In order to explore the response of foliar water use efficiency (WUE) of typical artificial ecological forest(Robinia pseudoacacia) and artificial economic forest (Apple) to environmental factors and the difference in different climate zones in the Loess Plateau

leaf samples from 22 samples were taken as research subject in the Loess Plateau. The stable carbon isotope technique was used

which could reflect the long-term WUE of plants.We measured the δ

13

C value of mature leaves of plants

analyzed its response to annual precipitation

temperature

solar radiation

relative humidity and water vapor pressure

and examined the difference between artificial ecolo

gical forest and economic forest in different climate zones. The results showed that:(1) The foliar WUE of apple was significantlyhigher than that of Robinia pseudoacacia

the values were 4.29 mmol CO

2

/mol H

2

O and 3.83 mmol CO

2

/mol H

2

O respectively. (2) The foliar WUE of the same plant in semi-arid area was higher than that in semi-humid area in climate regionalization. The foliar WUE of apple in semi-arid area was 12.5% higher than that in semi-humid area. The foliar WUE of Robiniapseudoacacia in semi-arid area was 6.4% higher than that in semi-humid area. (3) The foliar WUE of apple and Robinia pseudoacacia had the same response to environmental factors

and the response of foliar WUE to average water vapor pressure was more sensitive than other factors. The results expand the study of WUE and provide theoretical guidance for the improvement of WUE in the Loess Plateau.