从水力结构比较3种共存木本植物的抗旱策略

Comparison of drought strategies of three co-existing woody plants by their hydraulic structures

通过盆栽控水方法测定了华北石质山区刺槐、栓皮栎和侧柏3个主要造林树种在干旱胁迫以及随后的复水条件下气体交换和水分关系的变化,分析了这3个树种抗旱特性的差异。结果表明:1)在供水充足时,刺槐光合作用强、气孔导度大、耗水速度快。2)刺槐对土壤水分变化最为敏感,当土壤水分含量降低时,其光合速率和气孔导度迅速下降。3)复水后,刺槐和栓皮栎恢复速度比侧柏快。4)当小枝导水损失率发生变化时,刺槐的气孔导度变化迅速,相比之下,栓皮栎和侧柏对土壤水分变化以及其气孔导度随水力变化的反应都较为平缓。5)刺槐在水分充足时迅速进行光合积累,而干旱时,通过气孔关闭甚至落叶来避免过度失水。另外2种植物在中度干旱时,尤可保持光合作用,其中侧柏更为突出。在华北半干旱的石质山区,刺槐的发展受到较大限制。

This paper investigates the physiological characteristics for drought resistance among three main afforestation woody species（ie Robinia pseudoacacia L.,Quercus variabilis Blume,Platycladus orientalis（L.） Franco） in lithoid mountainous areas in north China.Variations in their gas exchanges and water relations were comparatively measured during withholding water and subsequent rewatering of potted seedlings.The results showed that：1） under well-watered conditions,black locust（R.pseudoacacia） had the strongest photosynthesis,the greatest stomatal conductance and water consumption among the three species.2） However,black locust was most sensitive to soil drying among the three species,its photosynthesis and stomatal conductance rapidly declined.3） On being rewatered,both gas exchanges and water relations were able to be rapidly recovered in all three species,among which black locust and cork oak（Q.variabilis） had faster recovery than arborvitae（P.orientalis）.4） Stomatal conductance（gs） of black locust changed rapidly when percentage loss of hydraulic conductivity（PLC） varied.By contrast,gs of cork oak and arborvitae changed much slower in response to soil moisture and PLC.In summary,black locust is able to rapidly assimilate and accumulate carbohydrates in well-watered conditions,however,when drought came,it sharply shut down its stomata and even shed leaves to prevent excessive loss of water.To the contrast,the other two species could maintain fairly high photosynthesis in intermediate drought stress,especially arborvitae.Soil moisture condition in the lithoid mountainous areas could restrict the development of black locust forests.