Analysis on the absorbing, transfer, restoration and adaptation mechanism of calcium in different peak forest plants in northern Guangdong Province，China

Thirty kinds of karst peak forest plants in the Shijiao village，Jiulong town，Yingde City， Guangdong Province（N24°08.113′,E112°51.855′, altitude, 121 m,height of hill 80 m）were selected as the object of quantitative analysis to reveal their adaptation to the karst soil environment rich in calcium. The measured variable included the total calcium content of rhizosphere soil, and root, stem, leaf and litter in different plants. The characteristics of utilization, store, and returning soil of calcium in different plants were analyzed based on the absorption coefficient, transfer rate, and return rates. In addition, adaptation mechanism for karst soil in different plants was classified based on the result of cluster analysis. The results show that,（1）The significant positive correlation between the total calcium content in plants and in rhizosphere soil shows the plants in karst peak forest have a good adaptation to karst soil. But the absorption coefficients have large differences among the different plants. The total calcium absorption coefficient of climbing plants is 1.21 times,1.22 times, and 1.30 times of trees, small shrubs and herbs, respectively. It means the climbing plants have a better adaptability to the karst environment.（2）There are large differences of total calcium in different living types of plants in the leaf, stem, and root, of which the average total calcium content are 1.08 times,1.07 times 1.17 times of trees, respectively, and 1.39 times and 1.82 times of herbs in leaf and root, respectively. The total calcium content has a tendency of root＞leaf＞stem.（3）The litter is the main way through which calcium in plants returns to the soil. The rates of 30 kinds of karst peak forest plants are between 22.06%-103.84%, among which herbs has the biggest rate, and tree has the second, and shrubs has the smallest, which are 67.18%,58.72%, 55.90%, respectively. (4)The results of cluster analysis based on the total calcium content of rhizosphere soil, root, stem, leaf, and litter show different adaptation ways of plants to karst soil, which are classified into four categories, abundant calcium-high absorption-low restoration, few calcium-low absorption-high restoration, more calcium-high absorption-medium restoration, and more calcium-medium absorption-medium restoration. There are 26 kinds of plants belong to the last one, implying that the most of plants in karst peak forests have a good adaptation to the karst high-calcium environment through continual absorption, steady accumulation and high-rate restoration.