spring drought effects on carbon turnover in and above temperate grasslands · 2010-11-12 · 0 0.2...
TRANSCRIPT
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Jun-16 Jun-17 Jun-18 Jun-19 Jun-20 Jun-21
prec
ipita
tion
[mm
]
0
2
4
6
8
10
12
14
16
18
20
tem
pera
ture
[°C
]
soil temp. -5cm [°C]
air temp. 2m [°C]
Spring drought effects on carbon turnover in and above temperate grasslands
SOM conferencePresqu’île de Giens (Côte d’Azur, France)19-23 September 2010
MICHAEL RIEDERER (1,2), JOHANNA PAUSCH (2), YAKOV KUZYAKOV (2), THOMAS FOKEN (1)(1) University of Bayreuth, Department of Micrometeorology, Bayreuth, Germany (2) University of Bayreuth, AgroEcoSystem Research Department (AES), Bayreuth, Germany
Contact: [email protected] / www.bayceer.uni-bayreuth.de/mm
Special thanks go to: Martin Rimmler, Jörg Hübner, Jo Olesch, Daniel Moran, Sebastian Singer, Kristin Schulz, Martin Pannek, Daniela Pfab and Steven Böttcher
Green bayceer edge (down right) marks our site!
Fig.1: Induced soil moisture difference between “drought“ and “normal” plots reached a value of 10% at point of labelling. 135 mm precipitation hav e been excluded from “drought” plots.
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
May-01 May-08 May-15 May-22 May-29 Jun-05 Jun-12 Jun-19
soil
moi
stur
e di
ffere
nce
[%]
0
2
4
6
8
10
12
14
16
18
20
prec
ipita
tion
[mm
]
sample period
mounting ofRain-out-shelters
demounting of ROS andpulse labelling
Fig.5: Soil and air temperature and precipitation during sample period. Chamber pulse labelling chambers induced no peak in soil temperature during June-16 th. Crosses mark dates of sampling.
13CO213CO2
13CO2
13CO2
13CO2
13CO2
12CO2
12CO2
12CO2
12CO2
12CO2
12CO2
12CO2
12CO2
12CO2
H2SO4+
Na213CO3
“normal“ “drought“
Fig.1: Experiment setup: “Normal” and “drought”-plots alternating arranged in a row (5 repetitions each). Soil temperature and moisture have been logged on both.
-40
0
40
80
120
160
200
240
Jun-16 Jun-17 Jun-18 Jun-19 Jun-20 Jun-21
δ13
C [‰
]
drought normal precipitation
natural abundance
above-ground biomass
Fig.8: δ13C-values of labelled above-ground biomass compared to natural abundance value.
-30.0
-25.0
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
Jun-16 Jun-17 Jun-18 Jun-19 Jun-20 Jun-21
δ13
C [‰
]
0-5
5-10
10-20
natural abundance
depth [cm]:
roots - " normal "- plots
-30.0
-25.0
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
Jun-16 Jun-17 Jun-18 Jun-19 Jun-20 Jun-21
δ13
C [‰
]
0-5
5-10
10-20
natural abundance
depth [cm]:
roots - " drought "- plots
-28.0
-27.5
-27.0
-26.5
-26.0
-25.5
-25.0
-24.5
-24.0
Jun-16 Jun-17 Jun-18 Jun-19 Jun-20 Jun-21
δ13
C [‰
]
0-5 5-10
10-20
natural abundance
soil - " normal "- plots depth [cm]:
-28.0
-27.5
-27.0
-26.5
-26.0
-25.5
-25.0
-24.5
-24.0
Jun-16 Jun-17 Jun-18 Jun-19 Jun-20 Jun-21
δ13
C [‰
]
0-5 5-10
10-20
natural abundance
soil - " drought "- plots depth [cm]:
-0.030
-0.025
-0.020
-0.015
-0.010
-0.005
0.000
0.005
0.010
0.015
Jun-16 Jun-17 Jun-18 Jun-19 Jun-20 Jun-21
EC
CO
2-flu
x [m
mol
m-2
s-1
]
Fig.6: Eddy Covariance (EC) determined atmospheric CO 2-flux 2 m above ground. Values < 0 indicate downward fluxes (ecosystem = CO 2sink) and vice versa.
Introduction
Conservation of grasslands carbon storage characteristics is desirable in times of climate change. But ecosystem function and species composition of temperate grasslands are likely to respond to precipitation change (IPCC). As long-time climate measurements suggest precipitation deficits in Southern German low mountain ranges mainly during spring, FORKAST project investigates local carbon cycle during artificially induces drought periods.
Pulse labelling experiment
The site “Voitsumra” is located on an extensively managed pasture 624 m a.s.l. After artificial 1000-year-drought period and demounting of the rain-out-shelters the plots have been labelled with stable isotope tracer (see Fig. 3 and 4).
Fig. 4: Schematic illustration of 13CO2 pulse labellingFig. 3: 13CO2 pulse labelling chambers with thermal packs, fans and carbon/acid-reservoirs inside.
Some preliminary results
Up to now about one-fifth of the samples has been analysed. The experiment setup worked well as a significant enrichment compared to natural abundance values could be found in all compartments. Tracer is shifted from green above-ground biomass (Fig.8) into the root system (Fig.9a/b). Roots in low depth show earlier and more enrichment before values get more and more equal. Soil samples show also an enrichment which stays constant during first five days of sampling (Fig.10a/b).
Meteorological conditions
The labelling experiment was accompanied by several meteorological measurements. Decreasing tempera-ture and rainfall events during third day of sampling have to be considered while analysing tracer translocation.
Fig.9a: δ13C-values of root system on normal plots Fig.9b: δ13C-values of root system on drought plots
Fig.10a: δ13C-values of soil on normal plots Fig.10b: δ13C-values of soil on drought plots
First results indicate that there is no difference between treated and untreated plots. This should not be assigned to spring drought effects in general. Climate measurements on our site show spring 2010 as unusual cold with high atmospheric humidity. Under those conditions vegetation dealt well with missing precipitation and less soil moisture.
Atmospheric C-fluxes
Atmospheric CO2 flux measurements can not provide separate fluxes from normal and drought plots, but a site specific background flux (Fig.6). After analysing all soil and plant samples we will make efforts to evaluate the influences those fluxes have on tracer translocation in biosphere and soil.
The same will be done with the results of complex atmospheric 13CO2-flux measurements (Fig.7).
-8.1
-8.0
-7.9
-7.8
-7.7
-7.6
-7.5
-7.4
22-0608:00
22-0609:00
22-0610:00
22-0611:00
22-0612:00
22-0613:00
22-0614:00
22-0615:00
22-0616:00
22-0617:00
22-0618:00
22-0619:00
δ13
C [‰
] VP
DB
updraft downdraft
Fig.7: Atmospheric 13CO2 measurement June-22 nd