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.
I. Terrestrial regeneration of nutrients: recycling of matter
A. Intrasystem cycling: fluxes between pools within an ecosystem 24.2
1 Soil nutrientplant uptake/uselitterfalldecomposition/mineralizationsoil
2. Nutrient regeneration in soil 508-9
Leaf litter regeneration: decomposition/mineralization (organicinorganic)
24.5, 24.6
Effects of leaf quality
Effects of climate 512-13
Follows multiple paths 511-512 24.9
Depolymerization – large organic molecules broken down into subunits;
its rate limits cycle and ultimately ecosystem productivity
immobilization by microbes limits nutrients available to plants
3. Soil nutrient properties 513
Eutrophic vs. oligotrophic soils
Mechanisms to retain nutrients (vs. leaching)
Are nutrients stored in soil or vegetation? 24.11
4. Annual dynamics/budget (balancing the books)
Requirements: leaf production, wood growth, leaching
Uptake: woody increment, returns from leaching litterfall
Reabsorption: uptake from leaves prior to leaf drop
B. Intersystem cycling: fluxes between ecosystems 24.2
1. Input sourcesnutrient gains 507
Lithosphere; weathering: adds new inorganic nutrients
physical/chemical alteration of rocks/minerals
Atmosphere: wetfall (in rain) and dryfall (dust particles)
Hydrosphere: waterflow (e.g. floods)
2. Output sourcesnutrient losses
Atmosphere
Ground water and stream runoff
3. Nutrient budgets
balanced (in equilibrium): if Input = Output
unbalanced (not in equilibrium): if I>Ostorage; if O>Iloss
4. Watershed studies 507-8 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
II. Aquatic regeneration: slow from deep water and sediments
A. Global variation in NPP vs. nutrient availability 24.16
B. Seasonal cycles in lakes 518-19 24.17, 24.18
Stratification effects on nutrients and productivity
C. Nutrient inputs necessary to maintain high NPP 520-2124.20
Natural limitation (often by P in lakes; Fe in oceans) 522-5 24.20; 24.24
Variation among eutrophic vs, oligotrophic lakes in nutrients and productivity 522
Salt marshes (+ estuaries) high productive 521-2 24.21
Export energy to other marine ecosystems 24.22
Summary: 1-5, 7, 10-12, 14-15