Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 145-146). / vi, 146 leaves, bound ill., maps 29 cm

Typescript (photocopy) / xii, 149 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Soil Science, University of Adelaide, 1982

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Inputs of DOC in precipitation were low and increased with the passage of rainfall through different canopies. Throughfall, stemflow, leachates from A horizons and litterfall were identified as sources of DOC, while B and C horizons in upland areas provide a sink. Throughfall and stemflow displayed high temporal variability in DOC concentrations, while soil leachates and peat waters exhibited strong seasonal patterns. DOC concentrations in throughfall, stemflow and A horizons were highest in the predominantly coniferous site. In the fall, DOC concentrations from A horizons in the deciduous site were significantly higher than those from the coniferous site. / Factors influencing DOC in peat waters are: (1) peat thermal regime, (2) water chemistry, and (3) water table position. Large storms ($>$30 mm precipitation) appear to be the primary factor influencing exports of DOC in streamflow, particularly following dry antecedant soil moisture conditions. Slow rates of water movement through compact deep peats ($>$60 cm depth) and adsorption of DOC in B and C horizons of this catchment obstruct exports of DOC, which over the 5.5 month study period, were minimal in comparison to inputs.

An incubation technique was used to examine carbon mineralization and inorganic nitrogen accumulation in samples of Douglas-fir and alder forest floors developed over soils derived from granitic, ultrabasic and limestone parent materials in western British Columbia and Washington. Samples included L, F, and H or Hi horizons of Douglas-fir mor, raw moder, mull-like moder and mull forest floors and alder typical moder forest floors. Carbon dioxide production by the forest floor materials provided an estimate of gross carbon mineralization and an approximate indication of gross nitrogen mineralization. Comparison of inorganic nitrogen accumulated and gross carbon mineralized indicated that a large fraction of the mineralized inorganic nitrogen is immobilized by the microbial population and (or) lost to denitrification. The Hi horizons (organic horizons containing considerable incorporated mineral matter) accumulated more inorganic nitrogen than did the L and F horizons. Alder forest floors accumulated more inorganic nitrogen than did Douglas-fir forest floor materials. Alder L horizons tended to accumulate ammonium nitrogen while the F and Hi horizons accumulated nitrate nitrogen. Douglas-fir mor forest floors were distinguished from their mull and moder counterparts by slower decomposition and less inorganic nitrogen accumulation, and by largely accumulating ammonium nitrogen in all horizons. Irregular nitrogen accumulation curves, for some samples of Douglas-fir L and F horizons were probably due to denitrification losses. Incubation conditions favoring nitrification, with no plant sinks to remove accumulated inorganic nitrogen, may have favored denitrification losses. / Land and Food Systems, Faculty of / Graduate

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Globally, the forestry sector is the second largest contributor of greenhouse gases, and sustainable forest management is a major target of international environmental policy. However, there is the assumption underlying many policy recommendations that an increase in above-ground carbon stocks correspond to long term increases in ecosystem carbon stocks, the majority of which is stored in soils. We analyzed soil carbon and nitrogen dynamics in forest soils that had undergone twenty years of organic inputs manipulations as part of the Detritus Input and Removal Treatment (DIRT) network. There was no statistically significant effect of the rate of litter or root inputs on the carbon or nitrogen in bulk soil, on respiration rates of soil in laboratory incubations, on the non-hydrolyzed fraction of soil organic matter, or on any organic matter associated with any density. However, there is evidence for positive priming due to increased litter inputs; doubling the rate of litter inputs decreased C and N contents of bulk soil and decreased respiration rates of soil. Furthermore, there is evidence that roots influence soil organic matter dynamics more strongly than above-ground inputs. Both of these results trends match data from other DIRT sites, and are supported by the literature. / Graduation date: 2012