Chain effect of attitude on epilithic moss distribution on rock faces in a subalpine region

Extensive exposure of rocks and slopes to natural disasters and human activities has resulted in significant ecological degradation, necessitating the quick and reasonable restoration of the ecological environment in areas affected by rock slopes. Mosses, especially epilithic mosses, have great potential for use in ecological restoration projects in mountainous areas because of their strong endurance and adaptability. The microenvironmental conditions of the rock surface, such as light, moisture, and temperature can affect moss growth and distribution. Individual rocks exhibit diverse surface attitudes that presumably induce variations in microenvironmental conditions, leading to significant variations in the distribution and growth of mosses across different rock faces. In this study, the effects of rock face attitude and microenvironment on the growth and expansion of subalpine epilithic mosses on rock faces were studied at the Jiuzhaigou World Natural Heritage Site in China. The results showed that in a humidity range restrained by natural precipitation, the higher the humidity, the better was the moss growth. The optimum humidity range for epilithic moss was 20 % to 60 %, whereas 20–60 µmol·m⁻²·s⁻¹ was the optimal light intensity. When the temperature exceeded 14 °C in the rainy season, mossy growth was better. The inclination of the rock face had a pronounced influence on the water, light, and thermal regimes of the rock surface. Regarding the rock-epilithic moss system in the subalpine area, a chain effect could be identified that the rock surface attitude affects the microenvironment, and the microenvironment further affects the moss growth. The key factors of the three links were inclination of the rock face, humidity, and moss biomass, respectively. As the rock face slopes downward, the microenvironment gradually becomes less conducive to plant growth owing to deteriorating environmental conditions characterised by reduced light intensity, humidity, and temperature.