Abstract:

Chinese fir and five exotic pines species Pinus elliottii Engelm., P. teada L., P. caribaea Morelet, P. rigida Mill., P. tropicatis Morelet were used in mixture expedment. The proportion of all mixed experimental plantations, except the control plot (pure Chinese fir plantation), was 66% Chinese fir plus 34% pines. The planting density 2 500trees/hm², all the seedlings used were 1-year-old planted in spring, in 1983.These mixed plantations were invesdgated 9 years later for their productivity, irradiance energy-use rate and nutrient-use efficiency and nutrient return rate in the nutrient cycling.The productivity and nutrient-use efficiency were the highest in the 66% Chinese fir plus 34% P. teada mixed plantation, its biomass amount reached 6.55t/hm²·a and producing biomass 73kg/hm²·a from each kg nutrient. The irradiance energy-use rate and accumulated bio-energy and nutrient return rate greatest in the 66% Chinese fir plus 34% P. caribaea mixed plantation, the total amount reached 3.97% and 17336kj/m²·a and 4.86%, respectively.The result of the comprehensive evaluation showed that: the scores of four items and tewlve categored from greatest to last are in due order: 66% Chinese fir plus 34% P. rigida plantation >66% Chinese fir plus 34% P. caribaea plantation > 66% Chinese fir plus 34% P. elliottii plantation > 66% Chinese fir plus 34% P. teada plantation (scored 71.6%) > 66% Chinese fir plus 34% P. tropicalis plantation > pure Chinese fir plantation.The result also indicated that p. rigid a and P. earibaea are the suitabler pine species to be mixed with Chinese fir in the central substropical area of China.

Key words: Mixed plantation, Resource-use, Irradiance energy-use rate, Nutrient return rate, Nutrient use efficiency