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Typical soil health assessment requires intensive field sampling and laboratory analysis. Although this approach yields accurate results, it can be costly and labor intensive and not suitable for continuous tracking of soil properties. Advances in soil sensor and wireless technologies are poised to replace physical sampling and offline measurement with in-field monitoring. This article reports the development, deployment, and validation of an Internet-of-Things (IoT) system for continuous monitoring of soil health. The end nodes of the proposed system, called soil health monitoring units (SHMUs), are solar powered and can be installed on a field for extended periods of time. Each SHMU transmits soil temperature, moisture, electrical conductivity, carbon dioxide (CO2), and geolocation data wirelessly using long-range wide-area network (LoRaWAN) radio technology. Data are received by a LoRaWAN gateway, which uploads it to a server for long-term storage and analysis. Users can view acquired data through a Web-based dashboard. The following significant experiments were carried out to validate the developed system: 1) a network consisting of eight SHMUs was deployed at an agricultural field site for several weeks and soil health metrics were analyzed using the soil health dashboard; 2) the flexibility of the system was demonstrated by the addition of an extra CO2 sensor allowing an additional variable directly linked to soil health to be recorded; 3) a wireless communication range of 3422 m was estimated at a transmission power of 10 dBm by deploying the developed system on a large field; 4) the average current consumption of a SHMU (including its associated sensors) was estimated to be 13 mA, at this rate, the onboard Li-ion battery is able to sustain a SHMU for several days; and 5) a 7 cm $\times6.5$ cm solar panel was able to fully charge the onboard battery in 14 days while supplying power to the SHMU.

High altitude alpine grasslands in the Qinghai-Tibetan Plateau (QTP) contain high soil organic C (SOC) stocks that are extremely vulnerable to climate warming. Microbial residues are increasingly recognized as a major source of SOC, however, how climate warming affects this component of SOC in this region remains largely unknown. In this study, we examined the response of microbial residues to a 3-year experimental warming and the degree to which they contributed to SOC storage in two Tibetan ecosystems—alpine steppe (AS) and swamp meadow (SM). The number of microbial residues was indicated by amino sugar analysis. Our results revealed that warming yielded divergent microbial residue accumulation that significantly altered their contribution to SOC storage in the two alpine grasslands. Warming increased microbial residue abundance by approximately 17.6% across 0 to 20 cm depth in SM soils, while causing a significant decline (about 6.2%) in AS soils. The higher microbial residue accumulation in SM could lessen potential positive feedbacks from climate warming, while the decrease in microbial residues in AS may indicate greater loss of microbial-derived C inputs in warmed soils. Moreover, we found that warming selectively increased fungal residues as compared with bacterial despite inconsistent responses to warming in the two grasslands. These changes were accompanied by significant shifts in fungal to bacterial residue C ratios and their contribution to SOC pool, indicating an alteration of SOC composition and stability in alpine grassland ecosystems. These findings demonstrate that a microbial-derived C feedback to climate change is ecosystem-specific that alters the direction and magnitude of the microbial community.

Often, metal and metalloid ions are present in water at concentrations that seriously affect human health; understanding their occurrence is critical, especially in regions such as Peru, where natural volcanic activity and anthropogenic activity have made them more prevalent in local waterbodies. In this study, river, lake, aquifer, and irrigation water samples, collected from the Chili-Quilca, Camana-Majes, Colca-Chivay-Siguas, Ocona, Urubamba-Vilcanota, and Titicaca river basins in Southern Peru, were analyzed for transition metals, other metals, metalloids, and other inorganic water constituents. Special emphasis was placed on metals and metalloids regulated by Peruvian Water Quality Standards and those categorized as of “primary interest” by the U.S. EPA, herein collectively referred to as “elements of concern”. Of the elements of concern, boron (2,170 µg L−1) and arsenic (2,060 µg L−1), were found at the highest concentrations in river water in the southern basins. Phosphorus (2,000 µg L−1) and boron (2,056 µg L−1) were found at the highest concentrations in irrigation water. The most frequently found elements of concern (in more than 60% of the samples) in all types of surface water samples were Al, As, B, Ba, Cu, Li, Mn, Sr, P, V and Zn. The most polluted waters, based on regulated metals concentrations and on their HQing quotient, followed the order: groundwater > river water > lake water. The potential sources of transition metal contamination were deduced by applying the multivariant statistical technique, principal component analysis (PCA), to the extensive sample dataset that included 35 variables and a total of 7,686 data of metal, metalloids, and other constituent concentrations, as well as physicochemical parameters. A Spanish translation of this paper is available in the online Supplementary Material.

We evaluated how microbial residues and their contributions to soil carbon (C) stocks changed with long-term (50 years) conversion of native grassland to cropland in the profiles (0–15, 15–30, 30–60, 60–90 cm) of chernozem. The conversion of grassland into arable land led to substantial depletion of microbial residues down to 90-cm depth, indicating the potential vulnerability of the microbial-derived C due to land-use change. Moreover, losses of microbial residue C at depths below 30 cm were much higher than that of total soil C after several decades’ cultivation. This demonstrated that the decline of total soil C pool after grassland conversion was selectively removing microbial residue C. Lower ratio of fungal to bacterial residue C after grassland conversion suggested a shift in the composition of microbial residue C, with potential consequences for changes in soil C quality and stock associated with land cultivation. Collectively, our findings foster the importance of microbial-derived organic C for soil C stock maintenance and emphasize the necessity to take subsurface soils into account when evaluating the role of microbial-derived C to soil C losses under land-use change.

A previous 5-year long field litter manipulation study at the Smithsonian Environmental Research Center (SERC) in coastal Maryland demonstrated that forest age controls the chemical trajectory of litter decay and the extent and source of litter incorporation into soil physical fractions among young (60–74 yrs) and old (113–132 yrs) successional stands. To investigate if these ecosystem-level differences influence soil organic carbon (SOC) stability and temperature sensitivity, and to infer differences in stabilization mechanisms, a six-month laboratory incubation (15 °C and 25 °C) of soils from the experimental plots was conducted. The results showed that: 1) C mineralization of wood amended soils was lower than control soils in all forests with young and old forests exhibiting distinct, early vs. late, CO2 efflux profiles over the time course of the incubation; 2) Soils from leaf-amended old forests exhibited a proportional increase in their active SOC pool but with shorter mean residence times (MRT) and a decrease in slow pools with longer MRTs, while SOC of young forests proportionally shifted to more slow cycling SOC pools with MRTs that were unchanged from controls. Structural equation modeling combining previous field and soil property data with laboratory incubation results indicated that temperature sensitivity of the active SOC pool was related to the microbial community and lignin content, while temperature sensitivity of the slow pool was related to chemical protection from silts and clays, environmental factors like pH, and soil C/N ratio. Our results underscore how successional forests of differing age can exhibit dramatically different controls on SOC-litter dynamics, through the protection and accessibility of C, that must be taken into account when predicting forest ecosystem response to future climate change.

Beneficial microbial associations enhance the fitness of most living organisms, and wood-feeding insects offer some of the most striking examples of this. Odontotaenius disjunctus is a wood-feeding beetle that possesses a digestive tract with four main compartments, each of which contains well-differentiated microbial populations, suggesting that anatomical properties and separation of these compartments may enhance energy extraction from woody biomass. Here, using integrated chemical analyses, we demonstrate that lignocellulose deconstruction and fermentation occur sequentially across compartments, and that selection for microbial groups and their metabolic pathways is facilitated by gut anatomical features. Metaproteogenomics showed that higher oxygen concentration in the midgut drives lignocellulose depolymerization, while a thicker gut wall in the anterior hindgut reduces oxygen diffusion and favours hydrogen accumulation, facilitating fermentation, homoacetogenesis and nitrogen fixation. We demonstrate that depolymerization continues in the posterior hindgut, and that the beetle excretes an energy- and nutrient-rich product on which its offspring subsist and develop. Our results show that the establishment of beneficial microbial partners within a host requires both the acquisition of the microorganisms and the formation of specific habitats within the host to promote key microbial metabolic functions. Together, gut anatomical properties and microbial functional assembly enable lignocellulose deconstruction and colony subsistence on an extremely nutrient-poor diet.

A potentially important factor for destabilization of soil organic C (SOC) in the conversion of ecosystems to arable land is the impact to microbial residues, which have been recently shown to be a significant source of SOC pool. Here, we present the results of a study investigating the changes of microbial residues along a chronosequence of cultivation (5, 15, and 25 years) and attempted restoration (6 and 12 years of agricultural abandonment) in a marsh wetland of China. The wetland cultivation depleted the fraction of SOC derived from microbes, in particular fungal residues. During agricultural abandonment and restoration, bacterial residues accumulated relatively more rapidly than fungal analogs, where fungal residues represented the major microbial SOC pool overall. These differential responses of microbial residues are illustrative of the susceptibility of this SOC pool and indicate their importance as a tool to track soil stability with land-use change. Our work points to the need for future research to focus more strongly on the nature and mechanisms of microbial residue–mediated C process during chronic land-use changes.

Author(s): Yan, Qina; Le, Phong VV; Woo, Dong K; Hou, Tingyu; Filley, Timothy; Kumar, Praveen

In most agricultural systems, the raindrop-induced breakdown of soil aggregates is the initial process of surface soil erosion and redistribution of soil organic matter. The physicochemical differences between the liberated and mobilized material and the residual raindrop-stable soil aggregates can be a critical factor controlling landscape-level heterogeneity in soil biogeochemical reactivity. Using an artificial rainfall simulator with soils from southeastern Iowa, we investigated the role of management intensity on the chemical characteristics of soil particles liberated through raindrop-induced breakdown of both small aggregates (0.25–2 mm; SMAGG) and large aggregates (>2 mm; LGAGG). At all sites LGAGG exhibited lower stability to raindrop energy than SMAGG. Both soil aggregate size classes from a restored prairie and an agricultural site using reduced ridge tillage exhibited higher raindrop stability than conventionally tilled sites. In the restored prairie, the chemical composition (i.e. lignin, substituted fatty acids, SOC and TN, δ15N values) of raindrop-liberated particles was nearly indistinguishable from raindrop-stable aggregates. Among all tilled sites, with the exception of SOC in the conservation tillage site, the raindrop stable particles had relatively higher concentration of measured chemical components versus raindrop-liberated particles. Additionally, the liberated particles in all tilled sites contained higher concentration of oxidized lignin phenols, a lower proportion of cinnamyl to vanillyl lignin, and, as evidenced by the δ15N values, a trend toward a higher proportion of microbially-processed nitrogen, indicating more decomposed microbial processed organic matter. These results are important for understanding the biogeochemical impacts and resulting spatial heterogeneity of raindrop liberated and transported soil particles among landscapes with different management intensity and efforts toward soil conservation.

Expansion and intensification of managed landscapes for agriculture have resulted in severe unintended global impacts, including degradation of arable land and eutrophication of receiving water bodies. Modern agricultural practices rely on significant direct and indirect human energy inputs through farm machinery and chemical use, respectively, which have created imbalances between increased rates of biogeochemical processes related to production and background rates of natural processes. We articulate how these imbalances have cascaded through the deep inter-dependencies between carbon, soil, water, nutrient and ecological processes, resulting in a critical transition of the critical zone and creating emergent inter-dependencies and co-evolutionary trajectories. Understanding of these novel organizations and function of the critical zone is vital for developing sustainable agricultural practices and environmental stewardship.

Few studies have quantitatively assessed the interacting controls of taxa-specific properties and PyOM production temperature on native soil C (NSC) stabilization/de-stabilization dynamics (i.e. priming effects - PE) because of difficulty in distinctly assessing NSC reactivity apart from added PyOM-C. To quantify PyOM-induced PE, we incubated 13C-enriched jack pine (JP) or red maple (RM) wood and associated 13C-PyOM produced at 200 (PyOM200), 300 (PyOM300), 450 (PyOM450) and 600 (PyOM600) °C in soil from a northern temperate forest (Michigan, U.S.A.) for 10 months. We found that (1) net PE was negative with addition of both wood and PyOM from both taxa, with a 3–40% suppression in mineralization across treatments, (2) RM200, RM450, and RM600 exhibited initial positive PE in the first week of incubation, (3) PyOM300 of both taxa, the temperature associated with initial aromatization and carbohydrate conversion, induced the most negative PE and exhibited the largest increase in soil oxidative enzyme activity in JP300, (4) addition of sucrose to the incubations as labile C, offset negative PE in JP treatments but not in RM treatments and, (5) mean residence times of the fast cycling C pool of NSC were lower (1.4–1.6 d) for RM than for JP (2.9–8.3 d) additions. These results suggest that future changes in tree taxa dominance in fire prone systems could alter soil C stability though introduction of PyOM of distinct, taxa-specific, chemical properties that may be largely controlled by taxa specific temperature thresholds in thermochemical conversion of woody tissues to PyOM.

Management of crop production using plastic film mulching (PFM) has the potential to improve soil health by accelerating nutrient cycling and facilitating stable C pool production; however, a key aspect of this process—microbial immobilization of residue C—is poorly understood, especially under PFM when combined with different fertilization treatments. A 360-day in situ 13C-tracing technique was used to analyze the contribution and dynamics of microbial biomass C (MBC) to soil organic C (SOC). Following 27-year PFM and four fertilization treatments, 13C-labelled maize straw residue was applied to micro-plot topsoil in a cultivated maize (Zea mays L.) field. Over the course of the experiment, MBC content was significantly (P

Global climate change has been found to affect plant net primary production and thereby could modify the quantity and quality of aboveground litter, which may consequently affect soil organic carbon (SOC). Whether those changes have influenced the chemical components of SOC is still unclear, especially for the soil beneath the surface soil. This study examined the changes in biopolymers (lignin, substituted fatty acids, amino sugars) in 0–10 cm and 10–20 cm soil depth in a temperate forest after five years of aboveground litter addition or removal treatments. The results showed that although SOC and soil nitrogen contents were not influenced by litter manipulation, the lignin phenols and substituted fatty acids contents in SOC of 10–20 cm soil were significantly higher in litter addition treatment compared to litter removal treatment, suggesting a selective accumulation pathway for these plant biopolymers in the 10–20 cm soil under litter manipulation. Soil amino sugar content, however, was not influenced by litter manipulation, although microbial biomass carbon (MBC) and nitrogen in 0–10 cm soil were significantly higher in litter addition plots due to the significantly higher substrate availability (dissolved organic carbon) and nutrient availability (total dissolved nitrogen) than those in the control. Although higher MBC could increase decomposition of SOC, this effect did not counterbalance the effect of higher aboveground litter input in litter addition plots, but rather changed the composition of SOC toward compounds of a purportedly more stable composition. The effects of aboveground litter removal were not entirely in contrast to the effects of aboveground litter addition on SOC, hinting that belowground inputs could sustain the storage of SOC for at least five years under aboveground litter removal treatment. The changes in the chemical composition of SOC under litter manipulation for five years suggested the potential changes in SOC stability and pool size in the future, especially in the 10–20 cm soil, to which more attention should be paid in future litter manipulation studies.

14 C is the most widely utilized geochronometer to investigate geological, geochemical and geophysical problems over the past 5 decades. Establishment of precise sedimentation rates is crucial for the reconstruction of paleo-climate, -ecological and – environmental studies when extrapolation of sedimentation rates is utilized for time scales beyond the dating range. However, agreement between short-term and long-term sedimentation rates in anthropogenically unperturbed sediment cores has not been shown. Here we show that the AMS 14 C-based long-term mass accumulation rate (MAR) of an organic-rich (>70%) sediment core from Mud Lake, Florida to be ∼5 times lower than the short-term MAR obtained using 239,240 Pu, 137 Cs and excess 210 Pb ( 210 Pb xs ). The measured sediment inventories of 210 Pb xs , 137 Cs and 239,240 Pu are comparable to the atmospheric fallout for the sampling site, indicating very little accelerated sediment erosion over the past several decades. Presence of sharp fallout peaks of 239,240 Pu indicates very little sediment mixing. The penetration depths of 137 Cs and 239,240 Pu were found to be much deeper than expected and this is attributed to their post-depositional mobility. MAR calculated using 14 C-ages in successive layers also indicated decreasing MARs with depth, and was reflective of progressive remineralization. Using first-order kinetics, the sediment remineralization rate was found to be 4.4 × 10 −4 y −1 and propose that over the long-term, remineralization of organic-rich sediment affected the long-term MAR, but not the ratio of 14 C/ 12 C. Thus, the MAR and linear sedimentation rate obtained using 14 C (and other isotope-based methods) could be erroneous, although 14 C ages may not be affected by such remineralization. Long-term remineralization rates of organic matter has a direct bearing on the biogeochemical cycling of elements in aqueous systems and mass balance of elements needs to be taken into consideration.

The surface chemistry of pyrogenic organic matter (PyOM) is altered by a variety of abiotic and biotic oxidative and sorption/desorption processes in the environment. Exposure of PyOM to high energy light prior to addition to soil or sediment, or while entrained in the atmosphere, may induce significant surface photooxidation, i.e., photochemical weathering, altering its environmental reactivity. We report on a 30-day soil incubation experiment testing the effects of the photochemical weathering of a 13 C-enriched ponderosa pine PyOM, produced by pyrolysis at 450 °C, on PyOM and soil organic carbon (SOC) mineralization. PyOM C mineralization was measured for both the photochemically weathered (i.e. UV treated PyOM or PyOMUV) and PyOM not exposed to high-energy light (i.e. PyOMW serving as a dark control). PyOMW exhibited a 3.7 times faster C mineralization rate across the 30-d study, which was driven by a large early mineralization of accessible/labile C during the first 6 d. In contrast, PyOMUV had faster C mineralization rates in the later part of the experiment (days 11–30). Overall, PyOMUV had a 13% lower net C mineralization than the untreated PyOMW where the MRT of accessible PyOMUV-C and PyOMW-C was calculated at 25.7 ± 6.8 d and 1.7 ± 0.2 d, respectively. Both forms of PyOM promoted a similar net reduction in native SOC mineralization (i.e., negative priming) of approximately 50% relative to the unamended, control soil. Addition of either PyOM form resulted in an equivalent minor decrease in the concentration of extractable soil lignin phenols and substituted fatty acids chemistry with respect to the unamended soil. At 30 d, soil phenol oxidase and peroxidase enzyme activities were higher with additions of either form of PyOM compared with the unamended control soils with PyOMUV exhibiting lower activities than PyOMW. Our results indicate that PyOM photochemical weathering can impart important changes to short-term PyOM reactivity and soil microbial activity, which could have important implications for soil systems by ultimately lowering turnover rates for both NSC and PyOM-C.

Bacteria play essential roles in maintaining soil health, including decomposition of organic and inorganic materials as well as processing nutrients and fertilizers. Careful monitoring of microbial activity has become of great interest in agricultural processes as high levels of activity and diversity can be correlated to soil quality, nutrient availability, as well as provide insight on future crop yields. Although many methods and devices have been developed to enable a better understanding and quantification of the microbial activity levels, most of them are based on laboratory culture assays or are difficult to implement in fields. Here, for the first time, we demonstrate feasibility of a non-destructive, real-time monitoring technique that allows measuring the degradation kinetics of a cellulose acetate (CA) membrane as a direct indicator of the level of cellulase activity of the microorganism within the targeted ecosystem. The sensors are made by depositing a 50-micron thick layer of CA onto circular shaped interdigitated electrodes (IDEs) on a FR-4 glass epoxy substrate with an active sensing area of 12 mm2. The kinetic degradation of the CA membrane was determined by measuring the changes in differential impedance across the IDEs at an operating frequency of 10 kHz. As a proof of concept, the sensors were tested in liquid culture media to monitor the cellulase activity of Pseudomonas aeruginosa, as commonly found bacteria in soil and water. The biodegradation of the CA membrane was successfully measured as a distinct decrease in the impedance of the sensor as the number of Colony Forming Units (CFU/mL) increased in the culture environment with an average linear sensitivity of −139.6Ω/log(CFU/mL) and R2 = 0.98. Sensors were also tested on samples taken from agricultural fields used for crop production. Results of sensors performance in soil provides evidence for using this technique for in-field measurements. Unlike conventional culture-based and DNA extraction techniques, the proposed method provides a real-time assessment of the microorganisms’ activity within their ecosystem. Furthermore, the proposed simple electrical sensing approach paves the road towards developing a new class of biosensors able to easily interface with common wireless data acquisition modules for precision agricultural applications.

Intensive row crop agriculture on loess mantled hillslopes in the upper Midwest, USA, accelerates soil erosion and the loss of organic matter by increasing soil aggregate breakdown, changing surface roughness patterns, and leaving soil exposed to rainfall and wind for much of the year. There is a knowledge gap, however, in relating how the dynamics of soil erosion on hillslopes control landscape heterogeneity in terms of particle size, surface soil organic chemistry and reactivity. Simulated rainfall experiments on intensively managed hillslopes in the Clear Creek, IA watershed, USA, revealed that tillage-induced, oriented roughness controls the amount and organic geochemistry of soil particles mobilized downhill. The average discharge rate of mobilized sediment was nearly 30-fold higher when the tillage orientation was parallel to the runoff direction compared to when the tillage orientation (i.e. contour tillage) was perpendicular to the runoff direction. Mobilized particles under contour tillage were higher in organic carbon (OC) content and were relatively less decomposed, based on lignin chemistry, compared to analogous particles under the parallel tillage orientation. Contour tillage increased deposition of denser particles within the furrows and increased the release of the finer, lighter, and organic-rich material during over-spilling and contour breach. Our findings have important implications for understanding how the interaction of tillage practices and event-based erosion influences the spatial heterogeneity of soil geochemistry and potentially soil health across agricultural landscapes as well as understanding what controls the geochemical signature of soil erosion into streams.

To test the impact of a range of long-term land use types on the partitioning of microbial residues among soil particles, samples from a Mollisol with plots under 100 years of continuous arable cropping, 30 years of simulated overgrazing to severely degraded bare soil, or 30 years of grassland restoration were investigated. The microbial residues, which were assessed among three particle-size fractions (

The environmental fate of functionalized carbon nanomaterials (CNM) remains poorly understood. Using 13C-labeled nanomaterial we present the results of a study investigating the mineralization and microbial uptake of surface-functionalized C60 (fullerols) in agricultural soils with contrasting properties. Soil microcosms rapidly mineralized fullerol C, as determined by 13C-content in the respired CO2, with higher fullerol mineralization in an organic, clay-rich soil versus a silty, low C soil (∼56.3% vs ∼30.9% fullerol C mineralized over 65 days). By tracking the enriched 13C from fullerol into microbial phospholipid fatty acids (PLFA) we also report, for the first time, the incorporation of nanomaterial-derived C into soil microbial biomass, primarily by fungi and Gram-negative bacteria. While more fullerol C was incorporated into PLFA in the organic C-rich soil (0.77% vs 0.19% of PLFA C), this soil incorporated fullerol C into biomass less efficiently than the silty, low C soil (0.13% and 0.84% of assim...

While soil organic carbon (SOC) accumulation and stabilization has been increasingly the focus of ecosystem properties, how it could be linked to soil biological activity enhancement has been poorly assessed. In this study, topsoil samples were collected from a series of rice soils shifted from salt marshes for 0, 50, 100, 300 and 700 years from a coastal area of eastern China. Soil aggregates were fractioned into different sizes of coarse sand (200–2000 µm), fine sand (20–200 µm), silt (2–20 µm) and clay (

We know little about how shifts in tree species distribution and increases in forest fire intensity could affect the formation of pyrogenic organic matter (PyOM) or charcoal, one of the most important and persistent soil organic matter pools. This limitation arises partly because the role of the precursor wood in controlling PyOM formation is unclear. The current study shows how tree species and pyrolysis temperature (200, 300, 450 and 600 °C) interact to control the physicochemical structure of the PyOM experimentally derived from 13C/15N-enriched Pinus banksania and Acer rubrum, two important co-occurring gymnosperm and angiosperm tree species from North American boreal-temperate ecotones. Complementary physicochemical and thermodynamic measurements revealed different susceptibilities of the two wood species to charring, with PyOM intermediates formed at lower temperature from the pine, indicating that the tree species regulated the efficacy of PyOM formation. Particularly, we report high-resolution data describing the comprehensive chemical architecture of PyOM (both –C and –N) as they are formed, which are complemented by unique molecular-level insights on their labile fractions. We posit that the tree species and pyrolysis temperature interaction reflects distinctive anatomical features of the two major tree taxa, including greater effective porosity in gymnosperms that promote the loss of volatiles and enhance the heat exposure of bio-components. This study points to a higher temperature threshold for PyOM production in maple forests compared with pine forests, resulting in potentially more degradable and less sorbtive PyOM in ecotones dominated by the former species.

Analytical techniques to assess the degree of alteration of pyrogenic black carbon (C) in soils and sediments are needed to gauge the role of environment and time in the dynamics of this stable carbon form. The benzenecarboxylic acids (B n CA, with n = number of carboxylic groups) and naphthalene analogues (N n CA) released by thermally assisted hydrolysis and methylation (THM) of black C have the potential to yield information about black C oxidation state but it remains unclear to what extent the carboxylic groups in B n CA and N n CA are native to the sample or form as analytical artefacts during the THM reaction. In an effort to clarify the source of analytical products and investigate long term black C oxidation in a soil environment we applied THM gas chromatography mass spectrometry (THM-GC–MS) using 13 C-labeled tetramethylammonium hydroxide ( 13 C-TMAH) to oak-derived black C samples isolated from a colluvial soil profile dating to 50–8100 cal BP. The results showed that the B n CA and N n CA originate from the black C and are potentially usable as oxidation proxies, with the exception of B1CA and hydroxyl-B1CA which have a significant source in lignin. The cumulative abundance of B n CA (excluding B1CA) and N n CA increased with age of the black C ( P

Soil degradation is an increasing threat to the sustainability of agriculture worldwide. Use of biochar from bio-wastes has been proposed as an option for improving soil fertility, degraded land restoration, and mitigating the greenhouse gas emissions associated with agriculture. Over the past 10 years, there have been hundreds of research studies on biochar from which it may be possible to determine appropriate methods for use of biochar to improve sustainable agriculture. To address potential gaps in our understanding of the role of biochar in agriculture, in this paper are reviewed the studies of 798 publications of field-, greenhouse- and laboratory-based biochar amendment soil experiments conducted as of August, 2015. Here we report the findings from a quantitative assessment. The majority of published studies have been performed in developed countries in soils that are less impaired than those found in many developing countries. The majority of the works involves laboratory and greenhouse pot experiments rather than field studies. Most published studies on biochar have used small kiln or lab prepared biochars rather than commercial scale biochars. And, most studies utilize wood and municipal waste feedstocks rather than crop residues though the later are often available in agriculture. Overall, the lack of well-designed long-term field studies using biochar produced in commercial processes, may be limiting our current understanding of biochar’s potential to enhance crop production and mitigate climate change. We further recommend greater alliance between researchers and biochar production facilities to foster the uptake of this important technology at a global scale.

Woody encroachment and subsequent brush management aimed at reducing woody plant cover can alter soil organic carbon (SOC) pools. However, brush management influences on the sources and stability of SOC is unknown. Using a space-for-time approach in a site with closely co-located patches representing unencroached grassland, woody encroachment, and brush management, we coupled stable isotopes and plant-derived biomarkers to quantify how woody encroachment alters input sources and stability of SOC and how these patterns change with brush management. Stable isotopes, lignin-derived phenols, substituted fatty acids, and carbon content of density fractions were measured in soils collected in shrub canopy interspaces, under live shrubs, and under shrubs killed 8 or 52 y previously. Bulk SOC and C3-derived SOC were higher in shallow soil (0–5 cm) under live shrubs than in interspace soil. Long-term brush management showed a decline in total SOC stocks, substituted fatty acids, and C3-derived SOC that were associated with the soil light fraction. Despite declines in bulk SOC following brush management, accumulated C3-derived SOC pools in the dense fraction remained largely stable following brush management. Woody encroachment increases the proportion of poorly-protected light fraction and loosely-mineral associated SOC derived from leaf litter, which is lost within several decades after brush management. However, woody encroachment produced a stabilized mineral-bound pool of C3- and C4-derived SOC that remained 52 years after brush management, suggesting that woody encroachment has the potential for long-term SOC stabilization.

China is a key global region vulnerable to climate change; however, limited studies have focused on the combined impacts of atmospheric CO2 enrichment and warming on crop production in arable land, especially in rice paddies in China. To address this issue, a 4 year open-air field experiment during 2010–2014 was conducted to simulate the impact of climate change on crop production in a rice paddy in southeast of China. Four treatments including the ambient condition (CK), CO2 enrichment (500 ppmv, CE), warming of canopy air (2 °C above the ambient, WA), and the combined CO2 enrichment and warming (CW) were used to investigate the responses of total biomass, crop yield and harvest index. In general, different treatments significantly affected wheat and rice production. Compared to CK, CE significantly increased grain yield of rice by 8%. In contrast, the decreases of 26.2% and 10% in wheat and rice yield were observed under WA. However, there was no significant difference of wheat production between CW and CK, while rice yield and biomass were slightly decreased by a mean of 4.8% and 5.3% over 4 years, indicating the positive effect of CO2 enrichment was unable to compensate for the negative impact of warming. The interannual variations of the responses were also observed in this study. The variation of wheat yields during 4 years was much higher than that of rice yields; however, significant changes in the stability of rice biomass and harvest index were observed under CE and WA. The results indicated both stabilizing and increasing grain yield under climate change are major challenges for agriculture in developing countries.

Commonly, the topographic influence on soil hydrology is calculated as a Topographic Wetness Index (TWI), which often correlates with surface soil properties, such as carbon and nitrogen, across broad spatial scales. However, traditional TWI methods can be ineffective at capturing finer scale variations when depression filling approaches are used and they do not incorporate localized soil texture controls on infiltration. We developed a new Dynamic Wetness Index (DWI) that attempts to account for the persistence of soil moisture over time at the microtopographic scale (~1 m2) by including inputs of measured soil texture, and information from the Dhara modeling framework that incorporates canopy process and surface-subsurface hydrologic models. DWI and TWI values were correlated with measured soil geochemical properties across six study sites (four agricultural sites, one restored prairie, and one forest site) within the Upper Sangamon River Basin, in central Illinois, USA. Relative to TWI, DWI improved correlations with certain measured soil surface geochemistry (pH R = −0.53), δ13C R = 0.13, δ15N R = 0.44) and certain lignin phenols (vanillyl, cinnamyl/vanillyl, syringyl-vanillyl-cinnamyl/substituted fatty acids). DWI positively correlated with indicators of lignin oxidation, indicating that wetter soils have higher potential for lignin decomposition. In this small dataset, relative to TWI the data show DWI increased significance and decreased the range of correlations with soil moisture and certain surface soil geochemistry parameters driving plant chemistry decay and nitrogen cycling.

Water-soluble organic carbon (WSOC) represents a small but dynamic fraction of soil organic carbon (SOC) and plays a key role in the terrestrial carbon cycle. Some researchers have indicated that the WSOC has been affected by soil tillage. However, there is still a gap in knowledge regarding WSOC dynamics within agricultural practices in many regions, including northeast China. This study assesses the influence of a common management practices, namely plastic film mulching (PFM) and fertilization treatments (nitrogen and manure), on the dynamics of WSOC and straw-derived WSOC (WSOCstraw) in continuous maize (Zea mays L.) topsoil (0−20 cm) over a 360-day period. In this study, an in situ 13C-tracing technique using pulse-labeled maize straw within bulk soil and soil aggregates (>2 mm, 1−2 mm, 0.25−1 mm and

The role of tillage practices on soil aggregate properties has been mainly addressed at the pedon scale (i.e., soilscape scale) by treating landscape elements as disconnected. However, there is observed heterogeneity in aggregate properties along flowpaths, suggesting that landscape scale hydraulic processes are also important. This study examines this supposition using field, laboratory and modeling analysis to assess aggregate size and stability along flowpaths under different management conditions: (1) tillage-induced abrasion effects on aggregate size were evaluated with the dry mean weight diameter (DMWD), (2) raindrop impact effects were evaluated with small macroaggregate stability (SMAGGSTAB) using rainfall simulators, and (3) these aggregate proxies were studied in the context of connectivity through the excess bed shear stress (&delta, ), quantified using a physically-based landscape model. DMWD and SMAGGSTAB decreased along the flowpaths for all managements, and a negative correspondence between the proxies and &delta, was observed. &delta, captured roughness effects on connectivity along the flowpaths: highest connectivity was noted for parallel-ridge-till flowpaths, where &delta, ranged from 0&ndash, 8.2 Pa, and lowest connectivity for contour-ridge-till flowpaths, where &delta, 1.1 Pa. High tillage intensity likely led to an increase in aggregate susceptibility to hydraulic forcing, reflected in the higher gradients of aggregate size and stability trendlines with respect to &delta, Finally, a linear relationship between DMWD and SMAGGSTAB was established.

Beneficial microbial associations enhance the fitness of most living organisms, and wood-feeding insects offer some of the most striking examples of this. Odontotaenius disjunctus is a wood-feeding beetle that possesses a digestive tract with four main compartments, each of which contains well-differentiated microbial populations, suggesting that anatomical properties and separation of these compartments may enhance energy extraction from woody biomass. Here, using integrated chemical analyses, we demonstrate that lignocellulose deconstruction and fermentation occur sequentially across compartments, and that selection for microbial groups and their metabolic pathways is facilitated by gut anatomical features. Metaproteogenomics showed that higher oxygen concentration in the midgut drives lignocellulose depolymerization, while a thicker gut wall in the anterior hindgut reduces oxygen diffusion and favours hydrogen accumulation, facilitating fermentation, homoacetogenesis and nitrogen fixation. We demonstrate that depolymerization continues in the posterior hindgut, and that the beetle excretes an energy- and nutrient-rich product on which its offspring subsist and develop. Our results show that the establishment of beneficial microbial partners within a host requires both the acquisition of the microorganisms and the formation of specific habitats within the host to promote key microbial metabolic functions. Together, gut anatomical properties and microbial functional assembly enable lignocellulose deconstruction and colony subsistence on an extremely nutrient-poor diet.

The addition of pyrogenic organic matter (PyOM), the aromatic carbon-rich product of the incomplete combustion of plant biomass or fossil fuels, to soil can influence the rate of microbial metabolism of native soil carbon. The interaction of soil heterotrophs with PyOM may be governed by the surficial chemical and physical properties of PyOM that evolve with environmental exposure. We present results of a 36-day laboratory incubation investigating the interaction of a common white-rot fungus, Trametes versicolor, with three forms of 13C-enriched (2.08 atom% 13C) PyOM derived from Pinus ponderosa (450 °C): one freshly produced, and two artificially weathered (254 nm, UV light-water treatment and water-leaching alone). Analysis (FTIR, XPS) of the UV-weathered PyOM showed increased aliphatic C–H content and oxidation of aromatic carbon relative to both the original and water-leached PyOM. The addition of both weathered forms of PyOM stimulated (positively primed) fungal respiration of the growth media, while the unaltered PyOM mildly inhibited (negatively primed) respiration. Artificial weathering resulted in higher oxidative (laccase and peroxidase) enzyme activity than unaltered PyOM, possibly the result of a diminished capacity to bind reactive substrates and extracellular enzymes after weathering. However, and contrary to expectations, simple water-leached weathering resulted in a relatively higher enzyme activity and respiration than that of UV-weathering. The 13C content of respired CO2 indicated negligible fungal oxidation of PyOM for all treatments, demonstrating the overall low microbial reactivity of this high temperature PyOM. The increased enzymatic and positive priming response of T. versicolor to weathered PyOM highlights the importance of weathering-induced chemistry in controlling PyOM–microbe–soil carbon interactions.

In temperate deciduous forests of eastern USA, most earthworm communities are dominated by invasive species. Their structure and functional group composition have critical impacts on ecological properties and processes. However, the factors determining their community structure are still poorly understood, and little is known regarding their dynamics during forest succession and the mechanisms leading to these changes. Earthworm communities are usually assumed to be stable and driven by vegetation. In contrast, the importance of dispersal and ecological drift is seldom acknowledged. By analyzing a 19-year dataset collected from forest stands in eastern USA, we demonstrated that on a decadal timescale, earthworm community dynamics are shaped by the interplay of selection, dispersal, and ecological drift. We highlighted that forests at different successional stages have distinct earthworm species and functional groups as a result of environmental filtering through leaf litter quality. Specifically, young forests are characterized by soil-feeding species that rely on relatively fresh soil organic matter derived from fast-decomposing litter, whereas old forests are characterized by those feeding on highly processed soil organic matter derived from slow-decomposing litter. In addition, year-to-year species gains and losses are primarily driven by dispersal from regional to local species pools, and by local extinction resulted from competition and ecological drift. We concluded that with continued dispersal of European species and the recent "second wave" of earthworm invasion by Asian species from the surrounding landscape, earthworms at the investigated forests are well-established, and will remain as the major drivers of soil development for the foreseeable future.

Elevated nitrogen (N) deposition has the potential to increase litter and soil carbon (C) storage by suppressing lignolytic activity, but reports of the response of forest floor and soil have shown inconsistent responses. We investigated organic carbon and nitrogen as well as lignin phenols and substituted fatty acids (SFA) in forest floor litter and organic horizons, and mineral soil profiles from a mixed broad-leaf Korean pine (Pinus koraiensis) forest, China after 6 years of N addition treatment at double the current N deposition rate. Total C and N were not influenced by experimental N deposition. However, incipient changes in extractable lignin phenol concentration were seen for degraded litter (P = 0.100) exhibiting increases of about 5% while mineral soil, surface litter and O-horizon showed no change. The degree of lignin oxidation was not substantially influenced in any layer although a significant decrease in vanillyl lignin phenol oxidation was measured in the degraded litter under elevated N. Extractable substituted fatty acids in the forest floor and mineral soil horizons were also, essentially, insensitive to N addition with the minor exception of the O-horizon showing a small but significant (� 16%, P = 0.041) increase. Our results are consistent with one group of literature showing little change in overall soil and litter character under short term, 5–10 years, of N addition. Minor changes in molecular C dynamics, such as those observed for lignin phenols and substituted fatty acids could possibly be attributed to the suppression of microbial decay under N addition.

Soil microorganisms secrete enzymes used to metabolize carbon (C), nitrogen (N), and phosphorus (P) from the organic materials typically found in soil. Because of the connection with the active microbial biomass, soil enzyme activities can be used to investigate microbial nutrient cycling including the microbial response to environmental changes, transformation rates and to address the location of the most active biomass. In a 9-year field study on global change scenarios related to increasing N inputs (ambient to 15 g N m � 2 yr � 1 ) and precipitation (ambient to 180 mm yr � 1 ), we tested the activities of soil bglucosidase (BG), N-acetyl-glucosaminidase (NAG) and acid phosphomonoesterase (PME) for three soil aggregate classes: large macroaggregates (>2000 mm), small macroaggregates (250e2000 mm) and microaggregates (

Carbon isotope (δ 13 C) compositions of total organic carbon (TOC) as well as several extracted higher plant derived lignin biomarkers, along with the recovery of grass phytoliths, provide the first direct evidence of existence of extensive grass land (C4) vegetation over the Ganges deltaic plain during the Last Glacial Maximum (LGM). The earliest Holocene (∼9 ka) is marked by pronounced 13 C depletion in the lignin phenols coinciding with rapid sea level rise, intensified monsoon, and replacement of grassland vegetation by mangroves. Another C4 invasion phase is identified during the late Holocene (∼6–2 ka). Both the LGM and late Holocene C4 phases coincide with the well known monsoon minima. The study suggests that change in pCO 2 might not be the singular driver of vegetation change as proposed recently and the climate models must take the monsoon like mega-climate processes into account for reconstructing the glacial biomes.

Highlights This work utilizes “multi-stage pulse labeling” 15N applications, primarily during reproductive growth stages, as a phenotyping strategy to identify maize hybrids with superior N use efficiency (NUE) under low N conditions. Research using labeled isotopic N (15N) can precisely quantify fertilizer nitrogen (N) uptake and organ-specific N allocation in field crops such as maize (Zea mays L.). The overall research objective was to study plant N uptake patterns potentially correlated with N use efficiency (NUE) in field-grown maize hybrids using a “multi-stage pulse labeling” 15N phenotyping strategy with an emphasis on the reproductive period. Five hybrids varying in NUE were compared under zero N fertilizer application (0N) plus a moderate rate of 112 kg N ha−1 (112N) in 2013 (2 locations) and 2014 growing seasons. The equivalent of 3.2 (2013) to 2.1 (2014) kg of 15N ha−1, as labeled Ca(15NO3)2, was injected into soil on both sides of consecutive plants at multiple stages between V14 and R5. Aboveground plant biomass was primarily collected in short-term intervals (4–6 days after each 15N application) in both years, and following a single long-term interval (at R6 after 15N injection at R1) in 2014. Averaged across hybrids and site-years, the moderate N rate (112N) increased absolute 15N uptake at all stages; however, plants in the 0N treatment allocated proportionally more 15N to reproductive organs. Before flowering, short-term recovery of 15N (15Nrec) totaled ~0.30 or 0.40 kg kg−1 of the 15N applied, and ~50% of that accumulated 15Nu was found in leaves and 40% in stems. After flowering, plant 15Nrec totaled ~0.30 kg kg−1 of 15N applied, and an average 30% of accumulated 15Nu was present in leaves, 17% in stems, and the remainder—usually the majority—in ears. At the R5 stage, despite a declining overall rate of 15N uptake per GDD thermal unit, plant 15Nrec represented ~0.25 kg kg−1 of 15N applied, of which ~65% was allocated to kernels. Overall long-term 15Nrec during grain filling was ~0.45 and 0.70 kg kg−1 of total 15N applied at R1 with 0 and 112N, respectively, and most (~77%) 15N uptake was found in kernels. The “multi-stage pulse labeling” technique proved to be a robust phenotyping strategy to differentiate reproductive-stage N uptake/allocation patterns to plant organs and maize efficiencies with newly available fertilizer N.

Although carbon nanomaterials such as single-walled carbon nanotubes (SWCNT) are becoming increasingly prevalent in manufacturing, there is little knowledge on the environmental fate of these materials. Environmental degradation of SWCNT is hindered by their highly condensed aromatic structure as well as the size and aspect ratio, which prevents intracellular degradation and limits microbial decomposition to extracellular processes such as those catalyzed by oxidative enzymes. This study investigates the peroxidase and laccase enzymatic response of the saprotrophic white-rot fungi Trametes versicolor and Phlebia tremellosa when exposed to SWCNTs of different purity and surface chemistry under different growth conditions. Both unpurified, metal catalyst-rich SWCNT and purified, carboxylated SWCNTs promoted significant changes in the oxidative enzyme activity of the fungi while pristine SWCNT did not. These results suggest that functionalization of purified SWCNT is essential to up regulate enzymes that may be capable of decomposing CNT in the environment. © 2014 Published by Elsevier Ltd.

As human activities have intensified along tropical coastlines, the anthropic influ- ence on adjacent coral reefs has become increasingly deleterious. Changes in land use generally degrade water quality, but controversy persists over the degree to which reduced water quality affects the ecology of reef communities. We cored reef frameworks at 4 sites in Bahia Almirante, a semi-enclosed, coastal lagoon in northwestern Panama, to explore the historical relationship between turnover in coral-species dominance and terrigenous input. The coral constituents of the cores were analyzed in tandem with lignin-phenol concentrations. Chronologies and sedimenta- tion rates were determined from 210 Pb profiles in the cores. Increased terrigenous input from agri- cultural development and expansion of the human population degraded water quality in Bahia Almirante over the last century. Documented episodes of heavy rainfall after 1970 accelerated a phase shift from dominance by branching corals of the genus Porites to dominance by the lettuce coral Agaricia tenuifolia at water depths of 5 to 10 m by increasing runoff, increasing sediment and nutrient loads, and lowering light levels. The phase shift in coral dominance was unprece- dented on a millennial time scale and the degree to which it occurred varied along a gradient of terrigenous input to the Bahia.

Previous studies have demonstrated positive net primary production effects with increased nitrogen (N) and water availability in Inner Mongolian semi-arid grasslands. However, the responses of soil carbon (C) and N concentrations and soil enzyme activities as indicators of impacts of long-term N (urea) and water addition are still unclear. We tested the effect of 7 years of a N and water addition experiment on soil C, N, and specific soil-bound enzymes in a semi-arid grassland of Inner Mongolia. We determined concentrations of soil organic carbon (SOC) and soil total nitrogen (TN) in both the 0–10 and 10–20 cm soil layers. Concentrations of labile carbon (LC) and inorganic nitrogen (nitrate and ammonium), and soil pH were measured. Additionally, soil dehydrogenase (DHA), β-glucosidase (BG) and acid and alkaline phosphomonoesterase (PME) enzyme activities were determined in the 0–10 cm soil layer. SOC concentration in the 0–10 cm soil layer showed no response to N addition or N plus water addition, but increased with water addition alone by 0.3–15.7 %. N addition significantly increased nitrate by 46.0–138.4 % and ammonium by 19.0–73.3 % in the 0–10 cm soil layer, whereas water addition did not affect them. The activities of DHA and alkaline PME enzymes, as well as soil pH, in the 0–10 cm layer decreased with N addition, however water addition alone caused these enzyme activities to increase. Unlike the surface soil (0–10 cm), the lower soil layer (10–20 cm), was responsive to N and water addition in that SOC and TN concentrations decreased with N addition and increased with water addition. The accumulation of SOC and TN in N and water addition plots may be caused by the input of plant biomass exceeding SOC decomposition. Decrease in microbial activity, derived from decreased DHA and alkaline PME activities might result from suppression effects of lower pH and decreased microbial N supply. Water availability is proved to be more important than N availability for soil C and N accumulation in this semi-arid grassland.

In this study, we examined the response of surface soils to increased leaf and wood litter input within adjacent successional forests recovering from agricultural disturbance at the Smithsonian Environmental Research Center (SERC), Maryland, USA. Previous studies at this site demonstrated an arrested development of O-horizon, even after 130 years of forest growth, and an annual loss of leaf litter in forests with the highest abundance of invasive earthworms. Biogeochemical indices of plant biopolymer dynamics, i.e. extractable lignin and substituted fatty acids (SFAs), were applied to soil physical fractions in order to assess the fate of 5 years of increased Tulip poplar (Liriodendron tulipifera L.) wood and leaf litter into O-horizon and mineral soil particles of purportedly different protection levels in this recovering forest system. Our results showed that in this continuously-disturbed recovering system the pattern of litter incorporation into soil varied with both litter type and forest age. For example, young successional forests, that also contained higher abundances of soil feeding endogeic earthworms, incorporated wood amendments deeper into soils and in a predominantly particulate organic matter (POM) form than older successional systems with predominantly litter and surface dwelling earthworms. Soil lignin concentration increased sharply with wood amendments in both forest stages, but young successional forests exhibited incorporation of fresher lignin into both POM and silt and clay (SC) fractions over 0–5 cm and 5–10 cm depths while old forests only increased in POM in the 0–5 cm depth. We attribute these differences to the higher rates of physical mixing from soil feeding endogeic species and potentially lower fungal activity in young successional forests. However, despite nearly 2.5 times of background annual leaf litter input over 5 years, neither total C content nor SFA concentration in soil fractions increased, a phenomenon we attribute to full decomposition of leaf litter amendments. These results demonstrate how the chemical trajectory of soils and litter layers in recovering forests can be a function of both legacy and current disturbance.

Pyrolysis molecular-beam mass spectrometry (PyMBMS) was tested as a high-throughput method for relative abundances of guaiacyl and syringyl lignin in lignocellulosic cell-wall materials from stems of a population of maize intermated B73 × Mo17 (IBM) recombinant inbred lines. Variations of up to twofold across the population in phenylpropanoid abundance were observed. Several histochemical and quantitative biochemical assays were used to validate the mass spectrometric data for lignin, hydroxycinnamic acids, crystalline cellulose, non-cellulosic glucans, and xylans. We demonstrate PyMBMS to be a valid high-throughput screen suitable for analysis of lignin abundance in large populations of bioenergy grasses. Pentose from xylans and hexose from cellulosic and non-cellulosic glucans also varied substantially across the population, but abundances of diagnostic fragments for these monosaccharides were not well correlated with the abundance of cell-wall polysaccharides.