Stand age related differences in non-co 2 soil atmosphere GHG-exchange in wet temperate Eucalyptus forests of SE Australia

Transcription

1 Benedikt Fest Stand age related differences in non-co 2 soil atmosphere GHG-exchange in wet temperate Eucalyptus forests of SE Australia

2 Table of Content 1. Background 2. Research rationale/objectives 3. Case Studies 4. Discussion

3 Processes behind non-co2 soil GHG-flux CH4 NO NH2OH N2O NO2 NO2 CH4 CO2 H2O CH4 CH3OH HCHO CO2 HCOOH NO3 Anaerobic CH4 + O2 CH4 Oxidattion C N2O NH4 + O2 Nitrrification Denitrificattion D N2 Aerobic Aerobic Methanogen M nesis N2O Anaerobic

4 Table of Content 1. Background 2. Research rationale/objectives 3. Case Studies 4. Discussion

5 Research rationale after Dataur and Verchot 2007

6 Research rationale Uniqueness of Australian forest systems Old, weathered soils with a low nutrient t status t (especially nitrogen and phosphorous) Repeated changes to soil properties due to wildfire Direct fire effects: Physical: Increase in Bulk Density after fire Decrease in soil porosity Decrease in soil permeability Change in ph and EC Chemical: Quantity of organic matter decreases, quality changes Nutrient availability increases sometimes remarkably (NH 4 +) Biological: Composition of microbial community changes Microbial biomass decreases after Certini et al. 2005

7 Research objective Investigating the influence of the disturbance history (time since last disturbance) on soil CH 4 and N 2 O flux in wet temperate eucalypt forests of SE Australia

8 Table of Content 1. Background 2. Research rationale/objectives 3. Case Studies 4. Discussion

9 Case Study A King Lake NP Wallaby Creek, King Lake NP (ca mm precipitation y -1 ) - Chrono-sequence of 3 Eucalyptus regnans dominated forest stands that regenerated after stand replacing wildfires Young (30 years old) Mature (90 years old) Old growth (around 300+ years old)

10 Sampling approach Manual chamber incubations; to investigate seasonal variation of soil GHG exchange within forest stands and spatial variation between different aged forest stands King Lake NP: 2x10 chambers along two 50 m transects per forest stand (Project started in 2006 and seasonal measurements were taken in 2008 up to the bushfire in February 2009)

11 Additional measurements Established methods were used to determine: soil bulk density soil gravimetric, volumetric water content soil temperature soil ph and EC particle size analyses soil inorganic N status soil total N, C, litter quantity litter quality (N, C)

12 Case Study B Warra LTER Warra LTER (ca mm precipitation y -1 ) Chrono/disturbance sequence of 6 mixed Eucalyptus obliqua and Eucalyptus regnans forest stands ID History 01CS 2001 clear fell slash burn 66 CS 1966 clear fell slash burn 66S 34S 1966 wildfire 1934 wildfire 34/98S Mix of 1934 and 1898 wildfire OG Over 200 years old

13 Sampling approach Manual chamber incubations; to investigate seasonal variation of soil GHG exchange within forest stands and spatial variation between different aged forest stands Warra LTER 3 plots a 5 chambers per forest stand, seasonal (Project started t in 2009, seasonal measurements were taken until )

14 Additional measurements Established methods were used to determine: soil bulk density soil volumetric water content 2.5 soil temperature soil ph and EC particle size analyses 1 soil inorganic N status soil total N, C, litter quantity litter quality (N, C) [CH4], ppm Reaction/diffusion model (von Fischer et al. in press) Time, min Reactive gas [SF6], ppb Time, min Non-reactive gas A novel approach was used to determine soil diffusivity and methanotrophic activity at the Warra LTER (von Fischer et. al. 2009) Soil DNA extraction

15 Soil atmosphere non-co 2 GHG exchange between different age classes King Lake NP m -2 s Methan Nitrous Oxide mg CO 2 -e equivalents Y M O

16 Soil atmosphere non-co 2 GHG exchange between different age classes Warra LTER s -1 mg CO uivalents m equ Methane Nitrous Oxide CS 1966CS 1966S 1934S Tower OG

17 Table of Content 1. Background 2. Research rationale/objectives 3. Case Studies 4. Discussion

18 Difference in soil-atmosphere nitrous oxide exchange between stands of different age/disturbance history ug N m -2 hr -1 2 O-N ug N m -2 hr -1 2 O-N CS 1966CS 1966S 1934S Tower OG Y M O Warra LTER King Lake NP

19 Stand development after Ashton, 2000, Aust. J. Bot.

20 Forest soil C:N and nitrification Soil C/N ratio has been shown to determine the rate of nitrification ifi ti and mineralization in eucalypt forest soils C/N ratio can determine nitrification and mineralisation processes This might indirectly influence soil microbial activity After Attiwill & May 2001, Mar.Freshwater Res.

21 Difference in soil-atmosphere nitrous oxide exchange between stands of different age/disturbance history r -1 ug N 2 O-N m -2 hr r -1 ug N 2 O-N m -2 hr CS 1966CS 1966S 1934S Tower OG 0 Y M O GWC g*g -1 mg*kg soil -1 NO mg*kgsoil -1 NH CS 1966CS 1966S 1934S Tower OG 2001CS 1966CS 1966S 1934S Tower OG 2001CS 1966CS 1966S 1934S Tower OG GWC g*g NH mg*kg NO 3 mg*kg 4 soil soil Y M O Y M O Y M O

22 Difference in soil-atmosphere nitrous oxide exchange between stands of different age/disturbance history r -1 ug N 2 O-N m -2 hr CS 1966CS 1966S 1934S Tower OG Model Adjusted R 2 GWC g*g -1 mg*kg soil -1 NO mg*kgsoil -1 NH CS 1966CS 1966S 1934S Tower OG 2001CS 1966CS 1966S 1934S Tower OG 2001CS 1966CS 1966S 1934S Tower OG 8745 N 2 O flux = *NO

23 Differences in soil-atmosphere methane exchange between stands of different age/disturbance history ug CH 4 -C m -2 hr ug CH 4 -C m -2 hr CS 1966CS 1966S 1934S Tower OG Y M O Warra LTER King Lake NP

24 Impact of fire on CH 4 oxidation Soil biophysical factors: pore volume pore distribution pore connectivity soil compaction soil moisture soil temperature CH 4, O 2 diffu usivity CH 4 assimilation Methanotrophic Biomass/Activiy Composition metabolism Soil biochemical factors: ph, EC, C/N nutrient status Methanotrophic traits: enzyme kinetics NH 4 tolerance nutrient demands (Cu, N, P?) ph tolerance desiccation tolerance temperature response

25 Differences in soil atmosphere methane exchange between stands at Warra LTER 0-10 Model Adjusted R 2 ug CH 4 -C m -2 hr CH 4 flux = * CH 4 flux = * 3.76*D CH CS 1966CS 1966S 1934S Tower OG activity min -1 CH cm 2 min -1 4 diffusivity CS 1966CS 1966S 1934S Tower OG 2001CS 1966CS 1966S 1934S Tower OG Model Adjusted R 2 D CH4 = *S *Soil Temperature D CH4 = *Soil Temperature 6.866*VWC Model Adjusted R 2 = *Air filled porosity = *Air filled porosity *VWC 0.233

26 Summary Non-CO 2 soil atmosphere GHG fluxes are different in stands of different disturbance history for the same forest community in the same geographic area The differences can partly be attributed to stand development related changes in the soil structure and soil nutrient status For CH 4 differences in microbial activity between stands explains most of the observed differences in flux magnitude Differences in N 2 O flux magnitude between stands can be attributed to with stand development increasing soil NH 4 and NO 3 status probably due to lower soil C/N ratios. This with increased soil moisture probably leads to higher levels of denitrification ifi ti

27 Concluding Comments Þ Non-CO 2 soil atmosphere GHG fluxes are difficult to upscale due to their spatial variability Þ Better mechanistic understanding is needed to model these fluxes Þ approaches needed to characterize the soil status/and type for a given stand at one point in time that allows up scaling and modeling of Non-CO 2 GHG (this might be possible for CH 4 )

28 Soil GHG exchange in CO 2 equivalents Warra LTER King Lake NP ivalents m -2 s -1 mg CO 2 -equi CS 1966CS 1966S 1934S Tower OG Y M O Methane Nitrous Oxide Carbon Dioxide

29 Comparison with other forest systems kg N2O ha -1 y -1 kg CH4 ha -1 y CH4 ha -1 y -1 kg CH4 ha -1 y an forests (Duta taur & Verchot 2007) Northe ern Hemisphere (Smith et al. 2000) E. obliqua (Meyer et al. 1997) E. delegatensis (Khalil et al. 1990) E. delegatens sis (Fest et al. 2008) E. re egnans 30 yea ars old E. re egnans 90 yea ars old E. reg gnans 350 yea ars old Nativ ive woodland (Livesley et al. 2007) Mallee ecosystem (Galbally et al. 1996) Mou untain beech NZ (Price et al. 2003) Beech Germ many (Butterbac ach-bahl et al. 2002) Norwa way spruce (Bo orken & Beese e 2006) Rainforests OZ (Kiese et al. 2003) E. reg gnans/e.delega gatensis Warra a 01CS E. reg gnans/e.delega gatensis Warra a 66CS E. regnans/e.deleg egatensis Warr ra 66S E. regnans/e.deleg egatensis Warr ra 34S E. regn nans/e.delegat tensis Warra 89/34S E. regnans/e.dele legatensis War rra OG kg Global mean

30 Thank you! Copyright The University of Melbourne 2008