Role of disturbance in altering biogeochemical cycling John Melack Sherri Johnson Roger Ruess Mark Harmon Gus Shavers Tim Hollibaugh Dan Reed John Blair Hugh Ducklow Rhett Jackson

Disturbance – an abrupt change (relative to generation time of reference taxa) in available elemental content. We are presenting a conceptual model designed to foster comparisons across ecosystems. We are suggesting an empirical analysis to test this model over a subset of ecosystems. We seek to examine changes in disturbance regimes with respect to frequency or magnitude in the context of climate change.

What to do with recalcitrant organic material? I.e. dead stuff that decays VERY slowly. Year following disturbance Nutrient loss % Biomass removal, or % Biomass reorganization Evaluate different types of disturbance that still can be quantified in terms of their disturbance intensity and response. Variation in response will differ between open and closed systems. Plant N N reservoir Fires

What to do with recalcitrant organic material? I.e. dead stuff that decays VERY slowly. Variation in response will differ between open and closed systems. Plant N N reservoir Windthrow

What to do with recalcitrant organic material? I.e. dead stuff that decays VERY slowly. Variation in response will differ between open and closed systems. Plant N N reservoir Kelp disturbance Open-system

Syntheses ideas - Inorganic Nutrients Toolik Lake ARCTIC- LTER ARC-LTER Soil to plant redistribution of nutrients, reset plant- soil balance and synchrony among nutrient cycles The entrainment of nutrients into the ecosystem cycle requires a continuous balance between plant and soil processes. Disturbance disrupts that balance and the synchrony of N & P cycles. 2 nd succession first reestablishes the soil-plant balance by a redistribution of nutrients, then re-accumulates lost nutrients. Re-accumulate lost nutrients Plant biomass Years of nutrient entrainment