stream water chemistry in watersheds receiving different atmospheric inputs of h+, nh4, no3−, and...

JOURNAL OF ThE AMERICAN WATER RESOURCES ASSOCIATIONVOL. 33, NO.4 AMERICANWATER RESOURCES ASSOCIATION AUGUST 1997

STREAM WATER CHEMISTRY IN WATERSHEDS RECEIVING DIFFERENTATMOSPHERIC INPUTS OF H, NH4, NO3-, AND SO42-'

Robert Stottlemyer2

ABSTRACT: Weekly precipitation and stream water samples werecollected from small watersheds in Denali National Park, Alaska,the Fraser Experimental Forest, Colorado, Isle Royale NationalPark, Michigan, and the Calumet watershed on the south shore ofLake Superior, Michigan. The objective was to determine if streamwater chemistry at the mouth and upstream stations reflected pre-cipitation chemistry across a range of atmospheric inputs of H,NH4, NO3-, and SO42-. Volume-weighted precipitation H, NH-,NO3-, and SO42- concentrations varied 4 to 8 fold with concentra-tions highest at Calumet and lowest in Denali. Stream water chem-istry varied among sites, but did not reflect precipitation chemistry.The Denali watershed, Rock Creek, had the lowest precipitationNO3- and SO42- concentrations, but the highest stream water NO3and SO42. concentrations. Among sites, the ratio of mean monthlyupstream NO3- concentration to precipitation NO3- concentrationdeclined (p < 0.001, R2 = 0.47) as precipitation NO3- concentrationincreased. The ratio of mean monthly upstream to precipitationS042 concentration showed no significant relationship to change inprecipitation S042 concentration. Watersheds showed strongretention of inorganic N (> 90 percent inputs) across inputs rangingfrom 0.12 to> 6 kg N ha-1 y-1. Factors possibly accounting for theweak or non-existent signal between stream water and precipita-tion ion concentrations include rapid modification of meltwater andprecipitation chemistry by soil processes, and the presence ofunfrozen soils which permits winter mineralization and nitrifica-tion to occur.(KEY TERMS: watershed; stream water chemistry; precipitationchemistry; input-output budgets; nitrate, sulfate.)

INTRODUCTION

Much debate remains about the effects of acidicdeposition inputs on terrestrial and aquatic ecosys-tems (DeWalle and Swistock, 1994; Driscoll et at.,1988; Jassby et at., 1994; Liegel et at., 1991; Murdochand Stoddard, 1992). Most of the attention is focusedon surface water acidification as a direct result of

precipitation H input. But most North American sur-face waters are moderate-to-well buffered and notdirectly sensitive to precipitation H input (Hirsch etat., 1982; Stoddard, 1994). Many terrestrial ecosys-tems are more sensitive to chronic inputs of inorganicnitrogen (N) and sulfur (S) (Aber et at., 1989; Gunder-sen, 1991). While emissions and deposition of S aredecreasing in many regions of North America (Hirschet at., 1991; Likens, 1992), those of inorganic N arenot (Likens and Bormann, 1995; NADP, 1982-1992).Increased emissions heighten concerns about the pos-sible effects of inorganic N deposition on ecosystems(Aber et at., 1989, 1993; Gundersen, 1991; Jassby etal., 1994).

Trends in stream water chemistry reflect not onlyprecipitation inputs, but also the effects of terrestrialecosystem processes (Likens and Bormann, 1995).Stream water ion concentrations represent the inte-gration of processes such as soil mineral weathering,disturbance, biotic uptake, change in biomass, precip-itation quantity and timing, and snowmelt runoff.Where snowmelt dominates the annual stream hydro-graph, two factors account for most seasonal varia-tions in stream water chemistry: the annualhydrologic cycle, and the degree to which snowmelt ispartitioned between overland and subsurface flow(Bond, 1979; Caine and Thurman, 1990; Stottlemyerand Toczydlowski, 1991; Stottlemyer and Troendle,1992). Meltwater or precipitation chemistry is rapidlyaltered once it enters the soil or rock substrate evenin sensitive alpine ecosystems (Caine, 1989; Campbellet at., 1995; Stottlemyer and Troendle, 1992). A thirdfactor in systems where the snowpack is large is theeffect of unfrozen soils on winter mineral soil process-es such as immobilization of essential nutrients,

1Paper No. 96030 of the Journal of the American Water Resources Association (formerly Water Resources Bulletin). Discussions are openuntil April 1, 1998.

2Research Scientist, U.S. Geological Survey, 240 West Prospect Road, Fort Collins, Colorado 80526.

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOcIATIoN 767 JAWRA

Stottlemyer

mineralization and nitrification. These processes canproduce seasonally large soil reservoirs of inorganicnutrients which further modify the chemistry of pass-ing meitwater.

Few reliable precipitation chemistry data existbefore the late 1970s. One can only make educatedguesses about chemical conditions of the past. Thestudy of forested ecosystems receiving very differentatmospheric inputs can provide some resolution to thequestion of how ecosystems responded to increasedinputs (Driscoll et al., 1988).

In this paper, I compare weekly upstream anddownstream water chemistry collected during 1988-1990 in first-order watersheds which receive differentprecipitation H, NH4, NO3, and S042. inputs. Myobjectives are (1) to see if there are any significantrelationships between present precipitation andstream water chemistry especially at upstream sta-tions, and (2) to examine the feasibility of using pre-sent stream water chemistry from a watershed withlow atmospheriè contaminant inputs as an analog towhat stream water chemistry might be in watershedsnow receiving higher inputs.

Study Sites

METHODS AND MATERIALS

The watersheds are study sites within the ongoinglong-term Watershed Research Program, U. S. Geo-logical Survey or cooperating long-term watershedsites (Fraser Experimental Forest, Colorado, U.S.Forest Service; Denali National Park, Alaska, Nation-al Park Service). In the results reported here, all sam-ples were collected using the same protocols, andanalyzed in the same laboratory at Michigan Techno-logical University, Houghton, Michigan.

Fraser Experimental Forest, Colorado. TheFraser Experimental Forest (FEF) is 137 km west ofDenver, Colorado, west of the Continental Divide.Lexen Creek, the study watershed (124 ha) withinFEF, has a prevailing easterly aspect and ranges inelevation from 2995 m at the watershed mouth to3515 m at the summit of Bottle Peak. The watershed'sbedrock includes remnants of sedimentary sandstoneat upper elevations, while gneiss and schist parentmaterial underlie the entire watershed. Soils aredominated by gravelly sandy loams with alluvial soilsnear the stream. The soils are mostly Inceptisols(Table 1). Resistant bedrock and extensive glaciationof the area — the headwaters originate in a cirque —account for the rugged terrain and inherent low soilfertility (Retzer, 1962; Stottlemyer, unpublisheddata). About 18 percent of the watershed is alpinemeadow which generally occurs above 3350 m eleva-tion. The lower and mid-elevation subalpine forestedslopes with southerly and easterly aspects are domi-nated by lodgepole pine (Pinus contorta Dougl.) whileupper elevations and northerly aspects are vegetatedby Engelmann spruce (Picea engelmannii Parry) —subalpine fir [Abies lasiocarpa (Hook.) Nutt.]. About70 percent of annual precipitation falls as snow.Snowpack water equivalent (SWE) increases sharplywith elevation (Meiman, 1987; Stottlemyer et al.,1996).

Calumet Watershed, Michigan. The Calumet,Michigan, watershed is adjacent to Lake Superior anddue north of the town of Calumet on Michigan'sKeweenaw Peninsula. Watershed elevation variesfrom 190 m to 375 m. The watershed is a first-order,176-ha catchment with NW aspect, uniform slope,moderate topographic relief, and is vegetated mostlyby 65-year old sugar maple (Acer saccharum) andwhite birch (Betula papyrifera Marsh) (Table 1). Thewatershed bedrock is Precambrian metamorphosedPortage Lake volcanics overlain with alkaline glacial

TABLE 1. Watershed Characteristics for Lexen Creek, Fraser Experimental Forest (FEF), Colorado;Calumet Watershed, Upper Peninsula, Michigan; Wallace Lake Watershed, Isle Royale

National Park, Michigan; and Rock Creek, Den au National Park, Alaska.

SiteParameter Lexen Calumet Wallace Rock Creek

Landscape Till Valleys Glacial Till Glacial Till Till ValleyBedrock Gneiss/Schist Meta Volcanics Meta Volcanics Meta VolcanicsSoil Inceptisols Haplorthods Haplorthods CryochreptsVegetation Subalpine/Alpine N. Hardwood Boreal BoreallTundraClimate Continental Great Lakes Great Lakes Continental

Precipitation (cm) 82 88 78 50

JAWRA 768 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION

Stream Water Chemistry in Watersheds Receiving Different Atmospheric Inputs of H, NH4-, NO3-, and S042

till and old beach deposits. Soils are primarily TypicHaplorthods. Weathering of the alkaline till results inmoderately buffered stream water (Stottlemyer andToczydlowski, 1991). Up to 50 percent of annual pre-cipitation occurs as snowfall.

Isle Royale National Park, Michigan. The Wal-lace Lake watershed (115 ha) is located in Isle RoyaleNational Park (ISRO), Michigan, in NW Lake Superi-or about 120 km N of Calumet (Stottlemyer and Han-son, 1989). Watershed elevation varies from 190 to275 m. Watershed vegetation is dominated by trem-bling aspen (Populus tremuloides Michaux), whitebirch, and white spruce [Picea glauca (Moench) A.Voss]. The bedrock is metamorphosed volcanics cov-ered by scattered alkaline glacial till originallyderived from limestone bedrock immediately south ofJames Bay. The soils are primarily Alfic Haplorthods,sandy to coarse loamy, mixed, frigid, and are between3000 to 5000-years old. Parent materials are sandsand beachline deposits laid down during the post-glacial Lake Nipissing stage. About 50 percent ofannual precipitation occurs as snowfall.

Denali National Park, Alaska. The Rock Creekdrainage (770 ha) is located north of Denali NationalPark headquarters. The watershed has a south-south-eastern aspect, and ranges in elevation from 640 to1700 m. The watershed is underlined with metavol-canic quartz shist and some marble. The bedrock isoverlain by glacial deposits near the watershedmouth. Soils are not mapped, but likely are Alfic Cry-ochrepts. Mid-age (100+ years) white spruce and 50-year old trembling aspen dominate vegetation in thelower quarter of the watershed. At lower elevationswith eastern or southeastern aspects open blackspruce (Picea mariana [Mill.] B.S.P.) occurs withwhite spruce and Betula glandulosa Michaux.Upstream from the coniferous and mixed forest is aband of closed tall scrub dominated by Alnus crispaand Salix. Mixed mesic shrub (Betula, Ericaceae)occurs at elevations above the tall scrub. Most of thewatershed is dominated by patches of mesic to dryDryas tundra. About 50 percent of annual precipita-tion occurs as snowfall.

A number of characteristics are common among thesites (Table 1). Snowmelt dominates annual streamwater discharge (Stottlemyer, 1992; Stottlemyer andHanson, 1989; Stottlemyer and Toczydlowski, 1991;Stottlemyer and Troendle, 1992). Snowmelt occurs inlate March and April in northern Michigan, and lateMay and June at Fraser and Denali. Except for RockCreek, sites receive similar annual precipitationamounts. Runoff at all sites is 45-55 percent of precip-itation inputs. Earlier studies of changes in streamwater chemistry during snowmelt, nutrient cycling

and budgets, show high retention of H (> 95 percent)and inorganic N (> 90 percent) input at all sites whileS outputs exceed precipitation inputs. Except forCalumet, vegetation has some similarities amongsites (Table 1), and is dominated by Picea, Abies,Pinus, Betula, and Pop ulus. The Calumet site is domi-nated by Betula and Acer. With increased latitude(Rock Creek) and elevation (Lexen Creek) coniferspredominate. In the forested portions of these water-sheds, the predicted annual C fixation is similar (100-200 g C/m2/yr; Reichle, 1973). None of thesewatersheds have been recently disturbed by directhuman use. The only known disturbances are aground fire in Wallace 60 years ago which burnedabout 20 percent of the watershed, and some selectivetimber cutting in Calumet about 75 years ago.

Field Sampling

Precipitation amount is recorded at all sites usingBelfort raingages. In the Calumet watershed, precipi-tation amount is recorded at mid-elevation. Thevolume-weighted precipitation chemistry for this siteand study, however, is from the National AtmosphericDeposition Program (NADP) station M199, in opera-tion since 1982 and located 21 km from the water-shed. The NADP uses Aerochem Metrics collectors("event collectors") for precipitation chemistry. AtWallace, mid-winter access limitations require thatprecipitation chemistry be measured with bulk collec-tors. In winter, the collector is a plastic-lined 1.5 mlong, 20.5 cm diameter tube. In summer, the collectoris a plastic, 10 cm diameter tube fitted with funneland pre-rinsed ashless filter to reduce evaporationand dust entry. The elevation of the collectors is 210m. At Lexen Creek, precipitation chemistry is deter-mined from two Aerochem Metrics samplers one oper-ating at 2725 m elevation near the base of thewatershed and another at 3350 m elevation near thetop of the watershed. The NADP protocol is used withthe samples analyzed in our laboratory. At RockCreek, precipitation chemistry from NADP stationAKO3 is used. This station is located at the mouth ofthe watershed.

Stream water discharge is monitored continuouslyat all sites. At Lexen, a 120 V-notch weir is used. AtCalumet and Wallace, Parshall flumes are used, andat Rock Creek a natural flume is gauged. Stevens Frecording gauges were used at all sites during thestudy reported here, except for Lexen where dischargewas recorded by punch tape.

Lexen Creek has four stream sampling stationslocated along an elevation gradient. The lowest eleva-tion station (2995 m) is at the watershed mouth. The

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 769 JAWRA

3200 m elevation station is 1.0 km from the mouth,the 3305 m elevation station 1.5 km, and the 3415 melevation station 1.76 km. At Calumet, Michigan, thedownstream station (190 m elevation) is located at themouth of the watershed, and the upstream gauge (325m elevation) 2.4 km from the mouth. At Wallace, thedownstream sampling station (190 m elevation) islocated at the mouth of the watershed, and theupstream gauge (220 m elevation) 0.9 km from themouth. Rock Creek, like Lexen Creek, has fourstream sampling stations located along an elevationgradient. The lowest elevation station is at the mouth(640 m elevation) of the watershed. The 750 m eleva-tion station is 1.8 km from the mouth, the 850 m sta-tion 3.0 km, and the 1110 m elevation station 4.8 km.

Stream water samples are collected weekly year-round at Calumet, from April to November at Wallaceand Lexen with periodic samples collected in winter,and early June to late October for Rock Creek. Duringrapid changes in the stream hydrograph, sampling isdaily or more frequent, depending on the magnitudeof diurnal change. Samples are collected in twice-rinsed 500-ml amber polyethylene bottles, and streamwater temperature, discharge, and sampling timerecorded.

Laboratory Analyses

Samples are brought immediately to a field labora-tory except for the Calumet samples which are direct-ly returned to our laboratory at MichiganTechnological University. For precipitation andstream water samples, pH, specific conductance, andalkalinity (titration with 0.02 N H2S04 to pH 4.5,stream water samples only) are determined as soon assamples reach room temperature. Separate filtered(pre-rinsed, 0.45 .im) subsamples for ion analyses arerefrigerated at 2CC. The filtered subsamples areshipped in coolers to our laboratory at Michigan Tech-nological University. Calcium, Mg2, Na, K, NH4,NO3, SO42-, and Cl- concentrations are determinedusing a Dionex Model 2020 ion chromatograph. Labo-ratory and field sampling procedures remained con-stant during the study. Quality assurance/qualitycontrol procedures in place during the study aredescribed in Stottlemyer (1987).

For quality assurance between our laboratory andthe NADP, since 1982 we have split weekly samplesfrom NADP station M199 running one split throughour laboratory. There are no significant differences (ttest) between ion concentrations from the NADP Cen-tral Analytical Laboratory and our laboratory. To com-pare chemistry between bulk and the eventprecipitation collectors (Aerochem Metrics), since1986 bulk collectors, as described above, have been

located 10 m from the NADP station M199 AerochemMetrics collector. Bulk collector and split M199 sam-ples are analyzed in our laboratory using the sameanalytical procedures as NADP. Concentrations ofCa2, Mg2, Na, NO3-, SO42- and Cl- in bulk precipi-tation were significantly higher (t test, p < 0.05) thanin samples from the Aerochem Metrics collector dur-ing this study (1988-1990), and during the ten yearsthe bulk collector has been in place.

Data Analyses

Precipitation chemistry are summarized for tenyears (1983-92), during which continuous recordsexist for all sites. The ten-year record permits analy-ses of seasonal and annual trends in atmospheric con-taminant concentrations which might help interpretstream water chemistry during the 1988-1990 study.To assess seasonal changes in precipitation chemistry(Figure 1), monthly volume-weighted means are com-puted for each ion from all samples collected in agiven month. Mean annual volume-weighted precipi-tation concentration is computed for each ion eachyear for comparison among years (Figure 2).

For stream water chemistry, only the period 1988-90 is used. With the short period, changes amongyears are not examined. To assess seasonal changes instream water chemistry, the same methods are usedas for precipitation. To compare seasonal change inprecipitation chemistry to stream water chemistry,the period of record is the same for both precipitationand stream water (1988- 1990).

Systat modules are used for time series andANOVA analyses of seasonal and annual differencesin precipitation and stream water chemistry (Wilkin-son, 1990). The procedures are as follows. The routineleast squares model is first used to show ion concen-tration against time (Figures 1-5) with the residualssaved to test independence. An autocorrelation plot ofregression residuals is then performed. If the autocor-relations are not significant, the time trend is thatdefined by the regression. Most variables do notexhibit significant autocorrelation. When autocorrela-tions are significant, i.e. outside the two-standarderror confidence band, the independence of observa-tions is suspect. Autocorrelation is then removed bydifferencing, and the transformed (differenced) vari-ables checked for autocorrelation. If there is a signifi-cant autocorrelation remaining, a cross correlationfunction plot of differenced variables is run. Then alagged regression on the transformed variables is per-formed, adjusted for the appropriate lag interval. Ifthe lagged regression is significant (p < 0.05) andthere are no warnings of outliers or other influence,the model is used to explain the trend. If the lagged

Stottlemyer


Stream Water Chemistry in Watersheds Receiving Different Atmospheric Inputs of H, NH-, NO3-, and S042

Figure 1. Monthly Mean Precipitation Chemistry for SelectedSpecies, 1983-92, Lexen Creek, Fraser Experimental Forest,Colorado; Calumet, Michigan (NADP Station M199); WallaceLake Watershed, Isle Royale National Park, Michigan; and

Rock Creek Watershed, Denali National Park, Alaska.

83 84 85 86 87 88 89 90 91 92

Figure 2. Mean Annual Precipitation Chemistry forSelected Species, 1983-1992, for Stations in Figure 1.


60

50

.J An

30

20

10

0

-Ia.w

a.

-Ja.0

-Ia.0

::H40

30

20

/N/N .,/ N

NN

10

060

50

40

::

':60

50

40

30

20

10

060

50

40

30

-

.-—I

60

50

..140

::

':60

40

30

20

10

0

60

50

40

30

NH +

•-------—Rock Creekir -—— Calumet"3 ---Wallace

Lexen Creek— . N -

•_:._._

2—'LI ,4 //

'N\ /\

H"S 'S .

— —

NN - ..' '

N N

NH4

- —Rock CreekNO -- çalumet3 --- Wallace

Lexen Creek

— — - _ - .—

SO42-

—N N

3

2

04

3

2

0

N03/S04

.:..NO3/NH4S,

J F MAMJ J AS ONDMonth

N03/S04

0

4

3

2

012

10

8

6

4

2

0

N03/NH4

Year

Figure 3. Mean Monthly Stream Water Ca2 Concentration(unweighted) for Upstream and Downstream Stations During

1988-90. Data for Rock Creek are for 1988, the only yearupstream stations were sampled weekly. Maximum monthlystandard deviation shown as vertical bar on right hand side.

Figure 4. Mean Monthly Stream Water NO Concentration(unweighted) for Upstream and Downstream Stations During



Rock Creek /

Elev.Elev.Elev.Elev.

/

640 m ______750m850 m1110 m

Rock Creek

640 m ____750 m850 m1110 m

Lexen Creek

EIev. 2995 m ______EIev. 3200 mElev. 3305 mEIev. 3415 m

Lexen Creek

2500

2000

1500

1000

C.,

500

01500

1000

a.w

500

01500

-j

a.0

C.,

01500

1000

a.0

, 500

EIev.Elev.Elev.EIev.

2995 m ______3200 m3305 m3415 m

1000

Stottlemyer

40

30

a.

20

-: Elev.Elev.

10 .Elev.Elev.

040

30

-j

a.0i. 20

0z10

040

30

-Ia.

20

0z10

040

30

-j

a.

20

0z10

0

500

Wallace

UpstreamDownstream

7/

Wallace

UpstreamDownstream ______

• I

Calumet

Upstream — — —


Calumet

UpstreamDownstream


Stream Water Chemistry in Watersheds Receiving Different Atmospheric Inputs of H, NB4, NO3-, and S042


-jw

0(1)

12000 -

10000Rock Creek 7

8000

//__6000

4000 Elev. 640 m _____Elev. 750 m

2000 Elev. 850 mElev. 1110 m

Lexen Creek

Elev. 2995 m ______Elev. 3200 mElev. 3305 mElev. 3415 m

regression is significant but contains outlier or otherinfluence warnings, a subsequent autocorrelation plotand Runs test (Systat NPAR module) of the residualsfrom the transformed variables is conducted.

RESULTS

Precipitation

Precipitation chemistry among sites is verydifferent (Figures 1 and 2; Tables 1 and 2). Volume-weighted H, NH4, NO3-, and SO42- concentrationsare four to eight times higher at Calumet than RockCreek. The total strength of these ions (equivalentbasis) at Calumet is five times that at Rock Creek.

TABLE 2. Mean Volume-Weighted Precipitation IonConcentration (teq L4) for Selected Species, 1983-1992

(standard deviation is in parentheses).

0150

1000

0 50

0150

.jIOOa.

0 50

0150

•E.iiooa.w

50

0

— -

I I I

—

I I

WallaceUpstream — — —Downstream

/\/\\_

I I I I

Site

IonFraser

AerochemCalumet

Aerochem

IsleRoyaleBulk

RockCreek

Aerochem

NH4 5(5) 18(18) 14(20) 3(2)

H 5(3) 19(19) 27(26) 6(3)

NO3- 10(6) 23(18) 17(15) 3(1)

SO42- 17(14) 32(26) 34(20) 8(4)

Upstream — — —Downstream ______

J F MA M J J A SMonth

0 ND

During 1983-1992, significant trends in seasonalprecipitation chemistry occur only at the Michigansites. At Calumet, mean monthly SO42- concentra-tions decline (p <0.001, R2 = 0.11) during the year asdoes the N03/S042- ratio (p < 0.01, R2 = 0.22). AtWallace, the mean monthly NO3- concentrationsdecline (p < 0.001, R2 = 0.36) during the year as doesthe N03/S042 ratio (p < 0.001, R2 0.22). The sea-sonal trend in N031S042- ratio is similar to Calumet.

During the 1988-1990 study, the Calumet precipi-tation NO3iNH4 ratio was lower in summer (t test,p< 0.05) than winter. At Wallace, summer H (p <0.05) and NO3- (p < 0.05) concentrations and NO3-ISO42- (p < 0.001) ratios are less than in winter. AtLexen, summer NO3/SO42 ratios (p < 0.001) and H'-(p < 0.05) concentrations are lower than in winter.

During 1983-1992, mean annual volume-weightedprecipitation H concentrations decline at Wallace (p< 0.05, R2 = 0.43, Figure 2). Sulfate concentrationsdecline at Calumet (p < 0.05, R2 = 041), Lexen Creek(p < 0.05, R2 = 0.37), and Rock Creek (p < 0.05, R2 =

Figure 5. Mean Monthly Stream Water SO42- Concentration(unweighted) for Upstream and Downstream Stations During


Stottlemyer

0.45). At Lexen Creek, the decline in S042 relative toNO3- increases the N031S042 ratio during thedecade (p = 0.05, R2 = 0.37). Ammonium makes upmost of the inorganic N concentration and input at allsites (Lexen Creek 68 percent, Calumet 74 percent,Wallace 69 percent, Rock Creek 88 percent).

Stream Water

Dominant stream water ions are Ca2 and HC03except at Rock Creek where Mg2 is the dominantcation. Calcium, a conservative ion with much greaterconcentrations in stream water than precipitation,has higher mean concentrations at lower elevationstations except for Rock Creek (Figure 3). Meanstream water Ca2 concentration declines duringsnowmelt at most stations (Figure 3, Table 3), butonly the decrease at Calumet is significant (p < 0.05).Stream water Ca2. concentration at the Lexen Creekalpine station does not decline during snowmelt. Themean total base cation (CB) concentration is highestat the downstream station of all watersheds exceptRock Creek where the CB concentration is greater atthe 850 m elevation station.

Hydrogen and NH4 inputs are retained in allwatersheds. Changes in stream water H and NH4concentration during snowmelt are generally < 10 peqL-1, and only the NH4 decline at Wallace is signifi-cant (p < 0.05). During most of the year, stream waterconcentrations are low (< 5 .ieq L'), and consequentlyare not graphed. No trend is evident in upstream-downstream H or NH4 concentrations.

Nitrate is retained in all watersheds except RockCreek. During winter, stream water NO3 concentra-tions at Calumet, Wallace, and the downstream Lexenstation increase (Figure 4). Stream water NO3- con-centrations decline during and following snowmelt(Figure 4, Table 3), and the decrease is significant(p < 0.05) at Calumet, Wallace, and the upper sub-alpine (3305 m elevation) station of Lexen Creek. At

upstream stations, Calumet and Wallace show similarsharp declines in NO3- concentration followingsnowmelt, while Lexen and Rock exhibit less decline.Lexen and Rock have slight increases and Calumeta sharp increase in upper elevation stream waterNO3- concentration concurrent with early snowmelt(Figure 4).

Mean upstream NO3- concentrations are greaterthan downstream at Calumet (t test, p < 0.01), Wal-lace (p < 0.05), and Lexen (p < 0.001). At Lexen,stream water NO3- concentration decreases as thestream enters the subalpine forest (elev. 3305 m, Fig-ure 4). Upstream NO3- concentrations are lower thandownstream at Rock Creek (p < 0.01). Rock CreekNO3- concentrations are similar at the lower two sta-tions. For all sites, the ratio of mean monthlyupstream NO3- concentration to precipitation NO3-concentration is inversely related (p < o.ooi, R2 =0.47) to precipitation NO3- concentration. At Wallace,monthly precipitation and downstream water NO3concentrations are positively related (p < 0.05, R2 =0.26).

Stream water SO42 concentrations show seasonaltrends similar to Ca2 (Figures 3 and 5). The declinein stream water SO42 concentration after snowmelt ismost pronounced at Wallace, but the decrease is notsignificant. As with Ca2, SO42 concentration at thealpine Lexen station shows little change during andfollowing snowmelt.

Mean SO42 concentrations are greater at themouth of Lexen, Calumet, and Wallace. For all sites,the ratio of mean monthly upstream S042- concentra-tion to precipitation SO42 concentration shows no sig-nificant trend as precipitation S042. concentrationincreases.

TABLE 3. Percentage Change in Downstream (D) and Upstream (U) Water Ion Concentration During and ImmediatelyFollowing Snowmelt. Base period was average concentration for month before snowmelt. Data for Fraser are from LexenCreek 1989-1990; Calumet from 1989-1990; Isle Royale from Wallace Creek, 1989-1990; Denali from Rock Creek, 1988.

Ion

SiteLexen Creek Calumet Wallace RockCreekD U D U D UD U

Ca2NO3-

SO42-

-12

-90

-21

+30

-17

+27

-32

-80

-28

-27

-79

-20

-30

-85

-67

-37

-79

.59

-10

-27

-13

-27

-8

-34


Stream Water Chemistry in Watersheds Receiving Different Atmospheric Inputs of W, NTL, NO3-, and S042

Precipitation

The Michigan sites appear the only ones where sea-sonal change in precipitation chemistry might affectstream water chemistry. At Calumet and Wallace, Iattribute the increase in precipitation SO42- concen-tration during March and April to the shift in winddirection in the Upper Midwest region from the NWto SE (Semkin and Jeffries, 1988; Stottlemyer andToczydlowski, 1991). However, seasonal precipitationSO42- input changes little. At the Michigan sites,mean monthly precipitation amount averages 6.2-6.5cm but the monthly mean for March and April is 4.6cm (NADP, 1982-92). The decrease in precipitationamount reduces wet precipitation S042 input.

In winter, precipitation input is temporarily storedin the snowpack, and with snowmelt the snowpackion content can be released into stream water. Snow-pack ion content can be large in regions of high snow-fall and precipitation ion concentration. But, at theMichigan sites periodic thaws throughout winter arecommon, and the snowpack solute content is oftenreduced > 50 percent before peak snowmelt (Stottle-myer and Toczydlowski, 1991, 1996).

At the Michigan sites, I attribute the decline inMay-August NO3- and May-December SO42- concen-trations to the seasonal shift in wind direction fromthe SE to the SW, W, and NW bringing in cleaner air.The net effect of the declines reduces the meanmonthly NO31S042- ratio through mid-summer (Fig-ure 1). Precipitation NH4 concentrations decrease atWallace during summer, but remain high at Calumet.The seasonal NO3- and NH4+ trends result in highsummer NO3-fNH4 ratios at Wallace and low ratiosat Calumet. Calumet's closer proximity to feedlotsand fertilized fields, a major NH4 source in thisregion (Glass and Loucks, 1986), is the likely cause.

At Lexen Creek, precipitation NH4, NO3- andSO42 concentrations increase during summer.Ammonium concentrations increase relative to NO3-which reduces summer precipitation NO3/NH4ratios, but not significantly. Increased summer fertil-izer and feed lot emissions in this region result insimilar NH4 trends at other Colorado sites (Lynch etal., 1995; Sievering et al., 1992). The increase in sum-mer precipitation NO3- concentration is consistentwith that observed in Front Range sites (Campbell etal., 1995), and in the NADP. Other studies showdry deposition N inputs can exceed wet precipitationinputs which could also change these ratios. However,dry deposition is not monitored at or near thesesites. The increased seasonal precipitation concentra-tions are concurrent with the months precipitation

occurred as rain. The greater scavenging capacity ofrain relative to snow, possibly coupled with increasedaerosol concentrations, could account for the increasein summer precipitation ion concentration.

During 1983-1992, the decline in precipitationSO42- concentration observed at several sites is con-sistent with other regional and national observations(Lynch et al., 1995), and has been attributed toreduced emissions (Likens, 1992; Murdoch and Stod-dard, 1992). I ascribe the lack of a significant trend inWallace precipitation SO42 concentration to the high-er variance in precipitation chemistry from bulk col-lectors. For example, at NADP station M199 thestandard deviation of mean volume-weighted SO42-concentration from the bulk collector is 38 percentgreater than the Aerochem Metrics collector during1988-1990.

Ammonium is the main contributor of elemental Nin wet precipitation. This indicates the importance ofland use practices, especially feed lots and the appli-cation of fertilizer, on regional and local precipitationquality (Glass and Loucks, 1986). In a recent nation-wide analysis of trends in NADP precipitation NH4concentration (Lynch et al., 1995), the number andpercentage of sites with increasing NH4 concentra-tion goes up substantially as length of the summaryperiod decreases from the present. The NH4 concen-tration increases are especially pervasive since 1983in the west. In the present study, ecosystem input ofNH4 is high at most sites, but except during mid-winter thaws, little NH4 is exported in stream water(Stottlemyer and Toczydlowski, 1991). Longer termstudies of soil water in Lexen, Calumet, and Wallaceshow rapid exchange and retention of precipitation orthroughfall NH4 in surface mineral soils (Stottlemy-er and Hanson, 1989; Stottlemyer and Toczydlowski,1996; Stottlemyer and Troen dIe, 1992; Stottlemyer etal., 1995, 1996). Forest vegetation in three of the fourwatershed study sites is predominantly conifers.Conifers may preferentially use NH4 (Reuss andJohnson, 1986).

Stream Water Chemistry

Where the annual stream hydrograph is dominatedby snowmelt runoff, a major factor affecting change inseasonal and annual stream water chemistry is varia-tion in the flow path of precipitation and snowmelt tothe stream (Bond, 1979; Huntington et al., 1994;Kaufmann et al., 1991; Lettenmaier et al., 1991; Stot-tlemyer and Toczydlowski, 1991, 1996; Stottlemyerand Troendle, 1992). Of particular importance is howsnowmelt is partitioned between surface overlandflow and soil water. With unfrozen soils throughoutwinter, most snowmelt penetrates forest soils at


DISCUSSION

Stottlemyer

Calumet, Wallace, and Lexen (Stottlemyer et al.,1996; Stottlemyer and Toczydlowski, 1991, 1996; Stot-tlemyer and Troendle, 1992). Because of the snowdepth at Rock Creek, unfrozen soils likely exist exceptin the tundra, but this is not quantified. Subsurfaceflow of snowmelt quickly alters its chemistry (Fosteret al., 1989; Stottlemyer and Toczydlowski, 1996).The degree to which snowmelt penetrates soils can beestimated by comparing change in stream water con-centrations for ions with high soil water concentra-tions (Ca2) to those with high precipitation orsnowpack concentrations (H, NH4, NO3-, SO42-)(Caine, 1989; Caine and Thurman, 1990; Stottlemyerand Toczydlowski, 1991; Stottlemyer and 'Froendle,1992).

Stream water Ca2 concentrations greatly exceededthose in precipitation in these watersheds. Soil miner-al weathering and cation exchange are the mainsources of stream water base cations (CB) in mostregions, even for sensitive surface waters (Charles,1991; Kaufmann et al., 1991). In this study, Ca2 isgenerally the dominant stream water CB. The magni-tude of seasonal change in stream water Ca2 concen-tration can decrease with increased watershed area orincreased contributions of deeper soil water (Driscollet al., 1988).

All downstream and most upstream stations in thewatersheds show a seasonal dilution of stream waterCa2 concentration during snowmelt. The decline instream water Ca2 concentrations is characteristic ofwatersheds where snowmelt seasonally changes therelative contributions of surface and near-surfacemineral soil water to deeper, more concentrated soilwater (Caine, 1992). The reduced seasonal change instream water Ca2 concentrations at all stations inLexen Creek and some Rock Creek stations indicatehigh, year-round, deep soil water contributions tostream water. The Lexen Creek alpine station showsminor seasonal change in Ca2 concentration eventhough its watershed area is small. The stream gaugeat this station exhibits little diurnal change in dis-charge even during peak snowmelt, and little or nooverland flow is observed (Stottlemyer, unpublisheddata). Snowmelt, while large at this elevation, easilypenetrates the thawed, coarse-textured soils or isevaporated (Stottlemyer et al., 1996; Troendle et al.,1993). Trajectories of time, discharge, and streamwater ion concentration in another FEF alpine water-shed show similar results (Stottlemyer and Troendle,1992).

Except at Rock Creek, mean precipitation inorganicN concentrations exceed stream water concentrations.Reduced downstream NO3- concentrations arecommon in watershed ecosystems receiving a widerange of atmospheric NO3- inputs (Lewis and Grant,1980; Likens and Bormann, 1995; Stednick, 1989;

Stottlemyer and Troendle, 1992). In the West andAlaska where atmospheric inputs of inorganic N arestill relatively low, high stream water NO3- concentra-tions are generally associated with the presence ofnitrogen fixers and/or poor ecosystem retention(Edmonds et al., 1995; Stottlemyer, 1992). Nitrogenfixers, as Alnus, are scattered in the riparian zone ofall study sites except Calumet.

In the eastern U.S., there is evidence that atmo-spheric NO3- might be reaching headwater streams,and could account for the increased NO3- concentra-tions observed in streams since 1970 (Kaufmann etal., 1991; Murdoch and Stoddard, 1992). The potentialfor precipitation NO3- entering a stream is greaterwhere the annual hydrograph is dominated bysnowmelt. However, in the present study, the meanupstream water to precipitation NO3- concentrationratio significantly declines as precipitation NO3- con-centrations increased. The mean upstream water/precipitation NO3- concentration ratio is lowest (0.39)at Calumet and highest (7.0) at Rock Creek whereprecipitation NO3- concentration is 13 percent that atCalumet. Other recent studies suggest for NorthAmerica the amount of precipitation NO3- enteringthe stream is still small even where a snowpack exists(Hedin, 1994). In British Columbia, greater than 80percent of recovered 15N-labelled fertilizer, applied tothe snowpack beneath forests dominated by lodgepolepine and Douglas fir (Pseudotsuga menziesii (Mirb.)Franco), was found still in the soil after one year (Pre-ston et al., 1990).

At other sites, high stream water NO3- concentra-tions in winter and during snowmelt are correlatedmore to soil water NO3- concentrations than precipi-tation inputs (Foster et al., 1989). In a subalpine for-est of central Colorado, during early snowmelt theflushing of soil water N, C, and S is thought an impor-tant influence on stream water chemistry (Arthur andFahey, 1993). Lewis and Grant (1980) attribute win-ter and early spring NO3- concentration pulses inComo Creek, Colorado, to soil freezing and reducedbiological sequestering by nitrification. Contributionsof soil inorganic N to stream water may become moreimportant than atmospheric deposition or snowpackinorganic N content when soils beneath the snowpackare unfrozen and spring snowmelt mixes with soilwater. These processes would help account for thehigh winter stream water NO3- concentrationsobserved in this study. With initial snowmelt, "older"soil water can be forced out (Abrahams et al., 1989,Campbell et al., 1995, Rascher et al., 1987) resultingin a small "pulse" or increase in stream water NO3and other ion concentrations. In this study, onlyCalumet and Lexen show such increases in ion con-centration during snowmelt. However, monthlymeans are not very sensitive in detecting elevated


Stream Water Chemistry in Watersheds Receiving Different Atmospheric Inputs of H, NH, NO3-, and S042

stream water ion concentrations generally lasting < 3days.

At Wallace, the size of extractable soil inorganic Npools indicates the potential importance of soil waterion contributions. Mean monthly soil inorganic Npoois (top 10 cm) vary at Wallace between 1.5 and 4.5kg ha-1 (Stottlemyer et al., 1995) depending on vege-tation type. Winter values average about 2 kg ha-1.These amounts far exceed mean monthly precipita-tion inorganic N inputs and peak snowpack N con-tent. At Rock Creek, net soil mineralization andnitrification during summer alone exceeds 3 kg Nha4, or 30 times annual precipitation inorganic Ninput (Stottlemyer, 1992). With such large soil inor-ganic N pools compared to precipitation inputs cou-pled with penetration of precipitation and snowmeltinto the soil, it is likely NO3- observed in streamwater is coming from the soil, not directly from pre-cipitation.

The general absence of relationships between pre-cipitation and stream water chemistry is more evi-dence that precipitation inputs likely have littleinfluence on seasonal changes in stream water chem-istry at these sites. The significant relationshipbetween precipitation and downstream water NO3-concentration at Wallace probably is not cause-effect.This watershed retains > 85 percent of inorganic Ninputs (Stottlemyer and Hanson, 1989). Wallacestream water NO3- concentration trends closely followthe seasonal trend observed in net soil N mineraliza-tion rates (Stottlemyer et al., 1995). With the largesoil inorganic N pools at Wallace and passage of melt-water through the forest soil, seasonal stream waterNO3- trends likely reflect changes in soil water.

The seasonal decline in stream water NO3- concen-tration, shown by the upstream and downstream sta-tions at Calumet, Wallace, and the downstreamstation at Lexen, during and after snowmelt is char-acteristic of watersheds with high inorganic N reten-tion during the growing season (Stoddard, 1994). Theupper elevation stations at Lexen Creek and RockCreek do not show much decline in NO3- concentra-tion. I attribute the sustained higher alpine streamwater NO3- concentrations at Lexen to meltwaterspassing through the soils picking up mobile NO3-, andpoor inorganic N retention from limited biological pro-ductivity. Stream water NO3- concentrations aregreatest at Rock Creek. The relatively high soil inor-ganic N fixation and mineralization rates in thisecosystem compared to retention capacity, even insummer, are the likely cause (Stottlemyer, 1992).

In contrast to inorganic N, previous studies ofwatershed ion budgets show SO42- outputs to exceedinputs at these sites (Stottlemyer, 1992; Stottlemyerand Hanson, 1989; Stottlemyer and Toczydlowski,1991; Stottlemyer and Troendle, 1992). The Michigan

sites, like most eastern locations, experienced highatmospheric SO42- inputs for decades, and this couldpartly account for the large sulfur output. In thisregion, elevated extractable soil S042 and decreasedcapacity to adsorb more SO42 are related to past andpresent S042- deposition (MacDonald et al., 1993). AtCalumet, the volume-weighted S042- concentration insnowmelt increases as it passes through the forestfloor and surface mineral soils (Stottlemyer andToczydlowski, 1996). This trend indicates the poten-tial importance of processes as organic mineraliza-tion, low soil adsorption, and desorption in regulatingSO42 concentration and flux. Sulfate concentrationalso increases downstream in the Calumet watershedindicating the significance of increased hydrologicpathlength (Driscoll et al., 1988). At Wallace, soilwater S042- concentration and flux also increase withsoil depth (Stottlemyer and Hanson, 1989), andstream water SO42 concentrations increase down-stream.

The Lexen Creek watershed is in a region with lit-tle historical precipitation data and lower SO42- emis-sions and deposition (NADP, 1991). Lexen streamwater SO42 concentrations are 35-50 percent those ofthe Michigan sites. As in the Michigan sites, soilwater S042 concentrations exceed those in precipita-tion and the snowpack indicating the importance ofsoil processes in modifying snowmelt chemistry (Stot-tlemyer et al., 1996). Lexen stream water SO42 con-centrations increase with decreasing elevation whichI interpret as the addition of S042 from soil processescoupled with increased hydrologic pathlength.

Mineral weathering can be a major contributor toSO42- exports as seen in the large S042 concentra-tions in Rock Creek. Rock Creek stream water SO42concentrations are related to Mg2 (p < o.øoi, R2 =0.90) and Ca2 (p < 0.001, R2 = 0.84) concentrationsindicating SO42 is a weathering product. Except forRock Creek where easily eroded shales and dolomiticmarble result in elevated upstream SO42 and Mg2concentrations (Stottlemyer, 1992), the reducedupstream S042 concentrations in this study are oppo-site what one might expect if precipitation orsnowmelt SO42- inputs dominated stream water con-centrations.

In sum, regardless of the H input to these sites,the release of CB by soil exchange and chemicalweathering neutralizes acidity inputs. The space-for-time model using these sites indicates little, if any,alteration of stream water chemistry by precipitationacross a range of atmospheric inputs. Other factorsmust account for the weak or non-existent signalbetween stream water and precipitation ion concen-trations. For these sites, potentially important factorsare the rapid modification of meltwater and precipita-tion chemistry by soil processes, and the presence of

JOURNAL OF THE AMERICAN WATER RESOURCES AssociATioN 777 JAWRA

Stottlemyer

unfrozen soils which permits winter mineralizationand nitrification to build relatively large ion poolsthat mix with penetrating snowmelt water.

ACKNOWLEDGMENTS

This research was supported by the Watershed Research Pro-gram, National Park Service and National Biological Service; theNational Acid Precipitation Assessment Program, Washington,D.C., and the U.S. Forest Service Rocky Mountain Forest andRange Experiment Station (RMF and RES), Ft. Collins, Colorado.Technical assistance in sample collection and analyses was provid-ed by Jeff Braun, RMF and RES; Dan Markowitz, Duke University;Manual Martinez, RMF and RES; K. McLoone, D. Toczydlowski,P. Toczydlowski, and B. Travis, Michigan Technological University,Houghton, Michigan.

LITERATURE CITED

Aber, J. D., K. J. Nadelhoffer, P. Steudler, and J. M. Melillo, 1989.Nitrogen Saturation in Forest Ecosystems. BioScience 39:378-386.

Aber, J. D., A. MaGill, R. Boone, J. M. Melillo, P. Steudler, andR. Bowden, 1993. Plant and Soil Responses to Chronic NitrogenAdditions at the Harvard Forest, Massachusetts. EcologicalApplications 3(1):156-166.

Abrahams, P. W., M. Tranter, T. D. Davies, and I. L. Blackwood.1989. Geochemical Studies in a Remote Scottish Upland Catch-ment: II. Stream Water Chemistry During Snow-melt. Water AirSoil Pollut. 43:231-248.

Arthur, M. A. and T. J. Fahey, 1993. Controls on Soil SolutionChemistry in a Subalpine Forest in North-Central Colorado.Soil Science Society America Journal 57(4):1122- 1130.

Bond, H. W., 1979. Nutrient Concentration Patterns in a StreamDraining a Montane Ecosystem in Utah. Ecology 60(6):1184-1196.

Caine, N., 1989. Hydrograph Separation in a Small Alpine BasinBased on Inorganic Solute Concentrations. Journal of Hydrology112:89-101.

Caine, N., 1992. Modulation of the Diurnal Streamflow Responseby the Seasonal Snowcover of an Alpine Basin. Journal ofHydrology 137:245-260.

Caine, N. and E. M. Thurman, 1990. Temporal and Spatial Varia-tions in the Solute Content of an Alpine Stream, Colorado FrontRange. Geomorphology 4:55-72.

Campbell, D. H., D. W. Clow, G. P. Ingersoll, M. A. Mast, N. E.Spahr, and J. T. Turk, 1995. Processes Controlling the Chem-istry of Two Snowmelt-dominated Streams in the Rocky Moun-tains. Water Resources Research 31(11):2811-2821.

Charles, D. F. (Editor), 1991. Acidic Deposition and Aquatic Ecosys-tems: Regional Case Studies. Springer-Verlag, New York, NewYork, 730 pp.

DeWalle, D. R. and B. R. Swistock, 1994. Causes of Episodic Acidifi-cation in Five Pennsylvania Streams on the NorthernAppalachian Plateau. Water Resources Research 30(7):1955-1963.

Driscoll, C. T., N. M. Johnson, G. E. Likens, and M. C. Feller, 1988.Effects of Acidic Deposition on the Chemistry of HeadwaterStreams: A Comparison Between Hubbard Brook, New Hamp-shire, and Jamieson Creek, British Columbia. Water ResourcesResearch 24(2): 195-200.

Edmonds, R. L., T. B. Thomas, and R. D. Blew, 1995. Biogeochem-istry of an Old-growth Forested Watershed, Olympic NationalPark, Washington. Water Resources Bulletin 31(3):409-419.

Foster, N. W., J. A. Nicolson, and P. W. Hazlett, 1989. TemporalVariation in Nitrate and Nutrient Cations in Drainage Watersfrom a Deciduous Forest. Journal of Environmental Quality18:238-244.

Glass, G. and 0. Loucks, 1986. Implications of a Gradient in Acidand Ion Deposition Across the Northern Great Lakes States.Environment Science and Technology 20:35-43.

Gundersen, P., 1991. Nitrogen Deposition and the Forest NitrogenCycle: Role of Denitrification. Forest Ecology and Management44:15-28.

Hedin, L. 0., 1994. Stable Isotopes, Unstable Forest. Nature372:725-726.

Hirsch, R. M., R. B. Alexander, and R. A. Smith, 1991. Selection ofMethods for the Detection and Estimation of Trends in WaterQuality. Water Resources Research 27(5):803-8 13.

Hirsch, R. M., J. R. Slack, and R. A. Smith, 1982. Techniques ofTrend Analysis for Monthly Water Quality Data. WaterResources Research 18:107-12 1.

Huntington, T. G., R. P. Hooper, and B. T. Aulenbach, 1994. Hydro-logic Processes Controlling Sulfate Mobility in a Small ForestedWatershed. Water Resources Research 30(2):283-295.

Jassby, A. D., J. E. Reuter, R. P. Axler, C. R. Goldman, and S. H.Hackley, 1994. Atmospheric Deposition of Nitrogen and Phos-phorus in the Annual Nutrient Load of Lake Tahoe (California-Nevada). Water Resources Research 30(7):2207-2216.

Kaufmann, P. R., A. T. Herlihy, M. E. Mitch, and J. J. Messer, 1991.Stream Chemistry in the Eastern United States 1. Synoptic Sur-vey Design, Acid-base Status, and Regional Patterns. WaterResources Research 27(4):611-627.

Lettenmaier, D. P., E. R. Hooper, C. Wagoner, and K. B. Fans, 1991.Trends in Stream Quality in the Continental United States,1978-1987. Water Resources Research 27(3):327-339.

Lewis, W. M., and M. C. Grant, 1980. Relationships Between SnowCover and Winter Losses of Dissolved Substances from a Moun-tain Watershed. Arctic and Alpine Research 12: 11-17.

Liegel, L., D. Cassell, D. Stevens, P. Shaffer, and R. Church, 1991.Regional Characteristics of Land Use in Northeast and South-ern Blue Ridge Province: Associations With Acid Rain Effects onSurface-water Chemistry. Environmental Management15(2):269-279.

Likens, G. E., 1992. The Ecosystem Approach: Its Use and Abuse.Excellence in Ecology, Book 3. The Ecology Institute, Oldendorf-Luhe, Germany, 167 pp.

Likens, G. E., and F. H. Bormann, 1995. Biogeochemistry of aForested Ecosystem. Springer-Verlag, New York, New York, 159pp.

Lynch, J. A., V. C. Bowersox, and C. Simmons, 1995. PrecipitationChemistry Trends in the United States: 1980-1993. NationalAtmospheric Deposition Program, Colorado State University,Fort Collins, Colorado, 103 pp.

MacDonald, N. W., J. A. Witter, A. J. Burton, K. S. Pregitzer, andD. D. Richter, 1993. Relationships Among Atmospheric Deposi-tion, Throughfall, and Soil Properties in Oak Forest Ecosystems.Canadian Journal of Forest Research 23:2348-2357.

Meiman, J. R., 1987. Influence of Forests on Snowpack Accumula-tion. In: Management of Subalpine Forests: Building on 50Years of Research, C. A. Troendle, M. R. Kaufmann, R. H.Hamre, and R. P. Winokur (Editors). U.S.D.A. Forest Service,Rocky Mountain Forest and Range Experiment Station, FortCollins, Colorado, GTR RM-149, pp. 6 1-67.

Murdoch, P. 5. and J. L. Stoddard, 1992. The Role of Nitrate in theAcidification of Streams in the Catskill Mountains of New York.Water Resources Research 28(10):2707-2720.


Stream Water Chemistry in Watersheds Receiving Different Atmospheric Inputs of H, NH-, NO3-, and S042

NADP, 1991. NADP NTN Annual Data Summary, National Atmo-spheric Deposition Program, Fort Collins, Colorado, 475 pp.

NADP, 1982-1992. NADP NTN Annual Data Summaries, NationalAtmospheric Deposition Program, Colorado State University,Fort Collins, Colorado.

Preston, C. M., V. G. Marshall, and K. McCullough, 1990. Fate of15N-labelled Fertilizer Applied on Snow at Two Forest Sites inBritish Columbia. Can. J. For. Res. 20:1583-1592.

Rascher, C. M., C. T. Driscoll, and N. E. Peters, 1987. Concentrationand Flux of Solutes from Snow and Forest Floor DuringSnowmelt in the West-Central Adirondack Region of New York.Biogeochemistry 3:209-224.

Reichle, D. E., 1973. Analysis of Temperate Forest Ecosystems.Ecol. Studies No. 1, Springer-Verlag, New York, New York, 304pp.

Retzer, J. L., 1962. Soil Survey of Fraser Alpine Area, Colorado.Soil Surv. Serv. 1956, No. 20, USDA Soil Conservation Service,Washington, D.C., 47 pp.

Reuss, J. 0., and D. W. Johnson, 1986. Acid Deposition and theAcidification of Soils and Waters. Ecol. Stud. Ser. Vol 59,Springer Verlag, New York, New York, 119 pp.

Semkin, R. G. and D. S. Jeffries, 1988. Chemistry of AtmosphericDeposition, the Snowpack, and Snowmelt in the Turkey LakesWatershed. Canadian Journal Fisheries and Aquatic Science45(Suppl. 1):38-46.

Sievering, H., D. Burton, and N. Caine, 1992. Atmospheric Loadingof Nitrogen to Alpine Tundra in the Colorado Front Range.Global Biogeochemical Cycles 6(4):339-346.

Stednick, J. D., 1989. Hydrochemical Characterization of Alpineand Alpine-Subalpine Stream Waters, Colorado Rocky Moun-tains, U.S.A. Arctic and Alpine Research 21(3):276-282.

Stoddard, J. L., 1994. Long-Term Changes in Watershed Retentionof Nitrogen: Its Causes and Aquatic Consequences. In: Environ-mental Chemistry of Lakes and Reservoirs, L. A. Baker (Editor).Advances in Chemistry Series No. 237, American Chemical Soci-ety, Washington, D. C., pp. 23-284.

Stottlemyer, R., 1987. Monitoring and Quality Assurance Proce-dures for the Study of Remote Watershed Ecosystems. In: NewApproaches to Monitoring Aquatic Ecosystems, ASTM STP 940,T. P. Boyle (Editor). American Society for Testing and Materials,Philadelphia, Pennsylvania, pp. 189-198.

Stottlemyer, R., 1992. Nitrogen Mineralization and Stream WaterChemistry, Rock Creek Watershed, Denali National Park, Alas-ka, U.S.A. Arctic and Alpine Research 24(4):291-303.

Stottlemyer, R. and D. Hanson, Jr., 1989. Atmospheric Depositionand Ionic Concentrations in Forest Soils of Isle Royale NationalPark, Michigan. Soil Science Society of America Journal53(1):270-274.

Stottlemyer, R. and D. Toczydlowski, 1991. Stream Chemistry andHydrologic Pathways During Snowmelt in a Small WatershedAdjacent Lake Superior. Biogeochemistry 13:177-197.

Stottlemyer, R. and D. Toczydlowski, 1996. Modification ofSnowmelt Chemistry by Forest Floor and Mineral Soil, North-ern Michigan. J. Environ. Qual. 25:828-836.

Stottlemyer, R., B. Travis, and D. Toczydlowski, 1995. NitrogenMineralization in Boreal Forest Stands of Isle Royale, NorthernMichigan. Water, Air, Soil Pollution 82:191-202.

Stottlemyer, R. and C. A. Troendle, 1992. Nutrient ConcentrationPatterns in Streams Draining Alpine and Subalpine Catch-meats, Fraser Experimental Forest, Colorado. Journal ofHydrology 140:179-208.

Stottlemyer, R., C. A. Troendle, and D. Markowitz, 1996. Relation-ship of Elevation and Aspect to Snowpack Loading and Releasein an Alpine-Subalpine Ecosystem. J. Hydrol. (in press).

Troendle, C. A., R. A. Schmidt, and M. H. Martinez, 1993. Parti-tioning the Deposition of Winter Snowfall as a Function ofAspect on Forested Slopes. In: Proc. 1993 Ann. Meeting, West-em Snow Conf., M. Ferrick and T. Pangburn (Editors). QuebecCity, Quebec, pp. 373-380.

Wilkinson, L., 1990. Systat: The System for Statistics. Systat, Inc.,Evanston, Illinois., 676 pp.


stream water chemistry in watersheds receiving different atmospheric inputs of h+, nh4, no3−, and...

Documents