The water relation of seedlings of Picea jezoensis on fallen logs

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We examined whether fallen logs without moss (FLB) are more drought-stressful sites for Picea jezoensis Carr. seedlings than are logs with moss (FLM) and whether drought affects the mortality of seedlings on logs. We measured the water potential of the log humus layer (Psi(H)) and needles of seedlings on the logs (Psi(N)) in a natural forest and a greenhouse under various drought conditions. We also determined the critical Psi(N) from the relationship between seedling mortality, Psi(N), and chlorophyll fluorescence, Fv/Fm. The Psi(H) on both moss-covered and bare logs in the forest was 0 MPa, regardless of the number of days without precipitation. In the forest, the mean predawn Psi(N) of FLB and FLM measured 11 days after a rainfall was -0.8 and -0.7 MPa, respectively, in the driest season. The Psi(N) for P. jezoensis seedlings of FLB reached the critical value earlier than those of FLM in the greenhouse, but this occurred after a long period (> 30 days) with no irrigation. We conclude that drought does not cause mortality of P. jezoensis seedlings on fallen logs in natural forests
NATL RESEARCH COUNCIL CANADAの論文