Studies on Transpiration of seedlings of the Main Tree Species Under the Condition of Drought Stress in the Dry-hot River Valleys of the Jinsha River

Transp iration of twenty-nine potted afforestation species for vegetation restoration in the dry-hot valleys ofthe J insha Riverwas studied under different drought stressweight on typ ical sunny day. Five main conclusionsweregotten as follows: (1) The transp iring water consump tion of different seedlings in the day time p resented a sustaineddescent with the drought stress, the descending extent of different seedlingswas obviously different. The seedlings,with the strong water consump tion, were more easy and quick to suffer from drought stress. ( 2 ) After six-day’sdrought treatment, the p ractical water consump tion of Acacia m earnsii, Leucaena leucocephala cv. Salvador,Carallia longipes, Euca lyptus globu lus descended the most, being 85. 78%～93. 11%; Sch leichera oleosa, B om baxm alabaricum, Tephrosia candida, A lbizia kalkora, Pinus yunnanensis descended the least, being only6. 37%～17. 42%. The classified result by the descended extent of water consump tion was identical to thecomparison result of slope k. ( 3) The transp iring water consump tion of seedlings in the first day determined thedynamic variation of water losing. With the sustaining of drought stress, the p roportion ofwater consump tion in the night to water consump tion in the whole day gradually increased. ( 4) When the seedlings suffered serious droughtstress inMarch, the descending p roportion order of transp iring from water consump tion of twenty-five species wasidentical to the size orderwhile suffering from middle2class drought stress. (5) According to the quantitative formulabetween transp iring water consump tion rate of seedlings in the day time, systematically classified method could beused to divide twenty-nine tree species into four classifications including high transp iring water consump tion, subhigh transp iring water consump tion, sub-low transp iring water consump tion and low transp iring water consump tion.