SOIL NUTRIENTS DYNAMICS IN BROADLEAVED FOREST AND CHINESE FIR PLANTATIONS IN SUBTROPICAL FORESTS

Abstract

This study explored how soil nutrients are affected by the monoculture Chinese fir (Cunninghamia lanceolata) plantation and natural broadleaved forest. A total of 11 different age classes of Chinese fir at four rotations were investigated. Five quadrats were selected in each age class in which three pits were dug in each quadrat at five depth intervals. In each sample plot, a total of 75 samples were collected. Composite soil samples were analysed for total and available nitrogen (N), phosphorus (P) and potassium (K). Results showed that amount of soil nutrients was significantly lower in Chinese fir plantations than in natural broadleaved forests. Soil depth and age of plantations significantly influenced soil nutrients. Further, total N, P, K, NH₄⁺-N, available P and available K decreased as the number of rotations increased. Successive cultivation of Chinese fir plantation led to decline in the amounts of soil nutrients in the plantations compared with those of natural broadleaved forest stands.