ABSTRACT: Riparian zone setting influences on the carbon isotopic compositions of Tree-ring sequences in the Slave River Delta, Northwest Territories, Canada.

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Abstract

Variations in the chemical composition of tree-rings are often primarilyfashioned by climatic influences that can be reconstructed through a technique known as isotope dendroclimatology. An increased awareness of the physiological complexities associated with carbon, oxygen and hydrogen uptake from the environment, and its subsequent transport and incorporation into tree-ring wood, has allowed for reliable qualitative and quantitative reconstructions of environmental variables that regulate a trees’ internal moisture balance. In this study, tree-ring sections and increment borer cores sampled from six white spruce (Picea glauca) trees at three sites within the Slave River Delta (SRD), Northwest Territories, Canada, were divided into annual tree-ring segments, processed for alpha-cellulose and analyzed for their carbon isotope compositions. The three cellulose carbon isotope time-series, collectively covering the time period from AD 1689 – 2003, were statistically correlated with average Historical Monthly Climate Grid (HMCG) temperature and precipitation for the period AD 1901–2000. The results presented here suggest the trees from all three sites show a distinct trend towards more enriched cellulose carbon isotope values with time, implying more stressful environmental conditions possibly related to the overall 20th Century drying of the Slave River Delta. Additionally apparent anthropogenic river influences such as heavy logging periods and upstream dam implementation are also present in the carbon isotope time-series from the Slave River Delta. The main study focus relates to the differences in riparian nature of the three sites. The cellulose carbon isotope values of the trees from the elevated or more remote river sites suggest a relationship with moisture-deficit-stress (MDS) emanating from hydroclimate effects during both the non-growing and growing seasons. The cellulose carbon isotope values from a lower elevation river adjacent site, however, suggest that these same effects can manifest as moisture-excess-stress (MES) on the trees. The relationships between these two types of moisture stress and the cellulose carbon isotope values of the trees from the sites with obvious riparian differences are discussed in detail.

Bibliography of Canadian Geomorphology