Balsam Fir Forest Research Articles

Application of a snow cover energy and mass balance model in a balsam fir forest

The objective of this study was to adjust the parameters of the point energy and mass balance model of a snow cover developed by E. Anderson in 1976 when applied to a balsam fir forest. This physically based model was used to simulate the snow cover energy and mass balance during spring at Lac Laflamme (47°N, 71°W). The calibration of the model was done with the physical properties of snow and hourly outflow observed at a snow lysimeter in 1985 and 1986; the validation was performed with the 1987 data. For the three seasons simulated, the model yielded accurate predictions, particularly of hourly and daily outflows. As expected, the forest canopy limits latent and sensible heat transfers to the snow cover because of its effect on wind speed. The prediction of outflow was almost insensitive to variations to the roughness parameter and to the critical Richardson number but was moderately sensitive to most parameters related to liquid water retention and transmission. Lack of fit between predicted and observed outflows, densities and temperatures at various levels in the snowpack occurred when ice layers or ice lenses were suspected to be present in the snow.

Forest-pest interaction dynamics: The simplest mathematical models

This paper is devoted to the investigation of the simplest mathematical models of non-even-aged forests affected by insect pests. Two extremely simple situations are considered: (1) the pest feeds only on young trees; (2) the pest feeds only on old trees. The parameter values of the second model are estimated for the case of balsam fir forests and the eastern spruce budworm. It is shown that an invasion of a small number of pests into a steady-state forest ecosystem could result in intensive oscillations of its age structure. Possible implications of environmental changes in forest ecosystems are also considered.

Simulation of snowmelt runoff pathways on the Lac Laflamme watershed

The contributions of subsurface and surface runoff to streamflow during snowmelt in a balsam fir forest located on a laurentidian upland watershed (Lac Laflamme) of Québec (47°N, 71°W) were determined with a hydrological model (HYFOR). Lysimeter and calculated snowmelt runoff at the base of the snowpack were used as an input to the model during the snowmelt periods of 1985, 1986, and 1987. The calculated values were obtained from a temperature index snow cover model. The initial simulations showed a poor ability to predict runoff. The soil porosity and hydraulic conductivity were modified to account for the ground frost effect. Simulations were substantially improved by reducing soil porosities by 31% and hydraulic conductivities by 53% of their original values measured under the frost free conditions. Surface flow volume, which lumps rapid through-flow and overland flow, computed with the calibrated model varied between 32 and 47% of the total volume for the three snowmelt periods. Because of the significant modifications of soil parameters necessary to obtain reasonable model performance, it is concluded that better field observations on soil hydrologic properties are needed to improve snowmelt runoff simulations.

Litter decomposition under snow cover in a balsam fir forest

In a subalpine balsam fir forest in Quebec, Canada, mass losses, respiration rates, and nitrogen and sulphur dynamics were measured on fir needles, birch leaves, lichens (mixed species), and small twigs decomposing under deep (> 1.5 m) winter snow for 6 months. Mass losses ranged from <6% (twigs) to 70% (lichens) and relative decomposition rates of needles and leaves were reversed from those expected at higher temperatures. Isolation of fir needles from direct contact with the snow did not affect decay rate, nor was decay accelerated by spring snowmelt. In situ respiration rates increased from about 1 mg CO2/(g∙day)) in February to 3–5 mg CO2/(g∙day)) in May, mostly because of rising temperatures. Summer respiration rates were much higher (> 6 mg CO2/(g∙day)). Nitrogen and suphur concentrations increased in all nonwoody litter over winter, but only birch leaves and some fir needles appeared to assimilate nutrients from the environment. Melting snow could easily have provided all of the nitrogen and sulphur taken up by decomposing litter. Decomposing lichens released 40 and 60%, respectively, of their initial nitrogen and sulphur contents. A literature review indicates mass losses from leaf litter decomposing under deep snow vary according to the proportion of labile material in the litter and usually constitute 40–60% of total first-year mass losses. Key words: decomposition, winter, balsam fir, snow.

Factors controlling throughfall chemistry in a balsam fir canopy: A modeling approach

This paper presents a model of water flux and throughfall concentrations of K+ and NH 4 + in a subalpine balsam fir forest. The model is based on a multi-layer submodel of hydrologic flow. Cloud water deposition and evaporation are incorporated as separate submodels. Chemical exchange is parameterized with diffusion resistances and internal foliar concentrations determined from leaching experiments on isolated canopy components. The model is tested against within-storm throughfall measurements and found to agree reasonably well in most instances. Some specific departures from observed data are noted, of which some can be explained. Differences between observed and modeled concentrations of K+ early in the storm events suggest that pre-storm conditions, which were not modeled, are important in controlling the chemical exchange. Responses of throughfall chemistry to changes in rain rate, rain concentration, and stand surface area index (SAI) were investigated by simulation with the model. Increasing rain rates increased leaching of K+ and uptake of NH 4 + . Increasing concentrations of K+ in rain decreased slightly the amount of K+ leached, but increasing concentration of NH 4 + in rain increased NH 4 + uptake proportionately. Increasing canopy SAI increased the leaching of K+ and the uptake of NH 4 + , with the pattern of the increase dependent on rain rate.

Factors controlling the chemical alteration of throughfall in a subalpine balsam fir canopy

Rainfall and throughfall (TF) at four canopy levels were collected sequentially during four storms in a subalpine balsam fir forest on Mount Moosilauke, New Hampshire. The chemical compositions of throughfall (TF) and “net TF” (rainfall concentrations subtracted from TF concentrations) were compared with precipitation chemistry, amounts and intensities. Net TF fluxes of ammonium, nitrate, hydrogen, potassium and sulfate ions were influenced by concentration gradients between TF and the canopy. For ions taken up by the canopy, there was less uptake at lower rainfall concentrations, and for those released, there was less loss at higher rainfall concentrations. For all these ions, the effect of concentration gradients between surface water and canopy component internal pools was also suggested by the fact that most of the release (or uptake for ammonium and nitrate) occurred on components located high in the canopy. On these components, concentration differences between TF and canopy component internal pools should be greatest. Next TF concentrations of ammonium and nitrate approached zero with cumulative precipitation, indicating that the mechanisms through which the canopy takes up these ions became saturated. Diffusion driven by concentration gradients between TF at canopy surfaces and the interiors of foliage and other canopy components is consistent with these observations. Hydrogen and potassium ions were released to TF water from canopy component surfaces. These losses from canopy components declined with cumulative precipitation, apparently by depletion of internal sources of ions. Sulfate ions were also apparently always released by this canopy to throughfall, and sulfate is the only ion considered in this study which showed a positive effect of rainfall intensity on the magnitude of ionic release from canopy components.

Hydrologic soil properties and application of a soil moisture model in a balsam fir forest

An analysis of hydrologic soil properties and the prediction of volumetric soil water content during four summers have been done for a site located in the balsam fir (Abiesbalsamea (L.) Mill.) forest of the Lac Laflamme watershed. The hydrologic properties were used to identify three different soil layers, THIRSTY, a soil moisture model using the Penman evapotranspiration formula, was applied to predict daily volumetric water content of these layers. Predictions of soil moisture with the calibrated model were close to the observed data for the median layer (20–60 cm from the soil surface) and less accurate for the surface layer (0–20 cm) where important transpiration activities take place. The model appeared unreliable for predicting soil water content of the bottom layer (60–100 cm) which was often saturated by groundwater. The calibration of the model required modifications of the observed values of the available water content at field capacity and the relative root density factor and was adjusted with the crop coefficient of the Penman evapotranspiration formula. These modifications of observed physical parameters raise the question of the feasibility of extrapolating the model to other sites without extensive calibration. The high sensitivity to variations of the crop coefficient applied to the evapotranspiration equation indicated that a more physically based transpiration model, supported by field-oriented process studies, would be required to improve the model's performance.

The Potential Role of Rime Ice Defoliation in Tree Mortality of Wave- Regenerated Balsam Fir Forests

(1) Overstorey mortality occurs rapidly and synchronously within the dieback zones of subalpine, wave-regenerated balsam fir (Abies balsamea (L.) Mill.) forests (fir waves) of the north-eastern United States. (2) Reductions in leaf area associated with dieback zone formation may cause increases in within-canopy windspeeds and rime ice deposition rates during winter storms, resulting in further foliage loss. (3) Field measurements in a fir wave on Mt Moosilauke, New Hampshire, U.S.A., showed that rime ice deposition during winter storms and cumulative winter needle litterfall were greatest in the dieback zone. (4) One-year-old foliage had 56%, lower photosynthetic capacity than current-year foliage. (5) Using reasonable assumptions, it was estimated that during the course of a single winter, the loss of stand-level potential photosynthetic capacity increased from 2 1 %/, in a 13-year-old sapling stand to 7 5%/o in a 75-year-old dieback zone stand. (6) Repeated defoliation each winter may contribute to tree death by reducing wholetree photosynthetic capacity.

Communities of ground‐living spiders in six habitats on a mountain in Quebec, Canada

Ground‐living spiders were studied, using pitfall traps, in six habitats between 580 and 960 m (deciduous forest, fir forest, forest‐line and three alpine mountain top sites) on Mont du Lac des Cygnes. Altogether 88 species of spiders were found during the study summer (June‐mid‐September 1985), of which 51 belonged to Linyphiidae (s. lat.), 9 to Lycosidae and 8 to Gnaphosidae. The highest species number and diversity were found in the forest‐line habitat, the highest individual number on the main summit and the lowest in deciduous forest, the lowest site. Lycosidae and Gnaphosidae species and individuals characterized the alpine habitats. Linyphiidae (especially Linyphiinae) the forested sites and Amaurobiidae and Agelenidae the deciduous forest site. Erigoninae occurred commonly at all sites; their individual numbers were very high at coniferous forest sites. The dominant species in all three alpine habitats was Pardosa concinna, on the forest‐line Hybocoptus gibbosus, in balsam fir forest Sisicottus montanus and in deciduous forest Amaurobius borealis. The material included several (sub)arctic‐alpine species.

Trajectory analysis of forest canopy effects on chemical flux in throughfall

Short interval sampling of precipitation inputs and stem flow-throughfall (SF-TF) outputs was conducted in a subalpine balsam fir forest to analyze the controls on canopy ion flux. A canopy hydrology model was used to separate the effects of abiotic and biotic processes. The time lag between precipitation inputs and SF-TF outputs caused by the storage of water in the canopy required that time-course patterns of SF-TF flux be examined graphically. The resulting trajectory analyses disclosed patterns from which we generalized about canopy processing of precipitation inputs. Changes in the ion concentration gradient across canopy tissue surfaces appeared to be an important factor in regulating the rate of flux of ions between canopy tissues and SF-TF. These changes were in turn determined by changes in such factors as apoplast ion concentrations and the residence time of water in the canopy. These generalizations permit qualitative predictions of SF-TF flux in other canopies over time based on only rudimentary knowledge of canopy structure and function.

Changes in biomass components through stand development in wave-regenerated balsam fir forests

Available data on the wave-regenerated Abiesbalsamea forests of the northeastern United States are synthesized into a model (BALSAM) which predicts changes in total and component biomass through the disturbance–regeneration cycle. Measured decay rates seem to imply a higher mean forest floor mass than is actually observed, so several alterations were made in the initial model to make it predict forest floor mass correctly. With or without these changes, forest floor mass decreases for about 12 years after disturbance, largely owing to low levels of litterfall in the early stages of stand development. Because changes in living biomass and dead bole mass through the disturbance cycle roughly cancel each other out, net ecosystem productivity closely parallels these litterfall-driven changes in the forest floor. Throughout the disturbance–regeneration cycle, the forest floor is derived primarily from woody tissue and its decay products, with foliage-derived material making up less than 25% of the total forest floor mass.

Effects of Spruce Budworm Outbreaks on the Productivity and Stability of Balsam Fir Forests

Effects of spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on the productivity and stability of forests in eastern Canada are reviewed and discussed. Defoliation results in reduced growth of trees, widespread tree mortality, and loss of wood production, and thereby causes major forest management problems. At present, the only feasible method for limiting damage and losses from budworm outbreaks over large areas is to apply chemical or biological insecticides periodically to kill larvae and protect the forest from defoliation and tree mortality. Although budworm outbreaks definitely disrupt the wood-producing capacity of forests (or the short-term "stability of forests for human usage"), in terms of overall ecological stability, outbreaks apparently act as a cycling mechanism that allows advance fir-spruce regeneration to succeed the fir-spruce overstory.

Density, Biomass, Productivity, and Nutrient‐Cycling Changes During Stand Development in Wave‐Regenerated Balsam Fir Forests

Regeneration waves in the high—altitude fir forests of the northeastern United States create a gradient of stands of different ages that are ideal for research on forest developmental processes. Changes in density, biomass, productivity, litterfall, and nutrient content of the vegetation over the course of stand development were documented in a series of these stands on Whiteface Mountain, New York. After a regeneration wave passes through an area and the overstory dies, formerly suppressed seedlings are released, and stand density increases to 10—13 trees/m2 at about age 10 (counting only stems over 25 cm tall). Stand density then begins to decrease, at first slowly but then more rapidly, with a maximum mortality rate of 20—25% yr between years 20 and 30. Thereafter mortality continues, but the rate decreases over time to ≈4% yr at age 55. After about age 20 the relationship between stand age and stand density is p = 0.04 · exp(115/AGE). For stands that have begun to self—thin, the relationship between stand age and stand density and mean aboveground tree mass is log10 m = 3.94 — 1.24 log10p, with a slope significantly different from —1.5. Basal area (measured at 25 cm) increases for the first 15—20 yr of stand development, then remains constant at 60—70 m2/ha for the remainder of the life of the stand. Total aboveground biomass of a mature fir stand is ≈11.8 kg/m2 (1.5 kg/m2 foliage, 1.7 kg/m2 branches, 0.9 kg/m2 bole bark, and 7.7 kg/m2 bole wood). The biomass accumulation rate is highest during the first decade of stand development (320 g · m—2 · yr—1), and declines to ≈115 g · m—2 · yr—1 for a 55—yr—old stand. Foliage biomass increases rapidly during the first 10—15 yr of stand development, then remains constant after crown closure. Branch biomass increases until about age 15, declines for about a decade, then increases again for the rest of the life of the stand. Bole bark increases until about age 30, then stabilizes. Bole wood continues to increase throughout the life of the stand. Aboveground net primary productivity for a mature stand is 960 g · m—2 · yr—1 (foliage, 380 g · m—2 · yr—1; twigs, 150 g · m—2 · yr—1; branch wood and bark, 170 g · m—2 · yr—1; bole bark, 25 g · m—2 · yr—1; and bole wood, 235 g · m—2 · yr—1). Productivity remains generally constant as the stand develops, but in the early stages almost 45% of the total aboveground production is devoted to producing bole wood and bark, while in a mature stand this proportion drops to ≈25%, with the remainder going to foliage and branch wood production. There is thus a shift from production of boles to branches as the stand ages. This may reflect a shift in the primary stresses on the trees, from intraspecific competition in the younger stands to physical environmental factors (e.g., wind abrasion and rime formation) in the older stands. After the initial increase, woody tissue respiration remains approximately constant throughout the life of the stand, as an increase in the size and height of boles is balanced by death of small trees and a decrease in total bole surface area. A mature fir stand contains nitrogen, potassium, magnesium, and calcium in the amounts 47.7, 18.1, 4.6, and 30.4 g/m2, respectively. All these nutrients accumulate rapidly in the early stages of stand development as the stand accumulates nutrient—rich foliage. This is particularly true for nitrogen; a 9—yr—old stand contains half as much nitrogen as a 60—yr—old one. However, the difference between nutrient uptake by the trees and nutrient release in decomposition is greatest somewhat later in stand development, when the pulse of litter accompanying stand die—off has decomposed but the young stand is still taking up significantly greater quantities of nutrients than it is returning in litterfall. Thus if ecosystem nutrient losses are controlled by nutrient accumulation in living biomass, the period of maximum nutrient conservation should occur in the years immediately after disturbance, when the stand is accumulating nutrients most rapidly. If the critical factor is the balance between uptake and release, then minimum losses should occur later. Increased meteorologic inputs of nitrogen and acid in the high—altitude fir forests may have altered the natural nutrient cycles of the preindustrial era.

Rates and mechanisms of cloud water deposition to a subalpine balsam fir forest

A resistance model for deposition of cloud droplets to a balsam fir forest canopy is described. The model accounts for impaction and sedimentation of cloud droplets, as well as evaporation and condensation of cloud water on canopy surfaces. It considers multiple height strata in the canopy, seven canopy component types in each stratum, and three size classes of cloud droplets. The model was tested against field data and was found to predict cloud water deposition rates in good agreement with measured values. Analysis of the model shows that in the windy, subalpine zone of New England for which the model was developed, advected cloud water can be deposited at rates on the order of tenths of a millimeter per hour, with deposition velocities ranging from 1 to 80 cm s −1. Most of the cloud water deposition takes place in the top 3 m of the canopy. Inertial impaction is the dominant deposition mechanism, but sedimentation can be important at low wind speeds and in the interior of the canopy. Increases in wind speed cause increased deposition via impaction and decreased deposition via sedimentation.

Effects of canopy components on throughfall chemistry: An experimental analysis.

Five canopy components of subalpine balsam fir forests (branches with young needles, branches with old needles, non-foliated twigs, lichen-covered twigs, and boles) were treated with simulated rain to test the influence of these components on throughfall and stemflow chemistry. Effects on the fluxes of potassium, sodium, hydrogen, sulfate, nitrate and ammonium ions by the canopy components were tested in relation to rain application rate, duration of rain, and time since the last rain. Interactions between ionic behavior and components were complex. In general, the ionic behavior ranged from high levels of net efflux to mixed influx-efflux to high levels of influx in the order: sulfate, potassium, sodium, nitrate, hydrogen, ammonium. In cases in which application rates produced significantly different results, net flux rates increased with application rate. Branch components mostly ranged from low flux rates (either influx or efflux) to high rates according to the order: young needles<old needles<twigs<lichencovered twigs.

Canopy processing of acidic precipitation by coniferous and hardwood forests in New England.

There are several important factors that may influence how forest canopies interact with acidic deposition, including forest community species composition, phenological status, and differences in atmospheric loading of strong acids. Results from comparative throughfall chemistry studies in New Hampshire, where precipitation pH is 4.1, indicate that northern hardwood canopies produce a throughfall solution chemistry that is less acid and higher in basic cations than either direct precipitation or throughfall solutions derived from nearby subalpine balsam fir forests. Neutralization of acid precipitation in the hardwood canopy appears to occur through two major processes: ion exchange removal of free H+ by the foliage, and Brønsted base leaching from the plant canopy. Data obtained during the period of senescence preceding leaf-drop suggest a strong link between alkalinity release and potassium leaching in the hardwood canopy. Compared with the hardwood canopy, the coniferous forest canopy exhibits several distinct quantitative differences in canopy processing.

Evolution Debate

In the report "Cloud droplet deposition in subalpine balsam fir forests: Hydrological and chemical inputs" by G. M. Lovett et al. (24 Dec., p. 1303), two errors appeared in Table 2 on page 1304. The cloud deposition of SO(4)(2-), incorrectly reported as 275.8 kg ha(-1) year(-1), should have been 137.9 kg ha(-1) year(-1). The percentage of the sum contributed by clouds, reported as 81 for SO(4)(2-), should have been 68.

Erratum: Cloud Droplet Deposition in Subalpine Balsam Fir Forests: Hydrological and Chemical Inputs

In the report "Cloud droplet deposition in subalpine balsam fir forests: Hydrological and chemical inputs" by G. M. Lovett et al . (24 Dec., p. 1303), two errors appeared in Table 2 on page 1304. The cloud deposition of SO 4 2- , incorrectly reported as 275.8 kg ha -1 year -1 , should have been 137.9 kg ha -1 year -1 . The percentage of the sum contributed by clouds, reported as 81 for SO 4 2- , should have been 68.

Protein binding phenolics and the inhibition of nitrification in subalpine balsam fir soils

Nitrification in a highly active Al horizon of a balsam fir forest floor soil can be greatly inhibited by an aqueous methanol extract of the forest floor. This extract was fractionated in an attempt to identify the compounds responsible for the inhibition. Condensed tannins, smaller molecular weight phenolics, and their distribution on particulate matter in the extract were the most important inhibiting components of the extract. When all phenolic material was removed from the extract, the remaining solution stimulated nitrification.

Nitrification in subalpine balsam fir soils: Tests for inhibitory factors

Previous work has shown that nitrification is negligible in floors of subalpine balsam fir forests but proceeds vigorously in the Al horizon beneath the forest floor. This paper describes a series of experiments designed to determine the causes for lack of NO − 3 production in the forest floor. These experiments showed that denitrification was not important and that autotrophic nitrifiers were present. Increases in pH, essential nutrients and inoculum did not enhance nitrification, indicating that an inhibitor rather than a limiting factor was involved. Analysis of forest floor and Al showed that aluminum was present at concentrations greater than those found to inhibit nitrification in culture. Since the Al was actively nitrifying, it seemed unlikely that aluminum was responsible for nitrification inhibition in the forest floor. Finally, a methanol extract of polyphenols from the forest floor was added to the Al significantly reducing nitrification. These experiments suggest that the higher phenolic concentrations are responsible for inhibition of nitrification in the forest floor.