黄土高原主要水土保持树种的蒸腾特性

采用精度为0.001 g的精密电子天平和露点水势仪对山杨、刺槐、油松和侧柏的叶片保水力、蒸腾速率日变化及叶水势日变化进行测定。结果表明：自然条件下，4树种叶片保水力从小到大依次为山杨、刺槐、油松、侧柏，其叶片分别经过19、41、49和77 h达自然风干状态；各树种日平均蒸腾速率由大到小的顺序为山杨（0.616 mmol/（m^2·s））〉刺槐（0.605 mmol/（m^2·s））〉油松（0.318 mmol/（m^2·s））〉侧柏（0.270 mmol/（m^2·s）），日最大蒸腾速率的排序为山杨（1.196 mmol/（m^2·s））〉刺槐（1.190 mmol/（m^2·s））〉油松（0.723 mmol/（m^2·s））〉侧柏（0.704 mmol/（m^2·s））；4个树种叶水势以清晨最高，中午最低，傍晚又有所恢复，日变化呈波浪形，日变幅以刺槐最大，其次为山杨和侧柏，油松最小；4个树种叶水势与蒸腾速率之间的关系呈负相关，可用对数曲线来拟合；各树种单位叶面积（cm2）的日（以12 h计）蒸腾耗水量由大到小为：山杨（0.48 mm）〉刺槐（0.47 mm）〉油松（0.25 mm）〉侧柏（0.21 mm）。

Transpiration characteristics of major tree species for soil and water conservation in Loess Plateau

Leaf water conservation capacity,daily changes of transpiration rate and leaf water potential of Populus davidiana,Robinia pseudoacacia,Pinus tabulaeformis and Platycladus orientalis were studied by using precision Electronic Balance with the accuracy of 0.001 g and Dew Point Microvokmeter.The results show that the descending order of the leaf water conservation capacity of four tree species is Populus davidiana,Robinia pseudoacacia,Pinus tabulaeformis,Platycladus orientalis,and it took 19 h、41 h、49 h and 77 h respectively before the leaf-weight did not decrease in natural condition.The descending order of the average transpiration rate is: Populus davidiana(0.616 mmol/(m²·s)),Robinia pseudoacacia(0.605 mmol/(m²·s)),Pinus tabulaeformis(0.318 mmol/(m²·s)),Platycladus orientalis(0.270 mmol/(m²·s)),and the daily maximum transpiration rate in the following descending order: Populus davidiana(1.196mmol/(m²·s)),Robinia pseudoacacia(1.190 mmol/(m²·s)),Pinus tabulaeformis(0.723mmol/(m²·s)),Platycladus orientalis(0.704 mol/(m²·s)).The diurnal variation of leaf water potential was a waveform curve with the highest in the early morning,the lowest at noon and significant recovery in the afternoon,and its daily variation amplitude is in the following order: Robinia pseudoacacia is the largest,while Pinus tabulaeformis is the smallest,and Populus davidiana,Platycladus orientalis are in the middle.Leaf water potential and transpiration rate are negatively related,and the relationship between them can be fitted by logarithmic curve.Daily transpiring water consumption amount(by 12h/d) on unit leaf area(by 1 cm²) of the four tree species is in the following descending order: Populus davidiana(0.48 mm),Robinia pseudoacacia(0.47 mm)>Pinus tabulaeformis(0.25 mm),Platycladus orientalis(0.21 mm).