bluuebunny/crossref_metadata_2025 huggingface dataset:
Bivariate Distribution Modeling with Tree Diameter and Height Data
Authors: Wang Mingliang , Rennolls Keith
Published: April 2024

The Logit-Logistic (LL), Johnson's SB, and the Beta (GBD) are flexible four-parameter probability distribution models in terms of the (skewness-kurtosis) region covered, and each has been used for modeling tree diameter distributions in forest stands. This article compares bivariate forms of these models in terms of their adequacy in representing empirical diameter–height distributions from 102 sample plots. Four bivariate models are compared: SBB, the natural, well-known, and much-used bivariate generalization of SB; the bivariate distributions with LL, SB, and Beta as marginals, constructed using Plackett's method (LL-2P, etc.). All models are fitted using maximum likelihood, and their goodness-of-fits are compared using minus log-likelihood (equivalent to Akaike's Information Criterion, the AIC). The performance ranking in this case study was SBB, LL-2P, GBD-2P, and SB-2P.
Incorporating Whole-Stand and Individual-Tree Models in a Stand-Table Projection System
Authors: Cao Quang V.
Published: April 2024

A stand table provides number of trees per unit area for each diameter class. This article presents three methods to project a current stand table into the future by predicting mortality and diameter growth for each diameter class by use of an individual-tree model. The stand table was then adjusted to produce the same total number of trees and basal area per hectare as predicted from the whole-stand model. The three methods evaluated in this study were stand table adjustment, constrained least squares (LS), and modified constrained LS. Data from the Southwide Seed Source Study of loblolly pine (Pinus taeda L.) showed that incorporating the individual-tree model helped improve the projection of stand tables, as compared to a previous approach. The three methods produced comparable results; error indices from these methods were within 5% of one another. The constrained LS method consistently provided the best fit (lowest error indices) as compared to the other methods.
Influence of Headwater Site Conditions and Riparian Buffers on Terrestrial Salamander Response to Forest Thinning
Authors: Rundio David E. , Olson Deanna H.
Published: April 2024

Although thinning of young, even-aged forests may accelerate the development of characteristics associated with mature forests, in the short term it may negatively affect some taxa, including terrestrial salamanders. Preexisting site conditions, including down wood, and forest management measures, such as riparian buffers, may moderate these effects, but these relationships are poorly understood. To explore whether down wood and riparian buffer widths might influence short-term responses to thinning, we sampled salamanders using ground searches before and during the first 2 years after experimental thinning at two 45- to 65-year-old headwater forest sites in western Oregon that differed in down wood volume. Prethinning distributions of terrestrial salamanders overlapped one- and two-tree height riparian buffers, and except for red-backed salamanders, overlapped very little with narrower streamside or variable-width buffers. At the site where down wood volume was low, captures of ensatina (Ensatina eschscholtzii Gray) and western red-backed salamanders (Plethodon vehiculum Cooper) both declined by 40% in thinned areas. In contrast, captures of ensatina and Oregon slender salamanders (Batrachoseps wrighti Bishop) were not significantly affected by thinning at the site where down wood volume was high. Our results suggest that site conditions, such as down wood volume, and riparian buffers may influence the effect of thinning on terrestrial salamanders, and demonstrate the tight linkage among management of aquatic, riparian, and upslope resources in headwater forests.
Mountain Pine Beetle Dispersal: The Spatial–Temporal Interaction of Infestations
Authors: Robertson Colin , Nelson Trisalyn A. , Boots Barry
Published: April 2024

An understanding of mountain pine beetle (Dendroctonus ponderosae Hopkins) dispersal during an outbreak is important for modeling future infestations and aiding management decisions. Data on the spatial pattern of red and green attacked trees were used to characterize the spatial–temporal nature of dispersal. Research goals were to detect evidence of dispersal based on the distance and direction between red and green attacked tree clusters, determine how dispersal changes at different stages of infestation, and to detect landscape variables influencing the observed dispersal patterns. Key variables explored were Biogeoclimatic Ecosystem Classification (BEC), topography, and the local population of susceptible hosts. Dispersal distances of 30 meters and 50 meters were consistently observed among different data subsets. Findings suggest that short-range dispersal often occurs despite an available population of susceptible hosts, and as the infestation grows in intensity, the abundance of dispersing beetles causes spot infestations to coalesce.
Evidence for Increasing Red Maple Abundance in the Eastern United States
Authors: Fei Songlin , Steiner Kim C.
Published: April 2024

Red maple (Acer rubrum L.) is widely believed to be increasing in abundance in eastern North America, but most evidence is anecdotal or localized. In this article we present analyses of FIA data sets designed to formally quantify changes in abundance of red maple in the eastern United States during the period of 1980 to 2005. The results indicate that recent increases in red maple abundance are almost ubiquitous on a state-by-state basis throughout the species' natural range and generally greatest in the western portions of the range. No states experienced a significant decrease in red maple abundance during this period. There is evidence that the species has naturalized into areas west of its putative pre-Columbian distribution. Red maple had an inverse “J” population structure, and density of red maple trees has increased in all diameter classes across the region. The trend of increasing red maple abundance will continue unless the circumstances that cause this phenomenon are changed.
Interactions of Elevation, Aspect, and Slope in Models of Forest Species Composition and Productivity
Authors: Stage Albert R. , Salas Christian
Published: April 2024

We present a linear model for the interacting effects of elevation, aspect, and slope for use in predicting forest productivity or species composition. The model formulation we propose integrates interactions of these three factors in a mathematical expression representing their combined effect in terms of a cosine function of aspect with a phase shift and amplitude that change with slope and elevation. This model allows the data to determine how the aspect effect changes with elevation and slope. Earlier articles concerning the interactions of slope, aspect, and elevation have been incomplete by either treating elevation as fixed or ignoring the possibility that aspect effect must also involve slope. The proposed set of variables is illustrated in four applications: (1) a hypothetical data set for probability of stocking by “species” having different adaptations to elevation, (2) in a discriminant function for forest/nonforest classification of data from Utah, (3) estimating mean annual increment of Utah forests, and (4) estimating the height asymptote in a mixed-model differential equation predicting Douglas-fir height growth.
Parameter Estimation of Base-Age Invariant Site Index Models: Which Data Structure to Use?
Authors: Wang Mingliang , Borders Bruce , Zhao Dehai
Published: April 2024

Two main approaches to estimating parameters of dominant height curves (derived by algebraic difference approach (ADA) and generalized ADA (GADA)), the dummy variable method and the difference approach (the error-in-variable (EIV) method along with ordinary least-squares (OLS) fits)are compared using second-rotation loblolly pine (Pinus taeda L.) data from a designed experiment. It was found that the EIV method consistently performed better than the dummy variable method, and the two unbiased estimation methods were not necessarily better than the biased OLS differencemethods. In general, the performance of these two approaches was similar in height prediction given site index, but in combination with site index prediction given heights, the difference methods generally performed better. The nonoverlapping forward difference data structure (III), is recommendedto fit difference models.
Rooting of Leafy Stem Cuttings of Baillonella toxisperma
Authors: Mpeck Marie Ngo , Atangana Alain
Published: April 2024

Rooting ability in Moabi was examined using 972 single-node leafy stem cuttings set in each of three blocks of a split-split plot experimental design in nonmist propagators. Each main plot contained three rooting media (sand, sawdust, and a 50:50 mixture of sand and sawdust), whereas three auxin types (indole-3-acetic acid [IAA], indole-3-butyric acid [IBA], and 1-naphthalene acetic acid [NAA]) and a control (alcohol) were tested at the subplot level. At the sub-subplot level, three leaf areas (25, 50, and 75 cm2) were investigated. Significant (P = 0.05) and nonsignificant substrate × hormone × leaf area interactions on rooting percentage were found at week 8 and during the rest of experiment, respectively. Significant sand versus sawdust × IBA versus IAA and NAA × quadratic components of leaf area interaction on rooting percentage was identified from week 10 to week 14 (P = 0.0462–0.038), and the highest rooting percentage (85.2 ± 7.24%) was found in 75 cm2 × IBA × sand-treated cuttings at week 14. Significant substrate × leaf area interaction on rooting percentage was observed throughout the experiment. Interacting substrate × leaf area significantly influenced the number of roots per rooted cutting at week 22. This study indicated that Moabi is amenable to vegetative propagation within 14 weeks.
An Alternative to Traditional Goodness-of-Fit Tests for Discretely Measured Continuous Data
Authors: Randolph KaDonna C. , Seaver Bill
Published: April 2024

Traditional goodness-of-fit tests such as the Kolmogorov-Smirnov and χ2 tests are easily applied to data of the continuous or discrete type, respectively. Occasionally, however, the case arises when continuous data are recorded into discrete categories due to an imprecise measurement system. In this instance, the traditional goodness-of-fit tests may not be wholly applicable because of an unmanageable number of ties in the data, sparse contingency tables, or both; therefore, a flexible alternative to goodness-of-fit tests for discretely measured continuous data is presented. The proposed methodology bootstraps confidence intervals for the difference between selected percentiles of the empirical distribution functions of two samples. Application of the approach is illustrated with a comparison of loblolly pine (Pinus taeda L.) tree crown density distributions at the 10th, 25th, 50th, 75th, and 90th percentiles simultaneously.
Preharvest Measurement of Marked Stands Using Airborne Laser Scanning
Authors: Peuhkurinen Jussi , Maltamo Matti , Malinen Jukka , Pitkänen Juho , Packalén Petteri
Published: April 2024

The customer-oriented wood procurement chain from forest to raw material user starts with a knowledge of stands available for harvesting and information on these marked stands. Despite several studies, no adequate method has been developed for obtaining preharvest measurement information to meet existing requirements. The aim here was to develop a method for the preharvest measurement of a marked stand based on single tree detection and airborne laser scanning. The trees were detected from high-density laser scanning data using automatic detection procedures, and their dbh was estimated using either local or regional models. The method was compared with actual harvester measurement of the stand and alternative methods for obtaining preharvest measurement information (systematic plot sampling, subjective inventory by compartments, and the laser canopy height distribution method). The comparisons of the methods were based on goodness-of-fit tests of diameter distributions and bucking simulations. The results indicated that the laser scanning-based single tree detection procedure has considerable advantages over other methods. The crucial point in applying the method seemed to be the choice of diameter prediction model.
Density Frontiers for Even-Aged Douglas-fir and Western Hemlock Stands in Coastal British Columbia
Authors: Montigny Louise de , Nigh Gordon
Published: April 2024

Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) and western hemlock (Tsuga heterophylla [Raf.] Sarg.) are the two most common and commercially important species on the coast of British Columbia, Canada. Our research focused on determining the relationship between maximum density and top height for pure stands of these species. These relationships can be used to provide a constraint on mortality functions in individual-tree growth and yield models for even-aged stands. Our data consist of density and top height from experimental plots established along the coast of British Columbia, Washington, and Oregon. These experiments yielded 2,930 observations from 628 plots. We fit stochastic frontier functions to the density/top height data. Stochastic frontier functions have a stochastic component that allows data points to lie on either side of the frontier. The fitting of the frontier functions using maximum likelihood estimation resulted in maximum density lines as an exponential function of top height for both species. The fitted model is based loosely on the −3/2 power thinning law. Our analysis shows that these relationships hold across sites with differing quality. The maximum density line is greater for western hemlock than for Douglas-fir up to a height of about 35 m, at which point they are almost the same. The higher maximum density of western hemlock is likely related to its greater shade tolerance. We used the growth-and-yield model Table Interpolation Program for Stand Yields (TIPSY) to simulate the growth of high-density stands of Douglas-fir and western hemlock. These simulations gave similar results to our fitted density frontier line.
Calcium Uptake, Partitioning, and Sinuous Growth in Douglas-Fir Seedlings
Authors: Littke Kim , Zabowski Darlene
Published: April 2024

Sinuosity is a growth deformation affecting Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and other conifers. Ca, an essential nutrient in tree growth and cell development, may be deficient in these stands and could be causing sinuous growth. An experiment was conducted to test whether low Ca availability causes sinuous growth in Douglas-fir seedlings. Douglas-fir 1 + 1 seedlings were grown in a greenhouse with high to low Ca availability. After 6 months of growth, the seedlings were measured for sinuosity and separated into new-needles, new-stem, old-needles, old-stem, and roots. High Ca fertilized seedlings had greater new-needle biomass and growth than low Ca fertilized seedlings. High Ca availability also led to higher Ca concentration and content, including higher foliar membrane-associated Ca, Ca-pectate, and Ca-oxalate than low Ca seedlings. Low Ca availability had no significant effect on sinuosity. Although high Ca availability did not alleviate sinuous growth in Douglas-fir seedlings, it did lead to higher growth, foliar biomass, and membrane-associated Ca.
The Interaction between Soil Nutrients and Leaf Loss during Early Establishment in Plant Invasion
Authors: Leger Elizabeth A. , Howe Katherine M. , Gurevitch Jessica , Woo Eliza , Hickman Jonathan , Ashton Isabel W. , Lerdau Manuel
Published: April 2024

Nitrogen availability affects both plant growth and the preferences of herbivores. We hypothesized that an interaction between these two factors could affect the early establishment of native and exotic species differently, promoting invasion in natural systems. Taxonomically paired native and invasive species (Acer platanoides, Acer rubrum, Lonicera maackii, Diervilla lonicera, Celastrus orbiculata, Celastrus scandens, Elaeagnus umbellata, Ceanothus americanus, Ampelopsis brevipedunculata, and Vitis riparia) were grown in relatively high-resource (hardwood forests) and low-resource (pine barrens) communities on Long Island, New York, for a period of 3 months. Plants were grown in ambient and nitrogen-enhanced conditions in both communities. Nitrogen additions produced an average 12% initial increase in leaf number of all plants. By the end of the experiment, invasive species outperformed native species in nitrogen-enhanced plots in hardwood forests, where all plants experienced increased damage relative to control plots. Native species experienced higher overall amounts of damage in hardwood forests, losing, on average, 45% more leaves than exotic species, and only native species experienced a decline in growth rates (32% compared with controls). In contrast, in pine barrens, there were no differences in damage and no differences in performance between native and invasive plants. Our results suggest that unequal damage by natural enemies may play a role in determining community composition by shifting the competitive advantage to exotic species in nitrogen-enhanced environments.
Variance Reduction for Radial Line Sampling Coverage Estimators
Authors: Lynch Thomas B.
Published: April 2024

It may be convenient to use radial line sampling for coverage estimates in small irregularly shaped areas. Radial line samples emanate from a fixed point located in the interior of the area and would be run according to a randomly selected azimuth. Thus, radial line sampling is analogous to techniques of local stereology, which considers quantitative aspects of spatial structures in the neighborhood of a central point. Coverage estimates from radial line sampling can be based on coverage observed on several sample lines. Several variance reduction techniques commonly used in Monte Carlo integration are proposed to reduce the variance of coverage estimates based on radial line sampling: importance sampling, control variates, and antithetic variates. The success of these techniques in irregularly shaped areas depends on the assumption that total line length is correlated with length of coverage. Radial line sampling as proposed here differs somewhat from ordinary line sampling because coverage estimates are based on squared line lengths.
Using Segmented Regression to Estimate Stages and Phases of Stand Development
Authors: VanderSchaaf Curtis L. , Burkhart Harold E.
Published: April 2024

Size-density trajectories on the logarithmic scale are generally thought to consist of two major stages. The first major stage is often referred to as the density-independent mortality stage in which the probability of mortality is independent of stand density; in the second stage, often referred to as the density-dependent mortality or self-thinning stage, the probability of mortality is related to stand density. Within the self-thinning stage, segments of a size-density trajectory consisting of a nonlinear approach to a linear portion, a linear portion, and a divergence from the linear portion are generally assumed. Here, we define the maximum size-density relationship (MSDR) dynamic thinning line as the linear portion. A loblolly pine (Pinus taeda L.) planting density study was used to demonstrate the process of using segmented regression models for estimating stages and phases of stand development. After results from the segmented regression model analyses were obtained, full versus reduced model tests indicated that a portion of self-thinning can be represented as linear. Estimates of the logarithm of quadratic mean diameter (lnD q) and logarithm of trees per hectare (lnN) where the linear component begins and ends were obtained from the segmented regression analyses and used as response variables predicted as a function of planting density. Predicted values of the lnD q and lnN allow for the MSDR dynamic thinning line boundary level and slope to be estimated for any planting density. Estimates showed that MSDR dynamic thinning line boundaries did not all attain the same level but varied by planting density.
Spatial Dynamics of Natural Regeneration in Two Differently Managed Pinus sylvestris Stands before and after Silvicultural Intervention Using Replicated Spatial Point Patterns
Authors: Pardos Marta , Montes Fernando , Cañellas Isabel
Published: April 2024

Individual seedlings were mapped on eight 5 m × 5 m plots between 2003 and 2006, in two differently managed Pinus sylvestris forests in Spain (group shelterwood system in Valsaín forest versus uniform system followed by soil preparation in Navafría forest). The spatial pattern of the seedlings was analyzed through the L(d) function. The spatial relationship between seedlings before and after the regeneration felling was analyzed using the intertype Lrs (d) function. To study the spatial relationship between seedling distribution and either light availability or organic matter depth, the Krx (d) function was used. A practical method is proposed for obtaining the group-specific mean for several replicates: L std(d), based on the standardization of the L(d) function by the quantile bounds of the null model, which, once attained, is compared with the sum, weighted by the number of points in each replicate. Both the Lstd(d) group means and the point number weighted mean showed a cluster pattern for seedlings from germination to 6 years old, peaking at short scales (15–100 cm), before and after the cutting. After the cutting, the co-occurrence between germinants and older seedlings was not significant, although the Lrs (d) function was positive and presented a peak (50–100 cm). Seedling emergence was positively associated with organic matter depth after the cutting. The association between seedling distribution and light was modified when the cutting was severe (>60% of tree basal area).
Spatial Pattern of Coast Redwood in Three Alluvial Flat Old-Growth Forests in Northern California
Authors: Dagley Christa M.
Published: April 2024

The spatial patterns of trees were investigated in old-growth redwood (Sequoia sempervirens [D. Don] Endl.) forests located in northern California to guide the design of restoration prescriptions. All stems ≥15 cm dbh were mapped and measured on three 1.5-ha plots. Patterns for trees in different size classes were analyzed separately with Ripley's K(d) function. Results revealed two patterns. At two sites, trees were randomly distributed throughout the stand and size classes were spatially independent of each other at scales of 0–50 m. At one site, a clumped spatial pattern was revealed for small- and medium-sized tree groups at small scales, whereas a random spatial pattern was detected for large trees at scales of 0–50 m. In addition, significant positive deviation from spatial independence at small scales suggested an attraction between tree groups. The spatial pattern of regeneration (trees <15 cm dbh) was described using quadrat-based analyses. Regeneration was clumped at all three sites. Results indicate that old-growth redwood forests occurring on alluvial flats have different spatial patterns for similar size classes of trees despite the similarities in topography and stand structural characteristics. For land managers interested in restoration, these results suggest that past thinning guides that emphasized uniform spacing may not be appropriate in restoration efforts. Instead, trees should be retained in clumps or in random spatial patterns.
Changes in Forest Structure After a Large, Mixed-Severity Wildfire in Ponderosa Pine Forests of the Black Hills, South Dakota, USA
Authors: Keyser Tara L. , Lentile Leigh B. , Smith Frederick W. , Shepperd Wayne D.
Published: April 2024

We evaluated changes in forest structure related to fire severity after a wildfire in ponderosa pine forests of the Black Hills, South Dakota, where 25% burned at low, 48% at moderate, and 27% at high severity. We compared tree mortality, fine (FWD) and coarse woody debris (CWD) and tree regeneration in areas burned under different severity. With low severity, mortality was limited to small trees (<15 cm dbh) with no reduction in basal area (BA) compared with unburned areas. FWD and CWD were 60% less than the unburned forest. With moderate severity, 100% mortality of small trees and significant large tree mortality resulted in an 50% reduction in BA and an open stand structure dominated by a few large trees. After 5 years, FWD and CWD recovered to unburned levels. With high severity, a lack of seed source makes regeneration unlikely. After 5 years, FWD equaled levels in unburned stands and CWD loads exceeded the unburned forest by 74%. The future landscape will be a mosaic of patches with forest structures determined by developmental trajectories set in motion by different fire severities. There will be patches of fully stocked, single canopy forest, multistory forest, and persistent grass- and shrub-dominated communities. High fuel loads in moderate and high severity areas remain a concern for management as does the lack of regeneration in high severity areas.
Problems of Scaling Plantation Plot Diameter Distributions to Stand Level
Authors: Borders Bruce E. , Wang Mingliang , Zhao Dehai
Published: April 2024

Diameter distribution models are used extensively in forest growth and yield modeling. They are usually fitted with fixed area sample plot data but applied at the stand level, the unit of forest production planning. In this process, the distribution obtained at the plot level is assumed to be representative of that at the stand level. In other words, the distribution from each plot of the same stand is assumed (roughly) to be the same, and therefore we can reasonably scale the plot distribution to the stand level. However, because of site-induced within-stand (between-plot) variability and spatial correlation introduced by tree competition and/or microsite effects or other factors, plot distributions may differ markedly from the stand distribution. We use data from 11 slash pine (Pinus elliottii) plantations, each consisting of 10 plots, to address differences in diameter distributions between plot level and stand level. The data indicate that (single) plot distributions are generally significantly different from their stand counterparts, because of spatial heterogeneity among plots within a given stand. For relatively homogeneous stands, diameter distributions obtained by averaging two to three plots may well represent the stand distribution within a certain precision, whereas for stands with more obvious spatial heterogeneity, a relatively large number of plots seem to be necessary for characterizing the stand distribution.
An Alternative View of Continuous Forest Inventories
Authors: Roesch Francis A.
Published: April 2024

A generalized three-dimensional concept of continuous forest inventories applicable to all common forest sample designs is presented and discussed. The concept recognizes the forest through time as a three-dimensional population, two dimensions in land area and the third in time. The sample is selected from a finite three-dimensional partitioning of the population. The partitioning is analogous to carving the volume into pieces like a three-dimensional jigsaw puzzle. Each puzzle piece is defined by the selection volumes of observation sets on the individual trees existing in the forest during the period of interest. The concept is a temporal extension of an alternative view of forest sampling offered in Roesch et al. (1993, Sur. Methods 19(2):199–204) and results in a finite number of independently selected three-dimensional sample units.
Sparse Bayesian Estimation of Forest Stand Characteristics from Airborne Laser Scanning
Authors: Junttila Virpi , Maltamo Matti , Kauranne Tuomo
Published: April 2024

In this article, a new method is applied to modeling forest stand characteristics from airborne laser scanning measurements. The method is an alternative to the cross-validation procedure of variable selection used in the ordinary least-squares (OLS) method and seemingly unrelated regression (SUR) with automatic selection of the features used in the model. This method is called the sparse Bayesian method. It does not suffer from overfitting thanks to the Bayesian formulation of the problem. The proposed method is applied to sample plot data obtained from inventory by compartments. The results show that the sparse Bayesian method performs as well as OLS and SUR methods, in terms of accuracy of total stand characteristics. The methods are comparable also in their demand for sample plot data. None of the methods lose much of their accuracy, even when just a few dozen sample plots are available. A Bayesian approach makes it possible to automate model formulation and sample plot selection processes. It is therefore possible to automatically generate a different model for intrastand strata, thus addressing intrastand variability. The proposed method automatically maintains a balance between the number of forest parameters and the rank of the model used to estimate them.
Evaluation of Four Methods to Estimate Parameters of an Annual Tree Survival and Diameter Growth Model
Authors: Cao Quang , Strub Mike
Published: April 2024

An approach to simultaneously estimate parameters of an annual tree growth model was developed, in which the sum of log-likelihood functions for tree survival and diameter growth was maximized. Four methods for acquiring interim values of stand density were evaluated: (1) Updating Attributes, in which individual tree values were summarized at the end of each year within the growth period to predict interim stand-level attributes, (2) Predicting Attributes, in which stand attributes were predicted annually using a stand-level model, (3) Linear Interpolation, in which stand attributes were predicted by linear interpolation, and finally (4) Initial Values, in which stand attributes at the beginning of the growth period were used as predictors throughout the growing period, and the rate of change for tree survival and diameter was assumed to be constant for this period. Data from the Southwide Seed Source Study of loblolly pine (Pinus taeda L.) showed that, overall, the Updating Attributes and Predicting Attributes produced better evaluation statistics in predicting tree survival and diameter growth than did the other two methods. A simulation study confirmed that these two methods produced the least biased estimates of parameters. Compared with the Updating Attributes method, the Predicting Attributes method produced similar evaluation statistics in predicting tree survival and diameter growth and similar bias in estimating model parameters. The Predicting Attributes method therefore offers a reasonable alternative to the Updating Attributes method, because of the ease of programming in available software languages.
Crown Recession Patterns in Three Conifer Species of the Northern Rocky Mountains
Authors: Garber Sean M. , Monserud Robert A. , Maguire Douglas A.
Published: April 2024

Crown length is a fundamental tree dimension for characterizing growth potential, wildlife habitat, and wood quality. The relative rates of height growth and crown recession determine the progression of crown length over time. We investigated patterns in crown recession of three co-occurring species in the northern Rocky Mountains: western white pine (Pinus monticola Dougl. ex D. Don), ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.), and interior Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. glauca). Past height, diameter, and crown base on 169 forest-grown trees were reconstructed by detailed stem analysis. Crown base was estimated for each year of the tree's life by dating the mortality of all whorl branches. Five-year crown recession was modeled in two parts, the first predicting the probability that a crown recedes and the second estimating recession conditional on its occurrence. The probability of crown recession increased and then decreased with an increasing crown ratio for all three species and similarly peaked over initial tree size. Conditional crown recession increased monotonically with crown ratio for ponderosa pine but peaked at crown ratios between 0.7 and 0.9 in western white pine and Douglas-fir. The resulting models lend insight into factors controlling rates of crown recession and their variation among species and differing initial conditions.
Identification of Scandinavian Commercial Species of Individual Trees from Airborne Laser Scanning Data Using Alpha Shape Metrics
Authors: Vauhkonen Jari , Tokola Timo , Packalén Petteri , Maltamo Matti
Published: April 2024

Airborne laser scanning (ALS) data are not usually considered to be very informative with respect to tree species, and this information is often obtained by combining such data with spectral image material. The aim here was to test the ability of variables derived solely from ALS data to describe the crown shape and structure characteristics required for tree species discrimination. For that purpose, we constructed tree crown approximations from the three-dimensional return data by applying a computational geometry approach, the alpha shape concept, and developed metrics for describing them. We examined the ability of these metrics to classify Scandinavian commercial species (pine, spruce, and deciduous trees) by means of linear discriminant analysis and compared the alpha shape metrics with groups of ALS-based height, density, intensity, and two-dimensional texture variables. For evaluating the classification accuracy, we used a test data set composed of 92 dominant or codominant trees detected and delineated manually from ALS data with a density of approximately 40 returns m−2. The alpha shape metrics proved capable of discriminating between all three species classes evaluated, and several height distribution and texture variables were found to discriminate between the coniferous tree species. An overall accuracy of approximately 95% and a κ coefficient of 0.90 was achieved using a combination of the variables. Because this initial application of the alpha shape metrics was carried out using a test data set on only such trees that are clearly detectable from remotely sensed data, further research is required to apply the approach presented here within stands with a continuous canopy. Furthermore, as the tree observations considered here were highly biased toward mature coniferous trees, experiments using more representative data sets are needed to generalize the result obtained.
Finding Efficient Harvest Schedules under Three Conflicting Objectives
Authors: Tóth Sándor F. , McDill Marc E.
Published: April 2024

Public forests have many conflicting uses. Designing forest management schemes that provide the public with an optimal bundle of benefits is therefore a major challenge. Although a capability to quantify and visualize the tradeoffs between the competing objectives can be very useful for decisionmakers, developing this capability presents unique difficulties if three or more conflicting objectives are present and the solution alternatives are discrete. This study extends four multiobjective programming methods to generate spatially explicit forest management alternatives that are efficient (nondominated) with respect to three or more competing objectives. The algorithms were applied to a hypothetical forest planning problem with three timber- and wildlife-related objectives. Whereas the ε-Constraining and the proposed Alpha-Delta methods found a larger number of efficient alternatives, the Modified Weighted Objective Function and the Tchebycheff methods provided better overall estimation of the timber and nontimber tradeoffs associated with the test problem. In addition, the former two methods allowed a greater degree of user control and are easier to generalize to n-objective problems.
A Balanced Repeated Replication Estimator of Sampling Variance for Apparent and Predicted Species Richness
Authors: Magnussen Steen
Published: April 2024

Design-based estimators of the sampling variance for apparent (S0 = observed) and predicted species richness (S̃) have been lacking. A balanced repeated replication (BRR) estimator is proposed and recommended for S0 and S̃. Good performance of the estimators is demonstrated in two contrasting examples with Monte Carlo (MC) simulations of simple random sampling with fixed area quadrats (plots) for estimating forest tree species richness. Chao and Lee's estimator of species richness was used for S̃. In BRR a set of half-samples forming an orthogonal design with respect to the inclusion/exclusion of sample records is used to produce estimates of S̃ from the observed half-sample and models for the effect of data-splitting. BRR estimates of the sampling variance of S0 were close to the MC estimates in the examples from eastern Canada (PROV) and the Barro Colorado Island (BCI) and clearly superior to naive model-based estimates. BRR estimates of S̃ were generally close to their MC counterparts, but in BCI a bias of approximately −10% was seen in small samples (n ≤ 24). BRR estimates of sampling variance of S̃ in PROV were close to the MC estimates for n ≤ 60. With larger sample sizes the BRR estimates drifted toward values obtained with Chao and Lee's model-based variance estimator. In BCI the opposite was true.
Short-Term Physiological Responses of Black Walnut (Juglans nigra L.) to Plantation Thinning
Authors: Gauthier Martin-Michel , Jacobs Douglass F.
Published: April 2024

We studied physiological responses of mature black walnut (Juglans nigra L.) trees to determine the time necessary for photosynthetic adaptation to plantation thinning. Measurements were taken before treatment (July 25, 2007) and for the first 3 days after thinning (July 29, 30, and 31, 2007). Measurements did not continue in August because trees had developed leaf anthracnose and senescence was occurring, but measurements resumed on May 29, 2008 and July 29, 2008. Repeated measures of net photosynthetic rates (A) showed that thinned trees did not respond immediately to partial release, but nearly doubled in A compared with a 35% increase in control trees 1 year after thinning. Significant increases in light, leaf water status, relative humidity of the air, and nitrogen content per unit leaf area were also found in thinned trees 1 year after treatment. From these variables, light (r2 = 0.79) showed the strongest relationship with A. Results suggest that black walnut requires a full growing season before it responds to treatment when thinned late in the growing season. Thinning earlier, such as in June, may trigger a more rapid adaptation in A of thinned trees that was not detected in our study.
Improved Calibration of Nonlinear Mixed-Effects Models Demonstrated on a Height Growth Function
Authors: Meng Shawn X. , Huang Shongming
Published: April 2024

The calibration of a nonlinear mixed-effects model is of critical importance in making local predictions. In previous applications, simplified equations were generally used to calibrate nonlinear mixed-effects models fitted using the first-order methods implemented through the NLINMIX macro in SAS. This simplification, however, could distort local predictions. In this study, using a nonlinear height growth model of lodgepole pine (Pinus contorta var. latifolia Engelm.), we demonstrated on two data sets the procedures to obtain an improved calibration of the height growth model. The differences between the improved and conventional calibrations were found to be significant. Calibration of the nonlinear mixed models using the improved method resulted in not only reduced bias but also reduced variance of the errors. It is recommended that the improved calibration method be used. A computing program detailing the procedures for obtaining the improved calibration was developed.
Automated Analysis of in Situ Canopy Images for the Estimation of Forest Canopy Cover
Authors: Korhonen Lauri , Heikkinen Jaakko
Published: April 2024

Forest canopy cover is a commonly used ecological indicator variable, but its reliable estimation in the field with, e.g., the line intersect sampling method is laborious. One alternative for obtaining this information quickly is to sample a larger area of canopy from each prespecified location within a sample plot by using digital cameras and then use image analysis techniques to extract canopy cover from the images. The first aim of this study was to implement an automated method for the estimation of canopy cover from skyward-looking canopy images obtained with standard digital cameras. The second aim was to compare the estimates obtained with the cameras and the automated analysis technique to control values measured with a vertical tube by using two different plot types and a varying angular field of view (1–50°). The results indicate that the automated analysis technique, involving an automated image thresholding algorithm and morphological image processing operations to eliminate the effect of within-crown gaps, can reliably replace manual postprocessing. With the tested sampling schemes, a 40° angle of view yielded the best approximation of the control.
Relationship between Soil Productivity and Tree Volume in Primeval Forest Ecosystems in Northeastern China
Authors: Yang John , Hu Yuanman , Bu Rencang
Published: April 2024

Soil properties are well known to influence plant productivity. Site-specific studies were conducted in primeval forest ecosystems in northeastern China to determine a quantitative relationship between soil productivity and tree volume. Three species-dominant primeval forest ecosystems (subalpine, spruce and fir, and Korean pine and hardwood) within the Changbai Mountain Natural Reserve area were selected as study sites. Soil properties of three landscape positions (convex, linear, and concave) in each of the three ecosystems were characterized, and the productivity was quantified using a soil-based productivity index (PI) model. On-site measurements of tree volume were used to assess their correlation with the soil PI values. A range of soil PI values occurred in landscape positions because of differential soil properties in each forest ecosystem. The PI values generally increased along the convex to concave transect and decreased with elevation. Soil pH and depth were identified as primary factors that limited the soil productivity, accounting for 52–56% of the PI variance. Tree volumes of each of the three ecosystems were positively correlated with soil PI values, with R2 of 0.82 to 0.87. The tree volume response to soil PI was dependent on the forest types. This field study demonstrated that the soil-based PI model would be a useful tool in identifying undesirable soil conditions of tree growth for site management and effectively predicting tree productivity based on soil properties within the site- and species-specific forest ecosystems.
Modeling Tree Mortality in Low- to Medium-Density Uneven-Aged Hardwood Stands Under a Selection System Using Generalized Estimating Equations
Authors: Kiernan Diane , Bevilacqua Eddie , Nyland Ralph , Zhang Lianjun
Published: April 2024

Tree mortality was modeled through time in uneven-aged northern hardwood stands managed under a selection system using long-term remeasurement data. Two models were fitted and compared: a traditional logistic regression model that predicted the probability of individual tree mortality over discrete time periods and a logistic regression model estimated using generalized estimating equations (GEEs) to account for autocorrelation in the longitudinal data. Model evaluation was based on the mean prediction error, mean absolute prediction error, variance of prediction errors, and mean square error calculated using an independent validation data set. The GEE model produced smaller evaluation statistics, especially for the smaller diameter classes. The predicted probability of mortality from the two models was compared with the observed mortality across 5-cm diameter classes for two time periods. Our results indicate that the GEE model was better able to capture the change in the probability of mortality over time, especially for the smaller diameter classes, than the more traditional logistic model.
Effects of Timber Harvest on Aquatic Macroinvertebrate Community Composition in a Northern Idaho Watershed
Authors: Gravelle John A. , Link Timothy E. , Broglio Justin R. , Braatne Jeff H.
Published: April 2024

Annual macroinvertebrate sampling was performed from 1994 to 2005 in the Mica Creek Experimental Watershed in northern Idaho to examine the relationship between contemporary timber harvest practices and the structure and diversity of aquatic macroinvertebrate assemblages. Four years of calibration, 4 years of postroad, and 4 years of postharvest (roads + harvest) data were used to analyze treatment effects. Metrics used to assess change included functional feeding group composition, organism densities, taxa richness indices, species diversity, and sediment tolerance indices. These assessments included changes to three macroinvertebrate taxa commonly used as bioindicators of stream habitat quality: Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddis flies) (EPT). In relation to pretreatment conditions, there were generally no major changes in functional feeding group composition or species diversity. Increases were observed in overall abundance and EPT abundance, but they largely can be explained by natural population variability. These results suggest that little or no change in macroinvertebrate communities resulted from road construction and timber harvest activities in the watershed. Substantial interannual variability was also observed, suggesting that infrequent biomonitoring may not provide adequate information to assess subtle disturbance effects in watersheds but can be an effective part of a comprehensive watershed monitoring program when coupled with other biotic and abiotic metrics.
Profit Efficiency in Timber Supply: Marginalization and Other Relevant Influences
Authors: Baardsen Sjur , Lien Gudbrand , Størdal Ståle
Published: April 2024

The objective of this article was to explore how marginalization of revenues from timber sales relative to income from agriculture and employment affects profit efficiency (the ratio of actual profit to maximum obtainable profit). We also sought to identify and measure the effects of other relevant inefficiency factors. A translog profit frontier function with an inefficiency module was estimated using a panel of 2,265 observations of 385 active Norwegian forest owners for 1991–2004. We found that profit efficiency decreases as the revenues from timber sales fall relative to agricultural or wage income. Other factors decreasing the efficiency were logging distance (beyond what can be explained by logging costs), fragmentation of the forest property, and time. Factors increasing profit efficiency were experience (age), information (possession of a management plan), and geographical location (centrality). On the basis of our results we make recommendations on how forest owners can improve their profit efficiency. We also suggest further developing and streamlining contract regimens as policy instruments for promoting efficiency.