Transpiration characteristics of major shrub species for soil conservation on the Loess Plateau in western Shanxi Province, northern China

Leaf water content, daily changes of transpiration rate, leaf water potential of Forsythia suspensa, Lonicera japonica, Rubus crataegifolius and Swida alba were studied by using the classical method of measuring tree transpiration—rapid weighing method, which would be beneficial to vegetation reconstruction and reasonable density by selecting tree species of lower water consumption under condition of water deficiency on the Loess Plateau. The results showed that the leaf water content in the morning and evening was higher than at noon and its daily variation amplitude was in the following descending order: R.crataegifolius (94.4%－111.2%)was the largest , while F. suspensa (55.8%－61.2%)was the smallest, S. alba (78.7%－105.2%) and L.japonica (69.6%－84.0%) were in the middle.The relationship between fresh weight and leaf areas can be fitted by Exponential curve.The four species had the average transpiration rate in the following order: R.crataegifolius (1.985-2.578 mmol/(m2·s)) S. alba(1.570-1.754 mmol/(m2·s)) L.japonica (1.417-1.485 mmol/(m2·s)) F. suspensa (1.160-1.399 mmol/(m2·s)). The diurnal variation of leaf water potential was a waveform curve and its daily variation amplitude was in the following descending order: R.crataegifolius was the largest, while F. suspensa was the smallest, S. alba and L.japonica were in the middle. Leaf water potential and transpiration rate were negatively related, and the relationship between them can be fitted by logarithmic curve.The equation and contribution of transpiration and meteorological factors were obtained, their integreted model was established with statistical analysis and principal component analysis, and the main factors of influencing transpiration rate were different from varied shrub species.