Sugar Maple Forest Research Articles

Distributed topographic indicators for predicting nitrogen export from headwater catchments

The possibility of using topographic indicators to predict spatial variation in dissolved nitrogen (N) export from headwater catchments was explored within a sugar maple forest in the Algoma Highlands of central Ontario, Canada, where the average annual export of total dissolved N export ranged from 3.58 to 6.96 kg N ha−1 a−1. Topographic indicators representing both “nondistributed” and “distributed” properties of the catchments were derived. Distributed topographic indicators that were designed to represent hydrologic flushing mechanism for N export were superior in predicting nitrate‐N export, explaining up to 85% in average annual nitrate‐N export and 90% in the slope of discharge versus peak nitrate‐N export which occurred during spring melt. However, the distributed topographic indicators were comparable to nondistributed ones for dissolved organic nitrogen export, explaining up to 68% of the variance compared to 65%. This study shows that spatial variation in N export from catchments within a relatively small region can be substantial, but that distributed topographic indicators can be used to predict a majority of this N export and thereby provide a basis for extrapolating N export from a few intensively monitored catchments to many other catchments within the sugar maple forest of the Algoma Highlands.

Processes regulating the invasion of European buckthorn (Rhamnus cathartica) in three habitats of the northeastern United States

Invasion by exotic plants often is restricted by processes, such as seed predation, acting on early life-history stages; however, the relative importance of these processes might vary among habitats. Modern human land use has created a mosaic of habitats in many landscapes, including the landscape of the northeastern United States. European buckthorn (Rhamnus cathartica) is an exotic plant that has achieved varying success in North American habitats. We studied dispersal, seed survival, germination, and seedling survival of buckthorn populations at four plots in each of sugar maple (Acer saccharum) forests, old fields, and abandoned conifer plantations in central New York State. Dispersal was low in maple forests, as evidenced by low collection rates of R. cathartica seeds in seed traps. Rates of post-dispersal seed predation were highest in maple forests and lowest in old fields, suggesting greater use of maple forests by granivorous rodents. Germination rates did not vary among seeds planted in soils of these habitats when studied in the laboratory despite differences in soil pH. Survival of transplanted seedlings was low in maple forests relative to old fields and plantations. Buckthorn invasion of old fields and abandoned plantations was not strongly constrained by factors we considered, and the buckthorn populations in these habitats were large. A combination of low dispersal by frugivores, low seed survival due to predation, and low seedling survival due to dim light conditions apparently prevents R. cathartica from invasion of intact maple forests of our area. Native fauna and canopy closure may act synergistically to reduce success of invasive plants in natural habitats.

Sensitivity of catchment‐aggregated estimates of soil carbon dioxide efflux to topography under different climatic conditions

Soil respiration (Rs) is an important component of regional carbon budgets in forested landscapes. Within a sugar maple forest on the Algoma Highlands of the Canadian Shield, mosaics of topographic features create gradients in environmental conditions and carbon pools that influence the pattern of Rs within the region. The sensitivity of catchment‐aggregated Rs (CAR) to different spatial partitioning schemes of the landscape under different climate scenarios was examined in two contrasting catchments: one dominated by uplands (C35); the other containing uplands, critical transition zones (transiently saturated areas in isolated depressions or adjacent to wetlands, streams and lakes) and wetlands. CAR was estimated using a six topographic feature representation of the catchments including crest, backslope, footslope, toeslope, inner and outer wetland. CAR was underestimated (−7.4%) or overestimated (30.8%) if coarser spatial partitions were used, but the amount of error differed between catchments and with climatic conditions. A single feature (upland) partitioning scheme performed poorly under all climatic conditions (warm‐wet, warm‐dry, cool‐wet and cool‐dry). A two feature (upland and wetland) partitioning scheme showed improvement, but a partitioning scheme with a minimum of three features (upland, transition and wetland) was needed for accurate estimates of CAR in topographically varying catchments. The critical transition zone had the highest rates of Rs under all climate scenarios, and the critical transition zone and wetland became increasingly larger contributors to CAR under warmer and drier conditions. These observations point to the importance of accounting for the differential contribution of topographic features to Rs in carbon budget models. Failure to do so may lead to inaccurate estimates of landscape‐scale Rs.

Controls on the heterogeneity of soil respiration in a tolerant hardwood forest

The spatial and temporal distribution of soil respiration (Rs) in forested landscapes and its control by environmental conditions and carbon pools has not been sufficiently investigated. A Rs monitoring strategy targeting different topographic features within a sugar maple forest on the Algoma Highlands on the Canadian Shield revealed that the critical transition zones (transiently wet areas adjacent to wetlands, streams, and lakes) yielded significantly larger Rs than adjacent upland or wetland portions of the catchment. Environmental conditions (soil temperature and soil moisture) explained the majority of variance in Rs. An exponential relationship in which the exponent is a polynomial expression that is linear with respect to temperature (°C) and quadratic with respect to moisture (% by volume) explained 57.0% of the variance in Rs (μmol CO2 m−2 s−1). However, inclusion of the quantity of carbon and substrate quality (carbon: nitrogen ratio) in the freshly fallen leaves, and the organic and/or mineral soils into the polynomial regression model explained an additional 15.3% of the variance in Rs (μmol CO2 m−2 s−1). This study highlighted the critical transition zone as major sites of Rs because of the synchronicity in optimal temperature and moisture conditions during the growing season and the large pool of high quality substrate that accumulates in topographic depositional areas.

Predicting tree survival in Ontario sugar maple (Acer saccharum) forests based on crown condition

Decline index (indicator of crown condition) data from 102 forest plots (approximately 10 000 trees) during 1986–2004 were compiled to derive survival models for south-central Ontario, Canada. The dominant species was sugar maple ( Acer saccharum Marsh.) with approximately 75% occurrence (n = 7640). The predictor variables for sugar maple survivorship included the decline index of 1 or 2 years prior to the beginning of the modelled period and ecological region (Algoma, Georgian Bay, Huron–Ontario, and Upper St. Lawrence). The observed crown condition of sugar maple improved significantly over the study period; in contrast, short-term mortality rate did not improve. The risk of sugar maple mortality could be predicted from decline index data for a single year indicating that the risk of tree death increases with higher decline index values (declining crown condition). Moreover, using 2 years of decline index data indicated that the risk of tree death also increased with the length of consecutive time individual trees have higher decline index values. Trees in the Algoma region, which represent the northern limit of sugar maple distribution in Ontario, were significantly more likely to die than trees in Huron–Ontario region.

Foliar and wood chemistry of sugar maple along a gradient of soil acidity and stand health

The decline of sugar maple (Acer saccharum Marsh.) in forest of north-eastern North America is an important environmental issue. In this study, relationships between, soil, wood and foliar chemistry were assessed for 17 stands distributed within a large area of the Quebec sugar maple forest and that were growing on soils with a strong gradient of acidity and base saturation. There were many significant relationships between variables describing the acid-base status of the top-B soil (Ca and Mg concentrations, exchangeable acidity and base saturation) and Ca and Mn concentrations and Ca/Mn and Mg/Mn in tree tissues. Manganese was the element that showed the strongest inverse non-linear relationships with top-B soil base saturation with variance explanation of 71 and 65%, for wood and foliage, respectively. The 17 sites were divided in two groups according to their level of decline. The declining stands had significantly higher wood Mn and Mg concentrations and lower Ca/Mn ratios and significantly higher foliar Mn and lower Ca and Al concentrations. It was impossible to determine if these differences were a cause or a symptom of sugar maple health. However, the increase in Mn concentrations in tree tissues with increasing soil acidity, as well as the higher Mn concentrations in declining as compared to healthy stands suggest that Mn, as well as low Ca availability, could be an important contributing factor in the sugar maple decline.

Lorentzian model of roots for understory yellow birch and sugar maple saplings

Total 66 small (<50 m 2), 24 medium (101–200 m 2) and 36 large (201–500 m 2) canopy gaps at the three sites of yellow birch ( Betula alleghaniensis Britton) and sugar maple ( Acer saccharum Marsh) forests were established in southern Québec, Canada. Half of the gaps were covered by 8×8 m 2 shading cloths to mimic a closed canopy. From these gaps, 46 understory yellow birch and 46 sugar maple saplings with different tree ages and sizes were sampled. Single- and multi-variable linear and nonlinear models of root biomass and traits (root surface area, volume, length and endings) were developed and examined. Lorentzian model as a multi-variable nonlinear model was firstly applied to the simulations using both base diameter and height, and performed the best fit to total root biomass in both species with the highest correlation coefficients ( R 2 = 0.96 and 0.98) and smallest root mean squared deviations ( RMSD=7.85 and 7.02) among all the examined models. The model also accurately simulated small fine root (⩽2.0 mm in diameter), coarse fine root (>2.0–5.0 mm) and coarse root (>5.0 mm) biomass ( R 2=0.87–0.99; RMSD=2.24–6.41), and the root traits ( R 2=0.71–0.99; RMSD=0.19–19.38). The study showed yellow birch roots were longer, larger, had more endings (tips) and grew faster than sugar maple roots. The root traits were largely distributed to small fine roots, sharply decreased from small fine roots to coarse fine roots, the fewest in coarse roots except for root volume. When trees were large, coarse root biomass increased more rapidly than fine root biomass, but vise versa when the trees were small.

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.

On the Relationships between Ground-dwelling Spider (Araneae) Assemblages and Dead Wood in a Northern Sugar Maple Forest

Downed woody material (fallen logs) offers ground-dwelling spiders (Araneae) ideal sites for nesting and foraging, but little is known about what characteristics of dead wood influence spider assemblages. In a maple forest of Forillon National Park, in eastern Quebec (Canada), spider assemblages on, adjacent to, and away from fallen logs were compared. We also tested how log type (coniferous vs. deciduous) and decomposition stage influenced spider assemblages. Sampling was done for an intensive four-week period using both litter samples and pitfall traps. A total of 5613 spiders representing 83 species from 16 families was collected. Spiders were affected by the presence of logs, as both species diversity and total number of individuals collected were significantly higher on the log surface compared to the forest floor. Ordination analysis revealed a distinct compositional difference between the spider fauna found on the wood surface compared to the forest floor. Wood type and decomposition stage had few significant effects on spider assemblages, except that less decayed logs supported higher spider diversity than logs in advanced stages of decay. Dead wood is clearly important for generalist predators such as spiders, further supporting the conservation importance of fallen logs in northern forest ecosystems.

Forest floor gross and net nitrogen mineralization in three forest types in Quebec, Canada

The effect of high nitrogen (N) depositions on forest ecosystems is an important concern in North America and may lead to N saturation of forest ecosystems and contribute to soils and surface water acidification. In this study, nitrogen dynamics in the FH layers of a sugar maple (SM), a balsam fir (BF) and a black spruce (BS) forest was characterized using a short term 15N isotopic pool dilutions approach and mid-term FH material incubation both in situ and in the laboratory. The short term dilutions approach indicated that the mean residence times of NH 4 + and NO 3 - in the FH material of the three sites were low (<1 d). The amount of inorganic nitrogen ( NH 4 + + NO 3 - ) recycled annually within the exchangeable forest floor reservoir was between one and two orders of magnitude larger than the annual atmospheric N deposition found at each of the sites. The BS site was clearly distinct than the two other forest types in that net N mineralization was negligible, even in absence of root uptake, suggesting that soil microorganisms were severely N limited. While net nitrification was not observed within the FH material of the BF site, NO 3 - did accumulate in the FH of the SM despite a low pH of 3.72 presumably because of heterotrophic nitrification or as a result of acid-tolerant autotrophic nitrification. The difference in N dynamics between the sites were most probably caused by dominant tree species. Transformation rates of inorganic N were higher in SM, followed by BF and BS stands. Given that the potential to mineralize inorganic N matches with a superimposed N atmospheric deposition gradient in Québec, the sugar maple forest is more likely to be affected by N saturation than coniferous forests.

A hierarchical approach for simulating northern forest dynamics

Complexity in ecological systems has challenged forest simulation modelers for years, resulting in a number of approaches with varying degrees of success. Arguments in favor of hierarchical modeling are made, especially for considering a complex environmental issue like widespread eastern hemlock regeneration failure. We present the philosophy and basic framework for the NORTHern Woodland Dynamics Simulator (N ORTHWDS) Integrated Hierarchical Model System ( NIHMS). NIHMS has an individual tree component (the N ORTHWDS Individual Response Model ( NIRM)), a mesoscale stand simulator ( NORTHWDS), and a landscape model (N ORTHWDS Landscape Model ( NLM, presented in another paper)). NIRM predicts the behavior of a tree given the physical and biotic environment that constrains its performance, using process-response functions at a scale larger than the individual plant. The NORTHWDS model integrates both the structure of the individual tree model (including tree growth and mortality functions) with a series of ecosystem processes (e.g. competition, site biogeochemistry, small-scale disturbance, deer browsing) and even larger scale events (e.g. catastrophic windthrow) to predict long-term stand dynamics on a 5-year simulation cycle. The boundaries in time and space between the NIRM, NORTHWDS, and NLM models are not discrete, but overlap due to the multiscale expression of ecological and physiological processes. For example, the NORTHWDS model represents both the intersection between the NIRM and NLM models with additional unique mesoscale processes (e.g. intertree competition). At the highest level of NIHMS, NLM provides the environmental context for NORTHWDS, with all levels operating in an internally consistent and parsimonious manner. Three case study scenarios are used to illustrate some of the potential applications of NIRM. Scenario 1: simulation of northern red oak survivorship, crown dynamics, diameter increment, and cumulative propagule production under different local stand densities; Scenario 2: the response of white ash along an available nitrogen gradient with respect to mortality, crown surface area, diameter growth, tree biomass, and propagule production; and Scenario 3: the survivorship and total propagule production of black spruce along a soil moisture gradient. Under Scenario 1, crown size decreased appreciably as local stand density increased from open-grown (<1 m 2/ha) to closed canopy conditions (15–30 m 2/ha), triggering reduced annual increment, lower established propagule production, and increased small tree mortality. Similarly, nitrogen (for white ash) and moisture (for black spruce) gradients significantly affected crown size and growth potential, with many of the same consequences as noted for increased competition in northern red oak. These predictions were consistent with ecological expectations for all scenarios except the black spruce moisture gradient response, which arose because of scale-related issues and the complexity of gradients. To evaluate NORTHWDS model behavior, a 36 ha synthetic stand resembling a hardwood-dominated forest from northern Wisconsin was simulated for 300 years using four windthrow disturbance scenarios (no windthrow, acute windthrow only, chronic windthrow only, and both types of windthrow). Acute (particularly severe but locally discrete and infrequent events) windthrow patterns were designed to generate many small, low intensity events, while chronic windthrow (pervasive yet low intensity cyclic loss of trees) losses depended on species, stature, rooting depth, and tree exposure. These scenarios were compared by examining differences in structural (i.e. biomass, tree richness) and compositional attributes for a number of key species. NORTHWDS predicted the maturation of a pole-sized aspen stand and its eventual conversion to a predominantly sugar maple forest. Quantitatively, aboveground biomass levels comparable to field data were forecast (up to 250–300 Mg/ha, depending on the scenario). The predicted dominance of sugar maple was also consistent with other regional studies, and can be attributed to its shade and browsing tolerance.

Overstory and understory leaf area index as indicators of forest response to ice storm damage

Leaf area index (LAI) was measured with the tracing radiation and architecture of canopies (TRAC) optical instrument in three consecutive summers from 1999 to 2001 in sugar maple forests across eastern Ontario to monitor recovery from ice storm damage suffered in January 1998. The study sites were experimental blocks of the Ontario Ministry of Natural Resources (OMNR) designed for measurement and monitoring of the effects of fertilizer and lime treatments on maple recovery. Understory vegetation survey data, collected in 1999 and again in 2001, were converted to understory gap fraction, and processed in the same manner as the TRAC data to obtain understory LAI. Subtraction of understory LAI from total LAI measured with the TRAC allowed monitoring of productive, overstory trees tapped for syrup production. Annual LAI measurements and LAI change were evaluated in relation to percent crown loss estimates and plot treatments. Understory, overstory and total LAI increased from year-to-year in most plots. Of the single year measurements, total LAI measured in 1999 was significantly related to damage, while 2000 and 2001 LAI accounted for progressively less of the variation in damage, indicating a change in canopy condition between seasons. Understory LAI increased dramatically in response to overstory crown loss, while overstory increased more in absolute terms, but less in relative terms. Between-season LAI change was more significantly related to damage than any of the annual LAI measurements to which it was compared, indicating that LAI response is a better indicator of damage than single year LAI. LAI change was not, however, significantly related to plot treatment.

Field measurements of root respiration indicate little to no seasonal temperature acclimation for sugar maple and red pine.

Increasing global temperatures could potentially cause large increases in root respiration and associated soil CO2 efflux. However, if root respiration acclimates to higher temperatures, increases in soil CO2 efflux from this source would be much less. Throughout the snow-free season, we measured fine root respiration in the field at ambient soil temperature in a sugar maple (Acer saccharum Marsh.) forest and a red pine (Pinus resinosa Ait.) plantation in Michigan. The objectives were to determine effects of soil temperature, soil water availability and experimental N additions on root respiration rates, and to test for temperature acclimation in response to seasonal changes in soil temperature. Soil temperature and soil water availability were important predictors of root respiration and together explained 76% of the variation in root respiration rates in the red pine plantation and 71% of the variation in the sugar maple forest. Root N concentration explained an additional 6% of the variation in the sugar maple trees. Experimental N additions did not affect root respiration rates at either site. From April to November, root respiration rates measured in the field increased exponentially with increasing soil temperature. For sugar maple, long-term Q10 values calculated from the field data were slightly, but not significantly, less than short-term Q10 values determined for instantaneous temperature series conducted in the laboratory (2.4 versus 2.62.7). For red pine, long-term and short-term Q10 values were similar (3.0 versus 3.0). Sugar maple root respiration rates at constant reference temperatures of 6, 18 and 24 degrees C were measured in the laboratory at various times during the year when field soil temperatures varied from 0.4 to 16.8 degrees C. No relationship existed between ambient soil temperature just before sampling and root respiration rates at 6 and 18 degrees C (P = 0.37 and 0.86, respectively), and only a very weak relationship was found between ambient soil temperature and root respiration at 24 degrees C (P = 0.08, slope = 0.09). We conclude that root respiration in these species undergoes little, if any, acclimation to seasonal changes in soil temperature.

Forest Landscape Response to Different Harvest Scenarios under Climate Warming – A Spatial Simulation Study

This study examined forest landscape responses to climate warming in a large (~0.5 million ha) boreal and northern hardwood forest region in northern Wisconsin, U.S.A. We examined whether it contributed to the decline of currently predominant tree species and whether harvests can be used as effective means to prolong the transformation of current forest landscapes to those under warmer conditions. We used a modeling approach by linking a spatially explicit landscape model (LANDIS) with a gap model (LINKAGES). Individual tree species responses at stand scales were simulated with LINKAGES, which integrated soil, climate and species data. Such responses were quantified as inputs for LANDIS, which was then used to integrate large spatial processes such as disturbance and harvesting with ecosystem processes. This protocol allowed us to examine regional forest landscape response to climate warming at the species level with greater realism than by using gap models or landscape transition models alone. Our simulation results suggest that forest landscapes in two ecoregions of northern Wisconsin would experience a significant change under a climate-warming scenario that a 5°C temperature increase occurs over next 100 years. In the lakeshore ecoregion, with more favorable water and nutrient conditions, currently dominant boreal and northern hardwood forests would transform into southern hardwood forests. This result is consistent with the general trends simulated by other models for this region, but shows that landscape transition takes much longer time. By incorporating realistic initial seed source and simulating spatially explicit seed dispersal, our results suggest that the landscape transition is gradual and becomes apparent during 2150–2300 in contemporary time assuming warming occurs from the beginning of this century. Forest harvesting plays an important role in delaying the decline of boreal forests and northern hardwoods. The greatest differences in resulting landscapes under different harvest scenarios (clear cutting group selection, and selection cutting) occurred starting around year 2150. However, harvest does not alter the long-term impacts of climate warming, as the proportions of various cover types simulated under different harvest scenarios at year 300 are very similar. At year 2300 in the lakeshore ecoregion, formerly dominant paper birch, yellow birch, sugar maple, balsam fir, and quaking aspen forests were replaced largely by southern oak species (bur oak, white oak, and black oak), white ash, and hickory. Boreal forests in this ecoregion completely disappeared, while northern hardwoods became a minor cover type compared to southern hardwood forests. A more dramatic transformation occurred in the barrens ecoregion. More than 98% of jack pine and red pine forests disappeared. Because southern hardwood species may be unable to reproduce and establish under warming conditions, the barrens ecoregion could transform into an area with only grass and shrub species.

Health of Eastern North American Sugar Maple Forests and Factors Affecting Decline

Abstract Sugar maple (Acer saccharum) is a keystone species in the forests of the northeastern and midwestern United States and eastern Canada. Its sustained health is an important issue in both managed and unmanaged forests. While sugar maple generally is healthy throughout its range, decline disease of sugar maple has occurred sporadically during the past four decades; thus, it is important to understand the abiotic and biotic factors contributing to sugar maple health. Soil moisture deficiency or excess, highway deicing salts, and extreme weather events including late spring frosts, midwinter thaw/freeze cycles, glaze damage, and atmospheric deposition are the most important abiotic agents. Defoliating insects, sugar maple borer (Glycobius speciosus), Armillaria root disease, and injury from management activities represent important biotic factors. Studies of sugar maple declines over the past four decades reveal that nutrient deficiencies of magnesium, calcium, and potassium; insect defoliation; drought; and Armillaria were important predisposing, inciting, and contributing factors in sugar maple declines. Forestland managers can contribute to sustained health of sugar maple by choosing appropriate sites for its culture, monitoring stress events, and examining soil nutrition.

Fifteen-year Change in Forest Floor Organic and Element Content and Cycling at the Turkey Lakes Watershed

To assess the long-term effects of atmospheric deposition on forest floor chemical composition, we took quantitative samplings of L-(Oi), F-(Oe), and H-(Oa) layers at an old-growth sugar maple-yellow birch stand on a till soil at the Turkey Lakes Watershed near Lake Superior, Ontario, Canada, in 1981 and 1996. We then assessed these samples for contents of organic matter (OM), total N, K, Ca, Mg, S, and Na, and exchangeable NH 4 + , NO 3 - , K + , Ca 2+ , Mg 2+ , SO 4 2- , and Na + . Over the 15-year period, total OM and element contents remained unchanged, with the exception of N, which increased significantly from 61.3 kmol/ha in 1981 to 78.4 kmol/ha in 1996. On an area basis, there were significant increases in exchangeable Ca 2+ (from 3.8 to 4.6 kmol/ha) and Na + (from 0.05 to 0.08 kmol/ha) and decreases in exchangeable NH 4 + -N (from 1.41 to 0.95 kmol/ha) and SO 4 2- -S (from 1.29 to 0.96 kmol/ha). There were no significant differences in average annual litterfall OM, N, Ca, Mg, S or Na inputs between 1980 and 1985 and between 1992 and 1997. Average annual wet-only SO 4 2- -S deposition during 1981-86 was 0.30; during 1992-97, it was 0.21 kmol/ha. Annual wet-only NO 3 - -N averaged 0.33 kmol/ha during 1981-86 and was similar during 1992-97. Throughfall was less rich in SO 4 2- and Ca 2+ , Mg 2+ , and Na + during 1992-97 than earlier. Throughfall NH 4 - and NO 3 - fluxes were unchanged. Efflux of cations from the forest floor reflected reduced throughput of SO 4 2- . Overall, the results suggest that in spite of atmospheric inputs, active biological processes-including litter input, fine-root turnover, and tree uptake-serve to impart stability to the mineral composition of mature sugar maple forest floor.

Community structures of Collembola in sugar maple forests: relations to humus type and seasonal trends

Summary Community structures of Collembola and their seasonal fluctuations were studied in eight southern Quebec sugar maple ( Acer saccharum Marsh.) forests growing on mull, moder and mor humus types. Endogeic species were extracted from soil cores using Berlese-Tullgren funnels while epigeic species were collected using pit-light traps (Luminoc®). Comparisons of species presence, abundance, and dominance among sites and seasons were done using Sorensen's similarity coefficients and CANOCO. A total of 92 species from 7 families and 35 genera were identified. Species dominance and community structure differed according to humus types. Two groups of endogeic species were identified. The mor/mor-moder type group included Folsomia penicula, Hypogastrura (Ceratophysella) spp. Que., Micrisotoma achromata, Onychiurus (Protaphorura)? parvicornis, Onychiurus (Onychiurus) sp. A Que. And Onychiurus (Onychiurus) sp. B Que. The mull/mull-moder type group included Isotoma (Desoria) notabilis, Tullbergia (Tullbergia) silvicola, Tullbergia (Tullbergia) clavata , and Pseudosinella alba. Such clear humus type relationships were not found among the epigeic species, but important seasonal changes in community structures were found for these species. Spring species were Sminthurinus (Katiannina) macgillivrayi, Hypogastrura (Ceratophysella) maheuxi, Hypogastrura (Hypogastrura) sp. A Que. and Sminthurinus (Sminthurinus) latimaculosus. Tomocerus (Pogonognathellus) flavescens, Sminthurinus (Sminthurinus) henshawi , and Orchesella hexfasciata appeared in the summer samples while Dicyrtoma (Dicyrtoma) aurata was found only in fall samples where it was dominant in most sites along with either Sminthurides (Sminthurides) lepus or Sminthurinus (Sminthurinus) quadrimaculatus. No strong seasonal trends were found among the dominant endogeic species.

Relationships between soil chemistry, microbial biomass and the collembolan fauna of southern Québec sugar maple stands

The relationships between the presence of endogeic and epigeic collembolan species and chemical and microbiological top soil parameters were examined for eight sugar maple forests. While the composition of the tree strata was similar among sites, the soil conditions varied widely and encompassed three regions of different geological origins as well as contrasting humus types. Endogeic species were extracted using Berlese-Tullgren equipment, whereas epigeic species were collected with pit-light traps (Luminoc®). In all, 92 species from 14 families and 36 genera were identified. The association between sampling locations and soil parameters was determined by principal component analysis (PCA), and the relationships between epigeic and endogeic collembolan communities and soil parameters were determined by canonical correspondence analysis (CCA and DCCA). The DCCA revealed that the distribution of endogeic species of the collembolan fauna was related to organic matter content, including pH, C, N, and C/N ratio. Sites were clustered according to humus types. Epigeic species were influenced by available P and exchangeable K and Mg. Sites were clustered according to geographical distribution, suggesting that for epigeic species, regional occurrence could be a stronger determinant of community composition than soil parameters.

BIODIVERSITY OF COLLEMBOLA IN SUGAR MAPLE (ACERACEAE) FORESTS

AbstractCollembola of 12 sugar maple forests of southern Quebec were surveyed through pit-light trapping and soil core extraction. These two sampling techniques were highly complementary, as pit-light traps are more efficient for sampling epigaeic species while soil core extractions are more efficient for hypogaeic species. A total of 108 species representing 38 genera and seven families was collected. Nine genera and 67 species are new records for the province of Quebec and 12 species are new records for Canada. The distribution of species among the different sites is summarized and taxonomic remarks are provided for 20 problematic species. A low percentage of the Quebec collembolan fauna is shared with Ontario and Newfoundland, which probably reflects an incomplete inventory of the fauna rather than highly different regional patterns in collembolan communities. The use of these two complementary sampling techniques is suggested to improve the inventory of Collembola in future research.

Prevalence of Fungal Entomopathogens in the Life Cycle of Pear Thrips, Taeniothrips inconsequens (Thysanoptera: Thripidae), in Vermont Sugar Maple Forests

Abstract Few data are available on the occurrence of fungal infections in pear thrips populations in sugar maple stands. Such studies are essential to the long-term development of fungi as effective biological control agents for pear thrips. Our goal was to determine the natural prevalence of infection at different phases in the pear thrips' life cycle, while simultaneously recovering new fungal isolates for possible use in a future control strategy. Sampling thrips from four different sites in central Vermont, the developmental stages associated with the forest soil had the highest levels of infection compared with life stages found predominantly on foliage. The highest rates were seen in larvae recovered from soil samples (11.9%), followed by adults collected from emergence traps and buds (5.9%) and larvae collected from the forest floor (3.9%). In contrast, 1.9% of the individuals sampled from the understory and 1.9% of the thrips collected from the upper canopy were infected. Further studies are needed to test and characterize these strains and assess their potential for use in a pear thrips management program.