Research Coordination Meeting: Strategic Placement and Area-wide - - PowerPoint PPT Presentation

Workshop: Relating Site Specific Insights to Landscape Features for Catchment Scale Management .

Art Gold, Professor, Univ. Rhode Island

Research Coordination Meeting: Strategic Placement and Area-wide Evaluation of Conservation Zones in Agric. Catchments IAEA/FAO Vienna, Austria December 17, 2008

Motivations For Scaling

• Inherent conceptual interest in scaling
• Interest in a micro-scale process that is

relevant at large scales, e.g. N gas fluxes

• Need to solve a specific problem at a

large scale, e.g. nitrate delivery to coastal waters, that is regulated by micro-scale processes

Overview: Relating Landscape Features to Site Process for Catchment Management

• Site Scale

– Does our sample size capture the controlling processes – the hot spot issue at the micro level? – Does our sampling design capture transformation rates at the scale of single landscape feature?

• Landscape Scale

– What “map” attributes relate to landscape features that control or reflect hot spots of transformations? – Is the mapping scale suitable to capture critical processing at the landscape scale?

Sample Size Question: Do microcosms for soil and aquifer biogeochemistry capture site processes?

• R. L. Smith, USGS

In situ Nitrate Dosing Experiment Explore Biogeochemistry on Larger Sample Volumes

Scale of Site Measurements Can Yield Major Differences in Groundwater N Removal in Hydric Soils at the Same Site

Dosing Field Study

Volume of Media (cm3) 16,000 32 Mass (g) 25,000 50 N Removal (μg kg-1 d-1) 50 < 2 N Removal Method

Microcosm Study

Conservative Tracers: Mass Balance Denitrification Gases

Nelson et al., 1995 Groffman et al., 1996

Undisturbed Mesocosms Permit Mass Balance and Process Level Studies

15 cm diam. PVC Core Extendible Pipe Hydraulic Jack with press Back side

• f pit

Side of pit where core will be extracted Seasonal High Water Table

Mesocosm Dosing Experiment

Carboy: Groundwater

Br+/5%15NO 3

15N Mesocosm Experiments:

Carbon rich microsites (1-5% by volume) in hydric cores generated the denitrification and N removal

Push-Pull Method: In Situ Denitrification Capacity

Push Pull Water Table Introduced plume: 44 kg sample size 2 cm mini-piezometer

1. Pump groundwater 2. Amend with 15NO3

• and Br-

3. Lower DO to ambient levels with gaseous SF6 4. Push (inject) into well 5. Incubate 6. Pull (pump) from well 7. Analyze samples for

15N2 and 15N2O

(products of microbial denitrification)

(Addy et al. 2002, JEQ)

Question: Does our sampling design capture transformations at the scale of a single landscape feature?

• Hubbard Brook “valley-wide” study (Schwarz,

Venterea, Lovett, Groffman)

• Are there intra-valley patterns of N transformations

that must be considered for scaling up to regional/catchment scale gas flux study?

• Can map attributes (elevation, aspect, geology,

soils, vegetation) explain variation and permit scaling from point samples?

Sampling Scheme: Hubbard Brook Watershed, NSF Long Term Ecological Research Site

1.5 km

Mean Range CV

(kg N ha-1 d-1) % N mineralization rate 1.18 0.25 - 2.33 44 Nitrification rate 0.61

• 0.01 - 1.53

71 (g N ha-1 d-1) N2O production rate 4.26

• 0.69 - 16.1

76

High valley-wide variability in point-based N transformation rates

Aspect

N m in era lization rate, Nitrification rate (kg N h a-1 d-1)

0.0 0.5 1.0 1.5 2.0

N 2O produ ction rate (g N h a-1 d-1)

0.0 0.5 1.0 1.5 2.0 N2O production

N facing S facing N facing S facing N facing S facing

a b** a b** N mineralization Nitrification

Landscape attributes (ASPECT) relate to N transformation rates

N mineralization Nitrification

Elevation

N min eralization rate, Nitrification rate (kg N h a-1 d-1)

0.0 0.5 1.0 1.5 2.0

N 2O produ ction rate (g N h a-1 d-1)

0.0 0.5 1.0 1.5 2.0 N2O production

low high

a b*** b*** a a b***

low high low high

Landscape attributes (ELEVATION) relate to N transformation rates

Dominant species

N min eralization rate, Nitrification rate (kg N ha-1 d-1)

0.0 0.5 1.0 1.5 2.0 2.5

N 2O produ ction rate (g N ha-1 d-1)

0.0 0.5 1.0 1.5 2.0

RS AB YB SM PB RS AB YB SM PB RS AB YB SM PB

N mineralization Nitrification N2O production a abcab c c* a ab ab b c***

Landscape attributes relate (SPECIES) to N transformation rates

Conclusions from valley-wide study

• There are coherent patterns of N cycling

across the landscape of the Hubbard Brook valley

• These patterns can be related to map

attributes and permit scaling up for catchment or regional gas flux estimates

Stream N Cycling Is Quite Variable

Question: Can we use landscape attributes to relate stream morphology to N removal?

Hypotheses

• Stream denitrification is stimulated by

hydrologic “connectivity” with riparian system

• Stream morphology reflects potential

connectivity

• Appropriate stream restoration increases

rates of hyporheic denitrification

Kausal et al., 2008

Possible Denitrification Pathways In Stream Ecosystems

Denitrifying Bacteria Surface water storage Algal mats Biofilms Woody debris Biofilms Hyporheic exchange

Runkel USGS

Hyporheic Exchange:

Developed vs Forested Storm Hydrographs

50 100 150 200 250 300 350 400 2 4 6 8 10 12 14 16

Time Flow Rate

• I. Natural Channel
• II. Channel with Incision

Due to Increased Runoff

Water Table Stream

• Channel Erosion
• Nonfunctional Floodplain
• Dry Riparian Soils

Developed Forested

Intensive Land Use:

• Higher flood flows
• Less recharge
• Lower Riparian Water Tables

Groffman et al, 2004

Nutrient inputs Bank Incision Removal of riparian zone

Stream Degradation

Increased Nitrogen Concentrations

Push Pull Groundwater Denitrification Studies: Low Bank (Unrestored)

High non-connected bank (Restored)

Low Bank “Connected” to Riparian Water Table (Restored)

50 100 150 200 250 300 June 2003 November 2003 June 2004 Date Denitrification Rate (μg/N/kg soil/day)

Unrestored High Bank Unrestored Low Bank Restored High Un-connected Bank Restored Low Connected Bank

Kaushal et al. (2008)

Stream morphology and genesis may provide insight into stream denitrification The Rosgen Classification System

Question: Is the mapping scale suitable to capture critical processing at the landscape scale?

Example: Geospatial data to identify high N removal riparian zones

• Can we identify narrow bands of hydric riparian

soils?

– 10 m of hydric soil width = substantial nitrate sink – 10 m < 0.02” at 1:24,000 scale

• Can we identify map features that reflect

riparian flow paths?

– Riparian Groundwater flow > > denitrification than

Surface Flow

• 100 lower order Geo-

referenced streams

• 6 transects per site
• Hydric soil width
• Presence of

seeps

• Compare to SSURGO
• Hydric status
• Geomorphic

Classification

• Measurements

Water flow T1 T2 T3 30m Stream 7.5m 7.5m

Right Bank Left Bank

T1 T2 T3

SSURGO Riparian Zone Validation Study

Soil Survey Geographic Digital Data 1:24,000 vs. Field Data

Riparian ecosystem

Surface flow (short-circuiting?)

Stream

Groundwater Seeps: Field Data

• Seeps found at 29/34 hydric till sites : Expect reduced groundwater N removal

potential in till

• No seeps found at 16/18 hydric outwash sites: Expect groundwater flow

through hydric soils with high denitrification potential

Till Hydric Soil

% of sites > 10m of hydric soils > 10m of hydric soils & NO seeps present & NO seeps present

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0

Hydric Till N= 34 Hydric Outwash N= 18 Nonhydric Till N= 17 Nonhydric Outwash N= 10 Hydric Organic& Alluvium N= 21

SSURGO Validation Study Hydro-geomorphic settings with high potential for riparian groundwater nitrate removal

30m buffer

Stream flow

T1 T2 T3 Rte 165 SPD VPD PD VPD PD SPD MWD Right bank Left bank

Soil Map Units Only Accurate for Presence/Absence

• f Hydric Soils

Field Observations:

• Ground-truth map: 3-4

drainage classes

• SSURGO composed of 1

soil map unit

Rte 165

N

Summary

• Great value in hypothesis based research

relating landscape attributes (soils, morphology, topopgrahy, plant community) to biogeochemical cycling.

• Geospatial analyses can serve to “scale-

up” site specific studies on wetland, riparian and stream functions at the catchment scale.