White Pine Plantation Research Articles

Radiation use efficiency in adjacent hardwood and pine forests in the southern Appalachians

The efficiency with which trees convert photosynthetically active radiation (PAR) to biomass has been shown to be consistent within stands of an individual species, which is useful for estimating biomass production and carbon accumulation. However, radiation use efficiency ( ɛ) has rarely been measured in mixed-species forests, and it is unclear how species diversity may affect the consistency of ɛ, particularly across environmental gradients. We compared aboveground net primary productivity (ANPP), intercepted photosynthetically active solar radiation (IPAR), and radiation use efficiency ( ɛ = ANPP/IPAR) between a mixed deciduous forest and a 50-year-old white pine ( Pinus strobus L.) plantation in the southern Appalachian Mountains. Average ANPP was similar in the deciduous forest (11.5 Mg ha −1 y −1) and pine plantation (10.2 Mg ha −1 y −1), while ɛ was significantly greater in the deciduous forest (1.25 g MJ −1) than in the white pine plantation (0.63 g MJ −1). Our results demonstrate that late-secondary hardwood forests can attain similar ANPP as mature P. strobus plantations in the southern Appalachians, despite substantially less annual IPAR and mineral-nitrogen availability, suggesting greater resource-use efficiency and potential for long-term carbon accumulation in biomass. Along a 260 m elevation gradient within each forest there was not significant variation in ɛ. Radiation use efficiency may be stable for specific forest types across a range of environmental conditions in the southern Appalachian Mountains, and thus useful for generating estimates of ANPP at the scale of individual watersheds.

Site and Stand Conditions Associated with Pine False Webworm Populations and Damage in Mature Eastern White Pine Plantations

Abstract The influence of site and stand conditions on pine false webworm (Acantholyda erythrocephala [L.], Hymenoptera: Pamphiliidae) population densities and host damage was evaluated in 22 eastern white pine (Pinus strobus L.) stands in northern New York State. Mean pine false webworm density was positively related to stand size (ha) and inversely related to soil silt content (A-horizon) after holding stand size constant. Percent radial growth loss (during the first five years after defoliation began) was inversely related to soil carbon content (B-horizon) and inversely related to fine sand content (A-horizon) after holding B-horizon carbon constant. Severe radial growth suppression (missing or discontinuous growth rings) and white pine mortality were inversely related to live crown ratio. The frequency of trees with missing growth rings was inversely related to soil nitrogen (A-horizon) after holding live crown ratio constant. Stands located on sandy glacial lake shoreline/delta deposits had more coarsely textured soils with lower levels of organic matter and nitrogen and had slower height growth rates, lower tree diversity, greater relative dominance of white pine, and higher levels of pine false webworm defoliation than stands on adjacent landforms. These results may be useful to foresters managing eastern white pine stands in areas where similar site and stand conditions predominate and pine false webworm occurs.

A comparison of sap flux-based evapotranspiration estimates with catchment-scale water balance

Many researchers are using sap flux to estimate tree-level transpiration, and to scale to stand- and catchment-level transpiration; yet studies evaluating the comparability of sap flux-based estimates of transpiration ( E t) with alternative methods for estimating E t at this spatial scale are rare. Our ability to accurately scale from the probe to the tree to the watershed has not yet been demonstrated, nor do we know the relative impact of the main sources of variability on our scaled estimates. Accounting for the variability in the radial distribution of sap flux within the sapwood, the variability of transpiration among trees and between plots within the catchment, and the variability in stand density, sapwood area, and leaf area are critical for making landscape inferences about transpiration. During 2004 and 2005, we continuously monitored 40 trees in three plots within a 13.5-ha gauged watershed comprising a 50-year-old eastern white pine plantation within the Coweeta Basin in western North Carolina, USA. We scaled sap flux-based estimates of stand transpiration ( E t) and surface area-based estimates of stand interception ( E i) to the catchment and compared these with water balance estimates of evapotranspiration ( E, precipitation minus runoff, P − R o). For both years, the sum of sap flux scaled E t and E i were 14 and 7% lower than evapotranspiration estimated from P − R o. Our results show that a considerable amount of variation exists at each scaling step encountered; however, a simple scaling exercise revealed that omitting among plot variation affected the sap flux scaled E t estimate by 48%. Thus, the largest source of variability in scaling to the landscape was landscape variation in stand density and sapwood area.

Long-term effects of intensive silvicultural practices on productivity, composition, and structure of northern temperate and boreal plantations in Ontario, Canada

Long-term interactive effects of site preparation, brush control and fertilization treatments on productivity, composition and structure were examined on jack pine ( Pinus banksiana Lamb.), black spruce ( Picea mariana [Mill.] B.S.P.), white pine ( Pinus strobus L.) and white spruce ( Picea glauca [Moench] Voss) plantations, 15 years after planting in Ontario, Canada. For all crop species, growth performance increased significantly with site preparation intensity on sites without brush control, but did not change on sites with brush control. The effect of brush control and site preparation on stand volume of crop trees varied among plantations while fertilization had no effect. For the jack pine plantation, stand volume of crop trees increased with brush control and site preparation intensity, while volume of non-crop trees did not differ among treatments. For the black spruce plantation, brush control increased and site preparation marginally affected stand volume of crop trees. However, brush control decreased non-crop tree hardwood volumes, resulting in a significant increase in total stand volume. In the white pine and white spruce plantations, stand volume of crop trees increased while that of non-crop trees declined, resulting in no difference in total stand volume. However, there was a significant shift of stand composition from hardwood dominated, mixed, to crop trees dominated with silvicultural intensity. Height structure changed with increasing silvicultural intensity for all plantations, showing a shift from a hardwood dominated multi-layer canopy (a canopy of two or more layers mixed of crop trees and non-crop trees) to a crop tree dominated canopy with an understory of naturally established shade-tolerant seedlings. We conclude that intensive silviculture is a useful tool for managing stand composition and structure of boreal and northern temperate plantations, but increases in total stand volume may not occur as expected.

Above- and belowground ecosystem biomass and carbon pools in an age-sequence of temperate pine plantation forests

We assessed the successional development of above- and belowground ecosystem biomass and carbon (C) pools in an age-sequence of four White pine ( Pinus strobus L.) plantation stands (2-, 15-, 30-, and 65-years-old) in Southern Ontario, Canada. Biomass and C stocks of above- and belowground live and dead tree biomass, understorey and forest ground vegetation, forest floor C (LFH-layer), and woody debris were determined from plot-level inventories and destructive tree sampling. Small root biomass (<5 mm) and mineral soil C stocks were estimated from soil cores. Aboveground tree biomass became the major ecosystem C pool with increasing age, reaching 0.5, 66, 92, and 176 t ha −1 in the 2-, 15-, 30-, and 65-year-old stands, respectively. Tree root biomass increased from 0.1 to 10, 18, 38 t ha −1 in the 2-, 15-, 30-, and 65-year-old stands, respectively, contributing considerably to the total ecosystem C in the three older stands. Forest floor C was 0.8, 7.5, 5.4, and 12.1 t C ha −1 in the 2-, 15-, 30-, and 65-year-old stands, respectively, indicating an increase during the first two decades, but no further age-effect during the later growth phase. Mineral soil C was age-independent with 37.2, 33.9, 39.1, and 36.7 t C ha −1 in the 2-, 15-, 30-, and 65-year-old stands, respectively. Aboveground ecosystem C increased with age from 3 to 40, 52, and 100 t C ha −1 in the 2-, 15-, 30-, and 65-year-old stands, respectively, due to an increase in aboveground tree biomass. Belowground ecosystem C remained similiar in the early decades after establishment with 37, 39, and 39 t C ha −1 in the 2-, 15-, and 30-year-old stands, but increased to 56 t C ha −1 in the 65-year-old stand due to an increase in root biomass. The difference in total ecosystem C between the 2- and 65-year-old stand was 116 t C ha −1. Our results highlight the importance of considering the successional development of forest ecosystem C pools, when estimating C sink potentials over their complete life cycle.

Growth Intercept Methods for Predicting Site Index in White Pine Plantations in the Glaciated Areas of Ohio

Abstract Growth intercept (GI) techniques were evaluated for estimating site quality in white pine stands planted on old-field sites in the Wisconsin-aged glaciated areas of northern and western Ohio. Correlations between growth of trees below the breast high (bh) annual growth increment andheight growth from bh and above were not statistically significant. Site index estimates were made using age at bh and height from the bh annual growth increment to the growing tip. Three-year and 5-year growth beginning 3 years above the bh annual increment and 10-year growth beginning oneinternode above bh were significantly more correlated with height than were intercepts beginning at bh. In multiple regression equations developed for predicting site index, 3-, 5- and 10-year intercepts, along with age at bh, accounted for 76, 77, and 80%, respectively, of the variationin tree heights and 35-year site indices varied from 60 to 83 ft. Combining clay content of the B2 soil horizon with GI and age increased the variation accounted for by 3-, 5-, and 10-year GI equations to 79, 78, and 81%, respectively, and the improvement in site index estimatesover those using GIs alone was not more than ±2 ft within any given GI measurement.

Molecular Epidemiology of White Pine Blister Rust: Recombination and Spatial Distribution

ABSTRACT Multilocus haplotypes (MLHs) were derived for the spermogonial (monokaryotic haploid) stage of Cronartium ribicola, the causal agent of white pine blister rust. Six random amplified polymorphic DNA loci and three single-strand conformational polymorphism markers were analyzed for 246 rust samples collected from two heavily infected white pine plantations. All cankers sampled were spatially located within the plantations. The hypothesis that spores are not locally disseminated was supported by the absence of any spatial clustering in the distribution of the MLHs. A large number of MLHs was found at both sites and the haplotypic diversity was close to the maximum (one) in both populations. All measures of recombination were not different from expectations under a scenario of sexual recombination. Genetic differentiation between the two sites was very low (theta = 0.023), yet it was significantly different from zero (P < 0.01). This analysis is in agreement with a scenario of extensive sexual recombination followed by some long-distance dispersal.

Net ecosystem production in a temperate pine plantation in southeastern Canada

Eddy covariance measurements of carbon dioxide (CO 2) and water vapour fluxes were made from June 2002 to May 2003 over a 65-year-old temperate conifer plantation forest in southern Ontario, Canada. This site is part of a newly initiated long-term tower flux measurement program over a chronosequence of white pine plantation forests, known as the Turkey Point Flux Station. Net ecosystem productivity (NEP) showed a strong dependence on environmental variables such as temperature, light regime, and vapour pressure deficit. In the summer, saturation water deficit exerted a strong control on photosynthetic uptake through decreased bulk surface conductance. There was a linear relationship between monthly carbon uptake and water loss. For each kilogram of water evaporated from the stand, approximately 2.15 g of carbon was sequestered. Annual NEP was 196 g C m −2 from June 2002 to May 2003. Annual gross ecosystem productivity (GEP) was 1442 g C m −2 and annual ecosystem respiration ( R) was 1247 g C m −2. A cross-site comparison of this site with 19 other, planted and natural, temperate conifer forests showed that NEP at the Turkey Point plantation was relatively low compared to other plantation forests of similar age group in Europe and North America. This analysis also showed that GEP and R of plantation forests was significantly higher than that of natural forests. In plantation forests, GEP and NEP linearly decreased with forest age, while R decreased little. Natural stands showed an increase in GEP and R with stand age, except for an old growth stand in western USA. This showed that photosynthesis, rather than respiration, plays a dominant role in net carbon uptake of both plantation and natural forests. In both, plantation and natural, stands there was a weak or no relationship between NEP and annual temperature and precipitation, while annual GEP and R was positively correlated to these environmental variables. The differences in carbon uptake among plantations and between plantation and natural temperate conifer forests were due more to physical and physiological differences among stands (e.g. stand age, tree density, leaf area index, site history, and adopted management practices in case of plantation forests), rather than differences in environmental variables.

Genet distribution of sporocarps and ectomycorrhizas of Suillus pictus in a Japanese white pine plantation

Summary • Spatial distribution and biomass of genets of sporocarps and ectomycorrhizas of Suillus pictus were studied in a plot of 20 × 24 m established in a Pinus pentaphylla var. himekomatsu plantation. • The biomass of S. pictus ectomycorrhizas was evaluated based on morphotypes, and genets were identified based on the inter-simple sequence repeat (ISSR) polymorphism analysis. • Suillus pictus was one of the dominant ectomycorrhizal fungal species in both the sporocarp and ectomycorrhizal communities in the study plot. Four genets were identified from sporocarps and these coincided with those identified from ectomycorrhizas. Sporocarps of each S. pictus genet occurred separately from those of other genets. Spatial distributions of ectomycorrhizas of each genet were wider than those of sporocarps. The largest genet occupied c. 54% of the plot, and the area of each genet differed considerably. • Vegetative growth of mycelia is assumed to play a more important role in the propagation of S. pictus than colonization from spores because expansions of all the four genets ranged from 25 to 30 m and no small genets were found in this plot.

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This work was motivated by previous pheromone trap tests for Conogrthes sp. and C. punctiferalis in which small numbers of Pleuroptia chloropahanta males were unexpectedly trapped. Formulations of (E)-10-hexadecenal (E10-16: Ald), (Z)-10-hexadecenal (Z10-16: Ald), n-hexadecanal (n-16: Ald) or (E)-10-hexadecenol (E10-16: OH) alone or in various combinations were tested as attractants for male moths of P. chloropahanta in different plantations. In chestnut and peach orchard field tests in 1994, E10-16: Ald alone was attractive to the males but binary mixtures of E10-16: Ald and 5 to 50% of Z10-16: Ald were not attractive. Trap catches by a binary mixture of E10-16: Ald and E10-16: OH in 1995 was very low and not different from that of a 4-component mixture for C. punctiferalis. In field tests of two Japanese white pine plantations of in 2001, 36 P. chloropahanta males were caught by traps baited with E10-16: Ald alone. Conclusive results, that is, exclusive attraction by E10-16: Ald were also obtained by field trap tests in plantations of Paulownia tomenyosa and Syrax abassia, host plants of this species. These results strongly suggest (E)-10-hexadecenal is effective as a sex attractant for monitoring P. chloropahanta and this compound may be one of the sex pheromone components of this species.

Growth of Eastern White Pine (Pinus strobus L.) Related to Forest Floor Consumption by Prescribed Fire in the Southern Appalachians

Abstract Chainsaw felling, burning, and planting of eastern white pine (Pinus strobusL.) have been prescribed on degraded pine/hardwood stands in the Southern Appalachians to improve overstory composition and productivity. The desired future condition of the overstory is a productive pine/hardwood mixture, with white pine, which is resistant to southern pine beetle (Dendroctonus frontalis), as the dominant pine. We evaluated the growth of white pine planted after fell-and-burn treatments through eight growing seasons after planting on three sites that differed in their fire characteristics and carbon and nitrogen losses. The three sites (JE, JW, and DD) differed in heat penetration and forest floor consumption. Although very little consumption of the Oe+Oa humus layer occurred during burning, consumption of the Oi litter layer was 94%, 94%, and 63% at JE, JW, and DD, respectively. Corresponding to the forest floor layer consumption (Oi and Oe+Oa combined), 46% of forest floor N was lost at JE, 45% of forest floor N was lost at JW, and less than 0.1% of the forest floor N was lost at DD. Biomass and density of woody competitor species were not significantly related to white pine size or growth. By the eighth growing season, no differences in white pine size or growth were detected between JE and JW, but DD had significantly smaller white pine trees. The size difference between DD and the other two sites was attributed to the replanting of seedlings at DD in 1992. However, relative growth rate (RGR) was significantly higher on DD in 1998 than the other two sites. Eight growing seasons after planting, white pine growth was negatively related to percent Oi layer consumed on the JE and JW sites. We also found significant relationships between white pine RGR and percent Oi consumed using data from all three sites. Although fire severity had a long-term effect on pine growth, fire severity was considered low overall on these sites because there were limited losses from the forest floor Oe+Oa layer. However, white pine increment and RGR were significantly related to percent forest floor Oi mass and N loss. This loss of site N capital could have a significant negative effect on growth of planted white pine over the long term. South. J. Appl. For. 26(1):18–25.

Understorey environment and vegetation response after partial cutting and site preparation in Pinus strobus L. stands

Understorey vegetation response to thinning, site preparation and underplanting was investigated in three natural, 110-year-old eastern white pine ( Pinus strobus L.) stands. The study was arranged in a split plot, randomized block design with four replicates, and included three thinning and four site preparation treatments. Early competition response, natural and planted white pine seedling growth and nutrient uptake were monitored. Light (PAR), soil moisture and temperature were assessed during the first two growing seasons. Environmental conditions varied with treatment. With increased thinning, overall the diversity of tree species decreased and shrub species increased, although this will change with time. PAR was the most crucial for successful seedling growth. At 50% PAR, seedling biomass of both natural and planted seedlings no longer appeared limited directly by light, and site preparation and brush control treatments resulted in further increased growth and improved seedling nutrition.

Surface burning in a mature stand of Pinus resinosa and Pinus strobus in Michigan: effects on understory vegetation

Beginning in 1991, periodic surface fires (frontal fire intensities &lt;200 kW m–1) were introduced into a mixed red pine (Pinus resinosa Ait.) and white pine (P. strobus L.) plantation (dbh 16–60 cm). Replicated plots of 0.4–0.5 ha were either burned three times at biennial intervals (early May of 1991, 1993, and 1995), burned once (early May 1991), or not burned. Measurements were conducted during the 1994 and 1995 growing seasons. The pine overstory was largely unaffected by the fires. The understory on unburned plots contained 16 111 large seedlings (&gt;1 m, ≤ 1.9 cm dbh) and 3944 saplings (2.0–5.9 cm dbh) per ha, consisting of 23 woody angiosperm taxa. Plots burned once contained 60% of the large seedlings, 7% of the saplings, and 6 fewer taxa than unburned plots. No large seedlings and few saplings were found in plots burned biennially. Cover of low (&lt;1 m) woody and herbaceous vegetation in plots burned once or three times was twice that of unburned plots, even in the growing season immediately following the May 1995 re-burn. Recovery of low vegetative cover in the re-burned plots was rapid, exceeding that in once-burned or unburned plots by late summer following the burn. Species richness of low vegetation was 20–25% higher in burned than unburned plots, except in the year immediately following reburning. Taxa dominating this site following burning were Sassafras albidum (Nutt.) Nees, Rubus spp., Phytolacca americana L., and Dryopteris spinulosa (O.F. MÜll.) Watt. Restoration of low-intensity surface fires to ecosystems dominated by mature red pine or white pine is feasible, but major changes in understory structure and composition will occur.

The Old Orchard White Pine Plantation at Biltmore

Abstract A pioneering case study in the Old Orchard Plantation on Biltmore Estate near Asheville, North Carolina, considered current yields and the effects of periodic thinning on height and basal area growth, as well as cubic volume and board-foot yields. Established in 1899, one of three plots of this eastern white pine stand was first thinned in 1916. Beyond providing growth-and-yield data, the Old Orchard Plantation demonstrates the value of maintaining permanent forest research plots for long-term ecological and silvicultural studies.

Nutrient availability and regeneration response after partial cutting and site preparation in eastern white pine

A 27-ha field experiment was set-up to study the effects of thinning, site preparation and underplanting in three 110-year-old natural eastern white pine ( Pinus strobus L.) stands using a four replicate, randomized block design. Three thinning and four site preparation treatments were applied. White pine seedlings were underplanted in sub-plots. Three years after treatment, a sample of natural and planted white pine seedlings was harvested to characterize growth and nutrient uptake. Ion exchange resin bags were used to assess soil nutrient availability. Light (PAR), soil moisture and soil temperature were assessed throughout the growing season. Nutrient availability was lower in the third as compared to the second growing season after treatment. Generally, environmental conditions improved and nutrient uptake and seedling growth increased after the silvicultural treatments were applied. Early white pine seedling growth was greatest following thinning of the overstory to a two-crown spacing, together with scarification and brush control.

Use of Vegetational Characteristics and Browsing Patterns to Predict Deer Damage in Eastern White Pine (Pinus strobus) Plantations

Abstract Browsing of seedlings by white-tailed deer (Odocoileus virginianus) can make natural and artificial forest regeneration difficult. Few mathematical models predict deer browsing within and between sites, giving managers only landscape-level characteristics, such as deer population levels and yearly snowfall measurements, to determine where deer-protective measures should be installed. This study described browsing patterns and assessed influence of vegetational characteristics on browsing. Predictive models were developed using overstory and understory measurements, and browsing reconstructions of individual seedlings within eight eastern white pine (Pinus strobus) plantations in northern Minnesota. Results indicated that deer concentrate browsing on terminal leaders in shorter seedlings, shifting to laterals as seedlings approach browsing height limits (140 cm).Damage models were site-specific. The vertical and horizontal distribution of understory vegetation and the presence of alternative food sources influenced the probability of browsing. Future models should incorporate these measures as well as browse selection patterns, landscape-level characteristics,and past deer activity. North. J. Appl. For. 16(2):96-102.

Fine-Level Genetic Structure of White Pine Blister Rust Populations

ABSTRACT The fine-level genetic structure of the white pine blister rust agent, Cronartium ribicola, was investigated by sampling multiple monokaryotic spermogonia directly on cankers in four eastern Canadian white pine (Pinus strobus) plantations and assessing genetic variability, using random amplified polymorphic DNA (RAPD) markers. Ninety-eight percent of the cankers surveyed contained a single DNA haplotype, suggesting spermogonia within cankers are the result of clonal reproduction. A single canker contained two haplotypes that were divided between the upper and lower parts of the canker, suggesting it represented two confluent cankers. In contrast, genotypic diversity was high among cankers. Thirty-seven haplotypes were found among forty-three cankers sampled, and an analysis of molecular variance indicated that 93% (P < 0.001) of the total genetic diversity was attributable to sampling of different cankers, strongly suggesting that multiple infections do not take place in the white pine blister rust pathosystem, i.e., a canker is the result of infection by a single genotype. This result is in contrast with the high level of genetic diversity previously reported among dikaryotic aecidia within cankers and is consistent with the hypothesis that variability in the aecidial stage is the result of outcrossing between resident spermogonia and alien spermatia. The genetic structure of the spermogonial stage, which is the vegetative extension of infection by basidiospores and, therefore, the indirect result of meiosis, was consistent with random mating; the observed genotypic diversity was not significantly different (P > 0.05) from the genotypic diversity expected under the assumption of panmixis. The results indicate that monokaryotic cankers can be genotyped by sampling a single unopened spermogonia per canker.

Factors influencing amphibian and small mammal assemblages in central Appalachian forests

We studied terrestrial amphibian and small mammal assemblages with drift fences and pitfall traps in five forested stands during 1987–1988 on Shenandoah Mountain in the George Washington National Forest, Virginia, USA. Eleven species of salamanders, five frogs, five shrews, and seven rodents were monitored. Amphibians were significantly more abundant in forest stands consisting of mature hardwoods than in a recent clearcut and a white pine plantation. Although there was considerable variation in abundance among species in the five stands, small mammal abundance was high in all five habitats studied. Amphibian species diversity (Shannon Index) was less than half that for small mammals because red-backed salamanders ( Plethodon cinereus) were dominant in most assemblages. Amphibian and small mammal diversity and total species richness were not related to estimated stand age, total number of canopy trees, tree diversity, or frequency of underground rocks. Maintenance of amphibian biodiversity requires the combination of mature hardwoods and wetland habitats (e.g. wildlife ponds and seepages). Most of the small mammals encountered were habitat generalists. Management focus on mature hardwood forests would maintain populations of small mammals requiring cool, moist situations in upper-elevation habitats in the central Appalachian Mountains.

Forest Management Effects on Surface Soil Carbon and Nitrogen

AbstractChanges in surface soil C and N can result from forest management practices and may provide an index of impacts on long‐term site productivity. Soil C and N were measured over time for five watersheds in the southern Appalachians: two aggrading hardwood forests, one south‐ and one north‐facing, undisturbed since the 1920s; a white pine (Pinus strobus L.) plantation planted in 1956; and two regenerating hardwood forests, a whole‐tree harvest in 1980, and a commercial sawlog harvest in 1977. Soils on harvested watersheds were sampled before and for ≈15 yr after harvest. Surface soil C concentration on the undisturbed watersheds varied significantly among sample years. Concentrations fluctuated on the south‐facing and decreased on the north‐facing watershed. The pattern for total N was similar. Total N decreased significantly on the north‐facing but was stable on the south‐facing watershed. In the white pine plantation, C increased while N concentrations decreased during the 20‐yr period. Soil C and N concentrations generally declined the first year following whole‐tree harvest. Fourteen years after cutting, C remained stable, while N was greater compared with reference watershed soils. The commercial sawlog harvest resulted in large increases in surface soil C and N concentrations immediately after cutting. Carbon levels remained elevated 17 yr following cutting. Our data suggest that the forest management practices examined do not result in long‐term decreases in soil C and N. However, the high interannual variation on all watersheds suggests that care must be taken in selecting control sites to determine long‐term treatment impacts.

Response of Planted Eastern White Pine (Pinus strobus L.) to Mechanical Release, Competition, and Drought in the Southern Appalachians

Abstract Conversion of low-quality, natural mixed pine/hardwood ecosystems, containing a mountain laurel (Kalmia latifolia L.) dominated understory, to more productive eastern white pine (Pinus strobus L.)/mixed-hardwood systems is a common prescription on relatively xeric southern Appalachian forest sites. We examined the effects of mechanical release, interspecific competition, and annual precipitation on growth of planted white pine in four 14-yr-old stands in the southern Appalachians. Two stands were mechanically released at age 6. No significant differences in biomass, basal area, or diameter were found between treatments for all species combined. Radial increment was significantly less during a drought year for both treatments. Height increment was less sensitive to severe moisture limitation than radial increment. Height and radial increment were compared to distance-dependent and distance-independent measures of competition for the nonreleased stands. Indices based on height and height/distance explained the greatest amount of variation in both radial and height increment. The influence of post-release severe drought may have delayed or diminished the response to release. The competitive influence of understory dominant mountain laurel at stand age 14 appears to be slight compared to the influence of other competing hardwood vegetation. South. J. Appl. For. 21(1):19-23.