Ridge and Valley

Weathering

The physical and chemical breakdown of particles.

Characteristics of Rocks

Earth's Rocks: Igneous, Metamorphic, sedimentary.

Igneous Rocks

Primary minerals such as quartz, muscovite, feldspars, biotite, augite, hornblende.

Sedimentary Rocks

Forms when weathering products released from older rocks collect under water as sediment and reconsolidate.

Metamorphic Rocks

Formed from other rocks by a process of change termed 'metamorphism'.

Exfoliation

The peeling away of outer layers of rock.

Chemical Weathering

Enhanced by water and oxygen.

Hydration

Water molecules binding to a mineral.

Hydrolysis

Water molecules split into hydrogen and hydroxyl components, replacing a cation from the mineral structure.

Well-weathered soils

Silicate clays and very resistant end products.

Residual Parent-Material

Develops in place from weathering of the underlying rock.

Colluvium

Made up of poorly sorted rock fragments detached from heights and carried downslope.

Alluvial Stream Deposits

Floodplains, alluvial fans, deltas.

Floodplain

Part of a river valley.

Delta

Continuation of a floodplain, clayey, poorly drained.

Glacial Till

Heterogeneous mixtures of debris deposited directly by ice.

Moraines

Irregular ridges where glacial tills are deposited.

Aerosolic dust

Fine particles carried high in the air, deposited by rainfall.

Eolian

Wind-transported particles.

Peat

Organic deposits including moss peat, herbaceous peat, woody peat, sedimentary peat.

Pedoturbation

The mixing activities of animals in soil.

Catena

Soils together in the landscape, sequence of distinct but related soil types arranged down a slope.

Topo sequence

Differences among soils resulting from the influence of topography.

Chrono sequence

Set of soils that share a common community of organisms, climate, parent material, and slope, differing in weathering time.

Transformations

Occur when soil constituents are chemically or physically modified or destroyed.

Translocations

Movement of inorganic and organic materials laterally or vertically within soil horizons.

Additions

Inputs of materials to the developing soil profile from outside sources.

Master Soil Horizons

O - organic, A - mineral mixed with humus, E - eluviation, B - illuviation, C - zone of least weathering, R - bedrock.

Barrens

Woodland or shrubland communities where tree establishment or growth is suppressed by environmental conditions and/or disturbance regime; often found on thin or excessively drained soils.

Bog

A nutrient-poor, acidic peatland that receives water primarily from direct rainfall, with little or no input from groundwater or runoff; vegetation consists primarily of peat mosses (Sphagnum spp.) and ericaceous shrubs.

Canopy

Branches and leaves of plants that form the uppermost layers of vegetation in a community; a canopy is said to be closed (or have 100% cover) when the lower strata are fully shaded during the growing season.

Characteristic species

A species strongly associated with a particular community type, either as a dominant or very common component.

Co-dominant

A species with relatively high abundance or percent cover; two or more species providing roughly equal cover, abundance, or influence in a community or stratum.

Community

An assemblage of plants and/or animal populations sharing a common environment and interacting with each other.

Conifer

Any of a large group of cone-bearing trees and shrubs, mostly evergreens such as the pine, spruce, fir, cedar, etc.; some conifers drop their leaves yearly and thus are not 'evergreen' (e.g. tamarack, bald cypress).

Disturbance

A temporary change in average environmental conditions that causes a pronounced change in ecosystem; may be natural (e.g. blow-down) or human-induced (e.g. logging, introduction of invasive species, etc.).

Dominant

A species with the greatest abundance, percent cover, or influence in a community or stratum.

Edaphic

Relating to soil, especially as it affects living organisms. Edaphic characteristics include such factors as water content, acidity, aeration, and the availability of nutrients.

Ericaceous

Members of the heath family (Ericaceae).

Exotic

Species not native to Pennsylvania, or to the area in which they occur.

Forb

A broad-leaved (not grass-like) herbaceous plant; may include ferns and fern-allies.

Forest

A type of community dominated by trees greater than five meters in height, and having at least 60% canopy closure, crowns usually interlocking; may be terrestrial or palustrine.

Graminoid

Grass-like, narrow leaved herbaceous plants; includes grasses (Poaceae), sedges (Cyperaceae), rushes (Juncaceae), and a few others.

Grass

A member of the grass (Poaceae) family.

Ground layer / Ground flora

The herbs, shrubs, and woody vines beneath the trees in a forest; or the lowest layer of vegetation in an open-canopy community.

Hardwood

In our region, broad-leafed deciduous trees.

Heath

A member of the family Ericaceae; ericaceous plants thrive in acidic soils.

Herb, Herbaceous

Plants with no persistent woody stem above the ground, as distinct from trees and shrubs.

Herbaceous layer

The layer of vegetation in which herbs are common, usually the ground flora.

Herbaceous perennial

A perennial plant that dies back to their rootstock each Fall and regenerates each Spring.

Hydrophyte, Hydrophytic

Plants adapted to growing in water or on a substrate (soil) that is at least periodically deficient in oxygen as a result of excessive water content. Plants that grow in hydric soils.

Invasive species

A species that does not naturally occur in a specific area and whose introduction likely causes economic or environmental harm or harm to human health.

Native

Species that occurred in Pennsylvania or in the area in which they are found prior to European settlement; not introduced by human activities; indigenous.

Old Growth

Near climax forest stands that have suffered few, if any, intrusions by humans.

Palustrine

Pertaining to freshwater wetlands.

Perennial

A plant that lives for more than two years.

Shrub

A perennial, woody plant less than five meters in height with multi-stem growth form.

Spring ephemeral

Usually refers to a forest wildflower that blooms briefly in the Spring prior to leaf-out of the canopy.

Structure

The spatial arrangement of vegetation layers within a community.

Successional

Communities that are changing in composition.

Swamp

A wooded wetland, intermittently or permanently flooded.

Terrestrial

Uplands; where vegetated, supporting vegetation that is not predominantly hydrophytic.

Tree

A woody perennial plant, usually having one principle stem, that has a definite crown and characteristically reaches a mature height of at least five meters.

Understory

The lower layers of vegetation in a community; in a forest, all the vegetation layers beneath the canopy and sub-canopy.

Vernal

Occurring in the Spring; vernal pools are temporary shallow woodland ponds that harbor herptiles (e.g. salamanders, frogs) during their aquatic stage of life.

Wetlands

Areas intermediate between aquatic and terrestrial habitats; characterized by a predominance of hydrophytes, where conditions are at least periodically wet enough, during the growing season, to produce anaerobic soil conditions and thereby influence plant growth.

Woodland

A community with a sparse tree canopy (10%-60% cover), usually with an herbaceous and/or shrub layer. Characteristic of environments where tree establishment or growth is suppressed by edaphic conditions or disturbance regime.

Woody

Plants having lignified stem tissue (trees, shrubs, and woody vines).

Acidic

Soil or water with a pH lower than 7; soils lower than 5.5 pH are strongly acidic.

A-horizon

The top layer of soil horizons, or 'topsoil'; includes decomposed organic materials called humus.

Alluvium

Unconsolidated material deposited by running water, including gravel, sand, silt, clay, and various mixtures of these.

Anticline

A fold in rock strata raised up into an arch through folding.

Basic

Soil or water with a pH higher than 7.

Bedrock

The solid rock that is exposed at the surface or underlies the soil or other unconsolidated material at the surface.

B-horizon

The subsoil layer below the A-horizon.

Calcareous

Describes soil, groundwater, or surface water with high calcium concentrations, often derived from limestone or calcium-rich glacial deposits. These soils show a higher pH (more basic) than acidic soils.

Carbonate rock

Sedimentary rock composed primarily of carbonate minerals (limestone or dolomite).

Dolostone / Dolomite

A sedimentary carbonate rock composed of calcium magnesium carbonate.

Duff / Ground litter

Fresh or partly decomposed organic debris (leaves, twigs); the O-horizon of a soil profile.

Chroma

Colorfulness; the perceived intensity of a color; a chroma of 2 or less on the Munsell scale (dull colored, usually grayish) often indicates hydric (wetland) soils where anaerobic processes occur.

Colluvium

Soil and rock fragments on the base of slopes that have moved predominantly by gravity.

Floodplain / Lowland

Flat to nearly-flat areas along water bodies that are subject to flooding.

Gleyed soil

A characteristic grey mottling of hydric soil formed under anaerobic conditions.

Homocline ridge

A ridge formed by underlying strata tilted in the same direction.

Hydric

Wet; soils that are sufficiently wet to produce anaerobic conditions in the root zone.

Interbedded

Alternating layers of different rock types (shale and sandstone for example).

Limestone

A sedimentary rock composed of calcium carbonate.

Mesic

Areas of intermediate soil moisture content; moist but well drained.

Mineral soil

Soil composed of primarily mineral rather than organic materials.

Muck

Highly decomposed organic material in which the plant parts are no longer distinguishable.

Neutral pH soil

Soil with a pH of 7.0; neither acidic nor basic.

Organic matter (SOM)

Material derived from the decayed organisms; SOM = 'soil organic matter'.

Parent material

The underlying geologic material from which soils form.

pH

'Potential Hydrogen' - a measure of acidity or alkalinity; pure water is neutral (pH of 7). Solutions with pH less than 7 are said to be acidic (pH 0 to

Physiography

Study of the Earth's physical patterns and processes.

Residuum

Soils weathered in place from bedrock; not transported.

Resistant layer

Sedimentary rock layers that are more resistant to erosion.

Sandstone

Sedimentary rock composed primarily of sand-sized minerals or rock grains.

Shale

A fine-grained sedimentary rock composed of "mud" (a mix of clay and silt-size mineral particles) that is laminated and readily breaks into thin pieces.

Silt

Soil composed of fine-grained mineral sediments of intermediate size between sand and clay (0.074 - 0.002 mm) and carried in or deposited by moving water.