CHANGES IN SOIL SOLUTION CHEMISTRY OF ANDISOLS FOLLOWING INVASION BY BRACKEN FERN

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1 SC/98/ l;o3.00/0 Soil Science Copyrighr ~ by Lippinco[[ Willims &: Wilkim Ocrober 1998 Vol No. 10 Primed 11 U.S.A. CHANGES N SOL SOLUTON CHEMSTRY OF ANDSOLS FOLLOWNG NVASON BY BRACKEN FERN J. L. Johnson.Mynrd,' P. A. McDniel 2, D. E. Ferguson 3, nd A. L. Flen 2 Disturbed res within the Grnd Fir Mosic (GFM) ecosystem of northern dho show little to no nturl conifer regenertion. Cler-cut sites re invded quickly by brcken fern successionl communities nd seem to be in n rrested stte of secondry succession. This study compred the soil solution composition of Andisols supporting brcken fern successionl communities with undisturbed forest to determine the effects of shifts in vegettion communities. Tretment res included undisturbed forest, 3D-yer-old brcken fern glde (cler-cut in 1965), nd nturl brcken fern glde estimted to be centuries old. The nturl brcken fern glde ws divided into subplots, one of which hs heen weeded 2 to 3 times ech growing seson since Soil solution ws collected in porous cermic cup lysimeters t 12- nd 25-cm depths. Smples were collected from My to July in 1994 nd Solutions were nlyzed for ph, Al, nd dissolved orgnic crbon (DOC). The soil solution ph in the 30-yer-old glde ws consistently lower thn in the other sites throughout the smpling period, nd the 3D-yer-old glde ws the only site to periodiclly register below ph 5. The nturl brcken _ fern glde tht hd been weeded ws more similr to the undisturbed forest, suggesting tht brcken fern biomss does hve n cidifying effect on soil solution. The highest Al concentrtion recorded ws 1.6 mg/l in the 3D-yer-old glde, wheres in the undisturbed forest Al ws often below the detection limit. Aluminum nd DOC were found to be positively relted, with r vlues of nd for 1994 nd 1995, respectively. These results indicte tht brcken fern does hve n cidifying effect on soil solution. Aluminum concentrtions were lower thn reported toxic levels for other conifer species nd were correlted with DOC. These two findings suggest tht Al toxicity my not be mjor f«tor contributing to the lck of conifer regenertion within the GFM. (Soil Science 1998;163: ) Key words: Soil solution chemistry, Andisols, brcken fern. T HE ppliction of soil solution chemistry to the study of pedogenic processes is extremely useful becuse of its sensitivity to chnges in vegettion (Nnzyo et. 1993). Person (1971, 1975) proposed tht the composition of soil solution is the most pproprite expression of the soil environment governing plnt response. This dynmic pedologicl pproch (Singer et L 1978) cn Dept. of SOU nd Envronmentdl Science, Univmily 01 C.~fomi, Riv... ide, CA Dr. Johnson-Moynrd is corresponding uthor. E-mil: jrnynrd@ucrcl.u..du 'SOil Science Division, Univ. of dho, Moscow, D 838«2339. 'ljsda Forest Service, nlennountdin Res. Sm., Moscow, D Received Dec. 18, 1997; ccepted June 2, '998. yield informtion not only bout current pedologicl processes but lso bout conditions for plnt growth, such s nutrient vilbility (possible deficiencies nd toxicities). The composition of soil solution reflects chnges in vegettion nd is, therefore, useful in monitoring the effects of mngement techniques nd nturl disturbnces. Chnges in soil solution chemistry hve been documented following disturbnces such s cler-cutting (Dhlgren nd Driscoll 1994), invsion by new vegettion types (Dhlgren et l. 1991), nd vlnches (Arthur nd Fhey 1993). Although chnges in soil solution chemistry re expected fter cler-cutting, the effects re not usully 814 This file ws creted by scnning the printed publiction. Errors identified by the softwre hve been corrected; however, some errors my remin.

2 VOL No. 10 CHANGES N ANDSOL CHEMSTRY AFTER FERN NVASON 815 long-lsting. Dhlgren nd Driscoll (1994) observed tht chemicl responses to whole tree cler-cutting t Hubbrd Brook, New Hmpshire, mximized fter 2 yers nd returned to bckground levels by the fourth nd fifth yers. Some midelevtion ecosystems in the nlnd Pcific Northwest consist of stnds of grnd fir (Abies grndis [Doug!. ex D. Don] Lindl.) forest in ptchwork or mosic pttern with vrious shrub nd forb communities. These ecosystems re referred to collectively s the Grnd Fir Mosic (GFM) (Ferguson nd Adms 1994). n the GFM of northern dho, successionl communities dominted by brcken fern (Pteridiurn quilinurn (L.) Kuhn) re estblished quickly fter timber hrvest or nturl disturbnce such s fire or disese. These res seem to remin in n rrested stte of secondry succession, i.e., little or no nturl conifer regenertion is observed where brcken fern-dominted successionl communities hve become estblished (Ferguson 1991; Sommer 1991). Mny cler-cut sites within the GFM hve continued to support brcken fern successionl communities since timber hrvest ws initited in the 1960s, period of more thn 30 yers. Attempts to reestblish these sites by plnting seedlings hve met with very limited success (Ferguson nd Adms 1994). Recent investigtions of the solid-phse chemistry nd minerlogy of GFM soils hve shown tht minerlogicl shift, from llophnic to nonllophnic Andisols, is occurring in soils supporting brcken fern communities (Johnson Mynrd et l. 1997). Although nonllophnic Andisols re often ssocited with luminum (Al) toxicity in plnts (Shoji et l. 1985; Nnzyo et ), solid-phse studies do not necessrily give complete picture of the soil environment experienced by plnt roots. The objective of this study ws to determine if there re significnt chnges in the soil solution chemistry of site tht is invded by brcken fern, compred with djcent undisturbed forest, s well s to provide preliminry evlution of the possibility of toxic levels of Al inhibiting nturl conifer regenertion. MATERALS AND METHODS Study Are The GFM occurs in the to 1800-m elevtionl rnge of the Clerwter River dringe of northern dho nd in the Blue Mountins of northestern Oregon nd southestern Wshington (Fig. 1). The study re is locted t n elevtion of 1463 m, pproximtely 3 km south ofegle Point in the Clerwter Ntionl Forest, Sec. 35, T40N; R7E. Dominnt soil prent mterils in the study re include Mzm volcnic sh, which verges bout 60 cm in thickness, nd underlying colluvium nd/or residuum derived from fme-grined igneous rock tht is chemiclly similr to grnite. Smpling loctions were chosen to llow comprison of soils under three different vegettion types or tretments. The tretments included undisturbed forest, 30- yer-old brcken fern glde (cler-cut nd invded by brcken fern in 1965), nd nturl brcken fern site (present in the GFM before timber hrvest) tht is estimted to be centuries old. The nturl brcken fern glde is divided into subplots, one of which hs been weeded 2-3 times during ech growing seson since Sites re djcent to one nother nd hve similr slope, spect, nd prent mteril; vegettion type is the only fctor tht differs significntly. Although the effects of site nd vegettion re confounded somewht s result of the lck of repliction of sites, it is resonble to conclude tht vegettion type is cusing differences in soil solution becuse of the creful selection of sites. Differences in vegettion type re reflected within the clssifiction of soils within the GFM. Soils in the undisturbed forest re clssified s Typic Hpludnds (Soil Survey Stff 1994;Johnson-Mynrd et l. 1997). The 30-yer-old brcken fern glde soils re clssified s Alic Fulvudnds; the Fulvi-gret group indictes higher C content in the upper 40 cm of the soil compred with the Hpludnds of the undisturbed forest (Soil Survey Stff 1994). Soils of the nturl brcken fern site re clssified s Alic Hpludnds, bsed on KC-extrctble Al > 2 cmol(+)/kg (Soil Survey Stff 1994; Johnson Mynrd et l. 1997). To monitor soil solution chemistry, three sets of two porous cup suction lysimeters (5-emdirn.) were plced t ech site. Ech set consisted of 30.5-cm-ong lysimeter nd 15-cm-ong lysimeter buried to depths of 25 em nd 12 em, respectively. To help minimize Al contmintion of cid soil solution by the porcelin cups (Rsmussen 1989), lysimeters were leched with deionized wter in the lbortory before instlltion nd were then llowed to equilibrte in the field for n 8-month period before smple collection. The smplers used in this study were of different type thn the ones used in Rsmussen's study nd hve been reported s being pproprite for smpling cidic soil solutions when properly pretreted nd equilibrted in the field

3 816 JOHNSON-MAYNARD, McDANEL, FERGUSON, AND FALEN SOL SCENCE CANADA WASHNGTON f-48 MONTANA, '\ 1 Spokne t + f-47 ~v... " ~ork Cler"'~te + " -- ~:to - -"'- R.i Ver 0. '""" " L ~ :t>it-v \... Q~ j~ '.. Egle Pt. Moscow "'v./~ ~. T40N... ~ ~ --.~... '!-.'f f ~~ --, ~ Sheep Mtn. Study ~Site ~o.. o ) ~ Sec ~~, DAHO R7E OREGON, r 1 Fig. 1. Loction of the study re in northern dho; inset shows loction of the smpling site. (Hughes nd Reynolds 1990). Soil solution smpling in 1994 nd 1995 ws strted in My, fter snowmelt, nd continued through July when the soils becme too dry to obtin dequte smple. Solutions were extrcted from the soil by plcing vcuum of pproximtely 0.7 MP on the lysimeters for bout 3 h. Solutions were then collected in plstic flsk, plced in cooler, nd trnsported bck to the lbortory. Lbortory Methods After filtering through 0.45-J.Lm flter, smples were immeditely nlyzed for ph. Auminum nd Fe concentrtions of soil solution were mesured by CP spectroscopy. Dissolved orgnic crbon (DOC) ws mesured using Dohrmnn C nlyzer. Only soil solutions from the deep (25 em) lysimeters were nlyzed for DOC becuse they yielded greter mounts of smple throughout the seson. Dt were nlyzed by the generl liner. model procedure of SAS (SAS Corp. 1987). Anlysis of vrince w~ used to test the null hypothesis tht men vlues for ph, DOC, nd concentrtions of A nd Fe in soil solution were not different between vegettion types. Signifcnt differences were determined by protected lest significnt difference test t P = For A, Fe, nd ph, no significnt differences between the shllow (12 em) nd deep (25 em) lysimeters were found within sites; therefore, dt from these lysimeters were grouped to compute verges. As result, A, Fe, nd ph vlues represent verge conditions found in the 12 to 25-cm depth within the sh cp. RESULTS AND DSCUSSON ph 1994 ph dt showed tht soil solution from the 30-yer-old brcken fern glde site hd consistently lower ph vlues throughout the growing seson (Fig. 2) nd ws the only site in which ph dropped to 5 (July 1) during the smpling period. n cid soil solutions, ph 5 is criticl

4 VOL No. 10 CHANGES N ANDSOL CHEMSTRY AFTER FERN NVASON ~ , (A) (B) c.-e... - s:. b d... ~- 6.5 c..- _... ~... ~.... ~,/ b --- b l b...,/ c. ::: lit b..- ~ b b..... b ph...,.---lr / / b.. / b / / li ~ r-----r-----r-----r~--~----r-----r---~r---~--~ My 20 Jun 3 Jun 17 Jull Jul15 My 22 Jun 10 Jun 26 JuliO Jul24 Smpling Dte yr-old brncken site - +- Undisturbed forest... Nturl brncken glde (weeded) Nturl brncken fern glde Fig. 2. Soil solution ph for smpling dtes in (A) 1994 nd (B) Dt points lbeled with the sme letters within smpling dte re not significntly different (X = 0.05). point t which plnts my strt to experience Al toxicity (Wlt 1994), Sttisticl nlysis shows tht ph within the 30-yer-old nd nturl brcken fern gldes ws significntly lower thn in the undisturbed forest nd the nturl brcken fern glde (weeded) for every smpling dte in The fct tht the soil solution ph from the. weeded nturl brcken fern glde ws not significndy different (in four of five smpling dtes) from tht of the undisturbed forest suggests tht the removl of the bove-ground brcken fern biomss does help rise ph reltive to the unweeded brcken fern site.. Soil solution dt collected in 1995 re similr to those of 1994 in tht the ph of soil solution in the 30-yer-old brcken fern glde ws usully lower thn the other sites throughout the smpling period (Fig. 2b). The lowest ph recorded ws 4.8 in the 30-yer-old glde on June 26, As ws observed in the 1994 dt, the 30-yer-old brcken fern glde hd the only solution dropping below 5.0 during the entire smpling period. The trend in ph with respect tq time is similr to 1994 dt in the undisturbed forest. The 30-yer-old brcken fern glde ws the only site to show decrese in ph correspondlng to the June 26, 1995, smpling. This site lso showed sesonl decrese in ph for June Combining the 2 yers of dt suggests tht the soil solution from brcken fern-influenced soil does experience sesonl drop in ph. Soil solution ph in the weeded subplot of the nturl brcken fern glde ws consistently, significntly higher thn in the unweeded subplot, indicting tht brcken fern biomss hs n cidifying effect on soil solution. Overll ph dt point to two importnt findings. First, soil solution ph of the 30- yer-old brcken fern glde is consistently nd significndy lower thn tht of the undisturbed forest nd the nturl brcken fern glde (weeded). The 30-yer-old brcken fern site is lso the only site tht experienced soil solution ph vlues less thn 5 during the 2-yer smpling period. Secondly, the ph in the weeded subplot of the nturl brcken fern glde ws significntly higher thn the unweeded subplot for every smpling dte over the 2-yer period. This indictes tht bove-ground brcken fern biomss hs n cidifying effect on soil 'solution ph. Chnges in soil ph were lso noted in the solid phse of soils supporting'brcken fern communities for s little s 30 yers, The ph of 1:1

5 818 JOHNSON-MAYNARD, MCDANEL, FERGUSON, AND FALEN SOL SCENCE (soil:wter) mixtures from soils of the 30-yerold nd nturl brcken fern sites were sigpificnty lower thn the undisturbed forest (Johnson-Mynrd et l. 1997). Aluminum n 1994, soil solution A concentrtions, s expected, vried inversely with ph; i.e., the highest A concentrtion 'corresponded to the lowest ph (Fig. 3). The 30-yer-old brcken fern glde ws, therefore, highest in A, wheres the undisturbed forest ws often below the lower limit of the detection level (0.15 mg/l). Sttisticl differences were detected in three of the five smpling dtes during The undisturbed forest ws significntly lower in Al thn the 30-yer-old brcken fern glde onjune 3 nd 17 ndjuly 1; Although Al concentrtions in soil solutions collected in 1995 were more vrible, they showed the sme generl trend of the 30:..yerold brcken fern glde, i.e., they were highest wheres the undisturbed forest ws lowest (Fig. 3b). Soil solution from the 30-yer-old glde ws significntly higher in A for every smpling dte in Aluminum concentrtions were lso much higher in 1995 reltive to The reson for this difference is not entirely cler, but it my be relted to climtic differences. Approximtely 3.3 em more rin fell during the months of J0y nd June in 1994 thn fell in My nd June 1995, resulting in dilution of the A in soil solution. The effectiveness of weeding the nturl glde is somewht less cler when looking 't 1995 dt. This problem reflects the need for further monitoring to void skewed dt cused by climtic conditions. Solution culture studies hve been conducted to determine the effects of Al on tree growth. Unfortuntely, none of these studies hs considered grnd fir. Hutchinson et l. (1986) found reduced biomss of spruces grown in nutrient solution contining from 0.19 to 0.37 mmol Al/L (5.1 to 10 mg/l) nd in vrious pines with 1.48 to 2.96 mmol Al/L (40 to 80 mg/l). t is importnt to consider tht these numbers represent totl Al in solution nd tht the toxic portion would be much smller. Thornton et l. (1987), for exmple, reported the toxic threshold for root elongtion of red spruce (Pice rubens Srg.) seedlings s 0.25 mmol Al/L (6.75 mg/l), with n estimted A+3 ctivity of 0.05 mmol Al/L (1.35 mg/l). Aluminum concentrtions mesured in this study re generlly below the toxic levels reported for other species. This indictes 1.6~ ~-----~~~ ' (A) A 0.8 (mgl) 0.4 ~- _..J! _- /. / / "'~'''...!,.., t' ~... "". b b 8 F" _... b..- _ "'..."... b b...,. '. 7".:t:"::... Jl.._ b " b...- "b _:. 'i-- b..- _ 4 _.l>~ - ~ - J>. O~~----_T-----r----~----~~--~----~----r_----~--~r_~ My 20 JUD 3 JUD 17 Jull Jul15 My 22 Jun 10 Jun 26 JulO Jul24 Smpling Dte yr-old brcken fem site -..- Undisturbed forest.-.-e... Nturl brcken fem site (weeded) Nturl brcken fern site Fig. 3. Soli solution A concentrtions for (A) 1994 nd (B) Dt points lbeled with the sme letters within smpling dte re not significntly different ( = 0.05).

6 VOL No. 10 CHANGES N ANDSOL CHEMSTRY AFTER FERN NVASON 819 tht Al toxicity my not be mjor contributor to the regenertion problem within the GFM. Despite the significntly higher levels of Al in the soil solution from brcken fern-influenced soils, the occurrence of Al toxicity cnnot be proven for two resons. First, Al threshold vlues hve not been reported for grnd fir. Second, most of the studies report toxic levels of totl Al in solution insted of Al ctivities. Dissolved Orgnic Crbon Dissolved orgnic crbon is n importnt component of soil solution. These soluble substnces cn exert substntil influence on ion leching processes, nutrient cycling, microbil community dynmics, nd minerl wethering (Evns et l. 1988). n this study, interctions between Al nd DOC re extremely importnt becuse of differences in biovilbility of orgniclly complexed Al nd free Al+.} (Hue et l. 1986). n 1994, dissolved orgnic crbon t 25 cm ws highest in the 30-yer-old brcken fern glde soil solution for every smpling dte except June 17 (Fig. 4). Dissolved orgnic crbon in the 30-yer-old brcken fern glde ws lso significntly higher thn in the undisturbed forest on My 20 nd July 15. A generl trend existed where DOC ws highest in erly spring (My 20), decresed throughout June, nd then incresed to the mximum level in July. July ws lso when the soil becme too dry to yield sufficient soil solution smple for nlysis. t ws expected tht DOC would be higher in spring becuse of the flush of orgnic cids relesed from decomposition of the plnt biomss. n 1995, DOC levels were significntly higher in the 3D-yer-old brcken fern glde reltive to the undisturbed forest for every smpling period (Fig. 4b). DOC in the nturl brcken fern glde ws signilicntly higher thn in the undisturbed forest for every smpling period nd significntly lower thn in the 30-yer-old brcken fern glde for ll but one smpling dte. There is no pprent trend of DOC concentrtion with time mong sites in 1995 dt. Soil orgnic crbon contents indicte tht DOC is being immobilized rpidly within the shcp of the brcken fern influenced soils. Orgnic crbon rnged from 5.4% in the 30- yer-old soil to 3.7 in the undisturbed forest (Johnson-Mynrd et l.1997). Temporl vrition in DOC is fctor tht influences the A chemistry of soil solutions gretly (Nilsson nd Bergkvist 1983). Dissolved orgnic crbon nda/fe in soil solution smples collected t sites within the GFM during the 1994 (dt not shown) nd 1995 growing sesons re significntly nd positively correlted, with r vlues of nd 0.824, respectively (Figs. S 60~ , ~ (A) 1994 (B) DOC (mgl) ~ b~ ~~... \ \ '" //.1'''' b \ ~...,b. /".' b '.:- \ / /'/" ~ - -.:... ~... ~.. b... b b /r , b / c c ' b b ::":;.:.--e"~ c c -~ c b c 10~~----~----~----~----~r-~~----~r-----r-----r-----r-~ My 20 Jun 3 Jun 17 Jull JullS My 22 Jun 10 Jun 26 JuliO Ju24 Smpling Dte yr-old brcken fern site - +- Undisturbed forest.-..._-- Nturl brcken fern site (weeded) Nturl brcken fern site Fig. 4. Dissolved orgnic crbon (DOC) concentrtions in soil solutions collected in (A) 1994 nd (8) Dt points lbeled with the sme letters within smpling dte re not significntly different (. = 0.05).

7 820 JOHNSON-MAYNARD, MCDANEL, FERG;-;SON, AND FALEN SOL SCENCE (A) [= (B) [ = cf o 0 0!lJ A 6DD Fe 0.40 lj (mgl) (mg/l) SO SO DOC (mg/l) Fig. 5. Reltionship between (A) A nd (B) Fe with DOC (t 25-cm depth) in soil solution smples from nd b). Solid phse dt showing ccumultions of All fe-humus complexes in the Bw1 nd Bw2 horizons of the 30-yer-old nd nturl brcken fern gldes (Johnson-Mynrd et l. 1997) suggest tht the intimte reltionship between All Fe nd DOC my be ltering the blnce of soilforming processes. The reltionship between DOC nd Al shown in Fig. 5 cnnot, by itself, be used to determine the possibility of Al toxicity. Nonllophnic Andisols hve lrge orgnic pool tht controls Al vilbility, sitution in which one would expect to see decresed Al toxicity, yet Al toxicity is commonly reported in nonllophnic Andisols. Further dt bout Al specition in soil solution re needed to evlute the possibility tht Al toxicity prevents nturl conifer regenertion in soils of the GFM. CONCLUSONS Soil solution ph ws significntly lower in the 30-yer-old brcken fern glde. This ws cused by the presence of brcken fern nd the resulting lck of secondry succession. The ph of soil solution smples from brcken fern-influenced soils showed sesonl decrese, nd occsionlly it reched vlue of 5. Soil ph dt indicte tht the presence of brcken fern biomss cn decrese ph significntly within reltively short time spn. Aluminum in soil solution ws lso significntly higher within the volcnic sh cp of the 30-yer-old nd nturl brcken fern gl~es for most of the smpling dte~. Although toxic level of Al hs not been reported for grnd fir, the concentrtions mesured in the GFM re generlly lower thn vlues reported for other species. This indictes tht Al toxicity is not responsible for the lck of nturl conifer regenertion. Dissolved orgnic crbon lso tends to be highest in the brcken fern-influenced soils nd is correlted positively with totl Al nd Fe in soil solution. The reltionship between DOC nd Al/Fe is consistent with minerlogicl dt nd indictes tht formtion of soluble metl-humus complexes is n importnt process in Andisols supporting brcken fern communities. REFERENCES Arthur, M.A, nd T.]. Fhey Controls on soil solution chemistry in sublpine forest in north-centrl Colordo. Soil Sci. Soc. Am.]. 57: Dhlgren, R. A, F. C. Ugolini, S. Shoji, T. to, nd R. S. Sletten Soil-forming processes in Alic Melnudnds under Jpnese pmps grss nd ok. Soil Sci. Soc. Am.]. 55: Dhlgren, R.A nd C. T. Driscoll The effects of whole-tree der-cutting on soil processes t the Hubbrd Brook Experimentl Forest, New Hmpshire, USA Plnt Soil. 158: Evns,A]r., L. W. Zelzny, nd C. E. Zipper Solution prmeters influencing dissolved orgnic crbon levels in three forest soils. Soil Sci. Soc. Am. ]. 52: Ferguson, D. E nvestigtions on the Grnd Fir Mosic ecosystem of northern dho. Ph.D. disserttion, University ofdho, Moscow, D. Ferguson, D. E., nd D. L. Adms Effects of pocket gophers, brcken fern, nd western coneflower on survivl nd growth of plnted conifers. Northwest Sci. 68:

8 VOL. 163 ~ No. 10 CHANGES N ANDSOL CHEMSTRY AFTER FERN NVASON 821 Hue, N. v., G. R. Crddock, nd EAdms Effect or orgnic cids on luminum toxicity in subsoils. Soil Sci. Soc. Am.]. 50: Hughes,S., nd B. Reynolds Evlution of porous cermic cups for monitoring soil-wter luminum in cid soils: Comment on pper by Rulund-Rsmussen (1989}.J Soil Science 41: Hutchinson, T. c., L. Bozic, nd G. Munoz-Veg Responses of five species of conifer seedlings to luminum stress. Wter Air Soil Pollut. 31: Johnson-Mynrd,]. L., P. A. McDniel, D. E. Ferguson, nd A. L. Flen Chemicl nd minerlogicl conversion of Andisols following invsion by brcken fern. Soil Sci. Soc. Am.]. 61: Nnzyo, M., R. A. Dhlgren, nd S. Shoji. Chemicl chrcteristics of volcnic sh soils. n Volcnic Ash Soils-Genesis, Properties, nd Utiliztion. S. Shoji et l. (eds.). Elsevier,Amsterdm, pp Nilsson, S.., nd B. Bergk.vist A chemistry nd cidifiction processes in shllow podzol on the Swedish west cost. Wter Air Soil Pollut. 20: Person, R. W ntro to symposium-the soil solution. Soil Sci. Soc. Am. Proc. 35: Person, R. W Soil cidity nd liming in.the humid ttopics. Cornell 1m. Agric. Bull. No. 30, thc., NY. Rsmussen, R. K Aluminum contmintion nd other chnges of cid soil solution isolted by mens of porcelin suction cups. ]. Soil Sci. 40:95-10l. SAS Corp SAS User's Guide: Sttistics. SAS nst., Cry, NC..,. Shoji,S., T. to, M. Sigus, nd 1. Ymd Properties of nonllophnic Andisols from Jpn. Soil Sci. 140: Singer, M., F. C. Ugolini, nd J. Zchr n siru srudy of podzoliztion on tephr nd bedrock. Soil Sci. Soc. Am.]. 42: Soil Survey Stff Keys to Soil Txonomy, 6th Ed. SMSS technicl monogrph no. 19. US Gov. Print. Office, Wshington, DC. Sommer, M. R Soils of the Grnd Fir Mosic. M.S. thesis, University of dho, Moscow, ill. Thornton, F. c., M. Schedle, nd D.J. Rynl Effects of luminum on red spruce seedlings in solution culture. Environ. Exp. Bot. 27: Wolt,]. D Soil Solution Chemistry: Applictions to Environmentl Science nd Agriculture. John Wiley & Sons, New York.