干旱胁迫对苗木蒸腾耗水日变化的影响

采用BP340 0精密电子天平 ,于 2 0 0 2年夏季研究了在不同水分胁迫条件下 ,4种北方主要造林树种苗木的日蒸腾耗水速率及实际耗水量变化规律 .结果表明 ,在正常水分条件下 ,各苗木的日最大耗水速率出现在 10 :0 0— 14 :0 0之间 ,阔叶树种的蒸腾耗水速率远远大于针叶树种 ,是针叶树种的 5～ 7倍 ,苗木的耗水速率排序为 :黄栌 >火炬树 >侧柏 >油松 ;1年生的黄栌和火炬树与 5年生侧柏的日耗水量相差不大 ,是油松的 1倍 .当苗木受到干旱胁迫后 ,苗木的日最大耗水速率会提前 ,蒸腾速率迅速下降 ,但下降幅度不同 ,耗水速率排序为 :火炬树 >黄栌 >油松 >侧柏 .在中等干旱胁迫下 ,油松、火炬树、侧柏、黄栌的日平均耗水速率分别下降了 5 4 0 %、6 8 6 %、87 2 %和 90 2 % ;侧柏和黄栌之间 ,油松和火炬树之间的日耗水量基本相同 ,但侧柏和黄栌只有油松和火炬树的一半 ;干旱胁迫继续加重后 ,油松、火炬树、侧柏、黄栌的日平均耗水速率只有水分正常条件下的 15 7%、12 1%、4 3%和 9 2 % ,日耗水总量下降到 5 %～10 % ,4个树种间相差不大 .

Daily variation in transpiring water-consumption rates of seedlings in different drought stress

Daily variation in transpiring water|consumption rates and water consumption of four main plantation tree species in North China were studied by using BP3400 Precision Electronic Balance in summer of 2002 The results showed that the daily highest water|consumption rate of seedlings was in 10:00—14:00 in normal water supply, and the transpiring water consumption rates of broad leaf tree species were 5 to 7 times bigger than coniferous species. These four species had the average transpiring water consumption rates in the following order: Cotinus coggygria (130 0) > Rhus typhina(110 0) > Platycladus orientalis(22 0) > Pinus tabulaeformis (17 1). The daily amounts of water consumption of C. coggygria (1 year old) and R. typhina (1 year old) were the same as P. orientalis (5 year old), and the quantities were two times over that of P. tabulaeformis (5 year old). When the seedlings were in drought stress, the time that the daily highest water|consumption rate appeared was moved up by 2 to 4 hours. The transpiring water|consumption rates decreased quickly and had different rates, which was in descending order of R. typhina, C. coggygria, P. tabulaeformis and P. orientalis. The daily average water|consumption rates of four species were reduced by 68 6%, 90 2%, 54 0% and 87 2% respectively in medium drought stress. The amounts of water consumption between P. orientalis and C. coggygria and those between P. tabulaeformis and R. typhina were almost the same, and the amounts of the latter were double as those of the former. When the seedlings were in serious drought stress, the daily average water|consumption rates of P. tabulaeformis, R. typhina, P. orientalis and C. coggygria decreased by 15 7%, 12 1%, 4 3% and 9 2% respectively of those in normal water condition. The water consumption of the four tree species also down to 5% to 10% and the four species had almost the same daily amounts.