倒木上のコケの高さがエゾマツ実生の生残と成長に与える影響  [in Japanese] The Effect of Moss Height on Survival and Growth of Picea jezoensis Seedlings on Fallen Logs  [in Japanese]

倒木上のコケの高さがエゾマツ実生の生残と成長に与える影響を明らかにするため,コケがない倒木(FL_B),コケが低い倒木(FL_S),コケが高い倒木(FL_T)を対象に播種実験を行い,エゾマツ実生の発芽率と生残率,形態ならびに根の分布,各器官重を調査した。発芽率はFL_Tで有意に小さく,生残率は倒木間で差がみられなかった。コケの高さや実生の生残・枯死によらず,実生の主根の大部分は腐植層や材部に分布していた。当年生実生の個体重はFL_T上で最も小さかったが,FL_T上の実生は他の倒木の実生より幹が長く,幹へ多くの器官量配分を行っており,高いコケによる被陰に対し形態および器官量配分による順応を行っていたと考えられた。1年生実生の個体重はFL_SよりFL_B上の実生が小さかった。FL_B上の1年生実生の根長が有意に短く,T/Rが高かったことから,FL_Bでは1年生時の根の伸長が制限され,個体の成長が抑制されたと考えられた。エゾマツの発芽および定着にはFL_Sが適していると考えられた。

We surveyed the germination and survival rates, morphological characteristics, spatial pattern of root extension, and the mass distribution into each organ of current and 1-year-old Picea jezoensis seedlings growing on fallen logs with no moss (FL_B), short moss (FL_S), and tall moss (FL_T) in a natural coniferous forest in central Hokkaido, northern Japan, in order to estimate the influence of moss height on the establishment of P. jezoensis seedlings on fallen logs. The germination rate was significantly lower on FL_T than on the others. The survival rate of seedlings did not differ among the logs. Almost all parts of the tap roots of living and dead seedlings were distributed in the humus and wood layers of the logs, irrespective of moss height. Seedlings on FL_T had longer stems and greater stem masses than seedlings on the other logs, which indicated their morphologic and allometric acclimation to shading from the tall moss. The masses of individual current-year seedlings were lower on FL_T than on the others. The masses of individual 1-year-old seedlings were lower on FL_B than on FL_S. The root extension of 1-year-old seedlings on FL_B was inhibited and resulted in shorter roots and a higher T /R ratio. Consequently, the growth of 1-year-old seedlings on FLB was inhibited. Therefore, FL_S is the most suitable for the establishment of P. jezoensis seedlings.