Pinus Rigida Mill Research Articles

Crown conductance in dwarf, medium, and tall pitch pines in the Long Island Pine Plains

The New York Pine Plains are a unique ecosystem with normal statured and a dwarfed variety of pitch pines (Pinus rigida Mill.). Growing interspersed with the dwarf pines are trees of intermediate height and features. Several hypotheses have been put forward as to why some of the trees are dwarfed, but none have been substantiated. In this study, we tested whether dwarf or medium trees are hydraulically limited compared to normally growing trees. Granier style sap flux sensors were installed in three to six trees of each tree type and sap flux was measured in early August 2004. Sap flux measurements were scaled to crown stomatal conductance using leaf area to sapwood area ratios for each tree. Contrary to expectation, dwarf and medium stature trees had very low leaf area to sapwood area ratios, but high crown stomatal conductances compared to normal trees. Analyses of leaf area, ring widths, and crown stomatal conductance indicate that differences between normal, and dwarf and medium pines are not due to hydraulic limitation, but that stunted growth may be due to other causes.

Armillaria species distribution and site relationships in Pinus- and Tsuga-dominated forests in Massachusetts

The primary objective of this study was to determine the composition of Armillaria species in northeastern North American Pinus - and Tsuga -dominated forests. This was accomplished by sampling 32 plots at eight sites within pitch pine ( Pinus rigida Mill.), eastern white pine ( Pinus strobus L.), eastern white pine – mixed oak, and eastern hemlock ( Tsuga canadensis (L.) Carr.) forests. In total, 320 isolates were collected from 19 host tree species, with 207 of 320 (65%) of all isolations coming from Pinus and Tsuga. Armillaria solidipes Peck was the most abundant species, making up 188 of 320 (59%) of all isolations, which included 39 isolations from hardwoods. Meanwhile, Armillaria mellea (Vahl) P. Kumm. was collected a total of 27 times from eastern white and pitch pine. These two Armillaria species co-occurred at five of the eight sites sampled. Chi-square analyses showed that incidence of Armillaria species were significantly different by forest type. Pitch pine forests had a higher incidence of A. solidipes (p < 0.001), eastern white pine forests had a higher incidence of A. mellea (p = 0.001), and eastern hemlock forests had a higher incidence of Armillaria gallica Marxm. & Romagn. (p = 0.002) compared with expected values. The distribution of A. solidipes varied significantly by soil drainage and soil type, with a higher incidence on excessively drained (p < 0.001) and loamy sand (p < 0.001) soils.

Fine Root Dynamics in Thinned and Limed Pitch Pine and Japanese Larch Plantations

ABSTRACT To investigate fine root dynamics after thinning (50% of standing tree) and liming calcium magnesium carbonate[CaMg(CO3)2] 2 Mg ha− 1, a 2-year study was performed in 40-year-old pitch pine (Pinus rigida Mill.) and 44-year-old Japanese larch (Larix leptolepis Gord.) plantations in central Korea. Mean total fine root mass (kg ha− 1± SE) in the control, thinned, and limed plots were 1234 ± 32, 1346 ± 67, and 1134 ± 40 for the pitch pine plantation and 1655 ± 48, 1953 ± 58, and 1868 ± 70 for the Japanese larch plantation, respectively. Live fine root mass of pitch pine at 0-10 cm soil depth decreased after thinning and liming. In addition, liming significantly increased dead fine root mass of Japanese larch. Fine root production (kg ha− 1 yr− 1± SE) in the control, thinned and limed plots was 1108 ± 148, 2077 ± 262, and 1686 ± 103 for the pitch pine plantation and 1762 ± 103, 1886 ± 277, and 2176 ± 271 for the Japanese larch plantation, respectively. Fine root turnover rates increased after liming for both plantations. Fine root nitrogen (N) and phosphorus (P) concentrations of Japanese larch (1.012% of N and 0.073% of P) were higher than those of pitch pine (0.809% of N and 0.046% of P) in the control. Also N and P inputs into soil through fine root turnover increased after treatments. Results indicated that comparing fine root dynamics among forest types and after forest management practices might influence differences in soil fertility and underground nutrient cycling.

Genetic variation among pitch pine Pinus rigida families from Walden Woods: Heritability and path analysis of developmental variation of phenotypic traits

The growth and development of plants is determined by both genetic and environmental factors. In this study, path analysis was employed to investigate the magnitude of developmental variation among six quantitative characters associated with growth in 29 pitch pine (Pinus rigida Mill.) families at Walden Woods, Lincoln, Mass. Seedlings were grown for six months in two environments: sand (poor) and sandy loam (better) with four replications under greenhouse conditions. Data were recorded on stem height and weight, crown height and weight, and total height and weight. Data were analyzed using analysis of variance, heritability, and path analysis. Path analysis measures both direct and indirect effects of independent variables on dependent variables through intermediary variables. Hence, it is a powerful approach for evaluating the causal flow of physiological variables among a system of morphological characters during growth and development. Within this single population of pitch pines, significant genotype-environment interaction was found for most characters. Heritability for four characters was greater for families raised in sand than in sandy loam. Path analysis suggested that the physiological resources may be channeled differentially among various quantitative characters in relation to their environments, indicating that the environment modulates not only the development of individual phenotypic traits but also the relationships among these traits in the entire organism. Moreover we found that environmental effects may overwhelm the genetic expression of a given quantitative trait. Knowledge of relative flexibility/plasticity of individual characters in relation to specific environmental resources may be useful toward understanding developmental biology, growth, and reproduction in plants.

Short‐term effects of thinning and liming on forest soils of pitch pine and Japanese larch plantations in central Korea

AbstractThe influences of thinning (50% of standing density) and liming (Ca+Mg, 2 Mg ha−1) on soil chemical properties were investigated for 2 years (2001, 2002) in 40‐year‐old pitch pine (Pinus rigida Mill.) and 44‐year‐old Japanese larch (Larix leptolepis Gord.) plantations established on similar soils. In general, soil properties varied significantly among plantations and treatments. For both plantations, thinning significantly increased soil organic C (SOC) concentrations whereas there were no significant changes in soil pH and Ca and Mg concentrations. In addition, thinning increased total soil N and Na concentrations for the pitch pine plantation and available P concentration for the Japanese larch plantation in the second year after the treatment. Liming did not affect soil chemical characteristics for the pitch pine plantation except for Na concentration. However, for the Japanese larch plantation, liming significantly increased soil pH and K, Ca and Mg concentrations and decreased SOC and total soil N concentrations. For both plantations, soil Al concentration did not change after thinning and liming and decreased exponentially with increased pH values. The increases in SOC and total soil N concentrations after thinning were possibly due to increases in decomposition of organic matter and root death. Although differences were not statistically significant, soil available P concentration tended to increase at early stages of liming for both plantations. These results suggested that thinning and liming seemed to regulate soil chemical properties for pitch pine and Japanese larch plantations established on similar soils.

Effects of flooding on pitch pine (Pinus rigida Mill.) growth and survivorship1

Craine S. I. and Orians C. M. (Tufts University, Medford, Mass.). Effects of flooding on pitch pine (Pinus rigida Mill.) growth and survivorship. J. Torrey Bot. Soc. 133(2): 289–296. 2006.—Pitch pines (Pinus rigida Mill.) colonize the shores of Cape Cod coastal plain ponds in periods of low water and, once established, inhibit the growth of resident herbaceous species, including rare endemics. The effects of flooding on P. rigida may vary with plant age and may be affected by previous exposure to flooded conditions. To determine the effects of flooding on pitch pine survivorship, we performed three sets of experiments. First, we examined the effects of relative flood depth—root flooding versus total submersion—on three-month-old seedlings. Second, we determined whether prior exposure to root flooding enhanced subsequent survivorship in flooded conditions one year later. Lastly, we compared the effects of root flooding on pines of different ages—three months, 15 months, and five years. We found that three-month-old P. rigida succumbed to total submersion in two to four weeks but tolerated root flooding for up to one year. Fifteen-month-old seedlings that had survived eight weeks of root flooding one year earlier were significantly more flood-tolerant than members of the same cohort that had never been flooded. Fifteen-month-old seedlings, as well as five-year-old saplings, suffered significantly more mortality after four months of root flooding than did three-month-old seedlings. The ability of young P. rigida, normally an upland plant, to survive in waterlogged soil appears to be due, in part, to morphologic modifications acquired in response to flooded conditions, including hypertrophy of lenticels on the stem and plagiotropism. Both these acquired modifications are known to help oxygenate root tissues through internal channels, avoiding cellular anoxia despite reduced oxygen availability in the rhizosphere. Overall, our results suggest that periodic flooding has historically played a role in preventing the colonization of P. rigida on coastal plain pond shores and that reduced flooding intensity may lead to more frequent encroachment of P. rigida in this habitat.

Introduction of Canadian tree species to the Northeast of China

This paper describes the early results of the introduction of some Canadian tree species to Liaoning Province in Northeast China. Based on earlier trial results from the 1920s and testing over the last 20 years, some of the introduced conifers show strong adaptation to the new ecological and climatic conditions with normal flowering and fruiting, excellent growth rates, and resistance to local pests. Of the seventeen introduced species tested, eastern white pine (Pinus strobus L.), jack pine (Pinus banksiana Lamb.), and pitch pine (Pinus rigida Mill.), show the most promising results as compared to indigenous pine species (i.e., Pinus tabulaeformis Carr., P. koraiensis Sieb. et Zucc., and P. sylvestris var. mongolica Litv.). These findings have resulted in the implementation of large-scale planting programs of jack pine in the current five-year plan of the provincial forestry authority. In parallel with the seed source trials, seed production areas have been established by selecting promising sources and species for developing local landraces for future seed production. The application of this successful cooperation will not only increase the forest cover of Liaoning from the current 31% to 35%, improving the environment and wood supply, but also serve as a model for the region as well as for other jurisdictions. Key words: species introduction, seed source, ecological adaptability, landrace, seed production areas

Cumulative Forage Production, Forage Quality and Livestock Performance from an Annual Ryegrass and Cereal Rye Mixture in a Pine Walnut Silvopasture

Annual ryegrass (Lolium multiflorum Lam.) and cereal rye (Secale cereale L.) pastures can extend the grazing season in the lower Midwest. There is little data from this region on the productivity of these forages in a silvopasture system. Our objective was to determine the forage and livestock production from annual ryegrass/cereal rye in a silvopasture versus an open (non-forested) system. This study was conducted near New Franklin, MO, USA. The treatments were (1) annual ryegrass/cereal rye planted into a 6- to 7-year-old stand of pitch pine (Pinus rigida Mill.) × loblolly pine (Pinus taeda L.) hybrids and black walnut (Juglans nigra L.) (TREE treatment) and (2) the same forages planted into pastures without trees (OPEN treatment). Marshall annual ryegrass and cereal rye were no-till seeded at 22 and 67 kg ha-1 of pure live seed, respectively, on 18 September 2000 and 30 August 2001. Treatments were replicated three times in a randomized complete block. In March 2001 and 2002, three beef heifers were assigned to each pasture and rotationally grazed until early June. Cumulative forage production and quality were measured for each treatment. Cumulative forage production in the TREE treatment was reduced by approximately 20% compared to the OPEN treatment. However, beef heifer average daily gain and gain ha-1 were equal for both treatments. Beef producers using a annual ryegrass/cereal rye in a silvopasture system likely would not sacrifice livestock production when hybrid pine and black walnut trees are 6- to 7-year-old when compared to an open pasture.

Influence of Meso- and Microscale Habitat Structure on Focal Distribution of Sympatric <I>Ixodes scapularis</I> and <I>Amblyomma americanum</I> (Acari: Ixodidae)

We compared the distribution of sympatric Ixodes scapularis Say and Amblyomma americanum (L.) within several suitable forested habitats at different spatial scales and characterized differences in microhabitat features accounting for the observed distribution of questing ticks. We used automatic data loggers placed in the shrub and litter layers to contrast mesoclimate and microclimate conditions experienced by questing ticks. Larger numbers of I. scapularis were collected at sites where the forest canopy was more fragmented and where the canopy contained more hardwood species than pitch pine, Pinus rigida Mill. Dominance of pine in the canopy affected the character of the shrub layer vegetation and composition of the litter layer, which concomitantly affected the microclimate conditions experienced by questing ticks. Pitch pine-dominated habitats were drier and hotter than those under a broad-leaved canopy, and questing ticks experienced increased saturation deficit in the later spring and summer in pine forest sites. The shrub layer vegetation seemed to have a moderating effect on the microclimate experienced by questing ticks and subtle differences in vegetation structure resulted in substantially different conditions as encountered by questing ticks over the space of a few meters. In contrast to questing I. scapularis, all three stages of questing A. americanum exhibited poor relationships with microclimate variables recorded in the litter and shrub layers. Further research is required to determine which environmental conditions and which habitats are most likely to support this species.

Influence of Meso- and Microscale Habitat Structure on Focal Distribution of SympatricIxodes scapularisandAmblyomma americanum(Acari: Ixodidae)

We compared the distribution of sympatric Ixodes scapularis Say and Amblyomma americanum (L.) within several suitable forested habitats at different spatial scales and characterized differences in microhabitat features accounting for the observed distribution of questing ticks. We used automatic data loggers placed in the shrub and litter layers to contrast mesoclimate and microclimate conditions experienced by questing ticks. Larger numbers of I. scapularis were collected at sites where the forest canopy was more fragmented and where the canopy contained more hardwood species than pitch pine, Pinus rigida Mill. Dominance of pine in the canopy affected the character of the shrub layer vegetation and composition of the litter layer, which concomitantly affected the microclimate conditions experienced by questing ticks. Pitch pine-dominated habitats were drier and hotter than those under a broad-leaved canopy, and questing ticks experienced increased saturation deficit in the later spring and summer in pine forest sites. The shrub layer vegetation seemed to have a moderating effect on the microclimate experienced by questing ticks and subtle differences in vegetation structure resulted in substantially different conditions as encountered by questing ticks over the space of a few meters. In contrast to questing I. scapularis, all three stages of questing A. americanum exhibited poor relationships with microclimate variables recorded in the litter and shrub layers. Further research is required to determine which environmental conditions and which habitats are most likely to support this species.

Root environmental effects on phi thickening production and root morphology in three gymnosperms

Phi thickenings, lignified thickenings found on the radial and tangential walls of root cortical cells, are present in a restricted number of angiosperms and gymnosperms. To test whether their occurrence is constitutive or environmentally induced, seedlings of Cryptomeria japonica (L.f.) D. Don (Cupressaceae, phi thickenings present), and Pinus aristata Engel. and Pinus rigida Mill. (Pinaceae, phi thickenings absent) were grown under conditions of waterlogging and soil compaction. After 4 months, five morphological characters and the presence and cross-sectional area of phi thickenings were measured. All measured aspects of seedling morphology were affected by the treatments, and the two treatment factors (waterlogging and compaction) interacted significantly with one another. Taproots were significantly shorter, lateral roots were shorter and fewer in number, and root:shoot ratios were smaller in waterlogged and compacted soil in all three species. Despite these morphological effects, phi thickening presence or absence did not vary: phi thickenings were always found in C. japonica and never in the two Pinus species. However, the phi ratio (the area occupied by phi thickenings relative to the total root area) decreased significantly with both waterlogging and compaction even though it remained unchanged with root maturity. Thus, although root morphology and phi thickening anatomy were significantly affected by the environment, the presence of phi thickenings was not, and is evidently a constitutive anatomical feature in the species examined.Key words: phi thickenings, root anatomy, Cryptomeria, Pinus, waterlogging, soil compaction.

Influence of seedbed, light environment, and elevated night temperature on growth and carbon allocation in pitch pine ( Pinus rigida) and jack pine ( Pinus banksiana) seedlings

Jack pine ( Pinus banksiana Lamb.) and pitch pine ( Pinus rigida Mill.) are two autecologically similar species that occupy generally disjunct ranges in eastern North America. Jack pine is boreal in distribution, while pitch pine occurs at temperate latitudes. The two species co-occur in a small number of stands along a ‘tension-zone’ that traverses central Maine. These populations provide an opportunity for studying differences between boreal and temperate species in their adaptation to climatic factors. As seedling establishment and early growth are key life-stages governing tree distribution, we experimentally evaluated the influence of seedbed light environment and substrate on the success and early growth of these species. Under similar environments, first-year jack pine seedlings allocated relatively more biomass to roots and pitch pine more to foliage. This might provide pitch pine with an adaptive advantage when soil moisture was not limiting and an advantage to jack pine if substantial moisture stress occurred. Complex ontogenetic shifts in these allocation patterns occurred over second and third years of growth, which resulted in an equalization of interspecific differences in shoot–root ratios by the end of the third growing season. Night temperatures of 4–5 °C above ambient reduced growth of jack pine seedlings, while that of pitch pine was unaffected. However, foliar respiration and respiratory response to temperature were not significantly different between species and did not explain observed differences in temperature response.

A Multiscale Landscape Approach to Predicting Bird and Moth Rarity Hotspots in a Threatened Pitch Pine–Scrub Oak Community

Abstract: In the northeastern United States, pitch pine ( Pinus rigida Mill.)–scrub oak (Quercus ilicifolia Wang.) communities are increasingly threatened by development and fire suppression, and prioritization of these habitats for conservation is of critical importance. As a basis for local conservation planning in a pitch pine–scrub oak community in southeastern Massachusetts, we developed logistic‐regression models based on multiscale landscape and patch variables to predict hotspots of rare and declining bird and moth species. We compared predicted moth distributions with observed species‐occurrence records to validate the models. We then quantified the amount of overlap between hotspots to assess the utility of rare birds and moths as indicator taxa. Species representation in hotspots and the current level of hotspot protection were also assessed. Predictive models included variables at all measured scales and resulted in average correct classification rates (optimal cut point) of 85.6% and 89.2% for bird and moth models, respectively. The majority of moth occurrence records were within 100 m of predicted habitat. Only 13% of all bird hotspots and 10% of all moth hotspots overlapped, and only a few small patches in and around Myles Standish State Forest were predicted to be hotspots for both taxa. There was no correlation between the bird and moth species‐richness maps across all levels of richness (r =−0.03, p = 0.62). Species representation in hotspots was high, but most hotspots had limited or no protection. Given the lack of correspondence between bird and moth hotspots, our results suggest that use of species‐richness indicators for conservation planning may be ineffective at local scales. Based on these results, we suggest that local‐level conservation planning in pitch pine–scrub oak communities be based on multitaxa, multiscale approaches.

Spatial variability in soil nutrient availability in an oak-pine forest: potential effects of tree species

Established species have been shown to affect soil nutrient availability, but the effects of "native invasive" species on soil nutrient availability are relatively unknown. Oak-dominated forests in the eastern deciduous forest are dynamic in their species composition, with increasing dominance of red maple (Acer rubrum L.) in the midstory and overstory. We hypothesized that higher quality red maple litter within a litter matrix dominated by oaks would accelerate N turnover, increase nutrient availability in the soil, and result in a thinner and less massive O horizon. We examined nutrient availability in soils under three overstory tree species (Quercus prinus L., A. rubrum, and Pinus echinata Mill. or Pinus rigida Mill.), under a shrub (Vaccinium spp.), and in locations without tree stems ("no tree"). Ex tract able nutrients (P, K, Mg, Ca) and total and available N were quantified in the O horizon and upper mineral soil at 0.5 m and 1.0 m from the base of individual trees or from the center of Vaccinium and no-tree locations. Despite low lignin concentration in red maple litter and low lignin/N ratio, the lowest N mineralization rates were found in red maple microsites; the highest N mineralization rates were found under oak. Extractable cations were generally highest under red maple and lowest under pines, and red maple had the highest levels of total N (but not NO3or NH4) in the upper mineral soil. Shifting species composition towards red maple and away from pines in these forests may alter nutrient cycling by increasing surface soil cation availability, but reducing soil N mineralization.

Conceptual ecological models for the Long Island pitch pine barrens: implications for managing rare plant communities

Fire dependent pitch pine ( Pinus rigida Mill.) and scrub oak ( Quercus ilicifolia Wang.) barrens are found on coarse-textured, droughty soils in the northeastern United States. These communities are globablly rare and, in many areas, dependent on active management to sustain them. We used historic and recent aerial photographs of the Central Pine Barrens in New York to develop transition matrices and trajectories of vegetation change. A vegetation map for 1990 provided pre-burn cover type information for a 1,200 ha area burned by an extremely severe wildfire in August 1995. Geographic information system analyses, a fire-history study, post-wildfire research and existing literature provided additional information for development of three conceptual models that describe our understanding of vegetation change in response to fire and land clearing. A simulation model was then used to predict the amount of each cover type in 2046. The reasonableness of the prediction was assessed based on our understanding of pine barrens vegetation dynamics. In 1938, following a period of frequent, intense wildfires of the region, 90% of vegetation in the study area was open canopy barrens (including dwarf pine plains, pitch pine–scrub oak woodland, heath, pine–heath woodland, and scrub oak shrubland). Between 1938 and 1994, wildfires decreased in size, the average area burned per year generally declined, and there were no fires in 70% of the study area. As a result, barrens decreased to ∼45% of study area vegetation. In August 1995, an unusually severe summer wildfire converted 810 ha of woodland and forest into scrub oak shrubland, and increased barrens to 60% of study area vegetation. Most areas of heath and pine–heath, which comprised 24% of barrens vegetation in 1996, are successional types that developed on formerly cleared land. In the absence of extensive burning, we expect barrens vegetation to be converted to closed-canopy forest as coppice trees and new seedlings mature. Recent changes in fire regimes are likely to result in a loss of barrens vegetation that exceeds predictions of the simulation model. Careful use of prescribed fire and/or mechanical treatments to simulate the effects of fire are recommended for future restoration and maintenance of pitch pine barrens, and for protection of human life and property.

Pitch pine ( Pinus rigida Mill.) invasion of Cape Cod pond shores alters abiotic environment and inhibits indigenous herbaceous species

Invasion by pitch pine ( Pinus rigida Mill.) on coastal plain pond shores may have direct impacts on the herbaceous community, or may merely indicate changes in hydroperiod, which are the actual cause of community change. We compared abiotic conditions and community composition of sites that had been invaded by P. rigida and those that had not on two Cape Cod ponds. Soil under living pines had lower pH and water content, reduced net nitrification, and increased rates of ammonification. Dense stands of pine saplings reduced PAR penetrance by 94% and excluded virtually all herbaceous species. To determine if pines alone can change community composition, we imposed artificial shade and added pine needle litter to experimental plots. In the course of one growing season, both litter and shade significantly reduced the frequency of herbs in the herbaceous zone of the pond shore. Litter had the greater effect (significant for six of seven taxa), while shade reduced the frequencies of three taxa significantly.

Contrasting modes of survival by jack and pitch pine at a common range limit

Freezing tolerance, reproductive development, and seed germination of jack pine (Pinus banksiana Lamb.) and pitch pine (Pinus rigida Mill.) were compared in a small sympatric population in Acadia National Park in Maine, at the southern range limit of the former and the northern limit of the latter. Freezing tolerances of vegetative shoots and roots were similar for both species. Both species flower prolifically, and there was no evidence of differences in either pollen viability, cone survival, or proportion of viable seed (65–70% of the total). Regeneration success (established seedlings ranging from 1 to 13 years old) was similar overall for both species, but success by species varied greatly in some years. Jack pine regeneration was significantly associated with thinner soils, while pitch pine regeneration was associated with thicker soils in hollows. Jack pine seed germinated significantly faster than pitch pine seed, especially when day–night temperature was reduced. Pitch pine seedlings always exhibited a significantly higher shoot/root ratio than those of jack pine. The most northerly provenances of jack pine germinated significantly faster than those from the most southerly provenances. Jack pine also germinated at a significantly higher percentage than pitch pine in exposed granite sand. Thus relatively cool, dry conditions may favor establishment of jack pine seedlings, while pitch pine establishment may be favored in warmer, wetter conditions.

Effect of water stress on aluminum toxicity in pitch pine seedlings

A decrease in soil water content during droughts may increase aluminum (Al) to concentrations that are toxic to the growth of trees. The effects of water stress (WS) on the response of ectomycorrhizal pitch pine (Pinus rigida Mill.) seedlings to aluminum was determined by growing seedlings in sand irrigated with nutrient solution (pH 3.8) containing 0, 5, or 10 mg L‐1 Al. Water stress was imposed for 41 days by withholding nutrient solution for five consecutive days each week. At harvest time, seedlings at high WS had 72% of mean gravimetric water contents of seedlings at low WS. Aluminum decreased growth of seedlings at high WS, but had no effect on growth of seedlings at low WS. Aluminum toxicity symptoms in roots (e.g., dark thickened tips) were observed at lower Al levels at high WS than at low WS. Stem dry weight was the only plant part decreased by water stress alone. Across Al levels, Al concentration in roots was higher at low WS than at high WS. Water stress alone reduced root [phosphorus (P), potassium (K), and calcium (Ca)] and foliar [P, K, and magnesium (Mg)] concentrations of mineral nutrients. Decreases of nutrients in roots with increasing Al was greater at low than at high WS. Calcium was the only foliar nutrient decreased by Al treatment.

Nitrogen and phosphorus dynamics in foliage and twig of pitch pine and Japanese larch plantations in relation to fertilization

Seasonal foliage and twig nitrogen (N) and phosphorus (P) dynamics were determined for 40‐year‐old pitch pine (Pinus rigida Mill.) and Japanese larch (Larix leptolepis Gord.) plantations established on similar soils in central Korea. Also, the effects of three levels of N plus P fertilizers on N and P retranslocation were evaluated. In general, Japanese larch had significantly higher current foliage N and P concentrations than pitch pine, and N and P concentrations were higher in foliage than those in twigs for both study species. Foliage N and P concentrations were highest in mid‐growing season and lowest in autumn whereas twig N and P concentrations increased during foliage senescence, suggesting that twig served as a storage tissue. We did not find differences in foliage N and P retranslocation between pitch pine and Japanese larch; current foliage N and P retranslocation of the control trees were 35% and 56% for pitch pine, and 39% and 59% for Japanese larch, respectively. There were no consistent patterns in foliage and twig N and P retranslocation following fertilization.

Changes in radial increment of host and nonhost tree species with gypsy moth defoliation

Ring widths from 1458 trees from Massachusetts, New York, and New Jersey were measured to determine the influence of gypsy moth (Lymantria dispar L.) defoliation on both hosts (primarily oaks (Quercus spp.)) and nonhosts. Previous year's defoliation negatively influenced radial increment in all oak species. Defoliation also negatively affected radial growth of pitch pine (Pinus rigida Mill.), an intermediate host. There was little or no effect of defoliation on increment of trembling aspen (Populus tremuloides Michx.) and bigtooth aspen (Populus grandidentata Michx.), but both are preferred hosts. Defoliation of host trees in mixed stands resulted in increased increment in the nonhosts tulip-tree (Liriodendron tulipifera L.) and ash (Fraxinus spp.) in the year following defoliation. The effect of defoliation was also evident in the relative production of earlywood and latewood with a pronounced dominance of earlywood production in host trees during the same year as defoliation and often in the following year.