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  • 1
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; nitrogen ; nutrient cycling ; spruce decline ; subalpine spruce-fir
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen inputs, fluxes, internal generation and consumption, and outputs were monitored in a subalpine spruce-fir forest at approximately 1000-m elevation on Whiteface Mountain in the Adirondacks of New York, USA. Nitrogen in precipitation, cloudwater and dry deposition was collected on an event basis and quantified as an input. Throughfall, stemflow, litterfall and soil water were measured to determine fluxes within the forest. Nitrogen mineralization in the forest floor was estimated to determine internal sources of available N. Lower mineral horizon soil water was used to estimate output from the ecosystem. Vegetation and soil N pools were determined. During four years of continuous monitoring, an average of 16 kg N ha−1 yr−1 was delivered to the forest canopy as precipitation, cloudwater and dry deposition from the atmosphere. Approximately 30% of the input was retained by the canopy. Canopy retention is likely the result of both foliar uptake and immobilization by bark, foliage and microorganisms. Approximately 40 kg of N was made available within the forest floor from mineralization of organic matter. Virtually all the available ammonium (mineralized plus input from throughfall) is utilized in the forest floor, either by microorganisms or through uptake by vegetation. The most abundant N component of soil water solutions leaving the system was nitrate. Net ecosystem fluxes indicate accumulation of both ammonium and nitrate. There is a small net loss of organic N from the ecosystem. Some nitrate leaves the bottom of the B horizon throughout the year. Comparisons with other temperate coniferous sites and examination of the ecosystem N mass balance indicate that N use efficiency is less at our site, which suggests that the site is not severely limited by N.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5001
    Keywords: Triple-resonance spectroscopy ; NMR signal assignment ; Chemical Shift Index ; Protein secondary structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Nearly complete backbone 1H, 15N and 13C signal assignments are reported for β-hydroxydecanoyl thiol ester dehydrase, a 39-kDa homodimer containing 342 amino acids. Although 15N relaxation data show that the protein has a rotational correlation time of 18 ns, assignments were derived from triple-resonance experiments recorded at 500 MHz and pH 6.8, without deuteration. The Chemical Shift Index, CSI, identified two long helices and numerous β-strands in dehydrase. The CSI predictions are in close agreement with the secondary structure identified in the recently derived crystal structure, particularly when one takes account of the numerous bulges in the β-strands. The assignment of dehydrase and a large deuterated protein [Yamazaki et al. (1994) J. Am. Chem. Soc., 116, 11655–11666] suggest that assignment of 40–60 kDa proteins is feasible. Hence, further progress in understanding the chemical shift/structure relationship could open the way to determine the structures of such large proteins.
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  • 3
    Publication Date: 2022-05-25
    Description: © The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution-Noncommercial License. The definitive version was published in Ecosystems 13 (2010): 239-248, doi:10.1007/s10021-010-9315-8.
    Description: Ecosystem nutrient budgets often report values for pools and fluxes without any indication of uncertainty, which makes it difficult to evaluate the significance of findings or make comparisons across systems. We present an example, implemented in Excel, of a Monte Carlo approach to estimating error in calculating the N content of vegetation at the Hubbard Brook Experimental Forest in New Hampshire. The total N content of trees was estimated at 847 kg ha−1 with an uncertainty of 8%, expressed as the standard deviation divided by the mean (the coefficient of variation). The individual sources of uncertainty were as follows: uncertainty in allometric equations (5%), uncertainty in tissue N concentrations (3%), uncertainty due to plot variability (6%, based on a sample of 15 plots of 0.05 ha), and uncertainty due to tree diameter measurement error (0.02%). In addition to allowing estimation of uncertainty in budget estimates, this approach can be used to assess which measurements should be improved to reduce uncertainty in the calculated values. This exercise was possible because the uncertainty in the parameters and equations that we used was made available by previous researchers. It is important to provide the error statistics with regression results if they are to be used in later calculations; archiving the data makes resampling analyses possible for future researchers. When conducted using a Monte Carlo framework, the analysis of uncertainty in complex calculations does not have to be difficult and should be standard practice when constructing ecosystem budgets.
    Keywords: Monte Carlo ; Hubbard Brook ; Forest biomass ; Allometric equations ; Error analysis ; Ecosystem N budget
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/vnd.ms-excel
    Format: application/pdf
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  • 4
    Publication Date: 2002-10-01
    Description: A major ice storm in January 1998 provided an opportunity to study the effects of a rare, intense disturbance on the structure of the northern hardwood forest canopy. Canopy damage was assessed using visual damage classes within watersheds of different ages at the Hubbard Brook Experimental Forest (HBEF) and changes in leaf area index in two of these watersheds. Ice thickness was measured, and ice loads of trees were estimated using regression equations. In the 60- to 120-year-old forests (mean basal area 26 m2·ha1), damage was greatest in trees 〉30 cm diameter at breast height and at elevations above 600 m. Of the dominant tree species, beech (Fagus grandifolia Ehrh.) was the most damaged, sugar maple (Acer saccharum Marsh.) was the most resistant, and yellow birch (Betula alleghaniensis Britt.) was intermediate. Trees with advanced beech bark disease experienced heavier ice damage. Little damage occurred in the 14-year-old forest, while the 24- to 28-year-old forest experienced intense damage. In the young stands of this forest, damage was greatest between 600 and 750 m, in trees on steep slopes and near streams, and among pin cherry (Prunus pensylvanica L.). Recovery of the canopy was tracked over three growing seasons, and root growth was monitored 1 year after the storm. Because of the high density of advance regeneration from beech bark disease and root sprouting potential in ice-damaged beech, HBEF will likely see an increase in beech abundance in older forests as a result of the storm. There will also be a more rapid change from pioneer species to mature northern hardwoods in the younger forests. These predictions illustrate the ability of rare disturbances to increase heterogeneity of forest structure and composition in this ecosystem, especially through interactions with other disturbances.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 5
    Publication Date: 2016-05-01
    Description: Forest health deteriorated in eastern North America as a result of depletion of available soil base cations by elevated inputs of acid deposition. We experimentally restored available calcium (Ca) to soils of a forested watershed at Hubbard Brook, New Hampshire, and measured the response of fine root biomass 14 years after treatment. In this northern hardwood forest, fine root (
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 6
    Publication Date: 2006-06-01
    Description: Hemlock woolly adelgid (HWA; Adelges tsugae Annand) infestations have resulted in the continuing decline of eastern hemlock (Tsuga canadensis (L.) Carrière) throughout much of the eastern United States. In 1994 and 2003, we quantified the vegetation composition and structure of two hemlock ravines in the Delaware Water Gap National Recreation Area. This is the first study to use pre-adelgid disturbance data, annual monitoring of infestation severity, and annual records of hemlock health to assess forest response to HWA infestation. In 2003, 25% of monitored hemlock trees were either dead or in severe decline. Measures of hemlock decline (crown vigor, transparency, density, and dieback) were correlated with HWA infestation severity and changes in light availability over the study period. Average percent total transmitted radiation more than doubled at these sites from 5.0% in 1994 to 11.7% in 2003. The total percent cover of vascular plants increased from 3.1% in 1994 to 11.3% in 2003. Species richness increased significantly, and more species were gained (53) than lost (19) from both ravine floras over the 9-year study period. Though exotic invasive plants were absent from these ravines in 1994, our 2003 resurvey found invasive plants in 35% of the permanent vegetation plots.
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    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
    Publication Date: 2004-03-01
    Description: Replicated circular openings ranging in size from 0.1 to 1 ha were cleared in 1996 at Blodgett Forest Research Station, California, and planted with seedlings of six native species. After 5 years of postharvest growth, heights were measured and analyzed according to species, opening size, and location within opening. The sequence of mean height from tallest to shortest, according to species, was as follows: giant sequoia (Sequoiadendron giganteum (Lindl.) Buchholz) 〉 incense-cedar (Calocedrus decurrens (Torr.) Florin) 〉 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) ≈ ponderosa pine (Pinus ponderosa Dougl. ex Laws.) 〉 sugar pine (Pinus lambertiana Dougl.) ≈ white fir (Abies concolor (Gord. & Glend.) Lindl.). To describe the influence of openings size on seedling height, we use an information-theoretic approach to select from competing models that predicted fifth-year height from group selection opening size. Asymptotic fits (modeled with MichaelisMenton curves) were selected for giant sequoia, ponderosa pine, sugar pine, and incense-cedar. Quadratic fits were selected for white fir and Douglas-fir. Linear models predicting increasing growth with opening size were consistently ruled out for all species. Although a marked depression in seedling-height growth occurred along the edges within the openings, mean annual radial increment of the 90-year-old border trees surrounding the openings increased by 30%, compared with other canopy trees in the forested matrix between openings.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
    Publication Date: 2018-01-01
    Description: Forest harvesting can impact site quality by removing essential nutrients, exacerbating the effects of historic base cation losses associated with acid deposition. We studied the 30-year trajectory of forest recovery from clearcutting (whole-tree harvest (WTH)) in a forest originally dominated by sugar maple (Acer saccharum Marsh.). At both the watershed scale (21.9 ha) and the “detailed” plot scale (1 m2), a dramatic decline of sugar maple was observed, along with maintenance of American beech (Fagus grandifolia Ehrh.) and an increase in birch, mainly yellow birch (Betula alleghaniensis Britt.). Many of the “detailed” plots where sugar maple failed to recruit became unoccupied rather than being “won” by another species. The decline of sugar maple was most severe in the upper elevation zones of the watershed, where low base status (especially Ca) of the soils was a likely driver. The results support previous studies indicating that regeneration by sugar maple is severely compromised on base cation depleted soils. Lower survival of seedlings for sugar maple emphasized the importance of maintaining advance regeneration to favor desired species such as sugar maple. Foresters should consider that sites with low base saturation and exchangeable Ca are likely to exhibit regeneration failure for sugar maple in the long term, even those with initial dominance by this species.
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    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 9
    Publication Date: 2007-03-01
    Description: We examined mortality of Abies concolor (Gord. & Glend.) Lindl. (white fir) and Pinus lambertiana Dougl. (sugar pine) by developing logistic models using three growth indices obtained from tree rings: average growth, growth trend, and count of abrupt growth declines. For P. lambertiana, models with average growth, growth trend, and count of abrupt declines improved overall prediction (78.6% dead trees correctly classified, 83.7% live trees correctly classified) compared with a model with average recent growth alone (69.6% dead trees correctly classified, 67.3% live trees correctly classified). For A. concolor, counts of abrupt declines and longer time intervals improved overall classification (trees with DBH ≥20 cm: 78.9% dead trees correctly classified and 76.7% live trees correctly classified vs. 64.9% dead trees correctly classified and 77.9% live trees correctly classified; trees with DBH 
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 10
    Publication Date: 2016-05-01
    Description: In the western United States, forests are experiencing novel environmental conditions related to a changing climate and a suppression of the historical fire regime. Mixed-conifer forests, considered resilient to disturbance due to their heterogeneity in structure and composition, appear to be shifting to a more homogeneous state, but the timescale of these shifts is not well understood. Our objective was to assess the effects of climate and fire suppression on stand dynamics and demographic rates of an old-growth mixed-conifer forest in the Sierra Nevada. We used a Bayesian hierarchical analysis to quantify species and community rates of recruitment, growth, and mortality. Despite a warming climate, we found that stand density, basal area, and carbon have increased over 56 years. Fir recruitment and growth significantly exceeded the community-level median rates, whereas pine recruitment and growth was significantly lower than the community-level median rates. Shifts in species composition from a well-mixed stand to a more dense fir-dominated stand appear to be driven by low growth and recruitment rates of pines relative to firs. In forests such as these with consistent and relatively low mortality rates, we recommend that restoration and management activities be focused on promoting pine recruitment and growth.
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    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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