Central Hardwood Forest Research Articles

Modeling the Effects of Harvest Alternatives on Mitigating Oak Decline in a Central Hardwood Forest Landscape

Oak decline is a process induced by complex interactions of predisposing factors, inciting factors, and contributing factors operating at tree, stand, and landscape scales. It has greatly altered species composition and stand structure in affected areas. Thinning, clearcutting, and group selection are widely adopted harvest alternatives for reducing forest vulnerability to oak decline by removing susceptible species and declining trees. However, the long-term, landscape-scale effects of these different harvest alternatives are not well studied because of the limited availability of experimental data. In this study, we applied a forest landscape model in combination with field studies to evaluate the effects of the three harvest alternatives on mitigating oak decline in a Central Hardwood Forest landscape. Results showed that the potential oak decline in high risk sites decreased strongly in the next five decades irrespective of harvest alternatives. This is because oak decline is a natural process and forest succession (e.g., high tree mortality resulting from intense competition) would eventually lead to the decrease in oak decline in this area. However, forest harvesting did play a role in mitigating oak decline and the effectiveness varied among the three harvest alternatives. The group selection and clearcutting alternatives were most effective in mitigating oak decline in the short and medium terms, respectively. The long-term effects of the three harvest alternatives on mitigating oak decline became less discernible as the role of succession increased. The thinning alternative had the highest biomass retention over time, followed by the group selection and clearcutting alternatives. The group selection alternative that balanced treatment effects and retaining biomass was the most viable alternative for managing oak decline. Insights from this study may be useful in developing effective and informed forest harvesting plans for managing oak decline.

Effects of forest composition on trophic relationships among mast production and mammals in central hardwood forest

Abstract Oak-dominated forest has declined in the eastern United States as shade-tolerant mesophytic species (e.g., maple [Acer spp.]) replace oaks (Quercus spp.), sparking concern among ecologists regarding species that consume acorns. Our goal was to describe how increasing mesophication of oak forests may affect consumers in higher trophic levels. We investigated relationships among forest composition, mast production, small-mammal density, and carnivore occurrence in 8 stands representing a gradient of oak–hickory dominance in central hardwood forest in southern Illinois. We livetrapped small mammals for >24,000 trap-nights in June–August 2009–2011 with trapping webs to estimate population density of mice (Peromyscus spp.). We collected mast seeds during October–November 2009–2010 and calculated average dry biomass (g/m2) for each species and stand. During winters 2009–2011, we photographed carnivores using baited camera traps. We regressed mast biomass on measures of forest composition and regressed ...

The Effects of Extreme Drought on Native Forage Nutritional Quality and White-Tailed Deer Diet Selection

Forage availability is often used as a measure of habitat quality for Odocoi- leus virginianus (White-tailed Deer; hereafter Deer). Many studies have evaluated treatment effects on forage availability, but the effects of other abiotic factors, such as drought, on native forages and Deer diet selection are poorly understood. We measured diet selection and nutritional quality of commonly occurring forages following extreme drought (2007) and normal rainfall years (2008) in 4 closed-canopied hardwood stands in the Central Hardwoods region. Deer selected 6 forage species in both years of the study. Within these 6 species, crude protein (CP) and acid detergent fiber (ADF) were not different, and neutral detergent fiber (NDF) increased during the year of normal rainfall. Thirteen other commonly occurring forages showed a different trend, with CP negatively affected by drought and ADF and NDF unaffected. Less-selected species in the drought year and a greater selection-index cut-off value suggest Deer were more selective of species consumed during extreme drought because fewer plants met their nutritional requirements. Our data support the selective quality hypothesis, predicting Deer become more selective of plant species to meet nutritional requirements when resources are lim- ited. Our data suggest more frequent and intense droughts predicted as a result of global climate change may influence diet selection of deer and decrease forage quality enough to limit lactation during the late-summer stress period in the Southeast.

Canopy accession strategies and climate-growth relationships in Acer rubrum

A pervasive pattern of forest composition change is occurring throughout the Central Hardwood Forest of the eastern US. Acer rubrum has invaded the understory of Quercus stands across a variety of site types. The proliferation of A. rubrum, and that of other shade-tolerant mesophytes, inhibits the regeneration of Quercus. Without alterations in disturbance or climate regimes, composition in invaded stands is expected to shift towards A. rubrum dominance. Canopy accession strategies and climate-growth relationships of A. rubrum are critical factors in this successional shift. We quantified patterns of suppression and release during canopy accession, examined the relationships between climate variables and radial growth, and compared our findings for A. rubrum in an old-growth forest in Tennessee to other studies throughout the region to elucidate broad-scale patterns. The most common mode of A. rubrum canopy recruitment began with a tree originating in a gap followed by accession into the canopy without a period of suppression (61%). The remaining trees experienced a period of suppression before recruiting to the main canopy. A prominent establishment pulse occurred from the 1940s to the 1960s and 93% of trees that recruited to the canopy during this period established in gaps and were never suppressed. The mean age at canopy accession for individuals that experienced suppression was 24yr. The transition from suppression to release phases in radial growth trends was abrupt. The mean interseries correlation and the average mean sensitivity of the A. rubrum tree-ring chronology were comparatively high for the region. Acer rubrum individuals were most productive during cool, wet springs preceded by wet autumns and warm winters. Our results indicate that A. rubrum will remain competitive in the coming decades without a change in current disturbance regimes and the Quercus component will be difficult for managers to maintain in similar stands of the Central Hardwood Forest.

Short-Term Forest Management Effects on a Long-Lived Ectotherm

Timber harvesting has been shown to have both positive and negative effects on forest dwelling species. We examined the immediate effects of timber harvests (clearcuts and group selection openings) on ectotherm behavior, using the eastern box turtle as a model. We monitored the movement and thermal ecology of 50 adult box turtles using radiotelemetry from May–October for two years prior to, and two years following scheduled timber harvests in the Central Hardwoods Region of the U.S. Annual home ranges (7.45 ha, 100% MCP) did not differ in any year or in response to timber harvests, but were 33% larger than previous estimates (range 0.47–187.67 ha). Distance of daily movements decreased post-harvest (from 22 m±1.2 m to 15 m±0.9 m) whereas thermal optima increased (from 23±1°C to 25±1°C). Microclimatic conditions varied by habitat type, but monthly average temperatures were warmer in harvested areas by as much as 13°C. Animals that used harvest openings were exposed to extreme monthly average temperatures (∼40°C). As a result, the animals made shorter and more frequent movements in and out of the harvest areas while maintaining 9% higher body temperatures. This experimental design coupled with radiotelemetry and behavioral observation of a wild ectotherm population prior to and in response to anthropogenic habitat alteration is the first of its kind. Our results indicate that even in a relatively contiguous forested landscape with small-scale timber harvests, there are local effects on the thermal ecology of ectotherms. Ultimately, the results of this research can benefit the conservation and management of temperature-dependent species by informing effects of timber management across landscapes amid changing climates.

Accelerated succession following an intense wind storm in an oak-dominated forest

Catastrophic wind events often contribute to stand dynamics of central hardwood forests, yet opportunities to study them are limited. As luck would have it, we sampled 54 long-term monitoring plots (0.04ha) on the Shawnee National Forest in southern Illinois prior to an intense 2009 windstorm that swept across the central United States. The sampled plots, which were resampled immediately after the storm, were situated across a gradient of topographic positions. Overstory trees (⩾6.6cmdbh), saplings (⩾1m tall and <6.6cmdbh), and seedlings (<1m tall) were tallied and recorded by species within each plot and used to document post-storm changes in community composition and density. Prior to the storm, species abundance differed among the three strata, and within each strata tree communities were most closely related to slope position and elevation. This relationship did not change after the storm, however there was a shift in species composition of the overstory and seedling strata. Due in part to their overwhelming pre-windstorm abundance, oaks suffered greater losses compared to non-oak species in the overstory strata, accounting for 62% and 53% of all reductions in basal area and stem density, respectively. The lack of understory oak and release of more shade-tolerant species in the understory by the wind storm could potentially accelerate succession. Although wind has likely always played a role in the disturbance regime of central hardwood forests, the effect of wind events has changed with increased fire suppression and threatens the perpetuity of oak-dominated forests in this region.

Understory light regimes following silvicultural treatments in central hardwood forests in Kentucky, USA

Manipulation of the light regime is a primary goal of many silvicultural treatments, but the specific light conditions created remain poorly documented for many forest types and geographic locations. To help quantify effects of silvicultural treatments on light conditions, measurements of basal area, canopy cover, and photosynthetically active radiation (PAR), measured both instantaneously and across time, were collected in central hardwood forests in Kentucky, USA following silvicultural treatments. These measurements were used to: (1) Investigate the magnitudes of differences in understory percent ambient PAR following implementation of shelterwood with reserves and thinning treatments; (2) document the spatial and temporal distribution and variability of understory percent ambient PAR in shelterwood with reserves treatments (mean residual basal area=5.2m2/ha), thinning treatments (18.5m2/ha), and untreated controls (27.1m2/ha); and (3) examine relationships between: basal area and canopy cover; basal area and measured percent ambient PAR; and canopy cover and measured percent ambient PAR.Mean light levels from instantaneous measurements were 78% of ambient in the shelterwood with reserves, 33% of ambient in the thinning and 9% of ambient in the control. Similarly, only 1.3% of the approximately 140h of PAR measurements in the controls indicated high light conditions (>60% of ambient), 15.9% in the thinning treatment and 65.4% in the shelterwood with reserves treatment. There were only 32 periods of high light found across all plots in the control, 176 periods of high light in the thinning treatment, and 441 periods of high light in the shelterwood with reserves treatment. Indexes of variability in light across time and among sampling locations within a stand did not differ statistically between the shelterwood with reserves and thinning treatments but both treatments were statistically more spatially and temporally variable than the uncut control. Simple linear regression relationships were observed between stand basal area and mean relative PAR (r2=0.8784 for instantaneous measurements, r2=0.9697 for continuous measurements), and basal area and canopy cover (r2=0.8479). Such relationships provide a means for including light management in forest planning and application of silvicultural treatments. The results for the distribution of light also suggest, however, that treated stands may have similar mean light levels, but differ substantially in the spatial and temporal distribution of light.

Repeated prescribed fires alter gap-phase regeneration in mixed-oak forests

Oak dominance is declining in the central hardwoods region, as canopy oaks are being replaced by shade-tolerant trees that are abundant in the understory of mature stands. Although prescribed fire ...

Sustaining young forest communities: ecology and management of early successional habitats in the Central Hardwood Region, USA

Sustaining young forest communities: ecology and management of early successional habitats in the Central Hardwood Region, USA

Change in oak abundance in the eastern United States from 1980 to 2008

Although oaks ( Quercus spp.) have historically dominated much of the forest land in eastern North America, a great deal of fragmentary and sometimes anecdotal evidence suggests that they have been yielding dominance in recent decades to other, typically more shade-tolerant species. Using FIA data, our work formally quantifies the change in oak abundance in the eastern U.S. during the period of 1980–2008. The results indicate that most areas in the eastern U.S. experienced some decline in oak abundance, but the decrease was not universal either geographically or among species. Declines were especially marked in the Central Hardwood Region, which lost oak abundance on 81% its forested area as measured by importance value (IV). Areas with a high oak abundance were more likely to see a reduction in abundance. Among all 25 species analyzed, eight species decreased significantly in IV while two increased. Both the top two most prevalent white oak species (white oak ( Quercus alba) and post oak ( Quercus stellata)) and red oak species (northern red oak ( Quercus rubra) and black oak ( Quercus velutina)) had significant decreases in density and IV. Water oak ( Quercus nigra) is one of the red oak species that had a near universal increase of its abundance throughout its native range (83% of area). This study provided a comprehensive quantification of the dynamic of oak species in a regional-wide geographic context, which will provoke forest researchers and managers to revisit the oak decline problem by using knowledge from other regions and other species.

Effects of Nitrogen on Temporal and Spatial Patterns of Nitrate in Streams and Soil Solution of a Central Hardwood Forest

This study examined changes in stream and soil water and their relationship to temporal and spatial patterns of in soil solution of watersheds at the Fernow Experimental Forest, West Virginia. Following tenfold increases in stream concentrations over a 13-year period (1969–1981) on untreated WS4, concentrations have declined through 2006. Following fourfold increases in stream on treatment WS3 from pretreatment levels to a 1998 maximum, concentrations have declined through 2006, despite additions of N. Concentrations of soil water were consistently lower for WS4 compared to WS3. Data for soil water on WS3 versus WS4 followed patterns of net mineralization and nitrification for these watersheds. Nitrogen additions to WS3 decreased spatial heterogeneity of N processing, which was largest in the pretreatment year and decreased significantly to a minimum by 2000-2001. Concurrently, soil water increased on WS3 from 1.3 mg -N L−1in pretreatment 1989 to a maximum of 6.4 mg -N L−1in 2001. Spatial heterogeneity in soil water on WS4 remained high during this period. Data suggest that temporal patterns of stream may be influenced by spatial heterogeneity of watershed processes which vary over time in response to N availability.

Coupling of vegetation layers and environmental influences in a mature, second-growth Central Hardwood forest landscape

Forest communities across the landscape of the Central Hardwood Forest Region are experiencing a transition from dominance by oak (Quercus) and hickory (Carya) to maple (Acer) driven largely by a prolonged period of fire suppression. In many cases, this shift in community composition, structure, and function is considered undesirable as oak–hickory forests are valued for timber, wildlife habitat, and natural heritage. Considerable management and restoration efforts target the restoration of oak–hickory forest communities, yet treatments have yielded varying degrees of success. In some cases, difficulties in meeting targets may be due to ecological thresholds created by complex vegetation–environment interactions that maintain the maple-dominated community state. We examined direct and indirect interactions among vegetation layers and environmental gradients for the mature, second-growth forest communities of the Ironton Unit of the Wayne National Forest (WNF) in southeastern Ohio. Using a stratified random approach, we identified 72 study communities with trees at least 70 years old and without evidence of recent disturbance. Within these communities, we sampled all overstory vegetation on two–four 500m2 plots and recorded saplings and ground-flora species in nested sub-plots. At each plot, we also collected soil samples for physical and chemical analyses and recorded physiographic variables. Our first objective was to describe the Ironton forest landscape, where communities were likely transitioning from oak to maple. To identify such patterns, we used ordination analyses that relate species occurrence to implied environmental gradients. Our second objective was to use the relationships to develop a structural equation model (SEM) to quantify the strength of pathways among the canopy, sapling, and ground-flora vegetation layers and environmental factors (e.g., soil chemistry and physiographic position). Our results indicate that the forest landscape of the Ironton Unit of the WNF is at a transition point with communities dominated by either oak or maple, and a sapling layer dominated by maple. Maple may be most likely to replace oak and hickory in the canopies of communities at mid- and lower-slope positions with intermediate soil moisture. This transition will likely have cascading effects throughout the sapling and ground-flora layers, which SEM demonstrates are directly influenced by the canopy. We believe the simultaneous consideration of direct and indirect interactions shaping vegetation structure and composition using techniques such as SEM will advance understanding of the current transition from an oak–hickory to a maple-dominated forest landscape. This information will contribute to the continued improvement of appropriate forest management and ecosystem restoration techniques for the Central Hardwood Forest Region, including those designed to shift the dominance of forest communities from maple to oak.

Relationship between treefall direction, slope-aspect, and wind in eight old-growth oak stands in the Central Hardwood Forest, USA

This study examined the relationship between direction of treefall, slope-aspect and prevailing wind in five old-growth stands where single-tree canopy gaps characterize the dominant disturbance regime. All live and downed trees were inventoried in 0.45-ha sample plots, and crown sizes of live trees were measured along two perpendicular axes. Directions of fall and slope-aspect of downed trees also were recorded. Regional prevailing winds and wind gusts were obtained from four nearby airports. I used circular statistics to determine if directions of treefall for each study stand had a mean direction or if the directions of fall were uniformly distributed. If directions of treefall had a true mean, they were then compared to mean slope aspect and prevailing wind directions. At two of eight plots, treefall directions were uniformly distributed (i.e., no mean direction). Only one plot showed a statistically significant similarity between mean slope-aspect and mean direction of fall, and only three of the eight study plots showed statistically significant similarities between mean treefall and wind directions. Mean crown asymmetry (ratio of long and short diameters) was 1.26, and there were no significant differences in asymmetry values when current gap border trees and non border trees were compared. While trees may fall downhill and downwind, the high variation in treefall and wind directions precluded establishing a consistent statistical relationship between these data sets. I suggest that crown asymmetry, resulting from differential crown growth of trees on sloped-hillsides and within canopy gaps, exerts a strong additional influence on direction of fall.

A Decrease in Oak Litter Mass Changes Nutrient Dynamics in the Litter Layer of a Central Hardwood Forest

Abstract The abundance of oak is declining in the central hardwood forest, resulting in structural and functional changes in the litter layer. We hypothesized that a decline in oak litter mass associated with a lower oak component will result in an increase in nutrient cycling rates in the litterlayer. To test this hypothesis, we compared mass loss and C, N, P, and Ca dynamics in pure oak litter and in litter made of 48% oak plus 52% five other deciduous species in a central hardwood forest in West Virginia. In 12 months of litter decomposition, pure oak litter decomposed more slowly,retained more C and N, immobilized more and subsequently did not release P, and released less Ca than litter consisting of 48% oak plus five other species. Annual stand-level nutrient fluxes in pure oak and in 48% oak plus five other species litter were correspondingly +4.1 and −4.4kg ha−1 N, +0.22 and −0.17 kg ha−1 P, and −9.3 and −16.7 kg ha−1 Ca. These results indicate that a decline in oak will cause more rapid nutrient cycling in the litter layer of affected central hardwood stands.

Fire History of a Rimrock Pine Forest at New River Gorge National River, West Virginia

The fire history of a rimrock pine forest at the New River Gorge National River, West Virginia, was studied using 21 fire-scarred Pinus virginiana Mill. (Virginia pine) cross-sections. Fire frequency and the goodness-of-fit between the fire interval distribution and the normal and Weibull distributions were evaluated with the FHX2® program. A 107-year fire chronology (1898–2005) was constructed from 53 fire scars. Fire intervals ranged from 1 to 8 years. The Weibull median interval was approximately 3 years using liberal (one or more trees scarred during a single year) or conservative (two or more trees scarred during a single year) criteria. Similar to other mixed forest stands in the Central Hardwood Region, fires in the 20th century were likely ignited from coal mining activities and steam-driven locomotives near the study site. Anthropogenic fires may have caused an artificial increase in rimrock pine forests or allowed pines to persist in greater numbers than would be possible in the absence of disturbance. Restoration (e.g., prescribed burning) is probably not needed to retain P. virginiana as a component of the rimrock forest, but the species' dominance will continue to be restricted on the rim of the gorge.

Influence ofMicrostegium vimineumPresence on Insect Abundance in Hardwood Forests

Microstegium vimineum (Japanese Stiltgrass) is an exotic, annual grass that has invaded hardwood forests throughout the Southeastern United States. Four forests, in four Tennessee counties, were selected, and insects and plant communities were sampled along transects with and without M. vimineum. Insects were sampled using a terrestrial vacuum sampler. Percent plant cover was measured using a point-intercept technique, and plant species richness and diversity were calculated. Of the 60 families collected, significantly more individuals in the families Acrididae, Cicadellidae, and Gryllidae, were collected in areas with M. vimineum, whereas areas without M. vimineum resulted in significantly more individuals in the families Blattellidae and Chrysomelidae. Herbaceous plant richness and diversity did not significantly differ between areas with and without M. vimineum. Areas without M. vimineum had significantly lower percent vegetation cover (30.41%) than areas with M. vimineum (91.48%). The overall herbaceous plant community diversity and structure may be more influential factors in the abundances of insect families in central hardwood forests than the invasion of M. vimineum.

Competitive interaction between Microstegium vimineum and first-year seedlings of three central hardwoods1

Abstract We established an experiment designed to compare effects of Microstegium vimineum (Japanese stiltgrass) on seedlings of three native hardwood species to investigate the hypothesis that competitive effects of M. vimineum on juvenile trees will vary across different tree species. Growth and survival of Acer rubrum, Liriodendron tulipifera, and Quercus rubra first-year seedlings were compared in plots with and without M. vimineum in three planting beds under 50 percent shade. The tree species studied are abundant and of particular interest in the Central Hardwood Region. A. rubrum and L. tulipifera seedlings experienced reduced growth in several foliar characteristics in the presence of M. vimineum. Q. rubra did not exhibit any differences in foliar characteristics between plots with and without M. vimineum, however there was a reduction in Q. rubra stem weight as a result of the presence of M. vimineum. The differential responses of A. rubrum, L. tulipifera, and Q. rubra to the presence of M. vimin...

Oak Ecosystem Management Considerations for Central Hardwoods Stands Arising from Silvicultural Clearcutting

Abstract Silvicultural clearcutting was widely used during the late 20th century to regenerate stands on upland sites and achieve timber production objectives within the central hardwood region. As these even-aged stands develop, silvicultural guidelines are needed to address newer management objectives emphasizing oak ecosystem maintenance. The US Forest Service Common Stand Exam procedure (Common Stand Exam Users Guide, 2003, Ver. 1.5.1, US Forest Service, Washington, DC, 87 p.) was modified to assess stand stocking, composition, oak (Quercus) competitive status, and other emerging management concerns. A total of 74 randomly selected upland stands that had been silviculturally clearcut between 1980 and 1990 were sampled across the Shawnee National Forest in southern Illinois. Maples (Acer spp.) and yellow-poplar (Liriodendron tulipifera L.) predominated across all landscape positions 15–26 years after stand initiation. Oak (Quercus spp.) trees per acre was related to landscape position and averaged less than 50 trees/ac on the more productive lower slope positions and north aspects. However, when yellow-poplar was present, oaks were in a competitively inferior canopy position regardless of slope position or aspect. Our results show that for sustaining oak ecosystems in this region, management interventions favoring oaks should focus on the most productive sites, where crop tree release would reduce yellow-poplar interference with a sparse oak resource, as well as on less productive sites, where thinning to reduce stocking may be needed to maintain stand health.

Effects of Microsites Created by Selective Harvesting on Growth of Microstegium vimineum in a Central Hardwood Forest

Abstract Disturbances related to silvicultural activities are inevitable and may facilitate the spread of established populations of exotic species. Microstegium vimineum is an annual exotic grass that has spread throughout the eastern United States. Different categories of understory microsites resulting from cutting and the operation of logging machines within three selective harvest units were identified and characterized by measuring several environmental variables. M. vimineum was sown within the microsites categorized. Differences in growth of M. vimineum across different microsites were quantified. As percent canopy cover increased, M. vimineum percent cover, mean length, and mean number of nodes decreased. Also, as litter depth increased, M. vimineum percent cover and stem length decreased. In undisturbed microsites in which M. vimineum was not sown, the exotic grass was not a dominant species, whereas in all other microsites created by logging machine operation M. vimineum was a dominant species whether those areas were sown or colonized by wild populations. These results suggest that unique microsites created by logging may facilitate M. vimineum invasion of central hardwood forests. The apparent connection between soil and canopy disturbance and invasion by M. vimineum provides further impetus for careful planning and use of haul roads and skid trails.

A 20-year Landsat water clarity census of Minnesota's 10,000 lakes

A 20-year comprehensive water clarity database assembled from Landsat imagery, primarily Thematic Mapper and Enhanced Thematic Mapper Plus, for Minnesota lakes larger than 8 ha in surface area contains data on more than 10,500 lakes at five-year intervals over the period 1985–2005. The reliability of the data was evaluated by examining the precision of repeated measurements on individual lakes within short time periods using data from adjacent overlapping Landsat paths and by comparing water clarity computed from Landsat data to field-collected Secchi depth data. The agreement between satellite data and field measurements of Secchi depth within Landsat paths was strong (average R 2 of 0.83 and range 0.71–0.96). Relationships between late-summer Landsat and field-measured Secchi depth for the combined statewide data similarly were strong ( r 2 of 0.77–0.80 for individual time periods and r 2 = 0.78 for the entire database). Lake clarity has strong geographic patterns in Minnesota; lakes in the south and southwest have low clarity, and lakes in the north and northeast tend to have the highest clarity. This pattern is evident at both the individual lake and the ecoregion level. Mean water clarity in the Northern Lakes and Forest and North Central Hardwood Forest ecoregions in central and northern Minnesota remained stable from 1985 to 2005 while decreasing water clarity trends were detected in the Western Corn Belt Plains and Northern Glaciated Plains ecoregions in southern Minnesota, where agriculture is the predominant land use. Mean water clarity at the statewide level also remained stable with an average around 2.25 m from 1985 to 2005. This assessment demonstrates that satellite imagery can provide an accurate method for obtaining comprehensive spatial and temporal coverage of key water quality characteristics that can be used to detect trends at different geographic scales.