Land Management, Mycorrhizal Diversity, and Soil Carbon Sequestration Mark Hunter & Tim James Ecology & Evolutionary Biology

Background & Premise Ongoing paradigm shift in understanding the origin of soil carbon stocks Declining focus on the “recalcitrance” of leaf litter inputs (Schmidt et al. 2011, Lehman & Kleber 2015) Increasing focus on root and (especially) microbial inputs in generating soil organic matter

Roots & Fungi Roots and mycorrhizal fungi appear to drive long-term carbon sequestration in boreal forest soils (Clemmensen et al. 2013) Increasing carbon storage with forest age appears related to changes in mycorrhizal fungal community composition (Clemmensen et al. 2015; Kyaschenko et al. 2017) Precise mechanisms and generality across ecosystems remain controversial (Averill et al. 2014; Terrer et al. 2016; Norby et al. 2017; Pellitier & Zak 2017)

Our Big Questions What are the relationships among mycorrhizal abundance, mycorrhizal diversity, mycorrhizal identity and soil carbon storage? Do forest management practices differ in their potential to store carbon in soils based on their mycorrhizal communities?

General Methods Field sampling of soils and their associated mycorrhizal communities in red pine and mixed hardwood forests under different management practices in the Great Lakes Region Literature search to assess the state of knowledge on land management, mycorrhizal fungi, and carbon sequestration

Field Methods Sampled 3 old growth red pine stands and 4 red pine plantations (dating from 1930s) Sampled 3 stands each of 3 hardwood management regimes (established 1951) Extensive extraction, leaving 60 sq feet/acre Medium extraction, leaving 75 sq feet/acre Unmanaged since 1905 clearcut

3 horizons x 5 cores x 16 forest stands = 240 soil samples Oa 30 cm 12.5m E 5 cm B 3 horizons x 5 cores x 16 forest stands = 240 soil samples (actually 205 after accounting for some missing horizons)

Soil Chemistry Soil carbon Soil nitrogen Chitin Ergosterol

Red Pine Plantations Favor Deeper Soil Carbon Stores Mixed Model Interaction F2,94 = 4.39, P = 0.015 (Forest Type Main Effect F1,94 = 2.82, P = 0.096)

Red Pine Plantations Also Favor Deeper Soil Nitrogen Stores Mixed Model Interaction F2,94 = 7.34, P = 0.0011 (Forest Type Main Effect F1,94 = 3.74, P = 0.0563)

Soil Chitin Concentrations Follow Patterns of Carbon Sequestration Management Main Effect F1,97 = 3.30, P =0.072

Soil Chitin Concentrations Follow Patterns of Carbon Storage REGRESSION F1,97 = 43.29, P < 0.0001

Harvesting Rate of Hardwoods Does Not Influence Soil Carbon Stores Mixed Model Management F2,84 = 0.33, P = 0.723 High rate leaves 60 sq feet remaining/acre Medium rate leaves 75 sq feet remaining/acre

Harvesting Rate of Hardwoods Does Not Influence Soil Nitrogen Stores Mixed Model Management F2,84 = 1.07, P = 0.349 High rate leaves 60 sq feet remaining/acre Medium rate leaves 75 sq feet remaining/acre

Patterns of Diversity and Identity of the Soil Fungi

In Red Pine Stands, Fungal Diversity Declines With Soil Depth and is Lower in Plantations than in Old Growth Observed OTUs Management: p = 1.057 e -7, F=34.77981 Horizon: p = 1.069 e -07, F= 20.1609 Management*Horizon: p = 0.8453, F = 0.1684 O/A

In Hardwood Stands, Soil Fungal Diversity is Highest in the O/A Soil Horizon B B Observed OTUs Management: p = 0.1158, F = 2.2087 Horizon: p =4.446e-6, F = 14.1990 Management*Horizon: p = 0.9317, F = 0.2109 O/A

Fungal Community Composition Is More Closely Associated With Soil Carbon Stores

The Structure of Soil Fungal Communities Varies Markedly Between Pines and Hardwoods = Conifer = Deciduous

Within Pine Stands, Soil Fungal Communities Vary With Stand Management and Soil Horizon O/A Management PERMANOVA: p = 0.001, F= 3.7585 Horizon p = 0.001, F=3.5385

Red Pine Plantations Host a Higher Percentage of Ectomycorrhizal Fungi Than Do Old Growth Stands

The Higher Percentage of Ectomycorrhizal Fungi in Plantation Soils Holds Across Soil Horizons Management: p = 0.0002991 F = 14.4263 Horizon: p = 0.160016 F = 1.8793 Management * Horizon: p = 0.449180, F = 0.8092 O/A

Within Hardwood Stands, Soil Fungal Communities Vary With Stand Management and Soil Horizon PERMANOVA: p = 0.001, F= 2.3415 Horizon p = 0.001, F=3.4811

Carbon Storage is Linked to Fungal Community Composition in Hardwood Forests PCoA1 F1,92 = 92.35, P<0.0001 PCoA2 F1,92 = 8.89, P=0.0037 Model r-sqd = 0.52

Low Values of both PCoA 1 and PCoA 2 are Associated with High Soil Carbon PCoA1 F1,92 = 92.35, P<0.0001 PCoA2 F1,92 = 8.89, P=0.0037 Model r-sqd = 0.52

In Hardwood Stands, the Percentage of Ectomycorrhizal Fungi Declines Under High Rates of Timber Extraction

The Lower Percentage of Ectomycorrhizal Fungi Under High Timber Extraction Holds Across Soil Horizons Management: p = 0.05959, F = 2.9106 Horizon: p = 0.48663, F = 0.7261 Management * Horizon: p = 0.99046, F = 0.0718 O/A

Overall Conclusions Pine plantations may provide a suitable tool for soil carbon storage Their soil carbon stocks correlate positively with chitin (a fungal biomarker) and with the percentage of ectomycorrhizal taxa in samples In hardwood stands, fungal community composition is a strong predictor of soil carbon stocks Moreover, representation by ectomycorrhizal fungi appears depressed under high rates of timber removal, although effects on C stocks are unclear

Plenty Left to Do! We have many analyses still to run at finer levels of resolution We want to develop an international network of colleagues who are exploring relationships among fungal community composition and C storage We want to expand our ecosystem management comparisons

Thanks! Energy Institute Lucas Michelotti Hillary Streit

Management Has No Significant Effect on the Thickness of Soil Horizons Red Pine Hardwoods

Conifer taxonomy: Order

Deciduous taxonomy: Order

Conifer taxonomy: Class

Deciduous taxonomy: Class