BIOL 4120: Principles of Ecology Lecture 5: Terrestrial Environment

1. BIOL 4120: Principles of Ecology Lecture 5: Terrestrial Environment Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate.edu

2. Topics for this class: 5.1 Soil is the foundation of all life 5.2 Formation of soil 5.3 Physical properties of soil 5.4 Soil horizons 5.5 Soil water holding capacity 5.6 Soil ion exchange capacity 5.7 Soil classification 5.8 Light distribution in plant canopy

3. 5.1 Soil is the foundation upon which all terrestrial life depends • Before life invaded the land from the sea, there was probably little that looked like soil today • Dust like Mars; Little organic matter • A few microorganisms. • Soil is medium for plant growth; the basis of all terrestrial life. Without soil, there would be no plants, no soil microorganism and no land animals • Plants obtain many of their water and nutrients from soil and it provides an place to attach to.

4. Definition of soil • Soil is hard to define because it is so complex • Soil is a natural product formed and synthesized by the weathering of rocks and the action of living organism. • Soil is a collection of natural bodies of earth, composed of mineral and organic matter and capable of supporting plant growth. • The stratum below vegetation and above hard rock

5. Soil is a living system made up of a three dimensional matrix (length, width, and depth) and of minerals and organic matter, and organisms: • plants, both roots and stems • Bacteria • Fungi • Algae • Small animals • Larger animals

6. 5.2 Formation of soil Starting Point: weathering of rocks and their minerals. • Mechanical and Chemical Weathering • Mechanical: interaction of several forces • Water • Wind • Temperature • Creates loose material • Sorted and moved • Chemical • Acids produced by lichens and mosses • Addition of organic matter (dead plants and animal tissues) • Oxidization • etc

7. Five interrelated factors • Five factors are involved in the formation of soil • Parent Material • Igneous rock • Sedimentary rock • Metamorphic rock • Climate • Temperature Rainfall • Wind Elevation • Latitude • Biotic Factors • Living organisms (plants, animals, bacteria, fungi). • Degradation by living organisms • Topography • Water runoff • Draining • Erosion • Time • Weathering, accumulation, decomposition and mineralization take time • Initial differentiation can be within 30 years • Formation of true soil, 2000 to 20000 years

8. 5.3 Soils show a great deal of variation • Color • No direct effect on how soil function • Allows classification • Red • Possibly oxides • Black • Possible high organic content • Texture • Variation in size and shape of soil particles • Gravel • >2mm • Sand • 0.05mm to 2mm • Silt • 0.002mm to 0.05mm • Clay • <0.002mm Soil texture is percentage of sand, silt and clay. (Texture chart)

9. Structure • Space for roots etc • Pore space • Amount of water held • Rate of water movement • Aeration • Compaction • Aggregation • Depth • Depends on • Slope • Weathering • Parent material • Vegetation • Grasslands are deep • Forests are shallow

10. 5.4 Soil has horizontal layers Soil profile Layers or horizons

12. 5.5 Moisture holding capacity is an essential feature of soils • Soil can become saturated if all pores filled • All water is hold by soil particulars, at field capacity (FC) • Capillary water is usually present • Extracted by plants • Wilting point (WP) • Plant no long extract water Available water capacity (AWC) • All affected by soil texture • Sand • Lower capacity • Clays • Higher capacity

13. Water content at different soils

14. 5.6 Ion exchange capacity is important to soil fertility Soil soluble nutrients are charged particles, ions. Cations: positively charged (Ca2+, Mg2+, NH4+) Anions: negatively charged (NO3–, PO34–) Ions are attached to soil particles, so do not leach out of the soil. Ion exchange capacity: total number of charged sites on soil particles in a standard volume of soil.

15. Soils have an excess of negative charged sites • Cationic exchange dominant (colloids) • Cation exchange capacity (CEC): total # of negatively charged sites, located on the leading edges of clay particles and SOM. • Concentration and affinity • Al3+ > H+ > Ca2+ > Mg2+ > K+ = NH4+ > Na+

16. Soils have an excess of negative charged sites Change in pH affects binding capacity for ions • Immovable • Hydrogen (H+) • Aluminum (Al+++) • Removable in order • Calcium (Ca++) • Magnesium (Mg++) • Potassium (K+) • Ammonium (NH4+) • Sodium (Na+)

17. Process of cation exchange in soils In soils with high Mg++ or Ca++, K+ is lacking, why?

18. 5.7 Basic Soil Formation Processes Produce Different Soils • Regional differences in geology, climate, and vegetation give rise to characteristically different soils • The broadest level of soil classification is soil order

19. Entisol Mollisol Alfisol Andisol Aridisol Inceptisol Histosol Oxisol Vertisol Spodosol Ultisol Gelisol • There are twelve orders of soil

21. 5.7 Soils vary with climate and vegetation

23. Ultisols • Ultisol • Warm climate soil • Redish or yellowish • Low nutrient content Laterization: when PPT greatly exceeds ET in warm climates, water rapidly percolated through soil and into groundwater. Soluble soil nutrients are constantly leached out of soils, leaving behind the less soluble ions (Al+++ and Fe++) which give soil color (whitish for Al and red for Fe) and H+ make soil acidic and nutrient poor.

24. Salinization (Aridisol) Salinization: in very dry climates and when loss of soil moisture due to ET exceeds PPT, water leaves the soil through the surface. The minerals (NaCl) dissolved move upward from the groundwater and result in a salt crust on the surface of the soil. Irrigation of dryland can result salinization. This becomes a problem in US southwest, Australia, Northern Africa, China, and major areas of dryland irrigation.

25. 5.8 Light distribution within plant canopy • Influencing factors • Vegetation types • Leaf area index (LAI) • Leaf angles

26. Plant cover dramatically changes the light environment underneath it • types of plants making up the cover can have an effect (small portion reach ground) • Deciduous forest – 1% to 5% • Coniferous forest – 10% to 15% • Tropical rain forest – 0.25% to 2%

27. Total LAI=315/78.5=4

28. Effect of leaf angle on leaf area index and light penetration

29. Season also affects the light penetration • The ground under a deciduous forest will undergo a seasonal cycle affected by leaf loss • The ground under a coniferous forest will undergo a seasonal cycle unaffected by leaf loss • The ground under a tropical rainforest will neither have a seasonal cycle or an effect from leaf drop

31. Quantifying Ecology: Beer’s Law and the Attenuation of Light • The greater the surface area of leaves, the less light will penetrate the canopy and reach the ground • The attenuation (vertical reduction) of light through a stand of plants is estimated using Beer’s law

32. Beer’s Law

35. The End

36. Basic Soil Formation Processes Produce Different Soils • Laterization is a process common to soils found in humid environments in the tropical and subtropical regions  heavy leaching of nutrients • Calcification occurs when evaporation and water uptake by plants exceed precipitation  deposition and buildup of alkaline salts (CaCO3) in the subsoil • Salinization occurs in very dry climates or coastal regions as a result of salt spray  salt deposits near the soil surface

37. Podzolization occurs in cool, moist climates where coniferous vegetation (pine forests) dominates  acidic soil enhances leaching of cations, iron, and aluminum from the topsoil • Gleization occurs in areas with high rainfall or in areas of poor drainage  organic matter is slowly decomposed and accumulates in the upper layers of soil

38. Padilla and Pngnaire (2007, Functional Ecology. Mediterranean Woody seedling)