Variations of wood delta(13)C for the past 50 years in declining Siebold's beech (Fagus crenata) forests.
Markedly damaged stands have been observed in Siebold's beech (Fagus crenata) forests on the Tanzawa Mountains, Japan, which are located close to densely populated and heavily industrial areas. We measured the delta(13)C records for the past 50 years (1944-1997) in wood cellulose sampled from relatively healthy trees in declining forests on Mt. Hinokiboramaru (1600 m). This may provide information on the history of stresses related to environmental changes, which have caused the decline symptoms. The results showed that, for all of the trees studied, wood delta(13)C has decreased with time. Also, the difference in delta(13)C among trees grew abruptly after the mid-1960s, which almost coincides with the time when the decline symptoms were markedly observed. Some trees with large reduction of wood delta(13)C exhibited the strong decreases in radial growth. This suggests that the reduction of tree growth may have been more greatly influenced by decreasing carboxylation rate than by stomatal limitation. It is unlikely that water stress and SO(2) and O(3) stresses have induced the growth reduction, because those stresses cause increasing wood delta(13)C. This is supported by the facts that wet conditions and relatively low SO(2) and O(3) levels have been observed near Mt. Hinokiboramaru. In addition, analyses of wood Ca showed no evidence that acid fog and soil acidification have affected the wood delta(13)C and growth through effects on the nutrient uptake of trees. However, what type of stresses have induced the large reduction of wood delta(13)C and growth for some of the trees studied remains unknown because of the lack of sufficient data for evaluation. In contrast, lesser reduction of wood delta(13)C from the other trees may be related to an increase in the plant water-use efficiency with increasing atmospheric CO(2) concentration.
Sakata
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Komae Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 2-11-1 Iwato-kita, Komae, 201-8511, Tokyo, Japan
Suzuki
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K
Koshiji
T
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