Historical Roots of Forest Hydrology and Biogeochemistry

Leroy Jones reading rainfall recorded in a standard rain gageat the weather station at the Coweeta Hydrologic LaboratoryAdministration Headquarters. Photo taken by Leland J. Prater(September 1952).

H-flumes and Coshocton wheels like this one at the Oxford,Mississippi, Hydrologic Laboratory were used in the mid-Southstudies to measure flow and sediment runoff from catchments withdifferent harvesting and site preparation practices. The Coshoctonwheel rotates to expose a slot that collects a fixed proportion of theflow coming off the watershed. Dr. Stan Ursic of the HydrologicLaboratory demonstrates how the wheel works.

Sources of photos and notes –

McGuire, K., and G.E. Likens 2011. Historical roots of forest hydrology and biogeochemistry. In D.F. Levia et al. (eds.), Forest Hydrology and Biogeochemistry: Synthesis of Past Research and Future Directions, Ecological Studies 216, DOI 10.1007/978-94-007-1363-5_1, # Springer Science Business Media B.V. 2011

Ice, G.G. and J.D. Stednick. 2004. Forest watershed research in the United States. Forest History Today.http://www.foresthistory.org/publications/FHT/FHTSpringFall2004/2004Watershed.pdf

• 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 Gaging station at Wagon Wheel Gap,

Colorado. This was theprototype for later small forest watershed studies in the United States,with a control watershed and calibration period prior to treatment.USDA Weather Bureau photo (1928).

A tramway carried employees and visitors to the remote Fremont Experimental Station!

http://www.fs.fed.us/outernet/rm/main/history/rmrs_a_look_back.pdf

• 1909 – 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) – temporarily

• 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.

Coweeta Hydrologic Laboratory http://coweeta.uga.edu/• Located in the Blue Ridge Physiographic province of North Carolina• 2185 hectares• Streamflow monitoring in 1934• Stream chemistry monitoring – 1968

Hubbard Brook Ecosystem Forest (HBEF)http://www.hubbardbrook.org/• 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

• 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’sobservations and results

• Infiltration was seldom limiting in forest landscapes

Forest Management to Ecosystem ScienceThen 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.

Really helped the development of ecosystem models and quantification of the fluxes.

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!

http://www.hubbardbrook.org/overview/HBEF_establishment.htm

• 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!

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 3rd edition in 2013) –http://www.springer.com/life+sciences/ecology/book/978-1-4614-7809-6

Role of Vegetation and its growth status in nutrient cycling

• Conducted a number of manipulation experiments –where forest vegetation was removed and the impacts on water and nutrient losses from watershed was studied

Role of Vegetation and its growth status in nutrient cycling

• 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!

A series of watershed experiments are shown in this photo of Hubbard Brook, New Hampshire, taken the winter of 1972–1973.

In the foreground is a block-clearcutting (performed in 1970). In the middle of the photo is a progressive strip cutting (performed from 1970–1974). To the far right is a watershed that was clear-cut with trees left on site (1965–1966) and experimentally treated with herbicides (applications for three years).

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

Acid Rain and insights from HBEF

• 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

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.