Noormets102904

Moisture sensitivity of ecosystem respiration in the Upper Great Lakes forests: 

Moisture sensitivity of ecosystem respiration in the Upper Great Lakes forests Labmeeting, 10.27.04

Goals: 

Goals Does ER in the Upper Midwest forest respond to moisture? Do all forests respond the same way? How to best describe moisture effects? What drives the observed response?

Outline: 

Outline ER = f (Ts) ER = f (Ts, M/SWC) M-binned R10 = f (M) Q10 = f (M) ER = f (Rain) Seasonality of ER

Methods: 

Methods Study site - Chequamegon Sampling protocols – EC Cook et al., 2004 Cook et al., in preparation Curtis et al., 2002 Davis et al., 2003 Desai et al., 2004 Euskirchen et al., in preparation Gough et al., in preparation Noormets et al., submitted

Study sites: 

Study sites

Temperature response functions: 

Temperature response functions Model fits by M10 or SWC10 class Model parameters driven by M10 & SWC10

Seasonal course of ER, Ts, M: 

Seasonal course of ER, Ts, M ER, Ts (µmol CO2 m-2 s-1, ºC) M, SWC, WT (kPa, %, cm) 2002 - mature 2003 - mature 2002 - young 2003 - young

Single R-Ts fit per growing season: 

Single R-Ts fit per growing season

Ea (J mol-1 K-1): 

Ea (J mol-1 K-1)

R10 (µmol CO2 m-2 s-1): 

R10 (µmol CO2 m-2 s-1)

R2: 

R2

R-Ts fit by M-class: 

R-Ts fit by M-class

Seasonal M10 & SWC10 dynamics: 

Seasonal M10 & SWC10 dynamics M (kPa) SWC (%)

Ea by SWC-class: 

Ea by SWC-class Ea (J mol-1 K-1)

R10 by SWC-class: 

R10 by SWC-class R10 (µmol CO2 m-2 s-1)

R2 by SWC-class: 

R2 by SWC-class

R-Ts-M fit: 

R-Ts-M fit

Ea (J mol-1 K-1): 

Ea (J mol-1 K-1)

R2: 

R2

R2, moisture effect: 

R2, moisture effect

Ea & R10 are not independent: 

Ea & R10 are not independent NEE (µmol CO2 m-2 s-1)

Ea & R10 are not independent: 

Ea & R10 are not independent

Ea vs. R10, comparison of M-classes: 

Ea vs. R10, comparison of M-classes Slope (ΔEa:ΔR10)

R-Ts-M Conclusions: 

R-Ts-M Conclusions Moisture does affect temperature-response of ER M-sensitive R10 captures M-dependent variability as well as grouping data by M-class Stand age does not affect Ea & R10 M-sensitive Ea (or Q10) did not improve model fit

R-Ts-M Problems: 

R-Ts-M Problems Ea and R10 are not independent Ea is not very stable. Related to #1.

Rain effects on ER: 

Rain effects on ER

What to expect?: 

What to expect?

Rain effect, time since last rain: 

Rain effect, time since last rain

Rain effect, time since last rain: 

Rain effect, time since last rain

Rain effect, time since last rain: 

Rain effect, time since last rain

Defining rain event threshold: 

Defining rain event threshold

ER vs. previous day’s rainfall: 

ER vs. previous day’s rainfall

Ratio of max ER to pre-rain ER: 

Ratio of max ER to pre-rain ER

Slide34: 

Ratio of max ER to pre-rain ER

Seasonal changes in ER: 

Seasonal changes in ER

SeasonalityIHW-2003: 

Seasonality IHW-2003

SeasonalityYHW-2002: 

Seasonality YHW-2002

Seasonality: 

Seasonality

Seasonality: 

Seasonality Spring > Fall Spring < Fall Spring ~ Fall

Seasonality: 

Seasonality Moisture ? – possibly, but not at all sites Substrate ? – auto- vs. heterotrophic R

Summary: 

Summary Moisture does affect ER Age does not seem to affect ER response parameters R10 & Ea Rain does affect ER the effect is short-lived it may not occur in all stands the effect may be greater in stands with higher LAI, i.e. proportional to evaporative demand There is seasonality in ER, beyond Ts- and M-effects seasonality differs between young and mature stands transition phase coincides with low SWC