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D. Sihi
Department of Environmental Sciences Emory University Atlanta GA USA

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Research article
Published: 18 August 2021 in Reviews of Geophysics
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A reanalysis is a physically consistent set of optimally merged simulated model states and historical observational data, using data assimilation. High computational costs for modelled processes and assimilation algorithms has led to Earth system specific reanalysis products for the atmosphere, the ocean and the land separately. Recent developments include the advanced uncertainty quantification and the generation of biogeochemical reanalysis for land and ocean. Here, we review atmospheric and oceanic reanalyses, and more in detail biogeochemical ocean and terrestrial reanalyses. In particular, we identify land surface, hydrologic and carbon cycle reanalyses which are nowadays produced in targeted projects for very specific purposes. Although a future joint reanalysis of land surface, hydrologic and carbon processes represents an analysis of important ecosystem variables, biotic ecosystem variables are assimilated only to a very limited extent. Continuous data sets of ecosystem variables are needed to explore biotic-abiotic interactions and the response of ecosystems to global change. Based on the review of existing achievements, we identify five major steps required to develop terrestrial ecosystem reanalysis to deliver continuous data streams on ecosystem dynamics.

ACS Style

R. Baatz; H. J. Hendricks Franssen; E. Euskirchen; D. Sihi; M. Dietze; S. Ciavatta; K. Fennel; H. Beck; G. De Lannoy; V. R. N. Pauwels; A. Raiho; C. Montzka; M. Williams; U. Mishra; C. Poppe; S. Zacharias; A. Lausch; L. Samaniego; K. Van Looy; H. Bogena; M. Adamescu; M. Mirtl; A. Fox; K. Goergen; B. S. Naz; Y. Zeng; H. Vereecken. Reanalysis in Earth System Science: Toward Terrestrial Ecosystem Reanalysis. Reviews of Geophysics 2021, 59, 1 .

AMA Style

R. Baatz, H. J. Hendricks Franssen, E. Euskirchen, D. Sihi, M. Dietze, S. Ciavatta, K. Fennel, H. Beck, G. De Lannoy, V. R. N. Pauwels, A. Raiho, C. Montzka, M. Williams, U. Mishra, C. Poppe, S. Zacharias, A. Lausch, L. Samaniego, K. Van Looy, H. Bogena, M. Adamescu, M. Mirtl, A. Fox, K. Goergen, B. S. Naz, Y. Zeng, H. Vereecken. Reanalysis in Earth System Science: Toward Terrestrial Ecosystem Reanalysis. Reviews of Geophysics. 2021; 59 (3):1.

Chicago/Turabian Style

R. Baatz; H. J. Hendricks Franssen; E. Euskirchen; D. Sihi; M. Dietze; S. Ciavatta; K. Fennel; H. Beck; G. De Lannoy; V. R. N. Pauwels; A. Raiho; C. Montzka; M. Williams; U. Mishra; C. Poppe; S. Zacharias; A. Lausch; L. Samaniego; K. Van Looy; H. Bogena; M. Adamescu; M. Mirtl; A. Fox; K. Goergen; B. S. Naz; Y. Zeng; H. Vereecken. 2021. "Reanalysis in Earth System Science: Toward Terrestrial Ecosystem Reanalysis." Reviews of Geophysics 59, no. 3: 1.

Research article
Published: 06 August 2021 in Journal of Geophysical Research: Biogeosciences
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A long-standing goal of ecology has been to understand the cycling of carbon in forests. This has taken on new urgency with the need to address a rapidly changing climate. Forests serve as long-term stores for atmospheric CO2, but their continued ability to take up new carbon is dependent on future changes in climate and other factors such as age. We have been measuring many aspects of carbon cycling at an unmanaged evergreen forest in central Maine, USA, for over 25 years. Here we use these data to address questions about the magnitude and control of carbon fluxes and quantify flows and uncertainties between the different pools. A key issue was to assess whether recent climate change and an aging tree population were reducing annual C storage.Total ecosystem C stocks determined from inventory and quantitative soil pits were about 23,300 g C m-2 with 46% in live trees, and 48% in the soil. Annual biomass increment in trees at Howland Forest averaged 161±23 g C m-2 yr-1, not significantly different from annual net ecosystem production (NEP = -NEE) of 211 ± 40 g C m-2 y-1 measured by eddy covariance. Unexpectedly, there was a small but significant trend of increasing C uptake through time in the eddy flux data. This was despite the period of record including some of the most climate-extreme years in the last 125. We find a surprising lack of influence of climate variability on annual carbon storage in this mature forest.

ACS Style

D. Y. Hollinger; E. A. Davidson; S. Fraver; H. Hughes; J. T. Lee; A. D. Richardson; K. Savage; D. Sihi; A. Teets. Multi‐Decadal Carbon Cycle Measurements Indicate Resistance to External Drivers of Change at the Howland Forest AmeriFlux Site. Journal of Geophysical Research: Biogeosciences 2021, 126, 1 .

AMA Style

D. Y. Hollinger, E. A. Davidson, S. Fraver, H. Hughes, J. T. Lee, A. D. Richardson, K. Savage, D. Sihi, A. Teets. Multi‐Decadal Carbon Cycle Measurements Indicate Resistance to External Drivers of Change at the Howland Forest AmeriFlux Site. Journal of Geophysical Research: Biogeosciences. 2021; 126 (8):1.

Chicago/Turabian Style

D. Y. Hollinger; E. A. Davidson; S. Fraver; H. Hughes; J. T. Lee; A. D. Richardson; K. Savage; D. Sihi; A. Teets. 2021. "Multi‐Decadal Carbon Cycle Measurements Indicate Resistance to External Drivers of Change at the Howland Forest AmeriFlux Site." Journal of Geophysical Research: Biogeosciences 126, no. 8: 1.

Article
Published: 13 July 2021 in Water, Air, & Soil Pollution
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The Animas River provides irrigation water in northwestern New Mexico and the Navajo Nation. Concerns regarding the river water quality arose on August 5, 2015, when approximately 11.35 million liters of heavy metal contaminated water was accidentally released from the Gold King Mine into the Animas River. This study sought to determine the total concentrations of 7 heavy metal(loid)s (As, Pb, and Zn as metals of concern and Fe, Mn, Ca, and Cu as metals of interest) using portable X-ray fluorescence (PXRF) in two agricultural fields and compare these values to Environmental Protection Agency (EPA) regional screening levels (RSL). Total concentrations of 6 out of 7 metals were below the RSL; only As exceeded the soil screening value of 7.07 mg kg−1 at some locations in the agricultural fields. We also determined water-soluble (WS) and exchangeable fractions (Ex) of As that might be available for agricultural crop uptake using sequential extractions. The WS-As ranged from 0.014 to 0.074 mg kg−1 and Ex-As ranged from 0.135 to 0.248 mg kg−1 and thus were less than 1 and 3% of the total As concentration respectively (ranging from 5.62 to 14.79 mg kg−1) and not considered a threat for plant tissue accumulation. While the concentrations of As observed in the agricultural fields may have exceeded screening levels, the As was not apparently plant available and its risk to crops was determined to be low.

ACS Style

Gaurav Jha; April L. Ulery; Kevin Lombard; Dawn VanLeeuwen; Colby Brungard; Biswanath Dari; Debjani Sihi. Portable X-ray Fluorescence (PXRF) Analysis of Total Metal(loid)s and Sequential Extraction of Bioavailable Arsenic in Agricultural Soils of Animas Watershed. Water, Air, & Soil Pollution 2021, 232, 1 -14.

AMA Style

Gaurav Jha, April L. Ulery, Kevin Lombard, Dawn VanLeeuwen, Colby Brungard, Biswanath Dari, Debjani Sihi. Portable X-ray Fluorescence (PXRF) Analysis of Total Metal(loid)s and Sequential Extraction of Bioavailable Arsenic in Agricultural Soils of Animas Watershed. Water, Air, & Soil Pollution. 2021; 232 (7):1-14.

Chicago/Turabian Style

Gaurav Jha; April L. Ulery; Kevin Lombard; Dawn VanLeeuwen; Colby Brungard; Biswanath Dari; Debjani Sihi. 2021. "Portable X-ray Fluorescence (PXRF) Analysis of Total Metal(loid)s and Sequential Extraction of Bioavailable Arsenic in Agricultural Soils of Animas Watershed." Water, Air, & Soil Pollution 232, no. 7: 1-14.

Preprint content
Published: 28 April 2021
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Models of soil organic matter (SOM) decomposition are critical for predicting the fate of soil carbon (and nutrient) under changing climate. Traditionally, models have used a simple set-up where the substrate is divided into conceptual pools to represent their resistance to microbial degradation, and decomposition rates are often proportional to the amount of substrate in each pool. Emerging models now consider explicit microbial dynamics and show that SOM loss under warming may be fundamentally different from the classical models. Microbial explicit models use reaction kinetics, represented on a concentration basis. However, when the substrate makes up most of the volume of soils (e.g., the organic horizon in forest soils or peat), an increase or decrease in SOM does not, or only very little, affect concentrations of microbes and substrate. Consequently, reduction in SOM does not reduce the amount of substrate the microbial biomass encounters. This problem does not occur in classical models like CENTURY. We incorporated the effect of organic matter on soil volume in several microbial models. If microbes are solely limited by enzymes, organic soils or peats are decomposed very quickly as there is no mechanism that stops the positive feedback between microbial growth and SOM concentration until the substrate is gone. Alternative formulations that account for carbon limitation or microbial ‘cannibalism’ display a sweet spot of soil carbon concentration. Interestingly, a response to warming will depend on the amount of organic vs. mineral materials. Apparent Q10 was higher in fully organic soil than in mineral soils, which was pronounced when small to moderate amounts of the mineral matter was present that diluted the substrate for microbes. We suggest that model formulations need to be clear about the assumption in key processes, as each of the steps in the cascade of biogeochemical reaction can produce surprising results.

ACS Style

Debjani Sihi; Stefan Gerber. Challenges of using microbial explicit models for evaluating organic matter decomposition in predominantly organic soils . 2021, 1 .

AMA Style

Debjani Sihi, Stefan Gerber. Challenges of using microbial explicit models for evaluating organic matter decomposition in predominantly organic soils . . 2021; ():1.

Chicago/Turabian Style

Debjani Sihi; Stefan Gerber. 2021. "Challenges of using microbial explicit models for evaluating organic matter decomposition in predominantly organic soils ." , no. : 1.

Journal article
Published: 26 March 2021 in Journal of Geophysical Research: Biogeosciences
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Understanding seasonal and diurnal dynamics of ecosystem respiration (Reco) in forests is challenging, because Reco can only be measured directly during night‐time by eddy‐covariance flux towers. Reco is the sum of soil respiration (Rsoil) and above‐ground respiration (in theory, RAG = Reco ‐ Rsoil). Rsoil can be measured day and night and can provide a check of consistency on Reco, as the difference in magnitude and time dynamic between Reco and Rsoil should be explained by RAG. We assessed the temporal patterns and climatic drivers of Rsoil and Reco in a mature eucalypt woodland, using continuous measurements (only at night for Reco) at half‐hourly resolution over 4 years (2014‐2017). Our data showed large seasonal and diurnal (overnight) variation of Reco, while Rsoil had a low diurnal amplitude and their difference (Reco ‐ Rsoil, or RAG) had a low seasonal amplitude. This result implies at first glance that seasonal variation of Reco was mainly influenced by Rsoil while its diurnal variation was mainly influenced by RAG. However, our analysis suggests that the night‐time Reco decline cannot realistically be explained by a decline of RAG. Chamber measurements of autotrophic components at half‐hourly time resolution are needed to quantify how much of the Reco decline overnight is due to declines in leaf or stem respiration, and how much is due to missing storage or advection, which may create a systematic bias in Reco measurements. Our findings emphasize the need for reconciling bottom‐up (via components measured with chambers) and direct estimates of Reco (via eddy‐covariance method).

ACS Style

A. A. Renchon; J. E. Drake; C. A. Macdonald; D. Sihi; N. Hinko‐Najera; M. G. Tjoelker; S. K. Arndt; N. J. Noh; E. Davidson; E. Pendall. Concurrent Measurements of Soil and Ecosystem Respiration in a Mature Eucalypt Woodland: Advantages, Lessons, and Questions. Journal of Geophysical Research: Biogeosciences 2021, 126, 1 .

AMA Style

A. A. Renchon, J. E. Drake, C. A. Macdonald, D. Sihi, N. Hinko‐Najera, M. G. Tjoelker, S. K. Arndt, N. J. Noh, E. Davidson, E. Pendall. Concurrent Measurements of Soil and Ecosystem Respiration in a Mature Eucalypt Woodland: Advantages, Lessons, and Questions. Journal of Geophysical Research: Biogeosciences. 2021; 126 (3):1.

Chicago/Turabian Style

A. A. Renchon; J. E. Drake; C. A. Macdonald; D. Sihi; N. Hinko‐Najera; M. G. Tjoelker; S. K. Arndt; N. J. Noh; E. Davidson; E. Pendall. 2021. "Concurrent Measurements of Soil and Ecosystem Respiration in a Mature Eucalypt Woodland: Advantages, Lessons, and Questions." Journal of Geophysical Research: Biogeosciences 126, no. 3: 1.

Journal article
Published: 15 March 2021 in Biogeosciences
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Tropical ecosystems contribute significantly to global emissions of methane (CH4), and landscape topography influences the rate of CH4 emissions from wet tropical forest soils. However, extreme events such as drought can alter normal topographic patterns of emissions. Here we explain the dynamics of CH4 emissions during normal and drought conditions across a catena in the Luquillo Experimental Forest, Puerto Rico. Valley soils served as the major source of CH4 emissions in a normal precipitation year (2016), but drought recovery in 2015 resulted in dramatic pulses in CH4 emissions from all topographic positions. Geochemical parameters including (i) dissolved organic carbon (C), acetate, and soil pH and (ii) hydrological parameters like soil moisture and oxygen (O2) concentrations varied across the catena. During the drought, soil moisture decreased in the slope and ridge, and O2 concentrations increased in the valley. We simulated the dynamics of CH4 emissions with the Microbial Model for Methane Dynamics-Dual Arrhenius and Michaelis–Menten (M3D-DAMM), which couples a microbial functional group CH4 model with a diffusivity module for solute and gas transport within soil microsites. Contrasting patterns of soil moisture, O2, acetate, and associated changes in soil pH with topography regulated simulated CH4 emissions, but emissions were also altered by rate-limited diffusion in soil microsites. Changes in simulated available substrate for CH4 production (acetate, CO2, and H2) and oxidation (O2 and CH4) increased the predicted biomass of methanotrophs during the drought event and methanogens during drought recovery, which in turn affected net emissions of CH4. A variance-based sensitivity analysis suggested that parameters related to aceticlastic methanogenesis and methanotrophy were most critical to simulate net CH4 emissions. This study enhanced the predictive capability for CH4 emissions associated with complex topography and drought in wet tropical forest soils.

ACS Style

Debjani Sihi; Xiaofeng Xu; Mónica Salazar Ortiz; Christine S. O'Connell; Whendee L. Silver; Carla López-Lloreda; Julia M. Brenner; Ryan K. Quinn; Jana R. Phillips; Brent D. Newman; Melanie A. Mayes. Representing methane emissions from wet tropical forest soils using microbial functional groups constrained by soil diffusivity. Biogeosciences 2021, 18, 1769 -1786.

AMA Style

Debjani Sihi, Xiaofeng Xu, Mónica Salazar Ortiz, Christine S. O'Connell, Whendee L. Silver, Carla López-Lloreda, Julia M. Brenner, Ryan K. Quinn, Jana R. Phillips, Brent D. Newman, Melanie A. Mayes. Representing methane emissions from wet tropical forest soils using microbial functional groups constrained by soil diffusivity. Biogeosciences. 2021; 18 (5):1769-1786.

Chicago/Turabian Style

Debjani Sihi; Xiaofeng Xu; Mónica Salazar Ortiz; Christine S. O'Connell; Whendee L. Silver; Carla López-Lloreda; Julia M. Brenner; Ryan K. Quinn; Jana R. Phillips; Brent D. Newman; Melanie A. Mayes. 2021. "Representing methane emissions from wet tropical forest soils using microbial functional groups constrained by soil diffusivity." Biogeosciences 18, no. 5: 1769-1786.

Research letter
Published: 01 January 2021 in Agricultural & Environmental Letters
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In this study, an inexpensive Nix Pro (Nix Sensor Ltd.) color sensor was used to develop prediction models for soil iron (Fe) content. Thirty-eight soil samples were collected from five agricultural fields across the Animas watershed to develop and validate soil Fe prediction models. We used color space models to develop three different parameter sets for Fe prediction with Nix Pro. The different color space sets were used to develop three new predictive models for Nix Pro-based Fe content against the lab-based inductively coupled plasma analyzed Fe content. The model performances were assessed using the coefficient of determination, root mean square error, and model p-value. Three models (International Commission on Illumination's lightness, ±a axis (redness to greenness), and ± b axis (yellowness to blueness) [CIEL*a*b]; red, green, blue [RGB]; and cyan, magenta, yellow, key [black] [CMYK]) were significant in predicting the Fe content using colorimetric variables with R2 ranging from 0.79 to 0.81. The mean square prediction error (MSPE) and Kling–Gupta efficiency (KGE) Index were calculated to validate models and CMYK was predicted to be a better model (MSPE = 0.13; KGE = 0.601) than CIEL*a*b and RGB models. The results suggest Nix Pro is useful in predicting soil Fe content.

ACS Style

Gaurav Jha; Debjani Sihi; Biswanath Dari; Harpreet Kaur; Mallika Arudi Nocco; April Ulery; Kevin Lombard. Rapid and inexpensive assessment of soil total iron using Nix Pro color sensor. Agricultural & Environmental Letters 2021, 6, e20050 .

AMA Style

Gaurav Jha, Debjani Sihi, Biswanath Dari, Harpreet Kaur, Mallika Arudi Nocco, April Ulery, Kevin Lombard. Rapid and inexpensive assessment of soil total iron using Nix Pro color sensor. Agricultural & Environmental Letters. 2021; 6 (3):e20050.

Chicago/Turabian Style

Gaurav Jha; Debjani Sihi; Biswanath Dari; Harpreet Kaur; Mallika Arudi Nocco; April Ulery; Kevin Lombard. 2021. "Rapid and inexpensive assessment of soil total iron using Nix Pro color sensor." Agricultural & Environmental Letters 6, no. 3: e20050.

Journal article
Published: 05 August 2020 in Eos
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Scientists leverage long-term environmental measurements, emerging satellite observations, and recent modeling advances to examine changes in ecosystem carbon and water cycling.

ACS Style

Linnia R. Hawkins; Jitendra Kumar; Xiangzhong Luo; Debjani Sihi; Sha Zhou. Measuring, Monitoring, and Modeling Ecosystem Cycling. Eos 2020, 101, 1 .

AMA Style

Linnia R. Hawkins, Jitendra Kumar, Xiangzhong Luo, Debjani Sihi, Sha Zhou. Measuring, Monitoring, and Modeling Ecosystem Cycling. Eos. 2020; 101 ():1.

Chicago/Turabian Style

Linnia R. Hawkins; Jitendra Kumar; Xiangzhong Luo; Debjani Sihi; Sha Zhou. 2020. "Measuring, Monitoring, and Modeling Ecosystem Cycling." Eos 101, no. : 1.

Research article
Published: 13 May 2020 in PLOS ONE
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Optimizing barley (hordeum vulgare L.) production in Idaho and other parts of the Pacific Northwest (PNW) should focus on farm resource management. The effect of post-harvest residue management on barley residue decomposition has not been adequately studied. Thus, the objective of this study was to determine the effect of residue placement (surface vs. incorporated), residue size (chopped vs. ground-sieved) and soil type (sand and sandy loam) on barley residue decomposition. A 50-day(d) laboratory incubation experiment was conducted at a temperature of 25°C at the Aberdeen Research and Extension Center, Aberdeen, Idaho, USA. Following the study, a Markov-Chain Monte Carlo (MCMC) modeling approach was applied to investigate the first-order decay kinetics of barley residue. An accelerated initial flush of residue carbon(C)-mineralization was measured for the sieved (Day 1) compared to chopped (Day 3 to 5) residues for both surface incorporated applications. The highest evolution of carbon dioxide (CO2)-C of 8.3 g kg-1 dry residue was observed on Day 1 from the incorporated-sieved application for both soils. The highest and lowest amount of cumulative CO2-C released and percentage residue decomposed over 50-d was observed for surface-chopped (107 g kg-1 dry residue and 27%, respectively) and incorporated-sieved (69 g kg-1 dry residue and 18%, respectively) residues, respectively. There were no significant differences in C-mineralization from barley residue based on soil type or its interactions with residue placement and size (p >0.05). The largest decay constant k of 0.0083 d-1 was calculated for surface-chopped residue where the predicted half-life was 80 d, which did not differ from surface sieved or incorporated chopped. In contrast, incorporated-sieved treatments only resulted in a k of 0.0054 d-1 and would need an additional 48 d to decompose 50% of the residue. Future residue decomposition studies under field conditions are warranted to verify the residue C-mineralization and its impact on residue management.

ACS Style

Grant Loomis; Biswanath Dari; Christopher W. Rogers; Debjani Sihi. Evaluation of residue management practices on barley residue decomposition. PLOS ONE 2020, 15, e0232896 .

AMA Style

Grant Loomis, Biswanath Dari, Christopher W. Rogers, Debjani Sihi. Evaluation of residue management practices on barley residue decomposition. PLOS ONE. 2020; 15 (5):e0232896.

Chicago/Turabian Style

Grant Loomis; Biswanath Dari; Christopher W. Rogers; Debjani Sihi. 2020. "Evaluation of residue management practices on barley residue decomposition." PLOS ONE 15, no. 5: e0232896.

Communication
Published: 28 March 2020 in Water
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Water contamination is often reported in agriculturally intensive areas such as the Indo-Gangetic Plain (IGP) in south-eastern Asia. We evaluated the impact of the organic and conventional farming of basmati rice on water quality during the rainy season (July to October) of 2011 and 2016 at Kaithal, Haryana, India. The study area comprised seven organic and seven conventional fields where organic farming has been practiced for more than two decades. Water quality parameters used for drinking (nitrate, NO3; total dissolved solids (TDS); electrical conductivity (EC) pH) and irrigation (sodium adsorption ratio (SAR) and residual sodium carbonate (RSC)) purposes were below permissible limits for all samples collected from organic fields and those from conventional fields over the long-term (~15 and ~20 years). Importantly, the magnitude of water NO3 contamination in conventional fields was approximately double that of organic fields, which is quite alarming and needs attention in future for farming practices in the IGP in south-eastern Asia.

ACS Style

Debjani Sihi; Biswanath Dari; Zhengjuan Yan; Dinesh Kumar Sharma; Himanshu Pathak; Om Prakash Sharma; Lata Nain. Assessment of Water Quality in Indo-Gangetic Plain of South-Eastern Asia under Organic vs. Conventional Rice Farming. Water 2020, 12, 960 .

AMA Style

Debjani Sihi, Biswanath Dari, Zhengjuan Yan, Dinesh Kumar Sharma, Himanshu Pathak, Om Prakash Sharma, Lata Nain. Assessment of Water Quality in Indo-Gangetic Plain of South-Eastern Asia under Organic vs. Conventional Rice Farming. Water. 2020; 12 (4):960.

Chicago/Turabian Style

Debjani Sihi; Biswanath Dari; Zhengjuan Yan; Dinesh Kumar Sharma; Himanshu Pathak; Om Prakash Sharma; Lata Nain. 2020. "Assessment of Water Quality in Indo-Gangetic Plain of South-Eastern Asia under Organic vs. Conventional Rice Farming." Water 12, no. 4: 960.

Chapter
Published: 14 January 2020 in World Soils Book Series
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Depending upon type and pedogenic stage, soils are subject to biotic and abiotic interactions of complex nature depending on type, nature and specific properties. Soil biogeochemistry involves the study of elemental cycling as mediated by complex and inseparable interactions between the biotic (living) and abiotic (non-living) components of soils. Human activities have substantially altered biogeochemical cycling of several key elements including carbon, nitrogen, phosphorus, potassium, and other secondary and minor nutrients over the past few decades, which, in turn, had serious environmental consequences. The present chapter outlines the soil biogeochemical investigations conducted within Indian subcontinent in both natural ecosystems and managed agricultural systems and addresses the state-of-the-art in order to understand the undergoing biogeochemical reactions. Here, we sought to clarify complex interactions generally occurred during biogeochemical transformations of an element (or compound) of interest within the type-specific soil. Further, we emphasized the importance of advancing our understanding of feedback loops in soil biogeochemical processes as altered by anthropogenic perturbations in tropical and sub-tropical soils of India. Overall, this chapter is broadly focused on the nutrient cycling, which is followed by more specific topics like “soil microbiology,” “soil biodiversity,” and “soil biotechnology.”

ACS Style

Debjani Sihi; Biswanath Dari. Soil Biogeochemistry. World Soils Book Series 2020, 143 -158.

AMA Style

Debjani Sihi, Biswanath Dari. Soil Biogeochemistry. World Soils Book Series. 2020; ():143-158.

Chicago/Turabian Style

Debjani Sihi; Biswanath Dari. 2020. "Soil Biogeochemistry." World Soils Book Series , no. : 143-158.

Hypothesis and theory article
Published: 10 October 2019 in Frontiers in Ecology and Evolution
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Soil organic matter (SOM) is central to soil carbon (C) storage and terrestrial nutrient cycling. New data have upended the traditional model of stabilization, which held that stable SOM was mostly made of undecomposed plant molecules. We now know that microbial by-products and dead cells comprise unexpectedly large amounts of stable SOM because they can become attached to mineral surfaces or physically protected within soil aggregates. SOM models have been built to incorporate the microbial to mineral stabilization of organic matter, but now face a new challenge of accurately capturing microbial productivity and metabolism. Explicitly representing stoichiometry, the relative nutrient requirements for growth and maintenance of organisms, could provide a way forward. Stoichiometry limits SOM formation and turnover in nature, but important nutrients like nitrogen (N), phosphorus (P), and sulfur (S) are often missing from the new generation of SOM models. In this synthesis, we seek to facilitate the addition of these nutrients to SOM models by (1) reviewing the stoichiometric bias—the tendency to favor one element over another—of four key processes in the new framework of SOM cycling and (2) applying this knowledge to build a stoichiometrically explicit budget of C, N, P, and S flow through the major SOM pools. By quantifying the role of stoichiometry in SOM cycling, we discover that constraining the C:N:P:S ratio of microorganisms and SOM to specific values reduces uncertainty in C and nutrient flow as effectively as using microbial C use efficiency (CUE) parameters. We find that the value of additional constraints on stoichiometry vs. CUE varies across ecosystems, depending on how precise the available data are for that ecosystem and which biogeochemical pathways are present. Moreover, because CUE summarizes many different processes, stoichiometric measurements of key soil pools are likely to be more robust when extrapolated from soil incubations to plot or biome scale estimates. Our results suggest that measuring SOM stoichiometry should be a priority for future empirical work and that the inclusion of new nutrients in SOM models may be an effective way to improve precision.

ACS Style

Robert W. Buchkowski; Alanna Shaw; Debjani Sihi; Gabriel R. Smith; Ashley D. Keiser. Constraining Carbon and Nutrient Flows in Soil With Ecological Stoichiometry. Frontiers in Ecology and Evolution 2019, 7, 1 .

AMA Style

Robert W. Buchkowski, Alanna Shaw, Debjani Sihi, Gabriel R. Smith, Ashley D. Keiser. Constraining Carbon and Nutrient Flows in Soil With Ecological Stoichiometry. Frontiers in Ecology and Evolution. 2019; 7 ():1.

Chicago/Turabian Style

Robert W. Buchkowski; Alanna Shaw; Debjani Sihi; Gabriel R. Smith; Ashley D. Keiser. 2019. "Constraining Carbon and Nutrient Flows in Soil With Ecological Stoichiometry." Frontiers in Ecology and Evolution 7, no. : 1.

Invited primary research article
Published: 03 October 2019 in Global Change Biology
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Production and consumption of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) are affected by complex interactions of temperature, moisture, and substrate supply, which are further complicated by spatial heterogeneity of the soil matrix. This microsite heterogeneity is often invoked to explain non‐normal distributions of greenhouse gas (GHG) fluxes, also known as hot spots and hot moments. To advance numerical simulation of these belowground processes, we expanded the Dual Arrhenius and Michaelis–Menten model, to apply it consistently for all three GHGs with respect to the biophysical processes of production, consumption, and diffusion within the soil, including the contrasting effects of oxygen (O2) as substrate or inhibitor for each process. High‐frequency chamber‐based measurements of all three GHGs at the Howland Forest (ME, USA) were used to parameterize the model using a multiple constraint approach. The area under a soil chamber is partitioned according to a bivariate log‐normal probability distribution function (PDF) of carbon and water content across a range of microsites, which leads to a PDF of heterotrophic respiration and O2 consumption among microsites. Linking microsite consumption of O2 with a diffusion model generates a broad range of microsite concentrations of O2, which then determines the PDF of microsites that produce or consume CH4 and N2O, such that a range of microsites occurs with both positive and negative signs for net CH4 and N2O flux. Results demonstrate that it is numerically feasible for microsites of N2O reduction and CH4 oxidation to co‐occur under a single chamber, thus explaining occasional measurement of simultaneous uptake of both gases. Simultaneous simulation of all three GHGs in a parsimonious modeling framework is challenging, but it increases confidence that agreement between simulations and measurements is based on skillful numerical representation of processes across a heterogeneous environment.

ACS Style

Debjani Sihi; Eric A. Davidson; Kathleen E. Savage; Dong Liang. Simultaneous numerical representation of soil microsite production and consumption of carbon dioxide, methane, and nitrous oxide using probability distribution functions. Global Change Biology 2019, 26, 200 -218.

AMA Style

Debjani Sihi, Eric A. Davidson, Kathleen E. Savage, Dong Liang. Simultaneous numerical representation of soil microsite production and consumption of carbon dioxide, methane, and nitrous oxide using probability distribution functions. Global Change Biology. 2019; 26 (1):200-218.

Chicago/Turabian Style

Debjani Sihi; Eric A. Davidson; Kathleen E. Savage; Dong Liang. 2019. "Simultaneous numerical representation of soil microsite production and consumption of carbon dioxide, methane, and nitrous oxide using probability distribution functions." Global Change Biology 26, no. 1: 200-218.

Commentary
Published: 08 May 2019 in Journal of Geophysical Research: Biogeosciences
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Soil organic matter (SOM) is a critical ecosystem variable regulated by interacting physical, chemical and biological processes. Collaborative efforts to integrate perspectives, data, and models from interdisciplinary research and observation networks can significantly advance predictive understanding of SOM. We outline how integrating three networks – the Long‐Term Ecological Research, with a focus on ecological dynamics, the Critical Zone Observatories with strengths in landscape/geologic context, and the National Ecological Observatory Network with standardized multi‐scale measurements—can advance SOM knowledge. This integration requires improved data dissemination and sharing, coordinated data collection activities, and enhanced collaboration between empiricists and modelers within and across networks.

ACS Style

Samantha R. Weintraub; Alejandro N. Flores; William R. Wieder; Debjani Sihi; Claudia Cagnarini; Daniel Ruiz Potma Gonçalves; Michael H. Young; Li Li; Yaniv Olshansky; Roland Baatz; Pamela L. Sullivan; Peter M. Groffman. Leveraging Environmental Research and Observation Networks to Advance Soil Carbon Science. Journal of Geophysical Research: Biogeosciences 2019, 124, 1047 -1055.

AMA Style

Samantha R. Weintraub, Alejandro N. Flores, William R. Wieder, Debjani Sihi, Claudia Cagnarini, Daniel Ruiz Potma Gonçalves, Michael H. Young, Li Li, Yaniv Olshansky, Roland Baatz, Pamela L. Sullivan, Peter M. Groffman. Leveraging Environmental Research and Observation Networks to Advance Soil Carbon Science. Journal of Geophysical Research: Biogeosciences. 2019; 124 (5):1047-1055.

Chicago/Turabian Style

Samantha R. Weintraub; Alejandro N. Flores; William R. Wieder; Debjani Sihi; Claudia Cagnarini; Daniel Ruiz Potma Gonçalves; Michael H. Young; Li Li; Yaniv Olshansky; Roland Baatz; Pamela L. Sullivan; Peter M. Groffman. 2019. "Leveraging Environmental Research and Observation Networks to Advance Soil Carbon Science." Journal of Geophysical Research: Biogeosciences 124, no. 5: 1047-1055.

Journal article
Published: 28 December 2018 in Eos
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Root Trait and Soil Carbon Workshop; Oak Ridge National Laboratory, Oak Ridge, Tennessee, 31 July to 1 August 2018

ACS Style

Avni Malhotra; Debjani Sihi; Colleen M. Iversen. The Fate of Root Carbon in Soil: Data and Model Gaps. Eos 2018, 99, 1 .

AMA Style

Avni Malhotra, Debjani Sihi, Colleen M. Iversen. The Fate of Root Carbon in Soil: Data and Model Gaps. Eos. 2018; 99 ():1.

Chicago/Turabian Style

Avni Malhotra; Debjani Sihi; Colleen M. Iversen. 2018. "The Fate of Root Carbon in Soil: Data and Model Gaps." Eos 99, no. : 1.

Chapter
Published: 03 November 2018 in Advances in Crop Environment Interaction
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Rice (Oryza sativa L.) is the second largest cereal crop produced globally, with a worldwide production of about 720 million metric tons in recent years and contributing toward for 20% of the global calorie intake. The growing condition of rice is extreme such as high vs. low temperature and high vs. low level of CO2 concentration [CO2]. Given CO2 is a key substrate for photosynthesis, the atmospheric concentration of CO2 dominantly influences the growth and yield of rice crop. The main component of rice is the kernel (~90%) which is starch, and the composition and behavior of starch are greatly impacted by environmental drivers including temperature, CO2, and water. Therefore, it is important to understand the variation in production and yield of rice under the elevated [CO2]. Here, we discussed the impacts of elevated [CO2] on the quality and quantity of rice production under current and future climatic conditions. We have discussed the response of rice crops under elevated [CO2] and its interaction with several other biophysical drivers including air temperature, ozone concentration, soil water content, and genotype in various experimental approaches, viz., free-air CO2 enrichment (FACE), open top chambers (OTC), growth chambers, and temperature gradient tunnels. Overall, elevated [CO2] stimulated photosynthesis and production of rice on a short-term, but the long-term effects of elevated [CO2] on the quality and quantity of rice production is yet to be resolved and need some attention with respect to various environmental constraints.

ACS Style

Biswanath Dari; Debjani Sihi. Future of Rice Crop Under Enriched CO2 Environment. Advances in Crop Environment Interaction 2018, 425 -437.

AMA Style

Biswanath Dari, Debjani Sihi. Future of Rice Crop Under Enriched CO2 Environment. Advances in Crop Environment Interaction. 2018; ():425-437.

Chicago/Turabian Style

Biswanath Dari; Debjani Sihi. 2018. "Future of Rice Crop Under Enriched CO2 Environment." Advances in Crop Environment Interaction , no. : 425-437.

Journal article
Published: 25 August 2018 in Geoderma
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Recent developments of enzyme-based decomposition models highlight the importance of enzyme kinetics with warming, but most modeling exercises are based on studies with a step-wise warming. This approach may mask the effect of temperature in controlling in-situ activities as in most ecosystems the rate of warming is more gradual than these step warming studies. We conducted an experiment to test the effects of contrasting warming rates on the kinetics of carbon (C), nitrogen (N), and phosphorus (P) degradation enzymes in subtropical peat soils. We also wanted to evaluate if the stoichiometry of enzyme kinetics shifts under contrasting warming rates and if so, how does it relate to the stoichiometry in microbial biomass. Contrasting warming rates altered microbial biomass stoichiometry leading to differing patterns of microbial demand for C vs. nutrient (N and P) and enzyme expression following the optimum foraging strategy. Activity (higher Vmax) and efficiency (lower Km) of C acquisition enzymes were greater in the step treatment; however, expressions of nutrient (N and P) acquiring enzymes were enhanced in the ramp treatment at the end of the experiment. In the step treatment, there was a typical pattern of an initial peak in the Vmax and drop in the Km for all enzyme groups followed by later adjustments. On the other hand, a consistent increase in Vmax and decline in Km of all enzyme groups were observed in the ramp treatment. These changes were sufficient to alter microbial identity (as indicated by enzyme Km and biomass stoichiometry) with two apparently different endpoints under contrasting warming rates. This observation resembles the concept of alternate stable states and highlights a need for improved representation of warming effects on enzymes in decomposition models. Using peat soils of Florida Everglades, here we have demonstrated that contrasting warming rates can influence the dynamics of microbial and enzymatic kinetics. Hence, we suggest that future laboratory and field warming studies could consider our approach to accurately represent microbial and enzymatic kinetics in biogeochemical models.

ACS Style

Debjani Sihi; Patrick W. Inglett; Kanika S. Inglett. Warming rate drives microbial nutrient demand and enzyme expression during peat decomposition. Geoderma 2018, 336, 12 -21.

AMA Style

Debjani Sihi, Patrick W. Inglett, Kanika S. Inglett. Warming rate drives microbial nutrient demand and enzyme expression during peat decomposition. Geoderma. 2018; 336 ():12-21.

Chicago/Turabian Style

Debjani Sihi; Patrick W. Inglett; Kanika S. Inglett. 2018. "Warming rate drives microbial nutrient demand and enzyme expression during peat decomposition." Geoderma 336, no. : 12-21.

Journal article
Published: 01 July 2018 in Geoderma
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ACS Style

Zhengjuan Yan; Shuo Chen; Biswanath Dari; Debjani Sihi; Qing Chen. Phosphorus transformation response to soil properties changes induced by manure application in a calcareous soil. Geoderma 2018, 322, 163 -171.

AMA Style

Zhengjuan Yan, Shuo Chen, Biswanath Dari, Debjani Sihi, Qing Chen. Phosphorus transformation response to soil properties changes induced by manure application in a calcareous soil. Geoderma. 2018; 322 ():163-171.

Chicago/Turabian Style

Zhengjuan Yan; Shuo Chen; Biswanath Dari; Debjani Sihi; Qing Chen. 2018. "Phosphorus transformation response to soil properties changes induced by manure application in a calcareous soil." Geoderma 322, no. : 163-171.

Journal article
Published: 01 April 2018 in Agricultural and Forest Meteorology
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Debjani Sihi; Eric A. Davidson; Min Chen; Kathleen E. Savage; Andrew D. Richardson; Trevor Keenan; David Y. Hollinger. Merging a mechanistic enzymatic model of soil heterotrophic respiration into an ecosystem model in two AmeriFlux sites of northeastern USA. Agricultural and Forest Meteorology 2018, 252, 155 -166.

AMA Style

Debjani Sihi, Eric A. Davidson, Min Chen, Kathleen E. Savage, Andrew D. Richardson, Trevor Keenan, David Y. Hollinger. Merging a mechanistic enzymatic model of soil heterotrophic respiration into an ecosystem model in two AmeriFlux sites of northeastern USA. Agricultural and Forest Meteorology. 2018; 252 ():155-166.

Chicago/Turabian Style

Debjani Sihi; Eric A. Davidson; Min Chen; Kathleen E. Savage; Andrew D. Richardson; Trevor Keenan; David Y. Hollinger. 2018. "Merging a mechanistic enzymatic model of soil heterotrophic respiration into an ecosystem model in two AmeriFlux sites of northeastern USA." Agricultural and Forest Meteorology 252, no. : 155-166.

Journal article
Published: 01 September 2017 in Global Change Biology
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Temperature sensitivity of anaerobic carbon mineralization in wetlands remains poorly represented in most climate models and is especially unconstrained for warmer subtropical and tropical systems which account for a large proportion of global methane emissions. Several studies of experimental warming have documented thermal acclimation of soil respiration involving adjustments in microbial physiology or carbon use efficiency (CUE), with an initial decline in CUE with warming followed by a partial recovery in CUE at a later stage. The variable CUE implies that the rate of warming may impact microbial acclimation and the rate of carbon-dioxide (CO2) and methane (CH4) production. Here, we assessed the effects of warming rate on the decomposition of subtropical peats, by applying either a large single-step (10°C within a day) or a slow ramping (0.1°C/day for 100 days) temperature increase. The extent of thermal acclimation was tested by monitoring CO2 and CH4 production, CUE, and microbial biomass. Total gaseous C loss, CUE, and MBC were greater in the slow (ramp) warming treatment. However, greater values of CH4–C:CO2–C ratios lead to a greater global warming potential in the fast (step) warming treatment. The effect of gradual warming on decomposition was more pronounced in recalcitrant and nutrient-limited soils. Stable carbon isotopes of CH4 and CO2 further indicated the possibility of different carbon processing pathways under the contrasting warming rates. Different responses in fast vs. slow warming treatment combined with different endpoints may indicate alternate pathways with long-term consequences. Incorporations of experimental results into organic matter decomposition models suggest that parameter uncertainties in CUE and CH4–C:CO2–C ratios have a larger impact on long-term soil organic carbon and global warming potential than uncertainty in model structure, and shows that particular rates of warming are central to understand the response of wetland soils to global climate change.

ACS Style

Debjani Sihi; Patrick W. Inglett; Stefan Gerber; Kanika S. Inglett. Rate of warming affects temperature sensitivity of anaerobic peat decomposition and greenhouse gas production. Global Change Biology 2017, 24, e259 -e274.

AMA Style

Debjani Sihi, Patrick W. Inglett, Stefan Gerber, Kanika S. Inglett. Rate of warming affects temperature sensitivity of anaerobic peat decomposition and greenhouse gas production. Global Change Biology. 2017; 24 (1):e259-e274.

Chicago/Turabian Style

Debjani Sihi; Patrick W. Inglett; Stefan Gerber; Kanika S. Inglett. 2017. "Rate of warming affects temperature sensitivity of anaerobic peat decomposition and greenhouse gas production." Global Change Biology 24, no. 1: e259-e274.