By Gene E. Likens (auth.)
The aim of this 3rd variation is to replace long term facts provided in previous variants and to generate new syntheses and conclusions concerning the biogeochemistry of the Hubbard Brook Valley in accordance with those longer-term information. there were many adjustments, revelations, and interesting new insights generated from the longer information documents. for instance, the influence of acid rain peaked throughout the interval of the HBES and is now declining. The longer-term info additionally posed demanding situations in that very marked alterations in fluxes happened in a few elements, akin to hydrogen ion and sulfate deposition, calcium and nitrate export in circulate water and biomass accumulation, throughout the nearly 50 years of checklist. hence, offering “mean” or “average” stipulations for plenty of elements for this sort of lengthy interval, whilst swap used to be so well known, don't make experience. often times, pentads or many years of time are in comparison to express those alterations in a extra smoothed and rational method for this lengthy interval. from time to time, a unmarried interval, usually during times of swift switch, comparable to acidification, is used to demonstrate the most point(s). And, for a few components a distinct mass stability technique, permitting the calculation of the web surroundings Flux (NEF), is proven on an annual foundation during the study.
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Additional info for Biogeochemistry of a Forested Ecosystem
The concentrations of dissolved chemicals characterizing a period of time are reported as volume-weighted averages. These averages are computed by summing the amount of chemical from individual samples of precipitation or stream water during the period and then dividing this value by the total amount of water during the period. Nutrient flux (see Chap. 4) across ecosystem boundaries is determined by two methods. , g/ha-month). Streamwater outputs are calculated by multiplying the measured concentrations of dissolved chemicals in streamwater samples taken at the beginning and at the end of the interval by the streamflow on those dates.
The ideal water-year begins and ends for a period that shows little interannual change in watershed water storage, often a point in the year of lowest water storage. , soil water and snow). In watersheds of the HBEF, streamflow is largely dependent on (1) precipitation, (2) the capacity for water storage in the soil and thereby the amount of water stored in the soil at any time, and (3) the amount of water stored in the snowpack. 99 (see Federer et al. 1990). 95) and a regression slope closest to one.
1970; Likens et al. 1970; Bormann and Likens 1979). A. Federer, personal communication), but transpiration is difficult to quantify at large scales like a watershed. There is a major need for additional quantitative measurements to partition evapotranspiration into evaporation from the forest canopy and the ground and transpiration. 001) even though there has been a statistically significant increase in both Streamflow and Evapotranspiration 27 Annual Streamflow or ET (mm/yr) 1600 1400 1200 1000 800 1964 600 400 200 600 800 1000 1200 1400 1600 1800 2000 Annual Precipitation (mm/yr) Fig.