A Study On Nitrogen, Phosphorus Nutrient Use Efficiency And The Influence Mechanism Of Machilus Pauhoi Plantation

Machilus pauhoi is an excellent evergreen broad-leaved tree species in subtropical China. Plant size has been classified by the diameter at breast height (DBH) of in two M. pauhoi stands, i.e.,9 and 13 years old. The leaf stoichiometry characteristics relationships vary with plant size and relative growth rate of M. pauhoi biomass, and nutrient utilization mechanism of individual plants were analyzed. The main contents and results are as follows:The individual variations of seedlings in M. pauhoi stands were strengthened with the stand development. Average contents of leaf C, N, P in 9-year-old stand were lower than 13-year-old stand. Different growth season had significant effects on leaf N, P contents in two stands. And leaf N and P stoichiometry varied significant within Even-aged stand.There were complex relationships between plant size and leaf C, N, P stoichiometric characteristics. Leaf N, P contents, as well as their stoichiometric ratios, linearly correlated with DBH in the 9-year-old stand. On the contrary, leaf N, P stoichiometry showed quadratic correlation in 13-year-old stand. Date showed that large plant had stronger ability to adapt to impoverished environment than small one, in addition, the growth of M. pauhoi was constrained by P which is the limited nutrient of stands.The relative growth rate (RGR) level of individual in 9-year-old stand was higher, and rised with the increasing plant size, however, the opposite trend between RGR and plant size showed in 13-year-old stand. Leaf N, P contents, as well as their stoichiometric ratios, quadratically correlated with RGR in the 9-year-old stand. By contraries, leaf N, P stoichiometry showed linear correlation in 13-year-old stand. There were a consistent relationship between RGR and leaf stoichiometric characteristics in different aged stands when RGR was below 1.8 (mg/g/d).In even-aged stand, plant size had significant effects on leaf N, P nutrient resorption efficiency; as well as, leaf P-NRE were higher than N-NRE. In 9-year-old stand, the average value of N, P nutrient resorption efficiency was 35.8%、62.99%, and the average value of N, P nutrient resorption efficiency was 40.0%、64.82% in 13-year-old stand. The pattern of N, P use efficiency among different plant component showed leaf< branch<wood. Each component in different individuals of N and P use efficiency had consistency. Both of the stands, leaf, branch, wood N use efficiency and their P use efficiency that showed a significantly positive correlation; leaf N resorption efficiency and P resorption efficiency had significant positive correlation. N use efficiency between each component showed linear linearly correlation, the same was P use efficiency.Each component of plant N, P content was high but low nutrient use efficiency (i.e. YX2、AF4), is the excellent individual which could efficient utilization on N, P nutrient in two stands, especially in the P limited environment circumstances. Adequate supply in N, P nutrient condition, can play its nutrient utilization maximization of individual which had high level N, P content and nutrient use efficiency of each component.The number of bacteria, actinomycetes and fungi in rhizosphere soil were low and had significant differences between different individual plantations in two stands. In even-aged stand, soil nutrient and microbial structure had no obvious effect on nutrient use efficiency of plant.