Photoassimilation rates of sub-arctic moss and lichens species in pine ecosystems of the Central Siberia

Bryophytes and lichens usually dominate the ground floor layer of boreal forests and tundra, and contribute up to 50% of ecosystem gross CO₂ exchange (Bisbee et al. 2001; Goulden & Crill 1997). While Sphagnum spp. are the most important contributors in wetland C uptake, feathermosses and lichens play a significant role in drained habitats (Nilsson & Wardle 2005; O’Connell et al. 2003; Bjerke et al. 2013). Given their important ecological roles in such widespread biomes, it is surprising that still a few studies have attempted to understand the intrinsic factors that control moss-lichen cover carbon exchange dynamics specifically under ongoing climate change in high latitudes.

The aim of this work was to determine photoassimilation activity the widespread species of moss-lichen stratum during the growing season. The study has been conducted in Central Siberia near Zotino tall tower observatory (ZOTTO, 60 ° N, 89 ° E) in lichen- and feathermoss-dominated pine forests. The intensity of CO₂ photoassimilation of ground vegetation dominants (Cladonia stellaris O., Cladonia rangiferina L., Cetraria islandica L., Pleurozium schreberi W. ex B., Hylocomium splendens H., Dicranum scoparium H.) was determined in situ by infrared gas analyzer Walz GFS-3000 (Heinz Walz GmbH, Effeltrich, Germany) during the most part of a growing season (from June to September).

Bryophytes demonstrated more intense photosynthetic activity throughout the growing season. From June to September, among the studied moss species, the highest values of photoassimilation were observed for P. schreberi, and the lowest for H. splendens. The maximum values were recorded in August for all studied species and amounted to 4.36 ± 0.13 μmol / m² / s, and the lowest values were recorded in June to 1.4± 0.08 μmol / m² / s . Among lichens, C. stellaris was the most photosynthetically active, and C. rangiferina showed the least CO₂ photoassimilation rates. Moss-lichen layer dominants maintained relatively high photoassimilation activity throughout the growing season.

The research was funded by Krasnoyarsk Regional Fund of Science within the framework of the project № 2021 102007845  and RFBR, Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science, project number 44-243003.