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

Condition of Scots pine fine roots and mycorrhiza after fungicide application and low-level ozone exposure in a 2-year field experiment

“…Furthermore, ozone exposure had a temporary stimulating effect on mycorrhizas and number of total short roots after the first summer, which was supported by the good structural condition of mycorrhizas, even after the second summer, and agrees with a similar field experiment of Rantanen et al (1994) and with studies of Reich et al (1985) and Qiu et al (1993). However, Pérez-Soba et al (1995) found that slightly higher ozone exposure (55 ppb daily, 11 weeks) strongly reduced mycorrhizal infection in Scots pine roots, but mycorrhizal infection level in Pinus halepensis seedlings was not affected by ozone exposure (Díaz et al 1996).…”

Effects of Wet Acid Deposition and Soil Fertility on Seedling Growth, Nutrition, and Water Relations

“…Among conifers, Blaschke (1990) documented a reduction in mycorrhization of Norway spruce due to pH 4.0 rainfall, and Dighton and Skeffington (1987) a reduction in that of Scots pine due to pH 3.0 rains. However, Temple et al (1993) found rain acidity had no effect on mycorrhizal development of ponderosa pine, while in loblolly pine, Adams and O'Neill (1991) and reported a similar finding but Shafer et al (1985), Esher et al (1992), and Qiu et al (1993) collectively revealed that rainfall in the range of pH 4.3 to pH 3.2 reduced infection levels in this host. In contrast, the results reported here reveal that ectomycorrhizal formation of white oak was unaffected by rain treatment while that of loblolly pine was stimulated by the most acidic treatment.…”

“…Rationale for the selection of these two commercially and ecologically valuable species for study was derived from the conviction, also held by others (Lee and Weber 1979;Amezaga et al 1997), that comparisons between hardwoods and conifers of the effects of acid deposition on forest trees may yield different insights than studies of individual species. Furthermore, this combination of species includes a conifer which has been the focus of extensive research (Shafer et al 1985;Edwards et al 1990;Adams and O'Neill 1991;Edwards et al 1991;Walker and McLaughlin 1991;Esher et al 1992;Qiu et al 1992Qiu et al , 1993Walker and McLaughlin 1993;Baker et al 1994;McLaughlin et al 1994;Reddy et al 1995;Reinert et al 1996;Walker and McLaughlin 1997) and a hardwood that has been comparatively little investigated (Walker and McLaughlin 1991. Experimentation with forest tree seedlings has revealed substantial interspecific variation in their reaction to acid deposition.…”

Interactions between exposure to O3 and nutrient status of trees: effects on nutrient content and uptake, growth, mycorrhiza and needle ultrastructure

“…Radial growtb of stems might have been retarded by translocation of carbon to roots, as suggested by decreased sboot-to-root ratio and initial stimulation of mycorrbiza formation in both species in O.j exposure. Howe\'er, tbese beneficial effects, as detected also by Qiu et al (1993), are possibly transient and in tbe long-term, damage caused by O3 may be apparent, supported by tbe observation of reduced numbers of mycorrhiza of Norway spruce roots in harvest 2. Correspondingly, Edwards et al (1992) reported reduced biomass of all plant parts, unchanged stem diameter and increased height of Pinus taeda after a three-year exposure to concentrations of O.J twice tbe ambient level in Tennessee, USA.…”