Abstract. All vegetation on Watershed 2 of the Hubbard Brook Experimental Forest was cut during November and December of 1965, and vegetation regrowth was inhibited for two years by periodic application of herbicides. Annual stream-flow was increased 33 em or 39% the first year and 27 em or 28% the second year above the values expected if the watershed were not deforested.Large increases in streamwater concentration were observed for all major ions, except NH 4 +, S0 4 = and HC0 3 -, approximately five months after the deforestation. Nitrate concentrations were 41-fold higher than the undisturbed condition the first year and 56-fold higher the second. The nitrate concentration in stream water has exceeded, almost continuously, the health levels recommended for drinking water. Sulfate was the only major ion in stream water that decreased in concentration after deforestation. An inverse relationship between sulfate and nitrate concentrations in stream water was observed in both undisturbed and deforested situations. Average streamwater concentrations increased by 417% for Ca++, 408% for Mg++, 1558% forK+ and 177% for Na+ during the two years subsequent to deforestation. Budgetary net losses from Watershed 2 in kg/ha-yr were about 142 for N0 3 -N, 90 for Ca++, 36 forK+, 32 for Si0 2 -Si, 24 for AI+++, 18 for Mg++, 17 for Na+, 4 for C!-, and 0 for SOrS during 1967-68; whereas for an adjacent, undisturbed watershed (W6) net losses were 9.2 for Ca + +, 1.6 for K +, 17 for Si0 2 -Si, 3.1 for AI+++, 2.6 for Mg+ +, 7.0 for Na +, 0.1 for Cl-, and 3.3 for SO~-S. Input of nitrate-nitrogen in precipitation normally exceeds the output in drainage water in the undisturbed ecosystems, and ammonium-nitrogen likewise accumulates in both the undisturbed and deforested ecosystems. Total gross export of dissolved solids, exclusive of organic matter, was about 75 metric tons/km2 in 1966'-67, and 97 metric tons/km2 in 1967-68, or about 6 to 8 times greater than would be expected for an undisturbed watershed.The greatly increased export of dissolved .nutrients from the deforested ecosystem was due to an alteration of the nitrogen cycle within the ecosystem.The drainage streams tributary to Hubbard Brook are normally acid, and as a result of deforestation the hydrogen ion content increased by 5-fold (from pH 5.1 to 4.3).Streamwater temperatures after deforestation were higher than the undisturbed condition during both summer and winter. Also in contrast to the relatively constant temperature in the undisturbed streams, stream water temperature after deforestation fluctuated 3-4 o C during the day in summer.Electrical conductivity increased about 6-fold in the stream water after deforestation and was much more variable.Increased streamwater turbidity as a result of the deforestation was negligible; however the particulate matter output was increased about 4-fold. Whereas the particulate matter is normally 50% inorganic materials, after deforestation preliminary estimates indicate that the proportion of inorganic materials increased to 76...

Kith the exception of an occasional determination, the analytical results for the recoveries using calcium or magnesium appear to be eqiially good, regardless of xhether pure calcium and magnesium mixtures alone or other mixtures were analyzed.Figure G s h o w the titrimetric curves obtained at 660 mp for varying concentrations of calcium between 1.25 and 5.0 mey per liter of spinal fluid. The intersection of the tangent to the steep ascending slope of the titration curve to a line parallel to the abscissa and tangent to the upper portion of the cuive indicates the end point.A >imilar study ip shoxn in Figure 7 , where increasing concentrations of concentration of magnesium in the range of 1.05 to 4 20 meq. per liter of spinal fluid are titrated a t 660 mp. The end point is graphically determined in the same manner a.; io1 calciiim. A method has been devised for the photometric determination of small amounts of chloride in water. The method is based on the displacement of thiocyanate f r o m mercuric thiocy-anate by chloride ion and the subsequent reaction of the liberated thiocyanate with ferric iron to form the colored complex [Fe(SCN)] ++, which is measured either visually or in a spectrophotometer. Concentrations of chloride as low as 0.05 p.p.m. can be determined. HE literature on the determination of chloridesisvoluminous.T \Yhether present as a required constitumt or as an impuiity, the chloride ion is usually determined by either gravimetric or volumetric methods. The oldest and the classical method is the gravimetric, in which the chloride ion is evaluated as silver chloride. ..inother method frequently employed is the volumetiic, several variations of which are available. The Volhard method, oiiginated by Carpentier ( 7 ) , described by T'olhard (38), and later improved by Lundbak (65) and others (26), is more accurate than the Mohr method ( 2 7 ) .A comparatively recent method is the mercurometric method, which was developed in 1933 by Dubskj. and Trtilek (9, 10).Diphenplcarbohydrazide v a s used as an indicator in the titration n-ith mercuric nitrate. Other 13-orkers (1, 5 , 8, 20, 62, 29,32, 54) later adopted this method with some modifications. ill1 these methods, homeever, are not always suitable for the detei mination of micro quantities of chloride.The present investigation was the result of a need for a simple colorimetric method for the determination of less than microgram quantities of chloride in condensate. Luce, Denice, and ilkerlund ( 6 4 ) determined small amounts of chloride turbidimet-1 ically. This method, however, lacked the required precision.Other methods (2, 4, 6, 14, 15, 17, 81, 28, 55, S9) for the determination of small amounts of chloride either required special apparatus or lacked the desired simplicity.The method presented here is a modification of that proposed b! . Vtsumi (36, 37) and followed up by Imasaki (16). This modified procedure has been greatly improved and broadened in ita application. The use of ferric perchlorate instead of ferric ammonium sulfate eliminates a ...

Stream water chemistry varies hyperbolically with stream discharge through four decades of discharge change within the Hubbard Brook Experimental Forest, New Hampshire. This dilution process is most simply explained by the mixing of rain water or surface water with deeper soil water. The resultant mixture of waters subsequently appears as stream water. Sodium and silica concentrations in stream water are markedly diluted during high discharge periods while hydrogen ion, aluminum, and nitrate concentrations are increased. Magnesium, calcium, sulfate, chloride and potassium concentrations are changed very little by stream discharge variations. During the summer, biologic activity measurably reduces the concentration of nitrate and potassium in stream water.

The forest of a small watershed-ecosystem was cut in order to determine the effects of removal of vegetation on nutrient cycles. Relative to undisturbed ecosystems, the cut ecosystem exhibited accelerated loss of nutrients: nitrogen lost during the first year after cutting was equivalent to the amount annually turned over in an undisturbed system, and losses of cations were 3 to 20 times greater than from comparable undisturbed systems. Possible causes of the pattern of nutrient loss from the cut ecosystem are discussed.

Data on the depth distribution of the major atmospheric gases and the abundance of gaseous 12CO2, 13CO2, and 14CO2 in the subsoil unsaturated zone have been obtained from several sites in the western Great Plains of the United States. Sample profiles range from land surface to depths of 50m. Although each site must be considered on an individual basis, several general statements can be made regarding the profiles. 1) Diffusion of these gaseous molecules through the unsaturated zone is an important transport mechanism. 2) As predicted by diffusion theory, depth profiles of the various isotopic species of CO2 differ substantially from one another, depending on individual sources and sinks such as root respiration and oxidation of organic carbon at depth. 3) In general, post-bomb (> 100% modern) 14C activities are not observed in the deep unsaturated zone, in contrast to diffusion model predictions. 4) In spite of generally decreasing 14C activities with depth, absolute partial pressures of 14CO2 in the subsoil unsaturated zone are 1–2 orders of magnitude higher than the partial pressure of 14CO2 in the atmosphere.

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The balances of input in atmospheric precipitation and discharge in streams have been determined for selected mineral constituents in three small tributaries to Hubbard Brook in the White Mountains of New Hampshire. Inputs and discharge of sulfate, am: monium, and nitrate were calculated from hydrologic data, together with chemical analyses of weekly samples of precipitation and streamwater taken over a 2-year period. The calculations show that precipitation provides most of the 30-50 kilograms of sulfate per hectare carried annually by the streams and that inputs exceed outflows of ammonium and of nitrate. Maximum effluent nitrate concentrations of 2 mg/1 (milligrams per liter) are observed in early spring. Measurements of pit indicate that the hydrogen ion is one of the major cations in precipitation over the area. Determinations were made of the discharge of bicarbonate, silica, and aluminum in the streams. Annual stream loads of silica ranged from 20 to 40 kilograms per hectare. Effluent bicarbonate and silica concentrations vary directly with each other and inversely with aluminum. (Key words' Forests; precipitation; quality of water) Hampshire. The objectives include' (1) the minerals; and with determinations of the indetermination of the rates of addition, internal put in precipitation and discharge in streams of calcium, magnesium, sodium, potassium, and circulation, and egress of dissolved mineral chloride [Likens et al., 19'6.7; Juang a•d Johnmatter in forested watersheds, and (2) the relation of these rates to the ecology of the son, 1967]. This report provides data on the balance forest and to the geochemistry of the watershed minerals. Individual phases of the inves-between the input in precipitation and the discharge in streams of sulfate, ammonium, * This report is contribution number 5 of the nitrate, hydrogen ion, bicarbonate, silica, and Hubbard Brook Ecosystem Study. Published as aluminum for three Hubbard Brook tributary a contribution to the U.S. Program of the International Hydrological Decade and the Inter-watersheds. Considerable information on these national Biological Program. balances in the watersheds studied has been 1115 1116 FI S I--IER ET acquired during the present study (June 19'64 has selected for intensive hydrologic study. through May 1966). I• is anticipated that a These small (12 to 43 hectare) watersheds are subsequent report covering a longer period will outlined in Figure I and designated W-2, W-4, establish more precisely the input-discharge and W-6. Measurements of precipitation and relationships for dissolved mineral matter in of streamflow in the watersheds are obtained intact sections of the forest. Concurrent chem-continuously by Forest Service personnel from ical measurements on the efiluent from a cut-a network of recording rain gages and stream over watershed within the study area are pro-gages. Monthly and annual water budgets are viding information on the effects of disturbances computed for each of the watersheds. Addiwithin the natural environment and, indire...