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Title: Decreased summer drought affects plant productivity and soil carbon dynamics in Mediterranean woodland

Author
item COTRUFO, M - Colorado State University
item ALBERTI, G - University Of Udine
item INGLIMA, I - University Of Naples
item MARIANOVICH, H - University Of Croatia
item Lecain, Daniel
item ZALDEI, A - Institute Of Biometeorology
item PERESSOTTI, A - University Of Udine
item MIGLIETTA, F - Institute Of Biometeorology

Submitted to: Biogeosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2011
Publication Date: N/A
Citation: N/A

Interpretive Summary: Global climate change (GCC) is predicted to great alter precipitation pattern amounts and intensities. Since precipitation (and soil moisture) drive many biological processes there is interest in examining how GCC will affect carbon cycling. We conducted an experiment in the central Italy Mediterranean woodland where precipitation was reduced and increased (artificially). Plant productivity and soil Carbon were monitored over 5 years, as these are major indices of the ecosystem carbon cycle. Added precipitation increased plant productivity and soil carbon, while decreased precipitation had little effect. These results indicate critical “thresholds” for preciptation and soil moisture that will greatly change carbon cycling in this ecosystem under certain GCC scenarios.

Technical Abstract: Precipitation patters are expected to change in the Mediterranean region within the next decades, with projected decreases in total rain fall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbustus unedo L., in Central Italy, to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, namely plant-derived C input to soil and soil respiration. Replicated plots of 100 m2 were exposed to either a 20% reduction of through fall or to a water addition by targeted irrigation during summer months, to maintain soils above a soil water content of 10% v/v. Treatments were compared to control plots which received ambient rain. The through fall manipulation experiment started in 2004 and we report data up to the 2009-2010 growing season. Enhanced soil moisture during summer months highly stimulated annual ANPP, litter fall and soil C input, which on average increased by 130%, 41% and 50%, respectively as compared to control. Soil C input was stimulated in excess of soil respiration, which resulted in increased soil C stocks in the short-term (+13%). On the contrary, the 20% reduction in trough fall did not significantly change soil moisture at the site, and therefore did not significantly affect NPP or soil respiration. However, at the fifth year of experimental through fall exclusion, annual litter fall was reduced in dry plots as compared to control. We conclude that minor changes (around 10% reduction) in rain fall amount are not likely to significantly affect NPP or soil C dynamics in Mediterranean woodland. However, if summer rain will increase, C cycling will significantly accelerate and soil C stocks will be enhanced in the short-term. More studies modelling long term dynamics are needed to predict if the observed increase in soil C input under wet conditions is going to be sustained, or if labile C is being substituted to stabile C, with a reverse effects on long term soil C stores.