D

deadfall— A trap in which the prey (usually small) is killed by a falling stone or log.

debris flow— A moving mass of rock fragments, soil, and water, more than half of the particles larger than sand size, often the result of an intense thunderstorm and accompanying flash-flooding.

deciduous— Falling off at a certain season or stage of growth (e.g., plants with deciduous leaves as opposed to evergreens).

decoy— To attract by means of imitated sounds or models.

decurved— Curved downward or bent down.

defile— Narrow natural passages often favored as hunting locations.

deflexed— Turned abruptly downward (same as reflexed). (See Fig. 6.1.)

deltoid— Triangular leaf, attached at the center of one side.

demographics— Phenomena related to populations.

dendrochronologists— Scientists who study the record of information provided by trees and other woody plants in their ring structure or series.

dendrochronology— A dating method in which distinctive sequences of tree-ring widths are used to establish age.

dentate— Toothed, with the teeth directed outward; loosely used for any large teeth.

diapause— A period, usually longer than one month, in the life cycle of an organism during which the organism is quiescent.

dihedral— Having wings set off from the body at a distinct angle from the horizontal.

dimorphism— The existence of two size or color categories within a species, especially as occurs between the sexes.

dioecious— Flowers unisexual, having the male and female (or staminate and ovulate) elements on different individuals.

diopside— A mineral of the clinopyroxene group, CaMg(SiO₃ )₂ . Occurs as a mineral in contact metamorphism.

dipteran— A member of the Order Diptera, a two-winged fly.

discordant— Lack of parallelism between adjacent strata.

disjunct— Discontinuous, widely separated.

diurnal— Active during the day.

dolomite— 1. A common rock-forming mineral, CaMg(CO₃ )₂ . Part of the magnesium may be replaced by ferrous iron. Dolomite is white to light-colored and has perfect rhombohedral cleavage. 2. A sedimentary rock commonly interbedded with limestone.

dolomite barrens— Areas of dolomite that from a distance appear devoid of vegetation.

dorsal— Refers to the "back" or upper side of an organism.

duff— Organic material (predominantly needles and leaves) that accumulates beneath trees.