Michael T. Ter-Mikaelian

Biomass equations for sixty-five North American tree species

Abstract The paper presents a comprehensive review of the biomass equations for 65 North American tree species. All equations are of the form M = aDb, where M is the oven-dry weight of the biomass component of a tree (kg), D is diameter at breast height (DBH) (cm), and a and b are parameters. Equations for the following tree components were included in the review: total aboveground biomass, stem wood, stem bark, total stem (wood and bark), foliage, and branches (wood and bark). A total of 803 equations are presented with the range of DBH values of the sample, sample size, coefficient of determination R2, standard error of the estimate, fitting method used to estimate the parameters a and b, correction factor for a bias introduced by logarithmic transformation of the data, site index and geographic location of the sampled stand(s), and a reference to the paper in which the equation (or the data) was published. The review is a unique source of equations that can be used to estimate tree biomass and/or to study the variation of biomass components for a tree species.

A review of the long-term effects of post-harvest silviculture on vertebrate wildlife, and predictive models, with an emphasis on boreal forests in Ontario, Canada

Greater fibre yields may be possible in commercial forests through an increased application of post-harvest silvicultural techniques. In Canadian boreal forests, while basic silvicultural regeneration techniques such as planting, seeding, scarifying, and tending, have been employed since the 1940’s, more intensive techniques (intensive forest management (IFM)) such as increased area planted, pre-commercial and commercial thinning, extra tending events, fertilizing, and short rotations may soon be used. There may be effects of basic and more intensive silviculture on biodiversity in the long-term, compared to natural regeneration following logging or especially stand development following natural disturbances. We reviewed approximately 50 papers that reported studies of the long-term effects of post-harvest silviculture on vertebrate wildlife. In particular, large impacts to biodiversity universally occur when native forest types are replaced by rapidly-growing exotic tree species. However, in boreal forests, native tree species are usually planted, and so any effects on associated wildlife communities may be considerably less than in non-native species plantations. Limited long-term information is available, but published studies of effects of basic silviculture and IFM suggested that loss of structures in forest stands was an important common impact that resulted in vertebrate species responses. Fewer structural features in managed forests compared to in natural forests likely results in reduced numbers of animal species dependent on those structures, such as cavity-using species and species for which large decaying woody debris is important. Simplifying stand structures and species composition may result in systems with low connectivity, making them vulnerable to insect and mammalian herbivory. Concentration of IFM in stands on highly productive sites could exacerbate effects (positive or negative), owing to the positive relationship between forest productivity and animal and plant diversity. Species such as black-backed woodpeckers (Picoides arcticus) may be reduced over large areas by stand conversion to mixedwoods, stand structural changes and especially age-class truncation. On the other hand, IFM may contribute increased habitats to species favoring young to mature coniferous-dominated forests, that normally decline across a landscape following clearcutting in boreal mixed and upland conifer stands. An aspatial model, based on published and local information and expert opinion, suggested that IFM and post-harvest silviculture in Ontario’s boreal forests would produce positive and negative species-specific effects on the vertebrates that we modeled. However, IFM appeared to result in little increased effect over basic post-harvest silviculture. We also expect that stand-level effects of IFM on species would accumulate through time over landscapes, as more stands come under intensive management and the level of effects will be cumulative.

Temporal fire disturbance patterns on a forest landscape

Abstract Potential temporal fire disturbance patterns on a forest landscape were investigated using a fire regime model with four different fire probability functions: (1) forest age-independent; (2) hyperbolic increase with forest age; (3) sigmoid increase with age; and (4) linear increase with age. Different combinations of parameter values for a logistic equation were used to approximate different fire probability functions. An extensive model behavior study suggested that fire regimes similar to the observations in Ontario could result from any of the fire probability functions, but with different parameter values. Simulation results on the case study area indicated that when the fire rotation period was fixed to 200 years (corresponding to fire regimes in the southern part of northwestern Ontario), the predicted temporal disturbance patterns (average interval between two successive fires) were similar for small and intermediate fires, but different for large and severe fires. The results from the fire probability function with a sigmoid shape appeard the most appropriate among the four tested fire probability functions. The average interval between two successive fires for each size group is: small fires every 5.8 years, intermediate fires every 34.4 years, and large fires every 151.6 years. Better prediction of a temporal disturbance pattern, especially for large and severe fires, will require an explicit understanding of the quantitative relationship between fire probability and forest age.

Modelling the effect of spatial scale and correlated fire disturbances on forest age distribution

Abstract With the exponential model, Van Wagner (1978) gave us valuable insight in understanding stand age and forest age distribution in fire-disturbed landscapes. He showed that, under certain conditions, the probability distribution of the age of a stand subject to periodic renewal by fire is exponential. The extension of this model to the landscape-level results, also under certain conditions, in an exponential shape for the forest age distribution. Empirical studies have supported this hypothesis in some landscapes and not in others. The results are believed to depend on the size of the landscape in question, the patterns of fire disturbance, and changes in the disturbance regime over time and space. In this paper, we present additional insight into some of the fundamental factors that determine the forest age distribution. We analyzed some alternative spatial models of fire disturbance, and used a spatial simulation model (FLAP-X) to explore whether the forest age distribution has an exponential shape, and whether it would be stable or variable over time under different conditions. We use different spatial and temporal disturbance patterns, some of which represent correlation due to fire growth and episodes of high fire disturbance. We describe FLAP-X and give the results of computational tests based on hypothetical data. We found that, under characteristic boreal fire disturbance regimes, we should not expect to find forest age distribution stability even at very large spatial scales due to the spatial and temporal correlation of disturbances.

Estimating biomass of white spruce seedlings with vertical photo imagery

Estimation of individual tree seedling biomass isrequired in a variety of forest management andresearch applications such as assessment of netprimary productivity and carbon sequestrationpotential of forest stands, understory forest fuelinventories, and development of silviculturalguidelines to promote the growth of desired treespecies. Photo imagery is a promising non-destructivemethod for estimating the aboveground biomass of treeseedlings. This method was tested using naturallyregenerated white spruce (Picea glauca (Moench)Voss) seedlings growing in the understory of a mixedconifer shelterwood in central Ontario. In the fall of1997, 45 seedlings were sampled from plots exposed toone of three mechanical release treatments (earlyspring release, mid summer release, and no release(control)) in 1994. Each seedling was photographed inthe field to measure the vertical projected area(silhouette area) of the aboveground portion of theseedling. Seedlings were harvested, basal diameter andtotal height measured, and biomass (dry mass) offoliage, branches, main stem and total abovegroundplant tissue determined. Regression analysis revealeda strong relationship between both silhouette area andbasal diameter, and seedling biomass. Coefficients ofdetermination for regression equations usingsilhouette area were equal to 0.892, 0.918, 0.926, and0.937 for the main stem, branches, foliage, and totalaboveground biomass, respectively. Respectivecoefficients of determination for regression equationsusing basal diameter were 0.960, 0.945, 0.953, and0.977. Silhouette area-based equations for totalaboveground and foliar biomass differed significantly(P < 0.005) among release treatments. Nosignificant differences among treatments were observedbetween silhouette area-based equations for biomass ofbranches and main stem (P > 0.05), or betweenbasal diameter-biomass (allometric) equations for allcomponents (P > 0.1). The method was thentested by validating the biomass equations using anindependent data set from 35 white spruce seedlingsfrom the same site and cohort, but exposed todifferent treatments and microenvironmentalconditions. For each seedling, biomass components werepredicted using silhouette area-based and allometricequations, and a relative error of predictioncalculated. The mean relative error for silhouettearea-based predictions varied among biomass componentsfrom −20.25% to −3.21%, with standard deviation ofthe error ranging from 23.04% to 33.44%. The meanrelative error for allometric equations ranged from−2.46% to −21.75%, with standard deviations of23.34% to 32.61%. These results suggest that: (1)photo imagery can be used as an alternative to moretraditional allometric methods of biomass estimation,and (2) general (developed for a broad range ofgrowing conditions) equations derived by either methodare preferable to those specifically calibrated for agiven growing environment.

Carbon debt repayment or carbon sequestration parity? Lessons from a forest bioenergy case study in Ontario, Canada.

Forest bioenergy can contribute to climate change mitigation by reducing greenhouse gas (GHG) emissions associated with energy production. We assessed changes in GHG emissions resulting from displacement of coal with wood pellets for the Atikokan Generating Station located in Northwestern Ontario, Canada. Two contrasting biomass sources were considered for continuous wood pellet production: harvest residue from current harvest operations (residue scenario) and fibre from expanded harvest of standing live trees (stemwood scenario). For the stemwood scenario, two metrics were used to assess the effects of displacing coal with forest biomass on GHG emissions: (i) time to carbon sequestration parity, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in regenerating forest equalled the amount of forest carbon without harvest for energy production; and (ii) time to carbon debt repayment, defined as the time from the beginning of harvest to when the combined GHG benefit of displacing coal with biomass and the amount of carbon in the regenerating forest equalled forest carbon at the time of harvest. Only time to carbon sequestration parity was used for the residue scenario. In the residue scenario, carbon sequestration parity was achieved within 1 year. In the stemwood scenario, times to carbon sequestration parity and carbon debt repayment were 91 and 112 years, respectively. Sensitivity analysis showed that estimates were robust when parameter values were varied. Modelling experiments showed that increasing growth rates for regenerating stands in the stemwood scenario could substantially reduce time to carbon sequestration parity. We discuss the use of the two metrics (time to carbon sequestration parity and time to carbon debt repayment) for assessing the effects of forest bioenergy projects on GHG emissions and make recommendations on terminology and methodologies for forest bioenergy studies.

An individual tree-based model of competition for light

Abstract A variant of a distance-independent neighborhood model for light competition is developed, in which the average amount of light available to an individual tree in a population is found by considering the discrete representations of tree crowns. Trees are assumed to be independently and uniformly distributed within a certain area of interaction (a plot). Tree crowns are considered as either vertical or horizontal planar screens (“discrete screens”) of arbitrary form that partially absorb light and that are illuminated by a point source of light. The average vertical light profile is calculated for both crown representations. The results obtained are discussed and are compared with the description traditionally used in forest modeling; the latter considers a tree canopy as a “solid layer” for which the light profile is calculated using Lambert-Beers law of light absorption. The comparison showed that the solid-layer approach underestimates the amount of light available to an individual tree and is less sensitive to changes in the number of trees in the plot than the “discrete screens” approach. The paper also discusses an application of the results obtained to population-level dynamical models.

Carbon Profile of the Managed Forest Sector in Canada in the 20th Century: Sink or Source?

Canada contains 10% of global forests and has been one of the worlds largest harvested wood products (HWP) producers. Therefore, Canadas managed forest sector, the managed forest area and HWP, has the potential to significantly increase or reduce atmospheric greenhouse gases. Using the most comprehensive carbon balance analysis to date, this study shows Canadas managed forest area and resulting HWP were a sink of 7510 and 849 teragrams carbon (TgC), respectively, in the period 1901-2010, exceeding Canadas fossil fuel-based emissions over this period (7333 TgC). If Canadian HWP were not produced and used for residential construction, and instead more energy intensive materials were used, there would have been an additional 790 TgC fossil fuel-based emissions. Because the forest carbon increases in the 20th century were mainly due to younger growing forests that resulted from disturbances in the 19th century, and future increases in forest carbon stocks appear uncertain, in coming decades most of the mitigation contribution from Canadian forests will likely accrue from wood substitution that reduces fossil fuel-based emissions and stores carbon, so long as those forests are managed sustainably.

Effects of harvesting on spatial and temporal diversity of carbon stocks in a boreal forest landscape

Carbon stocks in managed forests of Ontario, Canada, and in harvested wood products originated from these forests were estimated for 2010–2100. Simulations included four future forest harvesting scenarios based on historical harvesting levels (low, average, high, and maximum available) and a no-harvest scenario. In four harvesting scenarios, forest carbon stocks in Ontarios managed forest were estimated to range from 6202 to 6227 Mt C (millions of tons of carbon) in 2010, and from 6121 to 6428 Mt C by 2100. Inclusion of carbon stored in harvested wood products in use and in landfills changed the projected range in 2100 to 6710–6742 Mt C. For the no-harvest scenario, forest carbon stocks were projected to change from 6246 Mt C in 2010 to 6680 Mt C in 2100. Spatial variation in projected forest carbon stocks was strongly related to changes in forest age (r = 0.603), but had weak correlation with harvesting rates. For all managed forests in Ontario combined, projected carbon stocks in combined forest and harvested wood products converged to within 2% difference by 2100. The results suggest that harvesting in the boreal forest, if applied within limits of sustainable forest management, will eventually have a relatively small effect on long-term combined forest and wood products carbon stocks. However, there was a large time lag to approach carbon equality, with more than 90 years with a net reduction in stored carbon in harvested forests plus wood products compared to nonharvested boreal forest which also has low rates of natural disturbance. The eventual near equivalency of carbon stocks in nonharvested forest and forest that is harvested and protected from natural disturbance reflects both the accumulation of carbon in harvested wood products and the relatively young age at which boreal forest stands undergo natural succession in the absence of disturbance.