17. Species-specific litter decomposition

Organizers Hans Cornelissen and Will Cornwell. First meeting was held 14-18 November 2006

PARTICIPANTS Helen Quested, Stockholm U, Sweden ( VISTA, traits, decomp.) Lou Santiago,UC Riverside, USA (tropical traits, decomp.) Natalia Pérez-Harguindeguy, U Córdoba, Argentina (pfts, traits and decomposition) Bart Hoorens, U Illinois, now Vrije U, Amersterdam (global change and decomp.) David Wardle,Swedish U, Sweden (linking aboveground and belowground) Ian Wright, Macquarie U, Sydney (plant traits: Glopnet) Victor Brovkin, Potsdam, Germany (global modeller: LPJ - CENTURY), Will Cornwell, Stanford University, now Vrije U, Amsterdam (traits, decomposition, semi-arid) Hans Cornelissen, VU Amsterdam, NL (traits, decomp., global change) Valerie Eviner, University of California, Davis

18 Nov 06>

Global meta-analysis of plant trait and plant type control over litter decomposition rates

There is fast growing evidence that plant species exert strong control over decomposition rates through the ‘afterlife’ effects of traits of living plant modules (leaves, stems and branches, roots) on the quality of their litter. A growing literature also indicates that shifts in species composition, as a consequence of global changes (e.g. warming, precipitation), are strong drivers of changing litter decomposition rates in various biomes worldwide. The feedbacks of such changes to climate, through the release of CO 2 via decomposition, are paramount. Since it is not feasible to study litter decomposition rates of each individual species, plant traits and plant functional types are increasingly being used to generalize effects of (changing) plant species composition on litter decomposition. A powerful method in recent years has been to incubate litters of multiple species simultaneously in semi-natural outdoor ‘common garden experiments’, particularly in litterbeds (e.g. Cornelissen et al. 1999, New Phyt. 143: 191-200). This approach has revealed that leaf traits and plant functional types can be used as estimators of leaf litter decomposability (i.e. potential decomposition rate) for particular regional floras. However, we do not know if and how these relationships can be scaled up to biomes or the whole planet. And yet, this is the type of information that is specifically needed, but still lacking, in dynamic global dynamic vegetation models (DGVM) such as LPJ ( Sitch et al. 2003, Global Change Biology 9: 161-185). Pilot attempts to physically make this link in WG4 have been promising.

A group of scientists involved in ‘common garden’ and other multi-species litter decomposition experiments and datasets, jointly carried out analyses of cross-species relationships between functional leaf traits and leaf litter decomposability at the global scale. This task was facilitated by the ART DECO database (Assembly of Research on Traits and DECOmposition), prepared by the participants and other contributors before the meeting. We made the following advances:

1. We checked the dataset for errors and inconsistencies, identified gaps (e.g. missing geographical areas, traits, metadata); and subsequently filled some of the gaps.
2. We did various analyses to partition variance in leaf litter decomposition rates due to the various interacting drivers, trying to find and underpin similarities and differences in trait-decomposition relationships globally.
3. We did additional analyses on specific topics such as the effect of different decomposition phases or N or P limitation on carbon and nutrient turnover.
4. We did some pilots to incorporate leaf litter decomposability information by functional type or trait into LPJ in various biomes.
5. We made a template for collecting data for a possible new project, linking wood traits to wood decomposition for input into DGVMs (because of the great feedback potential to climate via carbon storage and fire regimes).

Will Cornwell will spend a one-year post-doc (from 1 Jan. 2007) with Hans Cornelissen to perform the final analyses on the complete dataset, and produce draft papers together with the other participants.

Concrete plans are being explored for getting together with a group in the near future to synthesise wood trait-decomposition relationships globally, and perhaps develop a common experimental protocol for obtaining new empirical data to fill the gaps.

Last updated December 2006