Biogeochemistry of a Forested Ecosystem

Dr. Likens' research focuses on the ecology and biogeochemistry of forest and aquatic ecosystems, primarily through long-term studies at the Hubbard Brook Experimental Forest, in the White Mountains of New Hampshire. He was the co-founder of the Hubbard Brook Ecosystem Study in 1963, which has shed light on critical links between ecosystem function and land-use practices. He and his colleagues were the first scientists to discover acid rain in North America and to document the link between the combustion of fossil fuels and an increase in the acidity of precipitation. His findings have influenced politicians and policy makers, guided and motivated scientific studies, and increased public awareness of human-accelerated environmental change.

The goal of this Third Edition is to update long-term data presented in earlier editions and to generate new syntheses and conclusions about the biogeochemistry of the Hubbard Brook Valley based on these longer-term data. There have been many changes, revelations, and exciting new insights generated from the longer data records. For example, the impact of acid rain peaked during the period of the HBES and is now declining. The longer-term data also posed challenges in that very marked changes in fluxes occurred in some components, such as hydrogen ion and sulfate deposition, calcium and nitrate export in stream water and biomass accumulation, during the almost 50 years of record. Thus, presenting "mean" or "average" conditions for many components for such a long period, when change was so prominent, do not make sense. In some cases, pentads or decades of time are compared to show these changes in a more smoothed and rational way for this long period. In some cases, a single period, often during periods of rapid change, such as acidification, is used to illustrate the main point(s). And, for some elements a unique mass balance approach, allowing the calculation of the Net Ecosystem Flux (NEF), is shown on an annual basis throughout the study.

This book describes the integration of several different approaches to examine questions regarding the function of interesting plant metabolites. This new edition generates new syntheses and conclusions about the biogeochemistry of the Hubbard Brook Valley.

Describes the integration of several different approaches to ask and then answer questions regarding the function of interesting plant metabolites

1 Ecosystem Analysis Small Watershed Approach The Hubbard Brook Ecosystem Location Climate Area, Topography, and Aspect Geology Soils Vegetation and Fauna Drainage Streams Concluding Thoughts 2 Hydrology The Water-Year Precipitation Streamflow and Evapotranspiration Deep Seepage Representativeness of the Hydrology of the Hubbard Brook Experimental Forest for Northern New England 3 Chemistry Precipitation Chemistry Annual Volume-Weighted Concentrations Origin of Ions in Bulk Precipitation Dry Deposition Elevational Effects Acid Precipitation Acid rain and base cation depletion Some charge equivalence changes and biotic responses: Headwater results scaled to Hubbard Brook and Beyond: Snow and Snowpack Chemistry Dilution and Effect of Acid Rain on Baselines Impact of acid rain on accumulation of forest biomass How has the forest ecosystem in W6, the reference watershed, responded to acid rain? Trace Metals Throughfall and Stemflow Streamwater Chemistry Concentrations of Dissolved Substances Valleywide Streamwater Chemistry - A Synoptic View Seasonal Variations in Bulk Precipitation and Streamwater Concentrations Long-Term Trends in Bulk Precipitation and Streamwater Chemistry 4 Input-Output Budgets Mass Meteorologic Input of Dissolved Substances Annual Variation in Net Hydrological Budgets Some Examples of Important Components of Input-Output Budgets Nitrogen Chlorine Sulfur Dissolved Silica Input-Output Budgets: Summary Monthly Variations Output Consistently Greater Than Input Input Consistently Greater Than Output Crossover Patterns Relationship of Annual Mass Output of Dissolved Substances to Annual Streamflow Annual Variation in Mass Output of Dissolved Substances Particulate Matter Measurement of mass output Annual loss Seasonal variation in erodibility Particulate Matter Versus Dissolved Substance Export The Role of Debris Avalanches in Landscape Denudation Long-Term Changes in Input/Output Budgets 5 Weathering Source of Hydrogen Ion in the Weathering Reaction Carbon Nitrogen Sulfur Estimates of Ecosystem Weathering Flux Net Soil Release 6 Nutrient Cycles and Mass Balances The Calcium Cycle The Potassium Cycle The Sulfur Cycle Nutrient Cycle Relationships at the HBEF Annual Watershed-Ecosystem Mass Balances ("Budgets") Calcium Sodium Potassium Sulfur Nitrogen Nitrogen retention in forested watershed-ecosystems Chlorine 7 The Northern Hardwood Ecosystem in the Hubbard Brook Valley in Relation to Other Forest Ecosystems 8 Summary Discussion and Conclusions Epilog Odyssey