Full Stocking Research Articles

Sapling Stocking Targets for Multiple Management Goals in Northern Hardwood Forests: How Do Stands Measure Up?

Abstract Well-stocked natural tree regeneration is critical to sustainable management of northern hardwood forests (NHF) by selection silviculture, but explicit goals and stocking criteria for sapling recruit size classes are lacking. For stems 0–2 in. (0–5.1 cm), we define 171 and 691 stems ac−1 (422.5 and 1,707.5 ha−1) as lower and upper full stocking thresholds for basic NHF management goals (wood and biomass productivity) and overabundant/pest–pathogen-challenged species. We define component stocking targets as 15% of full stocking targets for six additional wildlife (e.g., nut producers) and resilience (e.g., pest–pathogen) goals and individual species representation. Applying our system to 141 managed stands in Michigan, USA, we found several areas of concern. At low threshold, 33% of stands were understocked for biomass and wood goals, whereas 67% were fully stocked with overabundant/pest–pathogen-challenged species. Among goals, component stocking (low threshold) was as low as 5% (nut producers), with more than half the stands component stocked for ≤ 2 goals and ≤ 2 individual species. Stocking varied geographically and decreased with increasing site quality, overstory basal area, and deer use. Study Implications The stocking goals and density criteria we developed can help managers objectively identify areas where current silvicultural practices are ineffective and need modification. Our system is based on an interactive platform that can be readily modified to accommodate new information and management goals. Several management suggestions emerged from applying our system to selection-managed NHF stands in Michigan. First, highest quality sites have the greatest stocking challenges. Stocking outcomes could likely be improved via more intense overstory harvests and mitigation of deer impacts. Second, most stands meeting stocking goals are vulnerable to future changes in climate and pest–pathogen outbreaks, given stocking is often dominated by a small subset of candidate species. Planting, including the incorporation of assisted migration species candidates could help ameliorate this problem, as species could be evaluated based on their contribution to multiple component stocking goals.

Stocking Diagrams for Silvicultural Guideline in Korean Pines and Japanese Larch

Appropriate management of stand density is necessary to avoid wasted growing space and overcrowding-induced self-thinning and therefore to optimize profitability. We developed a Gingrich-style stocking chart for Korean red pine (Pinus densiflora), Korean white pine (P. koraiensis), and Japanese larch (Larix kaempferi) in Korea. Datasets for even-aged stands were categorized into two censored datasets via relative density based on species-specific stand density indices to assign adequate plots for tree allometry. Censored plot data for maximum density on full stocking were used to develop A-level stocking based on mean individual tree area. In censored plot data for minimum density on full stocking, individual trees represented open-grown trees, and a crown competition factor of 100 was proposed as B-level stocking. Based on parameters estimated from allometry, stocking diagrams comprising quadratic mean diameter, number of trees, and basal area were correctly expressed. A-level stocking at the same quadratic mean diameter revealed that Korean white pine had the most trees and largest basal area, while Japanese larch had the fewest trees and smallest basal area. In contrast, B-level stocking disclosed that Japanese larch had the most trees and basal area, whereas Korean white pine had the fewest trees and smallest basal area. The stocking diagrams suggest that silvicultural treatments for these species should be species-specific.

Demographic trends in Claremont California’s street tree population

The aim of this study was to quantify street tree population dynamics in the city of Claremont, CA. A repeated measures survey (2000 and 2014) based on a stratified random sampling approach across size classes and for the most abundant 21 species was analyzed to calculate removal, growth, and replacement planting rates. Demographic rates were estimated using a hierarchical Bayesian framework. The community-level (all species) median growth rate was 1.41% per year (95% CI: 1.21–1.65%) with Pinus brutia and Pistacia chinensis growing significantly faster than the community-level median. The community-level median removal rate was 1.03% per year (95% CI: 0.66–1.68%), with no significant differences between species and the community-level medium. Once removed, only 7.2% (95% CI: 4.4–12.9%) were replaced annually. Presence of overhead utility lines influenced tree removal rates while age, diameter-at-breast-height, and prior tree condition influenced tree growth. Overall live aboveground biomass in sampled sites was 713.29 Mg in 2000 and increased to 877.36 Mg by 2014. Biomass gain from growth outweighed loss from removals nearly three-fold; replacement contributed 0.5% of the total biomass gain. We conclude that to increase the resilience of the street tree population will require 1) an increase in percent of full stocking or biomass stock and 2) a shift in the species palette to favor species less vulnerable to pests and expected disturbance from climate change and 3) ongoing monitoring to detect departures from baseline demographic rates.

Structure, function and value of street trees in California, USA

This study compiled recent inventory data from 929,823 street trees in 50 cities to determine trends in tree number and density, identify priority investments and create baseline data against which the efficacy of future practices can be evaluated. The number of street trees increased from 5.9 million in 1988 to 9.1 million in 2014, about one for every four residents. Street tree density declined from 65.6 to 46.6 trees per km, nearly a 30% drop. City streets are at 36.3% of full stocking. State-wide, only London planetree (Platanus×hispanica) comprises over 10% of the total, suggesting good state-wide species diversity. However, at the city scale, 39 communities were overly reliant on a single species. The state’s street trees remove 567,748t CO2 (92,253t se) annually, equivalent to taking 120,000 cars off the road. Their asset value is $2.49 billion ($75.1 million se). The annual value (USD) of all ecosystem services is $1.0 billion ($58.3 million se), or $110.63 per tree ($29.17 per capita). Given an average annual per tree management cost of $19.00, $5.82 in benefit is returned for every $1 spent. Management implications could include establishing an aggressive program to plant the 16 million vacant sites and replace removed trees, while restricting planting of overabundant species. Given the tree population’s youth there is likely need to invest in pruning young trees for structure and form, which can reduce subsequent costs for treating defects in mature trees.

Rangeland Condition Monitoring: A New Approach Using Cross-Fence Comparisons of Remotely Sensed Vegetation.

A need exists in arid rangelands for effective monitoring of the impacts of grazing management on vegetation cover. Monitoring methods which utilize remotely-sensed imagery may have comprehensive spatial and temporal sampling, but do not necessarily control for spatial variation of natural variables, such as landsystem, vegetation type, soil type and rainfall. We use the inverse of the red band from Landsat TM satellite imagery to determine levels of vegetation cover in a 22,672km2 area of arid rangeland in central South Australia. We interpret this wealth of data using a cross-fence comparison methodology, allowing us to rank paddocks (fields) in the study region according to effectiveness of grazing management. The cross-fence comparison methodology generates and solves simultaneous equations of the relationship between each paddock and all other paddocks, derived from pairs of cross-fence sample points. We compare this ranking from two image dates separated by six years, during which management changes are known to have taken place. Changes in paddock rank resulting from the cross-fence comparison method show strong correspondence to those predicted by grazing management in this region, with a significant difference between the two common management types; a change from full stocking rate to light 20% stocking regime (Major Stocking Reduction) and maintenance of full 100% stocking regime (Full Stocking Maintained) (P = 0.00000132). While no paddocks had a known increase in stocking rate during the study period, many had a reduction or complete removal in stock numbers, and many also experienced removals of pest species, such as rabbits, and other ecosystem restoration activities. These paddocks generally showed an improvement in rank compared to paddocks where the stocking regime remained relatively unchanged. For the first time, this method allows us to rank non-adjacent paddocks in a rangeland region relative to each other, while controlling for natural spatio-temporal variables such as rainfall, soil type, and vegetation community distributions, due to the nature of the cross-fence experimental design, and the spatially comprehensive data available in satellite imagery. This method provides a potential tool to aid land managers in decision making processes, particularly with regard to stocking rates.

Long-term soil response to variable-retention harvesting in the EMEND (Ecosystem Management Emulating Natural Disturbance) experiment, northwestern Alberta

Kishchuk, B. E., Quideau, S., Wang, Y. and Prescott, C. 2014. Long-term soil response to variable-retention harvesting in the EMEND (Ecosystem Management Emulating Natural Disturbance) experiment, northwestern Alberta. Can. J. Soil Sci. 94: 263–279. We report on soil responses to variable-retention (VR) harvesting from a large-scale experiment (>1000 ha). Samples were taken prior to treatment, and 1 and 6 yr after treatment under cover types representing the successional trajectory for boreal mixedwood forests in northwestern Alberta, Canada. Variable-retention harvesting at six overstory-retention levels [100 (control), 75, 50, 20, 10, and 0% (clearcut)] were applied to 10-ha experimental units under four cover types: deciduous-dominated (80–95% trembling aspen); deciduous-dominated with coniferous understory (80–95% trembling aspen with white spruce understory at 60–80% of full stocking); mixed coniferous-deciduous (35–65% of each); and coniferous-dominated (80–95% white spruce). Only a few clear differences in soil properties attributable to VR harvesting were evident 6 yr post-harvest: (1) both extractable NH4-N in forest floor and 0–7 cm mineral-soil, and forest floor exchangeable K decreased with increasing canopy removal, and (2) forest floor exchangeable Ca increased with canopy removal. There was a decreasing trend in forest floor and mineral soil C (kg ha−1) in undisturbed stands between 1998 and 2005. Differences in soil properties among cover types included higher pH and N concentration in forest floors, and higher cation exchange capacity and exchangeable Ca and Mg in mineral soils in deciduous-dominated stands. Deciduous-dominated stands appear to have distinct soil properties that change under stand development.

Residual Densities Affect Growth of Overstory Trees and Planted Douglas-Fir, Western Hemlock, and Western Redcedar: Results from the First Decade

In recent years, interest has increased in silvicultural systems and harvest cuts that retain partial overstories, but there are few data available on the growth of the understory trees in such stands. We studied the response of overstory trees and underplanted seedlings, Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), and western redcedar (Thuja plicata), to a range of residual overstory densities. Forty to 70-year-old Douglas-fir stands in western Washington were harvested, leaving retention levels of 0, 8, 16, 24, 32, and 40% of full stocking. The 9-year response of the understory seedlings was species-dependent with Douglas-fir the largest in diameter (mean diameter 6.4 cm and mean height 3.8 m), western hemlock the tallest (mean diameter 5.5 cm and mean height 5.4 m), and redcedar the smallest (mean diameter 1.5 cm and mean height 1.5 m), in part because it was heavily browsed. Douglas-fir and western redcedar showed the greatest growth in the lowest retention levels (0 and 8%), and western hemlock responded best at the middle retention levels (8 and 16%).

Influence of herbaceous and woody competition on white pine regeneration in a uniform shelterwood

We investigated the effects of herbaceous and woody vegetation control on the survival and growth of planted and natural eastern white pine (Pinus strobus L.) seedlings through six growing seasons following a uniform shelterwood regeneration harvest on two independent sites. Subsequent to chain scarification, white pine seedlings were planted at 2-m spacing, augmenting natural regeneration (full stocking and >3000 seedlings per ha). Herbaceous vegetation control involved the suppression of grasses, forbs, ferns, and low shrubs, and was maintained for zero, two, or four growing seasons after planting. Woody control involved the removal of all tall shrubs and deciduous trees, and was conducted at the time of planting, at the end of the second or fifth growing seasons, or not at all. White pine seedling growth responded positively to increased duration of herbaceous vegetation control and negatively to delayed woody control. Maximum growth was not realized unless both types of vegetation were suppressed. During the first six growing seasons, the height growth of planted pine was more than twice that of naturally regenerating pine, regardless of tending regime. The study suggests that successful white pine regeneration may be achieved by thinning from below to allow 50% to 60% of full sunlight in the understory, followed by the proactive, early suppression of woody and herbaceous vegetation to maintain optimum light levels and reduce competition for soil moisture and nutrients.

Modelling the risks of natural stand closure release with ageing in pure beech (Fagus sylvatica) and spruce (Picea abies) stands

In the development of pure beech and pure spruce pristine forests, we assume there should be a continuous transition from full stocking to successive disintegration and, finally, total replacement of the first generational wave at the end of its lifetime, dependent on mortality due to overcrowding as well as ageing, leading newly recruited cohorts to grow up from below. A survey of stem number distribution from permanent plots measured repeatedly in six pristine beech reserves and four spruce reserves, mainly in Slovakia, was considered as well as surveys from yield plots in untouched stands in Switzerland on comparable site conditions. From 64 (54, respectively) surveys in virgin forests, we separated (if necessary) the original regeneration waves from successive waves for calculation of stand density development. Comparison with a previous model for full stand closure according to Reineke’s density rule allowed the risk of stand release to be evaluated and determined. The risk of stand closure release is substantially higher for spruce than for beech because of differences in longevity and in vulnerability to storms. Decay does not seem to be the decisive factor, until advanced ageing is reached. Consequences for the understanding of natural forest dynamics, especially reinitiation through successive waves of regeneration are drawn on the basis of silvicultural expertise from continuous cover systems. The density threshold limit for the accession of a second growth in the upper storey is attained at an age of about 180 years for beech and 140 years for spruce. This corresponds to about 70% or 40% of the life cycle, respectively. Vulnerability to stand release should be considered as a gradual (discrete) rather than a continuous phenomenon that depends on the complex relationship between the collective cohesion within a stand and a propensity for weakening factors. This suggests that the establishment of large disclosure patches could be the driving force in the renewal of these virgin forests.

Bat response to shelterwood harvests and forest structure in oak-hickory forests

Forest management practices, such as shelterwood harvesting, can greatly impact bat habitat relationships. Such practices can alter the amount of structural volume within a forest, which can influence bat foraging patterns. We determined the effects of shelterwood harvests of different retention levels (50% and 70% of full stocking) on bat activity patterns in oak-hickory forests located in southern Ohio. We used the Anabat system to monitor activity during May–September 2006. Our objectives were to quantify the effects of harvesting on structural volume and use the results to explain variations in bat activity. Because harvesting alters vertical structure as well as the total amount of volume within a forest, we also determined the height within the vertical profile where changes in structural volume begin to influence overall and species-specific activity. Overall bat activity did not differ significantly between shelterwood harvest levels, but was significantly different between harvested and control sites, with more passes detected within the harvested sites. Lasiurus borealis (red bat), Eptesicus fuscus (big brown bat), and Lasionycteris noctivagans (silver-haired bat) activity was significantly greater in harvested versus control sites, but did not differ between shelterwood harvest levels. Myotis spp. ( Myotis lucifugus (little brown bat) and Myotis septentrionalis (northern Myotis)) and Perimyotis subflavus (tri-colored bat) activity did not vary between shelterwood harvest levels or between harvested and control sites. The greatest reductions in structural volume occurred in the understory to mid-canopy of the shelterwood harvests. Overall activity was most influenced by the amount of volume within 3–6 m above the forest floor, and declined as volume within that height strata increased. Mean bat passes declined by 50% when volume within 3–6 m exceeded 17 m 3/ha. Estimated use by L. borealis decreased by 50% at volumes exceeding 1750 m 3/ha in the understory to mid-canopy (0–12 m), while E. fuscus and L. noctivagans estimated use was the highest when volumes within 3–6 m were less than 63 m 3/ha. Our results suggest that forest management practices that reduce the amount of structural volume in the understory to mid-canopy provide suitable habitat for foraging bats. Quantifying the amount of structural volume at various heights within the vertical profile of the forest can lend valuable insights into overall and species-specific bat activity patterns.

A Stocking Diagram for Midwestern Eastern Cottonwood-Silver Maple-American Sycamore Bottomland Forests

Abstract A stocking diagram for Midwestern bottomland eastern cottonwood (Populus deltoides Bartram ex Marsh.)-silver maple (Acer saccharinum L.)-American sycamore (Platanus occidentalis L.) forests was developed following the methods of S.F. Gingrich (1967 Measuring and evaluating stocking and stand density in upland hardwood forests in the Central States. For. Sci. 13:38‐53). The stocking diagram was derived from forest inventory data from two different studies of bottomland forests that covered a wide range of soil and hydrologic site characteristics found throughout the central Midwest, including Missouri, Iowa, Illinois, and southern Wisconsin. The minimum of full stocking (B-level) was determined from measurements on open-grown trees. The maximum of full stocking (A-level) in our study was almost one-third higher in stand basal area than A-level stocking, as determined by J.C.G. Goelz (1995. A stocking guide for southern bottomland hardwoods. South. J. Appl. For. 19:103‐104) for southern hardwood bottomlands dominated by cherrybark oak (Quercus pagoda Raf.), Nuttall oak (Quercus nuttallii Palmer), and sweetgum (Liquidambar styraciflua L.,), or by C.C. Myers and R.G. Buchman (1984. Manager's handbook for elm-ash-cottonwood in the north central states. GTR-98. US Forest Service, North Central For. Exp. Stn., St. Paul, MN. 11 p) for elm (Ulmus spp.), ash (Fraxinus spp.), and eastern cottonwood forests in the north central states. However, A-level stocking in this study was only slightly higher than guides developed for northern red oak (Quercus rubra L.) in Wisconsin (McGill, D.W., R. Rogers, A.J. Martin, and P.S. Johnson. 1999. Measuring stocking in northern red oak stands in Wisconsin. North. J. Appl. For. 16:144‐150). Differences in stocking among these forest types are due to variation in species composition, species silvical characteristics, and possibly the data sources used to construct the stocking diagrams. This stocking diagram can be used by forest managers to make decisions related to stand stocking for management of eastern cottonwood, silver maple, and American sycamore bottomland forests in the Midwest.

A stand dynamic model for red pine plantations with different initial densities

A stand dynamic model was developed to predict the growth response in even-aged forest plantations of different initial planting densities. The model is based on the integration of three subcomponents: height growth, self-thinning, and diameter increment. The integrated model uses the height of dominant trees to simulate stand response to site quality and internal growth potential. An extended self-thinning submodel is used to simulate mortality in stands due to crowding and inter-tree competition. A diameter increment submodel is used to link the height growth and self-thinning submodels. The height growth submodel is based on an application of the “Pipe Model” theory. The three-parameter self-thinning submodel is developed from an extended self-thinning law that captures self-thinning in stands before they attain full stocking. The diameter increment model is based on the assumption that diameter increment is related to height growth and available growing space described by stand density. The integrated model is applied to data collected from a 45-year-old red pine (Pinus resinosa Ait.) plantation subsectioned with different initial planting densities. For the data used, only two parameters were required to capture 99% of measured variation in height growth. Additional data from sites with different planting intensities are required to formulate a more generalized height growth model. The slope of the linear self-thinning limit for red pine is approximately −1.5. Model predictions are consistent with field measurements.

Effect of Thinning on Aboveground Biomass Accumulation and Distribution in Naturally Regenerated Shortleaf Pine

Abstract The accumulation and relative distribution of standing biomass to different aboveground tree components was investigated in 46–53-year-old naturally regenerated shortleaf pine (Pinus echinata Mill.) stands growing in the Ouachita Mountains of southeastern Oklahoma that were thinned to different levels 16 years previously. The thinning levels were 50% full stocking, 70% full stocking, and a 140% full stocking unthinned control. After 16 years, the unthinned controls had more total aboveground biomass, bole wood, bark, and foliage standing biomass per hectare but had less branch standing biomass than the more heavily thinned stands. Foliage biomass as a proportion of total stand biomass was similar among the three treatment levels. Bark biomass proportion was significantly less in thinned to 50% treatment compared with the other treatments. Bole wood biomass proportion in thinned to 50% treatment was significantly less than in the control. The proportion in branches was significantly greater in the thinned treatments compared with the proportion in the unthinned control. These results suggest that thinning increases biomass distribution to branches at the expense of stems, after 16 years of postthinning stand growth.

Tree Biomass Equations for Naturally Regenerated Shortleaf Pine

Abstract Aboveground tree-level and branch-level biomass component equations were fitted by nonlinear seemingly unrelated regression, for even-aged naturally regenerated shortleaf pine (Pinus echinata Mill.) in southeastern Oklahoma. Data were obtained from 46- to 53-year-old trees growing in stands that had previously been thinned to densities ranging from 50% of full stocking to overstocked unthinned stands. Stand density affected some of the parameter estimates for trees growing in thinned stands versus unthinned stands. Equations based on dbh alone gave biomass estimates that were not significantly different from those obtained with equations based on dbh, height, and/or crown width. The fitted tree-level biomass component equations were additive in the sense that predictions for biomass components were constrained by the estimation process to sum to total tree biomass. These equations can be used to estimate aboveground tree or tree component biomass for naturally regenerated shortleaf pine in the dbh range of 7–40 cm in southeastern Oklahoma and have potential for application in other shortleaf pine growing areas.

Oak Regeneration Guidelines for the Central Appalachians

Abstract This article presents the first explicit guidelines for regenerating oaks in the central Appalachians. The objectives of this paper are (1) to describe the research foundation on which the guidelines are based and (2) to provide users with the instructions, data collection forms, supplementarytables, and decision charts needed to apply the guidelines in the field. The principal research foundation for the guidelines is a set of quantitative models that estimate, in advance of harvest, a stand's potential to regenerate oak stocking from advance regeneration and stump sprouts. Regeneration potential is measured by the predicted stocking by oak species, expressed as a percentage of full (100%) stocking, in the new stand in its third decade (21–30 years) after overstory removal. An understory classification system is used in conjunction with the models to help identifypotential barriers to regeneration development. Model results and other data on current stand conditions are used in the decision charts to identify prescriptions for achieving a strong component of oak regeneration after stand harvest. Overstory removals are recommended when the stand's oak regeneration potential is adequate to meet management goals. Otherwise, prescriptions designed to enhance seedling-origin oak regeneration potential are recommended.

Assessing the Hazard of Emerald Ash Borer and Other Exotic Stressors to Community Forests

Exotic stressors such as emerald ash borer are an increasing concern to many communities across North America. One means of assessing the hazard these stressors may represent to a community’s publicly managed trees is through an inventory of their street trees. The South Dakota Division of Resource Conservation and Forestry conducted street tree inventories in selected communities across the state and, from these data, have placed communities into stability categories based on the percentage of full stocking that each genera represents within the street tree population. The majority of surveyed communities are in the low stability category as a result of the dominance of green ash in their street tree populations.

Natural regeneration of lodgepole pine following partial harvesting on northern caribou winter range in west-central British Columbia

This study compares pine natural regeneration density and height growth in small harvested openings (0.01–0.07 ha) within two biogeoclimatic subzones (Sub-Boreal Pine–Spruce [SBPS] xc and Montane Spruce [MS] xv) and three partial harvesting treatments on northern caribou (Rangifer tarandus caribou Gmelin) winter range in the western Chilcotin region of British Columbia, Canada. Regeneration density was assessed annually for 7 years (1996–2002). In year 7, post-logging ingress stems > 1 year old had a significantly greater density on SBPSxc blocks (5898 stems per hectare) than on the higher-elevation MSxv blocks (1829 stems per hectare). The percentage of 2-m2 plots with a natural post-logging seedling > 1 year old averaged 52% in the SBPSxc and 31% in the MSxv. Advance regeneration added substantially to density and stocking in the SBPSxc but not in the MSxv. These results indicate that small (0.01–0.07 ha) harvested openings in the SBPSxc can be naturally restocked by lodgepole pine without post-logging site preparation, but higher-elevation blocks in the MSxv will need to be planted to ensure full stocking by lodgepole pine within 7 years. However, the long period between harvest entries on caribou winter range may still allow sufficient time to naturally regenerate openings in the MSxv.

Flower stimulation in young miniaturized seed orchards of Douglas-fir (Pseudotsuga menziesii)

We studied flower stimulation in two young miniaturized seed orchards of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) in Oregon. In experiment 1, female and male flowering were substantially enhanced when the trees were treated 2–4 years after grafting with stem girdling plus stem-injected gibberellin A4/7 (GA 0.25× rate = ProCone(tm) at 0.084 µL·mm–2 scion cross-sectional area). Comparable results were obtained the following year when the same trees were retreated with 1× GA. In experiment 2, female and male flowering were significantly enhanced when 3-year-old trees were treated with girdling plus either 1× GA, 1.5× GA, or 2× GA. Some treatments had higher mortality and less height growth than the control in the year of cone development. We recommend using a combination of girdling and 1× GA biennially once trees are large enough to produce large per-hectare seed yields and withstand the stress of flower stimulation. At the study orchards, this seems to be about 5 years postgrafting, just before the sixth growing season. Yields were estimated to be 272 963 seeds·ha–1 at age 4 years, or 143 095 seeds·ha–1 annually with stimulation occurring every 2 years. Yields should increase as orchards age, with full stocking, and with higher planting densities.

Post-harvest Regeneration of Lowland Black Spruce Forests in Northeastern Ontario

Success of natural regeneration has been a concern since the introduction of heavy machinery in harvesting. The objective was to compare the effect of three operational harvest methods careful logging around advanced growth (CLAAG), group seed tree (GST), and group seed tree followed by shearblading site preparation (SHE) on natural regeneration in the Clay Belt region of Ontario. A total of 30 stands, 562 cluster sample plots, were surveyed. Total density of black spruce regeneration did not differ, but height structure of black spruce regeneration did among harvest methods. The CLAAG method resulted in highest total regeneration density of other conifers. Decreasing density of other conifers from the CLAAG to GST to SHE sites indicated that the CLAAG method protected advance regeneration as expected and the SHE method removed advance regeneration in the path of the shearing blade. Both black spruce and other conifer regeneration densities increased with increasing time since harvest. Stocking of black spruce, all conifers, or all tree species did not differ significantly among harvest methods, nor did it change with time since harvest. Stocking was nonlinearly related to regeneration density. Models developed in this study predict that full stocking (i.e., 60%) can be reached based on regeneration density of 5000 stems per ha regardless of crop species choice preference. However, the existing stocking criterion for assessing black spruce regeneration may be problematic.

Vegetative Characteristics of Recently Reforested Bottomlands in the Lower Cache River Watershed, Illinois, U.S.A.

Abstract Interest in restoring native ecosystems is resulting in conversion of marginal agricultural lands to bottomland hardwood‐dominated forests in the midwestern and midsouthern United States. Growing stock for these efforts typically consists of planted oak (Quercus spp.) and volunteer vegetation. Reports of mixed reforestation success and the lack of post‐establishment tree growth data prompted this evaluation of vegetation characteristics of 5‐ to 7‐year‐old operational restorations in the Lower Cache River Watershed in southernmost Illinois, U.S.A. Fraxinus pennsylvanica (green ash), Acer negundo (box‐elder), and Liquidambar styraciflua (sweetgum) together comprised 77% of all tree stems observed. Full stocking of overstory tree species can be expected to produce a closed canopy stand within 160 m of a forested edge, due primarily to the abundance of rapidly growing volunteer‐origin trees. Planted oaks contributed minimally to total tree stocking but were present in sufficient numbers to eventually improve wildlife habitat, and therefore satisfied restoration objectives. Oak height was 23% greater when in the presence of a non‐oak tree species. Herbaceous cover was dominated by Solidago gigantea (late goldenrod) and Juncus spp. (rushes). Solidago gigantea was associated with poor growth and low density of non‐oak stems, whereas Juncus dudleyi (Dudley's rush) was associated with taller non‐oak stems. These results suggest that the presence of volunteer‐origin trees is crucial for the creation of full stand stocking that will result in rapid development of a closed canopy forest. Improved success of future reforestation efforts will require more intensive methods to establish adequate stocking beyond 160 m of a forest edge. Methods described here could be adapted for agricultural field to forest restorations in other regions to predict critical distances from volunteer seed sources within which supplemental planting would be unnecessary to meet tree stocking objectives.