Harvard Forest On-Going Research Projects

Harvard Forest Research

Identifying the impacts of hydrological events on DOM dynamics

Principal Investigator: Peter Raymond
Yale University: Sep 01 2009 - Sep 01 2011:

Abstract:
Across global ecosystems dissolved organic matter (DOM) represents an essential flux of material from terrestrial to aquatic environments. In freshwater ecosystems DOM inputs generally represent the largest and most bioavailable flux of carbon from the terrestrial environment. Although the sensitivity of DOM dynamics to hydrologic events is well recognized, the mechanisms that govern this phenomenon remain poorly understood. An increase in the frequency of extreme hydrologic events is projected to accompany future climate change. Therefore, understanding the physicochemical mechanisms controlling DOM transport and processing is of fundamental importance if we hope to predict the impact of future climate changes on aquatic ecosystem function and global carbon dynamics.
This research will focus on determining the role played by hydrological events in mediating DOM dynamics and related in-stream processes. In particular, we will address the following research question: What mechanisms within the watershed control allocthonous DOM export and structure during hydrological events?
The optical properties of stream water DOM and soil water DOM will be measured intensively over a 12-month period using spectrophotometric methods (UV-vis and Fluorescence). At the stream outlet and in set of 3 well sites, a set of optical probes will be employed to collect measurements every 15 minutes. Measurements from these probes will be used to infer DOC concentrations and to identify changes in DOM structure. To calibrate these fine-scale optical measurements and to provide a more detailed characterization of DOM composition, a suite of additional measurements will be taken at less frequent intervals. These will include more extensive fluorescence characterization for PARAFAC analysis, measurement of dissolved elemental composition (C, N, P), and isotopic composition 13C and 14C. These data will be used to create a new mathematical model that accounts for the routing of rainfall and snowmelt, DOM mobilization, DOM transport to the stream via surface and subsurface pathways, and stream-water DOM export.
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	Harvard Forest Research Identifying the impacts of hydrological events on DOM dynamics Principal Investigator: Peter Raymond Yale University: Sep 01 2009 - Sep 01 2011: Abstract: Across global ecosystems dissolved organic matter (DOM) represents an essential flux of material from terrestrial to aquatic environments. In freshwater ecosystems DOM inputs generally represent the largest and most bioavailable flux of carbon from the terrestrial environment. Although the sensitivity of DOM dynamics to hydrologic events is well recognized, the mechanisms that govern this phenomenon remain poorly understood. An increase in the frequency of extreme hydrologic events is projected to accompany future climate change. Therefore, understanding the physicochemical mechanisms controlling DOM transport and processing is of fundamental importance if we hope to predict the impact of future climate changes on aquatic ecosystem function and global carbon dynamics. This research will focus on determining the role played by hydrological events in mediating DOM dynamics and related in-stream processes. In particular, we will address the following research question: What mechanisms within the watershed control allocthonous DOM export and structure during hydrological events? The optical properties of stream water DOM and soil water DOM will be measured intensively over a 12-month period using spectrophotometric methods (UV-vis and Fluorescence). At the stream outlet and in set of 3 well sites, a set of optical probes will be employed to collect measurements every 15 minutes. Measurements from these probes will be used to infer DOC concentrations and to identify changes in DOM structure. To calibrate these fine-scale optical measurements and to provide a more detailed characterization of DOM composition, a suite of additional measurements will be taken at less frequent intervals. These will include more extensive fluorescence characterization for PARAFAC analysis, measurement of dissolved elemental composition (C, N, P), and isotopic composition 13C and 14C. These data will be used to create a new mathematical model that accounts for the routing of rainfall and snowmelt, DOM mobilization, DOM transport to the stream via surface and subsurface pathways, and stream-water DOM export. :
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