Abstract:

Biomass, productivity, gross caloric value of fractions,ash free caloric value and the characters of the distribution and structure of energy in Casurina equisetifolia communities on homogeneous and red earth eolian sandy soil were studied in Dongshan County, Fujian Province. The results showed that the standing crop of biomass and energy of C. equisetifolia community were 15 681.84 g·m^-2 and 317 795.31 kJ·m^-2 on red earth eolian sandy soil, and they were 5 129.87 g·m^-2 and 105 751.40 kJ·m^-2 on homogeneous eolian sandy soil. On the homogeneous eolian sandy soil,the gross value of each fraction ranged 19.98 to 21.39 kJ·g^-1, of which dead branch gross caloric value was the highest, while root was the lowest, the percentage of energy of each fraction was 46.93% (truck)>16.44%(root)>13.92% (branch)> 12.28% (dead branch)> 5.87% (bark)> 3.90%(leaf)> 0.66%(fruit).The return amount of litter was 2 061.77 kJ·m^-2a^-1 and the net energy productivity was 31 298.70 kJ·m^-2a^-1 in 2002. While on the red earth eolian sandy soil,the gross value of fractions were 19.84～21.70 kJ·g^-1,among them leaf was the highest, and root was the lowest. The energy percentage of total of fractions were as follow: 38.09% (truck)>19.48%(branch)>17.09% (root)>16.86%(leaf)>6.83%(bark)> 0.88% (dead branch)>0.77% (fruit), the returned amount of litter was 9 070.47 kJ·m^-2a^-1, and the net energy productivity was 31 298.70 kJ·m^-2a^-1 in 2002. The standing crop of biomass and energy of C. equisetifolia community on red earth eolian sandy soil were higher than those on the homogeneous eolian sandy soil. The main reason to the different was that the sandy layer was thinner on the red earth eolian sandy soil (<20 cm) than that on the homogeneous sandy soil(>100 cm), during the life of tree, The main nutrient absorbed by tree came from soil, so the ability to supply nutrient and water of the red earth eolian sandy soil was better than that of the homogeneous eolian soil. But the average gross caloric value of the whole community on the homogeneous eolian sandy soil was higher than that on the red earth eolian sandy soil. That was because the crown density of the community on the red earth eolian sandy soil was higher than that on the homogeneous eolian sandy soil.

Key words: Energy, Casurina equisetifolia, Homogeneous eolian sandy soil, Red earth eolian sandy soil