A comparison between the productivity of Pinus rigida which is native in the Eastern United States, and P. rigitaeda which is F_1 hybrid between P. rigida and P. taeda, has been established. For each tree the diameter at breast height(D) and the heigh...
A comparison between the productivity of Pinus rigida which is native in the Eastern United States, and P. rigitaeda which is F_1 hybrid between P. rigida and P. taeda, has been established. For each tree the diameter at breast height(D) and the height of tree(H) were measured in three years. The standard sample trees were felled down and then weighed each organ. From obtained data the allometric relation between D^2H and dry weight of the trunk(Ws), the branches(Wb) and the leaves (Wl) of P. rigide were approxmated by Ws=0.0592 (D^2H)^0.837 Wb=0.0065 (D^2H)^0.989 Wl=0.0447 (D^2H)^0.690 and those of P. rigitaeda were approximated by Ws=0.0522 (D^2H)^0.843 Wb=0.0037 (D^2H)^1.117 Wl=0.0207 (D^2H)^0.865 From the above, the standing crops of above ground of P. rigida were estimated to be as much as 16.93-34.35 ton dry matter per ha. and those of P. rigitaeda were 20.45-45.55 ton per ha. Annual net production was appraised at 8.07-9.35 ton/ha·yr in P. rigida and at 11.59-13.41 ton/ha·yr in P. rigitaeda (1.0 : 1.4). It is assumed that high productivity of P. rigitaeda stand compared with P. rigida was resulted from an increase of the leaf amount with age. Photosynthetic ability under the saturated light of the current and the old leaves of P. rigida were respectively 2.62 and 0.06 ㎎ CO_2/g. d. wt.·hr and those of P. rigitaeda were 1.17 and 0.96 ㎎ CO_2/g.d. wt.·hr. Respiration of the current and the old leaves at 25℃ were 1.00 and 0.90 ㎎ CO_2/g. d. wt.·hr. in P. rigida and 0.90 and 0.45 ㎎ CO_2/g. d. wt.·hr in P. rigitaeda. It is assumed that photosynthetic longevity of P. rigitaeda leaves was vigorously maintained longer than that of P. rigida.