Abstract
Epiphytic lichens are an important component in subtropical forests and contribute greatly to forest biodiversity and biomass. However, information on epiphytic lichens still remains scarce in forest conservation owing to the difficulty of accessing all canopy layers for direct observation. Here, epiphytic lichens were quantified on 73 whole trees in five forest types in Southwest China to clarify the vertical stratification of their biomass in subtropical forests. Lichen biomass was significantly influenced by forest type and host attributes, varying from 187.11 to 8.55 g∙tree−1 among forest types and from 289.81 to <0.01 g∙tree−1 among tree species. The vertical stratification of lichen biomass was also determined by forest type, which peaked at the top in primary Lithocarpus forest and middle-aged oak secondary forest and in the middle upper heights in other forests. Overall, the proportion of lichen biomass accounted for 73.17–100.00% of total lichen biomass on branches and 0.00–26.83% on trunks in five forests, and 64.53–100.00% and 0.00–35.47% on eight host species. Seven functional groups showed marked and various responses to tree height between and among forest types. This information improves our understanding of the distribution of epiphytic lichens in forest ecosystems and the promotion of forest management in subtropical China.
Highlights
Epiphytic lichens grow on branches and trunks of trees, sometimes with heavy cover, in many forest ecosystems
Our study showed that epiphytic lichen biomass ranged from 8.55 to 187.11 g·tree−1 in the subtropical Ailao Mountains
These data are low compared with the data from temperate/boreal oak woodland (545 g·tree−1 [12]) and coniferous forests (47–31,300 g·tree−1 [13,14,15,16,18,22,23,24,25,30]). When these data are considered in combination with the host density [37], a crude approximation for lichen stand-level biomass was 71 kg·ha−1 in the primary dwarf mossy forest (PDMF), 150 kg·ha−1 in the PLF, 1105 kg·ha−1 in the middle-aged oak secondary forest (MOSF), 862 kg·ha−1 in the Populus bonatii secondary forest (PBSF), and 1180 kg·ha−1 in the Ternstroemia gymnanthera secondary forest (TGSF), falling within the high range of those reported in hardwoods (100-1800 kg·ha−1 [10,12]), tropical rain forest (7 kg·ha−1 [46]), and coniferous forests (120-4700 kg·ha−1 [10,13,14,17,18,20,21,22,24,25,47])
Summary
Epiphytic lichens grow on branches and trunks of trees, sometimes with heavy cover, in many forest ecosystems. They can contribute greatly to biodiversity and may constitute a large proportion of epiphyte biomass [1,2]. Epiphytic lichens have been documented to be indicative of forest community health, conservation and management, environmental changes, human disturbance, and air pollution [1,2]. Despite the remarkable contribution of epiphytic lichens to forest ecosystem, their biomass is difficult to assess directly because canopy surveys require difficult means of access, and the removal of lichens from bark is a very time-consuming task [3]. The indirect method of measuring litterfall is practicable for assessing epiphytic lichen biomass, but it is not without problems due to the fact that litterfall varies with wind, Forests 2017, 8, 436; doi:10.3390/f8110436 www.mdpi.com/journal/forests
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