the importance of lateral water fluxes and groundwater as  controlling variables

KIT – University of the State of Baden‐Wuerttemberg and  National Research Center of the Helmholtz Association

Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK‐IFU)

www.kit.edu

Soil‐atmosphere trace gas exchange ‐

the importance of lateral water fluxes and groundwater as  controlling variables

Klaus Butterbach‐Bahl, Ralf Kiese & Michael Dannenmann

Campus ‐ Alpin

IMK‐IFU: Atmospheric Environmental Research

Soils as sources and sinks for N ₂ O and CH ₄

Approx. 50% of N₂O fluxes and 20% of CH₄ fluxes are  directly linked to soil processes

Fowler et al. 2009, Atm. Environm. 43, 5193‐5267

Criteria for site selection

• Representativeness – Climate

– Vegetation

– Land use and land management – Soils

• Homogeneity

– Flat topography – Land use

– Vegetation – …

• Real world

– Inhomogenous

• Topography

• Land use/ land management

• Water routing

• Vegetation

• ..

 What do we know about the importance of „landscape

inhomogenities“ and edge effects for C/N/water/energy fluxes?

 How important is landscape water routing for biosphere‐atmosphere N  and C fluxes?

 Does this potentialy affect our view on landscape fluxes?

 Should we reconsider how we measure fluxes and how we scale fluxes?

Lysimeter field EC‐Tower

Tereno‐site Fendt

Fragmented landscape – N fluxes

Atmospheric dispersion

• Patchwork of land uses with own Nr sink/ source characteristics

• In such landscapes Nr is highly managed, transferred, emitted/ re‐deposited

• Intensive Nr interactions and transformations at landscape elements

N_r N_r

N₂

(N₂O/NO)

NO₃/ DOC

Fragmented landscape – N fluxes

Groffman et al., 2009 Biogeochemistry

NH₃

WD: well drained; MWD: moderately well drained, SPD: somewhat poorly drained, VPD: very poorly drained

Small scale variability of soil water status and effects on N ₂ O fluxes

Well‐aerated Facultative‐aerated Poorly aerated

Jungkunst et al. 2003, J. Geophys. Res. 109, D07302 Cambisol

Humic gleysol

Humic gleysol Sapric Histosol

Fibric Histosol

Groundwater level affects soil N ₂ O  fluxes

Van Beek et al. 2010, Nutr. Cycl Agroecosys. 86, 331‐340

Fragmented landscape – N fluxes

Throughfall Leaching

Spangenberg and Kölling 2004 Water, Air, and Soil Pollut.

Fragmented landscapes – C fluxes

C stock [kg m^-2]

row

column

20 40 60

20 40 60

12 14 16 18 20 22

Fragmented landscape – C fluxes

Robinson et al., 2009 Ecol Modelling

Butterbach‐Bahl – Landscape heterogeneity & C/N/H₂O fluxes

Fragmented landscape – C fluxes

Robinson et al., 2009 Ecol Modelling

Butterbach‐Bahl – Landscape heterogeneity & C/N/H₂O fluxes

Small scale variability of soil water

status and effects on CH ₄ fluxes

Water saturation deficit July 1994

Soil heterotrophic resprication July 1994 When averaged for the entire watershed, forest

productivity and soil respiration were modeled to be 8 to 11% less under simulation considering water

routing than that ignoring water routing

What is the problem?

• Atmosphere‐biosphere exchange of C and N is biased due to the selection of measuring sites

– Avoiding complexity

– Ignoring topography, water routing and deposition gradients

• Huge uncertainties with regard to fluxes and C/N  stocks hampers to identify e.g. climate change

feedbacks

• New criteria for site selection

• Additonal measurement approaches

• Advanced modeling tools

Targeting landscapes to allow and  down‐ and upscaling

Complex landscape: f (i, j, k, l, m)

iLandscape units

jFarm types

Social and  economic  environment

l Field types

Local  management

Physical  environment GIS analysis, 

remote  sensing,  land use  change

Incomes,  tenure, food 

security

Productivity,  GHG  emissions, 

activities

k Common lands

m Land types

Terrestrial Environmental Observatories

T R E N O

single lysimeter High(860m) / Graswang:

6 lysimeter 1600mm / 5°C

Medium(750m) / Rottenbuch:

12 lysimeter 1400mm / 6.5°C

Low(600m) / Fendt:

18 lysimeter 1030mm / 8.2°C

= intensive management = extensive management

MM HM

ML HL LL

service unit

∆Temp~ 2.5°C ∆Precipitation~ 300mm

N2O Emission [µg N m-2 h-1 ]

‐200 0 200 400 600 800 1000

1200 control

tranlocated mid elevation translocated high elevation

Additonal measurement approaches

Terrestrial Environmental Observatories

T R E N O

int. ext. int. ext.

0 2 4 6 8 10 12 14 16

Climate change Control

NH₄⁺-N NO₃^--N

kg N ha-1 yr-1

Climate change Control Control Climate change

int. ext. int. ext.

0,0 0,4 0,8 1,2 1,6 2,0

Winter

Autum

Summer

Spring

int. ext. int. ext.

0,0 0,4 0,8 1,2 1,6

2,0 DON-N

NO₃ NH₄ DON

N-leaching[kg N ha-1 yr-1 ]

Terrestrial Environmental Observatories

T R E N O

1d 2d

Biomass productivity gradient Indirect N₂O emissions

Coupled LandscapeDNDC – CMF simulation

Extensive grassland

Arable land Fertilization:

300 kg N/ha

Lateral nitrate transport

Total biomass production

Accumulated N₂O emissions

Legend

Soil NO₃ concentrations high

low Soil nitrate concentrations

Towards landscape measurement and  modeling approaches

Bedard‐Haughn et al., 2003,  J. Hydrol.) 

Conclusions

• Water routing, fragmentation and edge effects are enhancing/ reducing fluxes and storage of C/N at  landscape scales

• Effects remain unquantified

• New measuring/modeling strategies to assess effects

and to reduce uncertainties

• Water routing, fragmentation and edge effects are enhancing/ reducing fluxes and storage of C/N at  landscape scales

• Effects remain unquantified

• New measuring/modeling strategies to assess effects and to reduce uncertainties

Conclusions

Catchment N, water

[C] balance Gauge

advanced measuring  and modelling tools  for studying the 

complex interactions  of water, C, and N at  landscape scales

Virtual box Inventorying

• ground based

• Geostatistical

• Gradients

• ..

• Remote sensing

• Canopy (lignin content)

• NDVI

• ….

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