Browsing by Author "Green, Patrick Corey"

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    Competitive status of red spruce (Picea rubens) and Fraser fir (Abies fraseri) at ecotonal transitions in southern Appalachian sky islands
    Wetzel, Rose (Virginia Tech, 2024-07-05)
    Southern Appalachian spruce-fir sky islands are globally threatened, boreal relict forests where red spruce (Picea rubens) and Fraser fir (Abies fraseri) are dominant. Fraser fir dominates at the highest elevations with spruce-fir and spruce-dominated stands at middle elevations and hardwoods associating at lower elevations. A primary concern is encroachment of hardwoods upslope as climate change-driven milder temperatures and high precipitation confine spruce-fir forests to even higher elevations. We performed a dendrochronological analysis of growth rates in red spruce, Fraser fir, and competing hardwoods between cover types and slope aspects at six sky islands. We created linear models to test effects of aspect, cover type, and year on basal area growth measurements of red spruce, Fraser fir, and hardwoods to assess effects of competition. Growth rates were significantly affected by species, aspect, cover type, and year, and generally increased over time. Red spruce growth rates varied by combination of aspect and cover type but were greater than those of hardwoods on northern and southern aspects. Fraser fir growth rates were negative on southern-facing fir-dominated stands but increased in all other stands with the highest growth rates found in fir-dominated stands. The differences we report by cover type and aspect could help conservation practitioners prioritize treatment locations to improve climate resiliency.
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    Decision Support for Operational Plantation Forest Inventories through Auxiliary Information and Simulation
    Green, Patrick Corey (Virginia Tech, 2019-10-25)
    Informed forest management requires accurate, up-to-date information. Ground-based forest inventory is commonly conducted to generate estimates of forest characteristics with a predetermined level of statistical confidence. As the importance of monitoring forest resources has increased, budgetary and logistical constraints often limit the resources needed for precise estimates. In this research, the incorporation of ancillary information in planted loblolly pine (Pinus taeda L.) forest inventory was investigated. Additionally, a simulation study using synthetic populations provided the basis for investigating the effects of plot and stand-level inventory aggregations on predictions and projections of future forest conditions. Forest regeneration surveys are important for assessing conditions immediately after plantation establishment. An unmanned aircraft system was evaluated for its ability to capture imagery that could be used to automate seedling counting using two computer vision approaches. The imagery was found to be unreliable for consistent detection in the conditions evaluated. Following establishment, conditions are assessed throughout the lifespan of forest plantations. Using small area estimation (SAE) methods, the incorporation of light detection and ranging (lidar) and thinning status improved the precision of inventory estimates compared with ground data alone. Further investigation found that reduced density lidar point clouds and lower resolution elevation models could be used to generate estimates with similar increases in precision. Individual tree detection estimates of stand density were found to provide minimal improvements in estimation precision when incorporated into the SAE models. Plot and stand level inventory aggregations were found to provide similar estimates of future conditions in simulated stands without high levels of spatial heterogeneity. Significant differences were noted when spatial heterogeneity was high. Model form was found to have a more significant effect on the observed differences than plot size or thinning status. The results of this research are of interest to forest managers who regularly conduct forest inventories and generate estimates of future stand conditions. The incorporation of auxiliary data in mid-rotation stands using SAE techniques improved estimate precision in most cases. Further, guidance on strategies for using this information for predicting future conditions is provided.
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    The Effects of Mechanical Site Preparation Treatment and Species Selection on Survival and Carbon Pools in 12-Year-Old American Sycamore (Platanus occidentalis) and Willow Oak (Quercus phellos) Riparian Plantations in the Southeastern U.S. Piedmont
    Lynn, Drake Havelock (Virginia Tech, 2024-07-16)
    Riparian wetlands may provide numerous ecosystem services, including water quality protection, food and fiber supply, wildlife habitat, and carbon sequestration. In recent years, riparian forests have received increased attention and funding for riparian forest restoration projects. Unfortunately, failures of riparian restoration efforts are likely due to mortality of planted trees. Tree mortality is commonly attributable to several factors, including selection of species that are not well suited to the wetland sites, inadequate planting densities, soil compaction associated with former agricultural activities, lack of microtopographic relief that allow small seedling to survive on wet sites, competition by herbaceous plants, and browse. Selection of well-suited species, dense planting and use of mechanical soil site preparations are all potential remedies to partially address success of wetland restoration plantings. Riparian restoration projects have historically been undertaken with goals of improving water quality and/or wildlife habitat, but in recent years there has been increased valuation of carbon sequestration. Carbon valuation appears to be increasing, but more research is needed to determine rates and pools of carbon accumulation in riparian areas. Our research quantifies forest establishment effects on multiple carbon pools in a densely planted, 12-year-old old-field riparian restoration. Our research evaluated the effects of four soil mechanical site preparations (bed, disk, pit, and mound and rip) and species selection (American sycamore (Platanus occidentalis) and willow oak, (Quercus phellos) on forest establishment and carbon storage across multiple pools, namely in planted trees, herbaceous vegetation, fine roots, organic soil horizons, and the mineral soil. At 12 years, we found that species selection was more important to carbon storage than site preparation. American sycamore was well suited to the site and had better survival than willow oak (64% vs 42% survival). American sycamore also stored more carbon across all site preparations than willow oak. Measured carbon storage averaged 74.8 Mg ha-1 for American sycamore treatments and 63.1 Mg ha-1 for willow oak treatments. The plots were densely planted (1.2 m (4ft) by 1.8 m (6ft) spacing), and forests were established even in higher mortality willow oak plots. These results indicate that high planting density is potentially a viable practice for establishing riparian forest cover, especially if desired species are marginally site suited or other survival inhibiting factors exist.
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    Live crown ratio model and lumber recovery for intensively managed loblolly pine
    Parajuli, Kamana (Virginia Tech, 2025-01-09)
    Loblolly pine is a commonly planted pine species in the Southern US which is intensively managed as well as a major contributor to the timber industry. Various silvicultural treatments are commonly applied to pine plantations including thinning and sometimes pruning. Tree crowns contain the active photosynthesis region and play a vital role in tree growth. Among various tree crown measurements, live crown ratio (LCR) is derived from height to live crown base (HLCB) and total tree height. Accurate measurement of HLCB is basis for live crown ratio prediction. Due to numerous definitions and practical considerations, HLCB and crown structure are difficult and slow to measure accurately. Despite this, LCR is a useful predictor in various growth and yield models. Due to the challenges in measuring tree crowns, accurate live crown ratio prediction models are useful. The LCR model of (Dyer and Burkhart, 1987) was refit with intensively managed plantation (IMP) data. The parameters were significant, and the residual plots showed no concerning patterns but the prediction of height to live crown base for pruned trees was not logical as it sometimes predicted HLCB lower than pruning height. To address this, the base model was modified to accommodate the pruning effect and provide logical predictions. LCR is in range of 0 - 1 and HLCB is greater or equal to pruning height. If trees are not pruned, it reverts to the original model. The models were validated with a dataset of IMP measurements not used in fitting. Validation statistics suggest the model performs nearly as well as the original, unconstrained base model. It is expected that the new model will be useful for forest managers to predict LCR of both pruned and unpruned trees. The second part of the study is to understand the importance of common tree variables in predicting the lumber recovery in planted loblolly pine. A random forest model was used to determine the variable importance of DBH, total tree height and live crown ratio for total board ft., high-grade, and high-grade lumber proportion compared to total board ft. DBH ranked at the first position followed by total tree height and live crown ratio similarly ranked for volume and high-grade lumber volume. For proportions of high-grade lumber, tree height was at top rank followed by LCR, and DBH. However, the effect of these variables for lumber recovery was not explored. It is suggested that future work can explore parametric model forms for accurately predicting lumber recovery using simple, easy to measure tree variables.
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    Modeling Stem Taper of Southern Appalachian Red Spruce
    Morrone, Steven (Virginia Tech, 2023-05-24)
    Red spruce (Picea rubens Sarg.) is a commercially and ecologically important conifer species that primarily exists at northern latitudes of eastern North America. During the last glaciation, its range extended down the Appalachian Mountain chain into North Carolina and Tennessee. Since the planet warmed over the subsequent millennia, only small, sky-island populations remain at the highest peaks of the southern Appalachians where their habitat continues to be threatened by a warming climate. While they have been recognized for the rare wildlife habitat they provide in the region, these populations remain understudied. This thesis aimed to provide additional quantitative methods for managing red spruce stands through regionally fitted stem taper equations and to examine differences in stem form between the northern and southern populations of red spruce. In Chapter 1, five stem taper equations were evaluated for their ability to predict upper stem diameters and total volume in southern Appalachian red spruce: a simple linear, a quadratic polynomial, a segmented, a variable exponent, and a geometric model. Based on past studies and our results, we found that the best equations to use were the variable exponent and segmented polynomial models. Users should consider their own objectives and practical limitations in choosing which equation to use. In Chapter 2, we examined differences in stem form using three methods: a sectional rate of change in diameter, a sectional form class ratio, and a region variable added to two taper equations. The results were mixed, with the rates of change showing significant differences (p<0.05), but the form class ratios showing a mix of significant and insignificant differences. The two equations also had contrasting significance results. This made it unclear whether there were significant differences in stem form between the two populations but supported the idea that localized taper equations would provide the best results.