A combination of morphological and photosynthetic functional traits maintains the vertical distribution of bryophytes in a subtropical cloud forest

<p><span>The distribution and performance of bryophyte species are known to vary with vertical gradients, due to changes in environmental factors, especially light conditions. However, the morphological and physiological drivers of bryophyte distribution along forest vertical gradients are poorly understood. </span></p> <p><span><span><b>Methods</b><b>:</b> We conducted a comparative analysis of 28 morphological and photosynthetic functional traits in 18 species of mosses and liverworts distributed among three vertical microhabitats (ground, tree trunk, and branch) to analyze trait variance among the microhabitats and bryophyte life–forms in a subtropical cloud forest in Ailao Mountain, Yunnan, southwest China. Principle component analysis (PCA) was used to summarize trait differences among bryophyte species.</span></span></p> <p><span><b>Key Results: </b></span><span>In contrast to trunk and ground dwellers, branch dwellers tend to reduce light interception (smaller leaf and cell sizes, lower chlorophyll content); protect against damage from intense irradiation (higher ratios of carotenoids to chlorophyll); raise light energy utilization (higher photosynthetic capacity) and cope with lower environmental moisture conditions (pendant life-forms, thicker cell wall). Principal component analysis showed that ecological strategies of bryophytes in response to levels of irradiation were specialized in branch–dwellers, although those in ground and trunk–dwelling species were less distinct.</span></p> <p><b>Conclusions:</b> Environmental filtering shaped the functional traits combination and spatial distribution of bryophytes along the vertical gradients. Bryophyte species from  upper canopy of cloud forests show narrow  variation in functional traits under intense light , whereas species in the lower vertical strata associated with low levels of light intensity exhibited contrasting, but more diverse ecological strategies.</p>