scholarly journals Comment on “Mycorrhizal association as a primary control of the CO2 fertilization effect”

Science ◽  
2017 ◽  
Vol 355 (6323) ◽  
pp. 358.2-358 ◽  
Author(s):  
R. J. Norby ◽  
M. G. De Kauwe ◽  
A. P. Walker ◽  
C. Werner ◽  
S. Zaehle ◽  
...  
Keyword(s):  
Nitrogen Availability ◽  
Meta Analysis ◽  
Terrestrial Ecosystem ◽  
Mycorrhizal Symbiosis ◽  
Primary Control ◽  
Soil Nitrogen Availability ◽  
Ecosystem Responses ◽  
Mycorrhizal Association ◽  
Fertilization Effect ◽  
Enrichment Experiments

Terrer et al. (Reports, 1 July 2016, p. 72) used meta-analysis of carbon dioxide (CO2) enrichment experiments as evidence of an interaction between mycorrhizal symbiosis and soil nitrogen availability. We challenge their database and biomass as the response metric and, hence, their recommendation that incorporation of mycorrhizae in models will improve predictions of terrestrial ecosystem responses to increasing atmospheric CO2.

scholarly journals Mycorrhizal association as a primary control of the CO2 fertilization effect

Science ◽  
2016 ◽  
Vol 353 (6294) ◽  
pp. 72-74 ◽  
Author(s):  
César Terrer ◽  
Sara Vicca ◽  
Bruce A. Hungate ◽  
Richard P. Phillips ◽  
I. Colin Prentice
Keyword(s):  
Mycorrhizal Fungi ◽  
Atmospheric Carbon Dioxide ◽  
Nitrogen Availability ◽  
Arbuscular Mycorrhizal ◽  
Primary Control ◽  
Ecosystem Responses ◽  
Mycorrhizal Association ◽  
Fertilization Effect ◽  
Global Carbon ◽  
Low Nitrogen

Plants buffer increasing atmospheric carbon dioxide (CO2) concentrations through enhanced growth, but the question whether nitrogen availability constrains the magnitude of this ecosystem service remains unresolved. Synthesizing experiments from around the world, we show that CO2 fertilization is best explained by a simple interaction between nitrogen availability and mycorrhizal association. Plant species that associate with ectomycorrhizal fungi show a strong biomass increase (30 ± 3%, P < 0.001) in response to elevated CO2 regardless of nitrogen availability, whereas low nitrogen availability limits CO2 fertilization (0 ± 5%, P = 0.946) in plants that associate with arbuscular mycorrhizal fungi. The incorporation of mycorrhizae in global carbon cycle models is feasible, and crucial if we are to accurately project ecosystem responses and feedbacks to climate change.

scholarly journals Response to Comment on “Mycorrhizal association as a primary control of the CO2 fertilization effect”

Science ◽  
2017 ◽  
Vol 355 (6323) ◽  
pp. 358.3-358 ◽  
Author(s):  
César Terrer ◽  
Sara Vicca ◽  
Bruce A. Hungate ◽  
Richard P. Phillips ◽  
Peter B. Reich ◽  
...  
Keyword(s):  
Ectomycorrhizal Fungi ◽  
Arbuscular Mycorrhizae ◽  
Primary Control ◽  
Growth Responses ◽  
Co2 Fertilization ◽  
Data Set ◽  
Response Variable ◽  
Mycorrhizal Association ◽  
Fertilization Effect ◽  
Co2 Fertilization Effect

Norby et al. center their critique on the design of the data set and the response variable used. We address these criticisms and reinforce the conclusion that plants that associate with ectomycorrhizal fungi exhibit larger biomass and growth responses to elevated CO2 compared with plants that associate with arbuscular mycorrhizae.

scholarly journals Natural and anthropogenic drivers of calcium depletion in a northern forest during the last millennium

2016 ◽  
Vol 113 (25) ◽  
pp. 6934-6938 ◽  
Author(s):  
Bérangère A. Leys ◽  
Gene E. Likens ◽  
Chris E. Johnson ◽  
Joseph M. Craine ◽  
Brice Lacroix ◽  
...  
Keyword(s):  
Acid Rain ◽  
Nutrient Limitation ◽  
Nitrogen Availability ◽  
Terrestrial Ecosystem ◽  
Forest Harvesting ◽  
Forest Growth ◽  
Ecosystem Development ◽  
Ecosystem Responses ◽  
Northern Forest

The pace and degree of nutrient limitation are among the most critical uncertainties in predicting terrestrial ecosystem responses to global change. In the northeastern United States, forest growth has recently declined along with decreased soil calcium (Ca) availability, suggesting that acid rain has depleted soil Ca to the point where it may be a limiting nutrient. However, it is unknown whether the past 60 y of changes in Ca availability are strictly anthropogenic or partly a natural consequence of long-term ecosystem development. Here, we report a high-resolution millennial-scale record of Ca and 16 other elements from the sediments of Mirror Lake, a 15-ha lake in the White Mountains of New Hampshire surrounded by northern hardwood forest. We found that sedimentary Ca concentrations had been declining steadily for 900 y before regional Euro-American settlement. This Ca decline was not a result of serial episodic disturbances but instead the gradual weathering of soils and soil Ca availability. As Ca availability was declining, nitrogen availability concurrently was increasing. These data indicate that nutrient availability on base-poor, parent materials is sensitive to acidifying processes on millennial timescales. Forest harvesting and acid rain in the postsettlement period mobilized significant amounts of Ca from watershed soils, but these effects were exacerbated by the long-term pattern. Shifting nutrient limitation can potentially occur within 10,000 y of ecosystem development, which alters our assessments of the speed and trajectory of nutrient limitation in forests, and could require reformulation of global models of forest productivity.

scholarly journals The Mycorrhizal Tragedy of the Commons

2021 ◽  
Author(s):  
Nils Henriksson ◽  
Oskar Franklin ◽  
Lasse Tarvainen ◽  
John Marshall ◽  
Judith Lundberg-Felten ◽  
...  
Keyword(s):  
Mycorrhizal Fungi ◽  
Boreal Forests ◽  
Nitrogen Availability ◽  
Carbon Allocation ◽  
Tragedy Of The Commons ◽  
Nitrogen Immobilization ◽  
Mycorrhizal Symbiosis ◽  
Individual Tree ◽  
Carbon Supply ◽  
The Commons

The mycorrhizal symbiosis is ubiquitous in boreal forests. Trees and plants provide their fungal partners with photosynthetic carbon in exchange for soil nutrients like nitrogen, which is critical to the growth and survival of the plants. But plant carbon allocation to mycorrhizal symbionts can also fuel nitrogen immobilization, hampering tree growth. Here we present results from field and greenhouse experiments combined with mathematical modelling, showing that mycorrhizal fungi can be simultaneously mutualistic to an individual tree and parasitic to the networked community of trees. Mycorrhizal networks connect multiple plants and fungi, and we show that each tree gains additional nitrogen at the expense of its neighbors by supplying more carbon to the fungi. But this additional carbon supply eventually aggravates nitrogen immobilization in the shared fungal biomass. Individual trees may thus independently benefit from increasing their carbon investment to mycorrhiza, while causing a decline in nitrogen availability for the whole plant community. We illustrate the evolutionary underpinnings of this situation by drawing on the analogous the tragedy of the commons, and explain how rising atmospheric CO2 may lead to greater nitrogen immobilization in the future.

scholarly journals Reviews and syntheses: Soil N<sub>2</sub>O and NO emissions from land use and land-use change in the tropics and subtropics: a meta-analysis

2015 ◽  
Vol 12 (23) ◽  
pp. 7299-7313 ◽  
Author(s):  
J. van Lent ◽  
K. Hergoualc'h ◽  
L. V. Verchot
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Nitrogen Availability ◽  
Meta Analysis ◽  
Forest Conversion ◽  
N2o Emissions ◽  
Emission Rates ◽  
Soil N ◽  
The Tropics ◽  
No Emissions

Abstract. Deforestation and forest degradation in the tropics may substantially alter soil N-oxide emissions. It is particularly relevant to accurately quantify those changes to properly account for them in a REDD+ climate change mitigation scheme that provides financial incentives to reduce the emissions. With this study we provide updated land use (LU)-based emission rates (104 studies, 392 N2O and 111 NO case studies), we determine the trend and magnitude of flux changes with land-use change (LUC) using a meta-analysis approach (44 studies, 135 N2O and 37 NO cases) and evaluate biophysical drivers of N2O and NO emissions and emission changes for the tropics. The average N2O and NO emissions in intact upland tropical forest amounted to 2.0 ± 0.2 (n = 90) and 1.7 ± 0.5 (n = 36) kg N ha−1 yr−1, respectively. In agricultural soils annual N2O emissions were exponentially related to N fertilization rates and average water-filled pore space (WFPS) whereas in non-agricultural sites a Gaussian response to WFPS fit better with the observed NO and N2O emissions. The sum of soil N2O and NO fluxes and the ratio of N2O to NO increased exponentially and significantly with increasing nitrogen availability (expressed as NO3− / [NO3−+NH4+]) and WFPS, respectively; following the conceptual Hole-In-the-Pipe model. Nitrous and nitric oxide fluxes did not increase significantly overall as a result of LUC (Hedges's d of 0.11 ± 0.11 and 0.16 ± 0.19, respectively), however individual LUC trajectories or practices did. Nitrous oxide fluxes increased significantly after intact upland forest conversion to croplands (Hedges's d = 0.78 ± 0.24) and NO increased significantly following the conversion of low forest cover (secondary forest younger than 30 years, woodlands, shrublands) (Hedges's d of 0.44 ± 0.13). Forest conversion to fertilized systems significantly and highly raised both N2O and NO emission rates (Hedges's d of 1.03 ± 0.23 and 0.52 ± 0.09, respectively). Changes in nitrogen availability and WFPS were the main factors explaining changes in N2O emissions following LUC, therefore it is important that experimental designs monitor their spatio-temporal variation. Gaps in the literature on N oxide fluxes included geographical gaps (Africa, Oceania) and LU gaps (degraded forest, wetland (notably peat) forest, oil palm plantation and soy cultivation).

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