Overstory Thinning Research Articles

Effects of different intensities of overstory thinning on tree growth and understory plant-species productivity in a semi-arid Pinus halepensis Mill. afforestation

It is becoming more and more common in the Mediterranean basin to guard against forest fires by creating wooded firebreak areas by reducing the overstory density, pruning the remaining trees and slash mulching. Nevertheless, very few attempts have been made to analyse the effect of this practice upon tree growth and the productivity of the understory plant species in semi-arid areas by following a well defined experimental design over any length of time. To remedy this lack of information, during the spring of 2005 we thinned the overstory in a semi-arid Aleppo pine (Pinus halepensis Mill.) afforestation in SE Spain (planted in the winter of 1993-1994) from an initial density of about 1,500 trees per ha according to three different thinning regimes. The annual growth data of each stand (diameter at breast height, canopy cover and basal area) were measured in randomly situated plots of 20 × 20 m and the above-ground biomass of understory plant species was also harvested from quadrats of 0.5 × 0.5 m during the early summers of 2005 to 2009. Our results showed a positive and significant response from trees in thinned stands compared to the controls, in spite of periods of low-rainfall and plague stress that unfortunately occurred during the study period. There were also statistical differences in understory biomass production within the different areas of overstory thinning as a response to the new conditions. Nevertheless, this biomass was only a small fraction of the total above-ground biomass of the afforestation, which was much higher in control plots. These tree responses and structural changes to the afforestation could be of great interest because of their implications for forest management in the context of global change in an area where increases in temperature and reductions and irregularity in precipitation, together with higher fire risks, are forecast.

Land-use history, historical connectivity, and land management interact to determine longleaf pine woodland understory richness and composition

Restoration and management activities targeted at recovering biodiversity can lead to unexpected results. In part, this is due to a lack of understanding of how site-level characteristics, landscape factors, and land-use history interact with restoration and management practices to determine patterns of diversity. For plants, such factors may be particularly important since plant populations often exhibit lagged responses to habitat loss and degradation. Here, we assess the importance of site-level, landscape, and historical effects for understory plant species richness and composition across a set of 40 longleaf pine Pinus palustris woodlands undergoing restoration for the federally endangered red-cockaded woodpecker in the southeastern United States. Land-use history had an overarching effect on richness and composition. Relative to historically forested sites, sites with agricultural histories (i.e. former pastures or cultivated fields) supported lower species richness and an altered species composition due to fewer upland longleaf pine woodland community members. Landscape effects did not influence the total number of species in either historically forested or post-agricultural sites; however, understory species composition was affected by historical connectivity, but only for post-agricultural sites. The influences of management and restoration activities were only apparent once land-use history was accounted for. Prescribed burning and mechanical overstory thinning were key drivers of understory composition and promoted understory richness in post-agricultural sites. In historically forested sites these activities had no impact on richness and only prescribed fire influenced composition. Our findings reveal complex interplays between site-level, landscape, and historical effects, suggest fundamentally different controls over plant communities in longleaf pine woodlands with varying land-use history, and underscore the importance of considering land-use history and landscape effects during restoration.

Can Restoration Management Improve Habitat for Insect Pollinators in Ponderosa Pine Forests of the American Southwest?

Abstract In addition to their critical role in food crop production, pollinators keep natural plant communities healthy by assisting with plant reproduction. Currently, forest conditions in ponderosa pine (Pinus ponderosa) forests of the Intermountain West appear to be unfavorable for most insect pollinators. In an effort to reduce fire hazards and regain forest health in these forested landscapes, overstory thinning and prescribed burning are increasingly being applied. These treatments also have the potential to improve habitat for pollinating taxa. In this article, I focus on the potential effects of forest thinning, prescribed burning, and the accompanying incidental introduction of non-native species, as well as the potential impacts of herbivory by wild and domestic ungulates, on plant-pollinator interactions at sites undergoing restoration treatments. Lastly, I make management recommendations regarding how to mindfully conduct forest restoration for the benefit of insect pollinator assemblages despite the current lack of data.

Habitat Quality Following Mid‐Rotation Treatment in Conservation Reserve Program Pines

ABSTRACT Evaluation of habitat management practices at mid‐rotation is needed for pine (Pinus spp.) plantations enrolled in cost‐share programs. Plantations established in abandoned agricultural fields may have different understory plant communities than those with a long history of forest cover. Mid‐rotation pine plantations often have a hardwood midstory that limits development of early succession habitat components important to white‐tailed deer (Odocoileus virginianus; deer) and northern bobwhite (Colinus virginianus; bobwhite). We treated with imazapyr herbicide and prescribed burning (HB) 11 thinned, 13–22‐year‐old pine plantations in the Upper East Gulf Coastal Plain of Mississippi, USA, enrolled in cost‐share programs, and we sampled plant community response during the summers of 2003 and 2004, years 1 and 2 posttreatment. The HB treatment created a more open structure with greater coverage of debris and herbaceous plants than in controls. Increased forb coverage in HB plots yielded a more seasonally diverse foraging base for deer. Horizontal screening cover developed slowly in HB plots and was more abundant in control plots. Autumn and winter food‐plant coverage for bobwhite was provided by either treatment, but accessibility was improved in HB plots relative to controls. Bobwhite nesting cover was improved by HB relative to controls but was still of marginal quality. Brood‐rearing habitat was precluded in both treatments due to lack of bare ground. Our results indicate that imazapyr followed by prescribed fire is a beneficial tool for creating early succession habitat for deer and bobwhite in mid‐rotation pine plantations with a history of agricultural use. Continued management with periodic prescribed fire and overstory thinning should be instituted to maintain and perhaps improve these conditions.

Fire suppression and fuels treatment effects on mixed‐conifer carbon stocks and emissions

Depending on management, forests can be an important sink or source of carbon that if released as CO2 could contribute to global warming. Many forests in the western United States are being treated to reduce fuels, yet the effects of these treatments on forest carbon are not well understood. We compared the immediate effects of fuels treatments on carbon stocks and releases in replicated plots before and after treatment, and against a reconstruction of active-fire stand conditions for the same forest in 1865. Total live-tree carbon was substantially lower in modern fire-suppressed conditions (and all of the treatments) than the same forest under an active-fire regime. Although fire suppression has increased stem density, current forests have fewer very large trees, reducing total live-tree carbon stocks and shifting a higher proportion of those stocks into small-diameter, fire-sensitive trees. Prescribed burning released 14.8 Mg C/ha, with pre-burn thinning increasing the average release by 70% and contributing 21.9-37.5 Mg C/ha in milling waste. Fire suppression may have incurred a double carbon penalty by reducing stocks and contributing to emissions with fuels-treatment activities or inevitable wildfire combustion. All treatments reduced fuels and increased fire resistance, but most of the gains were achieved with understory thinning, with only modest increases in the much heavier overstory thinning. We suggest modifying current treatments to focus on reducing surface fuels, actively thinning the majority of small trees, and removing only fire-sensitive species in the merchantable, intermediate size class. These changes would retain most of the current carbon-pool levels, reduce prescribed burn and potential future wildfire emissions, and favor stand development of large, fire-resistant trees that can better stabilize carbon stocks.

Prescribed burning and mechanical thinning effects on belowground conditions and soil respiration in a mixed-conifer forest, California

Soil respiration ( R S) is a major carbon pathway from terrestrial ecosystems to the atmosphere and is sensitive to environmental changes. Although commonly used mechanical thinning and prescribed burning can significantly alter the soil environment, the effect of these practices on R S and on the interactions between R S and belowground characteristics in managed forests is not sufficiently understood. We: (1) examined the effects of burning and thinning treatments on soil conditions, (2) identified any changes in the effects of soil chemical and physical properties on R S under burning and thinning treatments, and (3) indirectly estimated the changes in the autotrophic soil respiration ( R A) and heterotrophic soil respiration ( R H) contribution to R S under burning and thinning treatments. We conducted our study in the Teakettle Experimental Forest where a full factorial design was implemented with three levels of thinning, none (N), understory thinning (U), and overstory thinning (O; September to October 2000 for thin burn combination and June and July 2001 for thin only treatments) and two levels of burning, none (U) and prescribed burning (B; fall of 2001). R S, soil temperature, soil moisture, litter depth, soil total nitrogen and carbon content, soil pH, root biomass, and root nitrogen (N) concentration were measured between June 15 and July 15, 2002 at each plot. During this period, soil respiration was measured three times at each point and averaged by point. When we assumed the uniform and even contribution of R A and R H to R S in the studied ecosystem without disturbances and a linear relationship of root N content and R A, we calculated the contributions of R A to R S as 22, 45, 53, 48, and 45% in UU, UO, BN, BU, and BO, respectively. The results suggested that after thinning, R S was controlled more by R H while after burning R S was more influenced by R A. The least amount of R S variation was explained by studied factors under the most severe treatment (BO treatment). Overall, root biomass, root N concentration, and root N content were significantly ( p < 0.01) correlated with soil respiration with correlation coefficients of 0.37, −0.28, and 0.29, respectively. This study contributes to our understanding of how common forestry management practices might affect soil carbon sequestration, as soil respiration is a major component of ecosystem respiration.

Canopy microclimate response to pattern and density of thinning in a Sierra Nevada forest

Restoring Sierra Nevada mixed-conifer forests after a century of fire suppression has become an important management priority as fuel reduction thinning has been mandated by the Healthy Forests Restoration Act. However, in mechanically thinned stands there is little information on the effects of different patterns and densities of live-tree retention on forest canopy microclimate. This study compared gradients of air temperature and vapor pressure deficit (VPD) through the vertical forest profile among an overstory-thin, an understory-thin, an un-thinned control, and a riparian environment in a Sierra Nevada mixed-conifer forest. Temperature and humidity were recorded for a year by 60 data loggers arrayed in 12 trees at 5, 15, 25, 35, and 45 m above the forest floor. Both thinning treatments had significantly more extreme summer daily ranges of temperature and VPD than the control across heights. The overstory-thin resulted in the greatest maximum temperatures, VPDs, and VPD range among all sensors at 5 m, and significantly higher summer maximum temperatures and VPDs than the control in lower strata (≤15 m). The understory-thin also had significantly higher summer maximum temperatures than the control (≤15 m), but these too were significantly less than in the overstory-thin nearest the surface at 5 m. Understory thinning did not alter the mean or range of microclimate as much as overstory thinning. Riparian microclimate had significantly lower minimums and means, and greater daily ranges of temperatures and VPDs than the control. Results suggest that thinning canopy cover significantly increases the extremes and variability of understory microclimate compared to thinning from below and no-thin treatments.

Carbon dynamics of a ponderosa pine plantation following a thinning treatment in the northern Sierra Nevada

We investigated the impacts of a thinning prescription commonly used to reduce fuel loads in mature ponderosa pine forests of the northern Sierra Nevada Mountains on the distribution of carbon among functionally distinct pools, and on the component fluxes of net ecosystem production (NEP). The biomass of wood, foliage, and roots was highest in the unthinned control stands, lowest in stands measured 3 years after thinning, and intermediate in the stands measured 16 years following the same prescription. While total wood net primary production (NPP) followed the same pattern as biomass across treatments, an apparent doubling of shrub foliage NPP in the 3 years following overstory thinning reduced the impacts of thinning on total foliage NPP. Similarly, reductions in coarse root NPP associated with tree removal were largely offset by increases in fine root production. Compensatory NPP by shrubs and fine roots increased the light use efficiency of thinned stands 60% over that of unthinned plots. Both soil respiration and the decomposition of aboveground dead wood appeared conserved across all treatments. Results suggest that when modeling the influence fuel reduction treatments on regional carbon dynamics, it may be necessary to consider the compensatory responses of understory vegetation as such shifts in growth form can effect meaningful changes in the capture and allocation of carbon in the ecosystem.

Initial tree regeneration responses to fire and thinning treatments in a Sierra Nevada mixed-conifer forest, USA

Fire is a driver of ecosystem patterns and processes in forests globally, but natural fire regimes have often been altered by decades of active fire management. Following almost a century of fire suppression, many western U.S. forests have greater fuel levels, higher tree densities, and are now dominated by fire-sensitive, shade-tolerant species. These fuel-loaded conditions can often result in high-intensity crown fires replacing historic low- to moderate-intensity fire regimes. In the mixed-conifer forests of the California Sierra Nevada, thinning and prescribed fire are widely used to reduce fuels and shift future stand composition from shade-tolerant species to more fire-resistant pines ( Pinus lambertiana and Pinus jeffreyi) that were historically more abundant. The impacts of these treatments, however, on forest regeneration composition and abundance are unclear. We examined the effects of prescribed fire and common thinning treatments (understory and overstory thinning) on microsite conditions, seed rain, and tree regeneration in an old-growth, mixed-conifer forest in the Sierra Nevada, California, USA. Treatments significantly altered environmental conditions, but there was substantial variation and overlap in conditions among treatments. Seed rain of shade-tolerant Abies concolor and Calocedrus decurrens was 5–26 times greater than P. jeffreyi and P. lambertiana, creating inertia in efforts to shift stands towards increased pine abundance. Survival of Pinus germinants was greatest in burned microsites. The burn-overstory thin treatment had both the highest mortality of advanced A. concolor and C. decurrens regeneration and the greatest increase in pine regeneration. Species occupied microsites gradating from low light/high moisture to high light/low moisture in the order: C. decurrens, A. concolor, P. lambertiana, and P. jeffreyi. Results suggest prescriptions may need to thin mature A. concolor and C. decurrens to significantly reduce their seed rain, create an abundance of burned open microsites, or plant Pinus seedlings to shift regeneration composition in treated stands.

Shifts in morphological traits, seed production, and early establishment ofDesmodium nudiflorumfollowing prescribed fire, alone or in combination with forest canopy thinning

Reintroduction of periodic dormant-season fire and overstory thinning are currently being employed for forest ecosystem management in deciduous forests of eastern North America. These manipulations usually alter the flux of light and the availability of soil nutrients to the perennial herbaceous plants that dominate the understory. We utilized Bayesian statistical methods to examine the effects of prescribed burning (B) and the combination of burning and overstory thinning (T+B) on the morphology, seed production, and early establishment of Desmodium nudiflorum (L.) DC. (Fabaceae) in mixed-oak ( Quercus spp.) forests in southern Ohio. During the fourth growing season after the first fire, plants from thinned and burned (T+B) plots were 62% larger than plants from control plots (C). Both burning alone (B) and T+B treatments decreased specific leaf area (SLA). T+B also resulted in significantly decreased root mass ratio (RMR), and increased leaf mass ratio (LMR), and specific root length (SRL). During the first growing season after a second fire, both B and T+B resulted in significantly increased plant biomass, LMR, individual seed mass, and total seed production, as well as decreased SLA and plant height; in contrast, neither B nor T+B had significant impacts on leaf area ratio or seedling establishment. Prescribed fire, especially when combined with thinning, can result in increases in total biomass, seed size, and seed production, and hence enhance the fitness of this perennial herb in these mixed-oak forests.

Ecophysiological responses of two herbaceous species to prescribed burning, alone or in combination with overstory thinning

The oak-rich deciduous forests of the central Appalachian Mountains of eastern North America have changed significantly since the onset of effective fire suppression early in the 20th century. Those changes have resulted in progressively decreasing light and nutrient supplies to herbaceous perennial understory species. Application of ecological restoration treatments such as reintroduction of frequent dormant-season fire and overstory thinning to pre-suppression density often increase light, soil temperature and moisture, and short-term nutrient availability to pre-suppression levels. To persist in this environment, perennial understory herbs must be able to acclimate phenotypically to the very different resource supply combinations present with and without fire suppression. As part of a larger study of the response of the long-lived herbaceous perennials Desmodium nudiflorum and Panicum boscii to ecosystem restoration treatments in Ohio mixed-oak forests, this study examined the ecophysiological effects of prescribed burning (B) and the combination of burning and thinning (T + B) in mixed-oak forests in southern Ohio. Control (C) plants had significantly lower maximum photosynthetic rate (A(max)) than those in the treated plots. The enhancement of A(max) averaged 26.7% and 52.7% in the B and T + B treatments, respectively. Plants from the T + B plots had higher quantum yield, stomatal conductance, and photosynthetic nutrient use efficiency than B and C plants. B plants had greater intrinsic water use efficiency (WUE) than plants in the C or T + B treatments. Light saturation point (LSP), light compensation point (LCP), and "dark" respiration (DR) did not differ among treatments. Photosynthetic parameters did vary significantly between the species, but no significant treatment × species interactions were detected. Our results support the hypothesis that prescribed burning, especially when combined with overstory thinning, in these perennial herbs can result in phenotypic acclimation characterized by enhanced photosynthetic performance.

Effects of fire alone or combined with thinning on tissue nutrient concentrations and nutrient resorption in Desmodium nudiflorum

This study examined tissue nutrient responses of Desmodium nudiflorum to changes in soil total inorganic nitrogen (TIN) and available phosphorus (P) that occurred as the result of the application of alternative forest management strategies, namely (1) prescribed low-intensity fire (B), (2) overstory thinning followed by prescribed fire (T + B), and (3) untreated control C), in two Quercus-dominated forests in the State of Ohio, USA. In the fourth growing season after a first fire, TIN was significantly greater in the control plots (9.8 mg/kg) than in the B (5.5 mg/kg) and T + B (6.4 mg/kg) plots. Similarly, available P was greater in the control sites (101 microg/g) than in the B (45 microg/kg) and T + B (65 microg/kg) sites. Leaf phosphorus ([P]) was higher in the plants from control site (1.86 mg/g) than in either the B (1.77 mg/g) or T + B plants (1.73 mg/g). Leaf nitrogen ([N]) and root [N] showed significant site-treatment interactive effects, while stem [N], stem [P], and root [P] did not differ significantly among treatments. During the first growing season after a second fire, leaf [N], stem [N], litter [P] and available soil [P] were consistently lower in plots of the manipulated treatments than in the unmanaged control plot, whereas the B and T + B plots did not differ significantly from each other. N resorption efficiency was positively correlated with the initial foliar [N] in the manipulated (B and T + B) sites, but there was no such relation in the unmanaged control plots. P resorption efficiency was positively correlated with the initial leaf [P] in both the control and manipulated plots. Leaf nutrient status was strongly influenced by soil nutrient availability shortly after fire, but became more influenced by topographic position in the fourth year after fire. Nutrient resorption efficiency was independent of soil nutrient availability. These findings enrich our understanding of the effects of ecosystem restoration treatments on soil nutrient availability, plant nutrient relations, and plant-soil interactions at different temporal scales.

Fire and fire surrogate treatment effects on leaf litter arthropods in a western Sierra Nevada mixed-conifer forest

Frequent, low-intensity fires were a common feature of Sierran forest ecosystems, but suppression policies over the past century have left many forests at risk for catastrophic wildfires. Recent policies highlight the use of prescribed burning or harvesting as fire risk reduction tools, but few studies have investigated the impacts of these management practices on the leaf litter fauna of Sierran forests. This study examines how three fire and “fire surrogate” treatments, prescribed burning, overstory thinning with understory mastication, and combined thinning and burning, impact diversity and abundance of Coleoptera and other leaf litter arthropods. Pitfall trapping was used to collect litter arthropods before and immediately after treatments in replicated forest compartments. The diverse Coleoptera assemblage was dominated by only a few common species, with many rare species represented by only one or two individuals. Rank–abundance diagrams indicated that much of the change in the beetle assemblage due to the treatments was a result of changes in the numbers of rare species. Indicator species analysis showed several species closely allied with the treated compartments, but few with the untreated controls. Both NMS and CCA ordination show considerable change in overall assemblage structure on compartments treated with fire, but less change in the thinned compartments. Coleoptera species richness was slightly higher in burned compartments. Some common beetle species, families of beetles, and other common groups such as ants and spiders showed changes in abundance due to the treatments, but the changes were taxon-specific and showed no general pattern. Overall impacts of the treatments appear to be moderate, and the increased habitat heterogeneity at the compartment level may provide additional habitat for many rare species to coexist. We conclude that the use of fire and fire surrogate treatments in Sierran mixed-conifer forests is justified from the standpoint of their effects on leaf litter arthropods, but the history of management at the site and the scale of treatments must be carefully considered.

Responses of Fendler ceanothus to overstory thinning, prescribed fire, and drought in an Arizona ponderosa pine forest

Overstory tree thinning and prescribed fire are used to restore ecosystem structure and function in ponderosa pine ( Pinus ponderosa Laws.) forests of the southwest but little research has examined constraints on population-level responses of understory plants. In order to study growth and reproduction of a common shrub species after forest restoration treatments, we monitored Fendler ceanothus ( Ceanothus fendleri Gray) plants from 1999 to 2002 in thinned and unthinned overstory units. To study effects of tree thinning, we analyzed relationships of overstory stand density (Reineke’s SDI) and current-year branch length, number of branches, and biomass, and also evaluated the importance of mule deer ( Odocoileus hemionus) and Rocky Mountain elk ( Cervus elaphus) herbivory (Browsing) as a predictor in linear models. To study effects of prescribed fire, we examined mortality, seedling emergence, and growth response on experimentally burned and unburned plots. SDI and browsing were significantly and negatively correlated with F. ceanothus current-year branch length, biomass, and leaf area but relationships were generally weak. Across the 4 years, browsing appeared to be consistently more important than SDI in explaining variation in growth. Although SDI and browsing were significant predictors of growth in years with near normal precipitation, models failed in drought years. Burning resulted in 17–32% mortality whereas 0–5% of plants died on unburned plots. Mortality of burned plants was positively related to amount of forest floor consumed during prescribed fires. One growing season after fire, surviving burned plants responded by producing long resprouts. Current-year branches were consistently longer on burned than unburned plants only where plots were protected from large herbivores. Unburned plants had more current-year branches and greater biomass than burned plants. No seedlings emerged on unburned plots but were found on 44% of burned plots. A quadratic function represented the relationship between seedling emergence and forest floor consumption. Our results suggest that restoration treatments in ponderosa pine forests of northern Arizona can help increase abundance of F. ceanothus but population responses may be slow, particularly when constrained by ungulate herbivory, fire-related mortality of plants and dormant seeds, and drought.

Aristida beyrichiana (Wiregrass) Establishment and Recruitment: Implications for Restoration

AbstractRestoration of the longleaf pine ecosystems of the southeastern United States has focused interest on the regeneration and establishment of Aristida sp. (wiregrass) as a means to reestablish ecological function and structure of the ecosystem. This study examined dispersal distance from planted adults and canopy cover and density effects on establishment and reproduction. In 1994 wiregrass plugs were planted in two densities (500 seedlings/100 m2 and 49 seedlings/100 m2) and three canopy‐thinning treatments (25 m2 basal area/ha, 16 m2 basal area/ha, and 8 m2 basal area/ha) were implemented in a 20‐year‐old longleaf plantation in southwestern Georgia. Due to the intense site preparation and the density of pines planted, virtually no understory vegetation was present. The site was burned in June 1995, which promoted seed production of the planted wiregrass. Results indicate that the 8 m2 basal area/ha treatment results in larger plants that in turn produce a greater number of seedling recruits. No seedling recruitment occurred in control plots. Dispersal distances of up to 594 cm were recorded. Natural seedling recruitment occurred at low‐density transplanting (5 plants/10 m2), denoting that high‐density planting similar to natural density (5 plants/m2) is not required for successful establishment or reproduction. However, overstory thinning in dense pine plantations is required for reproduction and increases the survival of individual plants due to changes in the environmental conditions at the forest floor.

Establishment and Control of Hay-scented Fern: A Native Invasive Species

Hay-scented fern (Dennstaedtia punctilobula (Michx.) Moore) is a native forest understory species that behaves as an invasive plant under certain conditions. Previous work has shown that both increased understory light intensity following overstory thinning and removal of competing plants by herbivores can lead to accelerated growth of hay-scented fern, allowing it to develop dense, nearly monospecific understories that inhibit tree seedling regeneration. To study the relationship between these two factors, we sampled 28 forest stands thinned at different times and subjected to different levels of browsing by white-tailed deer (Odocoileus virginianus), and concluded that more than 15 years of intensive browsing following thinning was necessary for ferns to form closed understory canopies with densities of >90 fronds/m2 and canopy heights of 60–80 cm; thinning alone or intensive browsing alone was not sufficient to cause this level of fern invasion. We applied three treatments to dense fern understories to determine the relative importance of the fern canopy and the dense mat of roots, rhizomes, and dead fronds in the inhibition of tree seedling establishment. Results after two years were: (1) complete removal of the organic mat produced a large germination response of woody and herbaceous species; (2) mixing the organic mat into the mineral soil produced an initial germination response but poor seedling survivorship, as the fern canopy regrew to near pretreatment density; (3) repeatedly clipping the ferns for two years without disturbing the organic mat resulted in a lower germination response than the removal treatment, but rapid growth of seedlings.

Wildlife Responses to Thinning Red Pine

Abstract Red pine is the most intensively managed conifer type in the Lake States, but its typical stand structure of a closed canopy with little understory results in poor wildlife habitat. We evaluated the effects of thinning mature red pine stands on wildlife habitat attributes and use. Red pine stands were thinned to a residual basal area of 16.1 m²/ha and 25.3 m²/ha and compared with controls (&gt;32.1 m²/ha) in terms of understory development, small mammal use, and ungulate use. Overstory thinning resulted in increased woody shrub densities and understory productivity. Small mammal populations tended to increase with overstory thinning, but the results were inconclusive. Elk and deer use increased with overstory removal. Increased ungulate use was likely attributable to increased forage quantity and quality and increased hiding/security cover attributes of the thinned stands. We conclude that overstory thinning can be an effective means of enhancing wildlife habitat and increasing wildlife use of red pine. North. J. Appl. For. 14(3):141-146.

Development of water oak stump sprouts under a partial overstory

A 28-year-old water oak (Quercus nigra L.) plantation was thinned from below to either 254 or 462 stems per hectare to determine the influence of a partial canopy on oak stump sprout development. Sprout clump survival, number of living sprouts in a clump, and height and DBH of the dominant sprout in a clump were measured in years 1–5 and 7 after harvest. By year 7, sprout clump survival under the heavily thinned canopy was 23% higher than under the lightly thinned canopy. Within-clump sprout mortality was not influenced by overstory thinning level, but by year 2 height and diameter increment were 15% and 22% greater, respectively, under the heavy overstory removal. Positive height and diameter growth of dominant sprouts continued under both canopy conditions through year 7, but early benefits of the heavy overstory removal on sprout growth diminished. Additional overstory removal or sprout clump thinning would be necessary to sustain sprout clump survival and sprout growth over extended periods.