A dynamic local scale vegetation model for lycophytes (LYCOm)

Abstract. Lycophytes (club mosses) represent a distinct lineage of vascular plants with a long evolutionary history including numerous extant and extinct species which started out as herbaceous plants and later evolved into woody plants. They enriched the soil carbon pool through newly developed root-like structures and promoted soil microbial activity by providing organic matter. These plants enhanced soil carbon dioxide (CO2) via root respiration and also modified soil hydrology. These effects had the potential to promote the dissolution of silicate minerals, thus intensifying silicate weathering. The weathering of silicate rocks is considered one of the most significant geochemical regulators of atmospheric CO2 on a long (hundreds of thousands to millions of years) timescale. The motivation for this study is to achieve an increased understanding of the realized impacts of vascular plants, represented by modern relatives to the most basal plants with vascular tissue and shallow root system, on silicate weathering and past climate. To this end, it is necessary to quantify physiological characteristics, spatial distribution, carbon balance, and the hydrological impacts of early lycophytes. These properties, however, cannot be easily derived from proxies such as fossil records, for instance. Hence, as a first step, a process-based model is developed here to estimate net carbon uptake by these organisms at the local scale, considering key features such as biomass distribution above and below ground, root distribution in soil regulating water uptake by plants besides, stomatal regulation of water loss and photosynthesis, and not withholding respiration in roots. The model features ranges of key physiological traits of lycophytes to predict the emerging characteristics of the lycophyte community under any given climate by implicitly simulating the process of selection. In this way, also extinct plant communities can be represented. In addition to physiological properties, the model also simulates weathering rates using a simple limit-based approach and estimates the biotic enhancement of weathering by lycophytes. We run the Lycophyte model, called LYCOm, at seven sites encompassing various climate zones under today’s climatic conditions. LYCOm is able to simulate realistic properties of lycophyte communities at the respective locations and estimates values of Net Primary Production (NPP) ranging from 126 g carbon m−2 year−1 to 245 g carbon m−2 year−1. Our limit-based weathering model predicts a mean chemical weathering rate ranging from 5.3 to 45.1 cm ka−1 rock with lycophytes varying between different sites, as opposed to 0.6–8.3 cm rock ka−1 without lycophytes, thereby highlighting the potential importance of such vegetation at the local scale for enhancing chemical weathering. Our modeling study establishes a basis for assessing biotic enhancement of weathering by lycophytes at the global scale and also for the geological past. Although our method is associated with limitations and uncertainties, it represents a novel, complementary approach towards estimating the impacts of lycophytes on biogeochemistry and climate.

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Impacts of early vegetation on biogeochemical cycles

10.5194/egusphere-egu21-12315 ◽

2021 ◽

Author(s):

Suman Halder ◽

Philipp Porada

Keyword(s):

Soil Carbon ◽

Root Respiration ◽

Chemical Weathering ◽

Soil Microbial Activity ◽

Global Scale ◽

Local Scale ◽

Climatic Conditions ◽

Silicate Weathering ◽

Soil Microbial ◽

Simple Limit

Lycophytes (club mosses) represent a distinct lineage of vascular plants with a long history including numerous extant and extinct species. They enriched the soil carbon pool through newly developed root-like structures and promoted soil microbial activity by providing organic matter. They enhanced soil carbon dioxide (CO2) via root respiration and also modified soil hydrology. These effects had the potential to promote the dissolution of silicate minerals, thus intensifying silicate weathering. The weathering of silicate rocks is considered one of the most significant geo-chemical regulators of atmospheric CO2 on a long (hundreds of thousands to millions of years) timescale. The motivation for this study is to achieve an increased understanding of the realized impacts of lycophytes on silicate weathering and past climate. To this end, it is necessary to quantify physiological characteristics, spatial distribution, the carbon balance, and hydrological impacts of early lycophytes. These properties, however, cannot be easily derived from proxies. Hence, as a first step, a process-based model is developed here to estimate net carbon uptake by these organisms at the local scale, considering key features such as root distribution, stomatal regulation of water loss, and root respiration. The model features ranges of key physiological traits of lycophytes to predict the emerging characteristics of the lycophyte community under any given climate by implicitly simulating the process of selection. In this way, also extinct plant communities can be represented. In addition to physiological properties, the model also simulates weathering rates using a simple limit-based approach and estimates the biotic enhancement of weathering by lycophytes. We run the Lycophyte model, called LYCOm, at seven sites encompassing various climate zones under today's climatic conditions. LYCOm is able to simulate realistic properties of lycophyte communities at the respective locations and estimates an average NPP ranging from 245 g carbon m-2 year-1 in Costa Rica to 126 g carbon m-2 year-1 in Estonia. Our limit-based weathering model predicts a chemical weathering rate ranging from 0.026 to 0.31 mm rock a-1 , thereby highlighting the potential importance of lycophytes at the local scale for enhancing chemical weathering. Our modeling study establishes a basis for assessing biotic enhancement of weathering by lycophytes at the global scale and also for the geological past.&#160;

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Continental weathering using combined Hf-Nd isotope system and clay mineralogy: new insights for the Late Cretaceous climate

10.5194/egusphere-egu21-11995 ◽

2021 ◽

Author(s):

Pauline Corentin ◽

Emmanuelle Puceat ◽

Pierre Pellenard ◽

Nicolas Freslon ◽

Michel Guiraud ◽

...

Keyword(s):

Clay Mineral ◽

Late Cretaceous ◽

Chemical Weathering ◽

Clay Mineralogy ◽

Global Scale ◽

Climatic Conditions ◽

Silicate Weathering ◽

Nd Isotope ◽

Continental Weathering ◽

The Impact

The Late Cretaceous period records a pronounced decrease in marine temperatures at a global scale initiating the last greenhouse-icehouse transition, whose origin still remains enigmatic. Continental weathering represents a major sink of atmospheric CO2 through silicate weathering reactions yet the importance of this process in the Late Cretaceous cooling has only been scarcely explored.In this study we explore the impact of the eastern South American margin uplift, concomitant to the long-term Late Cretaceous cooling, on the evolution of chemical weathering of the Brazilian margin, using a new proxy of silicate weathering based on the coupled Lu-Hf and Sm-Nd isotope systems in clays. This proxy, expressed as &#916;&#949;Hf, has been recently calibrated in modern environments (Bayon et al., 2016) but has only been scarcely applied to deep-time environments. This proxy, applied on sediments from DSDP site 356 on the S&#227;o Paulo Plateau, highlights a marked increase in silicate chemical weathering of the southeastern Brazilian margin from the Santonian to the Maastrichtian, also supported by the evolution of the chemical index of alteration (CIA) and clay mineralogy.This increase follows an episode of enhanced mechanical erosion of the margin revealed in the Turonian to Santonian by an increase of primary clay mineral (illite, chlorite) and Ti/Al ratio, linked to the tectonic uplift of the margin. Clay mineral assemblages additionally point to an evolution of local climatic conditions from arid to a more hydrolysing climate following this episode, that we link to a &#8220;rain shadow effect&#8221; affecting the eastern side of the newly formed relief that would have enhanced chemical weathering of the margin.Importantly the temporal coincidence of the increase in chemical weathering depicted here with the marked acceleration of the global cooling recorded worldwide during the Campanian points to a potentially important role of this process on the overall climate decline initiating the descent into our icehouse climate mode. Although records from additional sites are needed to establish the spatial extent of the margin affected by this process, our new dataset brings new insights about the impact of tectonic forcing on climate.Bayon et al. (2016) EPSL 438, p. 25-36.

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Global silicate weathering flux overestimated because of sediment–water cation exchange

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2016430118 ◽

2020 ◽

Vol 118 (1) ◽

pp. e2016430118

Author(s):

Edward T. Tipper ◽

Emily I. Stevenson ◽

Victoria Alcock ◽

Alasdair C. G. Knight ◽

J. Jotautas Baronas ◽

...

Keyword(s):

Cation Exchange ◽

River Water ◽

Chemical Weathering ◽

Global Scale ◽

Mineral Weathering ◽

Climate Feedback ◽

Silicate Weathering ◽

Exchange Equilibrium ◽

Silicate Mineral ◽

River Water Chemistry

Rivers carry the dissolved and solid products of silicate mineral weathering, a process that removesCO2from the atmosphere and provides a key negative climate feedback over geological timescales. Here we show that, in some river systems, a reactive exchange pool on river suspended particulate matter, bonded weakly to mineral surfaces, increases the mobile cation flux by 50%. The chemistry of both river waters and the exchange pool demonstrates exchange equilibrium, confirmed by Sr isotopes. Global silicate weathering fluxes are calculated based on riverine dissolved sodium (Na+) from silicate minerals. The large exchange pool supplies Na+of nonsilicate origin to the dissolved load, especially in catchments with widespread marine sediments, or where rocks have equilibrated with saline basement fluids. We quantify this by comparing the riverine sediment exchange pool and river water chemistry. In some basins, cation exchange could account for the majority of sodium in the river water, significantly reducing estimates of silicate weathering. At a global scale, we demonstrate that silicate weathering fluxes are overestimated by 12 to 28%. This overestimation is greatest in regions of high erosion and high sediment loads where the negative climate feedback has a maximum sensitivity to chemical weathering reactions. In the context of other recent findings that reduce the netCO2consumption through chemical weathering, the magnitude of the continental silicate weathering fluxes and its implications for solid EarthCO2degassing fluxes need to be further investigated.

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Faculty Opinions recommendation of Climate-driven thresholds in reactive mineral retention of soil carbon at the global scale.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.734948735.793560678 ◽

2019 ◽

Author(s):

Ying-Ping Wang

Keyword(s):

Soil Carbon ◽

Global Scale

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Towards a representation of priming on soil carbon decomposition in the global land biosphere model ORCHIDEE (version 1.9.5.2)

Geoscientific Model Development ◽

10.5194/gmd-9-841-2016 ◽

2016 ◽

Vol 9 (2) ◽

pp. 841-855 ◽

Cited By ~ 15

Author(s):

Bertrand Guenet ◽

Fernando Esteban Moyano ◽

Philippe Peylin ◽

Philippe Ciais ◽

Ivan A Janssens

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Soil Carbon ◽

Global Scale ◽

Soil Incubation ◽

First Order ◽

Carbon Decomposition ◽

Litter Manipulation ◽

Global Land ◽

Biosphere Model

Abstract. Priming of soil carbon decomposition encompasses different processes through which the decomposition of native (already present) soil organic matter is amplified through the addition of new organic matter, with new inputs typically being more labile than the native soil organic matter. Evidence for priming comes from laboratory and field experiments, but to date there is no estimate of its impact at global scale and under the current anthropogenic perturbation of the carbon cycle. Current soil carbon decomposition models do not include priming mechanisms, thereby introducing uncertainty when extrapolating short-term local observations to ecosystem and regional to global scale. In this study we present a simple conceptual model of decomposition priming, called PRIM, able to reproduce laboratory (incubation) and field (litter manipulation) priming experiments. Parameters for this model were first optimized against data from 20 soil incubation experiments using a Bayesian framework. The optimized parameter values were evaluated against another set of soil incubation data independent from the ones used for calibration and the PRIM model reproduced the soil incubations data better than the original, CENTURY-type soil decomposition model, whose decomposition equations are based only on first-order kinetics. We then compared the PRIM model and the standard first-order decay model incorporated into the global land biosphere model ORCHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems). A test of both models was performed at ecosystem scale using litter manipulation experiments from five sites. Although both versions were equally able to reproduce observed decay rates of litter, only ORCHIDEE–PRIM could simulate the observed priming (R2 = 0.54) in cases where litter was added or removed. This result suggests that a conceptually simple and numerically tractable representation of priming adapted to global models is able to capture the sign and magnitude of the priming of litter and soil organic matter.

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Radiocarbon Age of Soils in Oases of East Antarctica

Radiocarbon ◽

10.1017/rdc.2016.75 ◽

2016 ◽

Vol 59 (2) ◽

pp. 489-503 ◽

Cited By ~ 6

Author(s):

E Zazovskaya ◽

N Mergelov ◽

V Shishkov ◽

A Dolgikh ◽

V Miamin ◽

...

Keyword(s):

Organic Matter ◽

Vascular Plants ◽

High Arctic ◽

Climatic Conditions ◽

East Antarctica ◽

Radiocarbon Age ◽

Antarctic Soils ◽

Larsemann Hills ◽

Arctic Soils ◽

Organic Horizons

AbstractThis article discusses radiocarbon dating results for soils and soil-like systems in the East Antarctic oases, including Schirmacher, Thala Hills, and Larsemann Hills. The organic matter of endolithic and hypolithic systems, soils of wind shelters, and soils under moss-algae vegetation were dated along with micro- and macroprofiles. Organic matter pools formed under extreme climatic conditions and originated not from vascular plants but from cryptogamic organisms, and photoautotrophic microbes have been identified within the oases of the East Antarctica. The organic matter of the most of East Antarctic soils is young and cannot reach a steady state because of the high dynamism in the soil cover due to active erosion. The oldest soil organic matter in East Antarctica was found in the soils formed in wind shelters and endolithic soil-like systems under the protection of consolidated rock surfaces. According to our data, the maximal duration for the formation of organic matter profiles within the oases of East Antarctica is ~500 yr, which is similar to the age determined for High Arctic soils in Eurasia. The absence of older soils, comparable with the Holocene deglaciation, can be due to the extreme conditions resulting in occasional catastrophic events that destroyed the soil organic horizons.

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Global‐ and Local‐Scale High‐Resolution Event Catalogs for Algorithm Testing

Seismological Research Letters ◽

10.1785/0220180345 ◽

2019 ◽

Cited By ~ 1

Author(s):

Lisa Linville ◽

Ronald Chip Brogan ◽

Christopher Young ◽

Katherine Anderson Aur

Keyword(s):

Global Scale ◽

Local Scale ◽

Algorithm Performance ◽

Directional Information ◽

Event Sequences ◽

University Of Utah ◽

International Monitoring ◽

Using Data ◽

The University ◽

Global And Local

ABSTRACT During the development of new seismic data processing methods, the verification of potential events and associated signals can present a nontrivial obstacle to the assessment of algorithm performance, especially as detection thresholds are lowered, resulting in the inclusion of significantly more anthropogenic signals. Here, we present two 14 day seismic event catalogs, a local‐scale catalog developed using data from the University of Utah Seismograph Stations network, and a global‐scale catalog developed using data from the International Monitoring System. Each catalog was built manually to comprehensively identify events from all sources that were locatable using phase arrival timing and directional information from seismic network stations, resulting in significant increases compared to existing catalogs. The new catalogs additionally contain challenging event sequences (prolific aftershocks and small events at the detection and location threshold) and novel event types and sources (e.g., infrasound only events and long‐wall mining events) that make them useful for algorithm testing and development, as well as valuable for the unique tectonic and anthropogenic event sequences they contain.

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On the potential vegetation feedbacks that enhance phosphorus availability – insights from a process-based model linking geological and ecological timescales

Biogeosciences ◽

10.5194/bg-11-3661-2014 ◽

2014 ◽

Vol 11 (13) ◽

pp. 3661-3683 ◽

Cited By ~ 19

Author(s):

C. Buendía ◽

S. Arens ◽

T. Hickler ◽

S. I. Higgins ◽

P. Porada ◽

...

Keyword(s):

Biomass Production ◽

Primary Productivity ◽

Chemical Weathering ◽

Production Efficiency ◽

Root Exudation ◽

Terrestrial Ecosystems ◽

Global Scale ◽

P Uptake ◽

P Availability ◽

P Limitation

Abstract. In old and heavily weathered soils, the availability of P might be so small that the primary production of plants is limited. However, plants have evolved several mechanisms to actively take up P from the soil or mine it to overcome this limitation. These mechanisms involve the active uptake of P mediated by mycorrhiza, biotic de-occlusion through root clusters, and the biotic enhancement of weathering through root exudation. The objective of this paper is to investigate how and where these processes contribute to alleviate P limitation on primary productivity. To do so, we propose a process-based model accounting for the major processes of the carbon, water, and P cycles including chemical weathering at the global scale. Implementing P limitation on biomass synthesis allows the assessment of the efficiencies of biomass production across different ecosystems. We use simulation experiments to assess the relative importance of the different uptake mechanisms to alleviate P limitation on biomass production. We find that active P uptake is an essential mechanism for sustaining P availability on long timescales, whereas biotic de-occlusion might serve as a buffer on timescales shorter than 10 000 yr. Although active P uptake is essential for reducing P losses by leaching, humid lowland soils reach P limitation after around 100 000 yr of soil evolution. Given the generalized modelling framework, our model results compare reasonably with observed or independently estimated patterns and ranges of P concentrations in soils and vegetation. Furthermore, our simulations suggest that P limitation might be an important driver of biomass production efficiency (the fraction of the gross primary productivity used for biomass growth), and that vegetation on old soils has a smaller biomass production rate when P becomes limiting. With this study, we provide a theoretical basis for investigating the responses of terrestrial ecosystems to P availability linking geological and ecological timescales under different environmental settings.

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Networks of Photos, Landmarks, and People

Leonardo ◽

10.1162/leon_a_00172 ◽

2011 ◽

Vol 44 (3) ◽

pp. 240-243 ◽

Cited By ~ 6

Author(s):

David Crandall ◽

Noah Snavely

Keyword(s):

Recent Work ◽

Human Behavior ◽

Visual Representations ◽

3D Models ◽

Global Scale ◽

Local Scale ◽

Photo Sharing ◽

The World ◽

Vantage Points ◽

Combining Information

Social photo-sharing sites like Flickr contain vast amounts of latent information about the world and human behavior. The authors describe their recent work in building automatic algorithms that analyze large collections of imagery in order to extract some of this information. At a global scale, geo-tagged photographs can be used to identify the most photographed places on Earth, as well as to infer the names and visual representations of these places. At a local scale, the authors build detailed 3D models of a scene by combining information from thousands of 2D photographs taken by different people and from different vantage points.

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Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale

10.26686/wgtn.12469334.v1 ◽

2020 ◽

Author(s):

E Sebastián-González ◽

JM Barbosa ◽

JM Pérez-García ◽

Z Morales-Reyes ◽

F Botella ◽

...

Keyword(s):

Species Richness ◽

Human Impact ◽

Large Scale ◽

Diversity Index ◽

Global Scale ◽

Climatic Conditions ◽

Ecosystem Functions ◽

Number Of Species ◽

Terrestrial Vertebrate ◽

Latitudinal Patterns

© 2019 John Wiley & Sons Ltd Understanding the distribution of biodiversity across the Earth is one of the most challenging questions in biology. Much research has been directed at explaining the species latitudinal pattern showing that communities are richer in tropical areas; however, despite decades of research, a general consensus has not yet emerged. In addition, global biodiversity patterns are being rapidly altered by human activities. Here, we aim to describe large-scale patterns of species richness and diversity in terrestrial vertebrate scavenger (carrion-consuming) assemblages, which provide key ecosystem functions and services. We used a worldwide dataset comprising 43 sites, where vertebrate scavenger assemblages were identified using 2,485 carcasses monitored between 1991 and 2018. First, we evaluated how scavenger richness (number of species) and diversity (Shannon diversity index) varied among seasons (cold vs. warm, wet vs. dry). Then, we studied the potential effects of human impact and a set of macroecological variables related to climatic conditions on the scavenger assemblages. Vertebrate scavenger richness ranged from species-poor to species rich assemblages (4–30 species). Both scavenger richness and diversity also showed some seasonal variation. However, in general, climatic variables did not drive latitudinal patterns, as scavenger richness and diversity were not affected by temperature or rainfall. Rainfall seasonality slightly increased the number of species in the community, but its effect was weak. Instead, the human impact index included in our study was the main predictor of scavenger richness. Scavenger assemblages in highly human-impacted areas sustained the smallest number of scavenger species, suggesting human activity may be overriding other macroecological processes in shaping scavenger communities. Our results highlight the effect of human impact at a global scale. As species-rich assemblages tend to be more functional, we warn about possible reductions in ecosystem functions and the services provided by scavengers in human-dominated landscapes in the Anthropocene.

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