Wilbourn S, Davison A W, Ollerenshaw J H
Department of Agricultural & Environmental Science, Ridley Building, The University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK.
New Phytol. 1995 Jan;129(1):23-32. doi: 10.1111/j.1469-8137.1995.tb03006.x.
A mixture of Trifolium repens L. (var. Grasslands Huia) and Lolium perenne L. (var. Melle) was established in an area with low ambient ozone concentrations and exposed to episodes of ozone using a simple, unenclosed field fumigation system. Control plots were exposed to ambient air. There were two cutting frequencies to simulate grazing and silage production respectively. This paper reports on the performance of the system and the effects on yield and species composition in the first year of fumigation. The system operated satisfactorily when the wind speed was between 1 and 5 m s . When the wind dropped suddenly below 1 m s there were short periods with high concentrations but these events were rare and did not last more than a few minutes. Above 5 m s there was lateral downwind spillage of ozone and at higher wind speeds it was not possible to maintain the target concentration of 50-70 nl 1 . The plots were fumigated only when the weather was suitable for ozone formation and when the wind speed was stable. Because the weather was poor, fumigation was restricted to 22 d between July and September. The mean 4-7 h concentrations were 50-70 nl l . Seven-hour mean ambient concentrations over the same period were 10-28 nl 1 . There were significant effects of ozone on yield and herbage composition. The effects varied between harvests, probably because of differences in the timing of cutting relative to the episodes, and to the differences in phenology between the species. Most of the loss of yield was due to effects on Trifolium, which was much more sensitive than Lolium. There was a persistent effect of ozone on the stolon density of Trifolium which lasted into the following year. It is suggested that this arose because the clover replaced damaged leaves very quickly, maintaining the canopy at the expense of the stolons. Persistent effects on stolons might lead to poorer winter survival and lower nitrogen fixation. Gaps in the sward as a result of loss of Trifolium might allow rapid weed invasion. There was no interaction between cutting frequency and ozone, which may have been due to the fact that the poor summer restricted the number of cuts and therefore decreased the difference between the two cutting frequencies.
将白三叶草（草原惠亚变种）和多年生黑麦草（梅勒变种）的混合物种植在环境臭氧浓度较低的区域，并使用简单的开放式田间熏蒸系统使其暴露于臭氧环境中。对照地块暴露于环境空气中。设置了两种刈割频率，分别模拟放牧和青贮生产。本文报告了该系统的运行情况以及熏蒸第一年对产量和物种组成的影响。当风速在1至5米/秒之间时，该系统运行良好。当风速突然降至1米/秒以下时，会出现短时间的高浓度情况，但这些情况很少见，且持续时间不超过几分钟。风速高于5米/秒时，臭氧会侧向顺风溢出，在更高风速下无法维持50 - 70纳升/升的目标浓度。仅在天气适合臭氧形成且风速稳定时对地块进行熏蒸。由于天气不佳，熏蒸时间限制在7月至9月之间的22天。4 - 7小时的平均浓度为50 - 70纳升/升。同期7小时的平均环境浓度为10 - 28纳升/升。臭氧对产量和牧草组成有显著影响。不同收获期的影响有所不同，这可能是由于刈割时间相对于臭氧暴露事件的差异以及物种物候差异所致。大部分产量损失是由于对三叶草的影响，三叶草比黑麦草敏感得多。臭氧对三叶草匍匐茎密度有持续影响，这种影响持续到次年。据推测，这是因为三叶草能非常迅速地替换受损叶片，以牺牲匍匐茎为代价维持冠层。对匍匐茎的持续影响可能导致冬季存活率降低和固氮能力下降。由于三叶草损失导致的草地间隙可能会使杂草迅速入侵。刈割频率与臭氧之间没有相互作用，这可能是因为夏季不佳限制了刈割次数，并因此减小了两种刈割频率之间的差异。
