1. Soil C-balance approach Experimental design at CarboZALF-D
The influence of soil erosion on CO2 fluxes in the CarboZALF manipulation experiment
Mathias Hoffmann1, Jürgen Augustin2, Michael Sommer1
Institute of Soil Landscape Research1 / Institute for Landscape Biogeochemistry2, Leibniz-Center for Agricultural Landscape Research, ZALF, Germany; contact:
Results II
Introduction
The soil landscape of the hummocky groundmoraine in NE Germany is characterized by intensive past and recent erosion. As it is still unclear how erosion influences CO2 sink / source functions of agricultural landscapes we performed a field scale erosion manipulation experiment and monitored C fluxes in/out the soil-plant system since We present here results for maize in 2011.
Soil C-balance approach
All sites show C losses
Differences in soil C balance related to growing season (GS) & differences in total yield
non-growing season (NGS) showed only small differences and lower C-balance at the eroded site
CH4
NEE
GPP
Reco
g C m-2 a-1
C-Input
C-Output
DIC/DOC
DIC/DOC
Experimental design at CarboZALF-D
 SC = NEE (GPP + Reco) + CH4-C + (C-Output - C-Input) + DIC +DOC 1 2 3
6 cm of Ap removed from an eroded site (Calcic Cutanic Luvisol, 2) and deposited in a depression (Endogleyic Collu-vic Regosol, 3) – induction of a transient state in 2009.
Reference site: non-eroded site (Albic Cutanic Luvisol, 1) assumed as steady state
Results I
- 500 g C m-2
+ 780 g C m-2
Weather conditions 2011:
Frost period during February and March (max. -15°C)
dry early springand late autumn (88 mm) interupted by an exceptional wet summer (465 mm) 3 2 1
Topographic gradient leads to a wetness / moisture gradient in the depression – consequence:
Larger differences in C balance between chambers than between sites
g C m-2 a-1
Moisture gradient
Conclusions
Induced soil erosion enhance the annual C losses at the eroded as well as the depostion site (priming?)
moisture gradients in depressions show large impact on the C balance (hot spots)
Long-term measurements (>3 years) are needed to provide reliable information about (I) Impact of climatic conditions (wet vs. dry year), (II) crops and agricultural management, (III) as well as different impact of soil erosion and deposition on annual C balance
Monitoring of GHG fluxes by 4 automatic FT-NSS chambers per site: 2.5 m height, basal area 2.25 m2, 1h measurement frequency with 5-10 min deployment time
Flux separation into ecosystem respiration (Reco), gross primary productivity (GPP) and modelling of net ecoystem exchange (NEE) due to DROESLER (2005) 1 Ap 2 Ap Ap 3 Al
g C m-2 a-1
Go- M Bt
Sd- Bt
Sd- Bt
fAa
Sd-
elCev
elCev-Sed Gr
NEE
Induced soil erosion seems to inhibit plant growth at the eroded site (lower Reco, GPP and Yield)
NEE shows significant differences between manipulated and reference, but not between eroded and deposition site
Reco
GPP
Reference: DROESLER, M. (2005): Trace gas exchange and climatic relevance of bog ecosystems , Southern Germany, Dissertation, TU Munich, Munich, Germany