Abstract: Calorific values of plants are important indices for evaluating and reflecting material cycle and energy conversion in forest ecosystems. Based on the data of larch (Larix spp) in northeast China,the calorific values (CV's) and ash contents (AC's) of different plant organs were analyzed systematically using hypothesis test and regression analysis in this paper. The results show: (i) the CV's and AC's of different plant organs are almost significantly different,and the order by AFCV (ash-free calorific value) from the largest to the smallest is foliage (21.57 kJ/g),branches (20.98 kJ/g),stem bark (20.73 kJ/g),root (19.88 kJ/g),and stem wood (19.51 kJ/g); and the order by AC is foliage (5.79%),stem bark (2.48%),branches (1.88%),root (0.95%),and stem wood (0.47%); (ii) the CV's and AC's of stem woods are increasing from lower to top sections of trunk,and those of top,middle and lower sections are significantly different; (iii) the CV's and AC's of roots are increasing from stump to large and small roots,and those between each pair are significantly different; (iv) the mean GCV (gross calorific value),AFCV and AC of aboveground part are larger than those of belowground part (roots),and the differences are also statistically significant; (v) the CV's and AC's of different organs are significantly related to diameter,height and origin of the tree,but the influence degrees of the factors on CV's and AC's are not the same.

Key words: gross calorific value, ash-free calorific value, ash content, hypothesis test, regression analysis, Larix