Change of water vapor exchange properties of 3 tree species under drought

The water vapor exchange properties of Fraxinus mandshurica Rupr., Quercus mongolica Fish. et Turcz. and Acer mono Maxim. at the relative water content of soil (RWCS) of 100%, 70%, 50% and 30% were studied by analysis of water loss, transpiration, water use efficiency (WUE) and stomatal conductance. Seedlings did cost a lot of water during the growing season, and the total water loss of each kind of seedling decreased differently under low RWCS conditions. The dynamics of water loss for 3 species under different RWCS were different. At RWCS of 100%, F. mandshurica and A. mono had higher average leaf transpiration rate than that of Q. mongolica, respectively. Leaf diurnal transpiration of 3 species decreased considerably at RWCS of 30%. But the diurnal WUE was not sensitive to the change of RWCS for these species. Only the average stomatal conductance of A. mono changed significantly under lower RWCS. The implication of these results was that tree species adapted to lower RWCS by changing its water vapor exchange properties, and it would be possible to decrease water loss from forests by selecting proper tree species.