Traits of seven medicinal plants in Taihang Mountains and their responses to soil factors

In order to understand the trait differences of plants gradually formed during the process of adapting to the environment and their influencing factors, seven medicinal plants commonly found in Taihang Mountains were selected as the research objects, including Alkekengi officinarum, Houttuynia cordata, Artemisia argyi, Glechoma longituba, Lycium chinense, Lonicera japonica and Mentha canadensis. The plant photosynthesis, structural traits and soil physicochemical properties were measured to analyze the trait differences and their responses to soil factors. The results showed that among the seven medicinal plants, Mentha canadensis and Lycium chinense showed superior trait combinations, with higher photosynthetic rate and leaf dry matter content, and lower transpiration rate and specific leaf area; the root-to-shoot ratio of Lycium chinense was significantly higher than other plants. Spearman correlation analysis showed that leaf transpiration rate and stomatal conductance were significantly negatively correlated with leaf dry matter content and plant biomass per plant. There was a significant positive correlation between intercellular CO₂ concentration and leaf relative water content, while there was a significant negative correlation between water use efficiency and specific leaf area. The changes in the traits of the seven medicinal plants on Taihang Mountain slope mainly came from interspecific variation, with the variation coefficient of photosynthetic and structural traits ranging from 11.08% to 164.42%. Except for strong variation in plant biomass per plant and root-to-shoot ratio, all other traits showed moderate variation. The average intraspecific variation coefficient of different traits was 28.75%, which was at a low level. The RDA analysis of plant traits and soil factors showed that the sum of the explanatory rates of soil pH and clay content on plant trait variation was 72.30%, which was the main soil factor affecting the traits of the seven medicinal plants, and the soil conductivity was significantly positively correlated with soil pH and clay content. Through factor analysis, the organic carbon, total nitrogen, and C/N ratio were more correlated with the changes of the traits of Alkekengi officinarum, Mentha canadensis, Artemisia argyi and Lycium chinense, and the soil moisture was more correlated with that of Glechoma longituba. In summary, the traits of the seven medicinal plants were obviously different in Taihang Mountains, which could be affected by soil pH, soil particle composition, soil conductivity, and so on. Differentiated soil improvements should be carried out for specific plant varieties.