Forest Ecology Production Following

Question 1

What is Net biomass accumulation ?

Answer 1

NPP - tissue loss (herbivory, litterfall, root turnover).

Question 2

What types of respirationof producers ?

Answer 2

Leaf Dark Respiration and Construction and Maintenance Respiration (other parts of the plant).

Question 3

What do decomposers do ?

Answer 3

They decompose litter material into litter and soil organic matter accumulation. responsible for part of heterotrophic respiration.

Question 4

Who does heterotrophic respiration ?

Answer 4

Consumers and decomposers.

Question 5

Net Ecosystem Production components

Answer 5

Litter and Soil Organic Matter Accumulation
Live Biomass Accumulation of Plants
Live Biomass Accumulation of Consumers

Question 6

Percentage of Primary Production of forest consumed by herbivores ?

Answer 6

4 to 7 %.

Question 7

Detritus food web vs grazing food web

Answer 7

In forests, the production goes more into the detritus food web.

Question 8

Photosynthesis (GPP) is a function of:

Answer 8

Site:
Light (daily, seasonally, during the year)
Nutrients (nitrogen, phosphate, calcium…)
Water
Temperature
Length of growing season

Plant:
Leaf area
Photosynthetic efficiency (water, nutrients)

Question 9

Autotrophic respiration is a function of:

Answer 9

Site:
Temperature

Plant:
Photosynthetic efficiency (% C lost to dark respiration)
Photosynthesizing biomass vs respiring biomass

Question 10

Lost of GPP to respiration :

Answer 10

High in 450-year-old Douglas-fire forest : 93%
As trees are getting older, stems getting older, the leaves are getting higher up into the canopy, ratio fiolage using carbon vs respiring biomass is changing.

Question 11

What controls NPP ?

Answer 11

• Temperature : sigmoid relation, NPP goes up as the temperature goes up.
• Precipitation : logarithmic, increasing relation, adding water, increased NPP but at some point plateau. Something else starts to limit the productivity.
• Soil nutrient availability: logarithmic increasing relation. more nitrogen, more aboveground NPP.
• Water balance: water stress –> closure of stomatas, plant can take up less carbon. The less the water balance, the less the NPP.

Question 12

NPP in different ecosystem types ?

Answer 12

NPP varies: tropical forests are really productive, temperate and boreal forests are less productive. Forest plantations are fairly productive, not as much as tropical forests.

Question 13

Which forest type has higher NPP per year ?

Answer 13

Tropical, then temperate, then boreal

Question 14

Which forest type has higher NPP per month during the growing season and why ?

Answer 14

Boreal, then temperate and then tropical. Boreal has a shorter growing season (3 months, compared to 6 for temperate and 12 for tropical).
Difference in daylight. Along the equator, always the same daylight. Longer during the growing season in boreal forest (northern hemisphere). adaptation to the shorter growing season

Question 15

What is water balance ?

Answer 15

Water balance = P - PE + SWC
P = monthly precipitation
PE = monthly potential evapotranspiration
SWC = monthly soil water content

Question 16

How to know if an ecosystem is a carbon source or carbon sink ?

Answer 16

NEP <0 –> source
NEP > 0 –> sink

Question 17

What is found in the DOM (dead organic matter) pool ?

Answer 17

Litter
Roots (fine and coarse)
Fine woody debris
Coarse woody debris
Forest floor
Soil carbon (ultimately)

Question 18

What controls respiration (decomposition) ?

Answer 18

Site:
Temperature
Moisture
pH
Nutrients
Oxygen
Decomposing organisms (bacteria, fungi, soil arthropods)

Substrate:
Chemical properties (amount of ligning, Carbon:Nitrogen ratio)
Physical properties (surface area to volume, hardness)

Question 19

What factors influence the rate of decomposition?

Answer 19

Moisture (5-80%) : too wet or too dry it is slower

Temperature (2-40 °C): too hot or too cold it is slower

Aeration: too low it is slower

pH (4-10:low-fungal; high-bacterial), when lower, decomposition is primary fungal, higher it is bacterial.

Litter quality (C:N ratio): higher it is slower

e.g., Carbon:Nitrogen ratio of different materials
Douglas-fir: 548:1 429:1 491:1 58:1
sapwood heartwood bark needles

Question 20

Effect of soil fauna on fractionating DOM pool ?

Answer 20

it breaks the material into smaller pieces, increase surface area available to bacteria and fungi, mix organic matter with mineral soil.

Question 21

Carbon dynamics of Canada’s forests:

Answer 21

Natural forests stores more carbon because older, but managed forests takes up (sequesters) more carbon from the atmosphere because younger.
Natural forests : carbon taken up from the atmosphere by trees and recycle back to the atmosphere trough decomposition and fires.
Managed forests : take the wood and carbon to meet society needs.
Argument of conserving forests to reduce GHG emissions. But unless we reduced society needs for timbers, fibers and energy, the needs will need to be meet through other means. Other means (aluminium, steel, concrete) have high fossil fuels emissions.
Sustainable forest management are generally compatible with objectives of good carbon management : opportunities to increase sinks and reduce sources, and develop mitigation strategies trough the management of our forests.
One of the goal of substainable forest management : balance between the amount harvested and the amount that is regrowing.
Sustainable forests can have stable carbon stocks while providing every year energy, timber and fiber to meet society’s needs.