Soil Nutrient Regimes Research Articles

Light-growth responses of coastal Douglas-fir and western redcedar saplings under different regimes of soil moisture and nutrients

We characterized the radial and height growth response to light for coastal Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) and western redcedar (Thuja plicata Donn ex D. Don) saplings growing in sites of different regimes of soil moisture and nutrients on the east coast of Vancouver Island, British Columbia. We determined that at low light levels, site quality has little effect on the growth response of Douglas-fir saplings. At light levels above approximately 40 and 60% full sun, Douglas-fir saplings show statistically significant differences in height and radial growth, respectively, that reflect the differences in soil moisture and nutrient regimes of the sites we examined. Western redcedar approaches its maximum radial and height growth rates at about 30% full sun. Our data suggest that partial-cutting treatments need to create light environments greater than about 40% full sun to achieve growth that represents a high proportion of the site growing potential for Douglas-fir at full sun, while the high shade tolerance of western redcedar allows silvicultural treatments that retain a high amount of forest structure without compromising growth rates of young trees.

Quantitative characterization of nutrient regimes of high-elevation forest soils in the southern coastal region of British Columbia, Canada

To quantify the gradient of plant-available nutrients on high-elevation coastal sites that support growth of Pacific silver fir ( Abies amabilis (Dougl. ex Loud.) Forbes) in southern British Columbia, we collected samples of forest floor and mineral soil (0–30 cm) from montane and subalpine sites within maritime-windward, maritime-leeward, submaritime, and subcontinental climatic strata. The samples were analyzed for acidity, total C, total N, mineralizable-N, and extractable Ca, Mg, K, P, and SO4−S. Relationships between field-identified soil nutrient regimes (SNRs) and measured soil nutrient properties were examined using principal component analysis, discriminant function analysis, and covariance analysis. The nutrient gradient appeared to be heterogeneous as indicated by a relatively low percentage (29%) of variation explained by the first principal component. Within the space of chemical soil properties resulting from principal component analysis, the grouping of samples was weak and the relationship to SNRs also appeared weak. However, using discriminant analysis (DA) 70% agreement was found between field-identified SNRs and the classification based on measured soil properties. Nitrogen-related variables (total N, mineralizable-N, and C/N ratio) and the sum of extractable Ca, Mg, and K were the properties most strongly related to the field-identified SNRs. Mineral soil min-N concentrations appeared to be unrelated to changes in continentality within the study area. These findings agree with the results of previous studies suggesting that mineralizable-N of the mineral soil is the best property for a quantitative characterization of a soil nutrient gradient, and, hence for quantification of field-estimated SNRs. Field-estimated SNRs were also good predictors of site index as they explained the variation in site index of Pacific silver fir similarly well as total N and C/N ratio. However, the absence of a relationship between mineralizable-N and the Pacific silver fir site index requires a further study of plant–soil relationships in the area.

Phenology and Growth Form Distribution in an Alpine Pasture at Tungnath, Garhwal, Himalaya

Studies on phenology and growth form distribution in an alpine pasture of Garhwal Himalaya were undertaken from 1988 to 1998. One hundred seventy-one species were recorded and classified as 5 different growth forms. These species were also classified as early- and late-growing type, on the basis of initiation of their aerial sprouts. Cushion-forming forbs generally emerge as the season commences, that is, immediately after snowmelt. However, the vegetative growth of grasses and other forbs peaked randomly after arrival of the monsoon. Phenophases of different species at higher elevations respond to the availability of the soil moisture and nutrient regimes as well as to temperature and different photoperiodic induction. The spectrum of life forms in the region indicated a hemicryptophytic and geophytic plant climate.

The use of ground vegetation and humus type as indicators of soil nutrient regime for an ecological site classification of British forests

In many countries ground vegetation and humus type are used as indicators of forest soil quality, especially nutrient regime. This paper reports the development of such methods for use in British forests, within a new Ecological Site Classification combining climate, soil moisture regime and soil nutrient regime. To develop a field assessment method for soil nutrient regime, a study was made of soil chemistry, humus type and ground vegetation in British forests. Sites were selected in both mature plantations and semi-natural woodlands. Soil and humus profiles were described and the soil was sampled volumetrically for later chemical analysis. Vascular ground vegetation was recorded in quadrats by species cover fraction, and classified according to the existing British National Vegetation Classification. Soils were analyzed for a number of chemical variables. Vegetation data were treated by application of the species indicator values for soil reaction ( R) and soil nitrogen ( N), as proposed by Ellenberg [Vegetation Ecology of Central Europe, 4th Edition. Cambridge University Press, Cambridge]. Site mean indicator values mR and mN (weighted by species cover fraction) were then calculated. Multivariate statistical analysis techniques were applied to both the soil chemical and the vegetation sample data. Soil nutrient regime was shown to be a composite gradient of several soil chemical variables, of which the pH value and the availability of mineral (especially nitrate) nitrogen, and of calcium, were of particular importance. The species composition of the ground vegetation was related to position on this soil nutrient gradient. The vegetation: soil nutrient correlation using the site mean Ellenberg values was satisfactory ( r=0.89), but was improved by using indicator values generated from within the present data. The occurrence of the major humus types (mor, moder and mull) is broadly related to soil nutrient regime defined in this way. Both ground vegetation and humus type can therefore be used as soil nutrient indicators in British forests. A division of the soil nutrient gradient into five classes (Very Poor, Poor, Medium, Rich and Very Rich) is proposed. Future sampling work may lead to the definition of an additional class of soils with carbonate nutrient regimes. The Ecological Site Classification will provide forest managers in Great Britain with an improved basis for the selection of tree species for planting, and the adoption of silvicultural methods best suited to the site.

Use of understory vegetation in classifying soil moisture and nutrient regimes

One-hundred-and-two white spruce [ Picea glauca (Moench) Voss] stands sampled in the sub-boreal spruce biogeoclimatic zone of British Columbia were used to examine the role of understory vegetation in assessing soil moisture and nutrient regimes. Based on the existing knowledge, each species of indicator value was assigned into one of six indicator species groups for soil moisture and/or one of three indicator species groups for soil nitrogen. On each stand, the frequency of each indicator species group was calculated using % covers of all indicator species. Soil moisture and nutrient regimes were then classified based on calculated frequencies following the criteria proposed in the study. As a result, 16 stands were classified as moderately dry, 27 stands slightly dry, 25 stands fresh, 15 stands moist, 12 stands very moist, and 7 stands as wet; 10 stands were classified as very poor, 20 stands poor, 41 stands medium, 24 stands rich, and 7 stands as very rich. These classifications compared favorably with the two soil-based classifications reported earlier for the same data, with 47-59% of stands in agreement and 38-46% of stands in disagreement in only one class. Testing the classification against soil moisture and nutrient measures and white spruce foliage nitrogen and site index further supported the indicator plant approach to soil moisture and nutrient regime classification. It is concluded that the indicator plant approach is a good alternative to the soil-based approaches that have been commonly applied in site classification systems across Canada.

Mineralogy and genesis of selected soils and their implications for forest management in central and northeastern British Columbia

Soil properties in central and northeastern British Columbia are strongly influenced by parent materials because of geologically young till, glaciolacustrine, and glaciofluvial deposits. We examined pedogenesis on various parent materials to support studies of long-term forest productivity. We sampled nine pedons developed on till (Bobtail, Lucille Mountain, Skulow Lake, Log Lake, Topley, and Kiskatinaw), glaciofluvial (Bowron), and glaciolacustrine (Aleza Lake 1, 2) deposits. The Skulow Lake pedon is distinctive in the occurrence of talc, while the Lucille Mountain pedon has the only clay fraction in which kaolinite is absent. Other pedons on till contain mica, kaolinite, chlorite, smectite, and vermiculite. The Bowron pedon has mica, kaolinite, and chlorite, while the Aleza Lake pedons have mica, kaolinite, chlorite, and 2:1 expanding minerals. In pedons with low amount of 2:1 expanding clays in the C horizon, mica and chlorite appear to degrade into 2:1 expanding clays, while in pedons with C horizons containing 2:1 expanding clays, mica and chlorite seem stable and the formation of hydroxy-interlayered clays is the predominant process. Podzolization and lessivage are major pedogenic processes, while redoximorphic processes are observed in some pedons with illuvial Bt horizons. Significant soil compaction hazards are presented by the medium and fine soil surface textures. Although clay-rich Bt horizons may benefit soil nutrient regimes, conservation of nutrient-rich forest floors is important, given the low S contents in mineral soils. High contents of feldspars in these soils provide a large reserve of nutrients such as Ca and K. Key words: Clay minerals, parent material, podzolization, lessivage

Site and soil characteristics related to the incidence of Inonotus tomentosus

Inonotus tomentosus (Fr.) Teng causes Tomentosus root disease in spruce trees throughout the boreal and sub-boreal forests of British Columbia. Site and soil characteristics are related to the incidence of this fungus in wet, cool sub-boreal spruce forests located near Prince George, British Columbia. Two-hundred and ninety-six plots, 25.2 m in diameter, were examined to determine the incidence of I. tomentosus, and several site and soil variables were measured. These included soil moisture and nutrient regime, slope position, soil texture, soil coarseness, humus form, spruce density, tree species composition and soil pH. The incidence of I. tomentosus infection ranged from none to 31% of spruce trees per plot. Significant differences ( p < 0.05) in percent infection were found between soil moisture regimes, soil moisture by soil nutrient regimes, and slope position. All of these site and soil variables are used, in British Columbia, to determine a `site series', which is a site specific ecological classification unit used to determine harvest methods and silviculture prescriptions. The most important site variable influencing disease incidence is suggested to be soil moisture regime as influenced by slope position and soil texture.

Photosynthesis, water and nitrogen use efficiencies of four paper birch ( Betula papyrifera) populations grown under different soil moisture and nutrient regimes

A greenhouse experiment was conducted to determine how four populations of paper birch ( Betula papyrifera Marsh.), adapted to particular temperature, water and photoperiod regimes responded physiologically to different soil water and nutrient regimes. Seedlings of each of the four populations (Eaglet, LeeCreek, Porcupine and Skeena) from British Columbia were planted in pots and subjected to high and low water and nitrogen regimes for 4 months. Net photosynthesis ( A), stomatal conductance ( g s), water use efficiency (WUE) and nitrogen use efficiency (NUE) were measured and compared among treatments. Trade-offs between WUE and NUE were examined. Soil moisture was the major factor affecting A for all the populations. All populations showed relatively high A in the high-water and high-nitrogen (HWHN) treatment, ranging from 8.5 to 9.9 μmol CO 2 m −2 s −1. Photosynthesis of trees in the low-water and high-nitrogen (LWHN) treatment was about 45% of that in the HWHN treatment. There was a linear increase in A as g s increased in all populations. A decreased with increasing vapor pressure deficit (VPD). The populations demonstrated significantly different relationships between A and g s, and VPD, with the LeeCreek population being the most conservative. This may provide a physiological basis for provenance selection and seed transfer. Eaglet and LeeCreek populations had lower WUE at the same level of NUE compared with Porcupine and Skeena populations. Porcupine and Skeena populations may be more suitable for moist sites due to their greater capacity to sequester water quickly, while the LeeCreek and Eaglet populations may be more suitable for drier interior sites where long drought periods can occur.

Characterization of nutrient regimes in some continental subalpine boreal forest soils

To determine whether field-identified soil nutrient regimes (SNRs) can be characterized and segregated by direct soil nutrient measures, we collected samples of forest floor and mineral soil (0 to 30 cm) from a wide range of forest sites throughout the Engelmann Spruce — Subalpine Fir (ESSF) zone of British Columbia. The samples were analyzed for acidity, total C, total N, mineralizable N, and extractable Ca, Mg, K, P, and SO4-S. The study sites were stratified according to an a priori field classification (SNRs) and an a posteriori classification derived from quantitative classification (groups) using all direct measures of nutrients as discriminating variables. The two classification methods had 72% agreement. Regardless of the classification, nitrogen-related variables (C:N ratio, total N, and mineralizable N) in the mineral soil segregated best among SNRs or groups indicating the presence of a steep, N-driven regional soil nutrient gradient. Multiple regression models using SNRs, groups, or direct measures of nutrients together with surrogates of climate (elevation, latitude, and/or longitude) as predictors had the similar accountability for the variation in subalpine fir and Engelmann spruce site index (0.41 ≤ R2 ≤ 0.65). The similarity in the accountability for site index justifies the use of the a priori classification in estimating site quality. Comparison of mineralizable-N values for field-identified SNRs between different climatic regions showed similarities between boreal climates and discrepancies between boreal and cool mesothermal climates. The study gave further evidence that indices of plant-available nitrogen in the upper mineral soil provide useful measures for field-identified SNRs, but indicated that it may be necessary to expand the existing five-class a priori classification to accommodate differences in regional soil nutrient gradients. Key words: Classification, Engelmann spruce, subalpine fir, nitrogen, site index, soil nutrient regime

Mounding in the Sub-boreal Spruce Zone of west-central British Columbia: 8-year results

Results are presented from two site preparation trials involving mounding on a moist to wet site with a medium soil nutrient regime (5–6/C) located in a lower slope to toe of slope position and on a near-level area upslope from the first site with medium soil moisture and nutrient regimes (4/C). Both trials compared the performance of long-rooted hybrid white spruce (Picea glauca × P. engelmannii [Parry ex Engelm.]) (Sxw) container stock (PSB 323) to that of a standard-sized stock (PSB 313) planted in inverted mounds and untreated spots. The trial on the first site also tested the effectiveness of two mound capping depths and of planting the 313 stock to two different depths in mounded spots. After eight seasons, there were no significant differences between 313s and 323s in terms of height growth or proportions of free growing trees. Although diameter growth was significantly greater among 323s in mounds compared to 313s this relatively small difference is unlikely to justify the higher cost of the larger stock. Height and diameter growth among 313s were 17 and 22% greater, respectively, for trees planted in mounds with 20 cm of capping compared to 12 cm of capping. Deep-planting in mounds consistently resulted in slight increases in height growth and survival relative to planting to the standard depth, though differences were not statistically significant Rates of growth were substantially greater among trees planted in mounds compared with those in untreated spots.The greatest relative differences were noted on the first site where height growth among 313s was 43 to 74% greater in mounded treatments depending on planting depth and capping thickness, with similar improvements in diameter growth. Key words: Site preparation, mounding

Humus forms of trembling aspen ecosystems in northeastern British Columbia

For humus forms are one of the less known features of trembling aspen ecosystems, we studied them in 18 stands located across a range of soil moisture and nutrient regimes in the Boreal Black and White Spruce of northeastern British Columbia. The majority of study on humus forms featured loose Fz (zoogeneous) horizons, overlying thicker, compact-matted Fm (mycogeneous) horizons. Fine roots were concentrated at the lower boundary of Fm horizons. The occurrence of both Fz and Fa horizons implied the presence of two contrasting decomposition processes: one dominated by soil fauna (Fz) and the other dominated by soil fungi (Fm). We consider these humus forms to represent an intergrade between Mors and Moders, as supported by the results of chemical analysis. However, the Fz–Fm profile did not fit any taxon of the Mor or the Moder order in the existing humus form classification, and by default these humus forms had to be considered Hemimors. We suggest that a higher temperature near the ground surface and aspen litter are responsible for the development of the upper Fz horizon, and a lower temperature and dense root mat are responsible for the development of the lower Fm horizon. Considering this unique and persistent pattern across a range of aspen ecosystems, we proposed a new group of the Moder order—Lamimoder.

Relative growth rate and biomass allocation of paper birch (Betula papyrifera) populations under different soil moisture and nutrient regimes

Seedlings of four geographically diverse paper birch (Betula papyrifera Marsh.) populations native to British Columbia were grown under low and high levels of water and nitrogen in a greenhouse for 3 months to examine the relative sensitivity of each population to water and nutrient availability. Nine sequential measurements on height and basal diameter growth were made, and then the seedlings were harvested for final biomass measurements. Under optimal conditions the highest elevation population ceased height growth, while the low-elevation coastal population continued to increase in height under all treatment conditions. Plants of all populations grown under high N conditions grew faster and had larger total biomass and lower root/shoot ratios than plants grown under low N conditions. Relative growth rate was significantly correlated with shoot and foliage biomass, leaf area, and root weight ratio. All populations generally responded more to low N level than to low moisture level in terms of height growth, relative growth rate, total biomass, and root/shoot ratio. This suggests that the populations observed in this study are better adapted to drought than poor soil nutrient availability. Therefore, consideration of site quality, which includes soil moisture regime and soil nutrient regime, should be a primary concern when allocating birch seed lots in a planting program.

Relative growth rate and biomass allocation of paper birch (&lt;i&gt;Betula papyrifera&lt;/i&gt;) populations under different soil moisture and nutrient regimes

Relative growth rate and biomass allocation of paper birch (&lt;i&gt;Betula papyrifera&lt;/i&gt;) populations under different soil moisture and nutrient regimes

The effect of forestry drainage on vertical distributions of major plant nutrients in peat soils

Vertical distributions of total N, P, K, Ca and Mg in a 0–60 cm surface peat layer were studied at 80 pine mire sites in southern Finland. The sites fell into two categories according to the soil nutrient regime: Meso-oligotrophic and oligo-ombrotrophic, and formed a chronosequence from undrained sites to sites drained 55 years ago. A statistically significant drainage age effect on the gravimetric (mg g-1) concentration profile forms was detected for all nutrients except K. In oligo-ombrotrophic sites the concentration of N increased following drainage in the topmost layer (0–10 cm) and that of P in all layers. In meso-oligotrophic sites the changes in N and P profiles were obscure. The concentration profiles of K remained clearly surface-enriched in both site type groups, but there was a general drop in the concentration values immediately after drainage. Ca and Mg decreased, especially in the 10–20 and 25–35 cm layers in both site type groups. The volumetric (kg m-3) nutrient concentrations clearly reflected the increase in the bulk density of the surface peat occurring after drainage. The compaction of peat had compensated for the effect of the processes removing nutrients from the soil (increased tree stand uptake, leaching); for Ca and Mg to a lesser degree than for the other nutrients. It was concluded that the N, P and K profiles did not show changes that would be likely to affect site productivity, whereas the net loss of Ca and Mg may cause problems in the longer term. As the total K capital of the sites was in general rather small, a disturbance in the biological cycle, such as cutting of the tree stand, may be critical.

Effect of fertilization on ozone-induced changes in the metabolism of birch (Betula pendula) leaves.

Cloned cuttings of Betula pendula Roth were grown in field fumigation chambers at Birmensdorf throughout one growing season in filtered air with either < 3 (control) or 90/40 nl l-1 O3 (day/night; ozone generated from pure oxygen). Each ozone regime was split into high and low soil nutrient regimes by watering plants with either a 0.05 % or a 0.005% solution of a fertilizer which contained macronutrients and micronutrients. Fertilization had a strong effect on plant growth, enzyme activities and the expression of ozone-induced effects at the biochemical level. The activities of PEPC and Rubisco were enhanced about threefold in the plants with high fertilization (HF). Significant effects of ozone were in most cases found only in the older leaves of the plants with low fertilization (LF), There, sucrose, glucose and fructose levels were enhanced. In both fertilization treatments, the number of starch granules along the minor veins was increased. These ozone effects point to a decreased or inhibited phloem loading. The increased PEPC activity and the enhanced malate levels in the ozone-exposed plants might be the result of a redirection of carbon flow from sucrose synthesis and translocation towards anapleurotic processes, which can feed detoxification and repair of ozone injury as indicated by enhanced respiration. These findings agree well with the observed effects of ozone in lowering the root: shoot biomass ratio. Although there was a marked reduction in the O3 /LF plants, O3 /HF plants showed no significant response. Inositol was decreased under ozone exposure in both fertilizer treatments, contrasting with the pattern for carbohydrates. These results demonstrate the role of fertilization as an important modifier of ozone-induced effects at the plant biochemical level. Well fertilized plants appear to cope better with the impact of ozone on metabolism.

Soil nutrient regime classification for white spruce stands in the Sub-boreal Spruce Zone of British Columbia

Using mineralizable N (kg/ha) and C/N ratio measured within the rooting zone as differentiating characteristics, 93 white spruce (Picea glauca (Moench) Voss) stands from the Sub-boreal Spruce Biogeoclimatic Zone of British Columbia were quantitatively classified into five soil nutrient regimes (i.e., very poor, poor, medium, rich, and very rich) by cluster analysis and discriminant analysis. Significant differences in soil chemical properties, frequencies of nitrogen indicator species groups, foliar nutrients, and site index were found among the five soil nutrient regimes. The classification compared favorably (60% match) with the field classification based on topographic and soil morphological features using a dichotomous key. By relating each soil nutrient regime to the quantities of soil nutrients available to plants traditional site classification units can be directly linked to resource availability, thus potential productivity, of the sites. It is recommended that further studies of soil nutrient regime classification in the Sub-boreal Spruce Biogeoclimatic Zone should concentrate on characterizing the regional gradient of soil available nitrogen. Resume : En utilisant comme caractOristiques distinctives liazote minOralisable (kg/ha) et le ratio C/N mesurOs dans la zone dienracinement, 93 peuplements diOpinette blanche (Picea glauca (Moench) Voss) situOs dans la zone biogOoclimatique sub-borOale de liOpinette en Colombie-Britannique ont OtO quantitativement classifiOs en cinq groupes sur la base du rOgime nutritif du sol (c.-‡-d., trs pauvre, pauvre, moyen, riche et trs riche) par lianalyse de groupement et lianalyse discriminante. Il y avait des diffOrences significatives dans les propriOtOs chimiques du sol, la frOquence des groupes de plantes indicatrices diazote, les nutriments foliaires et les indices de site entre les cinq groupes de rOgime nutritif du sol. La classification se comparait favorablement (60% diappariement) avec la classification au champ basOe sur les aspects topographiques et morphologiques du sol en utilisant une clO dichotomique. En Otablissant un rapport entre le rOgime nutritif du sol et les quantitOs de nutriments du sol disponibles aux plantes, les unitOs traditionnelles de classification des sites peuvent Œtre directement reliOes ‡ la disponibilitO des ressources, donc ‡ la productivitO potentielle des sites. Les recherches futures sur la classification du rOgime nutritif du sol dans la zone biogOoclimatique sub-borOale de liOpinette devraient Œtre concentrOes sur la caractOrisation du gradient rOgional de disponibilitO de liazote du sol. (Traduit par la ROdaction)

Using Ellenberg Indicator Values to Assess Soil Quality in British Forests from Ground Vegetation: A Pilot Study

1. As a pilot study, descriptions of the vegetation and soil sampling were carried out on 20 forest sites to investigate the soil factors likely to be of importance in assessing soil quality for silvicultural/ecological purposes, and to see how useful indicator species were in predicting soil factors. 2. Soil analytical properties, mostly expressed in units of kg ha -1 , were examined statistically by principal components analysis. 3. The vegetation descriptions were treated numerically by assigning to each plant species Ellenberg indicator values for F (soil moisture), R (soil reaction) and N (soil nitrogen). The indicator values were weighted either using the Domin scores for abundance or the frequency of each species in the vegetation. 4. Measures of nitrogen availability (especially mineralizable NO 3 and NH 4 ) and pH were the most important variables loading Principal Component 1 (PC1). 5. The site mean indicator values for R (mR) and N (mN) were combined (mR + mN) to provide a simple proxy for 'soil nutrient regime', and the site mean indicator value for F (mF) was used as a proxy for 'soil moisture regime'. 6. The scores for each site on PC1 were related to the values of mR + mN. 7. A grid formed from mF and (mR + mN) was used to ordinate the sites in terms of 'soil quality' (soil nutrient regime and soil moisture regime). 8. Further work along similar lines is proposed to enable local (British) ecological indicator values for plant species to be developed.

A site classification for Scottish native woodlands

Summary The proposed site classification should assist in choice when creating or rehabilitating native woodlands on site types of different quality. Eight climatic zones are defined by warmth and wetness factors. Eight soil moisture regimes are defined by water table depth and the amount of available water in summer. Six soil nutrient regimes are defined by soil acidity and nitrogen availability. Woodland and scrub sub-communities of the National Vegetation Classification are ordinated by their preferences for soil moisture and soil nutrients, using Ellenberg ecological indicator values. After stratification by climatic zone, the communities are then located on the grid of soil moisture and nutrient regimes. The actual and relative positions of the communities and sub-communities are discussed in relation to existing knowledge of their distribution in relation to climate and soil types.

Soil nutrient regime classification for white spruce stands in the Sub-boreal Spruce Zone of British Columbia

Soil nutrient regime classification for white spruce stands in the Sub-boreal Spruce Zone of British Columbia

Use of synoptic variables in predicting white spruce site index

Based on data from 102 white spruce-dominated stands in the sub-boreal spruce zone of British Columbia, forest site quality was evaluated using both species-specific and ecological approaches. White spruce site index, determined from stem analysis data, was used as a species-specific measure of site quality. Climate regimes and soil moisture, aeration and nutrient regimes were used as ecological measures of site quality. Subzones and variants, differentiated by zonal vegetation, were used as synoptic measures of climate. Soil moisture regimes, differentiated by actual/potential evapotranspiration ratio, depth to a gleyed layer or prominent mottles, and depth to a groundwater table, were used as synoptic measures of soil moisture. Soil aeration regimes, differentiated by soil water saturation, slope, drainage, and soil texture, were used as synoptic measures of soil aeration. Soil nutrient regimes, differentiated by mineralizable nitrogen (kg ha-1) and carbon/nitrogen ratio, was used as synoptic measures of available soil nutrients. These measures were related to white spruce site index through regression analysis and limiting factor analysis. The results showed that soil moisture, aeration, and nutrients were growth-limiting factors while climatic variations within the sub-boreal spruce zone were not important. The best regression model explained about 90% of the total variance in site index, with standard error of estimates of 1.2 m. This strong relationship suggests that ecological site classifications can be used to evaluate both ecological site quality and forest productivity.