The Geographic Variation Of Leaf Nitrogen And Phosphorus In Oriental Oak (Quercus Variabilis) And Its Relation To Environmental Factor

Plant ecological stoichiometry has been developed in recent years. Nitrogen and phosphorus are the limiting elements for the terrestrial plants. Oriental oak (Quercus variabilis) was one of the most widely distributed trees in Eastern Asia and had great value in ecology, economy and landscape. In order to find out the response of nutrient status of plant to the climatic change, it is of great importance to study the N, P concentration and the N:P mass ratio of plant, as well as the relationships between the nutrient and climatic factors in a regional scale. The present distribution of Q. variabilis and the climate characters were studied by field work and searching existing papers. According to the present distribution, 20 sites were selected and set up in 13 provinces across China. Leaf samples were collected from the sites and analyzed.The results showed that the Q. variabilis mainly had a distribution between 22°-42°N, 98°-122°E. Horizontally, the mean, maximum and minimum of the MAT ( mean annual temperature) of Q. variabilis in China mainland were 15.8, 23.6, 7.2℃respectively, and the precipitation ranged from 411 to 2000 mm; in Taiwan, the mean MAT was 14.7℃, and the mean precipitation was 2803 mm. In the temperate zone, the distribution upper limit of Q. variabilis was 1500 m, and the MAT was 7.6℃, while in the subtropical zone, the upper limit was more than 3000 m, and the MAT was 7.7℃.The stoichiometry study showed, the mean concentration of leaf N of Q. variabilis across all the sites was 17.55 mg/g, the minimum and maximum were obtained in Luotian in Hubei Province(15.1±0.441 mg/g) and Xinkou in Fujian Province (21.09±0.758 mg/g) respectively. Mean concentration of leaf P was 1.04 mg/g across China, the minimum and maximum were obtained in Qimen in Anhui Province ( 0.617±0.0228 mg/g) and Kuming in Yunnan Province ( 1.37±0.063 mg/g) respectively. The N:P ratio had an average level at 17.93 and ranged from 12.372 (Kunming) to 26.879 (Xinkou).Leaf P and N:P ratio were significantly correlated with MAT and latitude across all sites, while the leaf N was weakly correlated with MAT and latitude. In general, leaf P decreased as the MAT increased and the latitude decreased. Leaf N was also weakly correlated with precipitation (p > 0.05), while the leaf P was significantly correlated with precipitation (p < 0.01), N:P ratio also significantly correlated with precipitation (p < 0.05). Generally, leaf P decreased and N:P ratio as the precipitation increased.In comparison with global pattern, the plants in China were limited by P and the P concentration was low in the soil. It was suggested fertilizing the forest with P.