Winter Burns Research Articles

EFFECTS OF PRESCRIBED FIRE ON HERPETOFAUNA IN BOTTOMLAND HARDWOOD FORESTS

Abstract Abundance, diversity, and richness of herpetofaunal species were compared between burned and unburned bottomland hardwood stands at Di-Lane Plantation Wildlife Management Area (WMA) in Burke County, Georgia, from July to October 2001. Two trap clusters, each consisting of a drift fence pitfall array, four coverboards, and three polyvinyl chloride (PVC) pipe refugia, were randomly placed within each of three burned and three unburned stands. Habitat variables were measured within a 0.04-ha circular plot centered on each trap cluster. A total of 346 individuals, representing 21 species, was captured in 348 array nights. Amphibian abundance, diversity, and richness were similar between burned and unburned stands. Reptile abundance and diversity were greater in burned stands, whereas reptile species richness was similar between burned and unburned stands. Winter burns did not significantly affect coarse woody debris volumes between burned and unburned stands and may have accounted for similar amphibi...

Effects of Alternative Thinning Regimes and Prescribed Burning in Natural, Even-Aged Loblolly–Shortleaf Pine Stands: 25 Year Results

Abstract In southeastern Arkansas, pine growth was monitored for 19 yr after mechanically strip thinning a dense, naturally regenerated, even-aged stand of 6-yr-old loblolly pines (Pinus taeda L.) and shortleaf pines (P. echinata Mill.) that averaged 16,600 stems/ac. Prescribed winter burns were conducted biennially between ages 9 and 20 yr and at 24 yr. Commercial thinnings during the 17th and 23rd growing seasons left a residual stocking of either 85 ft2/ac or 200 crop trees/ac (75 ft2/ac) in merchantable-sized (> 3.5 in. dbh) pines on plots that were precommercially thinned and on plots that were not. Precommercial thinning enhanced pine growth in dbh and sawlog volume through 25 yr. Because of increased sawlog production, present net value averaged highest on plots that were precommercially thinned at age 6 then commercially thinned during the 17th yr to 200 crop trees/ac and during the 23rd yr to 75 ft2/ac. In the year following prescribed winter burns, both dbh growth and volume growth were reduced by about one-half when crown scorch was 75%. South. J. Appl. For. 27(1):18–29.

Does Prescribed Burning Have a Place in Regenerating Uneven-Aged Loblolly-Shortleaf Pine Stands?

Abstract Before the 1981 growing season, a study was installed in southeastern Arkansas to examine the effects of three dormant-season burn intervals (low, moderate, and high frequency) and an unburned treatment on natural regeneration in uneven-aged stands of loblolly and shortleaf pines (Pinus taeda andP. echinata, respectively). Merchantable pine basal areas were maintained by harvesting on a 5 or 6 yr cutting cycle. When the study began, hardwoods greater than 1 in. dbh were injected with herbicide on all plots. During the next 19 yr, there were eight high frequency, four moderate frequency, and three low frequency prescribed burns. In 1991, the unburned plots received a single, broadcast-herbicide treatment. Single-tree selection harvests were conducted in 1982, 1987, 1992, and 1997. Through 1999 (19 yr), herbicides applied at 10 yr intervals were more effective than dormant-season burns for enhancing the growth of submerchantable pines. Although recurring winter burns tended to stop the progression of both pines and hardwoods from seedling to sapling size classes, the data suggest that properly timed dormant-season burns might be used to secure natural pine regeneration in selection management. South. J. Appl. For. 26(3):117–123.

Success of Artificial Bird Nests in Burned Gulf Coast Chenier Plain Marshes

Wildlife managers in the Gulf Coast Chenier Plain of Louisiana and Texas frequently burn marshes during winter to improve habitat for wintering waterfowl and furbearers. Such fires dramatically alter vegetation structure and cover, although such changes are generally temporary. However, if vegetation cover does not recover sufficiently by the start of the subsequent breeding season, nests of marsh birds could be exposed to increased predation rates. We examined effects of burning on 2 measures of vegetation structure and on 2 types of artificial bird nests during breeding seasons (May and June) before and after experimental winter burns (December and January). We found that vegetation structure did not differ between burned and non-burned marshes at 5 months post-burn. Similarly, depredation rates of artificial sparrow and duck nests did not differ between burned and non-burned marshes during the post-burn breeding season. We recommend that managers complete burning programs by the end of January so that sufficient nesting cover develops before the start of the breeding season.

Habitat Selection and Habitat Use by the Bog Turtle (Clemmys muhlenbergii) in Maryland

Habitat selection of 50 bog turtles (Clemmys muhlenbergii) was studied at two sites in Harford County, Maryland, from April 1996 to August 1997. These sites differ in size, amount of grazing, and stage of vegetative succession. In addition, one of the sites was studied intensively 20 years ago. Turtle movements were monitored using radiotelemetry: Individuals were located twice a week during the active season and once a month during hibernation to assess habitat selection and seasonal changes in habitat use. Vegetative, soil, and water characteristics were recorded in 0.25-m2 quadrats placed at turtle locations and stratified random locations throughout the study areas. Turtles selected sedges and rushes and other low-lying her- baceous plants. They avoided some woody plants (alders, grapes, and berries) and an exotic plant (Japanese honeysuckle, Lonicera japonica) that may gradually eliminate typical wetland vegetation and produce a closed canopy. Management practices, such as moderate animal grazing and winter burns, will help retard plant succession and provide more open habitat. Concern about the long-term persistence of the bog turtle (Clemmys muhlenbergii) has result- ed in federal listing of the bog turtle as a threat- ened species (U.S. Fish and Wildlife Service,

A comparison of the impacts of winter versus summer burning of slash fuel in alien-invaded fynbos areas in the Western Cape

Synopsis Dense slash from cleared stands of invasive alien trees in mountain catchment areas poses a hazard to fynbos recovery and soil stability, ifit burns under extreme summer weather conditions. Experimental burning of alien slash fuel was done to investigate whether winter burning of fuel may be used as a practical alternative to risking a summer wild fire. Fire intensity, heat release at the soil surface and indigenous post-fire plant recruitment were compared between different blocks of the same felled alien stand, which burnt during a controlled winter burn and a summer wild fire. Both fires consumed nearly all the fuel, but fire intensity and heat penetration into the soil were much greater for the summer wild fire than the winter control burn. Fynbos plant recruitment following the main winter establishment season was extremely low in the summer burn, and indicated that propagules in the upper soil had been killed in the fire. Species that emerged following the summer burn were predominantly resprouters or species with larger seeds that could emerge from deeper in the soil. Plant recruitment, species richness and cover were much higher following the winter burn. Half the species (mainly forbs, resprouters and legumes) appeared during the summer after the fire, but the remainder appeared only after the main winter establishment season. Small-seeded species were few and indicated that all germination cues were not optimized by burning in winter. Alternatively, soil-heating during the winter burn was sufficient to kill small seeds located close to the surface. Comparisons between summer slash fires on granite versus sandstone parent materials suggest that the impacts are much greater on the granite. The impacts were also greater where fuel loads are high. It is recommended that summer burning ofslash fuel be avoided in all areas supporting old (>8 yr), dense (>75%cover) alien stands. Furthermore, summer slash fires also should be avoided for moderately dense (>50%)alien stands on shale bands or granite-derived soils. As an interim strategy in these areas, winter burning offuel should be considered to prevent excessive soil and propagule damage during a summerwild fire. However, future alternatives, such as the immediate targeting of low-density stands and the implementation of biological control agents, urgently should be sought.

Response of Breeding Florida Grasshopper and Bachman's Sparrows to Winter Prescribed Burning

Populations of Florida grasshopper (Ammodramus savannarum floridanus) and Bachman's sparrows (Aimophila aestivalis) are small and declining. Prescribed burning is the primary management tool used to maintain their grassland habitats, but the effects of this management practice on the breeding density and reproductive success of these populations are poorly understood. We conducted a 3-year spot-mapping study of 3 winter burn classes (0.5-yr, 1.5-yr, and 2.5-yr postfire) in native dry prairie on 2 sites in central Florida to determine the effects of fire management on breeding density and reproductive success of these 2 sparrows. Florida grasshopper sparrow densities were greater on recently burned plots (0.5 yr postburn: x = 4.0 ± 1 territories/10 ha (x ± SE); 1.5 yr postburn x = 3.4 ± 0.8 territories/10 ha) than on plots that had not been burned in 2.5 years (x = 1.8 ± 0.8 territories/10 ha). Grasshopper sparrow reproductive success was also higher in recently burned plots (0.5 yr postburn; x = 1.6 successful territories/plot) than in 2.5-year burn plots (x = 0.6 successful territories/plot). In contrast, Bachman sparrow breeding densities and reproductive success were not affected by fire management rotation. Our results indicate that a fire rotation of ≤3 years is necessary to maintain suitable breeding habitat for Florida grasshopper sparrows but does not appear to negatively affect breeding Bachman's sparrows.

Survival and growth of Pinus echinata and Quercus seedlings in response to simulated summer and winter prescribed burns

First-year seedlings of shortleaf pine (Pinus echinata Mill.), southern red oak (Quercus falcata Michx.), and white oak (Quercus alba L.) were subjected to simulated prescribed burns during August (growing season) or January (dormant season) on an Upper Coastal Plain site in southeastern Arkansas, U.S.A. Survival and growth of resprouting rootstocks were compared with control seedlings through one growing season after burning. Although 100% of the oaks and 99% of the pines were topkilled by the fires, survival of resprouting rootstocks exceeded 95% for all three species in the year following the winter burn. No pines resprouted following the summer burn, but rootstock survival of oaks averaged >65%. Compared with controls, winter burns reduced (P < 0.01) mean height and groundline diameter (GLD) of shortleaf pine sprouts through the next growing season. For southern red oak, season of burning did not negatively affect (P > 0.05) the growth of sprouts during the year after burning. Although mean heights and GLDs of white oak sprouts versus controls were reduced (P [Formula: see text] 0.04) when means were averaged across burns, white oak sprouts on winter-burn plots were comparable in size with the control seedlings.

EFFECTS OF WINTER MARSH BURNING ON ABUNDANCE AND NESTING ACTIVITY OF LOUISIANA SEASIDE SPARROWS IN THE GULF COAST CHENIER PLAIN

Abstract Louisiana Seaside Sparrows (Ammodramus maritimus fisheri) breed and winter exclusively in brackish and saline marshes along the northern Gulf of Mexico. Many Gulf Coast marshes, particularly in the Chenier Plain of southwestern Louisiana and southeastern Texas, are burned intentionally in fall or winter as part of waterfowl management programs. Fire reportedly has negatively affected two Seaside Sparrow subspecies (A. m. nigrescens and A. m. mirabilis) in Florida, but there is no published information regarding effects of fire on A. m. fisheri. We compared abundance of territorial male Louisiana Seaside Sparrows, number of nesting activity indicators, and vegetation structure in paired burned and unburned plots in Chenier Plain marshes in southwestern Louisiana during the 1996 breeding season (April–July) before experimental winter burns (January 1997) and again during two breeding seasons post-burn (1997–1998). We found that abundance of male sparrows decreased in burned plots during the first b...

Plant size and season of burn affect flowering and fruiting of the grasstree Xanthorrhoea preissii

AbstractFlowering and fruiting were assessed on 14 populations of the grasstree, Xanthorrhoea preissii Endl., occurring in the Darling Range near Perth, Western Australia. Independent of site, season of burn or year of flowering, there was a strong relationship between plant height, which varied from 0.1 to over 2 m, and the incidence of postfire flowering, which varied from 1% (winter burn) to 75% (summer burn) of grasstrees present. There was no relationship between inflorescence dimensions, or flower or fruit production on a spike basis, and plant size/age (height). When standardized for height, spring‐burnt populations produced 40% as many inflorescences as autumn‐burnt populations and 20% as many as summer‐burnt populations. Inflorescences produced by spring‐burnt plants were moderately smaller than those by summer–autumn‐burnt plants. Fruit density per spike in autumn‐burnt plants was 80% of that in spring–summer‐burnt plants. The net effect was an average of 70 000 fruits produced per 100 summer‐burnt plants, 22 000 in autumn‐burnt plants, and 14 000 in spring‐burnt plants. Ecophysiological explanations of these results and their implications for population dynamics have yet to be explored.

Effects of Seasonal Prescribed Fires on Residual Overstory Trees in Oak-Dominated Shelterwood Stands

Abstract A study was initiated in 1994 to evaluate the degree of bole damage and crown decline residual overstory trees would experience because of prescribed burning of shelterwood stands. Three oak-dominated shelterwood stands, partially harvested 2 to 4 yr earlier, were divided into four treatments (unburned control, spring burn, summer burn, and winter burn). Fifteen permanent sampling points were systematically located in each 5 to 12 ac treatment area, and overstory trees were selected from these points with a 10 BAF prism. Before burning, each tree was evaluated for lower bole and crown condition and reevaluated two growing seasons after the fires. Hickory, oak, and yellow-poplar were largely unaffected by the winter and summer prescribed fires but displayed bole damage and crown decline following spring burning. American beech and red maple declined after all fire treatments. Fire damage to oak, hickory, and yellow-poplar was strongly associated to presence of logging slash near a tree's base. Directional felling or moving slash should minimize injury to these trees. This research will aid resource managers wishing to use prescribed fire in shelterwood stands to favor oak regeneration while minimizing damage to residual overstory oaks. South. J. Appl. For. 23(2):88-93.

Using shelterwood harvests and prescribed fire to regenerate oak stands on productive upland sites

Regenerating oak stands on productive upland sites in the Piedmont region is a major problem because of intense competition from yellow-poplar. As a potential solution to this problem, we tested the hypothesis that a shelterwood harvest of an oak-dominated stand, followed several years later by a prescribed fire, would adequately regenerate the stand. Three oak-dominated stands, in which shelterwood harvests had been conducted several years earlier, were each divided into spring burn, summer burn, winter burn, and control treatments. Three years after the prescribed fires, oak had higher density and stocking in burned as compared to unburned areas while yellow-poplar had its highest density and stocking in the controls. Season-of-burn interacted with fire intensity to create several probable outcomes of stand development. Areas treated with high-intensity fire during the spring will develop into oak-dominated stands after just one burn. Controls and areas treated with low-intensity fire will become dominated by yellow-poplar. Other combinations of fire intensity and season-of-burn will produce mixed hardwood stands with varying proportions of oak. Combining shelterwood harvesting with prescribed fire appears to be a viable method for regenerating oak stands on productive upland sites in the Piedmont region and may be applicable elsewhere.

Prescribed Fire Effects on Advanced Regeneration in Mixed Hardwood Stands

Abstract Fire treatments were initiated in 1990 to evaluate effects of low-intensity prescribed fires on composition and structure of the advanced regeneration pool under mature mixed-hardwood stands on upland sites in the Piedmont of South Carolina. One spring burn was as effective as three winter burns in reducing midstory density, considered a prerequisite for subsequent development of oak (Quercus spp.) advanced regeneration. Burning increased the number of oak rootstocks, reduced the relative position of competing species, and increased root-to-shoot ratios of oak stems in the regeneration layer. These favorable effects of fire on oak regeneration outweigh the removal of small, poorly formed oak stems from the midstory/understory strata during burning. Prescribed burning in hardwood forests may solve some of the current oak regeneration problems, especially on better upland sites in the South. South. J. Appl. For. 22(3):138-142.

Responses of hardwood advance regeneration to seasonal prescribed fires in oak-dominated shelterwood stands

Effects of seasonal prescribed fires of varying intensities on density, mortality, stem form, height, and height growth of hardwood advance regeneration were investigated. Three mixed-hardwood stands on productive upland sites were cut using a shelterwood technique, each forming a block of spring burn, summer burn, winter burn, and control treatments. Advance regeneration was inventoried from permanent plots before and after burning. Fires top-killed nearly all hardwood regeneration, forcing the rootstocks to sprout. Fire treatments reduced densities of all hardwood species relative to not burning, with spring and summer fires causing greater density reduction than winter burning. Among species, oak (Quercus spp. L.) and hickory (Carya spp. Nutt.) were more resilient sprouters than yellow-poplar (Liriodendron tulipifera L.) and red maple (Acer rubrum L.), especially as fire intensity increased. All prescribed fires improved oak stem form and stimulated height growth of hickory and oak. Overall, prescribed fires improved oak advance regeneration with spring burning providing the most benefit. This approach of following a shelterwood harvest with prescribed fire may be a viable method of regenerating oak-dominated stands on productive upland sites.

Liparis loeselii (L.) Rich. in eastern England: constraints on distribution and population development

The fenland form of Liparis loeselii is currently known from only three sites in eastern England, having been lost from about 30 former localities since the start of the nineteenth century. The reason for its loss is sometimes uncertain, but in only a small number of instances can it be attributed confidently to drainage. The habitat of the current Liparis populations, all in the Norfolk Broadland, can be summarized as ‘base-rich, wet, low-fertility, herbaceous fen’. Vegetation management, usually summer mowing, helps maintain the relatively low-growing, herbaceous vegetation that the orchid requires. In addition, all localities are in reflooded turbaries, the plant growing on a relatively buoyant mat of vegetation. Many former Liparis localities were apparently of similar character. Demographic studies on tagged plants in ten permanent plots in one population (Sutton Fen) between 1983 and 1990 showed that individuals were mostly short-lived but developed quickly. Small (young) individuals had particularly high mortalities and the majority died without flowering; individuals frequently, but not invariably, increased their leaf dimensions in successive years; flowering was almost entirely restricted to 2-leaved plants, especially robust individuals, and most flowering individuals re-appeared in the next growing season. The main period of emergence was between mid-June and mid-July, though some individuals that emerged in mid-June disappeared by mid-July (apparently due to mollusc grazing). The number of plants in the population showed considerable flux (though not all plots showed the same trends). A peak of numbers in some plots in 1986 and 1987(due to both high rates of recruitment and low mortality) was followed by a crash in 1988 and 1990. This affected the entire population (1990 numbers were about one third of those in 1983) but was particularly evident in plots which had shown an earlier strong increase in numbers. The population peak occurred after a winter burn and may have occurred in response to this. The cause of the subsequent decline is not known with certainty but it was associated with lack of vegetation management, low fen water levels (lack of surface inundation) at the time of emergence of Liparis plants and mollusc grazing damage. The effects of these events are difficult to disentangle, but grazing damage, perhaps facilitated by lack of shallow flooding at the time of shoot emergence, may be the proximate cause of loss. The short-lived character of many Liparis individuals and the quite rapid population turnover suggests that effective conservation management must provide conditions suitable for recruitment of new individuals as well as the maintenance of established plants, but the character of suitable regeneration niches is not well understood. It is possible thatperpetuation of Liparis populations may require some disturbance (perhaps winter burning or light trampling) as well as mowing. Rejuvenation of the hydrosere, by further peat removal, may be another long-term requirement.

Liparis loeselii(L.) Rich. in eastern England: constraints on distribution and population development

The fenland form ofLiparis loeseliiis currently known from only three sites in eastern England, having been lost from about 30 former localities since the start of the nineteenth century. The reason for its loss is sometimes uncertain, but in only a small number of instances can it be attributed confidently to drainage. The habitat of the currentLiparispopulations, all in the Norfolk Broadland, can be summarized as «base-rich, wet, low-fertility, herbaceous fen». Vegetation management, usually summer mowing, helps maintain the relatively low-growing, herbaceous vegetation that the orchid requires. In addition, all localities are in reflooded turbaries, the plant growing on a relatively buoyant mat of vegetation. Many formerLiparislocalities were apparently of similar character. Demographic studies on tagged plants in ten permanent plots in one population (Sutton Fen) between 1983 and 1990 showed that individuals were mostly short-lived but developed quickly. Small (young) individuals had particularly high mortalities and the majority died without flowering; individuals frequently, but not invariably, increased their leaf dimensions in successive years; flowering was almost entirely restricted to 2-leaved plants, especially robust individuals, and most flowering individuals re-appeared in the next growing season. The main period of emergence was between mid-June and mid-July, though some individuals that emerged in mid-June disappeared by mid-July (apparently due to mollusc grazing). The number of plants in the population showed considerable flux (though not all plots showed the same trends). A peak of numbers in some plots in 1986 and 1987 (due to both high rates of recruitment and low mortality) was followed by a crash in 1988 and 1990. This affected the entire population (1990 numbers were about one third of those in 1983) but was particularly evident in plots which had shown an earlier strong increase in numbers. The population peak occurred after a winter burn and may have occurred in response to this. The cause of the subsequent decline is not known with certainty but it was associated with lack of vegetation management, low fen water levels (lack of surface inundation) at the time of emergence ofLiparisplants and mollusc grazing damage. The effects of these events are difficult to disentangle, but grazing damage, perhaps facilitated by lack of shallow flooding at the time of shoot emergence, may be the proximate cause of loss. The short-lived character of manyLiparisindividuals and the quite rapid population turnover suggests that effective conservation management must provide conditions suitable for recruitment of new individuals as well as the maintenance of established plants, but the character of suitable regeneration niches is not well understood. It is possible thatperpetuation ofLiparispopulations may require some disturbance (perhaps winter burning or light trampling) as well as mowing. Rejuvenation of the hydrosere, by further peat removal, may be another long-term requirement.

Viability of Litter-Stored Quercus falcata Michx. Acorns After Simulated Prescribed Winter Burns

Partially stratified (11 days) southern red oak (Quercus falcata Michx.) acorns were placed at three depths in a reconstructed forest floor and subjected to simulated prescribed winter burns. Within the forest floor, acorns were placed within the L layer, at the upper-F/lower-F interface, and at the lower-F/mineral-soil interface. Winds for a backfire and headfire were generated by electric box-fans. After the burns, acorns were transferred to moist sand flats, stratified for an additional 16 days, then assessed for viability during a 45-day germination test. As depth within the forest floor increased, germinative capacity of acorns increased. All acorns placed within the L layer during prescribed burning failed to germinate. Germinative capacity of acorns placed at the upper-F/lower-F interface was lower (P=0.03) in the backfire (8.75%) than in the headfire (55.00%). At the lower-F/mineral-soil interface, there was no difference (P=0.09) in germinative capacity between backfire (92%) and headfire (89%), and their mean was no different (P=0.26) than the 93% achieved by unburned control acorns.

Viability of litter-stored Pinus taeda L. seeds after simulated prescribed winter burns

Stratified loblolly pine (Pinus taeda L.) seeds were placed at three depths in a reconstructed forest floor and subjected to simulated prescribed winter burns. Within the forest floor, pine seeds were placed at the L/upper-F interface, upper-F/lower-F interface, and lower-F/mineral-soil interface. Wind was generated by electric box-fans. Seeds that survived the burns were transferred to moist sand flats for 30-day germination tests. About 96% of seeds placed at the two upper layers in the forest floor were either destroyed by the fires or failed to germinate. Germinative capacity of seeds placed at the lower-F/mineral-soil interface averaged 79% as compared to 97% for unburned control seeds.

Impact of Prescribed Burning on Vegetation and Bird Abundance at Matagorda Island, Texas

We measured the impact of prescribed summer and winter burns on vegetation characteristics and spring abundance of birds in a Spartina/Paspalum grassland at Matagorda Island National Wildlife Refuge and State Natural Area, Texas, 1993-94. We burned 8 (4 summer burn, 4 winter burn), 122-ha plots. We estimated bird abundance by surveying once a week from March through May at 12-16 fixed-radius point count stations in each plot. We measured forb and grass foliar cover, litter depth, visual obstruction, and woody and residual stem density at each point count station 6-10 months after burning and 18-22 months after burning and found few differences in vegetation between summer and winter burns. Litter depth, visual obstruction, and woody stem density values were greater on control plots 6 to 10 months post-burn. By 18 to 22 months post-burn, only litter depth and visual obstruction remained higher on control plots than on either burn treatment. At 6 to 10 months after burning, wrens were more abundant on control plots and sparrows were more abundant on the burned plots. By 18 to 22 months post-burn, wren abundance had increased on the burned plots, but was still highest on control plots. Sparrow abundance remained highest on burned plots 18-22 months after burning. Precipitation was higher in 1993 than 1994; we believe blackbirds responded more to annual precipitation differences than to burning treatment. In this coastal island grassland, wren abundance was highest on unburned plots and sparrow abundance was highest on burned plots. We suggest that land managers could burn at > 2 year intervals in this grassland without negatively impacting most resident bird species.

Growth expectations from alternative thinning regimes and prescribed burning in naturally regenerated loblolly-shortleaf pine stands through age 20

Pine growth was monitored for 14 years after mechanically strip-thinning a dense, naturally regenerated, even-aged stand of 6-year-old loblolly pines ( Pinus taeda L.) and shortleaf pines ( Pinus echinata Mill.) that averaged 41000 trees per hectare in southeastern Arkansas, USA. Prescribed winter burns were conducted biennially between ages 9 and 20 years. A commercial thinning during the 17th growing season left a residual stocking of either 19.5 m 2 ha −1 or 494 crop trees ha −1 in merchantable-sized ( > 9.0 cm dbh) pines on plots that were precommercially thinned and on plots that were not. Precommercial thinning enhanced pine growth in total height and in diameter at breast height (dbh, taken at 1.37 m) through stand age 20 years. At age 20, present net value (PNV) averaged highest on plots that were precommercially thinned at age 6 then commercially thinned to 494 crop trees per hectare after 16 years because of increased production in sawtimber (trees over 24 cm dbh). The second highest PNV at age 20 was on unmanaged control plots because no costs were incurred for precommercial thinning, hardwood injection, prescribed burning, or timber sale administration. Within each thinning treatment, pine dbh growth decreased in the 18th and 20th year relative to an increase in the degree of crown scorch from prescribed winter burns that were conducted after 17 and 19 years, respectively.