FIELD STUDIES OF PINE, SPRUCE AND ASPEN PERIODICALLY SUBJECTED TO SULFUR GAS EMISSIONS A. H. LEGGE, Environmental Sciences Centre (Kananaskis), The University of Calgary, Alberta; R. G. AMUNDSON, Department of Botany, University of WAshington, Seattle; D. R. JAQUES, Environmental Sciences Centre (Kananaskis), The University of Calgary, Alberta; and R. B. WALKER, Department of Botany, University of Washington, Seattle. ABSTRACT Field studies of photosynthesis in Pinus contorta/Pinus banksiana (lodgpole pine/jack pine) hybrids, Picea glauca (white spruce) and Populus tremuloides (aspen) subjected to SO2 and H2S from a nearby natural gas processing plant were initiated near Whitecourt, Alberta, Canada during the summer of 1974. The site was characterized as a Pinus- Picea glauca/Arctostaphylos uva-ursi association (pine-white sprucee/bearberry). A 15 meter high scaffold was used as access to mid-crown foliage in the pines while the spruce and aspen were accessible from the ground. Net assimilation rates, transpiration rates and leaf resistances were calculated and water deficits were monitored. Photosynthetic rates measured were in a low range for the conifers studied, with pine having a maximum of 3.28 mg dm-2 hr'l and white spruce a maximum value of 2.3 mg dm-2 hr-l. The low maximum photosynthetic rate determined for aspen is thought to be attributable to the onset of autumn. Chemical analyses for SO4-sulfur using the methylene blue colorimetric method of Johnson and Nishita (1952) showed levels of 300-700 ppm, with the older foliage showing slightly higher values. Visible chronic SO2 symptoms had a pronounced sun, or upward, orientation. Ambient SO2, H2S and total S were measured using 2 Tracor 270HA Atmospheric Sulfur Analyzer (chromato- graphic method) and trends in ambient SO2 concentrations using an Envirometrics SO2 Analyzer (polarographic method). Concentration was found to be variable for SO2 and generally below 0.05 ppm. A concentration gradient of SO2 was found to exist in the lodgepole pine/jack pine stand with the SO2 values above the canopy generally higher than below the canopy (0.1 ppm above and 0.05 ppm below). This condition was occasionally reversed. The plant canopy is considered to act as a barrier to downward diffusion of the sulfur emissions in the first case and also a barrier to upward diffusion of sulfur emissions present due to advection in the stand in the second case. The vegetative environment surrounding the Windfall Gas Plant is definitely affected by sulfur gas emissions but the extent remains to' be determined. INTRODUCTION Specific damage and even elimination of plant species from areas exposed to sulfur gas emissions such as SO2 have often been documented (Scheffer and Hedgecock, 1955; Bowen, 1965; Westman, 1974; Skorepa and Vitt, 1975). Air quality sampling trailers are used extensively today to monitor air pollutants. It is difficult if not impossible, however, to estimate "damage" or impact from air pollu- tants upon vegetation without a knowledge of the many environmental variables, in addition to pollutant dose, that can modify plant response. An extensive research effort is needed to determine the short term and long term effects of high and low concentrations of sulfur gas emissions on vegetation in the field. The main objective of this study was to begin answering specific questions about the effects of sulfur gas emissions on several dominant plant species periodically exposed to a point source in the field: (1) What is the nature of the plant communities surrounding the point source emission? (2) What is the ecophysiological status of several dominant plant species Pinus contorta/Pinus banksiana (lodgepole pine/ jack pine) , Picea glauca (white spruce) and Populus tremuloides (aspen) under "as it is" field conditions? (3) What is the nature and composition of the ambient atmosphere in terms of SO2 and H2S using the methods of gas chromatography and polarography? The experimental site is located approximately one-half mile east of the AMOCO Windfall Gas Plant in the Whitecourt area of the sour gas corridor of western Alberta and is shown in plate 1 and plate 2. This area was chosen for study for several important reasons: (1) presence on the vegetation of classic symptoms indicating stress from sulfur gas emissions; (2) extensive background data already available for the area; Plate 1.. False col.or i.nfrrtrcc1 aerial. photoyraph r;howi.ng spzttl.al relationshi.]? between experimental. eco~>l~ysi.o:loyi.cal.test site on srtnci ciur'tt? (A) and the AMOCO Wi.nclfa1l. Gas Pl.ant: (If). The study area i.s cast of the gas plant. The affcci:~of the 1.956 fire are rcac1i.l.y i.cicnti.finblc hy the patchwork nature of the vegetation. Scale : 1: 30,000 Irnagery supp.2j.cd by :ENTRIM 15nvironmental Consultants YJtd . (3) si.rnil.arity in plant speci.es composi.ti.sn between this site and similar areas in the region of the Athabasca Tar Sands, thus making the data generated transferrahlc; (4) availability of line power; and (5) cxcal.lenk c:oopcratior~with the yi16 processing industry via tho Whitecourt: Environmental. Sturly Group ~nernber con~panies. Sincc the study area is located near the Windfal1 Gas Plant, it must bc rementbered that the primary point sources were the flare stacks rather that1 the incinerator st:acks. Plate 2. Aerial. col.or oblic~ueshowing rel.ationship between experjmental ecophysioJogical test site (A), instruinent trailer, iS rncter access tower to mid- crown foliage of lodyepole pine/-jack pine hybrids in the foregrounci nncl t-.he AMOCO W.i.nclfal.l. Gas I?lant (13) in the background and to the west. The recl ancl white striped incinerator stacks are indi.cated by (1) and the fl.are stacks by (2) . Note the undulati.ng nature of the topography. SI'I'X.: Cl,ASSSlt"ECATION AND DESCIIIP'I'ION The vccjetation of the Pihitccourt, Albcrta area J !; incl.uclec1 i-n thc "predort\inantl.y f orest " subrec~ionof the S3orcal Yorest ltecji.on of Canada by 1Iall.iclay (1937) . 17or.re (3.972) has further stzhclivjdcd the noreal Forest Region into 45 distinct yeoqraphic arcas with the PJhj tecourt arca located in the Lower Foothills area (R.l.9a). This area is char- acterized as a transition Forest area bei,weon the Boreal and the Subalpine Forest lieqions . The transitional. nature of the vcgetati on is emnphasized by the fact that, two cornmon species of trees occurring in the arca are actually represented by populations OF hybri.cl individual s bctween XJinus cont.ort:~iand Pinus hanksinnci vrhi Lc the true fir in the arca represents hybrids between nbics lasiocarpa and Abjrs ba2snmen. Variabi.lity in natural plant comnluni.C:ics i.n the Wh2.tecour.t: area in the vicinity of thc Windfall Gas Plant is naturally cor~lplex,but this complexity has been intensified due to past disturbance of the area by fire in 1.956 and by sei.smic expl.orati.on. The sutxiucci utldulatirrg topography also contri.butcs to gradual. environrncnta3. gradients causi.ng subtle variation in community cornposition and struct:ure front locat:i.on to location (plate 2). Two c1ist:inct sites offer fairly urxi.forrn and repeatable hahi.tats for vegetative community clcvelopntent. These arc well-drained vegctatecl sand dune sites and moist bogs. Thesc two sites exhibit plant communities that arc remarkably uniform and repeat themselves consistent1.y across the 1.anclscape. Only the sand dune site, one-half mi1.e cast of t:hc AMOCO Windfal.1. Gas X31.ant, wj.3.1 be ciescri.bed in cletail since it was the location of the ccopl.tysiol.ogicaI i111iiI.ysis durirlg the late sllinnlcr of 197.1 (plate 3). I?l.a%e 3. Experimental test siC:e one-half n1il.e east of the AMOCO Windfall Gas Plant showing the mature stand of Pinus contori:a/P.inus bn~?ks.innahybrid:; with 1.5 nteter access tower scaf foldi.ng and inc;trunlent trailer. Note the open nature of the stand and the domi.nancc of the pine. The plant association occurring on this sand dune site has been characterized following standard phytosociotogical techniyues (Daubenmire, $968). Table l shows the overstory ancl understory in this single-layercd, even-aged stand. 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