Doctor Laura Castaneda Gomez

Candidature

Graduated PhD 2020

Laura Castaneda GomezThesis Title

Soil organic matter dynamics under elevated CO2: mechanisms of impact

Research Project

Mycorrhizal fungi were initially defined as an association between roots and fungi that mediate plant nutrient uptake. Recent research has shown that they can also have an important role in mediating the decomposition of soil organic matter (SOM). However, research so far is scarce, shows conflicting results, and faces great methodological constraints.

Ectomycorrhizae and Arbuscular mycorrhizae are the most common fungal groups in association with roots, and most of the research unveiling their role on decomposition and nutrient cycling has been carried out with either one type or the other. In Australian native Eucalyptus-dominated forests, ECM and AMF can be present in the same root, which is rare for most ecosystems.

Both types of symbionts can vary in their saprotrophic capacities via different enzymatic production rates, the quantity and quality of carbon-rich compounds they release for free-living microbes (myco-depositions) and their nutrient uptake capabilities. These different traits could form the basis of varied mechanisms for organic matter cycling in soils.

Furthermore, increases in atmospheric carbon dioxide (CO2) levels have been observed to change the rate of C-rich rhizodeposition, which directly fuels mycorrhizal activity below ground. Both ECM and AMF have shown to increase their abundance and activity with elevated CO2 and changes in their morphological and functional traits might affect SOM dynamics in ways yet to be understood.

With this project, we want to evaluate the impact of two different types of mycorrhizal symbionts on SOM decomposition, to investigate some of the potential mechanisms involved and understand the possible changes in these dynamics with elevated CO2.  The results of this project will help to elucidate if mycorrhizal symbionts are involved in mediating ecosystems nutrient cycling and C storage in future changed conditions.

Publications

Castañeda-Gómez L, Walker JKM, Powell JR, Ellsworth DS, Pendall E, Carrillo Y, (2020) 'Impacts of elevated carbon dioxide on carbon gains and losses from soil and associated microbes in a Eucalyptus woodland', Soil Biology and Biochemistry, vol.143, Article no.107734

Jiang M, Medlyn BE, Drake JE, Duursma RA, Anderson IC, Barton CVM, Boer MM, Carrillo Y, Castaneda-Gomez L, Collins L, Crous KY, De Kauwe MG, dos Santos BM, Emmerson KM, Facey SL, Gherlenda AN, Gimeno TE, Hasegawa S, Johnson SN, Kannaste A, Macdonald CA, Mahmud K, Moore BD, Nazaries L, Neilson EHJ, Nielsen UN, Niinemets U, Noh NJ, Ochoa-Hueso R, Pathare VS, Pendall E, Pihlblad J, Pineiro J, Powell JR, Power SA, Reich PB, Renchon AA, Riegler M, Rinnan R, Rymer PD, Salomon RL, Singh BK, Smith B, Tjoelker MG, Walker JKM, Wujeska-Klause A, Yang JY, Zaehle S, Ellsworth DS, (2020) 'The fate of carbon in a mature forest under carbon dioxide enrichment', Nature, vol.580, no.7802, pp 227-231

Fry EL, De Long JR, Alvarez Garrido L, Alvarez N, Carrillo Y, Castaneda-Gomez L, Chomel M, Dondini M, Drake JE, Hasegawa S, Hortal S, Jackson BG, Jiang MK, Lavallee JM, Medlyn BE, Rhymes J, Singh BK, Smith P, Anderson IC, Bardgett RD, Baggs EM, Johnson D, (2019) 'Using plant, microbe, and soil fauna traits to improve the predictive power of biogeochemical models', Methods in Ecology and Evolution, vol.10, no.1, pp 146-157

Research Project Supervisors

Dr. Yolima Carrillo, A/Professor Jeff Powell, Professor Elise Pendall and Professor David Ellsworth