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Height- diameter equations are important in modeling forest structure and yield. Twenty-seven height- diameter equations were evaluated for eight tree species occurring in the northern hardwood forest of New Hampshire using permanent plot data from the Bartlett Experimental Forest. Selected models with associated coefficients are presented for American beech, eastern hemlock, paper birch, red maple, red spruce, sugar maple, white ash, yellow birch, and all 16 species combined. [ABSTRACT FROM AUTHOR]

We resurveyed a network of sampling plots ( n = 371) 10 years after its establishment in Hubbard Brook Experimental Forest (New Hampshire, USA) to quantify recent trends in tree biomass and demography. We found no significant change in live-tree biomass during the decade. Total biomass was 246 Mg·ha-1 (95%CI = 235-258) in 1995-1996 and 245 Mg·ha-1 (95%CI = 234-256) in 2005-2006. Annual mortality during the period for trees ≥ 10 cm diameter at breast height (1.37 m) averaged 9.7 trees·ha-1·year-1 (95% CI of annual mortality rate = 1.36%-1.84%·year-1). Tree recruitment into the census pool was 8.4 trees⋅ha-1·year-1 (95% CI = 5.8-10.6). Although overall forest biomass remained constant, there were marked shifts in the relative dominance of the canopy species. For example, the live biomass of Betula alleghaniensis Britton declined by 7%, whereas the live biomass of Picea rubens Sarg. increased by 6% and that of Acer saccharum Marshall increased by 4%. There was no instance of recruitment significantly exceeding mortality for the major species. Relative growth rates ranged from 1.03%·year-1 for Betula papyrifera Marshall to 1.99%·year-1 for Abies balsamea (L.) Mill. Our results confirmed earlier reports that the forest at Hubbard Brook is no longer aggrading. Current live-tree biomass is lower than expected. Although effects of novel disturbances documented on a regional level have not led to directional changes in tree demography at Hubbard Brook, we suggest that these novel stressors are depressing the biomass potential of the forest. [ABSTRACT FROM AUTHOR]

Abstract: Acidic deposition has caused a depletion of calcium (Ca) in the northeastern forest soils. Wollastonite (Ca silicate) was added to watershed 1 (WS1) at the Hubbard Brook Experimental Forest (HBEF) in 1999 to evaluate its effects on various functions of the HBEF ecosystem. The effects of Ca addition on foliar soluble (extractable in 5% HClO4) ions, chlorophyll, polyamines, and amino acids were studied in three hardwood species, namely sugar maple, yellow birch, and American beech. We further analyzed these effects in relation to elevation at Ca-supplemented WS1 and reference WS3 watersheds. Foliar soluble Ca increased significantly in all species at mid and high elevations at Ca-supplemented WS1. This was accompanied by increases in soluble P, chlorophyll, and two amino acids, glutamate and glycine. A decrease in known metabolic indicators of physiological stress (i.e., the amino acids, arginine and γ-aminobutyric acid (GABA), and the diamine, putrescine) was also observed. In general, these changes were species-specific and occurred in an elevation dependent manner. Despite an observed increase in Ca at high elevation for all three species, only sugar maple exhibited a decrease in foliar putrescine at this elevation indicating possible remediation from Ca deficiency. At higher elevations of the reference WS3 site, foliar concentrations of Ca and Mg, as well as Ca:Mn ratios were lower, whereas Al, putrescine, spermidine, and GABA were generally higher. Comparison of metabolic data from these three species reinforces the earlier findings that sugar maple is the most sensitive and American beech the least sensitive species to soil Ca limitation. Furthermore, there was an increase in sensitivity with an increase in elevation. [ABSTRACT FROM AUTHOR]

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.--Heart-leaved birch (Betula cordifolia) and yellow birch (B. alleghaniensis) are commonly found growing during early and midsuccession after disturbance in northeastern forests. Betula cordifolia most often occurs at high elevations (above 600 m) and is considered less shade tolerant than B. alleghaniensis. Though shade-tolerance affects distribution of both birches, other physiological differences may also influence the success of each of these species in forest communities. In particular, on boulder-covered depositional zones of landslides common to steep slopes of the Appalachians, water relations may be important for birch survival. In Franconia Notch, NH, a suite of landslides occurred during this century; we investigated water relations of pairs of B. cordifolia and B. alleghaniensis trees rooted within two meters of one another on two of these landslides. Midday water potential of B. alleghaniensis was often significantly more positive (and never more negative) than that of B. cordifolia, whether trees were growing in a soil-rich lower depositional zone of a 1959 slide or on a boulder-covered steep section of an overlapping 1948 slide. Also, the magnitude of differences in water potential between the two birch species varied through the season and between sites. The hydraulic conductivity of stems of the two species was indistinguishable, but predawn water potential measurements indicated that B. cordifolia was rooted in zones with lower water availability. This differential rooting may contribute to differential water stress between young, co-occurring birches in the successional forest environment. [ABSTRACT FROM AUTHOR]

The article presents the description of the body parts of the yellow birch tree in New Hampshire. It describes that the tree has a bicular head when it has grown from a seedling in open ground. It also describes that the leaves of the yellow birch differ from the black birch in their lighter shade of green in which its shape is more elliptical and a longer point at the apex.