Lecture 20 Flashcards
1
Q
Biogeochemistry
A
- the study of the physical, chemical, and biological factors that influence the movement and transformation of elements
2
Q
Understanding Biogeochemistry is Important In..
A
- Determining the availability of nutrients - chemical elements required for metabolism and growth
- Nutrients must be in certain forms for uptake by organisms
3
Q
The Rate of Physical and Chemical Transformations
A
- Determines the supply of nutrients
4
Q
Nutrient Requirements
A
- all organisms have similar nutrient requirements, but amounts and specific nutrients needed vary
5
Q
Structural Compounds of Plants
A
- Carbon (C) is the main component
- Nitrogen (N) is largely in enzymes
6
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
7
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
8
Q
C4 and CAM Plants
A
- require sodium
9
Q
Animals
A
- All require sodium
- mostly get nutrients in food as large, complex molecules
- Some are broken down; others are absorbed intact
10
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
11
Q
Minerals
A
- solid substances with characteristic chemical properties
12
Q
Rocks
A
- collections of dinnerent minerals
13
Q
Weathering
A
- the process of elements being released from rock minerals
- one of the processes that result in soil formation
14
Q
Mechanical Weathering
A
- The physical breakdown of rocks
- Exposes minerals to the processes chemical weathering
15
Q
Chemical Weathering
A
- chemical reactions release soluble forms of the mineral elements
16
Q
Soil
A
- a mix of mineral particles, organic matter, water, and organisms
17
Q
The Water
A
- contains dissolved organic matter, minerals, and gases
18
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
19
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
20
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
21
Q
Climate
A
- influences rate of soil development
22
Q
Soil Development
A
- fastest in warm, wet conditions
- In terrestrial ecosystems, the proportion of nutrients in the soil is greater
23
Q
Most of the Nutrients in these Ecosystems
A
- are in the living tree biomass
24
Q
What Contributes to Organic Matter in Soils?
A
- organisms such as plants, bacteria, and fungi
25
Organic Matter is a Reservoir of Nutrients
- Such as nitrogen and phosphorus
- Organisms also affect weathering
26
Atmospheric Sources of Nutrients
1. Nitrogen Fixation
2. Aerosols/Atmospheric Deposition
27
Nutrient Transformation
- Chemical and biological transformations in ecosystems alter the chemical form and supply of nutrients
28
Decomposition of Organic Matter
- Releases nutrients back into the ecosystem
29
Detritus
- includes dead plants, animals and microorganisms, and egested waste products
30
Decomposition
- the process by which detritivores break down detritus to obtain energy and nutrients
- releases nutrients as simple, soluble organic and inorganic compounds that can be taken up by other organisms
31
Litter
- Fresh, undecomposed organic matter on the soil surface
32
Fragmentation
- increases surface area, which facilitates chemical breakdown
33
Mineralization
- Chemical conversion of organic matter into inorganic nutrients
34
Heterotrophic Microorganisms
- release enzymes into the soil that break down organic macromolecules
35
What Determines Nutrient Availibility to Autotrophs
- Abiotic and biotic controls on decomposition and mineralization
- Decomposition and mineralization rates are faster in warm, moist conditions
36
Soil Moisture
- influences the availability of water and oxygen to microorganisms
- Wet soils: low oxygen concentrations- which inhibit detritivores
37
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
38
Nitrification
- NH3 and NH4 + are converted to NO3 – by chemoautotrophic bacteria, in aerobic conditions
39
Denitrification
- some bacteria use NO3 – as an electron acceptor, converting it into N2 and N2O, in anoxic conditions
40
Soil Fertility
- estimated from the concentration of inorganic forms of nitrogen
41
Nutrient Cycling
- influenced by climate, as temperature and moisture affect metabolic rates of the organisms involved in nutrient transformations
42
Mean Residence Time (Turnover Rate)
- amount of time on average that a molecule spends in the pool
- Total pool of element/rate of input
43
Pools
- total amount of a nutrient in a component of the ecosystem
44
Catchment or Watershed
- the land area that is drained by a single stream, is often used
- For terrestrial ecosystems
45
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
46
Early Primary Succession
- little organic matter in the soil, and little nitrogen from decomposition
- Nitrogen availability should limit primary production and community composition
47
Phosphorus (P)
- originates from weathering of the mineral apatite
- As the supply of P from weathering is exhausted over time, decomposition becomes increasingly important
48
Occlusion
- Soluble P may combine with iron, calcium, or aluminum to form insoluble compounds that are unavailable as nutrients
