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.
Nutrient loss
Plant N
Year following
disturbance
Fires
N reservoir
What to do with recalcitrant organic
material? I.e. dead stuff that decays
VERY slowly.
% 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
Windthrow
N reservoir
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
Kelp disturbance
Open-system
N reservoir
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.
Syntheses ideas - Inorganic Nutrients
Toolik Lake ARCTIC- LTER
Plant
Plant
Soil
20
Soil
Soil
15
Plant biomass
Plant
Soil
Soil to plant redistribution
of nutrients, reset plantsoil balance and
synchrony among
nutrient cycles
10
5
Plant N
Plant C (kg C m-2)
Plant
Recovery
Fire
0
1000of nutrient
4000
2000
3000
Soil N
Years
entrainment
Years
The entrainment of nutrients into the ecosystem cycle requires a continuous balance between plant and
0
soil processes. Disturbance disrupts that balance and the synchrony of N & P cycles. 2nd succession first
reestablishes the soil-plant balance by a redistribution of nutrients, then re-accumulates lost nutrients.
ARC-LTER