Ecological studies on the self fertilization effects of trees.

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Primary productivities of forests depend upon the nutrient cycling between trees and environments. In these nutrients cycles, the litter fall is an important flux of nutrients into the soil, from where trees absorb the nutrients. The nutrient cycle by litter fall has been termed "the self fertilization effects of trees".Nutrient cyclings were studied in two plantation forests, i.e. Chamaecyparis obtuse and Cryptomeria japonica plantations in Kyoto and the following results were obtained through the study period. 1. Litter fall supplies were measured in the two plantations growing on two different soil conditions, over a two year period. 2. Seasonal changes in soil respiration rates were measured in the two plantations over a two year period and the total annual carbon dioxide evolution was similar between the two plantations. 3. Seasonal changes in nutrient contents of needles were measured over a two year period in the two plantations. 4. Decomposition processes of needle litter were followed over a two year period in the two plantations, and nutrients release largely depended upon the soil nutritional conditions. 5. Seasonal changes in nitrogen mineralization processes were followed over a two year period and the mineralization potentials were significantly higher in the Crypromeria forests.