Sugar Maple Seedlings Research Articles

Test of soil extractants for their suitability in predicting Ca/Sr ratios in leaves and stems of sugar maple seedlings

Differential uptake and translocation of Ca and Sr in organisms have been reported, calling into question the use of Sr to track Ca cycling in the environment. We investigated the relationship between Ca/Sr ratios in soil extracts of various strengths (H2O, NH4Cl, and NH4EDTA) and seedlings of sugar maple (Acer saccharum Marsh.) grown from natural regeneration on 37 sites. Our objectives were to determine if Ca/Sr ratios in soil extracts are correlated with those in sugar maple tissues, and what soil extractant best duplicate plant tissue Ca/Sr ratios. Leaves had higher Ca/Sr ratios than stems and the extractants did not produce equal Ca/Sr ratios: H2O had the lowest Ca/Sr, and NH4EDTA the highest. The relationships between soil extract Ca/Sr ratios and leaf and stem Ca/Sr ratios were significant and linear, but the slopes differed among extractants. The lowest slope (0.45) was observed for the water extract/leaves and the highest (2.15) for the NH4EDTA extract/stem with discrimination factors ranging from 0.22 with NH4EDTA to 1.59 for water. Leaf extracts were more strongly correlated with soil Ca/Sr than stem extracts (R2 of 0.57–0.7 vs. R2 of 0.45–0.6, respectively). These findings support the use of Ca/Sr ratios in plants to track their source of soil Ca, but they highlight the need to calibrate the relationships for the plant tissue and soil extractant used.

Effects of Earthworm Invasion on Plant Species Richness in Northern Hardwood Forests

The invasion of non-native earthworms (Lumbricus spp.) into a small number of intensively studied stands of northern hardwood forest has been linked to declines in plant diversity and the local extirpation of one threatened species. It is unknown, however, whether these changes have occurred across larger regions of hardwood forests, which plant species are most vulnerable, or with which earthworm species such changes are associated most closely. To address these issues we conducted a regional survey in the Chippewa and Chequamegon national forests in Minnesota and Wisconsin (U.S.A.), respectively. We sampled earthworms, soils, and vegetation, examined deer browse in 20 mature, sugar-maple-dominated forest stands in each national forest, and analyzed the relationship between invasive earthworms and vascular plant species richness and composition. Invasion by Lumbricus was a strong indicator of reduced plant richness in both national forests. The mass of Lumbricus juveniles was significantly and negatively related to plant-species richness in both forests. In addition, Lumbricus was a significant factor affecting plant richness in a full model that included multiple variables. In the Chequamegon National Forest earthworm mass was associated with higher sedge cover and lower cover of sugar maple seedlings and several forb species. The trends were similar but not as pronounced in Chippewa, perhaps due to lower deer densities and different earthworm species composition. Our results provide regional evidence that invasion by Lumbricus species may be an important mechanism in reduced plant-species richness and changes in plant communities in mature forests dominated by sugar maples.

Compost-Containing Substrates and Their Effect on Posttransplant Growth of Containerized Tree Seedlings

Greenhouse studies were undertaken to determine the influence of composted media on the posttransplant growth of containerized red maple, sugar maple, and green ash seedlings. Before planting, the chemical and physical properties of each substrate were measured. For media containing composted biosolids, pH was significantly higher, whereas electrical conductivity, air-filled porosity, and total pore space were significantly lower than in a composted medium without biosolids. For composted substrates containing at least some soil, bulk density, particle density, and container capacity were all significantly greater than for composts without any soil. Growth of red maple was about the same in a noncomposted soilless medium (Metro-mix 360) as it was in substrates containing biosolid compost. Height growth, total biomass, and root biomass of green ash were all significantly greater for seedlings grown in Metro-mix 360 only, and the growth of sugar maple seedlings was about the same in Metro-mix 360 or in a composted substrate without biosolids (Metro-mix 560). The results of this study suggest no particular short-term growth advantage of using composted media as backfill amendments when transplanting; however, the addition of composts could be beneficial in improving the chemical and physical properties of native soils, particularly urban soils containing very low levels of organic matter.

Responses of secondary chemicals in sugar maple (Acer saccharum) seedlings to UV-B, springtime warming and nitrogen additions

Anticipated effects of climate change involve complex interactions in the field. To assess the effects of springtime warming, ambient ultraviolet-B radiation (UV-B) and nitrogen fertilization on the foliar chemistry and herbivore activity of native sugar maple (Acer saccharum Marsh.) seedlings, we carried out a field experiment for 2 years at two sugar maple forests growing on soils of contrasting acidity. At the Oliver site, soils are derived from a strongly calcareous till, whereas the naturally acidic soils and base-poor soils of the Haliburton site are derived from the largely granitic Precambrian Shield. At both sites, removal of ambient UV-B led to increases in chlorogenic acid and some flavonoids and reduced herbivore activity. At Haliburton, ammonium nitrate fertilization led to further increases in foliar manganese (Mn), whereas at Oliver there were no such changes. Nitrogen additions led to decreases in the concentrations of some flavonoids at both sites, but seedlings at Oliver had significantly higher concentrations of flavonoids and chlorogenic acid than seedlings at Haliburton. We suggest that this could be associated with increased mobilization of Mn due to increased soil acidity, which interferes with the role of calcium (Ca) in the phenolic biosynthetic pathway. It appears that the composition of the forest soil governs the response of seedlings when they are exposed to abiotic stressors.

Control of Hay-Scented Fern by Mowing

Abstract Hay-scented fern (Dennstaedtia punctilobula) is a native species that can invade and dominate the forest understory, after thinning and intensive deer browsing. Fern colonies form a dense cover 60 to 80 cm high that intercepts light and inhibits tree seedling regeneration. Hay-scented fern can be controlled with herbicides, but some landowners (both public and private) seek alternative methods. We investigated mowing as a possible method of fern control. We tested different mowing schedules and measured the response of ferns (frond length and density) and of natural regeneration and planted seedlings. Mowing the ferns twice in one growing season (first in June when the fern fronds had reached their full height and again in August) led to a significant reduction in frond length during the next two growing seasons compared to untreated controls. Mowing four times over 2 years reduced both length and density of ferns. Mean density of naturally established tree seedlings was four times greater on these treatment plots compared to controls, but with great variability among plots. Red oak (Quercus rubra) and sugar maple (Acer saccharum) seedlings planted the year after mowing showed greater survival and height growth compared to controls.

RESPONSE OF SUGAR MAPLE TO CALCIUM ADDITION TO NORTHERN HARDWOOD FOREST

Watershed budget studies at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, have demonstrated high calcium depletion of soil during the 20th century due, in part, to acid deposition. Over the past 25 years, tree growth (especially for sugar maple) has declined on the experimental watersheds at the HBEF. In October 1999, 0.85 Mg Ca/ha was added to Watershed 1 (W1) at the HBEF in the form of wollastonite (CaSiO3), a treatment that, by summer 2002, had raised the pH in the Oie horizon from 3.8 to 5.0 and, in the Oa horizon, from 3.9 to 4.2. We measured the response of sugar maple to the calcium fertilization treatment on W1. Foliar calcium concentration of canopy sugar maples in W1 increased markedly beginning the second year after treatment, and foliar manganese declined in years four and five. By 2005, the crown condition of sugar maple was much healthier in the treated watershed as compared with the untreated reference watershed (W6). Following high seed production in 2000 and 2002, the density of sugar maple seedlings increased significantly on W1 in comparison with W6 in 2001 and 2003. Survivorship of the 2003 cohort through July 2005 was much higher on W1 (36.6%) than W6 (10.2%). In 2003, sugar maple germinants on W1 were approximately 50% larger than those in reference plots, and foliar chlorophyll concentrations were significantly greater (0.27 g/m2 vs. 0.23 g/m2 leaf area). Foliage and fine-root calcium concentrations were roughly twice as high, and manganese concentrations twice as low in the treated than the reference seedlings in 2003 and 2004. Mycorrhizal colonization of seedlings was also much greater in the treated (22.4% of root length) than the reference sites (4.4%). A similar, though less dramatic, difference was observed for mycorrhizal colonization of mature sugar maples (56% vs. 35%). These results reinforce and extend other regional observations that sugar maple decline in the northeastern United States and southern Canada is caused in part by anthropogenic effects on soil calcium status, but the causal interactions among inorganic nutrition, physiological stress, mycorrhizal colonization, and seedling growth and health remain to be established.

Spatial patterns of plant species richness along a forest edge: What are their determinants?

The impact of forest edges on plant species richness is poorly understood. In a sugar maple ( Acer saccharum) stand in Southern Québec, variations in species richness and spatial pattern were observed as a function of distance to the edge and were associated with different environmental variables. Unexpectedly, light was not higher and soil moisture and organic matter were not lower close to the edge than in the forest interior: edge structure was most likely responsible for these results. At a 2 m 2 scale, richness tended to decrease with distance to the edge, as did fine-scale species turn-over. Erythronium americanum patch size increased with distance to the edge, most likely because of differences in clonal growth along the gradient. Cover of newly emerged seedlings of sugar maple decreased with distance to the edge, in association with soil moisture and pH. Path analyses revealed significant links between environmental (micro-elevation, irradiance, soil organic matter, moisture, and pH) and biotic variables (richness, E. americanum cover, and A. saccharum cover), but only a low proportion of the variance of the biotic variables was explained. At the scale studied, stochastic processes may be more significant than deterministic processes for species richness.

Response of Acer saccharum seedlings to elevated O3 and CO2 concentrations

The effects of three times ambient [O3] (3x) and high [CO2] (650 µL L-1 CO2) alone and in combination were studied on 2-yr-old sugar maple (Acer saccharum) seedlings for 86 days in open top chambers. Sugar maple net CO2 assimilation rate and growth were not decreased by the O3 treatment after one growing season, and the epicuticular wax was not damaged compared with the control. The absence of response to the O3 treatment is attributable to the low stomatal conductance of this species resulting in a low O3 uptake, together with the succession of periods of high and low [O3], which allowed the seedlings to alleviate the oxidative stress. At the end of August, under high [CO2], the growth of the seedlings and net CO2 assimilation to stomatal conductance to CO2 ratio in the second flush of leaves had doubled. Under the environmental growth conditions of the chambers (high light, nutrients and water availabilities), the seedlings may benefit from the availability of CO2. Sugar maple seedlings may have a competitive growth advantage under elevated CO2 conditions and three times ambient [O3] did not decreased the fertilizing effect of CO2.

The effects of UV-B, nitrogen fertilization, and springtime warming on sugar maple seedlings and the soil chemistry of two central Ontario forests

The interactive effects of springtime warming, ambient UV-B, and nitrogen fertilization on the chemistry of sugar maple (Acer saccharum Marsh.) seedlings and soils from two contrasting sites were assessed. Open-top chambers increased average springtime air temperatures by approximately 1.5 °C, but their heating effect was diminished upon closure of the overstory canopy. Ambient levels of UV-B were reduced with Mylar D polyester film. Ammonium nitrate fertilizer was added in an amount equivalent to an additional 50 kg N·ha–1. The soils of the Oliver forest were deep luvisols overlying a strongly calcareous till (average pH 6.0), while the naturally acidic soils of Haliburton were derived from the Precambrian Shield (average pH 4.7). Of the three main treatments used in this study, application of nitrogen fertilizer had the greatest impacts on foliar chemistry. At both sites, fertilizer application increased the acidity of the soils, while at Haliburton there were losses in total soil calcium. Haliburton maple seedlings had increased foliar concentrations of aluminum and manganese, decreased concentrations of calcium, and reduced calcium/manganese and magnesium/manganese nutrient ratios, after fertilizer was applied. Meanwhile, seedlings growing on the more alkaline soils of Oliver had increased foliar concentrations of magnesium following application of the nitrogen fertilizer. We suggest that these changes in the elemental chemistry of the soils and foliage brought on by continued nitrogen loading may predispose seedlings growing on naturally acidic soils, such as those of the Precambrian Shield, to further stress from additional abiotic and biotic stressors.

The Effects of AlCl3Additions on Rhizosphere Soil and Fine Root Chemistry of Sugar Maple (Acer Saccharum)

Increased Al mobilization and Ca and Mg leaching have been linked to nutritional imbalances in sugar maple across the northeastern US and Canada. The susceptibility of sugar maple fine roots to Al stress is poorly understood, in part because roots respond to Al stress by altering the chemistry of the rhizosphere. AlCl3 was applied to plots of sugar maple at the Hubbard Brook Experimental Forest, NH. After two years of treatment, we sampled fine roots of sugar maple, rhizosphere soil, and bulk soil in the Oa horizon and the upper 10 cm of the mineral soil. AlCl3 treatments resulted in significantly less Ca (21%) and Mg (30%) in fine roots from the organic horizon, but had no significant effect on fine root Al. Fine root (Ca+Mg):Al ratios were 42% lower in AlCl3 plots than in controls, though most roots had ratios above critical toxicity thresholds developed for hydroponically grown sugar maple seedlings. In the mineral horizon, roots differed only in Mg concentration, which was 22% lower in AlCl3 plots. In the AlCl3 treated plots, rhizosphere soil in the organic horizon had 47% greater Al and 29% less Mg than in controls. Combining data from both treatments we found significantly less Al and organically bound Al in rhizosphere soil than in bulk soil, possibly due to leaching of Al from the rhizosphere by organic acids released by roots. These results suggest that increased mobilization of Al in soil lowers (Ca+Mg):Al ratios in sugar maple fine roots, though roots may minimize Al stress by leaching Al from the rhizosphere.

Sugar maple (Acer saccharum Marsh.) establishment in boreal forest: results of a transplantation experiment

AbstractAim To evaluate whether seedlings of sugar maple (Acer saccharum Marsh.) can establish beyond the species northern range limit in adjacent boreal forest.Location The hardwood–boreal forest transition zone on the north‐east shore of Lake Superior, Ontario, Canada.Methods Seed fall of sugar maple was monitored for 5 years in a stand of this species at its northern range limit, and seed from this stand was transplanted to five micro‐habitat types in an adjacent boreal forest. The establishment and survival of sugar maple seedlings there, and in the seed‐source stand, was monitored for the following 7–11 years. Soil‐surface light levels were measured in both forest types.Results Most seed fell in the final year of monitoring, when c. 250 seeds m−2 were recorded. First‐year seedling establishment rates in the maple stand, deriving from this mast seed year, was approximately double that deriving from seed transplanted to the boreal forest sites; this is tentatively attributed to seed predator satiation in the maple stand. However, subsequent seedling survivorship in the boreal forest was greater than that in the maple stand, resulting in comparable seedling densities by the end of 6 years. This difference is tentatively attributed to better illumination in the boreal forest sites, and canopy‐opening disturbances appear to be especially facilitative of seedling survival.Main conclusions There is no fundamental impediment to sugar maple seedlings establishing in boreal forest communities if climate warming occurs and seed is available. If management intervention is needed to accelerate seed availability in a rapidly warming boreal forest, then diffuse seed application to disturbed boreal forest sites during mast years of local boreal tree species is recommended as the most effective way of avoiding seed predation and increasing seedling survival.

Leaf litter quality and decomposition rates of yellow birch and sugar maple seedlings grown in mono-culture and mixed-culture pots at three soil fertility levels

Seedlings of yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh.) were grown for 2 years in mono-culture and mixed-culture and at three fertility levels. Following the second growing season, senescent leaves were analysed for N concentration, acid hydrolysable substances (AHS), and nonhydrolysable remains (NHR). A litter sub-sample was then inoculated with indigenous soil microflora, incubated 14 weeks, and mass loss was measured. Litter-N was significantly higher at medium than at poor fertility, as well as in yellow birch than in sugar maple litter. The species effect on litter-N increased with increasing fertility. At medium fertility, litter-N of sugar maple litter was lower in mixed-culture than in mono-culture. AHS, NHR as well the NHR/N ratio were significantly higher in yellow birch than in sugar maple litter. At medium fertility, the NHR/N ratio of sugar maple litter was significantly lower in mono-culture than in mixed-culture. Mass loss was significantly greater at medium and rich fertility than at poor fertility, and in yellow birch than in sugar maple litter. At poor fertility, mixed-litter decomposed at a rate comparable to yellow birch, whereas at medium and rich fertility, mixed-litter decomposed at a rate comparable to sugar maple. There was a significant positive relationship between litter-N and mass loss. A similar positive relationship between NHR and mass loss was presumed to be a “species” effect on decomposition. Results support the hypothesis that species × fertility and species × mixture interactions can be important determinants of litter quality and, by implication, of site nutrient cycling.

CO2 enrichment and warming of the atmosphere enhance both productivity and mortality of maple tree fine roots

Summary • Fine roots are the key link for plant water and nutrient uptake, soil carbon (C) input and soil microbial activity in forest ecosystems, and play a critical role in regulating ecosystem C balance and its response to global change. • Red maple ( Acer rubrum ) and sugar maple ( Acer saccharum ) seedlings were grown for four growing seasons in open-top chambers and exposed to ambient or elevated carbon dioxide concentration [CO 2 ] in combination with ambient or elevated temperature. Fine-root production and mortality were monitored using minirhizotrons, and root biomass was determined from soil cores. • Both elevated [CO 2 ] and temperature significantly enhanced production and mortality of fine roots during spring and summer of 1996. At the end of the experiment in September 1997, fine root biomass was significantly lower in elevated temperature chambers, but there were no effects of elevated [CO 2 ] or the interactions between elevated [CO 2 ] and temperature. • Deciduous trees have dynamic root systems, and their activity can be enhanced by CO 2 enrichment and climatic warming. Static measures of root response, such as soil core data, obscure the dynamic nature, which is critical for understanding the response of forest C cycling to global change.

Do elevated ozone and variable light alter carbon transport to roots in sugar maple?

Summary • Here we conducted a series of 14C pulse-chase labeling experiments to test the hypothesis that ozone reduces allocation of recently assimilated carbon to roots of sugar maple (Acer saccharum). • Sugar maple seedlings were fumigated with 1.0 ×, 1.7 × and 3.0 × ambient ozone in open-top chambers for 3 yr under low and high light. Shoots were labeled with 14CO2 for 1 h in August of year 3, and seedlings were harvested 0, 4, 24 and 48 h after labeling. • Three years of ozone fumigation reduced total biomass of seedlings in low and high light treatments by 49% and 34%, respectively, and reduced per cent allocation of total seedling biomass to roots. Ozone similarly reduced allocation of net 14C (gross 14CO2 assimilated at time = 0 minus respiratory losses) to roots after 48 h, but not gross 14C, despite significant ozone effects on 14CO2 assimilation, leaf-level partitioning, and retention of gross carbon in shoots. • Although ozone delayed transport of 14C out of leaves initially, it had no effect on the transport process per se. Any reduction in net allocation to roots is most likely a function of changes in whole-plant source–sink relationships, with control a function of both shoot and root traits.

Relating spatial patterns of sugar maple reproductive success and relative deer density in northern New York State

Previous studies of sugar maple ( Acer saccharum) reproduction and its potential controlling factors have been performed on fine spatial scales (e.g. <1–10 ha), and the outcomes of these studies have often been extrapolated to regional scales (e.g. 1000–100,000 km 2). The resulting public and scientific perceptions are that sugar maple reproduction is declining over large areas in northern forests, and that white-tailed deer ( Odocoileus virginianus) herbivory is an important causal factor in this decline. We examined the validity of these perceptions in northern New York State (42,000 km 2) by performing a geostatistical analysis of sugar maple reproduction based on USDA Forest Service inventory data and relative deer density data constructed from hunter harvest records. We indexed sugar maple reproductive success (SMRS) as the number of sugar maple seedlings and saplings per saw log. Regression analysis indicated that global trends were present for both SMRS ( n=290, multiple r 2=0.085, P<0.001) and relative deer densities ( n=200, multiple r 2=0.17, P<0.001). Autocorrelation analysis indicated that SMRS had weak but significant spatial structuring at scales from 2400 to 40,000 m, but that most of the variability in SMRS probably occurred at scales finer than the data sources were able to detect (<2400 m). Relative deer densities demonstrated spatial patterning at scales from 10,000 to 82,000 m. At the township scale (i.e. approximate spatial grain of 10,000 m), SMRS and relative deer density observations were not correlated ( r 2=0.04, P=0.61, n=143). Additionally, the global trends in SMRS and relative deer density did not appear to be related. Within the range of deer densities observed in northern New York and at spatial scales >10,000 m, high deer densities were not necessarily associated with poor maple reproductive success. Lack of a broad-scale relationship between deer densities and SMRS does not preclude relationships at fine spatial scales (<10,000 m). Potential explanations for the lack of relationship between SMRS and deer density at broad scales include: (1) the generally low deer densities across the study area which may be below critical thresholds to impact reproduction; (2) the importance of functional compared to numerical response of deer in determining deer impact; and (3) the importance of other factors and multiple-factor interactions in affecting spatial patterns of reproductive success.

Phytotoxicity of American beech leaf leachate to sugar maple seedlings in a greenhouse experiment

In an effort to reexamine the factors that affect codominance of American beech (Fagus grandifolia Ehrh.) and sugar maple (Acer saccharum Marsh.), a greenhouse experiment was conducted to test the potential phytotoxic effects of American beech leaf leachate on sugar maple seedlings. We utilized an experimental protocol that addressed phytotoxic, nutrient, and pH effects by watering seedlings with seven treatment solutions: simulated throughfall water, average and dilute concentrations of beech leachate, average and dilute concentrations of maple leachate, and average and dilute concentrations of nutrient solutions. Sugar maple leachate had no effect on sugar maple seedling development, chemistry, or physiology. However, sugar maple seedlings exposed to average levels of beech leachate had significantly lower leaf area, fewer nodes, lower biomass, higher carbon assimilation rates, and higher stomatal conductance than seedlings exposed to the control solution. Results suggest that secondary compounds in beech leaf leachate are suppressing sugar maple seedling development and that field experiments are needed to explore the potential allelopathic relationship between these species.

Indirect effects of beech bark disease on sugar maple seedling survival

To investigate the mechanisms of indirect effects of the increased presence of American beech (Fagus grandifolia Ehrh.) saplings on sugar maple (Acer saccharum Marsh.) seedling survival, I conducted several experiments in the area of the Hubbard Brook Experimental Forest in central New Hampshire, U.S.A. To investigate the effects of competition from beech saplings on sugar maple seedlings, a removal experiment was conducted. Sugar maple seedling survival was monitored in five replicate plots of each of the two treatments for 6 years. Survivorship in plots in which beech saplings had been removed was significantly higher (33%) than in control plots (1%). A shading experiment demonstrated that a large proportion of the mortality of sugar maple seedlings results from the effects of shading. Cutting and shade cloth treatments were done in a two-factor factorial block design, and results showed a strong negative effect of shading in the plot. A third experiment investigated the role of soil moisture. Plots that had higher soil moisture and also had beech removed had the highest survival (76%), while control plots in a dry area had the lowest (22%). Overall, the experiments showed that beech bark disease and the associated increase in beech saplings had a negative indirect effect on sugar maple seedling survival. Sugar maple regeneration failure appeared to be, at least in part, due to the indirect effects of beech bark disease.

The impact of elevated ozone and carbon dioxide on young Acer saccharum seedlings.

The effects of high O3 (200 nl l-1 during the light period) and high CO2 (650 &mgr;l l-1 CO2, 24 h a day) alone and in combination were studied on 45-day-old sugar maple (Acer saccharum Marsh.) seedlings for 61 days in growth chambers. After 2 months of treatment under the environmental conditions of the experiment, sugar maple seedlings did not show a marked response to the elevated CO2 treatment: the effect of high CO2 on biomass was only detected in the leaves which developed during the treatment, and assimilation rate was not increased. Under high O3 at ambient CO2, assimilation rate at days 41 and 55 and Rubisco content at day 61 decreased in the first pair of leaves; total biomass was reduced by 43%. In these seedlings large increases (more than 2-fold) in glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) activity and in anaplerotic CO2 fixation by phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) were observed, suggesting that an enhanced reducing power and carbon skeleton production was needed for detoxification and repair of oxidative damage. Under high O3 at elevated CO2, a stimulation of net CO2 assimilation was observed after 41 days but was no longer observed at day 55. However, at day 61, the total biomass was only reduced by 21% and stimulation of G6PDH and PEPC was less pronounced than under high O3 at ambient CO2. This suggests that high CO2 concentration protects, to some extent, against O3 by providing additional carbon and energy through increased net assimilation.

Herbivory, Disease, and Mortality of Sugar Maple Seedlings

Herbivory, Disease, and Mortality of Sugar Maple Seedlings

The suitability of leaves from different canopy layers for a generalist herbivore (Lepidoptera: Lasiocampidae) foraging on sugar maple

Variations of leaf suitability within forest canopies may have important consequences for the biology of phytophagous insects. In this study we examined over 4 consecutive years (1994–1997), the influence of vertical stratification of leaves within a sugar maple (Acer saccharum Marsh.) stand on biological performance and feeding preference of Malacosoma disstria Hbn. Each year, 10 healthy sugar maple trees and about 15 understory sugar maple seedlings were selected. Leaves were collected from the lower (3–6 m above ground) and the upper crown (20–25 m above ground) sections of the trees and from seedlings. Sampled leaves were set in Petri dishes for insect rearings in controlled environment. The performance of the insect, especially pupal masses and the number of eggs of adult females, was higher when larvae were fed with leaves from the upper crown section of trees. Results for the feeding preference tests showed that larvae of fourth instars consumed more surface area from leaves collected in the upper crown section of the trees. More total nitrogen found in leaves from the upper tree crown could explain the higher performance of this insect. Our results confirm the importance of the heterogeneity in leaf suitability along a vertical stratification in forests by its influence on biological performance and feeding preference of M. disstria.