156 research outputs found
Enhanced rock weathering: biological climate change mitigation with co-benefits for food security?
Limited response of peatland CH<sub>4</sub> emissions to abrupt Atlantic Ocean circulation changes in glacial climates
Technologies to deliver food and climate security through agriculture
Acknowledgements D.J.B. and S.A.B. acknowledge funding from the Leverhulme Trust through a Leverhulme Research Centre Award (RC-2015-029). S.P.L. acknowledges funding from the DOE Center for Advanced Bioenergy and Bioproducts Innovation (US Department of Energy, Office of Science, Office of Biological and Environmental Research under award number DE-SC0018420). The input of P.S. contributes to the DEVIL (NE/M021327/1) and SoilsāRāGRREAT (NE/P019455/1) projects.Peer reviewedPostprin
A process-based model of conifer forest structure and function with special emphasis on leaf lifespan
We describe the University of Sheffield Conifer Model (USCM), a process-based approach for simulating conifer forest carbon, nitrogen, and water fluxes by up-scaling widely applicable relationships between leaf lifespan and function. The USCM is designed to predict and analyze the biogeochemistry and biophysics of conifer forests that dominated the ice-free high-latitude regions under the high pCO2 āgreenhouseā world 290ā50 Myr ago. It will be of use in future research investigating controls on the contrasting distribution of ancient evergreen and deciduous forests between hemispheres, and their differential feedbacks on polar climate through the exchange of energy and materials with the atmosphere. Emphasis is placed on leaf lifespan because this trait can be determined from the anatomical characteristics of fossil conifer woods and influences a range of ecosystem processes. Extensive testing of simulated net primary production and partitioning, leaf area index, evapotranspiration, nitrogen uptake, and land surface energy partitioning showed close agreement with observations from sites across a wide climatic gradient. This indicates the generic utility of our model, and adequate representation of the key processes involved in forest function using only information on leaf lifespan, climate, and soils
Ectomycorrhizal fungi and past high CO2 atmospheres enhance mineral weathering through increased below-ground carbon-energy fluxes
Field studies indicate an intensification of mineral weathering with advancement from arbuscular mycorrhizal (AM) to later-evolving ectomycorrhizal (EM) fungal partners of gymnosperm and angiosperm trees. We test the hypothesis that this intensification is driven by increasing photosynthate carbon allocation to mycorrhizal mycelial networks using 14CO2-tracer experiments with representative treeāfungus mycorrhizal partnerships. Trees were grown in either a simulated past CO2 atmosphere (1500 ppm)āunder which EM fungi evolvedāor near-current CO2 (450 ppm). We report a direct linkage between photosynthate-energy fluxes from trees to EM and AM mycorrhizal mycelium and rates of calcium silicate weathering. Calcium dissolution rates halved for both AM and EM trees as CO2 fell from 1500 to 450 ppm, but silicate weathering by AM trees at high CO2 approached rates for EM trees at near-current CO2. Our findings provide mechanistic insights into the involvement of EM-associating forest trees in strengthening biological feedbacks on the geochemical carbon cycle that regulate atmospheric CO2 over millions of years
Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering.
Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to 'trenching' of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO(2) and climate history
The role of enhanced rock weathering deployment with agriculture in limiting future warming and protecting coral reefs
Abstract: Meeting the net-zero carbon emissions commitments of major economies by mid-century requires large-scale deployment of negative emission technologies (NETs). Terrestrial enhanced rock weathering on croplands (ERW) is a NET with co-benefits for agriculture, soils and ocean acidification that creates opportunities for generating income unaffected by diminishing carbon taxes as emissions approach net-zero. Here we show that ERW deployment with croplands to deliver net 2 Gt CO2 yrā1 removal approximately doubles the probability of meeting the Paris 1.5 Ā°C target at 2100 from 23% to 42% in a high mitigation Representative Concentration Pathway 2.6 baseline climate. Carbon removal via carbon capture and storage (CCS) at the same rate had an equivalent effect. Co-deployment of ERW and CCS tripled the chances of meeting a 1.5 Ā°C target (from 23% to 67%), and may be sufficient to reverse about one third of the surface ocean acidification effect caused by increases in atmospheric CO2 over the past 200 years. ERW increased the percentage of coral reefs above an aragonite saturation threshold of 3.5 from 16% to 39% at 2100, higher than CCS, highlighting a co-benefit for marine calcifying ecosystems. However, the degree of ocean state recovery in our simulations is highly uncertain and ERW deployment cannot substitute for near-term rapid CO2 emissions reductions
Simulating carbon capture by enhanced weathering with global croplands: an overview of key processes highlighting areas of future model development
Enhanced weathering (EW) aims to amplify a natural sink for CO2 by incorporating
powdered silicate rock with high reactive surface area into
agricultural soils. The goal is to achieve rapid dissolution of minerals and
release of alkalinity with accompanying dissolution of CO2 into soils and drainage
waters. EW could counteract phosphorus limitation and greenhouse gas
(GHG) emissions in tropical soils, and soil acidification, a common agricultural
problem studied with numerical process models over several decades.
Here, we review the processes leading to soil acidification in croplands and
how the soil weathering CO2 sink is represented in models. Mathematical
models capturing the dominant processes and human interventions governing
cropland soil chemistry and GHG emissions neglect weathering, while
most weathering models neglect agricultural processes. We discuss current
approaches to modelling EW and highlight several classes of model having
the potential to simulate EW in croplands. Finally, we argue for further integration
of process knowledge in mathematical models to capture feedbacks
affecting both longer-term CO2 consumption and crop growth and yields
A new soil-based approach for empirical monitoring of enhanced rock weathering rates
Enhanced Rock Weathering (ERW) is a promising scalable and cost-effective
Carbon Dioxide Removal (CDR) strategy with significant environmental and
agronomic co-benefits. However, a major barrier to the widescale implementation
of ERW is a robust Monitoring, Reporting, and Verification (MRV) framework. To
successfully quantify the amount of carbon dioxide removed by ERW at scale, MRV
must be accurate, precise, and cost-effective. Here, we outline a new method
based on mass balance where metal analysis on soil samples is used to
accurately track the extent of in-situ alkaline mineral weathering. We show
that signal-to-noise issues of in-situ soil analysis can be mitigated by using
isotope-dilution mass spectrometry to reduce analytical error. We implement a
proof of concept experiment demonstrating the method in controlled mesocosms.
In our experiment, basalt feedstock is added to soil columns containing the
cereal crop Sorghum bicolor at a rate equivalent to 50 t ha-1. Using our
approach, we calculate an average initial CDR value of 2.24 +- 1.33 tCO2eq ha-1
from our experiments after 235 days, within error of an independent estimate
calculated using conventional elemental budgeting of reaction products. Our
result corresponds to an initial CDR efficiency of 24.4 +- 14.5 % for the
feedstock used. Our method provides a robust time-integrated estimate of
initial CDR, and offers a path to track and validate large-scale carbon removal
through ERW
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