The Terrestrial Environment
Chapter 5
Life on land
• Ecosystems defined by plant life (biomes)
• Drying out is biggest challenge on land
– Cells are 75-95% water
• Plants have cuticles with stomata
• Animals have efficient kidneys
Gravity and support
• 80% of mass allocated to support structures in redwoods
Environmental variability
• Terrestrial environments are more variable than aquatic environments
Light availability determined by vegetation characteristics
Leaf area index (LAI)
• Measures the cumulative area of leaves per unit area of ground
– (m2 leaf area/m2 ground area)
Leaf orientation affects light availability
Beer’s Law and Light Attenuation
Sunflecks can account for 70-80% of solar energy
Seasonal changes in light availability
Soil
• Soil is the medium for plant growth, including living organisms large and small
• Soil formed through process of weathering rocks
– Mechanical weathering
– Chemical weathering
Five factors involved in soil formation
Soil color
• Munsell color chart
Soil texture
Soil horizons
Soil moisture
• Water infiltrates the soil to fill soil pore space with water
• Saturated soil has all pores filled with water
• Field capacity is when large pores drain water, yet small pores hold water by
capillary action
• Wilting point is point at which plants can no longer extract water
• Available water capacity (AWC) is field capacity – wilting point
Ion (cation) exchange capacity
Affinity and concentration affect CEC
• Lyotropic series
–
Al3+ > H+ > Ca2+ > Mg2+ > K+ = NH4+ > Na+
Soil classification orders
Soil classification - orders
Soil processes
• Laterization
– Rapid weathering and heavy leaching leads to acidic, iron oxide rich soils
• Calcification
– Movement of dissolved alkaline salts up from groundwater and then build
up in B horizon
• Salinization
– Salts build up on soil surface
• Podzolization
– Organic matter causes acid condition, leading to leaching of Fe and Al from
A horizon
• Gleization
– Poor drainage leads to accumulation of organic matter, which reacts with
iron in soil