Soil Nutrient Characteristics of Rubber Plantations at Different Age Stages in Western Area of Hainan Island

In order to elucidate the soil nutrient characteristics of tropical rubber plantation ecosystem and evaluate the ecological benefits of the plantation and replantation of rubber trees in tropical areas, the nutrient characteristics in rubber plantations at 4 different age stages (2 year prophase of young trees, 7 year tapping young trees, 16 year tapping trees and 30 year mature age trees) in Danzhou zone of western Hainan Island were analyzed. The results showed that: (1) There were highly significant difference of SOM (soil organic matter) content at different age stages rubber plantations, and the content of tapping young trees (7 year)>mature age trees (30 year)> prophase of young trees(2 year)>tapping trees (16 year); and with the increase of soil depth on the 4 different age stages rubber plantations, the SOM content decreased gradually; (2) There were significant difference in TN (total nitrogen) concentration at different age stages rubber plantations, and the concentration of tapping young trees (7 year)>prophase of young trees (2 year)>mature age trees (30 year)> tapping trees (16 year), and with the increase of soil depth on 4 different age stages rubber plantations, the TN concentration decreased gradually, there was a significant positive relationship between TN and SOM (R² ≥ 0.6543, P＜0.001); (3) There were highly significant difference in TP (total phosphorus) concentration at different age stages rubber plantations, and all of which were extremely lower than that of the contrastive plots (Piper nigrum), and the prophase concentration of young trees (2 year)>tapping trees ( 16 year)>mature age trees (30 year)>tapping young trees (7 year); (4) There were highly significant difference in TK (total kalium) concentration at different age stages rubber plantations, and all of which were extremely lower than that of the contrastive plots (Piper nigrum), and with the increase of the ages of rubber plantations, the TK concentration decreased gradually, the TK concentration of the prophase of young trees (2 years)>tapping young trees (7 years)>tapping trees (16 years)>mature age trees (30 years). These data suggested that with the planting rubber trees in tropical areas, there was a downward trend of the soil fertility and nutrients, and it is necessary to increase fertilizers to maintain land productivity. These data set the important basis for the study of tropical land utilization/cover change affecting the global carbon cycle and the carbon-nitrogen coupling of rubber plantation growth, and which will offer theoretical bases for the rubber plantations in Chinese tropical areas.