Peter F. Newton

Stand density management diagrams: Review of their development and utility in stand-level management planning

Abstract Stand density management diagrams (SDMDs) are average stand-level models which graphically illustrate the relationships between yield, density and mortality throughout all stages of stand development. SDMDs are primarily used to derive density control schedules by management objective and have been developed for numerous, commercially important species, throughout the world. Historically, SDMDs were initially developed by Japanese scientists in the early 1960s. The principal elements of these initial diagrams included size-density relationships representing crown closure, minimum and maximum self-thinning conditions and yield isolines derived from the reciprocal equation of the competition-density effect. During the 1970s and 1980s various modifications to the original modelling approach were proposed including the replacement of the reciprocal equations with empirical-based volume-density functions, employing different relative density indices and size variates, and incorporation of forest production theories. During the early to mid-1990s, SDMDs were developed for a number of additional species employing earlier modelling approaches, including the development of SDMDs for mixed species stands. The objective of this study was to chronologically review the historical development and associated applications of SDMDs in stand-level management planning.

A decision-support system for forest density management within upland black spruce stand-types

The objective of this study was to develop an enhanced modular-based structural stand density management model (SSDMM) and associated algorithmic analogue for upland black spruce (Picea mariana (Mill) BSP.) stand-types situated within the central portion of the Canadian Boreal Forest Region. For a given density management regime, site quality, rotation age, stock-type, cost structure and set of merchantability standards, the hierarchical-based SSDMM enabled estimation of the following metrics: overall productivity (e.g., mean annual volume, biomass and carbon increments), volumetric yields (e.g., total and merchantable volumes per unit area), log-product distributions (e.g., number of pulp and saw logs by diameter class), biomass production and carbon sequestration outcomes (e.g., oven-dried masses of above-ground components and associated carbon equivalents by diameter class), recoverable end-products and associated monetary values (e.g., volume and economic value of recovered chip and dimensional lumber products by diameter class and sawmill-type (stud and randomized length processing protocols)), and fibre quality attributes (e.g., maximum branch diameter and wood density). The core modules which were responsible for describing stand dynamics and structural change were developed using 407 (122 from natural stands and 285 from managed stands) temporal tree-list measurements obtained from 269 (142 in natural stands and managed 127 in managed stands) sample plots (note, natural stands are those that naturally regenerated following a stand-replacing disturbance and have no history of density regulation whereas managed stands are those that naturally or artificially regenerated following a stand-replacing disturbance and have a history of density regulation). The modules responsible for predicting log product distributions, and end-product volumes and values, were developed employing relationships derived from taper and sawmill simulation studies. The modules responsible for predicting biomass and carbon outcomes, and log and fibre quality attributes, were developed using data obtained from initial espacement and thinning experiments. The resultant model introduces a number of advancements over its predecessors including those that (1) ensured mathematical compatibility among yield estimates, (2)?accounted for intrinsic density-independent mortality factors, response delay following thinning, and genetic worth effects, and (3) provided increased flexibility in terms of enabling end-users to change merchantability standards, specify product degrade factors, and adjust cost profiles, according to their unique requirements. As demonstrated, the decision-support model can assist in facilitating the transformative shift towards the production of high value end-products, bio-energy feed stocks, carbon credits, and ecosystem services, currently underway within the Canadian forest sector. Highlights? An enhanced modular-based structural stand density management model for upland black spruce stand-types is developed. ? New analytical solutions for accounting for response delay following thinning and genetic worth effects are provided. ? Utility of the model in designing crop plans for both natural and managed stand-types is demonstrated. ? This decision-support system facilitates the transformative shift towards a value-based management proposition.

Inhibition of black spruce seedling growth by forest-floor substrates of Central Newfoundland.

Abstract The objective of this study was to determine if seedbed substrates consisting of F and H organic matter and Ae and Bf mineral material inhibited seed germination and subsequent seedling growth of black spruce. The study was conducted with seedbed substrates collected from eight pure blackspruce stands of four age classes (15, 30, 45 and 60 years) in central Newfoundland. No significant effect on percentage germination or primary shoot growth of seedlings was obtained when grown on F and H organic matter, Ae and Bf mineral material. However, growth and development of primary roots was significantly reduced in the F and H organic matter and Ae mineral material compared to the controls (washed sand). The inhibitory effect increased with stand age. The affected seedlings did not produce normal primary roots with root hairs. The primary root cells of the affected seedlings were significantly broader and shorter compared to the control seedlings. Mineral material from the Bf horizon did not have any significant effect on primary root growth of black spruce seedlings.

Diameter distributional trends within mixed black-spruce/balsam-fir and pure black-spruce stand types

Abstract This study describes and compares (i) the diameter distribution of black spruce (Picea mariana (Mill.) B.S.P.) and balsam fir (Abies balsamea (L.) Mill.) within mixed black-spruce/balsam-fir stands, and (ii) the diamter distribution of black spruce within pure stands, at various stages of stand development. Employing relative-frequency diameter-class data from 128 0.081-ha semi-permanent sample plots located in natural mixed (57 plots) and pure (71 plots) stand types of central insular Newfoundland, 1st, 2nd, 3rd and 4th-order polynomial functions were used to describe stand structure at various species heights. The Chi-square statistic was used to compare distributions within and between stand types by height class. Results indicated that both species within mixed stands, and black spruce within both stand types, had similar distribution trends, i.e., initially reverse J-shaped or positively-skewed unimodal distributions progressing to a semi-bimodal or positively skewed mound-shaped distribution. Black spruce occupied a slightly greater proportion of the larger diameter classes, whereas balsam fir occupied a slightly greater proportion of the smaller diameter classes, indicating a semi-stratified structure.

An integrated approach to deriving site-specific black spruce regeneration standards by management objective

Abstract The objectives of this study were to develop and subsequently demonstrate a mathematical compatible approach for deriving site-specific regeneration standards by yield objective for use in black spruce (Picea mariana (Mill.) B.S.P.) management. The approach quantitatively links mean point-density estimates derived from regeneration surveys to future yields through the use of a stand density management diagram (SDMD). Specifically, the SDMD was used as a simulation model to derive periodic yield estimates for quadratic mean diameter, mean volume and merchantable volume for a range of initial density and site conditions commonly observed within naturally regenerating black spruce seedling populations. Yield prediction equations were developed employing mean point-density and dominant height as independent variables and subsequently summarized within a graphical, functional and algorithmic framework. The practical utility of the approach was demonstrated by considering regeneration assessment situations commonly encountered in operational settings: (1) estimating site-specific yields at rotation age given mean point-density estimates, and conversely, (2) determining site-specific mean point-density values required to attain specified yield objectives at rotation age. Although the operational utility of the approach is restricted to central insular Newfoundland due to data base limitations, the concepts and analytical framework underlying the approach are of general applicability.

Systematic review of yield responses of four North American conifers to forest tree improvement practices

The objective of this review was to summarize the expected yield gains of black spruce (Picea mariana (Mill.) B.S.P.), jack pine (Pinus banksiana Lamb.), white spruce (Picea glauca (Moench) Voss) and red pine (Pinus resinosa Ait.), to correct provenance-progeny selection, first generational selection strategies and second generational selection strategies, based on a systematic assessment of the scientific literature. The procedure consisted of four sequential steps: (1) searching electronic databases for relevant forest tree improvement studies employing a meta-analytical protocol; (2) attaining and assessing the identified publications for their specific applicability; (3) collating the results of the resultant study subset in terms of relative height growth gains; and (4) estimating rotational consequences in terms of merchantable productivity via prediction models. The results of the systematic search indicated that documented long-term yield responses to tree improvement were paucity in nature. Specifically, the majority of the published studies consisted of short-term results pertaining to provenance-progeny experiments. Furthermore, studies reporting yield responses to first and second generational selection strategies were practically non-existent. Consequently, expert opinion and unpublished preliminary results derived from ongoing tree improvement experiments were used to augment the limited published information available for these selection strategies. Overall, the results indicated that correct provenance-progeny selection could yield juvenile height growth gains of approximately 15% at 15 years for black spruce, 7% at 21 years for jack pine, 12% at 20 years for white spruce and 8% at 15 years for red pine. Corresponding merchantable productivity (mean annual merchantable volume increment) gains at rotation (50 years) for plantations established at nominal initial densities on medium-to-good quality sites were approximately 17, 15, 26 and 7%, respectively. Preliminary estimates derived from individual case-studies indicated that (1) first generational selection strategies could increase merchantable productivity by approximately 13% at 50 years for black spruce, 28% at 40 years for jack pine, and 20% at 45 years for white spruce, and (2) second generational selection strategies could increase merchantable productivity by approximately 31% at 50 years for black spruce.

Stand density management decision-support program for simulating multiple thinning regimes within black spruce plantations

The utility of currently available software programs for use in black spruce, Picea mariana (Mill.) B.S.P., density management is becoming limited due to the increasing complexity of treatments. Consequently, the objectives of this study were to develop and subsequently demonstrate a decision-support program for stand density management involving multiple thinning treatments applicable to plantations established in Ontario, Quebec, New Brunswick and Newfoundland. The resultant PC-based program enables forest managers to predict 75-year size-density trajectories for three density control regimes simultaneously, given a common planting density. Specifically, the program: (1) graphically illustrates the expected site-specific trajectories for each regime within the context of a stand density management diagram; (2) calculates and tabulates annual, treatment-specific and cumulative rotational yield estimates and associated performance indices for overall productivity, relative product value, and degree of optimal site occupancy; and (3) graphically illustrates production curves for volumetric yield and product size. Additionally, instructions on acquiring an executable version of the program via the Internet are included.

Evaluation of sampling design on taper equation performance in plantation-grown Pinus banksiana

Abstract The objective of this study was to determine empirically the optimum disk selection protocol when calibrating (1) the dimensional compatible variable-exponent taper equation, (2) the segmented polynomial taper equation, and (3) the modified variable-exponent taper equation, for plantation-grown jack pine (Pinus banksiana Lamb.) trees. Analytically, the full data set, consisting of 187 trees randomly selected within 21 jack pine plantations situated within the Canadian Boreal Forest Region, was randomly subdivided into calibration (parameterization) and validation (performance) subsets of approximately equal size. Based on prediction lack-of-fit indices (positional and tree-level absolute and relative mean biases in inside-bark diameter, cross-sectional area and total stem volume), the results indicated that the performance of the dimensional compatible and segmented equations was approximately equivalent among the 16 protocols evaluated (combinations of four above breast-height percentage-height sampling schemes with four below breast-height fixed-height sampling schemes). Conversely, the modified variable-exponent equation was strongly influenced by disk selection protocol, with the 10% sampling intensity combined with disks selected at 0.15, 0.5, 0.9 and 1.3 m being the most efficient. In summary, the results of this study suggest that the empirically derived modified variable-exponent equation was more data sensitive than the functionally derived dimensional compatible and segmented equations, when calibrated for plantation jack pine trees.

Temporal size-dependent growth responses within density-stressed black spruce stands: Competition processes and budworm effects

Abstract This study assessed temporal size-dependent growth response patterns within 18 density-stressed black spruce ( Picea mariana (Mill.) B.S.P.) stands situated on medium quality sites in central insular Newfoundland. The assessment employed a power function to analyze the relationship between mean annual stem volume increment and cumulative size. Parameters of the power functions were interpreted in terms of: (1) their expression of alternative modes of competitive interaction, according to potential interactions by either resource depletion or resource pre-emption; and (2) temporal size-dependent responses relating to an epidemic spruce budworm ( Choristoneura fumiferana Clem.) infestation that occurred within the study area during the late 1970s. The results derived from the relationships did not allow alternative modes of competitive interaction to be distinguished due to the low levels of statistical power associated with parameter estimates. However, the analysis did reveal the effects of budworm defoliation on competitive dynamics within the sampled stands. Five distinct phases of response to budworm were revealed as follows: (1) competition-induced, size-proportional, growth rate declines among all-sized individuals during the pre-defoliation period ( 1985). These patterns suggest that the principal effect of budworm defoliation was to increase competitive asymmetry within the sampled stands, thereby increasing the likelihood of episodic competition-induced mortality events.

Stem analysis program for coniferous forest tree species

The objectives of this study were to describe and demonstrate a PC-based stem analysis program applicable to coniferous forest tree species. From annual ring-width xylem sequences obtained from cross-sectional samples located at multiple stem heights, the program computes: radial and longitudinal ring-width sequences, apical growth increments, sectional and cumulative volume production patterns, and stem developmental profiles. Computations are based on the following geometric assumptions: (1) the stump, tip and sections in between are treated as geometric solids of revolution resembling a cylinder, cone, and frustum of a cone, respectively; and (2) for sections in which increments are not continuous throughout, computations are based on a geometric solid of revolution resembling a cone. The program corrects for slant-based sectional length measurements using the Pythagorean theorem and eliminates the need to externally predict height for a given age via a linear interpolation procedure. The utility of the program is demonstrated via a comparison of the longitudinal radial growth patterns of jack pine, Pinus banksiana Lamb., trees that developed under different density management regimes.