Organic nitrogen uptake is a significant contributor to nitrogen economy of subtropical epiphytic bryophytes

Abstract

Without any root contact with the soil, epiphytic bryophytes must experience and explore poor, patchy, and heterogeneous habitats; while, the nitrogen (N) uptake and use strategies of these organisms remain uncharacterized, which obscures their roles in the N cycle. To investigate the N sources, N preferences, and responses to enhanced N deposition in epiphytic bryophytes, we carried out an in situ manipulation experiment via the 15N labelling technique in an Asian cloud forest. Epiphytic bryophytes obtained more N from air deposition than from the bark, but the contribution of N from the bark was non-negligible. Glycine accounted for 28.4% to 44.5% of the total N in bryophyte tissue, which implies that organic N might serve as an important N source. Increased N deposition increased the total N uptake, but did not alter the N preference of the epiphytic bryophytes. This study provides sound evidence that epiphytic bryophytes could take up N from the bark and wet deposition in both organic and inorganic N forms. It is thus important to consider organic N and bark N sources, which were usually neglected, when estimating the role of epiphytic bryophytes in N cycling and the impacts of N deposition on epiphytic bryophytes in cloud forests.

Trait acclimation of the clonal fern Selliguea griffithiana to forest epiphytic and terrestrial habitats

“…The mean annual precipitation was 1859 mm, with 86% occurring in the wet season and 14% in the dry season. The mean annual relative humidity (RH) was 84%, and the mean air temperature was 11.6°C (Song et al, ). This forest is dominated by Lithocarpus xylocarpus , Castanopsis wattii , L. chintungensis , Schima noronhae , Machilus viridis , and Hartia sinensis .…”

“…The clonal facultative epiphytes, which can both grow in forest canopies (i.e., epiphytic habitats) and root in the understory soil (i.e., terrestrial habitats), are thought to have a strong plasticity in functional traits, that allows them to acclimate to distinct habitats (Freitas, Scarano, & Blesboer, ; Lu et al, ). Epiphytic habitats are characterized by a limited storage capacity for water and nutrients, sporadic and dilute nutrient inputs, low physical stability, extreme fluctuations in moisture and temperature, high wind speed, and severe and variable vapor pressure deficits (Lowman & Schowalter, ; Song et al, ; Théry, ; Zotz, ). However, how clonal facultative epiphytes acclimate to such contrasting environments has been poorly understood (Lu et al, ).…”

Vertical gradient in bryophyte diversity and species composition in tropical and subtropical forests in Yunnan, SW China

“…The Bubeng site is in tropical lowland seasonal rain forest (hereafter TRF) and the Xujiaba site in subtropical montane moist evergreen broad‐leaved forest (hereafter STF). Previous studies at Xujiaba have investigated the impact of bryophytes on the amount and nutrient composition of stem flow (Liu et al., ), bole bryophyte diversity in old‐growth and secondary forests (Ma et al., ; Song, Liu, Ma, & Zheng, ), water and nitrogen relations of bryophytes (Song, Ma et al., ; Song, Zhang et al., ; Song et al., ), and the responses of bryophytes to simulated nitrogen deposition and climate change (Shi et al., ; Song, Liu, Ma, & Qi, ; Song, Liu, & Nadkarni, ).…”

Ecological stoichiometry of the epiphyte community in a subtropical forest canopy

“…Although the nutrient sources of epiphytes and their adaptations to canopy habitats were identified in previous studies (Hietz et al, 1999;Song et al, 2016;Zotz & Hietz, 2001), the nutrient status and adaptations of the entire epiphyte community remain unclear.…”