Four genotypes of shortleaf pine (Pinusechinata Mill.) were grown in open-top chambers in the Piedmont Region of South Carolina. The seedlings were exposed to several combinations of ozone (near zero, ambient, 1.7 × ambient, or 2.5 × ambient) and acid rain (pH 3.3, 4.3, or 5.3). Glucose, sucrose, total reducing sugars, and starch contents of the pine needles were determined initially and at 5- to 12-week intervals during the following 38 weeks of exposure. Needles exposed to acid rain and ozone treatments followed the seasonal trends normally encountered in carbohydrate content, but there were some statistically significant differences in the quantities of individual carbohydrate components after prolonged exposure. In general, those needles exposed to higher levels of ozone (1.7 or 2.5 × ambient) had lower levels of starch and sucrose, with higher levels of both glucose and total reducing sugars. The starch levels in needles exposed to elevated ozone showed decreased values throughout the dormant period at all pH levels. Similarly, the sucrose levels were significantly lower in the high ozone and high acid rain treatment after 38 weeks of exposure. These results indicate that air pollutants may be affecting the carbon allocation balance within the needles.
Shortleaf pine (Pinus echinata Mill.) seedlings in 24 open-top chambers were exposed to combinations of ozone (carbon-filtered (control), ambient, 1.7 x ambient, and 2.5 x ambient) and acidic precipitation (pH 5.3, 4.3 and 3.3) for 16 months (1989 harvest) or 28 months (1990 harvest). Although the effects of acid rain were generally not significant, there was a trend toward increased aboveground biomass and leaf area in seedlings subjected to the low pH treatments. Because N concentrations in the soils generally increased with decreasing pH, we concluded that the effects of acid rain on aboveground biomass and leaf area were a consequence of an increasing concentration of soil N. In the 1989 harvest, seedlings in the 2.5 x ambient ozone treatment had significantly less biomass in all aboveground plant components and significantly less total leaf area than seedlings in the 1.7 x ambient ozone treatment. In the 1990 harvest, there were no significant effects of ozone on total aboveground biomass, although there was a trend toward reduced biomass in seedlings in the 2.5 x ambient ozone treatment. Both total leaf area and leaf biomass were significantly less in seedlings exposed to 2.5 x ambient ozone for 28 months than in both control seedlings and seedlings in the 1.7 x ambient ozone treatment. The greater, but not always significant, aboveground biomass and leaf area of seedlings in the 1.7 x ambient ozone treatment compared with control seedlings may be associated with the observed increase in soil nitrate concentration as a result of increased rates of leaf senescence and litterfall.
Shortleaf pine (Pinusechinata Mill.) seedlings grown in open-top chambers were exposed to several combinations of ozone (near zero, ambient, 1.7 × ambient, or 2.5 × ambient) in conjunction with acid rain (pH 3.3, 4.3, or 5.3) starting in August 1988. Needle samples from the first (89-1) and third (89-3) flushes of the 1989 growing season were analyzed for their glucose, sucrose, total reducing sugars, and starch contents. For the 89-1 flush (current-year needles), no differences in glucose, sucrose, or starch contents were observed among the various ozone exposures during 1989. However, needles exposed to 2.5 × ambient ozone exhibited higher levels of total reducing sugars compared with other ozone exposures for most of 1989. High H+ concentration (pH 3.3) increased glucose content (compared with pH 4.3 or 5.3) in the September sampling only. No significant differences were observed among ozone treatments for the total reducing sugars, glucose, or starch contents of the 89-3 flush (previous-year needles) for most of the sampling periods in 1990. However, the sucrose content was lower in needles receiving 2.5 × ambient ozone compared with other ozone exposures. Although high H+ concentration (pH 3.3) appeared to affect some carbohydrate components, there was no general trend observed.
The U.S. Environmental Protection Agency's computer data base (STORET) was employed to retrieve stream water quality data for a 9‐year period on an agricultural watershed in Maryland, 40 km northwest of Washington, D.C. Most of the farms in the area are large dairy operations that have waste management and storage facilities. During the study period, farmers increased their use of no‐till and minimum‐tillage corn (Zea mays L.) practices by as much as 90%, and several operators also installed animal waste‐control facilities.Total PO4, fecal coliform, and NO3 + NO2‐N data from four sampling stations in the watershed were retrieved from STORET and statistically analyzed using linear regression to relate concentration and time. The regressions indicated that concentrations of total PO4 and fecal coliform decreased with time. Total PO4 data from all four sampling stations showed a significant inverse relationship between time and concentration (5% probability or less). Of the four fecal coliform regressions, the furthest‐upstream sampling station was significant while the next one downstream approached significance (6% level). No statistical significance was evident in the NO3 + NO2‐N regression equations at any of the four stations during the 9‐year period.Results indicated that the time and costs for this type of analysis were reduced substantially by using the computer‐stored data base rather than direct sampling and laboratory analysis. A study similar to this one, but with in‐house data collection and analysis, would cost approximately 10 times more than the study reported herein.
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