1. Sources of nutrients to terrestrial systems1
Wet deposition
Inputs
2. Recycling
OrganicInorganic
Rates influenced by:
Climate
Quality of detritus 1
Dry deposition 1
N-fixation 2*
Recycling
Soil 1
Weathering
Parent material

2. Nutrient regeneration in terrestrial systems

3. Leaching Physical Fragmentation Decomposition Mineralization
Breakdown of organic material through decomposition
occurs in several different ways
Leaching
Physical
Fragmentation
Decomposition
Mineralization
(e.g., ammonification)
Chemical
Fungi
bacteria

4. Leaching
Physical
Fragmentation
Decomposition

5. Physical Decomposition: Leaching
Rainwater falling on leaf litter and other detritus dissolves inorganic nutrients from surfaces and washes them into the soil
Compounds are not changed during this process (NH4+ on leaf surface becomes NH4+ dissolved in soil water)
These inorganic nutrients (ammonia, nitrate, phosphate, etc.) are immediately available for uptake by plant roots.

6. Physical Decomposition: Fragmentation
Freeze/thaw cycles and animal activities (munching by insects, slugs, nematodes, etc.) break up detritus into smaller pieces
Resulting smaller pieces of detritus have a high surface area to volume ratio, increasing the rate of decomposition

7. Chemical Decomposition: Mineralization
Conversion of organic matter to inorganic compounds (CO2, H2O, NH4+, NO3+, etc.)
Fungi break down the woody components of litter into inorganic molecules (lignin, cellulose)
Bacteria & other microorganisms break down just about anything else

8. Mycorrhizae Symbiotic association between plant roots and fungi
Endomycorrhizae vs. Ectomycorrhizae
Play a role in decomposition by breaking down proteins into amino acids that are transferred to host plant

10. Decomposition Mechanisms Factors influencing decomposition rate
Leaching
Fragmentation
Chemical Alteration
Factors influencing decomposition rate
Quality of Detritus
Climate (temperate vs. tropical)
Soil Animals

11. Quality of Detritus Animal carcasses decompose faster than plants
Leaves decompose faster than wood
In any given climate, there is a 5 to 10-fold range in decomposition rates that is attributable to detritus composition

12. Climate: Tropical vs. Temperate
What does this tell you
about which abiotic factors
are most important in terms
of controls over rates of
decomposition?

13. Soil Animals
Soil animals have effects on soil structure, litter fragmentation, transformation of organic compounds, and composition of microbial community
Microfauna (<0.1mm; protozoans, nematodes)
Mesofauna (0.1mm – 2mm; taxonomically diverse, have the greatest effect on decomposition)
Macrofauna (>2mm; earthworms & termites, called ecosystem engineers because they alter resource availability by modifying physical properties of soils and litter

14. Soils as a compartment
Low clay content of soils in the tropics results in nutrients washing out of the soil unless there is quick uptake by plants
As a result, most nutrients are found in living biomass rather than soils: important implications of tropical deforestation

15. Vegetation as a compartment

16. Nutrient regeneration in aquatic systems

17. Global distribution of chlorophyll in oceans
Productivity in aquatic ecosystems
Global distribution of chlorophyll in oceans
Where is productivity highest?
Shallow seas, proximity to bottom sediments
Strong upwelling zones

18. Lake structure is similar to that of oceans but on a smaller scale
Littoral zone == shallow zone along lake shore; rooted aquatic plants generally grow here
Limnetic zone == open lake
Lakes divided vertically into 3 main depth zones:
epilimnion = warm surface layer; well-stirred; thickness of heated zone depends on velocity of winds that stir water at the surface
metalimnion= thermocline, zone of rapid temperature decrease
hypolimnion = cold dark waters
During the summer – you see a pretty distinct thermal stratification of these layers in most lakes

20. Carbon cycle – units = Gt C = 10 15 g C

21. Carbon dioxide 1 2 3

22. 3

23. Nitrogen Cycle Atmosphere N=N Soils, Oceans Organisms
Nitrogen Fixing
Denitrification
Denitrification
Nitrogen Fixing
Soils,
Organisms
Oceans
Marine
cycling
Leaching
Burial
Low levels of NH4+, NO3-2
Sediments
Mineralization
Assimilation
Nitrification