introduction - Pennsylvania Natural Heritage Program

from primary producers (green plants) through a series of organisms that eat and are eaten. Onlysome of the many possible relationships can be shown in such a diagram and it is usual to includeonly one or two carnivores at the highest trophic levels.Geomorphic: pertaining to the form of the earth or of its surface features.Instar: an insect larva that is between one moult (ecdysis) of its exoskeleton and another, or between thefinal ecdysis and its emergence in the adult form. Instars are numbered and there are usually severalduring larval development.Landscape Conservation Area (LCA): A large contiguous area; important because of its size,contiguous forest, open space, habitats, and/or inclusion of one or more Biological Diversity Areas,and although including a variety of land uses, has not been heavily disturbed and thus retains much ofits natural character.Mast: a fruit, especially of beech, but also of oak, elm, and other forest trees.Mesic: refers to an environment that is neither extremely wet (hydric) nor extremely dry (xeric).Mineral soil: a soil composed predominantly of, and having its properties determined Predominantly by,mineral matter. Usually contains < 20 percent organic matter, but may contain an organic surfacelayer up to 30 centimeters thick.Mycorrhiza: a close physical association between a fungus and the roots of a plant, from which bothfungus and plant appear to benefit; a mycorrhizal root takes up nutrients more efficiently than does anuninfected root. A very wide range of plants can form mycorrhizas of one form or another and someplants appear incapable of normal development in the absence of their mycorrhizal fungi.Old-field ecosystem: develops on abandoned farmland as the land gradually reverts to forest.Physiographic Province: A region of which all parts are similar in geologic structure and Climate andwhich has consequently had a unified geomorphic history; a region whose relief features andlandforms differ significantly from that of adjacent regions.Riparian: pertaining to or situated on the bank of a body of water, especially of a river.Toe slope: The lowest part of a slope or cliff; the downslope end of an alluvial fan.Trophic level: A step in the transfer of energy within a food-web. There may be several trophic levelswithin a system, for example: producers (autotrophs), primary consumers (herbivores), and secondaryconsumers (carnivores); further carnivores may form fourth and fifth levels.Vernal: occurring in the spring.Xeric: a dry, as opposed to a wet (hydric) or intermediate (mesic) environment.Xerophyte: a plant that can grow in very dry conditions and is able to withstand periods of drought.146