Nutrient resorption (NuR), the critical process where plants reclaim nitrogen (N) and phosphorus (P) from aging leaves before leaf fall, serves as a vital adaptation for survival in nutrient-scarce environments. Despite its ecological significance, there is a paucity of studies examining the N and P resorption efficiencies (NRE and PRE) of epiphytes—plants that are integral to the forest ecosystems of southwest China.

In a study published in Plant, Cell & Environment, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences have shed light on the leaf nutrient resorption characteristics of vascular epiphytes. The study highlighted how the nutrient resorption processes enabled epiphytes to persist in canopy environments where soil-derived nutrients are inaccessible. 

The researchers analyzed N and P concentrations alongside nitrogen isotope composition (δ¹⁵N) in mature and senescent leaves from 10 subtropical epiphyte species in Ailao Mountains National Nature Reserve in Yunnan. By using data from prior research on tropical lowland forests, they compared nitrogen and phosphorus resorption efficiencies and regulatory patterns across climates.

Notably, despite significant mass loss during leaf senescence, epiphytes matched terrestrial plants in resorption efficiency—a remarkable feat given their aerial habitat constraints. Functional group identity emerged as the primary driver of N recovery, while δ¹⁵N values provided species-specific insights into nutrient recycling proficiency.

Geographical disparities further shaped strategies: tropical epiphytes prioritized phosphorus conservation under P-limitation, whereas subtropical species focused on nitrogen under N-limitation. The resorption of nitrogen and phosphorus in subtropical epiphytes was jointly regulated by both stoichiometric (maintaining elemental ratios) and nutrient limitation control strategies. In contrast, tropical epiphytes exhibited a tendency to rely solely on either a stoichiometric strategy or a nutrient limitation control strategy.

“Epiphytes and terrestrial plants demonstrate a comparable pattern of nutrient resorption, which may alleviate deficiencies in nitrogen and phosphorus. This adaptive plasticity likely underpins the astonishing biodiversity sustained by nutrient-poor canopy niches,” said LI Su of XTBG.

Rich epiphytes in Ailao Mountains National Nature Reserve in Yunnan. (Image by XTBG)

First Published: 04 March 2025