Altitudinal variation in leaf traits of Castanopsis eyrei and their relationship to soil chemical factors

To reveal adaptive mechanisms of leaf traits of Castanopsis eyrei to different altitude gradients, and to provide a theoretical basis for the ecological conservation and rational utilization of C. eyrei.

C. eyrei in Hunan Nanshan park was taken as the research object, and the changes in leaf morphology, physiological and biochemical traits along the altitude gradient (500, 750, 950, 1 170 m) and their relationship with soil chemical factors were explored.

The results showed that with the increase of altitude, the leaf length, leaf width, leaf area, leaf mass, relative water content, and chlorophyll content all decreased, while leaf thickness, conductivity, content of malondialdehyde, proline, soluble sugar, activity of POD and SOD showed all increased. The leaf area of C. eyrei was the largest, and the leaf thickness, malondialdehyde content, proline content and antioxidant enzyme activity were the lowest in the region of low altitude 500-750 m, and the differences were not significant. The total phosphorus content and pH value of soil decreased with increasing altitude, while the total nitrogen, alkali hydrolyzed nitrogen, and total potassium content of soil show opposite trends. The redundant results showed that the main soil chemical factors affecting the leaf morphological, physiological, and biochemical variations of C. eyrei on altitude gradients were total potassium, total nitrogen, and pH value. The overall plasticity of leaf physiological and biochemical traits was higher than that of leaf morphology, and the plasticity of malondialdehyde, electrical conductivity, chlorophyll and leaf thickness were the highest.

The region of low altitude 500-750 m was the most suitable area for C. eyrei, and the plasticity of physiological and biochemical characters such as chlorophyll, osmotic substances and antioxidant enzymes played a very important role in its adaptation to higher altitude environment.