Title: Unraveling the mechanisms underlying pulse dynamics of soil respiration in tropical dry forests

Abstract

Tropical dry forests are already undergoing changes in the quantity and timing of rainfall, but there is great uncertainty over how these shifts will affect belowground carbon (C) cycling. While it has long been known that dry soils quickly release carbon dioxide (CO₂) upon rewetting, the mechanisms underlying the so-called 'Birch effect' are still debated. Here, we quantified soil respiration pulses and their biotic predictors in response to simulated precipitation events in a regenerating tropical dry forest in Costa Rica. We also simulated the observed rewetting CO₂ pulses with two soil carbon models: a conventional model assuming first-order decay rates of soil organic matter, and an enzyme-catalyzed model with Michaelis–Menten kinetics. We found that rewetting of dry soils produced an immediate and dramatic pulse of CO₂, accompanied by rapid immobilization of nitrogen into the microbial biomass. However, the magnitude of the rewetting CO₂ pulse was highly variable at fine spatial scales, and was well correlated with the size of the dissolved organic C pool prior to rewetting. Both the enzyme-catalyzed and conventional models were able to reproduce the Birch effect when respiration was coupled directly to microbial C uptake, although models differed in their ability to yield realistic estimates ofmore » SOC and microbial biomass pool sizes and dynamics. Lastly, our results suggest that changes in the timing and intensity of rainfall events in tropical dry forests will exert strong influence on ecosystem C balance by affecting the dynamics of microbial biomass growth.« less

Authors:

Waring, Bonnie G. ^[1]; Powers, Jennifer S. ^[2]

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+ Show Author Affiliations

1. Univ. of Minnesota, Saint Paul, MN (United States); Utah State Univ., Logan, UT (United States)
2. Univ. of Minnesota, Saint Paul, MN (United States)

Publication Date:

Fri Oct 14 00:00:00 EDT 2016

Research Org.:

Univ. of Minnesota, St. Paul, MN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1364415

Grant/Contract Number:  

SC0014363

Resource Type:

Accepted Manuscript

Journal Name:

Environmental Research Letters

Additional Journal Information:

Journal Volume: 11; Journal Issue: 10; Journal ID: ISSN 1748-9326

Publisher:

IOP Publishing

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Birch effect; precipitation; seasonality; soil carbon; tropical dry forest