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Abstract: Sapwood area is an important parameter for estimating transpiration at whole‐tree and watershed scales, given that it is used for scaling up point sap flow measurements. However, its determination may be difficult, particularly for large‐diameter trees of diffuse‐porous, broad‐leaved species. By delineating only the highly conductive sapwood, electrical resistivity tomography (ERT) may be more appropriate than sapwood dyeing for estimating tree sapwood area. We compared sapwood area measurements made with ERT with those that were obtained from wood dyeing, assuming that the more adequate measure was that which was best correlated with tree leaf area. To achieve this objective, we sampled 31 sugar maple (Acer saccharum Marsh.) and 20 yellow birch (Betula alleghaniensis Britt.) trees covering a large range of tree diameters and leaf areas from one site located in eastern Canada. Also, 79 sugar maple trees were sampled in two other sites to document the estimation of tree leaf area over a large territory. The sapwood area that was determined from ERT appeared to be the best method for scaling up point sap flow measurements to whole‐tree transpiration. The predictive ability of ERT was particularly greater than that of wood dyeing when they were both measured at 1 m. If the objective is to estimate tree leaf area rather than sapwood area, the crown surface area would provide a useful substitute for the ERT method because it is rapid and easy to measure while serving a robust predictor applicable over a large territory. [ABSTRACT FROM AUTHOR]

In terrestrial ecosystems, a large portion (20-80%) of the dissolved Si ( DSi) in soil solution has passed through vegetation. While the importance of this 'terrestrial Si filter' is generally accepted, few data exist on the pools and fluxes of Si in forest vegetation and the rate of release of Si from decomposing plant tissues. We quantified the pools and fluxes of Si through vegetation and coarse woody debris ( CWD) in a northern hardwood forest ecosystem (Watershed 6, W6) at the Hubbard Brook Experimental Forest ( HBEF) in New Hampshire, USA. Previous work suggested that the decomposition of CWD may have significantly contributed to an excess of DSi reported in stream-waters following experimental deforestation of Watershed 2 (W2) at the HBEF. We found that woody biomass (wood + bark) and foliage account for approximately 65% and 31%, respectively, of the total Si in biomass at the HBEF. During the decay of American beech ( Fagus grandifolia) boles, Si loss tracked the whole-bole mass loss, while yellow birch ( Betula alleghaniensis) and sugar maple ( Acer saccharum) decomposition resulted in a preferential Si retention of up to 30% after 16 yr. A power-law model for the changes in wood and bark Si concentrations during decomposition, in combination with an exponential model for whole-bole mass loss, successfully reproduced Si dynamics in decaying boles. Our data suggest that a minimum of 50% of the DSi annually produced in the soil of a biogeochemical reference watershed (W6) derives from biogenic Si ( BSi) dissolution. The major source is fresh litter, whereas only ~2% comes from the decay of CWD. Decay of tree boles could only account for 9% of the excess DSi release observed following the experimental deforestation of W2. Therefore, elevated DSi concentrations after forest disturbance are largely derived from other sources (e.g., dissolution of BSi from forest floor soils and/or mineral weathering). [ABSTRACT FROM AUTHOR]

This paper addresses issues in the microwave phytosanitary treatment of frozen wood. Four eastern Canadian wood species are used: trembling aspen, yellow birch, white birch, and sugar maple. The nonlinear heat conduction problem involving phase changes such as wood freezing is solved by a volumetric specific enthalpy-based finite element method. Dielectric and thermophysical properties are functions of temperature and moisture content. As an application, we studied the dielectric heating of four wood species as a function of moisture content and microwave properties. [ABSTRACT FROM AUTHOR]

Predicting forest responses to warming climates relies on assumptions about niche and temperature sensitivity that remain largely untested. Observational studies have related current and historical temperatures to phenological shifts, but experimental evidence is sparse, particularly for autumn responses. A 4 year field experiment exposed four deciduous forest species from contrasting climates ( Liquidambar styraciflua, Quercus rubra, Populus grandidentata, and Betula alleghaniensis) to air temperatures 2 and 4 °C above ambient controls, using temperature-controlled open top chambers. Impacts of year-round warming on bud burst ( BB), senescence, and abscission were evaluated in relation to thermal provenance. Leaves emerged earlier in all species by an average of 4-9 days at +2 °C and 6-14 days at +4 °C. Magnitude of advance varied with species and year, but was larger for the first 2 °C increment than for the second. Effect of warming increased with early BB, favoring Liquidambar, but even BB of northern species advanced, despite temperatures exceeding those of the realized niche. Treatment differences in BB were inadequately explained by temperature sums alone. In autumn, chlorophyll was retained an average of 4 and 7 days longer in +2 and +4 °C treatments, respectively, and abscission delayed by 8 and 13 days. Growing seasons in the warmer atmospheres averaged 5-18 days (E2) and 6-28 days (E4) longer, according to species, with the least impact in Quercus. Results are compared with a 16 years record of canopy onset and offset in a nearby upland deciduous forest, where BB showed similar responsiveness to spring temperatures (2-4 days °C−1). Offset dates in the stand tracked August-September temperatures, except when late summer drought caused premature senescence. The common garden-like experiment provides evidence that warming alone extends the growing season, at both ends, even if stand-level impacts may be complicated by variation in other environmental factors. [ABSTRACT FROM AUTHOR]

The increasing air temperatures central to climate change predictions have the potential to alter forest ecosystem function and structure by exceeding temperatures optimal for carbon gain. Such changes are projected to threaten survival of sensitive species, leading to local extinctions, range migrations, and altered forest composition. This study investigated photosynthetic sensitivity to temperature and the potential for acclimation in relation to the climatic provenance of five species of deciduous trees, Liquidambar styraciflua, Quercus rubra, Quercus falcata, Betula alleghaniensis, and Populus grandidentata. Open-top chambers supplied three levels of warming (+0, +2, and +4 °C above ambient) over 3 years, tracking natural temperature variability. Optimal temperature for CO2 assimilation was strongly correlated with daytime temperature in all treatments, but assimilation rates at those optima were comparable. Adjustment of thermal optima was confirmed in all species, whether temperatures varied with season or treatment, and regardless of climate in the species' range or provenance of the plant material. Temperature optima from 17° to 34° were observed. Across species, acclimation potentials varied from 0.55 °C to 1.07 °C per degree change in daytime temperature. Responses to the temperature manipulation were not different from the seasonal acclimation observed in mature indigenous trees, suggesting that photosynthetic responses should not be modeled using static temperature functions, but should incorporate an adjustment to account for acclimation. The high degree of homeostasis observed indicates that direct impacts of climatic warming on forest productivity, species survival, and range limits may be less than predicted by existing models. [ABSTRACT FROM AUTHOR]

The widespread occurrence of age-related changes in leaf morphology and allocation suggests that the leaf area index of individual trees (intra-crown LAI) may decline late in ontogeny. We used direct, within-canopy measurements to quantify the LA! of canopy trees with exposed crowns of two temperate deciduous species. Intra-crown LAI declined from ~7 to 4 in Acer saccharum, and from ~9.5 to 6.5 in Betula alleghaniensis, as tree size increased (from 15 to 72 cm diameter at breast height [dbh]). For A. saccharum, age (which varied from 30 to 160 years) was a significantly better predictor of LAI decline than dbh. We also modeled the effect of ontogenetic declines in LAI on understory light availability and found that light transmission increases significantly as canopy trees grow and mature. Our results thus suggest that gradual declines in LAI with tree age may play an important and overlooked role in contributing to the heterogeneity of sub-canopy light regimes in mature forests. [ABSTRACT FROM AUTHOR]

Control of competing vegetation is recommended to ensure successful Yellow birch ( Betula alleghaniensis Britton) regeneration within juvenile stands that do not sustain high enough sapling densities of this species. Four contrasting vegetation control treatments were tested to determine their effect on the growth and vigor of eight-year-old B. alleghaniensis saplings regenerating after final cutting of a shelterwood seed cut. Vegetation control treatments were TC (total circular removal), PC (circular removal of codominant competing vegetation), TS (total semicircular removal on 180° section), and NC (no vegetation control). Two years after treatment application, diameter growth significantly improved in response to vegetation control treatments, whereas sapling height growth did not. This pattern of biomass allocation was directly related to sapling etiolation, which increased with decreasing severity of vegetation removal. As a result, application of vegetation control, especially TC and PC treatments, was valuable in reducing signs of stress in saplings. However, increasing the severity of vegetation removal also made saplings more conspicuous to herbivores, which increased browsing, especially in the TC and PC treatments. Browsing was sufficient in some plots of the TC and PC treatments to overcome the vigor and diameter growth enhancements observed when browsing was negligible. In contrast to the TC and PC treatments, the TS treatment kept browsing very low while largely removing competition. The results suggest that B. alleghaniensis saplings established after final cutting of a shelterwood seed cut do take advantage of vegetation control treatments, but the decision to apply these treatments must include consideration of local herbivore population densities. [ABSTRACT FROM AUTHOR]

• Fertilizer-induced reductions in CO2 flux from soil ( ) in forests have previously been attributed to decreased carbon allocation to roots, and decreased decomposition as a result of nitrogen suppression of fungal activity. Here, we present evidence that decreased microbial respiration in the rhizosphere may also contribute to reductions in fertilized forest soils. • Fertilization reduced by 16–19% in 65-yr-old plantations of northern red oak ( Quercus rubra) and sugar maple ( Acer saccharum), and in a natural 85-yr-old yellow birch ( Betula allegheniensis) stand. • In oak plots, fertilization had no effects on fine root biomass but reduced mycorrhizal colonization by 18% and microbial respiration by 43%. In maple plots, fertilization reduced root biomass, mycorrhizal colonization and microbial respiration by 22, 16 and 46%, respectively. In birch plots, fertilization reduced microbial respiration by 36%, but had variable effects on root biomass and mycorrhizal colonization. • In plots of all three species, fertilization effects on microbial respiration were greater in rhizosphere than in bulk soil, possibly as a result of decreased rhizosphere carbon flux from these species in fertile soils. Because rhizosphere processes may influence nutrient availability and carbon storage in forest ecosystems, future research is needed to better quantify rhizo-microbial contributions to . [ABSTRACT FROM AUTHOR]

Soil–atmosphere fluxes of trace gases (especially nitrous oxide (N2O)) can be significant during winter and at snowmelt. We investigated the effects of decreases in snow cover on soil freezing and trace gas fluxes at the Hubbard Brook Experimental Forest, a northern hardwood forest in New Hampshire, USA. We manipulated snow depth by shoveling to induce soil freezing, and measured fluxes of N2O, methane (CH4) and carbon dioxide (CO2) in field chambers monthly (bi-weekly at snowmelt) in stands dominated by sugar maple or yellow birch. The snow manipulation and measurements were carried out in two winters (1997/1998 and 1998/1999) and measurements continued through 2000. Fluxes of CO2 and CH4 showed a strong seasonal pattern, with low rates in winter, but N2O fluxes did not show strong seasonal variation. The snow manipulation induced soil freezing, increased N2O flux and decreased CH4 uptake in both treatment years, especially during winter. Annual N2O fluxes in sugar maple treatment plots were 207 and 99 mg N m−2 yr−1 in 1998 and 1999 vs. 105 and 42 in reference plots. Tree species had no effect on N2O or CO2 fluxes, but CH4 uptake was higher in plots dominated by yellow birch than in plots dominated by sugar maple. Our results suggest that winter fluxes of N2O are important and that winter climate change that decreases snow cover will increase soil:atmosphere N2O fluxes from northern hardwood forests. [ABSTRACT FROM AUTHOR]

1 Traditional rankings of shade tolerance of trees make little reference to individual size. However, greater respiratory loads with increasing sapling size imply that larger individuals will be less able to tolerate shade than smaller individuals of the same species and that there may be shifts among species in shade tolerance with size. 2 We tested this hypothesis using maximum likelihood estimation to develop individual-tree-based models of the probability of mortality as a function of recent growth rate for seven species: trembling aspen, paper birch, yellow birch, mountain maple, white spruce, balsam fir and eastern white cedar. 3 Shade tolerance of small individuals, as quantified by risk of mortality at low growth, was mostly consistent with traditional shade tolerance rankings such that cedar > balsam fir > white spruce > yellow birch > mountain maple = paper birch > aspen. 4 Differences in growth-dependent mortality were greatest between species in the smallest size classes. With increasing size, a reduced tolerance to shade was observed for all species except trembling aspen and thus species tended to converge in shade tolerance with size. At a given level of radial growth larger trees, apart from aspen, had a higher probability of mortality than smaller trees. 5 Successional processes associated with shade tolerance may thus be most important in the seedling stage and decrease with ontogeny. [ABSTRACT FROM AUTHOR]

An algorithm ( Weather Reader) was developed and used to analyze daily weather records from all existing Canadian and American weather stations of eastern North America (in excess of 2100 stations), from 1930 through 2000. Specifically, the Weather Reader was used to compile daily minimum, mean, and maximum air temperatures for weather stations with at least 30 years of data, and was used to calculate accumulated degree days for winter thaw–freeze events relevant to yellow birch ( Betula alleghaniensis Britt.) from beginning to end. A thaw–freeze event relevant to yellow birch was considered to take place when (i) the station daily maximum temperature reached or exceeded +4°C after being below freezing for at least 2 months of the winter, (ii) sufficient growing degree days accumulated (>50 growing degree days) to cause the affected yellow birch trees to prematurely deharden, and (iii) the daily minimum temperature dropped below −4°C causing roots and/or shoots of dehardened trees to experience freeze-induced injury and possibly dieback. The threshold temperature of +4°C represents the daily temperature above which biological activity occurs in yellow birch. The station growing degree day summaries were subsequently spatially interpolated with the Kriging function in GS+™ and mapped in ArcView™ GIS in order to display the geographic extent of the most severe thaw–freeze events. The ArcView™ maps were then compared with the extent of historically observed yellow birch decline. It was found that the years 1936, 1944, and 1945 were particularly uncharacteristic in terms of region-wide winter thaw–freeze extremes, and also in terms of observed birch decline events during 1930–1960. An overlay of suspected accumulated birch decline based on thaw–freeze mapping and observed decline maps prepared by , and for 1930–1960 demonstrated similar geographic patterns. The thaw–freeze projection for 1930–1960 was shown to coincide with 83% of the birch decline map appearing in and 55% of the geographic range of yellow birch in eastern North America. Thaw–freeze mapping was also applied to two significant events in 1981. Greatest impact was recorded to occur mostly in southern Quebec and Ontario, and several American Great Lake States, specifically in northern Michigan and New York, where the greatest growing degree day accumulation prior to refreeze in late February (February 28th) was projected to have occurred; and in southern Quebec, most of Atlantic Canada, and Maine, prior to a late spring frost in mid-April (April 17). [ABSTRACT FROM AUTHOR]

The article investigates canopy recruitment in harvest openings created by group selection in hemlock-hardwood forests. The researchers measured gap trees in openings ranging from 40 to 1000 square meters and up to 55 years old. Sample trees up to 25 meters tall, spanning all stages of the gap capture process, were destructively sampled to determine height growth rates, total age, and size at time of gap formation. Results indicate that yellow birch comprised greater than 40% of the upper stratum of gap saplings in openings as small as 100-400 square meters. The ultimately successful hardwood gap trees, on average, reached crown shoulder height of the mature gap border trees within 28-37 years after gap formation. Successful trees were mostly advanced regeneration at the time of gap formation, but some gap colonists were also successful. Height increments in all hardwood species were strongly size dependent, with saplings reaching a maximum growth rate at a height of 10 meters. Extrapolation of current height growth of saplings less than 3 meters tall would substantially overestimate time needed for gap capture, but use of a size-dependent height increment function provided accurate estimates.

Despite its importance in the terrestrial C cycle rhizosphere carbon flux (RCF) has rarely been measured for intact root–soil systems. We measured RCF for 8-year-old saplings of sugar maple (Acer saccharum) and yellow birch (Betula allegheniensis) collected from the Hubbard Brook Experimental Forest (HBEF), NH and transplanted into pots with native soil horizons intact. Five saplings of each species were pulse labeled with13CO2 at ambient CO2 concentrations for 4–6 h, and the13C label was chased through rhizosphere and bulk soil pools in organic and mineral horizons for 7 days. We hypothesized yellow birch roots would supply more labile C to the rhizosphere than sugar maple roots based on the presumed greater C requirements of ectomycorrhizal roots. We observed appearance of the label in rhizosphere soil of both species within the first 24 h, and a striking difference between species in the timing of13C release to soil. In sugar maple, peak concentration of the label appeared 1 day after labeling and declined over time whereas in birch the label increased in concentration over the 7-day chase period. The sum of root and rhizomicrobial respiration in the pots was 19% and 26% of total soil respiration in sugar maple and yellow birch, respectively. Our estimate of the total amount of RCF released by roots was 6.9–7.1% of assimilated C in sugar maple and 11.2–13.0% of assimilated C in yellow birch. These fluxes extrapolate to 55–57 and 90–104 g C m−2 yr−1 from sugar maple and yellow birch roots, respectively. These results suggest RCF from both arbuscular mycorrhizal and ectomycorrhizal roots represents a substantial flux of C to soil in northern hardwood forests with important implications for soil microbial activity, nutrient availability and C storage. [ABSTRACT FROM AUTHOR]

Abstract Within the northern Great Lakes region, mesoscale (10s to 100s of km²) [patterning is driven by disturbance dynamics. Using original Public Land Survey (PLS) records in northern Wisconsin, USA, we study spatial patterns of wind and fire disturbances during the pre-Euroamerican settlement period (ca. 1850). Our goals were: (1) to determine how effectively wind and fire disturbance can be reconstructed from the PLS, (2) to assess the roles of wind and fire in shaping vegetation patterns, (3) to evaluate landscape to regional controls of wind and fire regimes, and (4) to assess the potential for interactions between these disturbances. Our analyses indicate that only relatively intense fire and wind disturbance can be reliably detected from the PLS (62-68% canopy removal). Heavy wind throw was more prevalent than fire disturbance in presettlement forests, and wind-disturbed patches were comparatively smaller and more complex in shape. Disturbance rotation periods ranged between 450 and 10500 years for heavy wind throw and between 700 and 93000 years for stand-replacing fire. Occurrences of wind and fire disturbance were related to geographic province and to regional soil patterns: analysis further suggests a negative interaction between the two disturbance types. Given that severe wind disturbance was infrequent, mature to old forests of late-successional species dominated much of pre-Euroamerican northern Wisconsin, but wind disturbances may have allowed regional persistence of less shade-tolerant species, such as Betula alleghaniensis. Pine-dominated vegetation was limited to regions with more frequent fire, but frequencies of stand-replacing fire derived from survey records were insufficient to maintain these successional vegetation types; we suggest that frequent surface fires, not recorded in the PLS. along with infrequent stand-replacing fire, maintained these vegetation types. The extensive nature of the PLS provides a powerful baseline for addressing changes in forest conditions and disturbance regimes associated with climate and land use for both the present and more distant past. Such baselines are informative in discussions of historical variability and restoration silviculture. [ABSTRACT FROM AUTHOR]

Despite increasing evidence of seed limitation in forest ecosystems, data remain sparse on spatial patterns of seed rain at large (>1 ha) spatial scales. We monitored seed rain (28.5 m²) throughout five northern hardwood forest fragments (27 ha sampled across 14-km² area) in southeastern Michigan over two years. Four fragments were nearest neighbors (300-700 m), yet varied in species compositions providing the opportunity to. detect landscape-scale seed exchange. Of the 37 species of woody plants present in the seed rain (98 032 mature seeds), only three (Betula papyrifera, Ostrya virginiana, and Ulinus americana) had widespread seed dispersions within all fragments containing resident sources (seed in >70% of traps in each fragment). Seed dispersions, measured as the percentage of traps within a fragment receiving seed, differed among species using different dispersal vectors with animal-dispersed species arriving in a lower percentage of seed traps than wind-dispersed seeds. At a given source density, seed dispersions increased with decreasing seed mass. Light-seeded fecund species such as Betula or Tsuga required lower source densities to saturate fragments with seed compared toheavy-seeded species (Acer, Fraxinus, Tilia). Heavy-seeded wind- and animal-dispersed species also displayed the strongest evidence of seed limitation, with seedling presence significantly associated with presence of seed for Carpinus caroliniana, Fagus grandifolia, Prunus avium, and Tilia americana. Of 17 species, landscape-Scale seed exchange was detected for only four disturbance-associated species (Acer negundo, Betula papyrifera, Celastrus scandens, Eleaganus umbellata). [ABSTRACT FROM AUTHOR]

Reports on the identification of a major source of systematic error in the laboratory evaluation of two bioenergetics models applied to the yellow birch fish. Evaluation of the models by using the laboratory growth and food consumption data for the yellow perch; Deficiencies in estimating the resting routine metabolism by both models; Causes for the inter-model differences in growth and consumption differences.

Presents information on a study about the masting or mast seeding in tree species, Abies balsamea, Acer saccharum and Betula alleghaniensis in a cold temperate forest of north eastern North America. Information about the species; Materials and methods used in the study; Results; Discussion.

AbstractIncreased levels of atmospheric CO2 may alter the structure and composition of plant communities by affecting how species respond to their physical and biological environment. We investigated how elevated CO2 influenced the response of paper birch ( Betula papyrifera Marsh.) and yellow birch (Betula alleghaniensis Britt.) seedlings to variation in soil moisture. Seedlings were grown for four months on a soil moisture gradient, individually and in mixed species stands, in controlled environment facilities at ambient (375 μL L–1) and elevated (700 μL L–1) atmospheric CO2. For both individually and competitively grown paper birch seedlings, there was a greater CO2 growth enhancement for seedlings watered less frequently than for well-watered seedlings. This differential change in CO2 responsiveness across the moisture gradient reduced the difference in seedling growth between high and low water levels and effectively broadened the regeneration niche of paper birch. In contrast, for yellow birch seedlings, elevated CO2 only produced a significant growth enhancement at the wet end of the soil moisture gradient, and increased the size difference between seedlings at the two ends of the gradient. Gas exchange measurements showed that paper birch seedlings were more sensitive than yellow birch seedlings to declines in soil moisture, and that elevated CO2 reduced this sensitivity. Additionally, elevated CO2 improved survival of yellow birch seedlings growing in competition with paper birch in dry stands. Thus, elevated CO2 may influence regeneration patterns of paper birch and yellow birch on sites of differing soil moisture. In the future, as atmospheric CO2 levels rise, growth of paper birch seedlings and survival of yellow birch seedlings may be enhanced on xeric sites, while yellow birch may show improved growth on mesic sites. [ABSTRACT FROM AUTHOR]

Presents an analysis of the spatiotemporal patterns of the seeds in the seed rain and the seed bank and of newly-emerged seedlings of Betula alleghaniensis, Acer rubrum, A. saccharum and Fagus grandifolia. Traits which are useful discriminators between the four species; Seed bank and newly emerged seedlings of shade-intolerant species compared to shade-tolerant species.

1. The relationship between seed and seedling spatial patterns of abundance was examined for live tree species in a deciduous forest of north-eastern North America. In this low-diversity forest, seed shadows (from different individuals of a given tree species) may overlap to a significant extent. The selective advantages of greater seed dispersal ability in order to avoid high predation and pathogen attack and intraspecific competition at proximity to the parent tree is unclear in this context. 2. On the study site, there were no strong and consistent relationships between seed and seedling spatial patterns of abundance for any of the tree species studied. Dispersion patterns of seeds or seedlings varied between quadrats and did not necessarily correspond within any one quadrat: e.g. clumped seeds and randomly dispersed seedlings. Seeds of Betula alleghaniensis were positively associated, but its seedlings were negatively associated with those of the other tree species. Good seed dispersal ability and highly specific germination microsites may partly explain these latter observations. 3. Seed or seedling mortality for Acer saceharum was not strongly related to seed or seedling abundance, leading to rejection of the hypothesis that seed and seedling mortality was density dependent for this species on the study site. Moreover, seed mortality was spatially uncoupled from seedling mortality. Spatial and temporal variation in the relative importance of mortality factors (e.g. predation, pathogen attack and competition) on seeds and seedlings may account for these results. Because many factors seem to control seed and seedling spatial patterns of abundance and mortality on any one site, and because the significance of these factors appears to vary over time, the relationship between seed and seedling spatial pat- terns in old-growth forests may often be obscure. [ABSTRACT FROM AUTHOR]

(1) Seed dynamics of Betula alleganiensis (yellow birch) were studied in a sugarmaple-yellow-birch forest near Quebec. Canada The seed rain was censused regularly during 1988 and 1989, and the soil seed bank was sampled at various times during the 1988 season, Seedlings of the 1988 and the 1989 cohorts were also surveyed, Dispersion patterns of seeds in the seed rain and in the seed bank, and of newly emerged seedlings, were contrasted. (2) No viable seeds were shed before the end of August in 1988, although by then the cumulative seed rain totalled 222 ? 103 seeds m[SUP-2] (mean ±I.S.E.). Viability of seeds in the seed rain was low in August 1988 (3%), but increased through the season to a peak at the end of October 74·4%), at the time of maximum seedfall (7377±99 seeds m[SUP-2] week[SUP-1]. Seed dispersal of the 1988 seed crop continued until the following spring and early summer. Seedfall during the 1988-89 winter period accounted for 24% of the viable seeds disseminated from August 1988 to July 1989. Autumn 1989 seed rain was fifteen rimes lower than that of autumn 1988 Furthermoree, seed viability was significantly lower in amtumn 1989 than in autumn 1988 (20% and 53% respectively) Seeds were contagiously dispersed over the site both m 1988 and in 1989. Seed-rain spatial pattern during the winter period differed from both autumn 1988 and autumn 1989 patterns. (3l) Seasonal dynamics of the seed bank mostly involved the litter layer. Seed number (in 1988) in the litter layer declined from June (192±26 viable seeds m[SUP-2] through July (107 ± 18 viable seeds m[SUP-2] to August (77±14 viable seeds m[SUP-2], but increased in October (1297± 143 seeds m[SUP-2] as a result of inputs from the seed rain. No significant changes in the number of viable seeds m the humus and the mineral layers were detected between the four sampling dates, implying that inputs from the top soil layer(s) equalled losses. Seeds of the... [ABSTRACT FROM AUTHOR]

This report deals with total extraction and activation of soluble indoleacetic acid oxidase from Betula alleghaniensis leaves as affected by different buffers, varying pH, phenol binder, detergent, plus volume and time parameters. For all buffers and pH levels tested, only tris pH 8 gave a high activity. This result was not a pH effect, since a wide‐range, citrate‐phosphate buffer at pH 8 gave a very low activity. Addition of a neutral detergent, Triton X‐100, to all buffers gave considerable activity in every case. Most activity with Triton X‐100 occurred at pH 6 and least at pH 8 regardless of buffer composition. A phenol binder, polyvinylpyrollidone, increased activity also, but less than the detergent Triton X‐100. Both of these compounds in combination gave an additive effect and the highest measure of enzyme activity. Further increases in measurable indoleacetic acid oxidase activity were obtained by using the best combination of these factors to determine the optium tissue: buffer ratio and optimum soaking time. Increases in activity of 70 and 60%, respectively, were achieved. [ABSTRACT FROM AUTHOR]

Analyzes the spatial patterns of seed rain, seed bank, and seedling emergence of a major tree component, Betulla alleghaniensis. Examination of the degree of consistency of spatial patterns of life stage and their relationship with each other; Methodology used in this research; Causes of recruitment in plants; Results and discussion.

Presents an experiment to quantify the net effects of four major physiognomic types on the growth and survival of sugar maple (Acer saccharum), red maple (Acer rubrum) and gray birch (Betula populifolia). Shrub thickets; Shrubby grass meadows; Grass meadows; Herbaceous meadows; Seedling growth; Intensity of competition; Favorability of the site.

The variability of virulence within a Quebec population of the fungal pathogen nectria galligena was studied under greenhouse conditions. Preliminary, small-scale inoculation of betula alleghaniensis saplings confirmed that wounds have to be present for successful infection by galligena and showed that saplings held at 10°C exhibited a broader range in necrotic zone length than saplings held at 24°C for 6 weeks. Results from the inoculation of alleghaniensis saplings with eight full-sib progeny sets of four siblings each of galligena showed a wide range of virulence in this pathogen.

We studied seedling growth responses to ambient and elevated CO2 (350 and 700 µL L-1 of three maternal families of yellow birch (Betula alleghaniensis), raised both individually and in high-density stands. Seedlings in competitive, dense stands exhibited markedly lower average CO2-induced growth enhancements than individually grown plants (16% vs. 49%). Maternal families differed in their growth responses to elevated CO2. However, differences among families were contingent upon density; families which exhibited the greatest CO2-induced growth at low density exhibited the least CO2-responsiveness at high density. These data are discussed in two separate contexts; the reliability of estimates of the CO2 fertilization potential of forest species based solely on individually grown plants, and the potential evolutionary consequences of rising CO2 on regenerating forest tree populations. [ABSTRACT FROM AUTHOR]

Root exudates from the unsuberized tips of new woody roots were collected from mature Betula alleghaniensis, Fagus grandifolia, and Acer saccharum in a northern hardwood forest. Numbers of new woody root tips were also determined for these three species. Exudates were fractioned into carbohydrates, amino acids/amides, organic acids, and 9 inorganic ions. Considerable species variation characterized the quantitative and qualitative nature of the organic fraction. Organic acids were the most abundant component. Fagus grandifolia released the largest amount of amino and organic acids per hectare, while B. alleghaniensis exuded the largest amount of carbohydrates. Sodium (possibly anomalous), K, and Ca dominated the cationic fraction, while the anionic fraction was chiefly SO4 and Cl. Betula alleghaniensis and F. grandifolia released considerably greater quantities of inorganic ions than A. saccharum, but the inorganic root exudate patterns of the three species were relatively uniform. These results indicate root exudates have some role in intrasystem nutrient cycling. [ABSTRACT FROM AUTHOR]

1. Replicate populations of crowded, regenerating stands of Betula alleghaniensis were grown in ambient and elevated (700p.p.m.) atmospheric CO2 concentrations in monoliths of forest soil. Early in the second year the seedlings were harvested and detailed measurements of individual plant root architectural parameters and ectomycorrhizal colonization were made. 2. Comparing the average responses of individual plants within the populations, elevated CO2 had no significant effects on architectural parameters that improve a plant's ability to forage for and acquire soil resources. In contrast, the intensity and magnitude of mycorrhizal colonization, and whole plant C/N ratios were significantly enhanced with elevated CO2. 3. The allometric scaling relationship between total plant biomass and root biomass was not affected by CO2, suggesting that relative allocation between roots and shoots was not affected. However, the allometric scaling relationships between root architectural parameters and plant biomass, and between fine root biomass and woody root biomass were significantly altered by elevated CO2. For all of these relationships, elevated CO2 reduced the 'size bias' of architectural components in relation to plant size within the populations; in elevated CO2 root architectural size (e.g. root length) per unit biomass was more similar between the smallest and largest individuals within the population than was the case for ambient CO2. 4. Overall, the results of this study suggest that the average individual seedling biomass and architectural growth responses within populations of plants exposed to elevated atmospheric CO2 levels may be unresponsive, but that mycorrhizal responses and interactions among plants within populations may be altered significantly. These findings have important implications for how we make predictions about plant growth responses to elevated CO2 in natural ecosystems. Significant increases in mycorrhizal infection rates and architecture-biomass allometries suggest that below-ground competitive interactions within plant populations may be reduced in elevated CO2. Alterations in competitive interactions may lead to shifts in productivity and plant population structure. [ABSTRACT FROM AUTHOR]

Established in 1935, a regular grid of 256 permanent plots includes about 20% of a 100-ha old-growth forest at the Dukes Research Natural Area in northern Michigan, USA. Woody stems have been re-measured 3-7 times providing extensive quantitative records of population and community dynamics over periods of up to 72 years. Woody stems in upland hemlock-northern hardwood stands, about half of the study plots, have been mapped and individually tracked since about 1990. Remaining plots are in swampy stands dominated by Fraxinus nigra and Thuja occidentalis. Detailed, long-term demographic data for late-successional forests are rare in general; this data set is both of exceptional duration and unusual in spatial intensity and detail. Because sample plots are in a regular array over the stand, they can support analyses of spatiotemporal pattern at various scales. A major wind disturbance in 2002 provides .a unique opportunity to compare disturbance response to baseline dynamics. Several publications based on this data set have already provided new insights into late-successional processes, but general availability of the data set with metadata should permit a range of further comparative and integrative analyses. The study is ongoing, and new measurements will be added to the archived data set. [ABSTRACT FROM AUTHOR]