Soil and vegetation components Ecophysiology Group - Mica Creek

Soil CO 2 flux measurements near tower at Mica Creek Automated Carbon Efflux System (ACES) Allows 16 simultaneous chamber flux measurements using one IRGA sensor Constructed by Forest Service scientists Objectives: Measure soil respiration at high temporal resolution in Northern Rockies Estimate belowground contribution of ecosystem respiration Soil Respiration Dr. John Marshall Erin Berryman (Graduate student)

Estimating Total Belowground Carbon Allocation (TBCA) Soil CO 2 flux measurements LI IRGA Soil surface flux using chambers Subtract litterfall C from total C removal (respiration) to estimate TBCA (Raich and Nadelhoffer 1989) –Mica Creek - tentative Can do this with ACES - requires installation of litterfall traps near tower –Priest River Experimental Forest (PREF) Strong landscape component to soil respiration –Measure CO 2 flux variation by: »Altitude »Slope aspect (solar radiation load)

Dissolved Organic Carbon (Blecker, Gravelle, et al.) –Seasonal DOC mass balance across the mgmt gradient (inputs – precip, stemflow, throughfall, outputs – stream water, internal transformations – litter & soil) –Quality measures of DOC through exchange resins (humic vs. non-humic) and spectrophotometry (aquatic vs. terrestrial source based on relative measure of lignin)

Nocturnal Cold Air Drainage (Blecker, Kavanagh et al.) –Begins when vertical temp gradient becomes isothermal –iButton temp measurements for ‘thickness’ of cold air layer Proposed study – Measure diurnal variation in quantity and isotopic signature of CO 2, in conjunction with vertical profile of temperature, wind speed & direction. How: Tethered balloon (rise above cold air lake, capture greater % of nocturnal CO 2 drainage), portable mast, tall trees) Possibly use SF 6 release ‘upstream’ to determine footprint (figure taken from Pypker et al – HJ Andrews)

As the evening progresses, the ‘cold air lake’ forces air from the upper portions of the watershed over the tower. Thus, the tower footprint shrinks and the quantity of CO 2 passing the tower declines (approx 30 to 60% of the CO 2 respired in the watershed) (Pypker et al – HJ Andrews)

Effects of canopy density and slope position on transpiration rates per unit leaf area in conifer forests of northern Idaho. Kathleen Kavanagh Peter Gag

Radial Sap Flow Meter (Granier 1985, 1987) Method for measuring whole-tree transpiration Measures a temperature difference between heated and reference probe. Sapwood flux creates temperature differences. Measure transpiration rates (E) and stomatal conductance (Gs)

Methods Two transects –3 sites demonstrating variation in slope postion/elevational gradient –2 sites same elevation, varied canopy structure One shared site between transects Measured at each site –5 trees of dominant and codominant crown position –All Douglas-fir (Pseudotsuga menziesii) –Soil Moisture –Temperature and humidity

Hypotheses 1) Increased rates of transpiration per unit leaf area in thinned stands. 2) Increased rates of transpiration per unit leaf as elevation increases away from riparian areas.

Remote data mgmt Telemetry: working with Senior ECE majors to design and install telemetry system for remote data access.

Katy Kavanagh, Pete Gag, Steve Blecker –Transpiration study: sap flux setup in 2005, volumetric soil moisture and soil water potential monitoring planned for 2006 Water fluxes