Seasonal changes in photosynthesis of young Cryptomeria japonica growing on ridges and foot-slopes

Abstract

The influence of environmental factors affected by topography, especially light conditions in winter, on photosynthetic capacity of field-grown young Cryptomeria japonica trees was studied. Trees with a large increment in height growth tended to have current year needles with high photosynthetic capacity in the growing season. The change in the photosynthetic capacity from October to February, corresponding to the change in chlorophyll content, differed between trees planted near a ridge and on a foot-slope. There was a tendency for trees with a greater exposure to sunshine in winter, such as those near a ridge, to have a reduced chlorophyll content in winter. The photosynthetic capacity of 1-year-old needles of sample trees near a ridge did not recover as much as those on a foot-slope, even if the foliar nitrogen content was high. These results imply that the magnitude of winter injury on the photosynthetic apparatus differed according to the topographical conditions and strongly influenced the photosynthetic capacity during the next growing season.