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.

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