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Epiphytes, including lichens, bryophytes, ferns and spermatophytes, are a large and widely distributed group across many forest ecosystems. Acquiring enough nitrogen (N) to support their life processes in nutrient-poor canopies is a crucial challenge for epiphytes.

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences employed stable isotope analysis to explore N acquisition and differentiation among co-occurring epiphytes in Ailaoshan subtropical forest in Yunnan Province.

The study was published in .

The researchers collected materials from epiphytic cyanolichens, chlorolichens, bryophytes, and vascular epiphytes and potential N sources (phorophyte leaves, litterfall, canopy soil, ground soil, and precipitation) in similar microhabitats in secondary patches within primary forests.

They analyzed and compared the N concentrations and δ¹⁵N of the collected materials. Results suggested that functional group was the most important factor that could affect δ¹⁵N and N of epiphytes, reflecting differences in N acquisition, uptake and utilization strategies among different groups.

"Atmospheric or within-canopy-derived N was more important than soil-derived N for epiphyte growth," said Li Su from XTBG, corresponding author of the study.

Analysis of δ¹⁵N enrichment factors confirmed the involvement of various N sources in nutrients of epiphytes, leading to differentiation in N utilization among different epiphyte groups. Cyanolichens mainly acquired N through N₂-fixation, while chlorolichens relied more on rainwater N. Bryophytes obtained considerable N from N fixation and ground soil, while vascular epiphytes acquired N from a wide range of sources, including ground soil, phorophytes and precipitation.

"Our study has shed light on differentiation in N sources of co-occurring epiphytes in Chinese subtropical forests and this could be one of the most important reasons for the survival of abundant epiphytes within nutrient-poor canopies," said Li.