Carbon Mitigation and Soil Dynamics

Amilcare PorporatoPrinceton Environmental Institute & Civil and Environmental Engineering

2

Soil Carbon

Soil respiration(CO2 and to a smallerextent CH4)

Other sources: (oceans,lakes, combustionof fossil fuels...)

Carbon fixation(photosynthesis)

Plant residues

Bicarbonates in drainage

SOIL

ATMOSPHERE

PLANTSPlant respiration(CO2)

3

Duk

e Fo

rest

FAC

E si

te

CO2 Tsϑ

Pulsing C-N dynamics driven by hydro-climatic variability

4

5

Impact of soil moisture on carbon and nitrogen dynamics

Manzoni, Schimel and Porporato, Ecology 2012.

6

•NIT

•IMM-

•IMM+

MIN•

• UP-• UP+

LitterNl

HumusNh

BiomassNb

AmmoniumN+

NitrateN-

Leaching

• LE-

Nitrogen plant uptakePlant residues

• LE+

Leaching

add(C/N)ADD•

h

lh

(C/N)DECr •

•

h

h

l

l

h

lh

(C/N)DEC

(C/N)DEC

(C/N)(C/N)

r1

+

+

−

h

h

(C/N)DEC •

• b(C/N)BD

•l

l

(C/N)DEC

Manzoni and Porporato, SBB, 2007; 2009; Porporato et al. WRR 2015

−−=

−−=

+−=

−−=

−

LEUPMINdtdN

BDDECrdtdC

BDDECADDdtdC

sLsETtIdtdsnZ

lb

lll

r

...

...

)1(

)()()(

(Random) dynamical system for CN dynamics

7

waves?

Patterns of fertility?

I) From plot (m) to watershed and regional scale (km)?

Root-soil moisture-nutrients interactions may result in “fertility islands” in drylands

8

Microbes

Mineral

SOM

Decomposition and

microbial

growth

Adhesion

Adsorption and

desorption

Soil aggregate10-1000 um

Diffusion;microbial motility

Diffusion

Soil moisture

Water retention curvesand hydraulic conductivity

CO2

Nutrientavailability

II) Micro-scale: aggregate-scale dynamics(μm-mm)

soil micro-bio fluidics

III) Humid systems and wetlands

Ecohydrological controls on C and Fe cycles

R and CO2

Fe3+

Fe2+Oxi

datio

nFe reduction

C oxidation (decomposition)CO2 and HCO3 (streams)

Biology and Chemistry

Hydrology

ETRQ

Lporosity

Zr

Root-zone model

Calabrese and Porporato, Soil Biology and Biogeochem. (2019).

From clay transport to Fe redox cycle

>50% C decomposedCalabrese and Porporato, Soil Biology and Biogeochem. (2019).

Drying

Wetting

Red.Oxid.

Temperature and moisture gradient

LUQ

CAL

BAR

Other topics

1. Methane (in collaboration with X. Zhang)

2. Carbon sequestration and dissolution of parent material (granite; basalt -- with M Celia & Tom Postma).

3. Consistent formulation of all photosynthetic pathways (C3, C4, and CAM) – with Samantha Hartzell & Mark Bartlett.

Weathering

Bedrock weathering and soil formation

Baseflow, Q(h)

Leakage, L(t)

Weathering zoneh(t)

leaching frequency: p(sfc)ρ(sfc)

Calabrese et al. JGR 2017

Climate Soil

Vegetation

D. Richter, A. Bacon (pers. comm.)

Chemical depletion fraction

Calhoun, SC

White and Blum, 1995

Sugarcane

Largescale land-atmosphere feedback?

CAM Plants

Ac(ci,Tl,φ)

classic Farquhar et al. (1981) model

Circadian rhythm

z

Plant capacitance

Demand-driven stomatal conductance

Importance of epiphytes

Up to 30% of tropical forests (e.g., Nadkarni 1984; Luttge 2004; Zotz 2016)

→ Princeton GFDL climate model

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Questions?

Opunthia ficus indicagrowing on an obelisk, Ethiopia

Photo: courtesy of P. Inglese, Univ. of Palermo, Italy