Research Coordination Meeting: Strategic Placement and Area-wide Evaluation of Conservation Zones in Agric. Catchments

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1 Workshop: Relating Site Specific Insights to Landscape Features for Catchment Scale Management. Research Coordination Meeting: Strategic Placement and Area-wide Evaluation of Conservation Zones in Agric. Catchments IAEA/FAO Vienna, Austria December 17, 2008 Art Gold, Professor, Univ. Rhode Island

2 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

3 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?

4 Sample Size Question: Do microcosms for soil and aquifer biogeochemistry capture site processes? R. L. Smith, USGS

5 In situ Nitrate Dosing Experiment Explore Biogeochemistry on Larger Sample Volumes

6 Scale of Site Measurements Can Yield Major Differences in Groundwater N Removal in Hydric Soils at the Same Site Dosing Field Study Microcosm Study Volume of Media (cm 3 ) 16, Mass (g) 25, N Removal (μg kg -1 d -1 ) 50 <2 N Removal Method Conservative Tracers: Mass Balance Denitrification Gases Nelson et al., 1995 Groffman et al., 1996

7 Undisturbed Mesocosms Permit Mass Balance and Process Level Studies Seasonal High Water Table Back side of pit 15 cm diam. PVC Core Side of pit where core will be extracted Extendible Pipe Hydraulic Jack with press

8 Mesocosm Dosing Experiment Carboy: Groundwater Br+/5% 15 NO 3

9 15 N Mesocosm Experiments: Carbon rich microsites (1-5% by volume) in hydric cores generated the denitrification and N removal

10 Push-Pull Method: In Situ Denitrification Capacity 1. Pump groundwater 2. Amend with 15 NO 3 - and Br - 3. Lower DO to ambient levels with gaseous SF 6 4. Push (inject) into well 5. Incubate 6. Pull (pump) from well 7. Analyze samples for 15 N 2 and 15 N 2 O (products of microbial denitrification) (Addy et al. 2002, JEQ) Push Water Table Pull Introduced plume: 44 kg sample size 2 cm mini-piezometer

11 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?

12 Sampling Scheme: Hubbard Brook Watershed, NSF Long Term Ecological Research Site 1.5 km

13 High valley-wide variability in point-based N transformation rates Mean Range CV (kg N ha -1 d -1 ) % N mineralization rate Nitrification rate (g N ha -1 d -1 ) N 2 O production rate

14 Landscape attributes (ASPECT) relate to N transformation rates N mineralization rate, Nitrification rate (kg N ha -1 d -1 ) Aspect a b** N facing S facing N facing S facing N facing S facing N mineralization Nitrification N 2 O production a b** N 2 O production rate (g N ha -1 d -1 )

15 Landscape attributes (ELEVATION) relate to N transformation rates N mineralization rate, Nitrification rate (kg N ha -1 d -1 ) Elevation b*** a low high b*** a b*** a low high low high N 2 O production rate (g N ha -1 d -1 ) N mineralization Nitrification N 2 O production

16 Landscape attributes relate (SPECIES) to N transformation rates N mineralization rate, Nitrification rate (kg N ha -1 d -1 ) Dominant species c*** c* c abc ab ab ab b a a RS AB YB SM PB RS AB YB SM PB RS AB YB SM PB N 2 O production rate (g N ha -1 d -1 ) N mineralization Nitrification N 2 O production

17 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

18 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

19 Possible Denitrification Pathways In Stream Ecosystems Denitrifying Bacteria Woody debris Biofilms Algal mats Biofilms Hyporheic Exchange: Surface water storage Hyporheic exchange Runkel USGS

20 I. Natural Channel Intensive Land Use: Higher flood flows Less recharge Lower Riparian Water Tables Water Table Stream 400 Developed vs Forested Storm Hydrographs Developed II. Channel with Incision Due to Increased Runoff Flow Rate Forested Time Channel Erosion Nonfunctional Floodplain Dry Riparian Soils Groffman et al, 2004

21 Stream Degradation Nutrient inputs Removal of riparian zone Bank Incision Increased Nitrogen Concentrations

22 Push Pull Groundwater Denitrification Studies: Low Bank (Unrestored)

23 High non-connected bank (Restored)

24 Low Bank Connected to Riparian Water Table (Restored)

25 Denitrification Rate (μg/n/kg soil/day) Unrestored High Bank Unrestored Low Bank Restored High Un-connected Bank Restored Low Connected Bank June 2003 November 2003 June 2004 Date Kaushal et al. (2008)

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

27 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

28 SSURGO Riparian Zone Validation Study Soil Survey Geographic Digital Data 1:24,000 vs. Field Data 100 lower order Georeferenced streams 6 transects per site - Hydric soil width -Presence of seeps Compare to SSURGO -Hydric status -Geomorphic Classification -Measurements Right Bank Water flow Left Bank T1 T2 T3 7.5m 7.5m T1 T2 T3 30m Stream

29 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 Surface flow (short-circuiting?) Riparian ecosystem Stream Till Hydric Soil

30 SSURGO Validation Study Hydro-geomorphic settings with high potential for riparian groundwater nitrate removal % of sites >10m of hydric soils & NO seeps present Hydric Till N=34 Hydric Outwash N=18 Hydric Organic& Alluvium N=21 Nonhydric Till N=17 Nonhydric Outwash N=10

31 Soil Map Units Only Accurate for Presence/Absence of Hydric Soils Field Observations: N 30m buffer Right bank T1 T2 T3 Rte 165 SPD Ground-truth map: 3-4 drainage classes PD SSURGO composed of 1 soil map unit VPD PD VPD Stream flow Rte 165 SPD MWD Left bank

32 Summary Great value in hypothesis based research relating landscape attributes (soils, morphology, topopgrahy, plant community) to biogeochemical cycling. Geospatial analyses can serve to scaleup site specific studies on wetland, riparian and stream functions at the catchment scale.