SOILS

	IMPORTANCE OF SOIL

		VITAL TO THE FUNCTIONING OF 
		TERRESTRIAL COMMUNITIES

			SITE OF MOST DECOMPOSITION

				NUTRIENT RELEASE

			SITE OF WATER UPTAKE BY PLANTS

	SOIL PROFILE

		VERTICALLY STRATIFIED INTO HORIZONS

			GENERAL PATTERN

				FIVE MAJOR HORIZONS

					O HORIZON - FRESH OR PARTLY 
					DECOMPOSED ORGANIC MATTER

					A HORIZON - UPPER LAYER OF 
					MINERAL SOIL (RICH IN ORGANIC 
					MATERIAL)

						TOGETHER WITH THE O 
						HORIZON WHERE MOST 
						BIOLOGICAL ACTIVITY 
						OCCURS

					E HORIZON - ZONE OF MAXIMUM 
					ELUVIATION (LEACHING) OF 
					DISSOLVED MATERIAL

					B HORIZON - ZONE OF MAXIMUM 
					ILLUVIATION (ACCUMULATION 
					OF ELUVIATES)

					

					C HORIZON - WEATHERED 
					UNDERLYING GEOLOGICAL 
					MATERIAL

	SOIL PROPERTIES

		PHYSICAL 

			COLOR - HORIZONS MAY DIFFER

				COLOR VARIES WITH ORGANIC 
				CONTENT, CHEMISTRY OF PARENT 
				MATERIAL AND DRAINAGE
			TEXTURE AND STRUCTURE

				TEXTURE - DETERMINED BY THE 
				PROPORTIONS OF SAND, SILT AND 
				CLAY

					TEXTURE PLAYS A ROLE IN 
					DETERMINING THE PORE SPACE 
					OF A SOIL

						PORE SPACE - AFFECTS 
						WATER INFILTRATION AND 
						DRAINAGE AND THE TOTAL 
						SURFACE AREA FOR WATER 
						ADHERENCE AND CHEMICAL 
						ACTIVITY

				STRUCTURE - THE RESULT OF THE 
				WAY SOIL PARTICLES ARE 
				AGGREGATED

					DETERMINED IN PART BY 
					TEXTURE

				DEPTH - VARIES AS THE RESULT OF 
				DIFFERENCES IN SLOPE, RATE OF 
				WEATHERING, NATURE OF THE 
				PARENT MATERIAL AND 
				VEGETATION

				MOISTURE - MUCH AFFECTED BY 
				TEXTURE

					DIFFERENT MEASURES OF 
					MOISTURE

						FIELD CAPACITY - THE 
						AMOUNT OF WATER AFTER 
						THE LARGE PORE SPACES 
						HAVE DRAINED

						AVAILABLE WATER 
						CAPACITY - THE 
						RENEWABLE WATER VOLUME 
						OF THE SOIL

						ITS LOWER LIMIT SET BY THE 
						PERMANENT WILTING 
						POINT

							WHEN SOIL WATER FALLS 
							TO A LEVEL THAT 
							RESULTS IN GREATER 
							TRANSPIRATION THAN 
							ABSORPTION 

		CHEMICAL

			INFLUENCED BY THE PARENT 
			MATERIAL, VEGETATION, MOISTURE, 
			CLAY AND ORGANIC MATTER CONTENT 
			ETC.

				CLAY PLAYS A MAJOR ROLE

					IT CAN TAKE MANY FORMS 
					PRODUCING DIFFERENT 
					COMPLEXES OF SILICON AND 
					ALUMINUM OXIDES 

						FORMING COLLOIDAL 
						PARTICLES CALLED 
						MICELLES

							THE 2:1 (Si/Al) CLAYS 
							(SUCH AS
							MONTMORILLONITE) 
							OFTEN ACQUIRE A NET 
							NEGATIVE CHARGE AS 
							THE RESULT OF 
							SUBSTITUTIONS OF IONS 
							WITH LESS POSITIVE 
							CHARGE

								THIS AFFECTS THE 
								CATION EXCHANGE 
								CAPACITY

									THE GREATER THE 
									CAPACITY THE 
									MORE NUTRIENT 
									CATIONS THAT 
									CAN BE STORED IN 
									THE SOIL

	LIFE IN THE SOIL

		MOST ACTIVITY IS IN THE UPPER HORIZONS

		IMPORTANT ORGANISMS INCLUDE: 

			BACTERIA, FUNGI, PROTOZOANS, 
			NEMATODES, SPRINGTAILS, 
			EARTHWORMS ETC.

			THESE LIVE IN PORES OF VARIOUS SIZES

			THE SMALLEST IN WATER FILMS ON SOIL 
			PARTICLES

			MANY POSSESS ENZYME SYSTEMS THAT 
			CAN BREAKDOWN CELLULOSE (OR 
			SYMBIONTS IN THE GUT WITH SUCH 
			ENZYMES)
			MANY PREDATORS

	SOIL GENESIS

		SOIL-FORMING FACTORS INCLUDE:

			PARENT MATERIAL - RESIDUAL OR 
			TRANSPORTED

			CLIMATE - TEMP. AND PRECIPITATION 
			AFFECT WEATHERING, DECOMPOSITION, 
			LEACHING, PLANTS ETC.

			BIOTIC FACTORS - VEGETATION AND 
			SOIL ORGANISMS

				NUTRIENT UPTAKE AND RELEASE, 
				AERATION (ROOT CHANNELS, 
				ANIMAL TUNNELS), BREAKDOWN OF 
				LARGE ORGANIC PARTICLES ETC.

			TOPOGRAPHY - STEEP SLOPES HAVE 
			MORE RUN OFF, GREATER EROSION AND 
			LESS DEVELOPMENT OF SOIL THAN 
			FLATTER TERRAIN

			TIME 

				SOIL FORMING PROCESSES MAY TAKE 
				A LONG TIME
					YOUNG SOILS ARE OFTEN MORE 
					FERTILE THAN OLD SOILS

						LESS TIME FOR LEACHING

	SOIL DEVELOPMENT (FORMATION)

		MAJOR PROCESSES

			PODZOLIZATION - ASSOCIATED WITH 
			COOL WET CLIMATES AT MID TO HIGH 
			LATITUDES AND AT HIGH ELEVATIONS

				

				SLOW DECOMPOSITION OF ORGANIC 
				MATTER, FORMATION OF ORGANIC 
				ACIDS AND LEACHING OF CATIONS

					CONIFERS DO WELL IN THIS TYPE 
					OF SOIL BECAUSE THEY CAN 
					TOLERATE LOW pH AND A 
					DEFICIENCY OF CATIONS

			LATERIZATION - ASSOCIATED WITH 
			WARM WET CLIMATES

				RAPID DECOMPOSITION OF ORGANIC
				MATTER, LEACHING OF SILICA AND 
				CATIONS, PRECIPITATES OF IRON 
				AND ALUMINUM OXIDES, 
				FORMATION (SOMETIMES) OF 
				LATERITE (HARD IMPERMEABLE 
				LAYER)

			CALCIFICATION - ASSOCIATED WITH 
			COOL TO HOT CLIMATES WHERE 
			PRECIPITATION IS OFTEN LESS THAN 
			EVAPOTRANSPIRATION AND THE
			PARENT MATERIAL IS RICH IN CALCIUM 
			CARBONATE 

				LITTLE LEACHING OF CATIONS, 
				ACCUMULATION OF ORGANIC 
				MATTER, OFTEN WITH THE 
				PRECIPITATION OF CALCIUM 
				CARBONATE IN DEEPER LAYERS

				TYPICAL OF GRASSLANDS

		SALINIZATION - ASSOCIATED WITH ARID 
		REGIONS WITH LITTLE VEGETATION

			SOILS CHARACTERIZED BY LITTLE 
			ORGANIC MATTER, ACCUMULATION OF 
			PRECIPITATED SOLUBLE SALTS (Na, K, 
			Mg, Ca)

				SALTS FROM PARENT MATERIAL OR 
				CONCENTRATED BY EVAPORATION 
				OF RUN OFF WATER

		GLEIZATION - ASSOCIATED WITH COLD 
		WET CLIMATES (E.G., TUNDRA) WHERE THE 
		WATER TABLE REMAINS ABOVE THE B AND 
		C HORIZONS

			HIGH IN ORGANIC CONTENT BECAUSE OF 
			LOW RATE OF DECOMPOSITION BY 
			MICROORGANISMS

				pH IS OFTEN LOW (BUILD UP OF 
				ORGANIC ACIDS)

	CLASSIFICATION OF SOILS

		11 MAJOR SOIL ORDERS (US SYSTEM)

	GROUPING SOILS

		CATENA - A PATTERN OF RELATED SOILS 
		FOUND SIDE BY SIDE IN AREAS WITH 
		DIFFERENT DRAINAGE AND SLOPE

			BUT, DEVELOPED FROM THE SAME 
			PARENT MATERIAL

		TOPOSEQUENCE - A PATTERN OF SOILS 
		ALONG TOPOGRAPHICAL CONTINUUM

			MAY NOT BE DEVELOPED FROM THE 
			SAME PARENT MATERIAL

		CHRONOSEQUENCE - A PATTERN OF SOILS 
		DEVELOPING IN THE SAME MANNER BUT AT 
		DIFFERENT STAGES OF THAT DEVELOPMENT

			E.G., AT DIFFERENT DISTANCES FROM A 
			RETREATING GLACIER