Michael R. McHale

Nitrogen solutes in an Adirondack forested watershed: Importance of dissolved organic nitrogen

Nitrogen (N) dynamics were evaluated from 1 June 1995 through 31 May 1996 within the Arbutus Lake watershed in the Adirondack Mountains of New York State, USA. At the Arbutus Lake outlet dissolved organic nitrogen (DON), NO3- and NH4+ contributed 61%, 33%, and 6% respectively, to the total dissolved nitrogen (TDN) flux (259 mol ha-1 yr-1). At the lake inlet DON, NO3-, and NH4- constituted 36%, 61%, and 3% respectively, of TDN flux (349 mol ha-1 yr-1). Differences between the factors that control DON, NO3+, and NH4+ stream water concentrations were evaluated using two methods for estimating annual N flux at the lake inlet. Using biweekly sampling NO3- and NH4+ flux was 10 and 4 mol ha-1 yr-1 respectively, less than flux estimates using biweekly plus storm and snowmelt sampling. DON flux was 18 mol ha-1 yr-1 greater using only biweekly sampling. These differences are probably not of ecological significance relative to the total flux of N from the watershed (349 mol ha-1 yr-1). Dissolved organic N concentrations were positively related to discharge during both the dormant (R2 = 0.31; P < 0.01) and growing season (R2 = 0.09; P < 0.01). There was no significant relationship between NO3- concentration and discharge during the dormant season, but a significant negative relationship was found during the growing season (R2 = 0.29; P < 0.01). Biotic controls in the growing season appeared to have had a larger impact on stream water NO3- concentrations than on DON concentrations. Arbutus Lake had a major impact on stream water N concentrations of the four landscape positions sampled, suggesting the need to quantify within lake processes to interpret N solute losses and patterns in watershed-lake systems.

Methods of soil resampling to monitor changes in the chemical concentrations of forest soils

Recent soils research has shown that important chemical soil characteristics can change in less than a decade, often the result of broad environmental changes. Repeated sampling to monitor these changes in forest soils is a relatively new practice that is not well documented in the literature and has only recently been broadly embraced by the scientific community. The objective of this protocol is therefore to synthesize the latest information on methods of soil resampling in a format that can be used to design and implement a soil monitoring program. Successful monitoring of forest soils requires that a study unit be defined within an area of forested land that can be characterized with replicate sampling locations. A resampling interval of 5 years is recommended, but if monitoring is done to evaluate a specific environmental driver, the rate of change expected in that driver should be taken into consideration. Here, we show that the sampling of the profile can be done by horizon where boundaries can be clearly identified and horizons are sufficiently thick to remove soil without contamination from horizons above or below. Otherwise, sampling can be done by depth interval. Archiving of sample for future reanalysis is a key step in avoiding analytical bias and providing the opportunity for additional analyses as new questions arise.

Long-term Changes in Soil and Stream Chemistry across an Acid Deposition Gradient in the Northeastern United States

Declines in acidic deposition across Europe and North America have led to decreases in surface water acidity and signs of chemical recovery of soils from acidification. To better understand the link between recovery of soils and surface waters, chemical trends in precipitation, soils, and streamwater were investigated in three watersheds representing a depositional gradient from high to low across the northeastern United States. Significant declines in concentrations of H (ranging from -1.2 to -2.74 microequivalents [μeq] L yr), NO (ranging from -0.6 to -0.84 μeq L yr), and SO (ranging from -0.95 to -2.13 μeq L yr) were detected in precipitation in the three watersheds during the period 1999 to 2013. Soil chemistry in the A horizon of the watershed with the greatest decrease in deposition showed significant decreases in exchangeable Al and increases in exchangeable bases. Soil chemistry did not significantly improve during the study in the other watersheds, and base saturation in the Oa and upper B horizons significantly declined in the watershed with the smallest decrease in deposition. Streamwater SO concentrations significantly declined in all three streams (ranging from -2.01 to -2.87 μeq L yr) and acid neutralizing capacity increased (ranging from 1.38 to 1.60 μeq L yr) in the two streams with the greatest decreases in deposition. Recovery of soils has likely been limited by decades of acid deposition that have leached base cations from soils with base-poor parent material.

Northeastern Hydrologic Benchmark Network (HBN) Soil Chemistry and Catskill Mountain Water-Quality Data

This data product contains soil chemistry data from 4 locations. Two of the locations were located in the Neversink River watershed near Claryville, NY (01435000) in the Catskill Mountains of New York (Fall Brook and Winnisook Creek), 1 of the locations was the Young Woman s Creek watershed near Renovo, PA (01545600) and the last site was the Wild River watershed at Gilead, Maine (01054200). Soil chemistry was collected at 2 times at each location: in 2001 and 2011 in Fall Brook, Young Woman s Creek and Wild River and in 1993 and 2012 in Winnisook. This data product also contains water-quality data from 5 water-quality stations: West Branch Neversink River at Winnisook Lake [01434021], East Branch Neversink River northeast of Denning [0143400680], Rondout Creek above Red Brook at Peekamoose [01364959], Biscuit Brook above Pigeon Brook at Frost Valley [01434025], Neversink River at Claryville [01435000]. The data were collected from water year 1992 to 2014. Stream water discharge is included with each water quality sample. For 3 of the stations (01434021, 0143400680, 01364959) discharge was discontinued in 2012. For those stations, discharge from 2012 to 2014 was estimated using linear regression analyses of nearby or downstream stations. The results of those regression analyses are also included in this data product.