EFFECTS OF CONTINUED PLATING OF CHINESE FIR ON THE FERTILITY OF SOIL AND THE GROWTH OF STANDS
Fang Qi (Forest Research Institue, Chinese Academy of Forest)
The continued planting of Chinese fir caused decrease in trees growth, druing 15 years old forest of the 2nd and 3rd times cultivation less 6.3% and 24.3% respectively in comparing with the first time cultivation. From the clear cutting of evergreen broad-leaf forests by burn and soil preparation to 15 years old the first time cultivation of Chinese fir forest caused the change of the soil fertility over three rotations as follows; the total amount of soil organic matter decreased by 45%; the total amount of N, P and K decreased by 38%, 42% and 32% respectively; the availability of N, P and K lessened 28%, 38% and 18% by order in rotations. The 3rd time cultivation of trees growing more slow, during the fast growing stage. Because the soil nutrients had been used in first two rotations. Therefore the stands of the 3rd cultivation was more open, thus influenced the ground vegetation, and the raising of soil nutrients, during the pole stage. There are about 174 specise in the stands of Chinese fir as undergrowth. The interspecific correlation coefficients of growth in every stands and in a certain stands showed Positive relation. Correlation coefficents of some species reached 0.4—1.0. In fact, continued planting of this species could not changed ecological environment for plant growth. The environmental conditions suitable for natural regeneration of subtropical evergreen borad-leaf forests and for the growth of many plants species also. If take effective steps to stop buring organic matter of the site, and carry out proper soil preparation in patches as well as control of water and soil erosion the site productivity can be maintained. Finally, accoding to physico-chemical properties of soil and topographical factors applied mathematical statisies forecasting stands periodical productivity of continued planting of this species significant value reached 0.81 of partial correlation coefficient.