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Glossary: T is for ... taiga, tap root, and tree ring.
by Ariadne Unst

Glossary of T...

taiga (n.)
Far northern coniferous forest. In Siberia, Eurasia, and America. Extends to the northern limit of trees.
Exists where the growing season is too short for deciduous trees.
Relatively few species, compared to tropical or temperate forests.
main types:
Forest of High to mid latitudes; dominated by coniferous forest. Predominant tree species are spruce, fir, pine, and cedars. Also called boreal forest.
Also see our page on the boreal forest.

tap root (n.)
A single thick vertical root. It is the primary root and follows the downward line of the plant's stem, often deeply into the ground.

taxon (n., pl. taxa)
1. a group of organisms of any taxonomic rank, e.g., family, genus or species.
2. a group of organisms or other taxa sharing a single common ancestor.

taxonomy (n.)
1. the method of classifying things into groups.
2. in biology, the classification of living organisms into taxa.

temperate forest (n.)
Three main types, all profoundly harvested and reduced by humans:
Temperate deciduous forest: originally covered most of Europe, eastern North America, and parts of Asia, Japan, Australia, and South America.
Moist temperate coniferous forest: western North America (Alaska to California); also in the Mississippi delta. Humidity is high, often with considerable fog. Conifers dominate, especially redwoods and spruces.
Broad-leaved evergreen forest. Found in central and southern Japan and in Florida. Moisture is high. Differences between winter and summer temperatures are less than in deciduous forests. Live oaks, magnolias, hollies, bays, and sabal palms are typical.

tepal (n.)
: a collective term for sepals and petals, used when they cannot be easily differentiated.

terminal (adj.)
At the end of the branch or stem.

terrestrial (adj.)
Living on land.

thallophyte (n.)
A subdivision of nonvascular plants. Includes algae and fungi. Contrast with bryophytes.

time, deep (deep time)
The expression deep time was introduced by John McPhee (Basin and Range) to describe geological time scales.

throughfall (n.)
All the precipitation reaching the forest floor minus the stemflow, i.e., canopy drip plus direct precipitation.

toothed (adj.)
Notched or indented with small lobes or points along the edge (as on a leaf).

top soil
The surface layer of soil. It is usually rich in nutrients from decaying plants and bacterial material.

Top-to-root ratio or root-to-shoot ratio
The relative weights or volumes of the epicotyl and the hypocotyl of a tree seedling, expressed as a ratio.

tracheid (n.)
Elongated and tapering woody plant cell, as in conifers. Conducts nutrients and supports the plant.

tree
Using Little's definition quoted in Buy Trees of California Trees and Shrubs of California by John Stuart and John Sawyer, a tree is a woody plant with: By contrast, shrubs are generally smaller with multiple stems.

tree ring
See also tree rings at Forests Of California.
One of the concentric circles of wood laid down by trees as they grow. Temperature, rainfall, forest fires, disease, insect infestation and other environmental conditions alter the amount that a tree grows in a year. For a year of extra growth, the ring is thicker. For a challenging year, growth is slowed and the ring is thinner. Most of the cells generated by the cambium collect on the inside of the cambium as xylem. is lighter-colored part of the ring is called springwood or earlywood. In August and early September, the growth rate slows and eventually stops. As growth slows, the walls of the xylem cells become thicker and appear darker than the earlywood. This area of the annual ring is called summerwood or latewood. Together, the earlywood and latewood form one annual ring. In spring, most trees grow quickly; the xylem cells are large with thin walls; a lighter-colored layer of wood is generated, which is called springwood or earlywood. In late summer, growth slows; the walls of the xylem cells thicken; darker wood is generated, called summerwood or latewood. Together, the earlywood and latewood form one annual ring.

trophic level
Each category of feeding, depending on the organism's mode of nutrition. From trophos (Greek for feeder).

tropical zone
Climate is hot. Depending on the locality, it is moist or dry. Vegetation predominantly evergreen.

tropical rain forest
See rain forest.

trunk (n.)
The main stem of a tree.

tuber (n.)
A short, thickened underground stem with numerous buds.

tuff (n.)
A rock composed of the finer kinds of volcanic detritus, usually fused together by heat.

tundra (n.)
Treeless barrens. For a fascinating description of the life of the tundra, see E.C.Pielou's A Naturalist's Guide to the Arctic
Tundra is usually flat or undulating, covered with lichen, sedges and grasses, mosses, and low shrubs (dwarf willows and birches). Characteristic of (a) the Arctic and (b) high-altitude (alpine) regions outside the Arctic.
Compare with the taiga or boreal forest.