Bryophytes are the earliest land plants and lack the supracellular transport systems of vascular plants. Epiphytic bryophytes usually dominate the tree trunks and branches in montane forests on moist, undisturbed sites. Due to their particular biological nature (no cuticle barrier, lacking roots and developed vascular systems, and growing on bark, etc.) and special habitats (poor, patchy, and heterogeneous in N supply), epiphytic bryophytes are likely to have different nitrogen (N) uptake and use strategies under natural conditions and under increasing atmospheric N deposition.
Prof. LIU Wenyao and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a multifactor in situ manipulation experiment via the 15N labelling technique in three coexisting and common epiphytic bryophyte species in the Ailaoshan subtropical cloud forest in SW China. They aimed to determine whether epiphytic bryophytes can take up N from tree bark or bark surface and to confirm the capacity of epiphytic bryophytes to absorb organic N and quantify its amount in the total N economy of the bryophytes. They further wanted to address the potential impact of increased N deposition on the N uptake dynamics of epiphytic bryophytes.
The 15N enrichment in the epiphytic bryophyte shoots suggested that the epiphytic bryophytes can acquire N from the bark and translocate it to their shoots via various pathways, e.g. passive diffusion, endophytic fungi, bacteria. The contribution of organic N (glycine) ranged between 28.4% and 44.5% of the total N uptake, which was comparable with NH4+, but significantly higher than NO3− . No significant differences were detected for the acquisition of different N forms between air deposition and bark injection for all three epiphytic bryophyte species, which demonstrated that those organisms did not shift their N preference from air to bark N sources. Increased N deposition increased the total amount of N absorbed by the epiphytic bryophytes, but it did not alter the N preference over a short time.
The study highlighted that organic N, as opposed to inorganic N, contributed remarkably to the N economy of the epiphytic bryophytes. High N loads may result in excessive N uptake, which may induce biochemical disorders in bryophytes. Thus, it is important to consider organic N and bark N sources when estimating the role of epiphytic bryophytes in N cycling and the impacts of N deposition on epiphytic bryophytes in cloud forests.
The study entitled “Organic nitrogen uptake is a significant contributor to nitrogen economy of subtropical epiphytic bryophytes” has been published in Scientific Reports.
Contact
LIU Wenyao, Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
Tel: 86-871-65153787
E-mail: liuwy@xtbg.ac.cn
