Patterns and driving factors of water and nitrogen use efficiency in Robinia pseudoacacia L. on the Loess Plateau in China

Abstract

Water use efficiency (WUE) and nitrogen use efficiency (NUE) demonstrates the competitive strategies of plants with limited resources, which is important in mediating survival productivity and fitness of plants. Previous studies have found that there is a trade-off relationship between WUE and NUE and that they are affected by many factors, such as climate variables, geographical variables and soil properties. However, the patterns of WUE and NUE in Robinia pseudoacacia on the Loess Plateau are unclear and their driving factors need to be investigated to advance our knowledge of these key parameters to understand the coupling of carbon, nitrogen and water cycle. In this study, we calculated the WUE and NUE in Robinia pseudoacacia along a precipitation transect on the Loess Plateau and examined the effects of influencing factors on WUE and NUE. Our results showed that WUE varied from 64.03 to 103.08 μmol mmol⁻¹, and NUE varied from 11.26 to 18.19 gC g⁻¹N. Latitude played a substantial role in WUE, and soil nitrogen (ammonium nitrogen and total nitrogen) played a substantial role in NUE. In addition, NUE in Robinia pseudoacacia was lower than the average value of whole plants on the Loess Plateau, and the growth of Robinia pseudoacacia was mainly restricted by phosphorus. By dividing into three zones, zone 3 had higher WUE in where with higher latitude and lower precipitation, and NUE was not significant among the three zones. These results highlight the importance of location variables and soil chemical properties to WUE and NUE and provide useful information for understanding the coupling of carbon, nitrogen and water cycle of plants in ecosystems.