Effects of Forest Cutting and Herbicide Treatment on Nutrient Budgets in the Hubbard Brook Watershed‐Ecosystem

Abstract

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...

Inorganic nitrogen availability after severe stand-replacing fire in the Greater Yellowstone ecosystem

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Soil warming, carbon–nitrogen interactions, and forest carbon budgets

“…S1 and S2). This approach has been commonly used in large-scale ecosystem manipulations such as the Hubbard Brook Ecosystem Study (47). Results from an earlier soil-warming experiment confirmed that the soil disturbance associated with the installation of heating cables has had no effect on soil temperatures or soil respiration and only minor and variable impacts on soil moisture, net nitrogen mineralization (Fig.…”

Assessing causation of the extirpation of stream macroinvertebrates by a mixture of ions

“…Golladay et al [34] and Arthur et al [35] found increases in nitrogen and phosphorus export in logged catchments in Appalachia but minor differences in calcium, potassium, or sulfate concentrations between logged and undisturbed watersheds. Likens et al [36] actually found sulfate concentrations to decrease following clear-cutting and experimental suppression of forest growth by herbicides.…”