Studying deep root dynamics with Disaggregation ...

Studying deep root dynamics with Disaggregation Modelling using SIMILE: Fine root dynamics for an east central Amazonian moist tropical forest Elemer Briceño, PhD. School of Forestry, Instituto Tecnologico de Costa Rica. [email protected], Dagoberto Arias, PhD. School of Forestry, Instituto Tecnologico de Costa Rica. [email protected], Bradley Christoffersen, Amazon-Climate Interactions (Amazon-PIRE). University of Arizona. [email protected] , Scott Saleska, PhD. Department of Soil, Water, and Environmental Science. University of Arizona. [email protected], Javier Espeleta, PhD. University of Washington. [email protected]

ABSTRACT

𝑇𝑅𝑖 =∝∗ 𝐿𝑅𝑖 + 𝜃

Calculate through Minirrizotron studies, the growth, mortality and turnover rates, of fine roots as well as their decomposition (as the time from death to disappearance).

where Tri: fine root turnover rate (yr-1 ), LRi is the median fine root lifespan (days) of a given root, α and θ are fit parameters.

Integrate Minirrizotron sequence information and soil humidity data into a dynamic object based modeling environment (SIMILE) using differential equations.

Soil shaft design, setup, and instrumentation TDT Soil Moisture Sensor Minirhizotron tube

𝑇𝐼𝑛𝑣𝑖

(1)

365 𝑑𝑎𝑦𝑠 = 𝐿𝑅𝑖

(2)

where TInvi: is the fine root turnover rate calculated using the inverse method. The final turnover rate is based both on Tri and TInvi

METHODOLOGY

OBJECTIVES  To model the lifespan of fine roots in relation to soil humidity and depth.  To calculate through minirrizotron studies, the growth, mortality and turnover rates, of fine roots as well as their decomposition (as the time from death to disappearance).  To integrate minirrizotron sequence information and soil humidity data into a dynamic object based modeling environment (SIMILE) using differential equations.

e.i: Equations:

Model the lifespan of fine roots in relation to soil humidity and depth.

0.1 1.0

𝐹𝑡 = −𝐾𝑇 ∗

3.0

0.5 2.0

5.0

4.0

Depth (m)

The below ground carbon pool, contributes largely to the carbon balance of forest ecosystems; being particularly dynamic, in terms of decomposition rates and carbon recycling to the soil carbon, but such pool is often understudied. In many studies, root sampling has only taken place to a depth of 1–2 m excluding potential large quantities of carbon and its distribution. Process based models of forest ecosystems synthesize a broad array of processes from tree physiology, nutrient recycling, soil physics and chemistry. The modeling environment SIMILE permits to use “Disaggregation Modelling” in which the soil can be divided number of layers, aiding at understanding the demography of root dynamics at different depths, aiding to integrate minirhizotron data sampling information for each layer; using differential equations to define the rate of recycling of each root defined biomass pool. The present research work has collected data from belowground measurements in 2 deep soil pits (10 meter depth), one in closed canopy forest and another in an adjacent natural tree-fall gap Minirrizotron data aims to integrate object based modeling with state of the art soil profile information on root depth and dynamics to create an accurate model to aid on the soil carbon balance of tropical forest ecosystems.

The Model

𝑑𝑇 𝑑𝑧

(3)

Where, Ft: flow of heat (W*m2) KT: thermal conductivity (W*m-1*K-1) T:temperature (°C) z: distance over which the flow occurs (m).

Depth

infiltration

Thermal Conductivity

Humidity

dead roots

7.0

turn over rate

Heat Flow

10.0 Median Root Lifespan

Pit depth distribution

1.3 m

heat capacity

gamma_r20 root death

Data

Hydraulic potential

2.1 m

Soil heat Parameters

1.3 m

Root biomass

Photosyntate allocation

nutrient recycling Risk ratio

Minirhizotron photo of fine roots at 10m depth at closed canopy site in July 2010

Temperature

Recruitment

Diameter_i precipitation specific root length_i

Weather information

Minirhizotron photo showing proliferation over the course of the dry season, which occurs from July – December at this site.

Appperance Rate

REFERENCES McCormack ML, DM Eissenstat, A Prasad, EAH Smithwick. 2013. Regional scale patterns of fine root lifespan and turnover under current and future climate. Global Change Biology19:1697-1708. McCormack ML, Adams TS, Smithwick EAH, Eissenstat DM. 2014. Variability in root production, phenology and turnover rate among 12 temperate tree species. Ecology 95: 2224-2235. Poszwa, A., E. Dambrine, et al. (2002). "Do deep tree roots provide nutrients to the tropical rainforest?" Biogeochemistry 60(1): 97-118. Yavitt, J. B. and S. J. Wright (2001). "Drought and Irrigation Effects on Fine Root Dynamics in a Tropical Moist Forest, Panama." Biotropica 33(3): 421-434.

Contact: Elemer Briceño, PhD. Ecophysiology and Ecosystem Modelling School of Forest Engineering Instituto Tecnológico de Costa Rica Email: [email protected] Tel: +506-25502475

LiDAR-derived canopy heights (red high; blue low) obtained by an aircraft survey of the site.

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ACKNOWLEDGEMENTS Vicerrectoría de Investigación del Instituto Tecnológico de Costa Rica PIRE Program in Amazon-Climate Interactions. University of Arizona