Scholarly Works, Forest Resources and Environmental Conservation

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Research articles, presentations, and other scholarship

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On Estimating the Aboveground Weights of Tree Stands
Madgwick, H. A. I.; Satoo, T. (Ecological Society of America, 1975)
Simulated sampling of nine tree stands was used to compare estimated stand component weights with known weights based on complete harvest. On average, estimates based on regressions of logarithm weight on either logarithm tree diameter or on logarithm (diameter)2 x height overestimated weights of stems, branches, and leaves by - 3% when the inherent bias of such regressions was accounted for. Ninety-five percent confidence intervals based on random sampling encompassed the measured stand weights 79%-100% of the time. Similar confidence intervals using stratified random sampling based on tree diameter encompassed the measured stand weights only 44%-98% of the time. The small average bias in estimates of stand weight using logarithmic regressions is of minor importance compared with the variation in estimates among replicated samples.
Sound transmission loss of gypsum wallboard wall partitions
Green, David W.; Sherry, C. W. (Acoustical Society of America, 1977)
Using the data bank of the acoustic laboratory of Domtar Research, statistical equations based on frequency and surface density were derived for predicting sound transmission loss (STL) and sound transmission class (STC) of double leaf wall partitions constructed using gypsum wallboard and either steel or wood studs. The equations show close agreement with experimental data for all frequency bands except those near the coincidence dip. Results predicted using these equations also agree closely with experimental results published by other laboratories. Using these equations the effect of frequency, surface density and cavity filler on STL and STC is easily seen. However, the study also revealed some unexpected results whether or not a partition was (1): Balanced- as to board placement did not significantly affect the STC of either steel or wood stud partitions. (2) For multilayer wood stud partitions attaching the second layer of board to the first with screws, rather than using glue, dramatically reduced the STL at higher frequencies. For higher surface density partitions this decrease may negate any benefits to be derived from adding fiberglass to the cavity space.
Proceedings of a Symposium on Yellow-Poplar Construction Lumber: an Emerging Development Opportunity for Southwest Virginia
Muench, John; Frame, Elvin D.; Deal, Earl L.; Haley, Jerry; Porter, James K.; Smith, Thomas K.; Johnson, Thomas G. (LMA Research & Education Foundation, 1989)
The proceedings highlight the potential for the establishment of a construction lumber industry based on yellow-poplar in Southwest Virginia and the new capital investments and innovations in production and marketing that would be needed to make it a success.
Postoptimal linear programming analysis of farm machinery
Bender, D. A.; Kline, D. Earl; McCarl, Bruce A. (American Society of Agricultural and Biological Engineers, 1990)
Linear programming (LP) is a widely used technique for farm machinery selection. Shadow prices from LP models are typically used to identify farm machinery bottlenecks. Shadow prices represent the value of an additional unit of a scarce resource, such as planter hours during a given time period. This shadow price approach can be misleading since a machinery change may affect the usages of other scarce resources, such as tractors and labor. A postoptimality algorithm is presented which improves on the shadow price approach. This algorithm gives detailed information on the effects of a machinery change on all relevant tractor and labor resources. This information is useful for investigating complex machinery interactions. The postoptimality algorithm is illustrated with a case study in Texas.
Accuracy of Visible and Ultraviolet Light for Estimating Live Root Proportions with Minirhizotrons
Wang, Z. Q.; Burch, W. H.; Mou, P.; Jones, R. H.; Mitchell, R. J. (Ecological Society of America, 1995-10)
Spatial and Temporal Variation in Soil and Vegetation Impacts on Campsites
Marion, Jeffrey L.; Cole, D. N. (Ecological Society of America, 1996-05)
We studied the impacts of camping on soil and vegetation at Delaware Water Gap National Recreation Area. We assessed the magnitude of impact on campsites that varied in amount of use and in topographic position. We also evaluated change over a 5-yr period on long-established, recently opened, and recently closed campsites, as well as on plots subjected to experimental trampling. Campsite impacts were intense and spatially variable. Amount of use and topographic position explained some of this variation. Soil and vegetation conditions changed rapidly when campsites were initially opened to use and when they were closed to use. Changes were less pronounced on the long-established campsites that remained open to use. In the trampling experiments, impact varied greatly with trampling intensity and between vegetation types. An open-canopy grassland vegetation type was much more resistant to trampling than a forb-dominated forest vegetation type. Campsite impacts increased rapidly with initial disturbance, stabilized with ongoing disturbance, and-in contrast to what has been found in most other studies-decreased rapidly once disturbance was terminated. Implications of these results for campsite management strategies, such as use concentration or dispersal, and rotation or closure of campsites, are discussed.
Global patterns of lake ice phenology and climate: Model simulations and observations
Walsh, Sinead E.; Vavrus, Stephen J.; Foley, Jonathan A.; Fisher, Veronica A.; Wynne, Randolph H.; Lenters, John D. (American Geophysical Union, 1998-11-27)
Lake ice phenology parameters (dates of ice onset and thaw) provide an integrative climatic description of autumn to springtime conditions. Interannual variations in lake ice duration and thickness allow estimates of local climatic variability. In addition, long-term changes in lake ice phenology may provide a robust indication of climatic change. The relationship between lake ice and climate enables the use of process-based models for predicting the dates of freeze-up and thaw. LIMNOS (Lake Ice Model Numerical Operational Simulator) is one such model, which was originally designed to simulate the ice phenology of several lakes in southern Wisconsin. In this study, LIMNOS is modified to run globally on a 0.5° by 0.5° latitude-longitude grid using average monthly climate data. We initially simulate the ice phenology for lakes of 5- and 20-m mean depths across the northern hemisphere to demonstrate the effects of lake depth, latitude, and elevation on ice phenology. To evaluate the results of LIMNOS we also simulate the ice phenology of 30 lakes across the northern hemisphere which have long-term ice records. LIMNOS reproduces the general geographic patterns of ice-on and ice-off dates, although ice-off dates tend to occur later in the model. Lakes with extreme depths, surface areas, or precipitation are simulated less accurately than small, shallow lakes. This study reveals strengths and weaknesses of LIMNOS and suggests aspects which need improving. Future investigations should focus on the use of geographically extensive lake ice observations and modeling to elucidate patterns of climatic variability and/or climate change.
Sampling-Skewed Biological Populations: Behavior of Confidence Intervals for the Population Total
Gregoire, Timothy G.; Schabenberger, Oliver (Ecological Society of America, 1999-04)
Four populations were repeatedly sampled with the aim of examining interval estimation of the cumulative amount, T, of some characteristic that has a positively skewed distribution, a feature of many biological populations. With samples of various sizes, the empirical sampling distribution of the simple expansion estimator was remarkably symmetric and approximately normal, as was that of the customary ratio-of-means estimator. While the nominal coverage rate of (1 - alpha)100% intervals based on the Student's t distribution was nearly achieved in all cases, there was a substantially greater tendency for such intervals to fail from below rather than above. This behavior is attributed to the strong positive correlation between the estimator of the population total and the corresponding estimator of its variance when sampling from a finite, and perforce nonnormal, population.
Laboratory measurements and modeling N mineralization potential in Virginia Coastal Plain agricultural, fallow, and forest soils
Shukla, S.; Mostaghimi, Saied; Burger, James A. (American Society of Agricultural and Biological Engineers, 2000)
A long-term aerobic incubation and leaching technique was used to measure N mineralization of surface and subsurface soils (sandy loam) from agricultural,forest, and fallow sites in a Virginia Coastal Plain watershed. N mineralization potential was measured to refine models used to describe this process in a watershed-scale nutrient export assessment. Potentially mineralizable N (N-0) and reaction rate constants (k) were estimated using a first-order model and a nonlinear regression procedure. Large variations in cumulative N mineralized, N-0, and k, were found for the surface soils from agricultural areas. Forest soils had much higher potentially mineralizable N than agricultural soils. For subsurface soils, the differences among land uses were less variable than those observed for the surface soils. The first order model (single-pool approach) was adequate for predicting N mineralization in surface soils from agricultural and fallow areas, but less suitable for forest surface soils. Consideration of a double exponential (two-pool approach) model did not improve the performance of N mineralization prediction for forested or agricultural soils. Large variations occurred in the field-predicted values of mineralized N due to temperature and moisture ranges commonly occurring throughout the season. Variability in the N mineralization potential of soils in the watershed suggests that individual k and N-0 should be derived for soils with similar properties to obtain better predictions of N mineralization and thus N movement to groundwater.
Effects of forest harvesting best management practices on surface water quality in the Virginia coastal plain
Thompson, Theresa M.; Mostaghimi, Saied; Frazee, J. W.; McClellan, P. W.; Shaffer, R. M.; Aust, W. Michael (American Society of Agricultural and Biological Engineers, 2000)
Three small watersheds located in Westmoreland County, Virginia, were monitored to evaluate the impact of forest clearcutting on surface water quality and to evaluate the effectiveness of forestry best management practices (BMPs) for minimizing hydrologic and water quality impacts associated with timber harvesting. One watershed (7.9 ha) was clearcut without implementation of BMPs, one watershed (8.5 ha) was clearcut with the implementation of BMPs and a third watershed (9.8 ha) was left undisturbed as a control Forest clearcutting without BMP implementation reduced storm runoff volume and did not significantly change peak flow rates. Following site preparation, both storm flow volumes and peak flow rates decreased significantly. For the watershed with BMP implementation, storm flow volume decreased significantly following harvest, while peakflow increased. Site preparation did not change storm flow volumes over post-harvest conditions, bur did significantly reduce storm peak flow rates. Disruptions in subsurface flow pathways during harvest or rapid growth of understory vegetation following harvest could have caused these hydrologic changes. Harvest and site preparation activities significantly increased the loss of sediment and nutrients during storm events, Storm event concentrations and loadings of sediment, nitrogen, and phosphorus increased significantly following forest clearcutting and site preparation of the No-BMP watershed. Both the BMP watershed and the Control watershed showed few changes in pollutant storm concentrations or loadings throughout the study. Results of this study indicate forest clearcutting and site preparation without BMPs can cause significant increases in sediment and nutrient concentrations and loadings in the Virginia Coastal Plain. However these impacts can be greatly reduced by implementing a system of BMPs on the watershed during harvesting activities.
Etude de 50 annees de changements d'occupation des terres dans la commune rurale de Madiama cercle Djenne
Wynne, Randolph H.; Sengupt, N.; Touré, M. (2004)
Effectiveness of a confinement strategy for reducing campsite impacts in Shenandoah National Park
Reid, Scott Edmonds; Marion, Jeffrey L. (Cambridge University Press, 2004-12)
The expansion and proliferation of backcountry campsites is a persistent problem in many parks and protected areas. Shenandoah National Park (SNP) has one of the highest backcountry overnight use densities in the USA national parks system. SNP managers implemented a multi-option backcountry camping policy in 2000 that included camping containment with established campsites. These actions were intended to reduce the number of campsites and the area of camping disturbance at each site. This paper describes a longitudinal adaptive management assessment of the new campsite policies, applying quantitative measures of campsite conditions to evaluate the efficacy of management interventions. Physical campsite measurements combined with qualitative visitor interviews indicated SNP had successfully reduced the number of campsites and aggregate measures of camping-related disturbance in the Park, while minimizing the use of regulations, site facilities and staff resources. Implications for managers of other protected areas are that an established site camping policy can minimize camping disturbance, including the number and size of campsites, provided managers can sustain rehabilitation efforts to close and restore unneeded campsites. Experiential attributes, such as the potential for solitude, can also be manipulated through control over the selection of established campsites. Integrating resource and social science methods also provided a more holistic perspective on management policy assessments. Adaptive management research provided a timely evaluation of management success while facilitating effective modifications in response to unforeseen challenges. Conclusions regarding the effectiveness of a visitor impact containment strategy involving an established site camping option are offered.
Comparison of standard exponential and linear techniques to amplify small cDNA samples for microarrays
Wadenbäck, Johan; Clapham, David H.; Craig, Deborah; Sederoff, Ronald; Peter, Gary F.; von Arnold, Sara; Egertsdotter, Ulrika (2005-05-04)
Background The need to perform microarray experiments with small amounts of tissue has led to the development of several protocols for amplifying the target transcripts. The use of different amplification protocols could affect the comparability of microarray experiments. Results Here we compare expression data from Pinus taeda cDNA microarrays using transcripts amplified either exponentially by PCR or linearly by T7 transcription. The amplified transcripts vary significantly in estimated length, GC content and expression depending on amplification technique. Amplification by T7 RNA polymerase gives transcripts with a greater range of lengths, greater estimated mean length, and greater variation of expression levels, but lower average GC content, than those from PCR amplification. For genes with significantly higher expression after T7 transcription than after PCR, the transcripts were 27% longer and had about 2 percentage units lower GC content. The correlation of expression intensities between technical repeats was high for both methods (R2 = 0.98) whereas the correlation of expression intensities using the different methods was considerably lower (R2 = 0.52). Correlation of expression intensities between amplified and unamplified transcripts were intermediate (R2 = 0.68-0.77). Conclusion Amplification with T7 transcription better reflects the variation of the unamplified transcriptome than PCR based methods owing to the better representation of long transcripts. If transcripts of particular interest are known to have high GC content and are of limited length, however, PCR-based methods may be preferable.
Genome-wide analysis of Aux/IAA and ARF gene families in Populus trichocarpa
Kalluri, Udaya C.; DiFazio, Stephen P.; Brunner, Amy M.; Tuskan, Gerald A. (2007-11-06)
Background Auxin/Indole-3-Acetic Acid (Aux/IAA) and Auxin Response Factor (ARF) transcription factors are key regulators of auxin responses in plants. We identified the suites of genes in the two gene families in Populus and performed comparative genomic analysis with Arabidopsis and rice. Results A total of 35 Aux/IAA and 39 ARF genes were identified in the Populus genome. Comparative phylogenetic analysis revealed that several Aux/IAA and ARF subgroups have differentially expanded or contracted between the two dicotyledonous plants. Activator ARF genes were found to be two fold-overrepresented in the Populus genome. PoptrIAA and PoptrARF gene families appear to have expanded due to high segmental and low tandem duplication events. Furthermore, expression studies showed that genes in the expanded PoptrIAA3 subgroup display differential expression. Conclusion The present study examines the extent of conservation and divergence in the structure and evolution of Populus Aux/IAA and ARF gene families with respect to Arabidopsis and rice. The gene-family analysis reported here will be useful in conducting future functional genomics studies to understand how the molecular roles of these large gene families translate into a diversity of biologically meaningful auxin effects.
Diversity-invasibility across an experimental disturbance gradient in Appalachian forests
Belote, R. T.; Jones, R. H.; Hood, S. M.; Wender, B. W. (Ecological Society of America, 2008-01)
Research examining the relationship between community diversity and invasions by normative species has raised new questions about the theory and management of biological invasions. Ecological theory predicts, and small-scale experiments confirm, lower levels of nonnative species invasion into species-rich compared to species-poor communities, but observational studies across a wider range of scales often report positive relationships between native and nonnative species richness. This paradox has been attributed to the scale dependency of diversity-invasibility relationships and to differences between experimental and observational studies. Disturbance is widely recognized as an important factor determining invasibility of communities, but few studies have investigated the relative and interactive roles of diversity and disturbance on nonnative species invasion. Here, we report how the relationship between native and nonnative plant species richness responded to an experimentally applied disturbance gradient (from no disturbance up to clearcut) in oak-dominated forests. We consider whether results are consistent with various explanations of diversity-invasibility relationships including biotic resistance, resource availability, and the potential effects of scale (I m 2 to 2 ha). We found no correlation between native and normative species richness before disturbance except at the largest spatial scale, but a positive relationship after disturbance across scales and levels of disturbance. Post-disturbance richness of both native and normative species was positively correlated with disturbance intensity and with variability of residual basal area of trees. These results suggest that more nonnative plants may invade species-rich communities compared to species-poor communities following disturbance.
Edaphic and climatic effects on forest stand development, net primary production, and net ecosystem productivity simulated for Coastal Plain loblolly pine in Virginia
Sampson, Deborah A.; Wynne, Randolph H.; Seiler, John R. (American Geophysical Union, 2008-01-11)
We used SECRETS-3PG to simulate net primary production (NPP) and net ecosystem productivity (NEP) of loblolly pine (Pinus taeda L.) growing on the Virginia Coastal Plain, focusing on the effects of soils and climate, and stand age over a 30-year rotation. Soil type was influential, with heavier soils having greater NEP earlier in the rotation than lighter, sandier soils, although these differences disappeared by the rotation end. Climate had only a small effect. Stand age had the largest effect, with simulated annual NEP strongly negative during the first 5 to 8 years of development but peaking at +600 g C m-² a-¹ by age 13. Modest declines in NEP after 13 years were associated with declines in LAI as stands aged. The 30-year mean annual NEP was positive over most of the study area but in a few cases was indistinguishable from zero for northwestern portions of the study. Simulated annual NPP rose from zero to over 2300 g biomass m-² a-¹ by age 12, after which it declined to ~1700 g biomass m-² a-¹ by rotation end. These results suggest that loblolly pine plantations on the Coastal Plain of Virginia may become net annual C sinks 5 to 9 years after planting but that when averaged over a whole rotation the net carbon accumulation during the baseline rotation simulated here is indistinguishable from zero. Our results also suggest, however, that this finding is sensitive to the length of the rotation, soil type (and thus fertility), and climate, implying that changes in management practices could significantly influence the carbon balance in managed loblolly pine plantations.
Effect of Fluid Shear Stress on Endocytosis of Heparan Sulfate and Low-density Lipoproteins
Barkefors, Irmeli; Aidun, Cyrus K.; Egertsdotter, Ulrika (Hindawi, 2008-01-24)
Hemodynamic stress is a critical factor in the onset of atherosclerosis such that reduced rates of shear stress occurring at regions of high curvature are more prone to disease. The level of shear stress has direct influence on the thickness and integrity of the glycocalyx layer. Here we show that heparan sulfate, the main component of the glycocalyx layer, forms an intact layer only on cell surfaces subjected to shear, and not under static conditions. Furthermore, receptor-mediated endocytosis of heparan sulfate and low-density liporoteins is not detectable in cells exposed to shear stress. The internalized heparan sulfate and low-density lipoproteins are colocalized as shown by confocal imaging.
Growth, Collapse, and Reorganization of the Annapurna Conservation Area, Nepal: an Analysis of Institutional Resilience
Baral, Nabin; Stern, Marc J.; Heinen, J. T. (Resilience Alliance, 2010)
Community-based conservation institutions can be conceptualized as complex adaptive systems that pass through a cycle of growth, maturation, collapse, and reorganization. We test the applicability of this four-phase adaptive cycle in the institutional context of the Annapurna Conservation Area (ACA), Nepal. We use the adaptive cycle to assess changes in structures and processes and to explore the past, present, and possible future trends in ACA. We focus on the crisis brought about by the Maoist insurgency and changes that took place in ACA during and after this period. Our analysis suggests that the conservation institution has passed through one and a half forms of the adaptive cycle in five major historical periods in the Annapurna region since 1960. It also appears to have been resilient to the insurgency because the system maintained its identity throughout, avoided alternative undesirable states, and entered into the reorganization phase following collapse. All forms of capital and institutional performance decreased to some extent during collapse, but flexible nested governance structures, including the devolution of responsibility to local entities, the maintenance of capital stocks, the retention of institutional memory, and the perceptions of institutional legitimacy among constituencies, facilitated reorganization. The institutional system is reorganizing along the original regime, but it has also developed an alternative pathway that will transform it in the near term. We evaluate the usefulness, strengths, and weaknesses of the adaptive cycle analogy in this application.
Threshold changes in storm runoff generation at a till-mantled headwater catchment
Detty, J. M.; McGuire, Kevin J. (American Geophysical Union, 2010-07-20)
A small research watershed in the Hubbard Brook Experimental Forest in New Hampshire was equipped with a spatially distributed instrument network designed to continuously monitor hydrometric responses in the shallow subsurface. We analyzed rainfall events during seasonal wet up from late summer through autumn to investigate the mechanisms of runoff generation and the patterns of rainfall!runoff response at the catchment outlet. Our results show that storm quick flow depths displayed a threshold relationship with two independently measured soil moisture indices: a maximum water table height index and the sum of gross precipitation and antecedent soil moisture. Quick flow depths during events with below!threshold criteria were not significantly correlated with either index, while quick flow depths during events with above!threshold criteria were strongly correlated with both indices (r ! 0.98). The effective runoff contributing area (estimated by event runoff ratios) also changed significantly between above! and below!threshold conditions, as did the synchronicity between groundwater fluctuations and streamflow. Below the threshold, we inferred that catchment runoff was generated primarily in the near!stream zones, while above the threshold the contributing area likely expanded laterally onto neighboring hillslopes. Our results show that the effective saturated hydraulic conductivity appeared to increase significantly during runoff events with above!threshold conditions, possibly owing to water tables rising into highly transmissive near!surface soils. We believe the observed threshold pattern may partially be explained as a transmissivity feedback mechanism and/or preferential flows through macropore networks which allowed for a rapid expansion of the runoff contributing area onto hillslopes, resulting in increased runoff yields. continuously monitor hydrometric responses in the shallow subsurface. We analyzed rainfall events during seasonal wet up from late summer through autumn to investigate the mechanisms of runoff generation and the patterns of rainfall!runoff response at the catchment outlet. Our results show that storm quick flow depths displayed a threshold relationship with two independently measured soil moisture indices: a maximum water table height index and the sum of gross precipitation and antecedent soil moisture. Quick flow depths during events with below!threshold criteria were not significantly correlated with either index, while quick flow depths during events with above!threshold criteria were strongly correlated with both indices (r ! 0.98). The effective runoff contributing area (estimated by event runoff ratios) also changed significantly between above! and below!threshold conditions, as did the synchronicity between groundwater fluctuations and streamflow. Below the threshold, we inferred that catchment runoff was generated primarily in the near!stream zones, while above the threshold the contributing area likely expanded laterally onto neighboring hillslopes. Our results show that the effective saturated hydraulic conductivity appeared to increase significantly during runoff events with above!threshold conditions, possibly owing to water tables rising into highly transmissive near!surface soils. We believe the observed threshold pattern may partially be explained as a transmissivity feedback mechanism and/or preferential flows through macropore networks which allowed for a rapid expansion of the runoff contributing area onto hillslopes, resulting in increased runoff yields.
Hydrological connectivity of hillslopes and streams: Characteristic time scales and nonlinearities
McGuire, Kevin J.; McDonnell, J. J. (American Geophysical Union, 2010-10-30)
Subsurface flow from hillslopes is widely recognized as an important contributor to streamflow generation; however, processes that control how and when hillslopes connect to streams remain unclear. We investigated stream and hillslope runoff dynamics through a wet‐up period in watershed 10 of the H. J. Andrews Experimental Forest in the western Cascades of Oregon where the riparian zone has been removed by debris flows. We examined the controls on hillslope‐stream connectivity on the basis of observations of hydrometric, stable isotope, and applied tracer responses and computed transit times for multiple runoff components for a series of storms during the wet‐up phase of the 2002–2003 winter rainy season. Hillslope discharge was distinctly threshold‐like with a near linear response and average quick flow ratio of 0.58 when antecedent rainfall was greater than 20 mm. Hillslope and stream stormflow varied temporally and showed strong hysteretic relationships. Event water mean transit times (8–34 h) and rapid breakthrough from applied hillslope tracer additions demonstrated that subsurface contributing areas extend far upslope during events. Despite rapid hillslope transport processes during events, soil water and runoff mean transit times during nonstorm conditions were greater than the time scale of storm events. Soil water mean transit times ranged between 10 and 25 days. Hillslope seepage and catchment base flow mean transit times were between 1 and 2 years. We describe a conceptual model that captures variable physical flow pathways, their synchronicity, threshold activation, hysteresis, and transit times through changing antecedent wetness conditions that illustrate the different stages of hillslope and stream connectivity.

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