Historical Roots of Forest Hydrology and Biogeochemistry

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1 Historical Roots of Forest Hydrology and Biogeochemistry Kevin McGuire and Gene E. Likens 2011 Provides an historical context on how the science of forest hydrology and biogeochemistry (or hydrochemistry) developed! Late 1800s and early 1900s interest was primarily focused on how forest removal affects floods and erosion; considerable uncertainty about the role of forests in water management The importance of forests for flood control and water storage was accepted by foresters but not by engineers Initial watershed study sites were established to resolve this controversy first experimental station at Wagon Wheel Gap in CO in the early 1900s Wagon Wheel Gap Station 1

2 A tramway carried employees and visitors to the remote Fremont Experimental Station! establishment of first paired watershed study site at Wagon Wheel Gap to study the effects of forest removal on runoff yields Forest removal did increase runoff yield (decreased evapotranspiration) As a result of the 1936 Omnibus Flood Control Act, USDA Forest Service created more experimental stations across the country which included Coweeta Hydrologic Laboratory, Hubbard Brook, HJ Andrews, etc. 2

3 Coweeta Hydrologic Laboratory Located in the Blue Ridge Physiographic province of North Carolina 2185 hectares Streamflow monitoring in 1934 Stream chemistry monitoring

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5 Hubbard Brook Ecosystem Forest (HBEF) Established in 1955 in the White Mountains of New Hampshire 3307 ha watershed Stream chemistry monitoring started in 1963 First watershed where budgets for element cycling were developed 5

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7 Initial studies were focused on impact of forest and silvicultural management practices on streamflow and sediment yield Later on a wider set of questions were addressed such as changes in forest type, vegetation types, density of forests, et. on water storage and evapotranspiration. These study locations were also very beneficial and instrumental in stimulating new paradigms and concepts in forest hydrology --like the Variable Source Area (VSA) concept Coweeta hydrologic laboratory Hewlett s and Hibbert s observations and results Infiltration was seldom limiting in forest landscapes. 7

8 Forest Management to Ecosystem Science Then came the Ecosystem Concept in Ecology pioneered by Eugene Odum in the late 1950s. Eugene Odum E. P. Odum s (1953) definition of the ecosystem as a... natural unit that includes living and nonliving parts interacting to produce a stable system in which the exchange of materials between the living and nonliving parts follows circular paths.... Led to the characterization of ecosystems has having specific and well defined compartments with fluxes of energy and nutrients among the compartments. Figure 1.2 Really helped the development of ecosystem models and quantification of the fluxes. 8

9 The Small Watershed Approach Defining boundaries and compartments in forest stands was always a problem Bormann and Likens at Hubbard Brook thought that the watershed could serve as a nicely contained unit with topographical and physiological boundaries of ecosystems - to apply the ecosystem concept! Thus, started the use of the small watershed approach to study watershed biogeochemistry! 9

10 Hydrologically gauged watersheds at HBEF allowed for study of inputs and outputs of water as well as nutrients and the role of atmospheric, biotic, geologic and hydrologic components in the fluxes and budgets of nutrients. Hubbard Brook Ecosystem Study began in June 1963 when Likens and Bormann received a NSF grant to study the Hydrologic-mineral interaction in a small watershed Observations and results from HBES paved the way for important scientific discoveries on how ecosystems and watershed function and also helped address some key environmental challenges! 10

11 Watershed-ecosystem nutrient budgets First site to develop watershed scale ecosystem budgets for nutrients Ca, Mg, Na, K etc. Helped understand the role of mineral weathering and biogeochemical reactions in the transport and retention of these solutes Lot of the details in book by Gene Likens Biogeochemistry of a Forested Ecosystem (now 3 rd edition in 2013) 11

12 Role of Vegetation and its growth status in nutrient cycling Conducted a number of maniputation experiments where forest vegetation was removed and the impacts on water and nutrient losses from watershed was studied Forest removal lead to increase in streamflow runoff, and greater exports of NO3 and other associated nutrients such as Ca, Mg, Na, and K from the watersheds NO3 was lost because of loss of nutrient uptake by vegetation Results showed that in absence of vegetation, watershed ecosystems had limited capacity to retain nutrients! Had important implications for forest management practices such as clear-cutting! 12

13 Acid Rain and insights from HBEF The detailed monitoring of water chemistry sampling, development of watershed budgets, and computations of nutrient fluxes at HBEF also allowed it to address one of the greatest challenges of the 60s and 70s Acid rain and its impacts on watershed ecosystems The long term water and chemical records being collected at HBEF were especially valuable in deciphering trends from Acid Rain First published account about the effects of Acid Rain in North America came from HBEF! Losses and depletion of cations from the watersheds as a result of acid inputs! The long dataset also revealed the decrease in the loss of cations in the 90s when controls on sulfate emissions were implemented by the industry 13

14 Development of watershed nutrient models and their use as predictive tools The large collection of data, synthesis of this information into budgets and fluxes, and the use of the ecosystem concept - all facilitated the development of models Models were used to test hypotheses and understand watershed functions Models have also been used as a predictive tool future long-term changes in ecosystem processes Examples of some models BROOK JABOWA PnET PnET-BGC These models have led to the development of many other ecosystem and catchment models of hydrology and biogeochemistry. 14