By Gene E. Likens (auth.)
The objective of this 3rd variation is to replace long term facts provided in previous versions and to generate new syntheses and conclusions in regards to the biogeochemistry of the Hubbard Brook Valley according to those longer-term facts. there were many adjustments, revelations, and interesting new insights generated from the longer info documents. for instance, the effect of acid rain peaked in the course of the interval of the HBES and is now declining. The longer-term facts additionally posed demanding situations in that very marked alterations in fluxes happened in a few parts, reminiscent of hydrogen ion and sulfate deposition, calcium and nitrate export in movement water and biomass accumulation, in the course of the nearly 50 years of checklist. therefore, offering “mean” or “average” stipulations for lots of elements for this sort of lengthy interval, while swap was once so admired, don't make experience. on occasion, pentads or many years of time are in comparison to exhibit those alterations in a extra smoothed and rational approach for this lengthy interval. occasionally, a unmarried interval, frequently during times of fast switch, similar to acidification, is used to demonstrate the most point(s). And, for a few components a distinct mass stability method, permitting the calculation of the internet atmosphere Flux (NEF), is proven on an annual foundation through the study.
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As standard practice, we do not include data from bulk precipitation samples that contain fresh leaves, bird feces, bud scales, insects, or any other significant foreign particles. Such contamination can represent a serious problem, because a variety of substances can leach from these materials as the water comes in contact with them in the collector. Our intent is to have enough collectors in position to provide at least one “clean” sample per interval. This procedure normally works very well at our site.
Soils Soils are diverse, but well-drained spodosols (Haplorthods) of sandy loam texture, with a thick organic layer at the surface, are most common. Most liquid precipitation infiltrates into the soil at all times, and there is very little overland flow because the surface soil is very porous, the surface topography is very rough (pit and mound, mostly from windthrown trees), and normally there is little soil frost (Pierce 1967). Soils in the Hubbard Brook Valley were formed in glacial till of variable depth, underlain by metamorphic rock of igneous and sedimentary origin (schists and quartz monzonite) (Johnson et al.
From June to October, the streams are heavily shaded by the forest vegetation. As a result, daily water temperatures do not vary more than a degree or two Celsius during that time of year. Maximum streamwater temperatures (~21 °C) occur just before leaf out of the forest canopy. The annual temperature range in these streams is about 0 °C to about 18 °C, with a mean of about 7 °C. The mean annual temperatures in two of the south-facing streams (W3 and W6) declined ~2 °C from 1966 to 1983 and then increased by ~1 °C and became more variable thereafter (Likens 2011).