Effects of Controlled Levels of Sulphur Dioxide on Western Wheatgrass in a South-Eastern Montana Grassland

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Abstract
Swards dominated by western wheatgrass (Agropyron smithii Rydb.) at 2 sites in Montana [USA] were continuously fumigated with 2,4 and 7 pphm [parts perhundred million] of SO2 mid-May-Oct. in 1975 and April-Oct. in 1976. SO2 stimulated leaf growth by increasing the number of leaves per plant. The responses was related to both the concentration of SO2 and the period of exposure. Leaves senesced more rapidly at higher SO2 concentrations. SO2 treatments did not significantly alter the net production of aboveground parts, the growth rates of aboveground parts, net assimilation rates, nor did they affect the leaf area ratios of either western wheatgrass or the entire community. The effects of SO2 on leaf growth, and the N:S ratios in plant material, indicated that there may be S deficiency in the grasslands studied.