Linking water age and solute dynamics in streamflow at the Hubbard Brook Experimental Forest, NH, USA

We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to conservative and weathering-derived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to compute hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). The innovative contribution of this paper is the simulation of dissolved silicon and sodium concentration in streamflow, achieved by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key role of water stored within the subsoil glacial material in both the short-term and long-term solute circulation. The travel time analysis provided an estimate of streamflow age distributions and their evolution in time related to catchment wetness conditions. The use of age information to reproduce a 14 year data set of silicon and sodium stream concentration shows that, at catchment scales, the dynamics of such geogenic solutes are mostly controlled by hydrologic drivers, which determine the contact times between the water and mineral interfaces. Justifications and limitations toward a general theory of reactive solute circulation at catchment scales are discussed

Trends in stream nitrogen concentrations for forested reference catchments across the USA

To examine whether stream nitrogen concentrations in forested reference catchments have changed over time and if patterns were consistent across the USA, we synthesized up to 44 yr of data collected from 22 catchments at seven USDA Forest Service Experimental Forests. Trends in stream nitrogen presented high spatial variability both among catchments at a site and among sites across the USA. We found both increasing and decreasing trends in monthly flow-weighted stream nitrate and ammonium concentrations. At a subset of the catchments, we found that the length and period of analysis influenced whether trends were positive, negative or non-significant. Trends also differed among neighboring catchments within several Experimental Forests, suggesting the importance of catchment-specific factors in determining nutrient exports. Over the longest time periods, trends were more consistent among catchments within sites, although there are fewer long-term records for analysis. These findings highlight the critical value of long-term, uninterrupted stream chemistry monitoring at a network of sites across the USA to elucidate patterns of change in nutrient concentrations at minimally disturbed forested sites

The essential value of long-term experimental data for hydrology and water management

We would like to thank the European Research Council ERC for funding the VeWa project and most of Tetzlaff's time (project GA 335910 VeWa). No data were used in producing this manuscript.Peer reviewedPublisher PD

From The Cover: Increased salinization of fresh water in the northeastern United States

Chloride concentrations are increasing at a rate that threatens the availability of fresh water in the northeastern United States. Increases in roadways and deicer use are now salinizing fresh waters, degrading habitat for aquatic organisms, and impacting large supplies of drinking water for humans throughout the region. We observed chloride concentrations of up to 25% of the concentration of seawater in streams of Maryland, New York, and New Hampshire during winters, and chloride concentrations remaining up to 100 times greater than unimpacted forest streams during summers. Mean annual chloride concentration increased as a function of impervious surface and exceeded tolerance for freshwater life in suburban and urban watersheds. Our analysis shows that if salinity were to continue to increase at its present rate due to changes in impervious surface coverage and current management practices, many surface waters in the northeastern United States would not be potable for human consumption and would become toxic to freshwater life within the next century

The chemical composition of atmospheric precipitation from selected stations in Michigan

The pH and amount of rainfall from over 60 selected stations throughout northern and lower Michigan was determined from September 1972 to December 1974. Precipitation pH was determined for each station by calibrated electrode meters.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43904/1/11270_2004_Article_BF00182879.pd

Forests as Commons – Changing Traditions and Governance in Europe

Commons are complex institutions and exist across the world in a wide range of situations regarding locally developed governance and management systems of many different natural resources. For many people commons remain associated with Hardin’s theory concerning the “Tragedy of the Commons” (1968), in which he assumed that local users of a natural resource are unable to formulate governance and management structures concerning their own choices that took into account the long-term sustainability of the resource itself. As a result, Hardin articulated that the tragedy was that the resource would inevitably become degraded in such situations and that the solution was private or public ownership. However, across Europe many forests have for a very long period of time successfully been managed as commons, just as they have in many other parts of the world. This chapter has three main aims: It will provide an introduction to the various types of commons before going on to link the issue of commons to the traditional forest landscapes of Europe, and it will look at how the role of forests and forest landscapes has changed and how it may change further in the future

Trends in stream nitrogen concentrations for forested reference catchments across the USA

To examine whether stream nitrogen concentrations in forested reference catchments have changed over time and if patterns were consistent across the USA, we synthesized up to 44 yr of data collected from 22 catchments at seven USDA Forest Service Experimental Forests. Trends in stream nitrogen presented high spatial variability both among catchments at a site and among sites across the USA. We found both increasing and decreasing trends in monthly flow-weighted stream nitrate and ammonium concentrations. At a subset of the catchments, we found that the length and period of analysis influenced whether trends were positive, negative or non-significant. Trends also differed among neighboring catchments within several Experimental Forests, suggesting the importance of catchment-specific factors in determining nutrient exports. Over the longest time periods, trends were more consistent among catchments within sites, although there are fewer long-term records for analysis. These findings highlight the critical value of long-term, uninterrupted stream chemistry monitoring at a network of sites across the USA to elucidate patterns of change in nutrient concentrations at minimally disturbed forested sites.Keywords: forested catchment, nitrate, trends, stream, reference catchments, ammoniumKeywords: forested catchment, nitrate, trends, stream, reference catchments, ammoniu

Long-term Trends from Ecosystem Research at the Hubbard Brook Experimental Forest

The Hubbard Brook Experimental Forest was established by the U.S. Forest Service in 1955 as a major center for hydrologic research in the Northeast. The Hubbard Brook Ecosystem Study originated 8 years later with the idea of using the small watershed approach to study element flux and cycling and the response of forest ecosystems to disturbance. Since that time, the research program at Hubbard Brook has expanded to include various physical, chemical and biological measurements collected by researchers from a number of cooperating institutions. Collaborative, long-term data are the keystone of the Hubbard Brook Ecosystem Study and have provided invaluable insight into how ecosystems respond to disturbances such as air pollution, climate change, forest disturbance, and forest management practices. This report highlights long- term ecological trends at Hubbard Brook, provides explanations for some of the trends, and lists references from the scientific literature for further reading