Alessandro Peressotti Dip. Scienze Agrarie e Ambientali Univesita di Udine.
Mediterranean forest ecosystem under changing precipitation regimes Peressotti A., Cotrufo M.F.,...
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Mediterranean forest ecosystem under changing precipitation
regimes
Peressotti A., Cotrufo M.F., Miglietta F., Valentini R., Inglima I., Pecchiari M., Alberti
G., Arriga N., Piermatteo D., Zaldei A.
Open Science Conference on the GHG Cycle in the Northern Hemisphere Sissi-Lassithi, Crete , 14-18 November 2006
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Annual precipitation slightly decreased in Central Italy, in the
past decade …
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…and the same is forecasted to the end of the century
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Conversely, mean surface air temperature increased …
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… leading to a decrease in soil moisture content
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The MIND projectThe EU Mediterranean ecosystems under The EU Mediterranean ecosystems under INcreasing Drought project was designed to:INcreasing Drought project was designed to:
investigate the potential effects of increasing drought on Mediterranean terrestrial ecosystems;
assess ecosystem vulnerability in response to changes in rainfall patterns;
identify appropriate management strategies to protect the ecosystem from the expected changes in climate
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The consortiumThe consortium
F. Miglietta, CNR IBIMET: WP1_Coordination and experimental manipulationR. Valentini, Università della Tuscia: WP2_Ecosystem fluxesM.F. Cotrufo, Seconda Università di Napoli: WP3_Soil respiration A. Peressotti, Università di Udine: WP4_TranspirationM. Borghetti, Università della Basilicata: WP5_Ecophysiology and growthS. Raddi, Università di Firenze: WP5_Ecophysiology and growthM. Menenti, CNR ISAFOM: WP6_Remote sensingF. Magnani, Università di Bologna: WP7_Modelling
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Specific questions addressed in this talk:Specific questions addressed in this talk:
Do changes in precipitation patterns affect the annual C budget of Mediterranean forest ecosystems?
What are the main controls of soil respiration in Mediterranean ecosystems? To what extent changes in soil water moisture affect soil respiration? … Interactions with temperature??
Will persistent changes in precipitation patterns affect on the long term soil C stocks of Mediterranean forests?
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• Lat.: 42°08’ N
• Long.: 11°58’ E
• Area: 6.2 ha
• Elevation: 220 m a.s.l.
• Annual precipitation: 650 mm
• Average air temperature: 15°C
• Management: coppice
• Vegetation: non-deciduous broadleaf (Arbutus unedo)
A large scale manipulation experiment
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Wet
Dry
Control
Experimental plot layout:
DryDry = 20% of throughfall displacement, in place since April 2004
WetWet = Soil water content maintained above 10%v through irrigation, since April 2004
ControlControl = Ambient precipitation regime, in place since April 2005
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Experimental setupExperimental setup
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Climate and irrigations in 2004 and 2005
WET PLOT
DRY PLOT
A: Daily mean air temperature and rainfall
B: Soil water content and rainfall + summer irrigation
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)
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ate
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+ irrig
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)
Mea
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ure
(°C
)
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Sap flow cumulative canopy transpiration
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ET WET ET DRY SWC WET SWC DRY
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B
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2005
mm
mm
Soi
l wat
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ntS
oil w
ater
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tent
Mid summer rains
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Mean monthly soil respiration
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Month
SR
(
mo
l m
-2 s
-1)
WET DRY
* **
**
**
**
*
2004 2005
Autumn rains
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Soil respiration
Soil mostrure limits soil respiration at high soil temperature
However, very high SR values can be measured at high temperature, in dry plots
An inerpretation: easily decomposable residue accumulation during dry stess realeased at the early rains ??
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Soil temperature (°C)
SR
(u
mo
l m-2
s-1)
SRD (umol m-2 s-1)
SRW (umol m-2 s-1)
DRYmodel
WET model
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Litterfall dynamics
Litterfall
0
50
100
150
200
250
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month
g litter/m2 WET
DRY
Measured Mean Residence TimeMeasured Mean Residence Time
Leaf litter poduction increases in the wet plots but, due to increased decay rate, annual mean residence time is significanlty higher in dry plots
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Litter dynamics and long term soil carbon pools
LITTER PRODUCTION
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Ecosystem respiration in 2005
0
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g
C d
ay-1
m-2
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DOY
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Ecosystem respiration
Soil water content
gC
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y-1 m
-2S
oil
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er
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ten
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First irrigation
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gC m
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GPP wet
Reco wetGPP dry
Reco dry
NEE dry
NEE wet
Fluxes in 2005
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Conclusions:Conclusions: Enhanced summer rainfall increases canopy assimilation (GPP). However, ecosystem respiration is also strongly increased and as a result annual Net Ecosystem C sequestration is reduced.
In Mediterranean water limited systems, the expected climatic changes in rainfall regime might not influence or slightly increase ecosystem carbon uptake because is dependent on seasonal distribution of water supply
Soil respiration is controlled by temperature during moist season and by soil moisture during summer drought. Substrate availability controls respiration in warm moist soils. This leads to respiration flashes at the first late summer rains, probably due to easily degradable substrates accumulated in dry soils over summer.
On the long term, persistent summer droughts are predicted to reduce C decay proportionally more than C input, leading to an overall accumulation of soil C in active and slow pools.
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Thank you for your attention.