Phosphorus (P) mobilisation from inorganic and organic P sources depends on P-acquisition strategies in dioecious Populus euphratica

Abstract

Dioecious species have secondary trait dimorphism in resource acquisition, allocation, and a skewed sex ratio. Yet, it is unclear how their sex-specific nutrient acquisition strategy affects the contributions of inorganic and organic phosphorus (P) soil pools to plant-available P. Here, the contribution of inorganic and organic P sources to available P in soil and sex-specific P acquisition during the whole growing season (from June to October) was assessed in a 20-year-old Populus euphratica plantation via analysing the transformation of soil P pools. Poplar females obtain available inorganic P by increasing specific root length (by 71% compared with males) and releasing organic acids to mobilise P from precipitated P (HCl-P), thus obtaining higher P than males during the mid-growing season (June). The increased mobilisation of moderately precipitated P in the rhizosphere was more significant in females during the whole growing season. During the late-growing season, males showed increased alkaline phosphatase activities (by 25% compared with females) and maintained a higher abundance of arbuscular mycorrhiza fungi to obtain P via higher consumption of organic and residual P (decreased by 68% and 24% from June to October). These changes in P acquisition strategies reflect the temporal niche differentiation: females acquire inorganic P mainly during the beginning and middle of the season, whereas males take up organic P and HCl-P, preferably in the second half of the season. The strategic adjustment of sex-specific P acquisition modulated the transformation of organic and inorganic P sources in soil towards plant-available P, increasing resource niche partitioning between two poplar sexes to maintain P supply.