stoichiometric flexibility in terrestrial systems: empirical identification and incorporation into models

Seeta SistlaFebruary 17, 2021

• Biota are characterized by more narrow element ratios(C > N > P > trace elements) than their environment.

• Characteristic element ratios are necessary to catalyzemetabolic reactions and build biological components(e.g. proteins, ATP, nucleic acids).

• Metabolic pathways couple element cycles from thesub-cellular to global scales.

Ecological stoichiometry connects the environment with biota

(flexible)

Stoichiometric homeostasis vs. flexibility

Cleveland and Liptzin. 2007. Biogeochemistry. (Image adapted from: Sterner and Elser (2002))

Sistla & Schimel. 2012. New Phytologist

Stoichiometric flexibility across scales: how can it be expressed?

Sistla & Schimel. 2012. New Phytologist

Stoichiometric flexibility across scales: how can it be expressed?

Does stoichiometric flexibility in response to nutrient enrichment predictably correlate with the relative fertility of the biota or environment?

greater nutrient limitation

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Is stoichiometric plasticity predictable across nutrient richness and growth rate gradients?

Sistla et al. 2015. Oikos

(across communities) (within community)

Slower growth rate

grea

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Is stoichiometric plasticity predictable across nutrient richness and growth rate gradients?

greater P limitationgr

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Sistla et al. 2015. Oikos

C:nutrient flexibility as environmental & biological nutrient limitation

Is stoichiometric plasticity predictable across nutrient richness and growth rate gradients?

Species-level stoichiometric homoeostasis positively correlated with plant species dominance and stability in a grassland system

How does stoichiometric flexibility influence community-level properties?

Yu et al. 2010. Ecology Letters

Higher stoichiometric flexibility, coupled with stronger mycorrhizaeassociations allows the less dominant species to better resist drought.

Mariotte et al. 2017. Journal of Ecology

How does stoichiometric flexibility influence community-level properties?

stoichiometrically coupled acclimating microbe-plant-soil model

(SCAMPS)

Sistla et al. 2014. Ecological Monographs.

How does stoichiometric flexibility influence terrestrial C cycling?

Winter warming + stoichiometric flexibility: accelerates soil carbon loss

more ‘fungal-like’, higher C:N, K-selected

more ‘bacterial-like’, lower C:N, r-selected

Can we use knowledge of stoichiometric flexibility to project the consequences of extraordinary nutrient and CO2 enrichment?

Sistla and Schimel. 2012. New Phytologist

• When do we expect deviations from homeostasis at the organism and community level? Press vs. pulse disturbances? Role of intrinsic growth rate? Resource timing?

• Community-level stoichiometric flexibility can arise from either species turnover and/or from being composed of stoichiometrically flexible species Implications on ecosystem processes?

Data-modeling integration challenges in a changing world

• Identifying and integrating stoichiometric flexibility into mechanistic models Better data across spatial, temporal scales What about phosphorus? Meta-analyses to detect flexibility potential in

response to global change drivers

• Relationship(s) between degree of stoichiometric flexibility and decomposition, primary productivity, shifts in community structure under increased warming and nutrient-enrichment?

Steffen et al. Science 2015.