John M. Lhotka

Economic and Life-Cycle Analysis of Forest Carbon Sequestration and Wood-Based Bioenergy Offsets in the Central Hardwood Forest Region of United States

This study investigates the combined impact of carbon and bioenergy markets on upland oak dominated mixed hardwood forests in the Central Hardwood Forest Region (CHFR) of the United States. A modification of the Hartman model was used for the economic analysis of carbon sequestration and using wood-based biomass for bioenergy. A life-cycle assessment was used to determine the amount of carbon sequestered due to stand growth and emitted during harvesting and decay of wood products. Two scenarios were taken, one where additionality of carbon is considered and the other where it is not. Sensitivity analysis was done with the range of carbon and bioenergy prices. The results show that net carbon payments have more impact on land expectation value (LEV) when additionality is not considered; in contrast, bioenergy payments have more impact on LEV when additionality is considered. Carbon and bioenergy prices also influenced the amount of stand level supply of forest products and carbon in both scenarios. In general, sawtimber, wood bioenergy, and carbon supply increased with an increase in carbon prices, whereas, pulpwood supply decreased. With few exceptions at higher carbon prices, bioenergy supply decreased with the increase in wood bioenergy prices, showing a backward bending supply curve in both scenarios.

Designing Nelder wheel plots for tree density experiments

The Nelder (Biometrics 18:283–307, 1962) wheel design allows a researcher to test multiple tree densities in a single plot. Because spatial relationships among planted trees are fundamental to a Nelder wheel, a researcher needs a specific set of layout parameters to establish a Nelder plot. While Nelder (Biometrics 18:283–307, 1962) provides calculus-based equations for determining the required layout parameters, the presentation focuses on derivation of these equations and not their application to forestry research. Other authors have outlined the design of Nelder plots for forestry research, but have done so using trigonometry-based equations. Existence of two layout methodologies in the literature is a source of confusion. In this paper, we present a straightforward means to determine the design parameters critical to the establishment of Nelder plots used within tree density research. The layout equations presented are expressed in terms that allow applied forestry researchers to easily answer the following question. Given the number and range of tree densities I want to evaluate, what are the required Nelder wheel layout parameters? Finally, we provide a step-by-step example of the design and installation of a Nelder plot for a scenario familiar to tree density research and discuss analysis of Nelder wheel experiments.

Comparing individual-tree approaches for predicting height growth of underplanted seedlings

Key messageIndividual-tree seeding height growth models developed using tree inventory data were comparable to those requiring the unique observation of point-based canopy structure data at each seedling.ContextQuantitative approaches describing the relationship between canopy structure and seedling growth can inform silvicultural decision making regarding the development of tree reproduction beneath a dominant forest canopy.AimsIndividual-tree seedling growth models with canopy structure predictors derived from tree inventory data have not been well-explored. This study compared a model framework fit using point-based measures of canopy structure observed at the seedling level to one fit using area-wide canopy structure variables derived from standard inventory plot data.MethodsSpecies-specific models predicting 5-year height growth were fit for cherrybark oak (Quercus pagoda Raf.), water oak (Quercus nigra L.), and yellow-poplar (Liriodendron tulipifera L.) underplanted within a canopy structure gradient created by silvicultural manipulation of a closed-canopy forest in Georgia, USA.ResultsThough the species varied in shade tolerance and growth rates, the general relationship between the predictor variables and height growth was similar among species and model type. Models highlight the importance of including predictor variables that describe seedling size along with openness and vertical structure of the forest canopy.ConclusionWhile the two model frameworks had comparable fit statistics, the one with predictors derived from tree inventory data may have enhanced utility as it can be directly integrated into existing individual-tree forest growth simulators.

Effects of gap-based silviculture on thermal biology of a terrestrial reptile

Abstract Context. Terrestrial reptiles require varied thermal environments to promote optimal physiological performance, growth, reproduction, and survival. Aims. Our study was designed to determine whether gap-based silvicultural practices offer suitable thermal environments for eastern box turtles (Terrapene carolina) by examining environmental temperature variation and body temperature of eastern box turtles in, and adjacent to, canopy gaps. Methods. We recorded box turtle body temperature from 20 radio-tracked turtles and environmental temperatures (canopy gaps and undisturbed habitat) using temperature loggers from June to September 2014 in a managed forest after canopy gaps (0.28–1.13 ha gap–1) were created via gap-based silviculture. Key results. Over the four-month study period, gap temperatures were generally higher than adjacent undisturbed microhabitats. Box turtle body temperatures were closely correlated with environmental temperatures in undisturbed habitat in June and July. Turtle body temperatures were, however, closely correlated with environmental temperatures in canopy gaps in August and September. In addition, box turtles in our study had activity areas that overlapped canopy gaps from 0 to 65%, depending on the individual. As percentage overlap of canopy gaps increased, turtle body temperatures were increasingly correlated with canopy gap temperatures. Furthermore, as percentage overlap of canopy gaps increased, daily mean body temperature records consistently stayed within the preferred box turtle body temperature range (20.2–26.2°C). Conclusions. Our study suggests that gap-based silviculture can create thermally compatible environments for box turtles depending on the time of day and year, and that box turtles use these microhabitats to thermoregulate. Implications. The application of relatively small-scale silvicultural practices (≤1 ha gap–1) that provide heterogeneity in forest structure, composition, and function may be a useful alternative to clearcutting and other intensive harvesting methods that are associated with declines in terrestrial reptile populations.

A Dendroecological Investigation of an Upland Oak-Dominated Forest within the Grand Prairie Region of Illinois

ABSTRACT We studied an upland forest located within the Grand Prairie region of Illinois and utilized tree-ring analysis to document tree cohort development and radial growth in relation to stand disturbance and climate. The overstory within the Humiston Woods Nature Center (Livingston County, Illinois) study area was dominated by oak (Quercus spp.), hickory (Carya spp.), and ash (Fraxinus spp.), while the subordinate crown classes were principally composed of elm (Ulmus spp.) and sugar maple (Acer saccharum). The study area contained tree cohorts originating during two recruitment periods. Overstory oaks and hickories primarily established between 1865 and 1900. A second tree cohort was associated with a timber harvest occurring in the late 1960s. In contrast to the 1865–1900 recruitment period, trees within the 1965–1980 cohort were primarily ash, elm, sugar maple, and black cherry (Prunus serotina). RWI values were most strongly correlated with Palmer Drought Severity Index, precipitation, and temperature in June of the current growth year. RWI and radial increment data for overstory oaks highlighted a sustained growth increase following a late 1960s timber harvest that remained high relative to predisturbance growth rates even in pronounced drought years. Data provide needed insight into oak woodland recruitment patterns relating to disturbance regimes that are difficult to recreate at the landscape level but often serve as ecological restoration objectives. Our findings help extend the foundational knowledge regarding forest composition, stand level dynamics, and radial growth relationships present among upland forests and changing disturbance patterns in the Grand Prairie region of Illinois.