Mahadev Sharma

Height-diameter models using stand characteristics for Pinus banksiana and Picea mariana

Height–diameter relationships based on stand characteristics (stand density, basal area and site index) were investigated for jack pine and black spruce trees using the data from permanent growth study plots in northern Ontario, Canada. Approximately half of the data was used to estimate model parameters and the rest was used for model evaluation. Multiple Chapman–Richards growth functions with parameters expressed in terms of various stand characteristics were fitted to determine the best models for predicting height. Models providing the most accurate predictors of height included basal area, trees ha−1 and diameter at breast height. The inclusion of site index did not increase predictive accuracy.

Top height definition and its effect on site index determination in thinned and unthinned loblolly pine plantations

Abstract Seven definitions of stand (top) height: (1) mean height of dominant and codominant trees at the time of plot measurement, (2) mean height of dominant and codominant trees that have always been dominant or codominant over the life of the stand, (3) Lorey mean height, (4) average height of the 100 thickest trees per hectare at the time of measurement, (5) average height of the 100 thickest trees per hectare at the time of last measurement, (6) average height of the 20% thickest trees at the time of plot measurement, and (7) average height of the 20% thickest trees at each measurement that also survived to the last measurement were evaluated for use in site index (SI) determination. Data collected from permanent plots over a 15-year period in thinned and unthinned loblolly pine plantations were used to make comparisons. Except for a few cases at certain measurements, all seven definitions of top height were significantly different from each other. Site index was predicted based on these definitions to determine if one definition is superior. Magnitudes of the maximum range of residuals and the fit statistics indicated that SI estimated using mean height of dominant and codominant trees that have always been dominant or codominant over the life of the stand is more precise than site indices estimated using other definitions. Using this definition of top height, a new SI equation for these stands was developed.

Forest stand dynamics and similarity theory

Abstract Data for modeling forest stand development require repeated, costly measurements over extended periods of time. The purpose of this study was to develop methods for generalizing short-term observations in juvenile stands to long-term trends in more mature stands. The concepts applied involve scale modeling techniques whereby small physical models (model system) provide insight into the nature of important phenomena (prototype system). Loblolly pine plantations in an operational spacing and in a scale that consisted of reducing the distance between plants to 1/16th that of the operational spacing were regarded as prototype and model systems, respectively. Stand development in these two forest systems was examined using principles from similarity theory. In order to apply similarity theory, the temporal development of two commonly measured variables, height and diameter, were standardized on a common scale using data from prototype and model systems. Then, nondimensional height and diameter ratios in the two systems were created using appropriate reference variables from each system. Analysis showed that the height and diameter growth relationships developed similarly for the two systems making growth results from the model system scalable to the prototype system. Scaling functions for forest systems established at small spatial scales could be useful tools for a host of research and developmental purposes.

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.

Life cycle cost and economic assessment of biochar-based bioenergy production and biochar land application in Northwestern Ontario, Canada

BackgroundReplacement of fossil fuel based energy with biochar-based bioenergy production can help reduce greenhouse gas emissions while mitigating the adverse impacts of climate change and global warming. However, the production of biochar-based bioenergy depends on a sustainable supply of biomass. Although, Northwestern Ontario has a rich and sustainable supply of woody biomass, a comprehensive life cycle cost and economic assessment of biochar-based bioenergy production technology has not been done so far in the region.MethodsIn this paper, we conducted a thorough life cycle cost assessment (LCCA) of biochar-based bioenergy production and its land application under four different scenarios: 1) biochar production with low feedstock availability; 2) biochar production with high feedstock availability; 3) biochar production with low feedstock availability and its land application; and 4) biochar production with high feedstock availability and its land application- using SimaPro®, EIOLCA® software and spreadsheet modeling. Based on the LCCA results, we further conducted an economic assessment for the break-even and viability of this technology over the project period.ResultsIt was found that the economic viability of biochar-based bioenergy production system within the life cycle analysis system boundary based on study assumptions is directly dependent on costs of pyrolysis, feedstock processing (drying, grinding and pelletization) and collection on site and the value of total carbon offset provided by the system. Sensitivity analysis of transportation distance and different values of C offset showed that the system is profitable in case of high biomass availability within 200 km and when the cost of carbon sequestration exceeds CAD

Biochar-based bioenergy and its environmental impact in northwestern Ontario Canada: a review.

60 per tonne of equivalent carbon (CO2e).ConclusionsBiochar-based bioenergy system is economically viable when life cycle costs and environmental assumptions are accounted for. This study provides a medium scale slow-pyrolysis plant scenario and we recommend similar experiments with large-scale plants in order to implement the technology at industrial scale.

Applying wavelet-based functional approach in modelling tree taper

Biochar is normally produced as a by-product of bioenergy. However, if biochar is produced as a co-product with bioenergy from sustainably managed forests and used for soil amendment, it could provide a carbon neutral or even carbon negative solution for current environmental degradation problems. In this paper, we present a comprehensive review of biochar production as a co-product of bioenergy and its implications. We focus on biochar production with reference to biomass availability and sustainability and on biochar utilization for its soil amendment and greenhouse gas emissions reduction properties. Past studies confirm that northwestern Ontario has a sustainable and sufficient supply of biomass feedstock that can be used to produce bioenergy, with biochar as a co-product that can replace fossil fuel consumption, increase soil productivity and sequester carbon in the long run. For the next step, we recommend that comprehensive life cycle assessment of biochar-based bioenergy production, from raw material collection to biochar application, with an extensive economic assessment is necessary for making this technology commercially viable in northwestern Ontario.

Height–diameter equations for boreal tree species in Ontario using a mixed-effects modeling approach

Abstract• IntroductionThe wavelet-based functional approach was evaluated for modelling tree taper of jack pine (Pinus banksiana Lamb.) trees grown in the Canadian boreal forest region.• ObjectivesWavelet-based functional fixed and mixed-effects models were developed to predict tree taper, and these models were evaluated for their predictive accuracy using calibration and evaluation data sets.• Results and discussionDiameters predicted using both fixed and mixed-effects taper models were unbiased for calibration data set as the 95% credible limits included 0 at all locations along the boles. The diameters predicted by these models for validation data set, however, were unbiased only at four out of 11 locations as the 95% credible limits of mean bias using fixed effects model did not include 0 at other locations.• ConclusionThe study concludes that the wavelet-based taper models are able to describe the taper of the trees used in fitting the model but are unable to capture the mean taper function of the trees not used in fitting the model.