Studying Global Change Effects On Forests

Question 1

True or false
Forests account for 30% of the annual anthropogenic carbon release.

Answer 1

True

Question 2

What is said in slide 2 about the Paris agreement?

Answer 2

The Paris agreement has a goal of limiting temperature to 1.5 degree Celsius of the pre industrial level. It also identifies forests as a key component to mitigating climate change.

Question 3

True or false
The uptake of carbon dioxide (photosynthesis) and the release (respiration) are important fluxes in the global carbon cycle : both more than 15 times as high as fossil fuel emissions .

Answer 3

True

Question 4

What is mainly respiration in plants ?

Answer 4

The use of carbohydrates for growth and maintenance.

Question 5

What is the CO2 fertilisation effect?

Answer 5

This is a phenomenon where there is an increase in the rate of Photosynthesis, limited transpiration bodies to an increase in atmospheric CO2,

Question 6

In this study plants are exposed to nEw conditions to study how climate responses will impact plant processes. Name the various ways through which plants are exposed to new conditions.

Answer 6

1. Through Chamber studies
2. Through open top chambers for gas exposure .
3. Stand scale manipulation- the FACE approach.
4. Environmental gradient

Question 7

What are the advantages and disadvantages of chamber studies.

Answer 7

Advantages:
1. The ability to completely control the environment
2. This study is good for isolating responses and is normally suitable for studying processes and mechanisms.
3. From a practical poINT OF VIEW ,quite easy.

Disadvantages
Can on,y be used to study smaller tress and so not really representative of bigger tree.
Limited ecological realism.

Question 8

What is a fun fact about ozone chambers.

Answer 8

Ozone chambers are field experiments so they give the necessary ecological realism while still being able to control certain elements .

Question 9

What are gradient studies ?

Answer 9

These are studies conducted along an already existing gradient , thereby letting the environment work for the benefit of the experiment.

Question 10

What are the advantages and disadvantages of open top chamber for gas exposure?

Answer 10

Advantages:
1. Inexpensive to build
2. More ecologically realistic as compared to growth chambers .
3 good for study of gases such as Ozne (O3) and CO2.

Disadvantages:
1: has plastics wrapping around to stop gases being used in the study from escaping into the atmosphere. This plastic has an effect on the light , precipitation, oxygen and VPD that the plants within the chamber get .
2. Limited plant size.
3. Edge effects : a plant may be in the chamber but may have roots outside of the chamber being exposed to different factors.

Question 11

What are some of the advantages of the FACE ( open release systems)approach ?

Answer 11

Advantages :
1. Very high ecological realism.
2. Other environmental factors are unaffected.
3. Used for exposure studies of gases.

Disadvantages
1. Very expensive to build and run.
2. Relies on wind for gas distribution which is problematic because when the wind is blowing in the wrong direction the gas is not released.

If CO2 is the gas being studied the system does not run at night because plants do not take up CO2 since the stomata will be closed.

Question 12

Arrange the exposure methods in order of the most ecologically real.

Answer 12

Use of environmental gradient
FACE
Open top chambers
Growth chambers

Question 13

Under above ground measurements there are two systems for leaf-scale gas measurements. Name and define them.

Answer 13

Open system : here there continuous uptake of air from the outside environment. Measurements here are focused on comparing concentration levels of a particular gas or substance on sample plant with the concentration levels of reference plant.

Closed system: here the same air is recirculating over a period of time. Here measurements are focused on rate of concentration change over a period of time. If CO2 is being measured there is bound to be a reduction over time because the plant takes up CO2 for use.

Question 14

What can you say about measuring leaves in conifers and shoots ?

Answer 14

These measurements are continuous, taken every 30 mins. The only controlled in the set up is temperature, temperatures are kept a bit higher than ambient temperatures to prevent condensation.

Question 15

Fun fact about photosynthesis and how varying in efficiency it can be on the same plant.

Answer 15

Photosynthesis is much higher in newer leaves on a plant . It also increases as you go up the plant.

Question 16

For below ground measurements what are some of the methods that can be used ?

Answer 16

Chamber based methods can be used
Open methods: 1.Another procedure is when you take out soil core of the selected area , fill out a sieve bag with plain soil , pit the bag containing plain soil where the core was taken out and leave to incubate . After a while the bag is taken out and studied anything found in the bag during evaluation is as a result of the environment.
2.The use of electronic sensors can also be employed

Question 17

What are some observed effects between a nitrogen fertilised Scott’s pine stand and a control one .

Answer 17

The respiration is much higher in the control stand . This is because roots require a lot of energy to grow to reach nutrients to support plant health and so once the stand is fertilised nutrients are easily available and they’re is no need for a lot of energy to be exerted .
In fertilised stand majority of its energy goes into production of biomass for stems to be able to compete with other trees for sunlight.

So on fertilised stands fine root production is much lower than it is in control stands.
Organic matter and above ground biomass is much higher in fertilised stands than it is in control stands

Question 18

Under eco-system scale measurements, what is net ecosystem exchange (NEE)

Answer 18

This is the measure of the balance between the carbon absorbed and released by an ecosystem.

Question 19

What is the Eddy co variance method ? Write all you can say about it .

Answer 19

This a method used to measure vertical fluxes in the atmosphere.
A negative values means CO2 is being transported into the stand (negative flux)and a positive value means CO2 is being transported out of the stand (upward flux)into the atmosphere. Best suited for flat terrain .

Question 20

True or false :
Summing up above ground and below ground measurements are equal to eddy covariance measurements .

Answer 20

False . They always differ , there has been no scientifically proven reason why . But maybe in terms of respiration before some of the gases can reach the eddy setup the wind has reduced its concentration.

Question 21

Respiration increases exponentially with temp. It is advisable to study respiration at nigh as during the day photosynthesis is more prominent.

Answer 21

True

Question 22

State some last minute fun facts

Answer 22

Nitrogen is used up the most where there is a lot of light , this is because more light equates to more photosynthesis. So usually at the top of trees.

Photosynthesis has an optimal response to temp. Because at certain temperatures some enzymes start to breakdown.

Respiration still occurs at high temperatures.

Question 23

Stomata opening and transpiration

Answer 23

Water in the stomata is always 1000% and water in the atmosphere is almost always about 60%.
The difference in concentration between the stomata and atmosphere is the driving force for transpiration. There is the need to even out concentration, this driving force is normally referred to as vapour pressure deficit .

Transpiration is also influenced by the size stomata, big stomata then water passes easily, small stomata water passage is difficult.