Leaf stoichiometry of two conifer species with different life forms in northern Daxing’an Mountains of northeastern China

Objective This paper studies the difference in ecological stoichiometric characteristics and their changes with increasing age of conifers of deciduous and evergreen species in the cold temperate zone to reveal the relationship between ecological stoichiometric characteristics and growth stage of two different life forms of conifers, and to provide help for the study of plant growth and nutrient supply in cold-temperate of China.

Method The contents and stoichiometric characteristics of C, N, P in Larix gmelinii and Pinus sylvestris var. mongolica from May to September were studied. The correlations between C, N, P and environmental factors were analyzed by homeostasis index and Pearson correlation coefficient.

Result (1) During different growth stage, monthly average N, P contents of L. gmelinii and P. sylvestris var. mongolica needles were both decreased with the increase of age class, while the C content increased with the increase of age class. The N and P contents of needles of L. gmelinii from May to August were higher than those of P. sylvestris var. mongolica, while the C content was lower than that of P. sylvestris var. mongolica. (2) The monthly mean values of C∶N, C∶P and N∶P of needles of L. gmelinii were higher than those of P. sylvestris var. mongolica. The N∶P of needles of L. gmelinii of four age classs were all less than 14, while the N∶P of needles of P. sylvestris of four age classes from May to July was less than 14, and the N∶P of needles of P. sylvestris var. mongolica of four age classes was more than 16. The homeostasis of N, P and N∶P of L. gmelinii needles was greater than that of P. sylvestris var. mongolica. (3) Soil moisture content was significantly correlated with the ecological stoichiometric characteristics of the needles of the two species. The N content of needles of P. sylvestris var. mongolica was significantly correlated with the stoichiometric ratio of C, N and P, and the C content of needles of L. gmelinii was significantly correlated with N∶P and soil ammonium and nitrate nitrogen.

Conclusion The two coniferous tree species with different life forms in the northern Daxing’an Mountains have different adaptation strategies to cold climate and frozen soil. L. gmelinii is the dominant species in the top community, but its different growth stages are both limited by N. However, the growth limiting factors of P. sylvestris var. mongolica are different due to seasonal changes.