Leaf phosphorus resorption is related to leaf lifespan and labile phosphorus allocation among species in a nutrient-poor sclerophyll woodland

Internal nutrient recycling, such as leaf nutrient resorption, serves as an important strategy for plants to optimise their growth and survival on nutrient-poor soils. Phosphorus resorption efficiency (P_RE) varies widely (20%–90%) among species living on P-poor soils. However, the key drivers behind this local variation are poorly understood. 

We hypothesised that two traits would drive variation in P_RE among species at a site characterised by chronically low soil P (total soil P of 84 ppm): leaf lifespan (LL) and the proportion of leaf P in ‘labile’ fractions that are easily resorbed. Labile P concentration, P_labile, is comprised of inorganic phosphates and soluble phosphorylated metabolites. 

To test this hypothesis and gain a wider understanding of how leaf nutrient resorption varies locally, we quantified a set of related traits for 14 common woody species in a species-rich but nutrient-poor sclerophyll woodland community at Davies Park in the Blue Mountains, NSW, Australia. These traits were LL, P_labile, green and senesced leaf N and P concentrations and P resorption efficiency (P_RE). 

Supporting our hypothesis, LL explained >50% variation in leaf P_RE. Similarly, P_RE was strongly and positively associated (R² > 60%) with the allocation of green leaf P to P_labile. The LL-P_RE relationship was mainly driven by lower senesced leaf P than green leaf P. The local soil P availability explained 60% variation in green leaf P. 

Overall, this study highlights the combination of traits leading to greater internal recycling of P, including high P_RE, long LL and high allocation of leaf P to P_labile, in species-rich, nutrient-poor ecosystems. Read the free Plain Language Summary for this article on the Journal blog.