Modeling The Production And Transport Of Dissolved Organic Carbon From Heterogeneous Landscape

Variation of dissolved of organic carbon concentration in stream water is a consequence of process changes in the surrounding terrestrial environment. This study will focus on 1) Identify significant environmental factors controlling the spatial and temporal variation of DOC in terrestrial ecosystems of a watershed southeast of Boston, Massachusetts; 2) Model the DOC leaching from different land cover and examine the relationship between leaching flux and in-stream DOC. Our hypothesis is variations of in stream DOC is closely related to watershed properties and environmental factors at annual, seasonal, and daily scales, especially land cover type, watershed size and hydrology. To explore the relationship of hydrology and DOC variation at ungauged sub-basin, we examined the effectiveness of using simulated stream flow from Soil Water Assessment Tool (SWAT) to study terrestrial DOC dynamics. Our results demonstrated that streamflow, drainage area, and percent of wetland and forest were particularly strong predictors in watersheds with a large proportion of developed area. The resulting linear model is able to explain about 70.2% (R2=0.702) and 65.1% (R2=0.651) of the variance of in-stream DOC concentrations at seasonal and annual scales respectively. Results also suggest that more frequent DOC sampling is necessary to establish the quantitative relationship between simulated stream flows from the SWAT and in-stream DOC concentrations at daily scale. The physically based ecosystem model developed in this study shows that DOC leaching from various land cover are highly correlated (up to 80%) with in-stream DOC by using ecological process with incorporated different hydrological pathways. It shows that leaching of DOC from soil is a significant contributor to the in-stream DOC. The production of DOC is largely controlled by the vegetation type and soil texture. Considering the hydrologic control on DOC transport with different pathways of water at finer spatial and temporal scale highlights the need to identify the quantitative relationships between water and carbon flux.

Dissolved organic carbon (DOC) leached from the O horizon of forest soils is a major source of soil organic carbon in the mineral soil, where a major proportion of the organic carbon in forest ecosystems is located. The relative contribution of recent litter and humified organic matter to the leaching of DOC from the O horizon is still being debated. In the present work, I studied the sources of DOC leached from the O horizon by manipulating the amounts of litter and humus and measuring DOC concentrations and fluxes, isotopic composition (13C and 14C) and chemical characteristics (measured by NMR, UV absorbance and fractionation into hydrophilic and hydrophobic compounds). A computer model (DyDOC) was used to simulate the DOC leaching processes. Furthermore, DOC was measured at different soil moisture conditions at three sites along a climate gradient in Sweden. In addition, 14C measurements of DOC were made at two of these sites to reveal the fate of the DOC leached from the O horizon. I concluded that about half or more of the DOC leached from recent litter is lost during passage through the O horizon. Despite this, both recent litter in the Oi horizon and more humified organic matter in the Oe and Oa horizons contribute significantly to the DOC leaving the O horizon, but with the major proportion coming from the Oe and Oa horizons. To successfully model DOC leaching, the DyDOC model had to be modified to allow DOC to also be leached from recent litter. Measurements along the climatic gradient showed that the concentration and fluxes were highest in the south and lowest in the north. I suggest that these differences can be related to differences in net primary production. Both differences in mean annual temperature and the gradient in nitrogen status from south to north contribute to this effect of net primary production. Soil moisture had no effect on DOC leaching out of the O horizon. The DOC concentration in the B horizon, which is a sink for DOC, is largely go

This groundbreaking work connects the knowledge of system function developed in ecosystem ecology with landscape ecology's knowledge of spatial structure. The book elucidates the challenges faced by ecosystem scientists working in spatially heterogeneous systems, relevant conceptual approaches used in other disciplines and in different ecosystem types, and the importance of spatial heterogeneity in conservation resource management.

Marine dissolved organic matter (DOM) is a complex mixture of molecules found throughout the world's oceans. It plays a key role in the export, distribution, and sequestration of carbon in the oceanic water column, posited to be a source of atmospheric climate regulation. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, focuses on the chemical constituents of DOM and its biogeochemical, biological, and ecological significance in the global ocean, and provides a single, unique source for the references, information, and informed judgments of the community of marine biogeochemists. Presented by some of the world's leading scientists, this revised edition reports on the major advances in this area and includes new chapters covering the role of DOM in ancient ocean carbon cycles, the long term stability of marine DOM, the biophysical dynamics of DOM, fluvial DOM qualities and fate, and the Mediterranean Sea. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, is an extremely useful resource that helps people interested in the largest pool of active carbon on the planet (DOC) get a firm grounding on the general paradigms and many of the relevant references on this topic. Features up-to-date knowledge of DOM, including five new chapters The only published work to synthesize recent research on dissolved organic carbon in the Mediterranean Sea Includes chapters that address inputs from freshwater terrestrial DOM

In order to build consensus on methods to measure and model soil carbon stocks and stock changes, the Steering Committee of the Livestock Environmental Assessment and Performance (LEAP) Partnership mandated a task force to develop this scoping analysis and pave the way towards the formation of the LEAP Tecnical Advisory Group on soil carbon stock changes. Soil carbon sequestration and storage in grasslands offers a significant potential to compensate for GHG emissions from livestock, but the lack of consensus on the appropriate methodologies to account for soil carbon stock changes hinders robust and standardized assessments. In this report, we reviewed several published soil organic carbon (SOC) models, and evaluated their aptitude to combine them with life cycle assessments (LCAs). Among contentious issues, the most relevant are: a) the lack of universal models, b) the uneven data availability, comparability and quality between countries and regions, and c) the difficulty to match measurable SOC fractions with those determined by the models. Taking this into account, a tiered approach is proposed, according to the availability of original data to run the models. The use of IPCC carbon (C) accounting system appears to be the simplest approach suitable to countries with scarcity of original C data. Conversely, more complex models such as Century (Parton 1987, 1988) or Roth C (Smith 1998) are likely to perform better and give less uncertainty when original input data are easily available.

Overviews of the source, supply and variability of DOM, surveys of the processes that mediate inputs to microbial food webs, and syntheses consolidating research findings provide a comprehensive review of what is known of DOM in freshwater. This book will be important to anyone interested in understanding the fundamental factors associated with DOM that control aquatic ecosystems."--BOOK JACKET.