Rigida Mill Research Articles

Pitch pine ( Pinus rigida Mill.) invasion of Cape Cod pond shores alters abiotic environment and inhibits indigenous herbaceous species

Invasion by pitch pine ( Pinus rigida Mill.) on coastal plain pond shores may have direct impacts on the herbaceous community, or may merely indicate changes in hydroperiod, which are the actual cause of community change. We compared abiotic conditions and community composition of sites that had been invaded by P. rigida and those that had not on two Cape Cod ponds. Soil under living pines had lower pH and water content, reduced net nitrification, and increased rates of ammonification. Dense stands of pine saplings reduced PAR penetrance by 94% and excluded virtually all herbaceous species. To determine if pines alone can change community composition, we imposed artificial shade and added pine needle litter to experimental plots. In the course of one growing season, both litter and shade significantly reduced the frequency of herbs in the herbaceous zone of the pond shore. Litter had the greater effect (significant for six of seven taxa), while shade reduced the frequencies of three taxa significantly.

Contrasting modes of survival by jack and pitch pine at a common range limit

Freezing tolerance, reproductive development, and seed germination of jack pine (Pinus banksiana Lamb.) and pitch pine (Pinus rigida Mill.) were compared in a small sympatric population in Acadia National Park in Maine, at the southern range limit of the former and the northern limit of the latter. Freezing tolerances of vegetative shoots and roots were similar for both species. Both species flower prolifically, and there was no evidence of differences in either pollen viability, cone survival, or proportion of viable seed (65–70% of the total). Regeneration success (established seedlings ranging from 1 to 13 years old) was similar overall for both species, but success by species varied greatly in some years. Jack pine regeneration was significantly associated with thinner soils, while pitch pine regeneration was associated with thicker soils in hollows. Jack pine seed germinated significantly faster than pitch pine seed, especially when day–night temperature was reduced. Pitch pine seedlings always exhibited a significantly higher shoot/root ratio than those of jack pine. The most northerly provenances of jack pine germinated significantly faster than those from the most southerly provenances. Jack pine also germinated at a significantly higher percentage than pitch pine in exposed granite sand. Thus relatively cool, dry conditions may favor establishment of jack pine seedlings, while pitch pine establishment may be favored in warmer, wetter conditions.

NEW DISTRIBUTION RECORD FOR ELATOPHILUS INIMICUS (HEMIPTERA: ANTHOCORIDAE)

Of the 18 Holarctic species in the genus Elatophilus, only 8 species are reported from North America (Lattin & Stanton 1993). The anthocorid Elatophilus inimicus was originally described by Drake and Harris (1926), from a single specimen collected in New York who placed the species in the genus Xenotracheliella. The species was subsequently transferred to the genus Elatophilus by Kelton and Anderson (1962), and was later documented to feed on species of scale insects in the genus Matsucoccus that inhabit only species of pine (Doane 1965, Lattin & Stanton 1992, Lussier 1965, and Mendel et al. 1991). This predator has been recorded previously only from Canada, and a few northeastern, midwestern, and coastal states (CO, MI, NC, and NY) feeding onM. resinosae Bean and Godwin. Recorded plant hosts for the prey of this predator include red pine (Pinus resinosa Ait.), pitch pine (P. rigida Mill.), and Scots pine (P. sylvestris L.), while additional prey suggested include mites, adelgids, and aphids (Lussier 1965). The only other species described from the eastern U.S. is E. pinophilus Blatchley described from pine in Florida (Blatchley 1928). A study was initiated in May 1999 to identify the potential native predators attracted to the sex pheromones of the scale insects M. feytaudi Ducasse, M. josephi Bodenheimer and Harpaz, and M. matsumurae Kuwana in eastern Tennessee. Delta style sticky traps (n = 60) baited with sex pheromones were placed in five pine sites established along an elevational gradient in the Great Smoky Mountains National Park in Sevier Co, TN. Pine site 1 (390 5771N, 28

Effect of water stress on aluminum toxicity in pitch pine seedlings

A decrease in soil water content during droughts may increase aluminum (Al) to concentrations that are toxic to the growth of trees. The effects of water stress (WS) on the response of ectomycorrhizal pitch pine (Pinus rigida Mill.) seedlings to aluminum was determined by growing seedlings in sand irrigated with nutrient solution (pH 3.8) containing 0, 5, or 10 mg L‐1 Al. Water stress was imposed for 41 days by withholding nutrient solution for five consecutive days each week. At harvest time, seedlings at high WS had 72% of mean gravimetric water contents of seedlings at low WS. Aluminum decreased growth of seedlings at high WS, but had no effect on growth of seedlings at low WS. Aluminum toxicity symptoms in roots (e.g., dark thickened tips) were observed at lower Al levels at high WS than at low WS. Stem dry weight was the only plant part decreased by water stress alone. Across Al levels, Al concentration in roots was higher at low WS than at high WS. Water stress alone reduced root [phosphorus (P), potassium (K), and calcium (Ca)] and foliar [P, K, and magnesium (Mg)] concentrations of mineral nutrients. Decreases of nutrients in roots with increasing Al was greater at low than at high WS. Calcium was the only foliar nutrient decreased by Al treatment.

Nitrogen and phosphorus dynamics in foliage and twig of pitch pine and Japanese larch plantations in relation to fertilization

Seasonal foliage and twig nitrogen (N) and phosphorus (P) dynamics were determined for 40‐year‐old pitch pine (Pinus rigida Mill.) and Japanese larch (Larix leptolepis Gord.) plantations established on similar soils in central Korea. Also, the effects of three levels of N plus P fertilizers on N and P retranslocation were evaluated. In general, Japanese larch had significantly higher current foliage N and P concentrations than pitch pine, and N and P concentrations were higher in foliage than those in twigs for both study species. Foliage N and P concentrations were highest in mid‐growing season and lowest in autumn whereas twig N and P concentrations increased during foliage senescence, suggesting that twig served as a storage tissue. We did not find differences in foliage N and P retranslocation between pitch pine and Japanese larch; current foliage N and P retranslocation of the control trees were 35% and 56% for pitch pine, and 39% and 59% for Japanese larch, respectively. There were no consistent patterns in foliage and twig N and P retranslocation following fertilization.

Changes in radial increment of host and nonhost tree species with gypsy moth defoliation

Ring widths from 1458 trees from Massachusetts, New York, and New Jersey were measured to determine the influence of gypsy moth (Lymantria dispar L.) defoliation on both hosts (primarily oaks (Quercus spp.)) and nonhosts. Previous year's defoliation negatively influenced radial increment in all oak species. Defoliation also negatively affected radial growth of pitch pine (Pinus rigida Mill.), an intermediate host. There was little or no effect of defoliation on increment of trembling aspen (Populus tremuloides Michx.) and bigtooth aspen (Populus grandidentata Michx.), but both are preferred hosts. Defoliation of host trees in mixed stands resulted in increased increment in the nonhosts tulip-tree (Liriodendron tulipifera L.) and ash (Fraxinus spp.) in the year following defoliation. The effect of defoliation was also evident in the relative production of earlywood and latewood with a pronounced dominance of earlywood production in host trees during the same year as defoliation and often in the following year.

Ice Storm Damage to Forest Tree Species in the Ridge and Valley Region of Southwestern Virginia

WARRILLOW, M. AND P. Mou. (Department of Forestry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061). Ice storm damage to forest tree species in the ridge and valley region of southwestern Virginia. J. Torrey Bot. Soc. 126:147-158. 1999.-Ice damage to canopy trees was surveyed after a major ice storm on Virginia Tech's Fishburn Forest in the central Appalachian Mountain region. The survey site was stratified according to aspect, slope, and slope position, and sample plots were randomly chosen within each topographic category. In general, Virginia pine (Pinus virginiana Mill.) and pitch pine (P. rigida Mill.) were the most damaged, and blackgum (Nyssa sylvatica Marsh.) was the most resistant species. Although yellow buckeye (Aesculus octandra Marsh.) and yellow poplar (Liriodendron tulipifera L.) were basically undamaged, they were restricted to the topographic areas where ice damage was generally less severe. Within a species, susceptibility varied according to topographic features. In general, the greatest damage occurred on steep slopes and eastern aspects, and the least damage occurred on toeslopes (foothill and valley bottom). Some species, such as red maple, varied greatly in their susceptibility to ice damage between topographic categories, while others, like blackgum, varied little. Dominant canopy individuals generally had less damage than co-dominant and intermediate individuals. These results suggest that damage by ice storms is patchy at local scales, and that the distribution of damage may be predictable.

Effect of nitrogen source on aluminum toxicity in nonmycorrhizal and ectomycorrhizal pitch pine seedling

The effect of elevated nitrate [(NO3‐nitrogen (N)] or ammonium (NH4)‐N on the response of nonmycorrhizal (NM) and ectomycorrhizal (ECM) pitch pine (Pintis rigida Mill.) seedlings to aluminum (Al) was determined in experiments in which N was increased three times above ambient levels. Seedlings with and without the mycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch were grown in sand irrigated with nutrient solution (pH 3.8) containing 0, 10, or 20 mg Al L‐1 (0, 370, or 740 μM Al). The nutrient solution simulated that for the sandy, nutrient‐poor soil of the New Jersey Pine Barrens. Elevated NO3‐N had no significant effect on Al toxicity in NM seedlings, but Al toxicity at ambient NH4‐N was ameliorated by elevated NH4‐N. Symptoms of Al toxicity in roots (thick and stunted) of ECM seedlings at ambient N levels were reduced by elevated NH4‐N and absent at elevated NO3‐N. When N was elevated by an increase in NO3‐N or NH4‐N, uptake of N and relative increases in total biomass were greater in ECM than in NM seedlings.

RAPID N2FIXATION IN PINES? RESULTS OF A MAINE FIELD STUDY

A recent study of the nitrogen budgets of pitch pines (Pinus rigida Mill.) and red pines (P. resinosa Ait.) growing in model ecosystems in New Hampshire (USA) reported very high nitrogen gains. Thus N2 fixation associated with the rhizosphere of pines may contribute to their success in nitrogen-limited ecosystems. We used the acetylene-reduction assay with carbon monoxide controls to determine whether high rates of N2 fixation are associated with pine forests in Maine. We measured nitrogenase activity in cores of the forest floor and the mineral soil beneath for five pitch pine, seven red pine, and six eastern white pine (P. strobus L.) stands. The stands represented 8 of the 15 biophysical regions of Maine (USA) and included a variety of age classes. We found only very low rates of nitrogenase activity, which varied seasonally with the highest values during the warmer months. The highest mean nitrogenase activity observed was 449 nmol C2H4·m−2·h−1. We estimated that <6 mg N/m2 was fixed annually by non-symbiotic diazotrophs in the soil horizons sampled. These rates are much smaller than atmospheric N inputs in Maine (300–450 mg N·m−2·yr−1) and consequently have little impact on the N budgets of the pines. Based on our results and the literature, it is likely that only low rates of N2 fixation are associated with pines.

Effects of carbon dioxide enrichment on response of mycorrhizal pitch pine (Pinus rigida) to aluminum: growth and mineral nutrition

Carbon dioxide enrichment may increase the Al tolerance of trees by increasing root growth, root exudation and/or mycorrhizal colonization. The effect of elevated CO2 on the response of mycorrhizal pitch pine (Pinus rigida Mill.) seedlings to Al was determined in two experiments with different levels of nutrients, 0.1- or 0.2-strength Clark solution. During each experiment, seedlings inoculated with the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch were grown 13 weeks in sand irrigated with nutrient solution (pH 3.8) containing 0, 6.25, 12.5, or 25 mg/l Al (0, 232, 463, or 927 μM Al) in growth chambers fumigated with 350 (ambient) or 700 (elevated) μl/l CO2. At ambient CO2, in the absence of Al, mean total dry weights (DW) of seedlings at the high nutrient level were 164% higher than those at the low level. Total DW at elevated CO2, in the absence of Al, was significantly greater than that in ambient CO2 at the low (+34%) and high (+16%) nutrient levels. Root and shoot DW at both nutrient levels decreased with increasing Al concentrations with Al reducing root growth more than shoot growth. Although visible symptoms of Al toxicity in roots and needles were reduced by CO2 enrichment, there were no significant CO2 × Al interactions for shoot or root DW. The percentage of seedling roots that became mycorrhizal was negatively related to nutrient level and was greater at elevated than at ambient CO2 levels. Generally, elevated CO2 had little effect on concentration of mineral nutrients in roots and needles. Aluminum reduced concentrations of most nutrients by inhibiting uptake.

Relating land-use history and climate to the dendroecology of a 326-year-old Quercus prinus talus slope forest

Dendroecology and land-use history were used to investigate the ecological history of a 326-year-old Quercus prinus L. forest. Quercus prinus, Castanea dentata (Marsh.) Borkh., and Pinus rigida Mill. dominated this talus slope prior to European settlement based on witness tree records. Oak species have exhibited continuous recruitment over three centuries probably in response to periodic fire and wind disturbances. While the stand escaped the direct impacts of timber cutting and the charcoal iron industry, the indirect effects of these land-use practices increased growth and recruitment. Different criteria were used for understory versus overstory trees to improve our detection of growth releases. Overall, major disturbances occurred approximately every 40 and 31 years before and after European settlement, respectively. This century, old-growth Q. prinus experienced marked growth increases coupled with high recruitment following the introduction of the chestnut blight (Cryphonectria parasitica (Murr.) Barr.) to the stand in 1909. Tree growth was also highly correlated with temperature and Palmer drought severity indices between 1895 and 1995. Climatic fluctuations in the 1820s-1830s and 1920s reduced radial growth and recruitment resulting in stem exclusion stages following regeneration pulses. Relating land-use history and climatic data to the dendroecology of this forest improved our understanding of its historical development.

On the Nature of Environmental Gradients: Temporal and Spatial Variability of Soils and Vegetation in the New Jersey Pinelands

1 Environmental variability can occur over various spatial scales, ranging from small patches at the scale of individual plants to long gradients over hundreds of metres. 2 In the New Jersey Pinelands, different species in the diverse shrub understorey of pitch pine (Pinus rigida Mill.) forests are patterned at these various scales. 3 Soil moisture, extractable NH4-N and N mineralization rate vary in complex ways, with the scale of spatial patterning changing over time and with depth in the soil profile. Moisture in both mineral and organic horizons, and NH4-N in the organic horizon, have patterns that are more stable over time than the mineralization rate in either horizon, or the NH4-N concentrations in the mineral horizon. 4 Vegetation patterns, as captured in principal components analysis, were poorly explained by any of the soil properties. Only the more temporally stable properties showed any relationship with vegetation patterns. 5 These results suggest that environmental gradients reflect patterns of environmental variation in four dimensions. Variation in the vertical dimension and over time is as pronounced and important as variation in the horizontal dimensions. 6 Many methods used to analyse vegetation implicitly assume temporal and spatial stability of environmental properties. Our results suggest that a more complex, fourdimensional assessment of environmental variation should be incorporated into models of vegetation-environment relationships.

LIVE AND DEAD ROOTS IN FOREST SOIL HORIZONS:CONTRASTING EFFECTS ON NITROGEN DYNAMICS

Roots are widely acknowledged to be major contributors to ecosystem nutrient cycles. However, live roots may have very different effects than dead roots, the quality of the soil surrounding the roots may itself affect the influence of the roots, and the nature of the soil profile may modify all of these interactions. We have used experimental, field-based mesocosms to dissect the differing effects of live and dead roots in organic and mineral horizons of spodosolic forest soils. Mesocosms were constructed in a simple ecosystem dominated by pitch pine (Pinus rigida Mill.) and blueberry (Vaccinium corymbosum L.) in the New Jersey Pinelands. They contained 5 cm deep surface horizons of either organic matter or an inert substitute (vermiculite), placed above 10 cm of mineral material from the E horizon, with defined amounts of live or dead roots added. Sampling was conducted over a 2-yr period. In mineral soil, live roots stimulated ammonification rates but had little effect on extractable N, and the stimulation occurred only if an organic surface horizon was present. In contrast, live roots in organic material reduced both ammonification rates and extractable N. Dead roots increased extractable N in the mineral material, but not the organic material. The presence or absence of an organic horizon had a dominating effect on all aspects of nitrogen dynamics in the mineral soil; not only extractable inorganic N, but also transformation rates, were higher in soils under organic matter. The results showed that the effects of roots on soil nutrients depended on (1) the ratio of live to dead root biomass, (2) the quality of the soil material in which the roots occurred, and (3) the structure of the soil profile. These findings necessitate a revision of the concept of “rhizosphere effect” in forest soils.

Phosphate-limitation physiology in ectomycorrhizal pitch pine (Pinus rigida) seedlings.

Foliar and root P concentrations, net H(2)PO(4) (-) (P(i)) uptake rates, and root surface acid phosphatase (APase) rates were assessed in pitch pine (Pinus rigida Mill.) seedlings inoculated with the ectomycorrhizal fungi Laccaria bicolor (Maire) Pat., Paxillus involutus (Batsch.) Fr., or Pisolithus tinctorius (Pers.) Coker and Couch, and grown at 10 or 100 micro M P(i) in sand culture. Following a 6-week period of acclimation to the P(i) regimes, seedlings grown at 100 micro M P(i) had greater foliar and root P concentrations than seedlings grown at 10 micro M P(i). Mycorrhizal colonization increased the concentration of P in roots and, under P(i)-limiting conditions, this retention was at the expense of P translocation to foliage. There were no differences in P(i) uptake rates between non-mycorrhizal and mycorrhizal roots grown at 100 micro M P(i). However, mycorrhizal colonization enhanced P(i) uptake in seedlings grown at 10 micro M P(i), with rates 1.3-, 2.6-, and 3.3-fold greater in roots colonized with L. bicolor, P. involutus, and P. tinctorius, respectively, than in non-mycorrhizal roots. Root acid phosphatase (APase) activity was greater in non-mycorrhizal roots than in roots colonized with any of the three mycorrhizal fungi, and increases in activity in response to P(i) limitation occurred only in non-mycorrhizal roots. These results highlight the importance of seedling acclimation to prevailing P(i) availability and the role of mycorrhizal fungi in altering the allocation of P between roots and shoots. The activities of the APase systems of the mycorrhizal species tested do not support the hypothesis that this enzyme system plays an important role in P(i) acquisition under P-limiting conditions.

Pitch Pine (Pinus rigida Mill.) Communities in the Hudson Valley Region of New York

This study is part of a coordinated series to describe the pine barrens of New York, communities characteristic of disturbed sites with poor soils. Pitch pine (Pinus rigida Mill.) communities in the Hudson Valley region of New York were found on a sand dune, alluvium, a lacustrine delta and on conglomerate and sandstone outcrops. The alluvium and lacustrine delta sites supported more mesic communities with higher tree and herb species richness than the sand dune site, but lacked a shrub layer. The sand dune, sandstone outcrop and conglomerate sites supported open tree canopy communities in which ericaceous shrubs, especially Gaylussacia baccata, dominated a distinct shrub layer. Community types could be classified into three physiognomic forms. Probably the most disturbed were communities of dwarf vegetation dominated by either pitch pine or scrub oak (Quercus iliczfolia). A second type was characterized by an open canopy of short pitch pines with an extensive shrub layer of scrub oaks or ericaceous shrubs. The third type had a closed canopy of tall pitch pine, red maple (Acer rubrum), red oak (Q. rubra) and/or white oak (Q alba), few shrubs but a considerable number of forest floor herbaceous species. The southeastern area is of particular interest because two of the best known pine barrens in New York, the Albany Pine Bush and the Schawangunk Mountains dwarf forest are lo- cated there. The Pine Bush has been the subject of a number of publications, most ad- dressed to a general audience (Rittner, 1975, for example), but Milne (1985) made a de- tailed study of upland forests and their successional development. He suggested that areas dominated by scrub oak (Quercus ilicifolia) with scattered pitch pine were characteristic of very disturbed sites, especially those that burned often. In the absence of disturbance, Milne believed they would succeed to closed-canopy pitch pine forests, then to areas dominated by a mixture of pitch pine, white pine (Pinus strobus), red oak (Quercus rubra), white oak (Q alba), red maple (Acer rubrum) and white ash (Fraxinus americana). Schawangunk Mountain ridge vegetation was described by McIntosh (1959), who noted that bare rock surfaces of the ridges were covered with pitch pine, sometimes dwarfed, no more than 1-3 m tall. These dwarf ridge top communities graded into taller pitch pine and

Pitch Pine (Pinus rigida Mill.) Communities in Northeastern New York State

-Pitch pine (Pinus rigida Mill.) is found in communities scattered around the edges of the Adirondack Mountains. These communities occur on rock pavement of granitic gneiss or sandstone in the Jefferson County region or deep sands in Oneida, Saratoga, Clinton, Essex, Warren, Schenectady and Albany counties. Detrended correspondence analysis (DCA) of the vegetation in 83, 10 X 10-m plots at 13 sites showed that species composition at each site was distinct. The first DCA axis was significantly correlated with soil extract specific conductance, percent very coarse sand, tree age, percent of oaks in the canopy and percent of heaths in the herb and shrub layers. The second axis was significantly correlated with tree height, species richness, soil pH, specific conductance and percent coarse sand. Two-way indicator species analysis (TWINSPAN) separated communities on rock from those on.sand. Communities on sand were classified according to the extent of ericaceous shrub cover, dominance of oaks and/or white pine in the canopy, and the degree of mesophytism of the community.

Above- and Below-Ground Characteristics of Persistent Forest Openings in the New Jersey Pinelands

EHRENFELD, JOAN G., WEIXING ZHU AND WILLIAM F. J. PARSONS. (IMCS, Rutgers University, New Brunswick, NJ 08903). Above- and below-ground characteristics of persistent forest openings in the New Jersey Pinelands. Bull. Torrey Bot. Club. 122:298-305. 1995.-Openings in the pitch pine (Pinus rigida Mill.) forests of southern New Jersey may persist for decades. In five such openings, ranging in size from 22 to 223 m2, and their surrounding forest matrix, we characterized the vegetation, the forest floor, root biomass, soil chemistry and soil fungi. There was a much greater disparity between the openings and the forest matrix in the density of small ericad shrubs than in the number or basal area of the canopy trees, and this disparity was mirrored in the thickness of the litter and organic horizons, and in the total small root biomass. The matrix:gap ratios of total root biomass and of total soil fungal length were similar to the ratios for tree and large shrub densities. Extractable NH4-N, BrayP, pH, and soil moisture did not differ between the openings and matrix, but extractable N03-N was higher in the openings than the intact forest. We suggest that the shrubs may be an important factor in maintaining the differences between the openings and the matrix, by trapping litter, maintaining high root biomasses, and inhibiting decomposition. If the organic horizon is destroyed in a locally intense disturbance, the slow rate of invasion and growth of the shrubs into mineral soil may help perpetuate the opening for long periods of time.

Growth and nutrition of nonmycorrhizal and mycorrhizal pitch pine (Pinus rigida) seedlings under phosphorus limitation.

The association of ectomycorrhizal fungi with tree roots enhances the acquisition of phosphorus (P) from the soil. In addition to increasing the uptake of H(2)PO(4) (-) (P(i)), mycorrhizal fungi may increase the spectrum of P sources utilized by tree roots by mediating the dissolution of insoluble metallophosphate salts or the hydrolysis of organic P compounds. To investigate the role of ectomycorrhizal fungi in enhancing P acquisition by tree roots, pitch pine (Pinus rigida Mill.) seedlings were grown in sand culture with or without the ectomycorrhizal symbiont Pisolithus tinctorius Coker and Couch under various conditions of P limitation. Compared with nonmycorrhizal seedlings, seedlings inoculated with P. tinctorius exhibited a greater capacity to function under P limitation as evidenced by superior growth and the maintenance of normal foliar ion composition at low P(i) concentrations. Nonmycorrhizal seedlings subjected to P-limiting conditions exhibited depressed K and P and elevated Na concentrations in foliage. The association of P. tinctorius with pitch pine seedling roots maintained foliar K concentrations and prevented the accumulation of Na under P limitation. Nonmycorrhizal seedlings were unable to obtain P from either solid AlPO(4) or inositol hexaphosphate (IHP), whereas seedlings inoculated with P. tinctorius utilized AlPO(4), but not IHP as a P source. Root surface acid phosphatase (APase) activity was depressed in roots infected with the mycorrhizal symbiont and was negatively correlated with seedling growth on all P sources. Root APase activity was negatively correlated with foliar P concentrations in seedlings grown on P(i), but was not correlated with foliar P concentrations in seedlings cultured with AlPO(4) or IHP.

Temporal variation in foliar nutrient concentrations of pitch pine, loblolly pine and the pitch X loblolly hybrid

Although loblolly pine nutrition is well documented, there is little information available on the nutrition of the pitch X loblolly hybrid. The purpose of this study was to characterize the temporal variation of fascicle characteristics and foliar nutrient concentrations of the pitch X loblolly hybrid and compare this variation to that of its parent species, particularly loblolly pine ( Pinus taeda L.). The study was located on the Piedmont physiographic province of Virginia. Two plantations, Plantation 1 containing full-sib, F1 trees and Plantation 2 containing half-sib, F2 trees, were established. Five pitch X loblolly hybrid families, two pitch pine ( Pinus rigida Mill.) families, and one loblolly pine ( Pinus taeda L.) family were selected from Plantation 1. Five hybrids, one pitch pine family, and four loblolly pine families were selected from Plantation 2. Foliage was sampled monthly from December 1988 through December 1989, and analyzed for total N, P, K, Ca and Mg. Fascicle length, fascicle weight and foliar nutrient data were analyzed. The hybrids generally had fascicle characteristics intermediate to those of the parent species. Collectively, the various crosses of the hybrid had foliar nutrient characteristics intermediate between the parent species, with few hybrid nutrient concentrations being significantly different from those of loblolly pine. Loblolly pine critical nutrient concentrations are adequate for diagnosing the nutritional status of most of the hybrid families. Some individual hybrid families may not nutritionally emulate loblolly pine and may require the use of individualized critical nutrient concentrations. Hybrid foliage should possibly be sampled in mid-summer to obtain maximum sensitivity to site or treatment difference, and in October through December for routine nutrient diagnoses.

Wildfire Effects on Forest Floor and Surface Soil in a Table Mountain Pine-Pitch Pine Forest

Wildfire plays a dominant role in creating die environmental and biological conditions necessary for the natural regeneration of mixed Pinus pungens Lamb. (Table Mountain pine)-Pinus rigida Mill. (pitch pine) forests. This study of forest floor and surface soil properties following a mid-July wildfire in these forests in the Shenandoah National Park revealed significant reductions in nutrient contents. Prolific regeneration of the pines occurred following the fire, with over 9,000 seedling/ha tallied in high severity areas, compared with less than 800 seedlings/ha in unburned areas. It is hypothesized that fire degrades site quality and sets back the site succession process so that the pines are better able to compete with invasive, xeric-site deciduous species like oaks and maples. Adjacent, unburned xeric-site oak forests dominate on more moist and fertile sites.