds were observed throughout the 2010 growing season. Phenological development phases included bud burst, flowering (A. rubrum), leaf or needle emergence and unfolding, leaf senescence (Acer spp.), and leaf fall (Acer spp). Clear species-specific phenological patterns were observed, but no treatment effects were evident, possibly as a result of the limited precision of this initial study. Chemical phenology of canopy tree foliage was also examined. Foliage samples were collected on a monthly basis from May through October 2010 and analyzed for total N, carbon (C), phosphorus (P),calcium (Ca), magnesium(Mg), potassium (K), aluminum (Al), boron(B), copper(Cu), iron (Fe), and manganese(Mn) content. Nitrogen was the only element that was significantly higher in the WB watershed for all species, although not all months showed significant differences. West Bear A. rubrum foliar N concentrations were only higher in May, while WB A. saccharum and P. rubens foliar N concentrations were consistently higher than EB. Foliar C, P, Mn, and Fe concentrations in A. rubrum trees and foliar Fe concentration in A. saccharum trees were higher in the WB watershed. Foliar P concentrations were higher in one year old P. rubens foliage of the WB watershed compared to EB. Foliar Ca and Mg concentrations were lower in A. rubrum of the WB watershed, but did not differ between treatments in A. saccharum or P. rubens. Foliar Cu and Zn concentrations were lower only in A. saccharum trees of the WB watershed. Foliar K and Al concentrations did not differ between treatments in any species. Foliar N and P concentrations decreased in all species throughout the growing season, while foliar Ca, K, and Al concentrations increased or were constant. This study found clear species-specific patterns of morphological and chemical phenology with time, but did not show evidence for visible alterations in seasonal development as a result of ecosystem acidification and N enrichment. Chemical phenology, as applied here, showed some responses consistent with ecosystem change that should be further explored for application to coupled chemical-biological indicators of a changing chemical and physical climate.

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