SREL Reprint #0269




The dynamics of dry matter and chemical substances
in a Juncas effusus population


Claude E. Boyd
Savannah River Ecology Laboratory, P O Drawer E, Aiken, SC 29802

Seasonal changes in standing crops of living and dead dry matter and tissue levels of chemical substances were determined for a Juncus effusus population. These data were used to determine rates of production, pigment synthesis and nutrient absorption during different parts of the annual growth cycle. The annual cycle began with the appearance of young shoots in late summer. Net productivity was greatest during early autumn and midspring. Little growth occurred during the winter and there was a rapid dieback of shoots in the summer. Tissue concentrations of most chemical constituents declined during spring growth and summer dieback. Uptake rates of mineral nutrients other than nitrogen were large during autumn growth, but slight during spring growth. The same was true of pigment synthesis. Energy accrual was generally proportional to dry-matter increases during both phases of growth. Results of this investigation and previous studies are discussed to show that rates of net nutrient uptake and synthesis of pigments are not merely functions of net dry-matter production, but physiological characteristics of the species. Quantities of chemical substances per unit area of stand did not necessarily follow the same patterns of change as did dry-matter standing crops. Dead Juncus effusus shoots decomposed rapidly, about 50% of the dry matter disappearing within 4 months. Mineral nutrients were lost more quickly than the degradation of dry matter.

SREL Reprint #0269

Boyd, C.E. 1971. The dynamics of dry matter and chemical substances in a Juncas effusus population. The American Midland Naturalist 86:28-45.


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