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Glossary: O is for ... old organic order.
by Ariadne Unst

Glossary of O...

O horizon (n.)
The soil horizon above the A horizon.

old growth (n.)
Old-growth or ancient forests are forest lands that have not been harvested or in any other way altered by people.
Of the estimated 2 million acres of coast redwood forest shortly after the arrival of the Europeans, less than 4% are now uncut.
An old-growth stand is usually well past the age of maturity as defined by the culmination of mean annual increment. It often exhibits characteristics of decadence. Example: low growth rates, dead and dying trees, snags, and down woody material. The stands usually contain large-diameter trees relative to species and site potential, multi-layered canopies, a range in tree-diameter sizes, and the presence of understory vegetation.
Some documents specify a lower limit on size; for example Michael Barbour et al. in Coast Redwood: A Natural and Cultural History state that old-growth redwoods exceed 200 feet high and 40 inches in diameter.

open (adj.)
Uncongested and open organization of flowers in an inflorescence.

opposite (adj.)
Leaves that lie in pairs on axis. Uncongested and open organization of flowers in an inflorescence.

order (n.)
A taxonomic category ranking below a class and above a family. Contains related families.

organic soils layers (n.)
L-layer--Freshly fallen or only slightly decomposed leaves, twigs, flowers, fruit, and bark lying on the soil surface.
F-layer--Zone of active organic matter fermentation.
H-layer--Humidified zone. The more or less stable fraction from the decomposed soil organic material. Generally, it is amorphous, colloidal, and dark.

organism (n.)
An individual member of a species. A single biological entity.

ovary (n.)
The basal portion of a pistil where germinated cells develop into seeds. Some plants have a superior ovary and some have an inferior ovary.

ovate (adj.)
Plump like a longitudinal section of a hen's egg; broad end basal.

ovule (n.)
The body (inside the ovary) that develops into the seed.