Research On Ecological Stoichiometry Characteristics Of Five Different Tree Species In Wanchuan Ecological Park

This study was carried out in Wanchuan ecological park in Jurong City, we took Osmanthus?Classic?Hackberry?Caphura and Pirumas as the research objects, and collected the leaves and soil of the five different tree species in different seasons(April, July, October and January).Meanwhile, we also collected the litter of the trees in autumn and winter. We determined the contents of C?N and P in leaves and soil of the five tree species in their different growing seasons, and the contents of C?N and P in the litter of the trees. Through this study, we analysed the change regulations of the C?N?P content and stoichiometric of the leaves and soil of the different trees with the change of seasons. We discussed the nutrient cycling mechanism in leaves?soil and litter. The results are follows:(1) From the perspective of the annual average, we found that except for Classic(whose ratio of N: P was greater than 16)the ratio of N: P in the other four different species of trees in the study area were all less than 14,so we concluded that N is the restrictive factor for Osmanthus, Hackberry, Caphura and Pirum,and P is the restrictive factor for Classic. Therefore N fertilizer should be timely supplement in this place to meet the nutritional needs of the normal growth of Osmanthus, Hackberry, Caphura and Orbis, P fertilizer should timely be supplement in this place to meet the nutritional needs of the normal growth of Classic.(2) From the individual level, the contents of C?N and P in the leaves and soil of five different species of trees were changed with different seasons, and there were significant differences between four seasons. The variation trends of the contents of C?N and P are not the same with different seasons, which showed that the content of nutrient elements in the leaves of the plant was greatly influenced by the genetic factors, in which the variation trends of Osmanthus and Classic are the same, and the variation trends of Hackberry?Caphura and Pirumas are similar, which may be related to the biological characteristics of the five species. Among them the Osmanthus and Classic are belong to evergreen species, while Hackberry?Caphura and Pirumas belong to perennial deciduous trees. The relationship of the leaf C:N between each tree species was Osmanthus> Pirumas >Hackberry>Caphura>Classic. According to the difference analysis, the utilization efficiency on N of Osmanthus is higher than Caphura and Classic.The relationship of the leaf C:N between each tree species was Classic>Osmanthus>Pirumas> Hackberry> Caphura. According to the difference analysis, the utilization efficiency on P of Classic and Osmanthus is higher than Hackberry and Caphura. Although there were differences in the seasonal variation of soil and leaf among the five species, the seasonal variation of C?N?P content in soil was opposite to that in leaf. The results showed that the leaf nutrient came from the soil, and there was a certain coupling relationship between soil nutrient and leaf nutrient.(3) Under the same site conditions, the contents of C?N?P and the chemical characteristics of the soil were different among five tree species. But when compared with the average level of soil nutrients in the whole country, they were all higher, and the quality of soil was higher. The relationship of C content wasphura>Pirumas>Hackberry>Osmanthus >Classic; the relationship of N content was:ckberry>Classic>Pirumas>Osmanthus>Caphura; the relationship of P content was:assic> Osmanthus?Hackberry?Caphura > Pirumas; the relationship of C:N was: Caphura >Pirumas >Osmanthus> Classic> Hackberry; the relationship of C:P was: Caphura> Pirumas> Osmanthus?Classic?Hackberry. So it can be inferred that the different vegetation types was one of the important reasons for the differences of C?N and P nutrient contents in soil. According to the results of the difference analysis we could judge the forest productivity of Caphura was significantly higher than that of Osmanthus and Classic, Classic and Hackberry kept higher nutrient pool of total N while nutrient pool of total N of Caphura was low. At the same time Classic also kept high nutrient pool of total P, but the nutrient pool of total P of Pirumas was low, and the rest of the tree species were maintained at a moderate level.(4) Based on the analysis of the nutrient elements and the stoichiometric ratio of leaf and soil of five different species of trees in the study area, the results showed that except for Caphura that the relationship between N and P content is negative, the rest showed a positive correlation. In addition, the correlation of Osmanthus and Hackberry was significant, and the others were not significant, which has a certain difference with the conclusions of previous studies. This phenomenon may be because of that the research area was an ecological sightseeing garden, which often subjected to human interference, so it leads to the different phenomena in the process of plant growth; The C:N and N, C:P and P of five species of trees showed extremely significant negative correlation(P<0.01), with the increase of the content of N and P, the value of C:N and C:P reduced gradually, and we could fit the relationship between the them by a linear equation. There was a significant positive correlation between the contents of N and P in the soil of the five tree species(P<0.01), which was consistent with the previous research results. In the soil of five different tree species, except for Hackberry that is uncorrelated, the others all showed a significant or extremely significant negative correlation between N content and C:N(P<0.05,P<0.01), in addition, there had a significant correlation of the relationship between C:P and P content of Hackberry, and others had extremely significant correlation(P<0.01), with the increase of the content N of and P, the value of C:N and C:P reduced gradually.