Phenology and cold tolerance ofPicea rubenssarg. Seedlings exposed to sulfuric and nitric acid mist

Abstract

Phenology and cold tolerance of Picea rubens Sarg. seedlings exposed to sulfuric and nitric acid mist. Accepted Dec. 8, 1991. Scand. J. For. Res. 7: 331-344, 1992 During the growing seasons of 1985-88, red spruce (Picea rubens Sarg.) seedlings were exposed repeatedly in field chambers to sulfuric and/or nitric acid mist in the range of pH 2.5 to 4.5. Hydrogen ion, sulfate, and nitrate concentrations in mist were within the range found in cloudwater of the northeastern USA where high-elevation spruce forests are declining. After the period of exposures, seedlings remained outdoors and buds were sampled in the autumn to determine effects of mist treatments on the number of developing needle primordia. Current-year foliage was sampled from autumn to spring for measurement of cold tolerance by freeze-induced electrolyte leakage (FIEL) and buds were scored for degree of bud break in the early spring. In the 1985-87 experiments when 16-hour overnight mist events were continuous, there were few statistically significant effects of acidic mist on needle primodia development, foliar FIEL, and bud-break. However, in the 1988 experiment when 16-hour overnight mist events were intermittent rather than continuous and acidities fluctuated among events, sulfuric acid mist decreased the number of needle primordia in September and October relative to the other treatments. Acidity of mist increased FIEL in October. Sulfate and nitrate content of mist appeared to influence these effects of acidity on FIEL differently depending on level of cold tolerance and duration of time since the period of exposures to mist. Bud-break in May was not significantly affected by prior mist treatments. Responses to acidic mist were similar among provenances that were obtained from different locations in the northeastern USA, although provenances differed in phenological development and FIEL. Mist deposition to the soil medium was minimized or avoided in these experiments; therefore, we conclude that foliar FIEL of red spruce seedlings is vulnerable to effects of direct contact of acidic mist with foliage. To relate results of these controlled experiments to cloudwater and decline of red spruce trees in the northern Appalachian mountains, the following information is needed: the frequency of wet-dry cycles in the forest; fluctuations in acidity and sulfate and nitrate concentrations among and within cloudwater events; the specific patterns of temperature changes that lead to winter injury; and the relationship between FIEL and freezing damage to foliage for both seedlings and mature trees.

Physiological and Environmental Causes of Freezing Injury in Red Spruce

“…However, other findings indicate that foliar assimilation of SO:-is very limited (Lindberg and Lovett, 1992;McLaughlin et al, 1996). In a separate study, Jacobson et al (1992) reported that the anionic (SO:-and NO;) composition of mist treatments significantly impacted red spruce cold tolerance in the fall, but that the specific impact differed between the two dates assessed: in early October nitrate NOT-treated plants had lower cold tolerance than SO:--treated ones, while in mid-October the opposite was true. During the winter, differences in cold tolerance were associated with treatment pH and not the anionic composition of treatments .…”

“…However, neither of these studies examined the impacts of SO$-on winter hardiness levels (Cape et al, 1991;L'Hirondelle et al, 1992). Jacobson et al (1992) showed that, although SO$-and/or NO3 additions reduced cold tolerance somewhat in autumn, these treatments had no influence on winter hardiness levels. Reductions in winter cold tolerance reported for this study were specifically associated with mist acidity and not the anionic composition of treatments .…”

“…Numerous studies have shown that treatment of red spruce with simulated acid deposition reduces the cold tolerance of current-year needles anywhere from 5 to 12OC (Fowler et al, 1989;Jacobson et al, 1992;Sheppard et al, 1993;Waite et al, 1994;DeHayes et al, 1999;Schaberg et al, 2000a) (see Table 6.5). In addition, studies of seedlings (DeHayes et al, 1991) or branches (Vann et al, 1992) exposed to ambient cloud water show that reductions in cold tolerance comparable to those documented for controlled studies also occur in the field, For example, in a mist exclusion study conducted on Whitetop Mountain, VA, native red spruce seedlings exposed to ambient cloud water were 5°C less cold tolerant in winter than seedlings that had cloud water excluded (DeHayes et al, 1991).…”

Carbohydrate distribution and cellular injuries in acid rain and cold-treated spruce needles

“…Acid mist treatment has led to increased needle injury after low temperature treatment in many experiments Jacobson et al 1992), and an inhibitory effect upon recovery has also been detected (Eamus and Murray 1993). The recovery from freezing was also slower in the acid rain-treated seedlings than in the controls.…”

“…thinning of cytoplasmic membranes, damage to the to March 1989. Short-term acid rain treatment does not affect the amount or type of ultrastructural freezing damage (Reinikainen and Huttunen 1989a), although acid rain or mist has been postulated as a predisposing factor with respect to frost damage Jacobson et al 1992), and although prolonged exposure to acid rain results in disturbances in hardening (Back and Huttunen 1992). Weather data are from the Finnish Institute of Meteorology plasmalemma and finally also damage to the chloroplasts.…”