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Takehisa Oikawa 경북대학교 환경과학연구소 1993 環境科學硏究所論文集 Vol.7 No.1
Primary production, which is the production by sutotrophic organisms, plays an essential role in all ecosystems. It determines the size and the activity of an ecosystem, depending on the flow of matter and energy from producers through herbivores to carnivores. Even humans, who are omnivores in an ecosystem, cannot escape this restriction. The princeipal ecosystems on land are forest and grassland ecosystems. As can easily be understood, forest ecosystems store a huge amount of organic matter mainly in woody parts. Whittaker and Likens (1973) estimated the total biomass of forests to be 1590 x 10'5 g d.w.; forest ecosystems, which occupy about 1/3 of the total land area, amount to about 87% of the total terrestrial biomass. In contrast, grassland ecosystems, including natural grasslands and arable lands, constitute a minor portion of the total biomass. Why then do humans depend on the major part of their food being produced not from arboreal crops, but from herbaceous crops? As is well known, the three major crops in the world are rice, wheat and maize. This question can be solved on the basis of mathematical models such as the one developed by Monsi and Saeki (1953), which gives primary productivity as a function of the physiological characteristics of leaves, the ecological characteristics of a plant community and an environmental parameter. A tentative hypothesis will be presented using their mathematical model.