Nutrient resorption, a 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. It is assumed to be crucial for epiphyte growth in nutrient-poor canopies, yet remain poorly understood due to unique habitats and limited access.

A study published in Plant, Cell & Environment and conducted by researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences highlighted how nutrient resorption processes enable epiphytes to persist in canopy environments where soil-derived nutrients are inaccessible, shedding light on leaf nutrient resorption characteristics of vascular epiphytes.

Researchers analyzed nitrogen and phosphorus concentrations and nitrogen isotope composition (δ¹⁵N) in mature and senescent leaves from 10 subtropical epiphyte species in Ailao Mountains National Nature Reserve in Yunnan, China. They compared nitrogen and phosphorus resorption efficiencies and regulatory patterns across climates based on data of prior research on tropical lowland forests.

Researchers found that 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 nitrogen 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 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 nitrogen and phosphorus deficiencies. This adaptive plasticity likely underpins the astonishing biodiversity sustained by nutrient-poor canopy niches,” said LI Su from XTBG, the corresponding author of this study.

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