Plant-plant interactions and resource dynamics of Abies fabri and Picea brachytyla as affected by phosphorus fertilization

Although extensive research has been conducted on the temporal dynamics of plant-plant interactions, little is known about the effect of phosphorus (P) availability. In this study, Abies fabri and Picea brachytyla seedlings were collected from the late-stage Hailuogou glacier retreat area and grown under different P regimes (control and P fertilization) from year 2015 to 2016 in a common garden experiment to investigate whether plant-plant interactions are modulated by P availability. We found that P fertilization affected the relative competition intensity (RCI). Under control conditions in 2015, the growth of A. fabri was facilitated by the presence of P. brachytyla. Under P fertilization, the facilitative effect was more intensive: the leaf, stem and total biomass of A. fabri significantly increased under interspecific interaction compared with intraspecific interaction, but no effect was found in P. brachytyla. RCI showed similar tendencies both in 2015 and 2016. In addition, plant-plant interactions and P fertilization caused temporal variation in C, N, P and non-structural carbohydrate (NSC) contents. The growth of A. fabri greatly benefited from the presence of P. brachytyla when exposed to P fertilization and showed higher biomass, and C, N, P and NSC accumulations. Our results demonstrated interactive effects between environmental conditions (i.e. P availability) and plant-plant interactions that are closely related to resource accumulation.