Leaf element concentrations and soil properties
in first- and second-rotation stands of red alder
Jana E. Compton, Dale W. Cole, and Peter S. Homann
Abstract: Successive rotations of nitrogen-fixing red alder (Alnus rubra Bong.) may alter soil properties, potentiallyinfluencing future tree growth and nutrition. We examined the effects of red alder on soil properties and next-rotation alder
leaf and leaf litter element concentrations. A conversion experiment was initiated in 1984 by clearcutting a 50-year-old red
alder stand and an adjacent 50-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand. Both areas were replanted
with red alder, yielding first- and second-rotation alder plots. Prior to conversion, the 50-year-old alder plot had higher total
soil C, N, and extractable Ca, Mg, and Al, while pH and available P were lower. The second-rotation plot had lower leaf P,
Ca, and Mg concentrations than the first-rotation plot in 1988 and 1989; it also had lower leaf K, Mn, and Fe concentrations in
1989. The second-rotation plot had lower leaf litter N, P, K, Mg, and Fe concentrations, and litter-fall mass and element
transfer rates were 3049% those of the first rotation. The findings indicate a potential decrease in availability of most
macronutrients when growing repeated rotations of red alder on glacial till derived soils.
Rsum: Les rvolutions successives daulne rouge (Alnus rubra Bong.), une espce fixatrice dazote, peuvent modifier lesproprits du sol et influencer la nutrition et la croissance future des arbres. Les auteurs ont examin les effets de laulne rouge
sur les proprits du sol et la concentration des lments dans les feuilles et la litire de feuilles des aulnes de la rvolution
subsquente. Une exprience de conversion a t initie en 1984 par la coupe blanc dun peuplement daulne rouge de
50 ans et dun peuplement adjacent de Douglas taxifoli (Pseudotsuga menziesii (Mirb.) Franco) de 50 ans. Les deux endroits
furent replants avec de laulne rouge pour constituer des parcelles de premire et de seconde rvolution. Avant la conversion,
la parcelle qui contenait de laulne rouge de 50 ans avait des valeurs de C et N total et de Ca, Mg et Al extractibles plus
leves tandis que les valeurs du pH et de P disponible taient plus faibles. Les parcelles de seconde rvolution avaient des
concentrations foliaires de P, Ca et Mg plus faibles que les parcelles de premire rvolution en 1988 et 1989. En 1989, les
concentrations de K, Mn et Fe taient galement plus faibles. Les parcelles de seconde rvolution avaient des concentrations
de N, P, K, Mg et Fe dans la litire de feuilles plus faibles ainsi quune masse de chute de litire et des taux de transfert des
lments qui reprsentaient 3049% des valeurs observes dans le cas de la premire rvolution. Ces rsultats montrent quil
peut y avoir une diminution de la disponibilit de la plupart des macronutriments aprs plusieurs rvolutions daulne rouge sur
des sols drivs dun till glaciaire.
[Traduit par la Rdaction]
Early successional nitrogen-fixing alder species strongly mod-ify soil properties during primary succession, increasing soilorganic matter, nitrogen, and mineral weathering (Bormannet al. 1994). However, continued N inputs by N fixers duringsecondary succession can result in accelerated nitrate leaching(Van Miegroet and Cole 1984), with rates ranging from 3 to40 kg NO3-Nha1year1 in mixed and pure red alder (Alnusrubra Bong.) stands (Binkley et al. 1992; Johnson andLindberg 1992). Reaching this N-saturated condition may not
be commonly observed because N fixers often do not naturallyreplace themselves or grow in continuous stands. Coppicing orplanting successive rotations of N fixers may substantially in-crease soil acidity and is considered to be risky in acid soils forthis reason (Bormann et al. 1994). Although interplanting withN fixers may increase N availability and biomass accumula-tion of nonfixing species in mixed stands (Ct and Camir1987), the complex effects of rotations on soil fertility are notwell understood.
Where red alder invades after disturbance, soil N availabil-ity often increases, and pH and base saturation decrease (sum-marized by Bormann et al. 1994). Decreases in soil pH aregenerally accompanied by increased soil solution and ex-tractable Al3+ (Reuss and Johnson 1986) and could result indecreased soil P availability (Sanyal and De Datta 1991).Available P has been shown to be higher (Giardina et al. 1995)and lower (Cole et al. 1990) under alder; given the importanceof pH and available P in the growth, nodulation and fixationin symbiotic N-fixing plants (Sprent 1988), any change overthe course of succession could be important in their ecologyand management.
Previous study in the Cedar River watershed of westernWashington found that red alder was less productive when
Received June 6, 1996. Accepted January 2, 1997.
J.E. Compton1 and D.W. Cole.College of Forest Resources,University of Washington, Seattle, WA 98195, U.S.A.P.S. Homann.Center for Environmental Science, MS 9181,Huxley College, Western Washington University, Bellingham,WA 98225-9181, U.S.A.
1 Author to whom all correspondence should be addressed.Present address: Department of Natural Resources Science,University of Rhode Island, Woodward Hall, Kingston, RI02881, U.S.A.
Can. J. For. Res. 27: 662666 (1997)
1997 NRC Canada
. J. F
grown in repeated rotations, as compared with growth on anadjacent site previously occupied by 50-year-old Douglas-fir(Pseudotsuga menziesii (Mirb.) Franco). The second-rotationalder had 33% less height growth and 75% less abovegroundbiomass 5 years after planting (Cole et al. 1995). The objectiveof this study was to examine the relationship between potentialchanges in soil properties under red alder and subsequent aldernutrition at this site. We expected the initial lower soil pH, basesaturation, and available P in the alder soil to yield lower basecation and P concentrations in the leaves and leaf litter of thesecond-rotation alder stand than in alder grown on a formerDouglas-fir site.
Site descriptionThe study was conducted at the Thompson Research Center, locatedat the southwestern end of the Cedar River watershed, 56 km south-east of Seattle, Wash. The elevation is 220 m in the western foothillsof the Cascade Mountains. Mean annual air temperature was 10Cfrom 1987 to 1992; the January mean was 4C; and the July mean was17C. Average annual precipitation was 135 cm, a large proportion ofwhich fell as rain between October and March.
The soil underlying the study site is the Alderwood series, pre-viously classified as a dystric Entic Durochrept, recently reclassifiedas a mesic ortstein Aquic Haplorthod (USDA Soil Survey Staff 1986).It is a gravelly sandy loam, derived from ablation till overlying indu-rated basal till. The earliest documented forest, mature Douglas-fir,was logged between 1910 and 1920 (Turner et al. 1976). After a seriesof wildfires passed through the area, most of the site was planted withDouglas-fir in 1931. Areas not planted, or where Douglas-fir wasdestroyed by subsequent fire, were invaded by red alder over the next10 years.
At the initiation of this study, the adjacent stands of Douglas-fir(basal area 50 m2ha1) and red alder (36 m2ha1) were approximately50 years old (Van Miegroet et al. 1992). In September 1984, all treesin a 50 100 m (0.5-ha) plot within each of the two stands wereharvested and removed with cables to minimize soil disturbance. InFebruary 1985, 2-year-old red alder seedlings from gravelly areas10 km southeast of the site were planted at 2 2.5 m spacing, yieldingfirst-rotation alder on the former Douglas-fir plot and second-rotationalder on the former alder plot.
Soil sampling and analysisIn July 1984, prior to harvesting, mineral soil was collected from the015, 1530, and 3045 cm depths from eight 15 15 m subplots ineach plot. For each subplot, soil was composited from three pits andair-dried. The