紫外线B辐射对几种植物种间竞争的影响

Effect of enhanced UV-B radiation on competition among several plant species

对大田条件下增强的紫外线B(UV B 2 80～ 31 5nm ,约相当于 1 5 %臭氧层衰减 )对小麦和野燕麦等 4个种对的竞争性平衡的影响进行了研究 .结果表明 ,对照和UV B处理时小麦和野燕麦的密度制约死亡规律没有显著差异 ,相对较大的竞争压力加强了UV B对这两个物种生物量降低的效应 .UV B辐射处理后 ,按单株生物量和地上部生物量 ,UV B增强了小麦对野燕麦的竞争优势 ,但是以单株籽粒数及籽粒重为依据的k1 2 值在紫外辐射处理后却下降 .竞争性平衡的改变伴随着两者总生物量的显著下降 ,特别是在较高的密度条件下 .紫外辐射对其它 3个种对的竞争性平衡有着不同程度与方向上的影响 .一般情况下UV B使竞争性平衡向有利于单子叶植物的方向发展 .这一结果暗示 ,竞争胁迫 ,特别是种间竞争对正确评估UV

The effect of enhanced UV B radiation (280～315 nm, approximating a 15% ozone layer reduction) on competitive interaction between spring wheat ( Triticum aestivum ) and wild oat ( Avena fatua ) was examined in the field. The density dependent mortality of both wheat and wild oat did not exhibit a significant difference between control and UV B treatments. A relatively high degree of competitive stress enhanced the effect of UV B stress on biomass reduction.Under UV B enhancement ,the relative competitive status of wheat in terms of total biomass and aboveground biomass increased ,but decreased when based upon grain production. Shifts in competitive balance occurred with significant changes in total biomass, especially when plants grew at higher densities in monocultures and mixtures. There were different effects in direction and intensity of UV B radiation on competition balance of the other three species pairs, but in general, the effect of UV B was in favor of monocotyledonous. The results implied that total degree of competitive stress,especially interspecific competition,might be crucial to assess the effect of UV B enhancement on agriculture ecosystem properly.