NRES 201 Lecture 23 Outline of Last Lecture I. Ecological effects of soil aerationII. Managing soil aerationIII. Wetlands and their soilsOutline of Current Lecture IV. Importance of soil temperature V. Solar radiation and soil heatingVI. Thermal properties of soilsVII. Soil temperature controlCurrent LectureImportance of soil temperature - - Plant processeso Greater effect - of soil than air temperature, on shoot growth than root growtho Plants differ in soil temperature requirementso In the spring, plant growth is often limited by cold soil temperatures. But, soil warming is not cost - effective.o In the summer, high soil temperatures can be a problem Especially for a shallow - rooted turfgrasso Soil temperatures trigger seed germination Species - specific May require - - Temperature fluctuation- Or previous exposure to cold (2-4 degrees C) (Vernalization)o Cool soils slow root uptake of water and nutrients Can cause P deficiency Can also cause winter burn of evergreens if evaporative loss exceeds water uptake- Microbial processeso Microbial activity is temperature - dependent Some activity even below freezing Activity doubles with every 10 degree rise in soil temperature 35 - 40 degree C is optimal- Freezing and ThawingThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Liquid water below the frost line is drawn toward ice lenses that continually expand in frozen soil.o Enormous pressure cause frost heaving that lifts stones, plants, and fence posts And cracks foundations and roads.o Thawing begins at soil surfaceo The melting ice contributes to surface runoff and erosion - Soil heating by fireo Surface soil briefly heated by forest, range, or crop - residue fireso Some mineral breakdown possible above 300 degrees Co Main effect is to destroy organic mattero Water infiltration is reduced And saturated soil above the water - repellant zone can lead to mudslides.Solar radiation and soil heating- The solar radiation balanceo Soils mainly heated by solar radiationo Only 50% of solar energy reaches the Earth Up to 75% in cloud free areaso Of the incident solar energy: 90% evaporates water or is radiated back to the sky Only 10% heats the soil- Albedoo Refers to the fraction of incident radiation that is reflected by the land surfaceo Depends on soil color and roughnesso Dark soils are often cooler than light soils Because of a higher moisture contento Vegetation also affects albedo- Aspecto The direction of slopeo Greatest solar energy absorption when sunlight falls perpendicular to the soil surfaceo North facing slopes are moister and cooler o South facing slopes are drier and warmer- Soil covero Warming and cooling occur more quickly for bare soils than for those covered by: Vegetation Mulch Or snowo The insulating effect of vegetation is due largely to
View Full Document
Unlocking...