A Hydrological Framework for Biogeochemical Studies Helmut Elsenbeer1 and Jorge Marcos de Moraes2   1Institute of Geoecology, University of Potsdam, Germany 2CENA/Universidade de São Paulo, Piracicaba, Brazil

Overview The archetypal nutrient cycling scenery The link between hydrological pathways and nutrient flow The risk of ignoring hydrology in biogeochemical studies Hydrological flowpaths as we know them Get to know your catchment: tools for a rapid hydrologic appraisal

The Archetypal Scenery: Ecosystem Fluxes and Stores of Nitrogen (N) and Potassium (K) N K Precipitation Throughfall Litter fall N K Shallow soil water Forest floor Deep soil water Streamflow

The Archetypal Scenery: Ecosystem Fluxes of Dissolved Nitrogen (N) and Potassium (K) N K Precipitation Throughfall Litter fall N K Shallow soil water Forest floor Deep soil water Streamflow

Possible Hydrological Flowpaths Precipitation Lateral, near-surface flowpaths Deep percolation

The Archetypal Scenery Meets Hydrology Precipitation Streamflow Throughfall Shallow soil water Deep soil water Precipitation Lateral, near-surface flowpaths  Deep percolation

Flowpaths and Water Chemistry Near-Surface Lateral Flow NO3-, DOC, K >> Si, Ca, Na Deep Lateral Flow Si, Ca, Na >> NO3-, DOC, K

The Watershed Chemistry of Potassium Ignoring Hydrologic Pathways (Assuming Verticality) Precipitation Throughfall Soil water, 30 cm Soil water, 60 cm Soil water, 90 cm Riparian zone Groundwater Baseflow 20 40 60 80 100 120 K (µmol/L))

The Watershed Chemistry of Potassium Taking into Account Hydrologic Pathways Precipitation Throughfall Overland flow Return flow Pipeflow Soil water, 30 cm Soil water, 60 cm Soil water, 90 cm Riparian zone Groundwater Baseflow 20 40 60 80 100 120 K (µmol/L))

Stormflow Hydrograph and Chemograph Discharge 2.4 Overland flow K/SiO2 (molar ratio) Chemograph 6 2.0 1.6 4 Return flow Discharge (L/s) 1.2 2 0.8 0.4 0.0 1 2 3 4 5 Time (h)

Stormflow Hydrograph and Chemograph 50 Discharge Chemograph 6 40 4 30 Discharge (L/s) Ca (µmol/L) Overland flow 2 20 Return flow 10 1 2 3 4 5 Time (h)

Interpreting the Solute Signal: Where do the Nutrients Come From? Sources Stream response Flowpaths Throughfall Discharge Overland flow Soil water Through- flow Groundwater Solute Signal

Lateral Hydrological Flowpaths in Rainforest Ecosystems Central Amazônia Central Amazônia Peninsular Malaysia Panama Rondônia Paragominas Panama Peruvian Amazon Queensland Rondônia

A Hierarchical Approach to Understanding Hydrochemical Flowpaths Level 4 Hydrochemistry Level 3 Flowpath hydrographs Soil water or groundwater energy status Level 2 Saturation deficit Soil moisture status Infiltrability Permeability changes with depth Level 1 Rainfall intensities, amount, and frequency

Top Level Information on Shaky Ground Flowpath hydrographs Infiltrability Permeability changes with depth Soil water or groundwater energy status Rainfall intensities, amount, and frequency Saturation deficit Soil moisture status Hydrochemistry Level 4 Level 3 Level 2 Level 1

Bottom Level Information Solid Basis for Bottom-Up Inference Hydrochemistry Level 3 Flowpath hydrographs Soil water or groundwater energy status Level 2 Saturation deficit Soil moisture status Infiltrability Permeability changes with depth Level 1 Rainfall intensities, amount, and frequency

Mid-Level Information Weak Explanatory Basis Hydrochemistry Level 3 Flowpath hydrographs Soil water or groundwater energy status Level 2 Saturation deficit Soil moisture status Infiltrability Permeability changes with depth Level 1 Rainfall intensities, amount, and frequency

Possible Hydrological Flowpaths Precipitation Lateral, near-surface flowpaths Deep percolation

Overland flow

ISCO sampler Water-level recorder Venturi flume

A Hierarchical Approach to Understanding Hydrochemical Flowpaths Level 4 Hydrochemistry Level 3 Flowpath hydrographs Soil water or groundwater energy status Level 2 Saturation deficit Soil moisture status Infiltrability Permeability changes with depth Level 1 Rainfall intensities, amount, and frequency