Lecture 20: Nutrient Supply and Cycling Flashcards
1
Q
Biogeochemistry
A
the study of the physical, chemical, and biological factors that influence the movement and transformation of elements
2
Q
Nutrient Requirements
A
all organisms have similar nutrient requirements, but amounts and specific nutrients needed vary
3
Q
Structural Compounds of Plants
A
- Carbon (C) is the main component
- Nitrogen (N) is largely in enzymes
4
Q
C:N Ratios
A
- Reflect biochemistry
- Animals have lower C:N ratios
- Humans have a ratio of 6
- Plants have a ratio of 10-40
- Organic matter with a high ratio will have a low net release of nutrients
5
Q
plants
A
- Require a set of essential nutrients
- Some species have specific requirements
- plants that host N-fixing bacteria require cobalt
- plants in selenium-rich soil require colbalt, but it is toxic to most plants
- may resorb as much as 60–70% of the nitrogen and 40–50% of the phosphorus in their leaves before they fall
6
Q
C4 and CAM Plants
A
require sodium
7
Q
Animals
A
- All require sodium
- mostly get nutrients in food as large, complex molecules
- Some are broken down; others are absorbed intact
8
Q
Nutrients
A
- derived from abiotic sources such as minerals in rocks and gases in the atmosphere
- may be cycled within an ecosystem, repeatedly passing through organisms and the soil or water
9
Q
Minerals
A
solid substances with characteristic chemical properties
10
Q
Rocks
A
collections of different minerals
11
Q
Weathering
A
- the process of elements being released from rock minerals
- one of the processes that result in soil formation
12
Q
Mechanical Weathering
A
- The physical breakdown of rocks
- Exposes minerals to the processes chemical weathering
13
Q
Chemical Weathering
A
- chemical reactions release soluble forms of the mineral elements
14
Q
Soil
A
a mix of mineral particles, organic matter, water, and organisms
15
Q
The Water
A
contains dissolved organic matter, minerals, and gases
16
Q
Soil Properties Influence Availibility of Nutrients to Plants
A
- Texture: determined by particle size
Influences soil water- holding capacity - The Coarest particles: sand
- Clays: the smallest particles
17
Q
Cation Exchange Capacity
A
the ability of a soil to hold and exchange cations; it is related to the amount and types of clay particles present
18
Q
Parent Material
A
- The rock or mineral material that was broken down by weathering to form a soil
- May be bedrock, or sediment deposited by glaciers, by wind, or by water
- Chemistry and structure determines rate of weathering, amount and type of minerals released, and it influences soil characteristics such as fertility
- exerts an influence on abundance, growth, and diversity of plants in an ecosystem
19
Q
Climate
A
influences rate of soil development
20
Q
Soil Development
A
- fastest in warm, wet conditions
- In terrestrial ecosystems, the proportion of nutrients in the soil is greater
21
Q
Most of the Nutrients in these Ecosystems
A
are in the living tree biomass
22
Q
What Contributes to Organic Matter in Soils?
A
- organisms such as plants, bacteria, and fungi
23
Q
Organic Matter is a Reservoir of Nutrients
A
- Such as nitrogen and phosphorus
- Organisms also affect weathering
24
Q
Atmospheric Sources of Nutrients
A
- Nitrogen Fixation
- Aerosols/Atmospheric Deposition
25
Nutrient Transformation
- Chemical and biological transformations in ecosystems alter the chemical form and supply of nutrients
26
Decomposition of Organic Matter
- Releases nutrients back into the ecosystem
27
Detritus
includes dead plants, animals and microorganisms, and egested waste products
28
Decomposition
- the breakdown of dead organic molecules, that are released as soluble organic or inorganic compounds for other organisms to take up
29
Litter
Fresh, undecomposed organic matter on the soil surface
30
Fragmentation
increases surface area, which facilitates chemical breakdown
31
Mineralization
Chemical conversion of organic matter into inorganic nutrients
32
Heterotrophic Microorganisms
release enzymes into the soil that break down organic macromolecules
33
What Determines Nutrient Availibility to Autotrophs
- Abiotic and biotic controls on decomposition and mineralization
- Decomposition and mineralization rates are faster in warm, moist conditions
34
Soil Moisture
- influences the availability of water and oxygen to microorganisms
- Wet soils: low oxygen concentrations- which inhibit detritivores
35
Lignin
- strengthens plant cell walls, and is difficult for soil microbes to degrade
- It decomposes very slowly
- amount of lignin in cell walls varies with plant species
36
Nitrification
NH3 and NH4 + are converted to NO3 – by chemoautotrophic bacteria, in aerobic conditions
37
Denitrification
some bacteria use NO3 – as an electron acceptor, converting it into N2 and N2O, in anoxic conditions
38
Soil Fertility
estimated from the concentration of inorganic forms of nitrogen
39
Nutrient Cycling
influenced by climate, as temperature and moisture affect metabolic rates of the organisms involved in nutrient transformations
40
Mean Residence Time (Turnover Rate)
- amount of time on average that a molecule spends in the pool
- Total pool of element/rate of input
41
Pools
total amount of a nutrient in a component of the ecosystem
42
Catchment or Watershed
- the land area that is drained by a single stream, is often used
- For terrestrial ecosystems
43
Measuring Nutrient Inputs and Outputs
- Atmospheric deposition includes elements in precipitation or aerosols and fine dust
- Wet deposition collectors open during precipitation events, then close to prevent evaporation
44
Early Primary Succession
- little organic matter in the soil, and little nitrogen from decomposition
- Nitrogen availability should limit primary production and community composition
45
Phosphorus (P)
- originates from weathering of the mineral apatite
- As the supply of P from weathering is exhausted over time, decomposition becomes increasingly important
46
Occlusion
- Soluble P may combine with iron, calcium, or aluminum to form insoluble compounds that are unavailable as nutrients
