dynamics of dry matter and chemical substances
in a Juncas effusus population
Savannah River Ecology Laboratory, P O Drawer E, Aiken, SC 29802
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
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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