《农业生态学agroecology-s2u3.1-soil_around_us》由会员分享，可在线阅读，更多相关《农业生态学agroecology-s2u3.1-soil_around_us（60页珍藏版）》请在金锄头文库上搜索。
1、Agricultural EcosystemsThe Soils Around Us Natural and Managed SoilsDr. G.R. Brewster Department of Environmental SciencesOutline1.Introduction2.What is soil?3.Soil as an environmental interface4.Soil as a resource5.Natural and managed soils6.Soil degradation concerns7.SummaryReadings?AGRI1000 Cours
2、e Resource Manual (pp 41-60) Brady and Weil (2004) 2ndEdition ?Functions of Soils in Our Ecosystems ?Medium for Plant Growth ?Recycler of Raw Materials ?Habitat for Soil Organisms ?Engineering Medium ?Soil as an Environmental Interface ?Soil as a Natural Body ?The Soil Profile and Its Layers (Horizo
3、ns) ?Soil: The Interface of Air, Minerals, Water and Life?Lecture / Class notesIntroduction?Agriculture is a managed ecosystem, and as such, it is considerably different from natural ecosystems.?Question? Is agriculture (animal and/or plant production systems) any different from other factory-based
4、industrial activities?Resources?Inputs?Outputs?$Lets look at agriculture in another another way (with a little bias towards soils).SOIL PlantsAnimalsEquipmentStructures$What is soil?Brewster, 1991Brewster, 1991Soil ?SOIL -The unconsolidated mineral or organic material on the immediate surface of the
5、 earth that serves as a natural medium for the growth of land plants. ?Sense the Soil feel, smell, see, Soil ?The unconsolidated mineral or organic matter on the surface of the earth that has been subjected to and shows effects of genetic and environmental factors of: Factors?1) climate (including w
6、ater and temperature effect)?2) macro- and microorganisms, conditioned by ?3) relief, acting on ?4) parent material over a period of ?5) time.Soil A Product?Soil differs from the material from which it is derived (Parent Material) in many : ?a) physical, ?b) chemical, ?c) biological, and ?d) morphol
7、ogical properties and characteristics. Parent MaterialSoil does not equal DIRT !Soils are Dynamic?the % air, % water, % organic matter will change with time and space. ?The Soil Ecosystem = all parts of the soil, including biotic and abiotic.?Soils are essential to life as we know it on this planet!
8、wind erosion in SaskatchewanBrady and Weil, 2002 Figure 2.32Soil as OPEN and DYNAMIC systemsOpen System: free movement of mass and energyDynamic System: constant change Additions Losses Translocations Transformations Organic horizons Mineral horizonshumidaridWhat would happen if there was no soil?Lo
9、ok-Off, North Mountain, Annapolis Valley, Nova Scotia(Brewster, 1994)What about food security issues? A case can be made that the rise and fall of past civilizations was partially due to soil degradation soil erosion processes.http:/www.culture.grUnlike our ancestors, we cannot move west (go west yo
10、ung man!), there are no, or at least very, very few new frontiers.Soils form a critical interfaceThe pedosphereVolume composition of soilsSoil gases Soil solutions Soil organics Soil minerals20%30%45%5%solidsporesSoil as a Resource?WHAT DOES SOIL DO? ?Healthy soil gives us clean air and water, bount
11、iful crops and forests, diverse wildlife, and beautiful landscapes. ?Soil does all this by performing five essential functions:1) Regulating water.?Soil helps control where rain, snowmelt, and irrigation water goes. ?Water and dissolved solutes flow over the land or into and through the soil. Spring
12、 Flooding Bible Hill2) Sustaining plant and animal life.?The diversity and productivity of living things depends on soil.?The more productive the soil, the more diversity in both the plant and animal community.Soils and Plant Growth?Physical support of plants?Provides water and air?C, H, O?Provides
13、essential elements?Macro-nutrients = N,P,K,Ca,Mg,S?Micro-nutrients = B,Fe,Mn,Cu,Zn,Mo,Co,Cl,Ni3) Filtering potential pollutants.?The minerals and microbes in soil are responsible for :?filtering, buffering, degrading, immobilizing, and detoxifying organic and inorganic materials, including industria
14、l and municipal by-products and atmospheric deposits.4) Cycling Nutrients.?Carbon, nitrogen, phosphorus, and many other nutrients are stored, transformed, and cycled through soil.5) Supporting Structures.?Buildings need stable soil for support, the bearing capacity determines the ease of stable cons
15、truction.http:/rsd.gsfc.nasa.gov/rsd/bluemarble/Natural soils and managed soilsC horizonOrganic horizonA horizonB horizonTypical soil form found in Nova Scotia and Atlantic Canada. (Podzol (Canada); Spodosol (USA)Typical natural soil form of coniferous forests world- wide.BmCBfAeOExploded soil horizons, the variable thickness and composition of soil horizons combine to give a soil its unique flavor or character.Soils are different in different placesSoils are classified, mapped, and their suitabilities a
