Redistribution effects of tree canopy of the artificial Pinus tabulaeformis forest on precipitation in the upper stream of Minjiang River

The experiment was conducted in the 23\|year\|old artificial Pinus tabulaeformis forest in the upper stream of Minjiang River in order to evaluate its service function in water preserving capability.Total 136 precipitation cases from September 2002 to September 2003 were monitored and redistribution and interception effect of the tree canopy on precipitation was analyzed.Of total 805 8 mm precipitation,canopy interception,step\|flow,throughfall of the forest were 297 892,66 771,440 137 mm,which account for 36 97%,8 41%,54 62% of the total precipitation,respectively.Only when precipitation was over 0 3 mm and over 2 8 mm throughfall and stem\|flow could be recorded respectively.The capability of canopy interception and redistribution on precipitation was closely related with amount and existing conformation of precipitation and stand characteristics.The stem\|flow and throughfall was positively correlated with precipitation amount,but canopy interception rate was negatively related with precipitation amount by logarithm and stemflow rate and throughfall rate of the forest were positively correlated with precipitation amount by logarithm.In the forest,interception capability by tree canopy on snow was much stronger than on rainfall and the throughfall amount on snow much weaker than on rainfall.Under the same precipitation the stemflow increased with the increase of tree diameter in breast height.An interesting finding in the study was that water absorbing capability of pine needles also played a definite role in precipitation interception.Compared with same pine forest in other regions of China the 23\|year\|old artificial Pinus tabulaeformis forest in the upper stream of Minjiang River had higher interception capability due to differences both in precipitation and in stand features.