Abstract
Epiphytic bryophytes are known to perform essential ecosystem functions, but their sensitivity to environmental quality and change makes their survival and development vulnerable to global changes, especially habitat loss in urban environments. Fortunately, extensive urban tree planting programs worldwide have had a positive effect on the colonization and development of epiphytic bryophytes. However, how epiphytic bryophytes occur and grow on planted trees remain poorly known, especially in urban environments. In the present study, we surveyed the distribution of epiphytic bryophytes on tree trunks in a Schima superba Gardn. et Champ. urban plantation and then developed count data models, including tree characteristics, stand characteristics, human disturbance, terrain factors, and microclimate to predict the drivers on epiphytic bryophyte recruitment. Different counting models (Poisson, Negative binomial, Zero-inflated Poisson, Zero-inflated negative binomial, Hurdle-Poisson, Hurdle-negative binomial) were compared for a data analysis to account for the zero-inflated data structure. Our results show that (i) the shaded side and base of tree trunks were the preferred locations for bryophytes to colonize in urban plantations, (ii) both hurdle models performed well in modeling epiphytic bryophyte recruitment, and (iii) both hurdle models showed that the tree height, diameter at breast height (DBH), leaf area index (LAI), and altitude (ALT) promoted the occurrence of epiphytic bryophytes, but the height under branch and interference intensity of human activities opposed the occurrence of epiphytic bryophytes. Specifically, DBH and LAI had positive effects on the species richness recruitment count; similarly, DBH and ALT had positive effects on the abundance recruitment count, but slope had a negative effect. To promote the occurrence and growth of epiphytic bryophytes in urban tree planting programs, we suggest that managers regulate suitable habitats by cultivating and protecting large trees, promoting canopy closure, and controlling human disturbance.
Highlights
Epiphytic or corticolous bryophytes grow on the bark of living trees and shrubs [1] and are found to be widely distributed from the northern forests in the northern hemisphere to the temperate forests in the southern hemisphere, including tropical forests
diameter at breast height (DBH) had a positive effect on the occurrence of epiphytic bryophyte, consistently with the findings reported by numerous previous studies [9,17,68]
Our results indicate that epiphytic bryophytes in urban environments prefer to colonize the shaded, humid parts of the trunk
Summary
Epiphytic or corticolous bryophytes grow on the bark of living trees and shrubs [1] and are found to be widely distributed from the northern forests in the northern hemisphere to the temperate forests in the southern hemisphere, including tropical forests. The colonization and subsequent development of epiphytic bryophyte diversity are regulated by factors at the tree, stand, and global scales [7,8]. Many studies have emphasized that the total tree height (H) [9], diameter at breast height (DBH) [10], canopy openness [11], age [12], and bark characteristics [13] are the driving factors of the diversity of epiphytic bryophytes. At the stand level, diversified microhabitats drive the development of epiphyte diversity that results from stand characteristics such as tree species composition [14], the continuity of the forest area [15], forest age [16], and tree density [17]. Most studies are conducted in native forest ecosystems, and relatively few studies involve urban forest ecosystems
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