International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.5, 229-239 http://ecoevopublisher.com/index.php/ijmec 23 2 Geographical factors such as altitude gradient and slope orientation also have an impact. Generally speaking, epiphytic plants are most abundant in the moist area at medium altitude. Low temperature at too high altitude and strong competition at too low altitude may both reduce the abundance of epiphytic plants (Suissa et al., 2021). In addition, the spatial pattern of forest landscapes also determines the spread and colonization of epiphytic plants. The spores or seeds of epiphytes need to spread from the source to new hosts. Over-isolated woodlands may lack epiphyte propagule sources, thereby reducing diversity (Paoli et al., 2020). 3 Ecological Adaptation and Functional Morphology of Epiphytes 3.1 Root system and water utilization strategies The epiphytic living environment determines that epiphytic plants develop unique strategies in water acquisition and storage. Because they are suspended in the tree canopy, epiphytes cannot directly draw water from the soil and can only rely on rain and fog precipitation as well as air humidity. The root system and water strategy of epiphytic plants embody the principle of "quick absorption and quick storage, slow consumption and water retention": limited water is quickly intercepted and stored through special root coverings, leaf tubes and water storage tissues, while unnecessary water loss is reduced through stomatal regulation and structural isolation. These adaptations ensure that epiphytes can survive in the canopy environment with intermittent and unstable water supply. The morphological diversity of different groups is precisely the result of their long-term adaptation to the water conditions of their respective microhabitats. For example, epiphytic ferns usually rely on curled leaves for rapid water absorption and cuticle for reduced transpiration, while epiphytic orchids rely on fleshy tissue and root cover (Garcia-Garcia et al., 2025). This diversity in functional morphology ensures that there are always epiphytes that can adapt to the local water conditions in the gradient from humid tropical cloud forests to seasonal arid forests (Hsu et al., 2024; Slate et al., 2024; Gao et al., 2025). 3.2 Nutrient acquisition mechanism Another major challenge for epiphytes is the source of nutrients. Because they are suspended in the air, epiphytes cannot absorb mineral nutrients from the soil. They must obtain limited elements such as nitrogen and phosphorus through multiple channels. The interception of rainwater and fog water is an important channel for nutrient input. Rainfall in the forest canopy brings trace amounts of dissolved nutrients. The accumulation and decomposition of fallen leaves are important sources of nutrients for epiphytic plants. Many epiphytic plants can capture the fallen leaves, branch shavings of the host tree, or their own withered organs, and accumulate them at the branches to form "canopy soil". This canopy soil is rich in organic matter and provides nutrients for epiphytes after decomposition by microorganisms (Victoriano-Romero et al., 2020). The special symbiotic relationship helps epiphytic plants obtain nutrients. The seeds of many epiphytic orchids are extremely small and lack endosperm, requiring symbiosis with mycorrhizal fungi for germination and nutrient absorption. Among them, the photosynthesis of algae and partial nitrogen fixation make lichenoid appendage a nitrogen source producer in the canopy (Slate et al., 2024). In addition, some epiphytic plants can obtain mineral elements from fallen dust. 3.3 Adaptation of epiphytic life types to light, temperature and humidity gradients There is a significant vertical environmental gradient within the forest: from the undergrowth to the canopy, the light gradually intensifies, the temperature rises and the air humidity decreases. Epiphytes, as users of the "vertical ecological gradient", exhibit diversity and functional differentiation that conform to this gradient (Dias-Pereira et al., 2022). Near the base of tree trunks and the lower branches under the forest, the light is weak but the humidity is high. Here, mosses, lichens and shade-tolerant epiphytic ferns thrive. The middle part of the trunk and the higher branches, with moderate light and humidity, are often the "territory" of epiphytic ferns and some orchids. Epiphytic ferns such as the Adiantum family thrive in semi-shaded environments. The topmost outer canopy is exposed to strong light, high temperature and relatively dry air. This is the stage for another set of epiphytes, including a large number of bromeliaceae, cactus epiphytes, and some sun-resistant orchids (Suissa et al., 2021). The temperature in the vertical gradient also affects the distribution of epiphytes: the upper part of the tree crown has a large temperature difference between day and night and a high daytime temperature. Epiphytes that adapt to this environment often have higher heat tolerance and resistance to sudden temperature changes. In terms of
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