LECTURE 27
CH 24 NUTRIENT REGENERATION IN TERRESTRIAL AND
AQUATIC ECOSYSTEMS
MAJOR CONCEPTS
1. Intrasystem cycling involves movement of matter from plant to soil to plant.
2. Nutrient regeneration in terrestrial ecosystems occurs primarily in the soil.
3. Climate and quality of plant detritus influences rates of nutrient regeneration.
4. As soils age, their nutrient availability decreases; mechanisms retain scarce nutrients.
5. Nutrient budgets for an ecosystem account for all nutrients.
6. Intersystem cycling involves flow between ecosystems; input must equal outputs
for an ecosystem to be in equilibrium.
7. Human disturbances impact nutrient availability and increase nutrient loss from
ecosystems.
8. Aquatic productivity varies depending on nutrient availability. Ocean productivity is
often limited by Fe; freshwater systems are limited by P.
9. Nutrients in water are regenerated slowly in deep layers of water and sediments.
10. Thermal stratification hinders vertical mixing in aquatic ecosystems.
11. High external and internal nutrient input makes estuaries and marshes highly
productive.
Terrestrial regeneration of nutrients: recycling of matter
Intrasystem cycling: 24.2
Soil nutrientplant uptake/uselitterfalldecomposition/mineralizationsoil
Nutrient regeneration in soil
Leaf litter regeneration: decomposition/mineralization 24.5, 24.6
Effects of leaf quality
Effects of climate
Follows multiple paths 24.9
Depolymerization – large organic molecules broken down into subunits;
its rate limits cycle and ultimately ecosystem productivity
Soil nutrient properties
Eutrophic vs. oligotrophic soils
Tropical soils: why poor but productive biome?
Mechanisms to retain nutrients
Are nutrients stored in soil or vegetation? 24.11
Annual dynamics/budget (balancing the books)
Requirements
Uptake
Reabsorption
Intersystem cycling 24.2
Input sourcesnutrient gains
Output sourcesnutrient losses
Nutrient budgets
balanced (in equilibrium): if Input = Output
unbalanced (not in equilibrium): if I>Ostorage; if O>Iloss
Watershed studies 24.13
What are sources of nutrient requirements in a forest?
Does intrasystem or intersystem cycling meet most requirements?
Input (in precipitation) vs. output (stream chemistry)
Greater nutrient output with greater stream flow
Greater productivity with greater input
Aquatic regeneration
Global variation in NPP vs. nutrient availability 24.16
Seasonal cycles in lakes 24.17, 24.18
Stratification effects on nutrients and productivity
Factors necessary to maintain high NPP 24.20
Natural limitation (often by P in lakes; Fe in oceans) 24.20; 24.24
Variation among eutrophic and oligotrophic lakes in nutrients and productivity
Salt marshes (+ estuaries) high productive 24.21
Export energy to other marine ecosystems 24.22
Summary: 1-5, 7, 10-12, 14-15