Abstract:Soil carbon, nitrogen and phosphorus ecologic measurement ratio reflects the content of limiting elements in soil, which can provide theoretical basis for land balance management and plant growth. The effects of lithology and planting years on the ecological stoichiometry of soil carbon, nitrogen and phosphorus is still not clear.Methods: In this study,we collected soil from different lithology background (dolostone, clastic rock) and fixed number of year (1, 3, 5 a) in Yexu Dragon Fruit Plantation , Taiping Town ,Pingguo County, Guangxi.Correlation analysis and redundancy analysis were employed to discuss the ecological stoichiometric characteristics of carbon, nitrogen and phosphorus in 0~80cm soil under different lithologic backgrounds and planting years.Results:The results show that:(1) The total phosphorus content in dolostone area was significantly higher than that in clastic rock area, while the soil organic carbon content, C/N, C/P and N/P in dolostone area were significantly lower than that in clastic rock area.The ecological stoichiometric ratios (5.96, 11.78, 1.96 and 8.71, 19.78, 2.28) in dolostone and clastic rock backgrounds are far lower than the national level.(2) The contents of soil organic carbon, total nitrogen and C/N, C/P, N/P increased with increasing of planting years, while the contents of soil available nitrogen, total phosphorus and available phosphorus showed no significant change. Soil organic carbon, total nitrogen, available nitrogen and C/N, C/P, N/P increased as the soil get deep, while soil total phosphorus content had no obvious change pattern.(3) Soil C/N and C/P were positively correlated with soil organic carbon and available nitrogen (P<0.01), but negatively correlated with soil moisture and bulk density, and soil N/P was negatively correlated with total phosphorus.(4) Redundancy analysis showed that soil available nitrogen content was an important factor influencing soil C, N, P and its ecological stoichiometric ratio under different lithologic background and planting years, which showed a significant positive correlation (P<0.01).Conclusions:The growth of pitaya fruit under the dolostone background was more affected by nitrogen elements than where under clastic rock background. Long- term planting of pitaya fruit was beneficial to the retention of carbon and nitrogen elements, and soil available nitrogen content was the key factor affecting soil carbon, nitrogen and phosphorus and its ecological stoichiometric ratio.