Lecture 7: Nutrient supplying and cycling

Question 1

Nutrients

Answer 1

chemical elements an organisms uses for its metabolism and growth

enter ecosystems through chemical breakdown of minerals in rocks and through fixation of gases in atmosphere

Question 2

Nutrients enter food chain with plants following chain of

Answer 2

production, consumption, decomposition, and recycling that keeps them cycling in system

Question 3

Nutrients from taken up by plants

Answer 3

C: CO2
H: H20
O: CO2/H20
N: NO3- and NH4+
P: H2PO4-
S: SO4-

Question 4

What is 90-98% of nutrients taken up from plants?

Answer 4

C, H, O

Question 5

Function of C, H, O in plants

Answer 5

C: carbohydrates and derivatives
H and O : basic building blocks for organic molecules

Question 6

N and P usually

Answer 6

limit productivity in terrestrial and aquatic ecosystems

Question 7

How do nutrients enter ecosystems?

Answer 7

Bedrock
Fixation of atmospheric gases
Atmospheric deposition

Question 8

How does bedrock help nutrients enter ecosystems?

Answer 8

Rocks contain minerals composed of nutrient elements
Weathering causes rock to breakdown and minerals to enter soil
Nutrients become available for biological processes

Question 9

What is the ulitimate source of phosphorus (and most other nutrients) that supports plant growth?

Answer 9

Minerals in bedrock

Question 10

How does fixation of atmospheric gasses help nutrients enter ecosystems?

Answer 10

Some bacteria can access N2 and turn it into biologically available form of nitrogen –> nitrogen fixation

Question 11

Air is full of N2, but issue is

Answer 11

plants and animals can not use N2 (not usable form due to strong triple bond)

Question 12

How to make N2 useful for plants?

Answer 12

nitrogen fixation: N2 –> NH4

Question 13

Nitrogen fixation

Answer 13

Convert nitrogen in atmosphere into form that can be used by living things

Bacteria: use enzyme nitrogenase to convert N2 into chemically available from NH4
lighting stirkes
Industrial, Harber Bosch process: uses lots of energy, fossil fuelss

Question 14

N fixation symbiosis

Answer 14

Plants: need nitrogen, have lots of carbon
Bacteria: can fix nitrogen, need carbon

Question 15

What is the ultimate source of nitrogen that supports plant growth

Answer 15

N2 gas in the atmosphere

Question 16

How does atmospheric deposition help nutrients enter ecosystems?

Answer 16

wind moves dust around the globe
rain can bring particles form atmosphere into the soil

Question 17

____ of primary minerals in major source of new P to ecosystem

Answer 17

Weathering

Question 18

____ is the major source of new N to ecosystems

Answer 18

Fixation

Question 19

What is problem with weathering and fixation?

Answer 19

processes take a long time

Question 20

How do plants recycle a lot of their own nutrients?

Answer 20

Leaves have high nutrient concentrations than wood
In fall, nutrients broken down in leaves and transported to stems and roots where they are stored (retraslocation)

Question 21

Detritus fuels

Answer 21

decomposition

Question 22

Microorganisms role

Answer 22

break down and mineralize nutrients (producing NH4) which is main form of soil N availability in many ecosystems

Question 22

Earthworms, termites, nematodes role in decomposition

Answer 22

consume litter and break into finer particles (increase surface area)

Question 22

Bulk of detritus is …

Answer 22

plant material: organic compounds difficult for plants and animals to take up directly

Question 22

Mineralization

Answer 22

chemical conversion of organic matter into inorganic forms

Question 23

Bacteria need carbon and nitrogen so they get from

Answer 23

detritus

Question 23

Bacteria break down litter and take

Answer 23

C and N that they need
N is sometimes left over often

Question 24

What is done with leftover N by bacteria?

Answer 24

Plants take up this leftover N in soil with their roots and use it to fuel primary production

Question 25

___ can control rates of decomposition

Answer 25

Climate

Question 26

Decomposition is faster in climate with

Answer 26

warm moist conditions

Question 27

Soil moisture influences availability of

Answer 27

water and O2 to microorganisms
wet soil have low O2 concentration to inhibit detritivores
dry soil do not have enough water fr microorganisms

Question 28

why is composition of plant litter important?

Answer 28

major control on decomposition and nutrient availability (N and P) in the soil

Question 29

Plant litter C:N is between

Answer 29

10:1 and 40:1

Question 30

Microbes need C:N to be about _____ to _____

Answer 30

25:1, build their bodies + maintenance and respiration

Question 31

What C:N is good for enriching the soil in available nitrogen?

Answer 31

40:1, microbe would use what it needs and have carbon left over, slower decomposition
10:1, microbe would use what it needs and have nitrogen left over: faster decomposition

left over released into soil and available to plants

Question 32

When N is left over from plant litter, it is used for

Answer 32

nitrogen mineralization (breakdown of organic nitrogen and production of plant available NH4 and NO3)

Question 33

Properties of litter influence decomposition rates

Answer 33

Lignin strengthen plant cell walls for soil microorganisms difficult to degrade –> decomposes slowly
secondary compounds can inhibit or promote microbial growth