The first CO₂ enrichment experiment with treeline trees
Does the availability of
photosynthates
(sugar) limit tree growth at the treeline?
An in situ test in the Swiss central Alps using "free air CO2 enrichment" (FACE) may provide an answer. If
carbon limitation is a reality, CO2
enrichment should induce sustained stimulation of growth
(Handa et al. 2005).
1 - The
research site (top center).
1 - The
research site (top center).
2 -
Larix decidua
2 -
Larix decidua
3 -
Pinus uncinata
3 -
Pinus uncinata
The research site is on Stillberg (Dischma valley, Davos) in a 30 year old
treeline afforestation of the Swiss Federal Institute for Forest, Snow and Landscape
Research (WSL) and its section on snow and avalanche research (SLF), 2200 m above sea
level, 46° N.
Porous tubes emit pure CO2. A
computer controls the concentration at c. 200 ppm above ambient (556 instead
of 367 ppm at the beginning of the experiment). Strong winds from NW are screened off by a transparent wind break
(Hättenschwiler et al. 2002).
4 - CO2 tanks are ...
4
5 - ...
delivered by helicopter.
5
6 - A 3 weeks
gas supply at the helicopter platform.
6
7 - Pressure
regulator, providing CO2 at
6 bar.
7
8 - The
experimental site.
8
9 - The
control and monitoring system regulates the CO2 flow.
9
10 - Vertical
CO2-release tubes are mounted on a
hexagonal steel ring, surrounding a 27 year old individual of Pinus uncinata.
10
11 - The air
sample is drawn in through this funnel and pumped to the infra-red gas analyser
in the control and monitoring system unit.
11
12 - Strong
winds from NW are screened off by a transparent wind break.
12
13 -
Decomposition trial: known quantities of naturally senesced leaf litter are
exposed in mesh covered chambers.
13
14 - Collection of needle litter by small "litter traps".
14
15 -
Photosynthesis measurements.
15
Captions
- CO2 tanks are ...
- ...
delivered by helicopter.
- A 3 weeks
gas supply at the helicopter platform.
- Pressure
regulator, providing CO2 at
6 bar.
- The
experimental site.
- The
control and monitoring system regulates the CO2 flow.
- Vertical
CO2-release tubes are mounted on a
hexagonal steel ring, surrounding a 27 year old individual of Pinus uncinata.
- The air
sample is drawn in through this funnel and pumped to the infra-red gas analyser
in the control and monitoring system unit.
- Strong
winds from NW are screened off by a transparent wind break.
-
Decomposition trial: known quantities of naturally senesced leaf litter are
exposed in mesh covered chambers.
- Collection of needle litter by small "litter traps".
-
Photosynthesis measurements.