Elevational trends in photosynthetic capacity and trait relationships of subtropical montane understorey bryophytes

Abstract

Bryophytes respond sensitively to environmental variation and the functioning and functions of bryophyte communities may therefore change due to climate change. However, how bryophyte functional traits and trait relationships vary with environmental variation is not well known. Therefore, we investigated elevational trends in photosynthetic traits and their relationship with nitrogen and phosphorus contents (N and P) for 19 moss species on the eastern slope of Gongga Mountain, China. As tissue N contents were previously shown to decrease with elevation, we expected net photosynthesis (Amax) and dark-respiration rates (Rd) to show similar decreasing trends. Contrary to our expectations, no significant trend for Amax in relation to elevation was found and Rd peaked at the middle elevation, while the slopes of the relationship of Amax with N were similar along elevations but differed from those found previously for bryophytes at two other sites on the Tibetan Plateau. Our results suggest that: 1) unlike for vascular plants, for bryophytes elevational trends in nutrient contents have limited predictive power for photosynthetic traits; 2) functional-trait relationships for bryophytes can differ between geographical locations. Therefore, care should be taken when using easy-to-measure traits like nutrients to predict bryophyte functioning. More detailed modelling than for vascular plants may be needed to account for the alternative solutions bryophytes use to adjust to their environment.

Keywords

• Allometric scaling
• Bryophytes
• Functional traits
• Photosynthesis
• Subalpine