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Glossary: B is for ... bark, biomass, and boreal
by Ariadne Unst

Glossary of B...

banner (n.)
The upper petal of a pea-like flower.

bark (n.)
The skin or covering of branches and roots of a tree. A relatively waterproof layer that protects the tree from insects, fungus, etc., and stops it from drying out. As the trunk grows, for many trees, the bark cracks as it expanded around the trees.

beak (n.)
A firm and pointed terminal appendage.

bedrock (n.)
Solid, unweathered rock close to the Earth's surface.

A simple, pulpy fruit developed from a single ovary. The fruit may contain few or many seeds, but no stones.

B horizon (n.)
The soil horizon below the A horizon and above the C horizon. In this layer, clay is enriched because of being washed down from the A horizon. Iron and aluminum oxides are similarly enriched. (Sometimes the precipitation of iron can cause the development of a hardpan.) Calcium carbonate, calcium sulfate, and other salts also accumulate.

biennial (n.)
A plant with a two-year life cycle. Usually it grows only stems and leaves in the first year; in the second year it flowers, seeds, and dies.

bifurcation ratio (n.)
Quantitative ratio between parts of systems that display branching. In particular, a tree's trunk bifurcates into smaller branches, which in turn bifurcate or branch. The ratio between the branches that are derived from a larger branch or main stem is the bifurcation ratio.

biodiversity (n.)
Biological diversity. It includes: species diversity (that is, diverse species), genetic diversity (the genetic variability among individuals within each species), and ecosystem diversity (the variety of ecosystems).

biomass (n.)
Total mass of a species or group of organisms in a particular habitat. The commercially sponsored California Forest Products Commission reports (1999) forest biomass as "all the plant material above the ground in a forest". Years of fire suppression leaves forests with increased ground-level tinder and fire hazard. Harvesting some of the trees:

biome (n.)
A geographic region distinguished by temperature and precipitation and the resulting vegetation. It contains a varying number of ecosystems.

biosphere (n.)
The portion of the Earth that supports life.

biotic factor (n.)
A living organism as well as the products of living organism (such as fallen leaves, feces, shells, and skeletons of dead creatures). Contrast with abiotic factor.

biotic potential (n.)
The powers of a population to increase.

bisexual (adj.)
Has stamens and pistils.

blade (n.)
The expanded leaf or petal; the leaf excluding the stalk.

boreal (adj.)
Northern. Opposite of austral.

boreal forest (adj.)
Forest of High to mid latitudes; dominated by coniferous forest. Predominant tree species are spruce, fir, pine, and cedars. Also called taiga.

bract (n.)
A modified leaf or a reduced leaf, which appears over or under or in association with a flower cluster; the scale-like leaves of an inflorescence.

breed (n.)
A race or strain cultivated by humans.

brown earth (also, brown forest earth) (n.)
Below a litter layer and a humus layer, this first layer of true soil is dark and humus-rich. Such earth is usually acidic, never alkaline, and often develops over clays. It grades into slightly lighter colored subsoils.

bryophyte (n.)
A subdivision of nonvascular plants. Includes mosses and liverworts. Contrast with thallophyte.

bud (n.)
An undeveloped stem, branch, or shoot of a plant. It holds undeveloped, preliminary leaves or flowers.

bulb (n.)
An underground food store of a plant; derived from a shoot enclosed in thick, overlapping, leafy scales.

bundle scar (n.)
The scar that is left on a twig after a leaf falls.

burl (n.)
A woody swelling where the stem joins the roots.