Laura S. Kenefic

Woody debris volume depletion through decay: Implications for biomass and carbon accounting

Woody debris decay rates have recently received much attention because of the need to quantify temporal changes in forest carbon stocks. Published decay rates, available for many species, are commonly used to characterize deadwood biomass and carbon depletion. However, decay rates are often derived from reductions in wood density through time, which when used to model biomass and carbon depletion are known to underestimate rate loss because they fail to account for volume reduction (changes in log shape) as decay progresses. We present a method for estimating changes in log volume through time and illustrate the method using a chronosequence approach. The method is based on the observation, confirmed herein, that decaying logs have a collapse ratio (cross-sectional height/width) that can serve as a surrogate for the volume remaining. Combining the resulting volume loss with concurrent changes in wood density from the same logs then allowed us to quantify biomass and carbon depletion for three study species. Results show that volume, density, and biomass follow distinct depletion curves during decomposition. Volume showed an initial lag period (log dimensions remained unchanged), even while wood density was being reduced. However, once volume depletion began, biomass loss (the product of density and volume depletion) occurred much more rapidly than density alone. At the temporal limit of our data, the proportion of the biomass remaining was roughly half that of the density remaining. Accounting for log volume depletion, as demonstrated in this study, provides a comprehensive characterization of deadwood decomposition, thereby improving biomass-loss and carbon-accounting models.

Habitat diversity in uneven-aged northern hardwood stands: a case study

Habitat characteristics were quantified in an empirically balanced uneven-aged northern hardwood stand in central New York. Canopy structure, wildlife trees, downed woody material, low cover, and richness and abundance of understory vegetation were assessed. High vertical structural diversity and low horizontal patchiness were associated with the single-tree selection system. Downed logs and wildlife trees were spatially well distributed, and cavities at a range of heights and sizes were documented. Application of a selection cutting decreased total canopy closure, but maintained high vertical structural diversity and an even distribution of foliage among canopy strata. Cutting reduced the number of wildlife trees, but increased low cover, shade-intolerant understory vegetation, and the abundance and complexity of downed woody material. This study provides quantifiable evidence of the diversity of habitat characteristics associated with a balanced stand structure and uniform spatial arrangement of different sized trees in uneven-aged northern hardwood stands.

Layer Stacking: A Novel Algorithm for Individual Forest Tree Segmentation from LiDAR Point Clouds

Abstract As light detection and ranging (LiDAR) technology advances, it has become common for datasets to be acquired at a point density high enough to capture structural information from individual trees. To process these data, an automatic method of isolating individual trees from a LiDAR point cloud is required. Traditional methods for segmenting trees attempt to isolate prominent tree crowns from a canopy height model. We here introduce a novel segmentation method, layer stacking, which slices the entire forest point cloud at 1-m height intervals and isolates trees in each layer. Merging the results from all layers produces representative tree profiles. When compared to watershed delineation (a widely used segmentation algorithm), layer stacking correctly identified 15% more trees in uneven-aged conifer stands, 7%–17% more in even-aged conifer stands, 26% more in mixedwood stands, and 26%–30% more (with 75% of trees correctly detected) in pure deciduous stands. Overall, layer stackings commission error was mostly similar to or better than that of watershed delineation. Layer stacking performed particularly well in deciduous, leaf-off conditions, even those where tree crowns were less prominent. We conclude that in the tested forest types, layer stacking represents an improvement in segmentation when compared to existing algorithms.

Nonnative invasive plants in the Penobscot Experimental Forest in Maine, USA: influence of site, silviculture, and land use history.

Abstract We investigated the occurrence of nonnative invasive plants on approximately 175 ha comprising a long-term, 60-year-old U.S. Forest Service silvicultural experiment and old-field stands in the Penobscot Experimental Forest (PEF) in central Maine. Stands in the silvicultural experiment were never cleared for agriculture, but have been repeatedly partially cut. Our objectives were to determine the extent of nonnative invasive plant populations in the PEF, and to relate invasive plant abundance and distribution to management history and environmental factors (overstory composition and basal area, canopy openness, and soil characteristics). We found ten invasive plant species in the study area. Very few occurrences of these were in the silvicultural experiment; where present, invasive plants there appear to be associated with proximity to seed source, and a greater degree of recreational or silvicultural disturbance. Ordination showed that the environmental variables which were associated with invasive species in the old fields were not associated with the presence of invasives in the silvicultural treatments. In the old-field stands, invasive plant cover was positively related to exposed mineral soil and negatively related to organic horizon thickness; invasive plant richness was negatively related to hardwood litter cover. Frangula alnus was the most frequent invasive plant species in both the old-field stands and silvicultural experiment; its distribution was not correlated with observed environmental variables. Control measures are recommended to prevent further encroachment of invasive plants into the silvicultural experiment.

Experimental forests and ranges : 100 years of research success stories

In 2008, Forest Service Research and Development celebrated the Centennial Anniversary of these Experimental Forests and Ranges. This publication celebrates the many scientists who over the course of decades conducted the long-term studies that began and are continuing to shed light on important natural resource issues. Story suggestions were solicited from the Experimental Forest and Range Working Group and were selected to demonstrate the array of research issues being addressed on these living laboratories. Gathering a wealth of information from her interviews with scientists, Gail Wells proceeded to write these “…wonderful success stories from 100 years of research.” Studies established decades ago on many of these sites are still going strong. Experimental forests and ranges provide a valuable, long-term stream of information about the land and its resources. Over the years, researchers have built an impressive body of science to support good land management and further understanding of natural processes. Their research sheds light on many important questions. These experimental forests serve as living laboratories that help us connect the future to the past.

Proceedings of the conference on diameter-limit cutting in northeastern forests

Contains nine papers presented at the conference on diameter-limit cutting in northeastern forests on May 23-24, 2005, at the University of Massachusetts at Amherst. NOTE, this is the full-text document. Individual papers are available via Treesearch.

Development of the Selection System in Northern Hardwood Forests of the Lake States: An 80-Year Silviculture Research Legacy

The northern hardwood research program at the Dukes Experimental Forest in Michigan and Argonne Experimental Forest in Wisconsin has been adapting to changing management and social objectives for more than 80 years. In 1926, the first northern hardwood silviculture study was established in old-growth stands at the Dukes Experimental Forest. In response to social demands for more “natural” forestry, the study included then-contemporary practices (e.g., liquidation of old-growth forest) and new approaches (e.g., partial cuttings). By 1953, the partial cutting treatments were deemed most sustainable (Eyre and Zillgitt, Partial cuttings in northern hardwoods of the Lake States: twenty-year experimental results. Technical Bulletin LS-1076, 1953), and led to the creation of an uneven-aged stand structural guide that is still widely used today: the famed “Arbogast Guide” (Marking guides for northern hardwoods under the selection system. Station Paper 56, 1957). Charismatic figures such as Raphael Zon, Windy Eyre, William Zillgitt, and Carl Arbogast Jr. were important to establishing this research and its early application in the Lake States region. Since then, research at the Dukes and Argonne Experimental Forests has expanded to evaluate a range of management alternatives for northern hardwood forests, including approaches designed to sustain biodiversity, habitat, and timber production. In addition, the long-term studies provide new opportunities for larger-scale applications and research unforeseen at the studies’ establishment. The lessons learned from the 80 years of research on northern hardwood ecosystems at the Dukes and Argonne Experimental Forests have led to numerous publications and management guides and have impacted thousands of forestry professionals and millions of hectares of land.

Sixty Years of Silviculture in a Northern Conifer Forest in Maine, USA

In 1950, the US Forest Service initiated a cutting practice level (CPL) study on the Penobscot Experimental Forest in Maine on the basis of findings of a national appraisal of forestland management. Silvicultural treatments, including the selection system with 5and 15-year cutting cycles, fixed diameter-limit cutting, and variants of commercial clearcutting, were chosen to represent “High-order,” “Good,” “Fair,” and “Poor” cutting practices as then defined for eastern spruce–fir (Picea–Abies; northern conifer) forests. After 60 years, selection treatments have maintained a wide distribution of tree sizes, increased the proportion of mature spruce, and decreased the proportion of hardwoods; selection cutting on a 15-year cycle resulted in the highest current stand value. Fixed diameter-limit cutting resulted in the greatest harvest revenue but degraded residual stand composition, structure, and value. Outcomes of commercial clearcutting varied as a function of treatment (none, repeated harvest, or rehabilitation) after the first harvest. After 60 years, the proportion of acceptable growing stock was highest in selection and rehabilitation treatments and lowest in fixed diameter-limit and commercial clearcut treatments. Findings confirm that long-term outcomes of silvicultural treatments with attention to residual stand condition surpass those managed for short-term financial gains with regard to residual stand structure, value, and quality.

Sampling and measurement protocols for long-term silvicultural studies on the Penobscot Experimental Forest

The U.S. Forest Service, Northern Research Station has been conducting research on the silviculture of northern conifers on the Penobscot Experimental Forest (PEF) in Maine since 1950. Formal study plans provide guidance and specifications for the experimental treatments, but documentation is also needed to ensure consistency in data collection and sampling protocols. This guide details current sampling and measurement protocols for three of the longest running Forest Service experiments on the PEF: (1) the management intensity demonstration (1950 to present), (2) the compartment management study (1952 to present), and (3) the auxiliary selection cutting study (1953-present). Each of these long-term stand-scale experiments use plot-based measurements of trees taken at periodic intervals. Additional data collected vary and include regeneration, recruitment, and mortality; amount, size, and decay of dead wood; and stand structural characteristics such as heights, crown dimensions, and spatial locations of trees. Descriptions provided here are the basis for data collection in the relevant studies on the PEF, inform interpretation of the published databases, and serve as a model for silvicultural studies elsewhere.

Northeastern Conifer Research: Multiple Species and Multiple Values

The northern conifer, or spruce-fir, forest of the northeastern USA and adjacent Canada has had a defining influence on the economy and culture of the region. The same can be said of the USDA Forest Service’s research in this forest, which began more than 100 years ago. Forest Service research has evolved since that time in response to changes in the needs and prominence of the forest industry, and in public attitudes and concerns. Early studies of forest protection and rehabilitation first gave way to mid-century research on production forestry, then to twenty-first-century research on forest ecology. Though various lines of research have come and gone, long-term studies on the region’s experimental forests continue to provide a unique perspective on the structure and dynamics of the forest, and the outcomes of silvicultural alternatives.