Ralph S. Meldahl

Effects of ozone and simulated acidic precipitation on ectomycorrhizal formation on loblolly pine seedlings

Abstract Since air pollutants have been postulated to alter rhizosphere ecology, a study was initiated to evaluate the impact of O 3 and acidic precipitation on ectomycorrhizal formation on loblolly ( Pinus taeda L.) seedlings. Six-month-old loblolly pine from two families differing in O 3 sensitivity were exposed to four O 3 concentrations (charcoal-filtered air, non-filtered, non-filtered × 1.7, or non-filtered × 2.5) and three levels of rainfall acidity (pH = 3.3, 4.3, 5.3) in modified open-top chambers for one growing season. Seedlings were planted in root exclusion tubes designed to isolate individual root systems. Roots were evaluated for the presence or absence of ectomycorrhizal short roots. Ectomycorrhizae were quantified as numbers of morphotypes or morphotype tips per centimeter-long root. Total number of morphotypes per centimeter-long root increased with increasing O 3 concentration in the O 3 -sensitive family. Elevated O 3 caused a shift in some individual morphotypes in both families. Total number of morphotypes decreased with increasing rainfall acidity in the O 3 -sensitive family, but was not altered in the other family. The responses observed in this study are probably related to changes in host metabolism and/or shifts in individual morphotypes.

The characterization and comparison of ozone exposure indices used in assessing the response of loblolly pine to ozone

Abstract Using the 1988 and 1989 experimental results obtained for two loblolly pine half-sibling families (GAKR 15–23 and GAKR 15–91) at the Auburn University intensive field research site, we: (1) explored the performance of a set of exposure indices; (2) characterized the ambient air and charcoal-filtered air treatments at Auburn and compared the values of the O3 exposure indices with those values calculated for ambient O3 monitors for a select set of sites; (3) identified and characterized O3 treatments in the Auburn open-top exposure chambers where an adverse effect was noted; and (4) identified where such experimental exposure regimes occurred under ambient conditions. We found that the SUMO exposure index did not perform adequately. We were unable to distinguish among the performances of the SUM06, W126, and SUM08 exposure indices. The results of the analyses of six estimated logistic parameters for a model of diameter2 × height (d2h) vs time indicated O3 effects for both families. At pH 4.3 (near ambient conditions), a response to O3 was detected in the NF × 2.5 treatments for both families for t2, the approximate time of maximum growth during the second year. Using ln (final d2h), family 23 did not show O3 effects. A comparison of the exposures experienced in the NF × 2.5 treatments with those occurring under ambient conditions at other locations showed that in 1983 and 1986, the San Bernardino County (CA) site experienced O3 exposures similar to those values experienced at the NF × 2.5 treatments in 1989.

Characteristics of Sap Trees Used by Overwintering Sphyrapicus varius (Yellow-bellied Sapsuckers) in an Old-growth Pine Forest

Abstract Sphyrapicus varius (Yellow-bellied Sapsuckers) are winter residents of mature Pinus palustris (longleaf pine) forests in the southeastern US. Sapsuckers pierce the bark of mature pines to create wells on living trees and consume the sugar-rich exudate and insects attracted to this food source. To determine sapsucker preferences for individual trees, for locations along boles, and for edge vs. interior habitat, we surveyed an old-growth Pinus palustris stand in lower Alabama with recent sapsucker activity. Individual tree characteristics and stand conditions were evaluated to assess their influence on the number and location of sap wells. Of 596 pines sampled, 74 (12.4%) contained wells. Sapsuckers selected trees with greater diameter at breast height (mean dbh of welled trees = 40.4 cm; non-welled trees = 24.6 cm; P < 0.01). Among pines with wells, sapsuckers fed differentially on different aspects and stem heights. Sap wells were concentrated on the north aspect of the bole (P < 0.05), where wells were 40% more likely to occur than any other aspect. No stand characteristics (plot distance to stand edge, plot basal area, plot tree density, 5-year radial increment growth) significantly influenced sapsucker tree-selection patterns.

Use of a non-linear model in examining growth responses of loblolly pine to ozone and acid precipitation

Abstract Monthly diameter 2 × height ( d 2 h ) data were measured over two years in open-top chambers at Auburn University, Alabama. This study exposed seedlings from two half-sibling loblolly pine ( Pinus taeda L.) families to ozone and acid precipitation treatments. For these data, the accumulation of d 2 h ) by individual trees over two years was efficiently represented by a six-parameter non-linear model of ln ( d 2 h ) as a function of time. Multivariate analysis of variance using these six estimated parameters for each seedling resulted in greater sensitivity to treatment differences as measured by tests of hypotheses than did analysis of covariance on ln (final d 2 h ). This result illustrates the importance of utilizing appropriate analyses that can bring as much of the data as is possible to bear on the question at hand. A test for additional information indicated that five of the six parameters contributed important information concerning treatment differences for at least one of the two families tested. It may be inferred that the treatments have an important effect on the nature of d 2 h accumulation within a growing season as well as on the d 2 h at the end of the growing season.

Productivity of Natural Stands of Longleaf Pine in Relation to Competition and Climatic Factors

Prior to the arrival of settlers to the United States, natural communities dominat by longleaf pine (Pinus palustris Mill.) and maintained by periodic fire occurre throughout most of the southern Atlantic and Gulf coastal plains. These com munities once covered an estimated twenty-four to thirty-six million hectare (h or two-thirds of the area in the Southeast (Vance, 1895; Chapman, 1932). Th range of longleaf pine covers a broad arc along the coastal plain and portions the Piedmont region from southern Virginia, south to central Florida, westward eastern Texas, and extends further inland in the Cumberland Plateau and Ridg and Valley physiographic provinces in Alabama and Georgia. Dissimilar to th other southern pines, longleaf pine tolerates a wide variety of habitats. It is foun growing on dry mountain slopes and ridges in Alabama and northwest Georgia, the low, wet flatwoods, as well as the excessively drained sandhills found alon the coast and fall line. Chapman (1 932) commented that longleaf pine covere more acreage than any other North American ecosystem dominated by a sing tree species.

Overhead shading and growth of young longleaf pine

A study to determine the effects of environmental conditions on the growth of longleaf pine (Pinus palustris Mill.) was initiated in 1969 on the Escambia Experimental Forest near Brewton, Alabama, USA. This study sample consisted of forty young naturally regenerated, even aged longleaf pine seedlings evenly divided between two soil types. At the beginning of the study, the seedlings were 14 years from seed and ranged in height from 0.8 to 1.5 m. From 1969 to 1970, height and diameter measurements were recorded once to four times weekly during the growing seasons and once a month during the dormant seasons. To test the effects of shading on growth, cheesecloth was suspended over 10 randomly selected seedlings from each soil type only during the first growing season, from March 28 to September 24, 1969. This study provides data from the only known in-field shading experiment with longleaf pine seedlings of this size. The effects of the shading treatment and soil type were evaluated for height and diameter growth. The shading treatment did not have a significant effect on either height or diameter growth, but soil type had a significant effect on diameter growth.