Research on the water use efficiency and foliar nutrient status of Populus euphratica and Tamarix ramosissima in the extreme arid region of China

摘要

Seasonal variations in foliar stable carbon composition (δ~(13)C) and nitrogen (N), phosphorus (P) and potassium (K) concentrations of Populus euphratica Olivier and Tamarix ramosissima Ledeb, as well as correlations between foliar δ~(13)C values and N, P and K concentrations were studied in the Ejina oasis in the lower reaches of the Heihe River, northwestern China. Foliar δ~(13)C values, and P and K concentrations significantly differed between species. Foliar δ~(13)C signatures in T. ramosissima were significantly more enriched than those in P. euphratica, but P and K concentrations of P. euphratica were higher. The seasonal variations and patterns of these were similar. The total foliar δ~(13)C values and N, P and K concentrations in both P. euphratica and T. ramosissima showed a descending trend. There were significantly positive correlations between foliar δ~(13)C values and N and P concentration of both P. euphratica and T. ramosissima. For the relationship between foliar δ~(13)C and K concentration, there appeared oppositely positive and negative correlations in P. euphratica and T. ramosissima, respectively, but they were not significant. The simple positive correlations of δ~(13)C-P% and δ~(13)C-N% suggested that N and P in P. euphratica and T. ramosissima behave in a similar manner. This study also showed that there were nutrient deficiencies; N and P nutriments were the co-limiting factors in P. euphratica, while it was P nutriment in T. ramosissima.