Wet deposition Dry deposition Weathering Recycling Parent
material Soil N-fixation Sources of nutrients to terrestrial
systems 1.Inputs 2. Recycling Organic Inorganic 3.Rates influenced
by: Climate Quality of detritus 1 1 1 1 2* Slide 2 Nutrient
regeneration in terrestrial systems Slide 3 Decomposition Physical
Chemical Leaching Fragmentation Mineralization (e.g.,
ammonification) Breakdown of organic material through decomposition
occurs in several different ways Fungi bacteria Slide 4
Decomposition Physical Leaching Fragmentation Slide 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
(NH 4 + on leaf surface becomes NH 4 + dissolved in soil water)
These inorganic nutrients (ammonia, nitrate, phosphate, etc.) are
immediately available for uptake by plant roots. Slide 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 Slide 7 Chemical Decomposition: Mineralization
Conversion of organic matter to inorganic compounds (CO 2, H 2 O,
NH 4 +, NO 3 +, etc.) Fungi break down the woody components of
litter into inorganic molecules (lignin, cellulose) Bacteria &
other microorganisms break down just about anything else Slide 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 Slide 9 Slide 10 Decomposition Mechanisms Leaching
Fragmentation Chemical Alteration Factors influencing decomposition
rate Quality of Detritus Climate (temperate vs. tropical) Soil
Animals Slide 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 Slide 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? Slide 13 Soil Animals Soil animals have effects on
soil structure, litter fragmentation, transformation of organic
compounds, and composition of microbial community Microfauna (2mm;
earthworms & termites, called ecosystem engineers because they
alter resource availability by modifying physical properties of
soils and litter Slide 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 Slide 15 Vegetation as a
compartment Slide 16 Nutrient regeneration in aquatic systems Slide
17 Global distribution of chlorophyll in oceans Productivity in
aquatic ecosystems Where is productivity highest? Shallow seas,
proximity to bottom sediments Strong upwelling zones Slide 18 Slide
19 Slide 20 Carbon cycle units = Gt C = 10 15 g C Slide 21 Carbon
dioxide 1 2 3 Slide 22 3 Slide 23 Nitrogen Cycle Nitrogen Fixing
Low levels of NH 4 +, NO 3 -2 Leaching Denitrification Atmosphere
N=N Oceans Soils, Organisms Denitrification Nitrogen Fixing
Sediments Mineralization Assimilation Nitrification Burial Marine
cycling
