Soil samples were collected from primary forest,natural secondary forest,Pinus caribaea and Acacia mangium stands in Baisha County,Hainan Province,for the determination of soil chemical properties including soil pH,organic matter,total and available N,P and K.The effects of soil layers and forest stands on soil chemical properties were compared.Results showed that forest soils in the studied area were strong acidic,with slight or moderate deficiency of available P,and moderate deficiency of available K(except the primary forest).The highest contents of soil total and available nutrients except for available P and total K were found in the primary forest,followed by natural secondary forest and Acacia mangium stands,and the lowest in Pinus caribaea stands.In soil layer A,except for total N and available P,significant differences were found for organic matter content and very significant differences for soil pH,hydrolyzable N,total P,and total and available K among the four types of forest stand.Similar trend was true for soil layer B.Correlation analysis indicated that soil organic matter content affected the total and available N,P and K in different manner.Soil organic matter had very significant or significant correlation with total N,and significant correlation with hydrolyzable N(only in soil layer B) in primary and natural secondary forests.Significant correlations beween organic matter and total N and P were found in Pinus caribaea stands,but no significant correlations between organic matter and soil nutrients existed in Acacia mangium stands.Some suggestions on forest management were also proposed to improve forest soil quality.
