Richardson, J., and J.P. Hall. 1973b. Natural regeneration after distur- Weidenhamer, J.D., D.C. Hartnett, and J.T. Romeo. 1989. Density-bance in the forest of eastern Newfoundland. Inf. Rep. N-X-90. dependent phytotoxicity: Distinguishing resource competition and Environ. Canada, Canadian Forestry Serv., St. John’s, NF. allelopathic interference in plants. J. Appl. Ecol. 26:613–624. Thompson, I.D., and A.U. Mallik. 1989. Moose browsing and allelo- Zackrisson, O., and M.-C. Nilsson. 1992. Allelopathic effects by
Empe-pathic effects ofKalmia angustifoliaon balsam fir regeneration in trum hermaphroditumon seed germination of two boreal tree spe-central Newfoundland. Can. J. For. Res. 19:524–526. cies. Can. J. For. Res. 22:1310–1319.
Weetman, G.F., R. Fournier, J. Baker, and E. Schnorbus-Panozzo. Zar, J.H. 1996. Biostatistical analysis. (3rd ed.) Prentice-Hall, New 1989a. Foliar analysis and response of fertilized chlorotic Sitka Jersey.
spruce plantations on salal dominated cedar-hemlock cutovers on Zhu, H., and A.U. Mallik. 1994. Interactions betweenKalmiaand Vancouver Island. Can. J. For. Res. 12:1512–1520. black spruce: Isolation and identification of allelopathic com-Weetman, G.F., R. Fournier, J. Baker, E. Schnorbus-Panozzo, and A. pounds. J. Chem. Ecol. 20:407–421.
Germain. 1989b. Foliar analysis and response of fertilized chlorotic Sitka spruce plantations on salal dominated cedar-hemlock cut-overs on Vancouver Island. Can. J. For. Res. 12:1501–1511.
Black Spruce Growth and Understory Species Diversity
with and without Sheep Laurel
Azim U. Mallik*
ABSTRACT Richardson and Hall, 1973a, p. 63, 1973b, p. 46; Wall, 1977, p. 55). Competition and allelopathic effects of Growth and understory species diversity of black spruce [Picea
sheep laurel have been attributed to the regeneration
mariana(Miller) B.S.P.] planted in central Newfoundland at
contigu-ous sites with and without dense cover of sheep laurel (Kalmia angus- failure and poor growth of conifers (Mallik, 1987, 1990, tifoliaL.) were compared. Black spruce stem density and volume per 1992, 1996; Mallik and Roberts, 1994). In eastern and hectare were calculated by sampling 10 circular quadrats (50 m2), and
central Newfoundland, large areas of moderately pro-the cover of all plant species was determined by sampling 20 quadrats ductive black spruce forests with sheep laurel un-(1 m2) in each site. In addition, 10 randomly sampled planted black
derstory have been converted into sheep laurel domi-spruce samplings from each site were analyzed for stem height, basal nated heath following forest disturbance (Mallik, 1995). diameter, and foliar chemistry. Results showed a significantly lower
A regeneration survey of 5888 plots in black spruce stem height and basal diameter (65 and 51%, respectively) at the site
plantations found that 55% of them contained sheep with dense sheep laurel cover (36%) compared with the site with
laurel (English and Hackett, 1994, p. 12). Black spruce sparse sheep laurel cover (,1% sheep laurel cover, and henceforth
in sheep laurel infested sites exhibits typical symptoms: referred to as the non-sheep laurel site for simplicity). Black spruce
grown at the sheep laurel dominated site contained significantly higher Poor plant height and diameter growth and short and quantities of Ca, Al, Fe, and K in the needles than that grown at the chlorotic needles, as observed in other conifers in the non-sheep laurel site. The sheep laurel dominated site also had a presence of different ericaceous plants (Handley, 1963; significantly higher mean organic matter depth of 8.3 cm compared Gimingham, 1972; de Montigny and Weetman, 1990; with 5.6 cm at the non-sheep laurel site. Canonical correspondence Fraser, 1993, p. 166; Inderjit and Mallik, 1996a; Jader-analysis (CCA) of the species cover data clearly separated the sheep
lund et al., 1997). Black spruce forests that are domi-laurel dominated plots from the non-sheep domi-laurel plots. The sheep
nated by sheep laurel tend to have a reduced species laurel dominated site had reduced species richness of vascular plants
richness and deficiency in available nutrients (Damman, but increased species richness for lichens compared with the
non-1971). Recently, Yamasaki et al. (1998) reported that sheep laurel site. Allelopathy associated with phenol-induced soil
black spruce seedlings in close proximity of sheep laurel nutrient imbalance and nutrient stress is a possible cause for black
spruce growth inhibition at the sheep laurel dominated site. (,1 m) experience lower height, biomass, root/shoot ratio, foliar N and P, and lower mycorrhizal infection than those growing farther (.1 m) away from sheep laurel.
R
apid growth of sheep laurel after clear cuttingDamman (1971, 1975) suggested that long-term occu-and fire in sheep laurel–black spruce communities pancy of a site by sheep laurel causes irreversible soil has been widely observed in eastern Canada,
particu-degradation, leading to a stable heath formation by pre-larly at sites with organic and coarse textured medium- cluding forest regeneration. Apparently sheep laurel, quality soil types (Page, 1970, p. 7; van Nostrand, 1971,
like other ericaceous plants, is able to grow in nutrient p. 68; Damman, 1975). The natural regeneration of black poor conditions where black spruce growth is very much spruce at these sites is poor, and planted black spruce restricted. There is evidence suggesting that the erica-seedlings exhibit stunted growth (Candy, 1951, p. 224; ceous plants are able to access the N that is bound in the protein–polyphenol complex through the ericoid Dep. of Biol., Lakehead Univ., Thunder Bay, ON, Canada P7B 5E1. mycorrhizae, but this N is not available to the conifers Received 25 Jan. 2000. *Corresponding author (azim.mallik@
lakeheadu.ca).
Abbreviations:CCA, canonical correspondence analysis; IAA, indole-acetic acid.
MALLIK: BLACK SPRUCE GROWTH AND SPECIES DIVERSITY WITH SHEEP LAUREL 93
through their ectomycorrhizal association (Bending and Species Composition and Richness
Read, 1996). It is also possible that the nutrient require- The cover of all the understory plants was determined by ments of sheep laurel are lower than those of black sampling 10 randomly placed 1-by-1-m quadrats in each of spruce. The rapid proliferation of sheep laurel after the sheep laurel and non-sheep laurel sites. The thickness of clear cutting and fire and the associated black spruce the organic and Ae horizon was determined from 25 soil pits that were randomly dug in each of the sheep laurel and non-growth inhibition is a serious problem for forest
man-sheep laurel sites. agement in central Newfoundland. Recognizing this
problem, the provincial government of Newfoundland
and Labrador has implemented new forest management Statistical Analysis guidelines that discourage forest harvesting in sites with
A pairedt-test was used to determine the significant differ-dense sheep laurel cover. Although poor black spruce ence of the growth parameter and foliar nutrient means of growth in the presence of dense sheep laurel cover has black spruce at the sheep laurel and non-sheep laurel sites. been widely observed in Atlantic Canada, to this day PC-ORD (McCune and Mefford, 1995) was used to ordinate no quantitative evaluation of black spruce growth has the 20 sampling plots with and without sheep laurel based on been made in plots with and without sheep laurel. The the species cover data. The species–environment relationships objectives of the present study were to compare (i) the were analyzed using CCA with Pearson correlation. growth and foliar nutrient concentrations of planted
black spruce and (ii) the species composition, richness,
RESULTS
and diversity of understory plants in contiguous plotswith and without sheep laurel.
Black Spruce Growth Response
Black spruce stem height and basal diameter were
STUDY AREA AND METHODS
significantly less (65 and 51%, respectively) at the site The study area belongs to the north-central subregion of with dense cover (36%) of sheep laurel compared with the central Newfoundland ecoregion that is characterized by
the non-sheep laurel site (Fig. 1). Consequently, after a high maximum summer temperature and a lower rainfall
15 yr there was 85% less black spruce volume at the and higher fire frequency than anywhere on the island
sheep laurel dominated site compared with the non-(Meades and Moores, 1994, p. 226). Because of the high fire
sheep laurel site (Fig. 1). Black spruce height growth frequency, the area is dominated by pure black spruce stands
of seed origin and aspen (Populus tremuloides Michaux) was consistently less at the sheep laurel dominated site stands originating from root suckering. The soil is typically a than at the non-sheep laurel site (Fig. 2). The stem coarse textured humo-ferric podzol. The area has rolling to density of black spruce was 34% less at the sheep laurel undulated topography that is characterized by shallow, me- dominated site compared with the non-sheep laurel site dium-quality till with a soil texture ranging from sandy loam (Fig. 1). The current stem density of the two sites con-to loam. Black spruce after disturbance in this relatively low
sists of planted seedlings as well as natural regeneration moisture, coarse-textured soil suffers from regeneration
fail-of black spruce. However, the natural regeneration fail-of ure, particularly when sheep laurel occurs as a dense
un-black spruce at the sheep laurel site was about one-derstory (Meades and Moores, 1994, p. 226).
third (900 stems ha21) of that of the non-sheep laurel This study was conducted in a 15-yr-old black spruce
planta-tion in Sandy Pond, central Newfoundland (488509N, 558249 site (2400 stems ha21).
W; altitude of 153 m). The area was harvested by clear cutting Black spruce grown at the sheep laurel plots con-in 1979, scarified con-in 1981, and planted with contacon-inerized black tained significantly higher concentrations of Ca, Al, Fe, spruce in 1982—15 yr before this study. The planting density and K in the needles than that in the non-sheep laurel was 2100 seedlings ha21. Approximately half of the 10-ha
plots (Table 1). The sheep laurel dominated plots had plantation contained on an average of 36% sheep laurel cover
a significantly higher organic matter depth (8.3 cm) than that was fairly uniformly distributed while the other half of
the non-sheep laurel plots (5.6 cm). The organic matter the plantation had,1% sheep laurel cover. The sheep laurel
depth was strongly related to thex-axis (r 5 20.841) dominated site had a thicker organic layer than the non-sheep
while the Ae horizon depth was strongly related to the laurel site. Both sites had coarse-textured freely drained sandy
y-axis (r5 298.2). They-axis did not separate the sam-loam soil with a 0.5 to 2 cm thick Ae horizon.
pling plots into levels of sheep laurel condition,
sug-Black Spruce Growth Response
Table 1. Foliar nutrient concentrations of planted black spruce Ten 50-m2circular quadrats were randomly placed in each
in sheep laurel and non-sheep laurel sites. Values are the means of the sheep laurel and non-sheep laurel areas. The stem
of 10 samples6SD. height and basal diameter of all black spruce saplings were
Nutrient Sheep laurel Non-sheep laurel
determined in each quadrat. From these data, the stem density
and volume of black spruce were determined. Ten randomly N, % 1.028
60.038 1.02860.033
selected planted black spruce saplings were destructively sam- P, mg kg21 8.7211
60.347 8.235960.278
K, mg kg21 3495
6205.95a 44036217.31b pled from each site to determine their age and yearly growth
Al, mg kg21 0.7525
60.084a 0.518460.053b increment by measuring their annual ring widths in two
direc-Ca, mg kg21 56.949
68.146 56.146664.717 tions perpendicular to each other. The planted black spruce Cu, mg kg21 0.0218
60.004 0.03260.005
seedlings were recognized by their presence in the lines with Fe, mg kg21 0.2821
60.018a 0.224760.014b Mg, mg kg21 9.8706
60.52 9.59260.689
regular spacing. Foliar samples were collected at the mid
can-Mn, mg kg21 19.5179
62.437 15.252263.184 opy level from 1-yr-old branches of black spruce for
chemi-Zn, mg kg21 0.3863
Fig. 1. (A) Mean stem height, (B) basal diameter, (C) stem density, (D) and volume of black spruce in sheep laurel and non-sheep laurel plots at Sunday Pond, NF, Canada 15 yr after planting.
gesting that this axis had picked up within-site vari- with a stem density of 4500 stems ha21, the non-sheep
ability. laurel site is comparable with Site Index 10 (Newton,
1992). By contrast, the sheep laurel dominated site is
Black Spruce Crown Closure and Understory
comparable to Site Index 7 (Newton, 1998).Species Cover, Richness, and Diversity
Sheep laurel cover at the two sites was 48.5 and 1.0%, respectively. The sheep laurel dominated site was also With smaller black spruce, the sheep laurel dominatedassociated with dense cover of blueberry (Vaccinium
site had relatively open canopy 15 yr after planting, with
angustifolium Aiton) and schreberi moss [Pleurozium
only 8.5% black spruce cover. In contrast, the
contigu-schreberi(Brid.) Mitt.]—29.5 and 44.5%, respectively, ous non-sheep laurel site was approaching canopy
clo-in contrast to 18.0 and 20.0% at the non-sheep laurel sure, with 56% black spruce cover (Table 2). In the
site. The cover of bunchberry (Cornus canadensis L.), context of the stand density management diagram for
however, remained similar (12.3 and 14%) at the two Newfoundland (Newton and Weetman, 1993) black
spruce crown closure approaching at the age of 16 yr sites (Table 2).
MALLIK: BLACK SPRUCE GROWTH AND SPECIES DIVERSITY WITH SHEEP LAUREL 95 Table 2. Species cover, richness, and diversity in sheep laurel and non-sheep laurel sites. Values are calculated from 10 quadrats (1 by
1 m) in each site.
% Cover Richness Diversity
Species Sheep laurel Non-sheep laurel Sheep laurel Non-sheep laurel Sheep laurel Non-sheep laurel
Vascular plants 12 16 1.24 1.23
Picea mariana 8.569.9 56625.6
Betula papyrifera 263.5 0.360.95
Larix laricinia 0 2.164.9
Populus tremuloides 0 1.863.8
Prunus pensylvanica 0 1.362.2
Nemopanthus macronuta 0.461.3 0
Viburnum cassinoides 0.461.3 0
Kalmia angustifolia 48.5627.0 162.1
Rhododendron canadense 369.5 0
Vacciniumspp. 29.569.6 18.1616.7
Gaultheria hispidula 3.366.7 10.8611.6
Cornus canadensis 3.565.8 1466.6
Linnaea borealis 0 0.561.6
Soidago rugosa 0 162.1
Epilobium angustifolium 0 0.561.1
Potentilla anserina 0 0.561.6
Cypripedium reginae 0 0.460.8
Vaccinium vitis-idaea 5.469.5 0
Mitella nuda 3.864.6 163.2
Maianthemumsp. 0.360.95 2.364.6
Bryophytes and Pteridophytes 7 9 1.01 .95
Pleurozium schreberi 44.5628.8 20.1622.2 Hylocomium splendens 1.563.4 0.861.8 Ptilium crista-castrensis 967.4 2.863.5
Sphagnumspp. 163.1 0
Polytrichumspp. 4.965.6 0
Dicranum scoparium 1.863.5 2.262.2 Dicranum polyseptum 11.763.5 9.864.4
Lycopodium dendroideum 0 0.360.95
Lycopodium annotinum 0 163.2
Lichens 9 5 .69 .89
Cladina rangiferina 163.2 0
Cladina alpina 0 161.1
Cladina arbuscula 0.360.95 4.464.7
Cladinaspp. 0 4.865.0
Permelia sulcata 4.965.4 0
Cladonia cenotea 1.862.6 0
Cladonia cornicraea 6.665.7 1.863.2
Cladonia fimbriata 0 1.261.5
Peltigera apthosa 0.561.6 0
Although the overall species richness of the sheep of black spruce. Although the stem density of black laurel and non-sheep laurel sites was comparable with spruce at the sheep laurel dominated site (|3000 stems
only 28 to 30 species, the two sites were markedly differ- ha21) was less than that of the non-sheep laurel site ent in terms of the species composition, richness, and (|4500 stems ha21) (Fig. 1), this difference is not critical
diversity of the vascular plants and lichens. The sheep from a resource management perspective because a den-laurel dominated site contained 12 species of vascular sity of 3000 stems ha21is considered sufficient for black plants and five species of lichens, whereas the non-sheep spruce regeneration. What is more important, however, laurel site contained 16 species of vascular plants and is that the height and volume of black spruce in the nine species of lichens (Table 2). A CCA of the species sheep laurel dominated plots is consistently less than cover data separated the sheep laurel dominated plots that of the non-sheep laurel plots.
from the non-sheep laurel plots (Fig. 3) along the Similar growth inhibition of black spruce has been
x-axis (Eigenvalue 5 0.22), which explained 12.7% of found in labrador tea dominated sites (Inderjit and Mal-the variance in Mal-the species data. lik, 1996a). However, at the labrador tea dominated site, conifer growth tended to improve 7 yr after planting. A poor early growth and eventual increased growth of
DISCUSSION
black spruce associated with a labrador tea dominated site was also reported by LeBarron (1948, p. 60). In the Both the stem density and growth of black sprucewere significantly less at the sheep laurel dominated site present study, the sheep laurel dominated site exhibited significantly slow growth, and no subsequent growth in (Fig. 1). Significant natural regeneration has occurred
in both sites because the planting density was 2100 seed- height of black spruce was observed 15 yr after planting. Thus, the growth inhibitory effect of sheep laurel on lings ha21. However, recruitment of black spruce in
sheep laurel dominated site was about one-third that of black spruce seems to be more long-term than the effects of labrador tea. Damman (1971) suggested that long-the non-sheep laurel site, indicating that long-the presence
irre-Fig. 3. Canonical correspondence analysis (CCA) of sheep laurel and non-sheep laurel plots showing the significance of sheep laurel cover and organic matter depth in their separation.
versible habitat degradation, converting conifer forests The primary objective of the present paper was to quantify the growth differences of black spruce at con-into ericaceous heath. He attributed this vegetation shift
to the high rate of organic accumulation, soil acidifica- tiguous sheep laurel and non-sheep laurel sites. Perhaps it is safe to assume that the contiguous sheep laurel and tion, and nutrient sequestration in the presence of
sheep laurel. non-sheep laurel sites initially belonged to the same site
type, and the invasion of sheep laurel transformed it The height and diameter (at breast height, DBH) of
the destructively sampled planted black spruce of the into a lower site index type (Damman, 1964, p. 62, 1971). What is not known for sure is how long sheep laurel sheep laurel and non-sheep laurel sites were compared
with the site index curves of naturally regenerating pure has been occupying the site. A study of disturbance-induced sheep laurel proliferation at a chronosequence black spruce in central Newfoundland (Newton, 1992).
It was found that the black spruce at the non-sheep and associated black spruce regeneration failure and habitat degradation will elucidate the role of sheep lau-laurel site fit close to Site Index 12 and that of the sheep
laurel dominated site was comparable to Site Index 10. rel in this vegetation shift.
Inderjit and Mallik (1996a) compared the growth and Using the site index curves of Newton (1992), the
pro-jected height of black spruce at the age of 50 in the non- foliar nutrients of planted black spruce in labrador tea and non-labrador tea sites. They attributed the poor sheep laurel and sheep laurel dominated sites would be
12.18 and 10.32 m, respectively. However, the values growth of black spruce in labrador tea dominated sites to a lower foliar N and to a soil nutrient imbalance that for the black spruce growing at the sheep laurel
domi-nated site may have been overestimated for at least a was due to the high phenolic content of the labrador tea litter. In this study, the black spruce grown at the couple of reasons. First, trees at the sheep laurel
domi-nated plots were too small to determine a meaningful sheep laurel dominated site had smaller needles but did not have lower concentrations of foliar N compared diameter at breast height, and secondly, as Newton
(1992) cautioned, the site index curves of age classes 1 with the non-sheep laurel site. These values are very similar and within the adequate range (0.95–1.10%) for to 20 may not be very accurate for the small sample
size of his model. In a subsequent paper, Newton (1998) black spruce according to Lowry and Avard (1968, p. 54). Swan (1970), however, considered 1.20% foliar N presented a more realistic site index for black spruce in
sheep laurel sites by developing successional vectors to be low for black spruce growth. There is no evidence in the present data to suggest that foliar N deficiency based on the size–density relationship (Newton and
Weetman, 1993). He suggested that delayed crown clo- is a cause of the growth limitation of black spruce in the sheep laurel dominated plots. However, other nutri-sure due to poor spruce growth and seedling mortality
in the presence of sheep laurel will lower the site index ent and heavy-metal imbalances may be responsible. Significantly higher concentrations of foliar Al and Fe to 7 or even 4, depending on the black spruce stem
density and the density and longevity of sheep laurel at were found in the black spruce at the sheep laurel domi-nated site compared with that of the non-sheep laurel a site. He further suggests that even a productive black
spruce–moss forest type on sandy loam or loamy sands site. Comerford and Fisher (1984) have shown that nor-mal tree growth may be impaired by nutrient imbal-may be degraded into an unproductive sheep laurel–
black spruce type of significantly lower site index if the ances. The high phenolic content of sheep laurel leaf and litter has been implicated as a soil depositional site is occupied by dense sheep laurel after forest
MALLIK: BLACK SPRUCE GROWTH AND SPECIES DIVERSITY WITH SHEEP LAUREL 97
and Mallik, 1996b; Northup et al., 1999), but the impor- from sheep laurel leaves. These authors have shown that genticic ando-hydroxyphenylacetic acid at 0.5 to tance of this process at this site may depend on further
5 mM concentrations, and the others at 1 to 5 mM
litter inputs over time. An invasion by sheep laurel
concentrations, can inhibit the primary root and shoot seems to more quickly bring about a reduction of
nutri-growth of black spruce (Mallik and Zhu, 1995). How-ents other than N, and at present, resource deficiency
ever, the involvement of these phenolic acids in the by a critical concentration of K (Swan, 1970) or
in-growth inhibition of larger black spruce seedlings under creased Fe, Al, and Mn toxicity may have created soil N
field conditions has not yet been studied. deficiency and nutrient imbalance (Inderjit and Mallik,
A reduced richness and diversity of vascular plants 1996b). This in turn may have created the growth
inhibi-was obtained in presence of sheep laurel compared with tory effect on black spruce.
the non-sheep laurel site. Habitat stress induced by the At the sheep laurel dominated sites of central
New-ericaceous plants may be suggested as a filtering mecha-foundland, field trials with spot fertilization of black
nism leading to heath formation where the species capa-spruce with three formulations of Gromax Transplant
ble of tolerating nutrient stress persist. The failure of Fertilizer (TPFS 4, 5, and Gromax Plus) at the time of
ground-level vascular species to invade sheep laurel planting produced a significant height increase of black
dominated sites allows cryptogams to occupy the soil spruce that lasted only for 2 yr (English, 1997, p. 10).
surface. It can be argued that the high diversity of stress After that, there was no significant difference in black
tolerant lichens at the sheep laurel dominated site is a spruce height between the fertilized and unfertilized
reflection of the stress condition of the habitat plants, and the author concluded that the
fertilizer-(Grime, 1977). treated seedlings were not able to capitalize on the initial
height growth boost to overcome the sheep laurel
ACKNOWLEDGMENTS growth inhibition. These results seem to suggest that
the black spruce growth inhibition phenomenon in the The work was supported by a research grant from the Natu-presence of sheep laurel is more than just a case of ral Science and Engineering Research Council (NSERC). I nutrient deficiency. thank Abitibi Consolidated, Grand Falls-Windsor for their logistical help during the field work and Robin Bloom and Results from the ericaceous litter amending
experi-Felix Eigenbrod for their help in data analyses. The comments ments of Inderjit and Mallik (1996a, 1997) showed that
of Dr. W.H. Carmean and two anonymous reviewers were sheep laurel and labrador tea litter can lower pH and
helpful in revising the manuscript. increase the total phenolic content of soil; these changes
can reduce the available N and P and increase Fe, Al,
REFERENCES
Ca, Mn, Zn, Cu, and Ba (Brady, 1990, p. 619). The
Appel, H.M. 1993. Phenolics in ecological interactions: The impor-authors attributed this soil nutrient imbalance to the
tance of oxidation. J. Chem. Ecol. 19:1521–1552. high phenolic content of the ericaceous litter because
Bending, G.D., and J.R. Read. 1996. Nitrogen mobilization from pro-phenolics are known to influence the availability, accu- tein–polyphenol complex by ericoid and ectomycorrhizal fungi. mulation, and uptake of nutrients (Rice, 1984; Appel, Soil Biol. Biochem. 28:1603–1612.
Brady, N.C. 1990. The nature and properties of soil. MacMillan Publ., 1993). The poor black spruce growth that was observed
New York. in the present study may have resulted from the adverse
Candy, R.H. 1951. Reproduction on cutover and burned over land effects of sheep laurel litter, causing allelopathy and in Canada. Silviculture Res. Note 92. Canada Dep. of Res. and nutrient imbalance. But this hypothesis must be tested Dev. Forest Res. Division, St. John’s, NF.
Comerford, N.B., and R.F. Fisher. 1984. Using foliar analysis to classify by further studies. Recent studies have shown that
phe-nitrogen-deficient sites. Soil Sci. Soc. Am. J. 48:910–913. nolic compounds in soil bind with organic N by forming
Damman, A.W.H. 1964. Some forest types of central Newfoundland phenol–protein complexes, and thus create soil N defi- and their relationship to environmental factors. For. Sci. Monogr. 8. ciencies in presence of ericaceous plants (Leak and Damman, A.W.H. 1971. Effects of vegetation changes on the fertility
of a Newfoundland forest site. Ecol. Monogr. 41:253–270. Read, 1989; Bending and Read, 1996).
Damman, A.W.H. 1975. Permanent changes in the chronosequence An alternative explanation of the poor growth of
of a boreal forest habitat. p. 499–515.InW. Schmidt (ed.) Sukessi-black spruce at the sheep laurel dominated site may be onsforschung Cramer. Vanduz, Germany.
due to the phenolic acids of the sheep laurel interfering de Montigny, L., and G.F. Weetman. 1990. The effects of ericaceous plants on forest productivity. p. 83–90.InB.D. Titus et al. (ed.) with the hormonal balance that is necessary for the
Inf. Report N-X-271. Canadian Forestry Serv., St. John’s, NF. normal growth of spruce (Zenk and Muller, 1963;
To-Einhellig, F.A. 1995. Mechanism of actions of allelochemicals in allelo-maszewski and Thimann, 1966). Zenk and Muller (1963) pathy. p. 96–116.InInderjit et al. (ed.) Allelopathy: Organisms, and Tomaszewski and Thimann (1966) showed that phe- processes, and applications. Am. Chem. Soc., Washington, DC.
English, B. 1997. Time-of-planting fertilization of black spruce on nolic acids in combination with high concentrations
Kalmiasites: Fourth year results. Silviculture Notebook 31. New-of metallic ions such as Mn can stimulate the
decarb-foundland Forest Serv. Silviculture and Res. Division, Corner oxylation of indoleacetic acid (IAA) and thus inhibit Brook.
plant growth. For example,p-hydroxybenzoic, vanillic, English, B., and R. Hackett. 1994. The impact ofKalmiaon plantation performance in central Newfoundland. Silviculture Notebook 2.
p-coumaric, syringic, and phloretic acid are known to
Newfoundland Forest Serv. Silviculture and Res. Division, Cor-reduce available IAA by promoting IAA
decarboxyl-ner Brook.
ation (Einhellig, 1995). Zhu and Mallik (1994) identified Fraser, L. 1993. The influence of salal on planted hemlock and cedar
p-hydroxybenzoic, genticic,o-hydroxyphenylacetic, va- saplings on northern Vancouver Island. M.S. thesis. Univ. of Br. Columbia Forest Sci. Dep., Vancouver.
Gimingham, C.H. 1972. Ecology of heathlands. Chapman & Hall, Meades, W.J., and L. Moores. 1994. Forest site classification manual: A field guide to the Damman forest types of Newfoundland. Forest London.
Grime, J.P. 1977. Evidence of the existence of three primary strategies Resource Dev. Agreement Rep. 003. Western Newfoundland Model Forest, Corner Brook.
in plants and its relevance to ecological and evolutionary theory.
Am. Nat. 111:1169–1194. Munson, A.D., and V.R. Timmer. 1989. Site-specific growth and nutri-tion of plantedPicea marianain the Ontario Clay Belt. I. Early Handley, W.R.C. 1963. Mycorrhizal associations andCalluna
heath-land afforestation. Bull. 36. Forestry Commission, London. performance. Can. J. For. Res. 19:162–170.
Newton, P.F. 1992. Base-age invariant polymorphic site index curves Inderjit, and A.U. Mallik. 1996a. Growth and physiological responses
of black spruce (Picea mariana) to sites dominated by Ledum for black spruce and balsam fir within central Newfoundland. Northern J. Appl. For. 9:18–22.
groenlandicum. J. Chem. Ecol. 22:575–585.
Inderjit, and A.U. Mallik. 1996b. The nature of interference potential Newton, P.F. 1998. An integrated approach to deriving site-specific black spruce regeneration standards by management objective. For. ofKalmia angustifolia. Can. J. For. Res. 26:1899–1904.
Inderjit, and A.U. Mallik. 1997. Effect of phenolic compounds on Ecol. Manage. 102:143–156.
Newton, P.F., and G.F. Weetman. 1993. Stand density management selected soil properties. For. Ecol. Manage. 92:11–18.
Ja¨derlund, A., O. Zackrisson, A. Dahlberg, and M.-C. Nilsson. 1997. diagram and their development and utility in black spruce manage-ment. For. Chron. 69:421–430.
Interference ofVaccinium myrtilluson establishment, growth, and
nutrition ofPicea abies in a northern boreal site. Can. J. For. Northup, R.R., R.A. Dahlgraen, T.M. Aide, and J.K. Zimerman. 1999. Effect of plant polyphenols on nutrient cycling and implications Res. 27:2017–2025.
Leak, J.R., and D.J. Read. 1989. The effects of phenolic compounds for community structure. p. 369–380.InPrinciples and practices in plant ecology: Allelochemical interactions. CRC Press, Washing-on nitrogen mobilizatiWashing-on by ericoid mycorrhizal system. Agric.
Ecosyst. Environ. 29:225–236. ton, DC.
Page, G. 1970. The development ofKalmia angustifolia on black LeBarron, R.K. 1948. Silvicultural management of black spruce in
Minnesota. Circular 791. USDA Forest Serv. Lake States Forest spruce cutover in central Newfoundland. Internal Rep. N-27. Forest Res. Lab., St John’s, NF, Canada.
Exp. Stn., Washington, DC.
Lowry, G.L., and P.M. Avard. 1968. Nutreant content of black spruce Rice, E.L. 1984. Allelopathy. Academic Press, Orlando, FL. Richardson, J., and J.P. Hall. 1973a. Natural regeneration after distur-needles. I. Variations with crown class and relationships to growth
and yield. Woodlands Paper 10. Pulp and Paper Res. Inst. of Can- bance in the forest of central Newfoundland. Inf. Rep. N-X-86. Canadian Dep. of Environ., Canadian Forestry Serv., St. John’s, NF. ada, Montreal, QC.
Mallik, A.U. 1987. Allelopathic potential ofKalmia angustifoliato Richardson, J., and J.P. Hall. 1973b. Natural regeneration after distur-bance in the forest of eastern Newfoundland. Inf. Rep. N-X-90. black spruce. For. Ecol. Manage. 20:43–51.
Mallik, A.U. 1990. Allelopathy and the competitive advantage of Canadian Dep. of Environ., Canadian Forestry Serv., St. John’s, NF. Swan, H.S.D. 1970. Relationships between nutrient supply, growth Kalmia angustifoliaover black spruce. p. 83–90.InB.D. Titus et al.
(ed.) Inf. Report N-X-271. Canadian Forestry Serv., St. John’s, NF. and nutrient concentrations in the foliage of black spruce and jack pine. Pulp Pap. Res. Inst. Can., Woodlands Pap. 19. 27p. Mallik, A.U. 1992. Possible role of allelopathy in growth inhibition
of softwood seedlings in Newfoundland. p. 321–341.InS.J.H. Rizvi Tomaszewski, M., and K.V. Thimann. 1966. Interactions of phenolic acids, metalic ions and chelating agents on auxin induced growth. and V. Rizvi (ed.) Allelopathy: basic and applied aspects. Chapman
and Hall, London. Plant Physiol. 41:1443–1454.
van Nostrand, R.S. 1971. Strip cutting black spruce in central New-Mallik, A.U. 1995. Conversion of temperate forests into heaths: Role
of ecosystem disturbance and ericaceous plants. Environ. Man- foundland to induce regeneration (Publication No. 1294). Natural Resources Canada, Canadian Forestry Serv., St. John’s, NF. age. 19:675–684.
Mallik, A.U. 1996. Competitive ability and allelopathy of ericaceous Wall, W.E., 1977. Ericaceous ground cover on cutover sites in south-western Nova Scotia. Inf. Rep. N-X-17. Canadian Dep. Fisheries plants as potential causes of conifer regeneration failures. J. Korean
For. Soc. 84:394–406. and Environ., Canadian Forestry Serv., Fredericton, NB. Yamasaki, S.H., J.W. Fyles, N.E. Egger, and B.D. Titus. 1998. The Mallik, A.U., and B.A. Roberts. 1994. Natural regeneration of red
pine on burned and unburned sites in Newfoundland. J. Veg. effect ofKalmia angustifoliaon growth, nutrition, and ectomycor-rhizal symbiont community of black spruce. For. Ecol. Manage. Sci. 5:179–186.
Mallik, A.U., and H. Zhu. 1995. Overcoming allelopathic growth 105:197–207.
Zenk, M.H., and G. Muller. 1963.In vivodestruction of exogenously inhibition by mycorrhizal inoculation. p. 39–57.InInderjit, K.M.
Dakshini and F.A. Einhellig (ed.) Allelopathy: Organisms, proc- applied indol-3-acetic acid as influenced by naturally occurring phenolic acids. Nature 200:761–763.
esses, and prospects. Am. Chem. Soc. Books, Washington, DC.
McCune, B., and M.J. Mefford. 1995. PC-ORD. Multivariate Analysis Zhu, H., and A.U. Mallik. 1994. Interactions betweenKalmiaand black spruce: Isolation and identification of allelopathic com-of Ecological Data. Version 2.0. MjM Scom-oftware Design, Gleneden
