Eldor Paul

• BSc ,MSc University of Alberta; PhD University of Minnesota
• Colorado State University

Rapid warming in the Arctic threatens to amplify climate change by releasing the region’s vast stocks of soil carbon to the atmosphere. Increased nutrient availability may exacerbate soil carbon losses by stimulating microbial decomposition or offset them by increasing primary productivity. The outcome of these competing feedbacks remains unclear....

As atmospheric carbon dioxide concentrations, [CO2Air], continue their uncontrolled rise, the capacity of soils to accumulate or retain carbon is uncertain. Free-air CO2 enrichment (FACE) experiments have been conducted to better understand the plant, soil and ecosystem response to elevated [CO2], frequently employing commercial CO2 that imparts a...

The long-standing perspective that recalcitrance of soil organic carbon (SOC) controls its stability and persistence has shifted to one in which physical inaccessibility of SOC to microorganisms plays a predominant role. This paradigm shift has been facilitated by analytical techniques that isolate SOC into physical fractions protected from decompo...

Mineral-associated organic matter (MAOM) is a key component of the global carbon (C) and nitrogen (N) cycles, but the processes controlling its formation from plant litter are not well understood. Recent evidence suggests that more MAOM will form from higher quality litters (e.g., those with lower C/N ratios and lower lignocellulose indices), than...

Soil organic matter (SOM) is critical for maintaining soil fertility and long-term agricultural sustainability. The molecular composition of SOM is likely altered due to global climate and land-use change; but rarely are these two aspects studied in tandem. Here we used molecular-level techniques to examine SOM composition along a bi-continental (f...

Soil organic matter (SOM) is extremely complex. It is composed of hundreds of different organic substances and it has been difficult to quantify these diverse substances in a dynamic- ecosystem functioning standpoint.Analytical pyrolysis has been used to compare chemical differences between soils, but its ability to measure the absolute amount of a...

This review covers historical perspectives, the role of plant inputs, and the nature and dynamics of soil organic matter (SOM), often known as humus. Information on turnover of organic matter components, the role of microbial products, and modeling of SOM, and tracer research should help us to anticipate what future research may answer today's chal...

Human impacts on biogeochemical cycles are evident around the world, from changes to forest structure and function due to atmospheric deposition, to eutrophication of surface waters from agricultural effluent, and increasing concentrations of carbon dioxide (CO2) in the atmosphere. The National Ecological Observatory Network (NEON) will contribute...

The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have be...

Our science, based on a successful past, has great potential for an exciting, dynamic future if we understand it and apply its unifying principles. Advances in genomic studies are identifying multitudes of new soil biota. Automated, analytical instrumentation and modeling are characterizing soil organic matter and its dynamics. Soil nutrient transf...

Priming is the altered rate of mineralization of native soil organic matter (SOM) induced by an amendment with an organic substrate, and can be either positive or negative depending on the nature of the substrate. Coupled with the use of tracer (14C, 13C, 15N) techniques, measurements of the rates of CO2 evolution and organic N mineralization are u...

Declining rates of soil respiration are reliably observed during long-term laboratory incubations. However, the cause of this decline is uncertain. We explored different controls on soil respiration to elucidate the drivers of respiration rate declines during long-term soil incubations. Following a long-term (707 day) incubation (30 °C) of soils fr...

Chemical recalcitrance of biomolecules, physical protection by soil minerals and spatial inaccessibility to decomposer organisms are hypothesized to be primary controls on soil organic matter (SOM) turnover. Previous studies have observed increased sequestration of plant derived aliphatic compounds in experimentally warmed soils but did not identif...

Climate change, land use practices, and other consequences of a growing human population affect soil sustainability. Unfortunately, scientists studying belowground processes have traditionally been limited to data and models that capture intermediate spatial and temporal scales, failing to accurately characterize soil phenomena at societally releva...

Determining the dynamics of carbon (C) as a function of vegetation and residue inputs is important for predicting changes in ecosystem functions and the global C cycle. Litter and soil samples were analyzed from plantations of eastern red cedar (Juniperous virginiana) and ponderosa pine (Pinus ponderosa) and native prairie at the Nebraska National...

a b s t r a c t Soil organic matter (SOM) is one of the earth's largest reservoirs of actively cycled carbon and plays a crit-ical role in various ecosystem functions. In this study, mineral soils with the same parent material and of similar approximate age were sampled from the same climatic region in Halsey, Nebraska to determine the relationship...

Diffuse-reflectance Fourier-transform mid-infrared spectroscopy (MidIR) can identify the presence of important organic functional groups in soil organic matter (SOM); however, spectral interpretation needs to be validated to correctly assess changes in SOM quality and quantity. We amended soils with known standards, increasing the total C in the sa...

The activities of extracellular enzymes, the proximate agents of decomposition in soils, are known to depend strongly on temperature, but less is known about how they respond to changes in precipitation patterns, and the interaction of these two components of climate change. Both enzyme production and turnover can be affected by changes in temperat...

The decomposition and transformation of above- and below-ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been largely uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling an...

A chemically protected pool of soil organic matter contributes to soil carbon storage. It has been hypothesized that specific guilds of microbes grow on labile SOM, while others grow on recalcitrant SOM. However, previous studies have shown similar average levels of microbial respiration of fresh litter amended to fresh soil and long term incubated...

Radioactive tracers were used to study the C allocation to coarse and fine roots, aboveground plant tissues, mycorrhizal lipids, belowground respiration, and soil in a mycorrhizal association. Sorghum bicolor (L.) Moench was grown in soil with a nonmycorrhizal microbial inoculum with and without Glomus clarum, a mycorrhizal inoculant. Fifty-one-day...

Background/Question/Methods Concern over the increase in atmospheric CO2 content has created interest in the mechanisms that increase and stabilize organic matter in soils. The present study examined the impacts of calcium and nitrogen on soil organic matter (SOM) in nutrient poor pine soils. Literature supports that calcium increases soil C cont...

Management induced microbial community shifts may be linked to soil organic matter stability. The objective of our study is to elucidate how microbial composition shifts with different agricultural practices. Soil samples (0-20 cm depth) were collected from Hoytville, Ohio. Experimental treatments included native forest (NF), conventional tillage m...

Soil organic matter dynamics and composition reflect the effects of vegetation, biota, climate, physical protection, and land-use. In the short-term we might expect the decomposition of litter and the stable organic matter to be most affected by the size and composition of the microbial community and the chemistry of the substrate. We compared soil...

Soil organic matter dynamics are very tightly controlled by the amount of available N. Enrichment of N stocks through the presence of symbiotic N fixers has a significant impact on the characteristics and kinetics of soil organic matter. Our study focuses on Sand Ridge State Forest (SRSF), a 3000 ha. mixed species series of plantations near Manito,...

Knowledge of the pools and fluxes of C and N soil components is required to interpret ecosystem functioning and improve biogeochemical models. Two former grassland soils, where wheat or corn are currently growing, were studied by kinetic analysis of microbial biomass C and N changes, C and N mineralization rates, acid hydrolysis, and pyrolysis. Nea...

Background/Question/Methods Studying soil organic matter dynamics is especially important in understanding ecosystem dynamics and carbon and nitrogen cycling in global change. Agricultural management and restoration practices are known to affect the ability of soil to store carbon. Previous studies show soil organic matter dynamics are controlled...

Background/Question/Methods Decomposition of a range of soil organic matter (SOM) labilities requires a suite of vastly diverse microbial functional groups found in soil. It is intuitive that a shift in the soil microbial community function has the potential to alter carbon cycling rates at global scales. However, decomposition models (CENTURY, R...

We performed mid-infrared (MidIR) spectral interpretation of fractionated fresh and incubated soils to determine changes in soil organic matter (SOM) chemistry during incubation. Soils from four sites and three depths were processed to obtain the light fraction (LF), particulate organic matter (POM), silt-sized (silt), and clay-sized (clay) fractio...

When fungal hyphae were separated from two mineral soils by wet sieving and density gradient centrifugation, a preparation consisting of 50% of the total soil fungal hyphae and 3% of the soil dry weight was obtained. Residual soil particles were removed by an additional sieving step which resulted in a final recovery of 20% of the fungal hyphae fro...

A litter-bag technique was used to measure decay rates and assess changes in organic and inorganic constituents of ponderosa pine (Pinusponderosa Laws.) needle litter during decomposition over a 2-year period in old- and young-growth forests in the Sierra Nevada of California. Rates of mass loss were among the lowest reported for temperate and bore...

We examined the effects of fertilization and gypsy moth defoliation of hybrid poplar (Populus ×canadensis Moench 'Eugenei') on ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungal colonization, ECM richness, and ECM composition in the summers of 1997 and 1998. The factorial experiment included two levels of defoliation (defoliated and contr...

A non-nodulating cultivar of Pisum sativum cv. Afghanistan was studied to characterize the nature and location of the non-nodulating factor. Nodule formation was not temperature sensitive. Rhizobium leguminosarum could exist in the rhizosphere. Root secretions did not decrease nodulation in adjacent normal plants, nor did the proximity of normal pl...

The uncertainty associated with how projected climate change will affect global C cycling could have a large impact on predictions of soil C stocks. The purpose of our study was to determine how various soil decomposition and chemistry characteristics relate to soil organic matter (SOM) temperature sensitivity. We accomplished this objective using...

The general consensus is that a warming climate will result in the acceleration of soil organic matter (SOM) decomposition, thus acting as a potential positive feedback mechanism. However, the debate over the relative temperature sensitivity of labile versus recalcitrant SOM has not been fully resolved. We isolated acid hydrolysis residues to repre...

Policies that encourage greenhouse-gas emitters to mitigate emissions through terrestrial carbon (C) offsets -C sequestration in soils or biomass -will promote practices that reduce erosion and build soil fertility, while fostering adaptation to climate change, agricultural development, and rehabilitation of degraded soils. However, none of these b...

Soil carbon (C) dynamics and sequestration are controlled by interactions of chemical, physical and biological factors. These factors include biomass quantity and quality, physical environment and the biota. Management can alter these factors in ways that alter C dynamics. We have focused on a range of managed sites with documented land use change...

The aim of this review is to describe and discuss the concepts that have been employed to interpret N mineralization–immobilization in soil, and how N turnover is related to the characteristics of organic N and the biota conducting the transformations. A brief survey of the period before the arrival of electronic searches became available provides...

The field of soil ecology has relatively few fundamental unifying principles that can be used to explain and predict patterns and processes in belowground ecosystems. Here we propose that a first step towards developing a more comprehensive set of unifying principles in soil ecology is to identify and understand the characteristics shared by a wide...

Today’s questions concerning the role of soil organic matter (SOM) in soil fertility, ecosystem functioning and global change can only be addressed through knowledge of the controls on SOM stabilization and their interactions. Pyrolysis molecular beam mass spectrometry (py-MBMS) provides a powerful and rapid means of assessing the biochemical compo...

Global climate change may induce accelerated soil organic matter (SOM) decomposition through increased soil temperature, and thus impact the C balance in soils. We hypothesized that compartmentalization of substrates and decomposers in the soil matrix would decrease SOM sensitivity to temperature. We tested our hypothesis with three short-term labo...

Soil organic matter can be protected from decomposition through physical protection within soil aggregates, chemical protection through association with mineral particles, and biochemical stabilization through biotic or abiotic creation of decay-resistant compounds. However, the methods most often used to differentiate soil organic matter usually l...

Microorganisms play key roles in biogeochemical cycling by facilitating the release of nutrients from organic compounds. In doing so, microbial communities use different organic substrates that yield different amounts of energy for maintenance and growth of the community. Carbon utilization efficiency (CUE) is a measure of the efficiency with which...

Soil C decomposition is sensitive to changes in temperature, and even small increases in temperature may prompt large releases of C from soils. But much of what we know about soil C responses to global change is based on short-term incubation data and model output that implicitly assumes soil C pools are composed of organic matter fractions with un...

The relationship between organic matter (OM) lability and temperature sensitivity is disputed, with recent observations suggesting that responses of relatively more resistant OM to increased temperature could be greater than, equivalent to, or less than responses of relatively more labile OM. This lack of clear understanding limits the ability to f...

Soils have often been viewed as a black box. Soil biology is difficult to study with the precision we would wish, due to the presence of considerable soil heterogeneity, a huge diversity of organisms, and a plethora of interacting processes taking place in a complex physical-chemical environment. We have isolated a tiny fraction of the known organi...

Soil organic matter (SOM) in agricultural soils comprises a significant part of the global terrestrial C pool. It has often been characterized by utilizing a combination of chemical dispersion of the soil followed by physical separation. We fractionated soil samples under continuous corn (Zea mays L.) rotations at four long-term sites in the Corn B...

Afforestation of agricultural lands can provide economically and environmentally realistic C storage to mitigate for elevated CO2 until other actions such as reduced fossil fuel use can be taken. Soil carbon sequestration following afforestation of agricultural land ranges from losses to substantial annual gains. The present understanding of the co...

Soil organic matter is the earth's largest terrestrial reservoir of carbon (C). Thus, it serves as a major control on atmospheric carbon dioxide (CO2) levels. To better understand these controls, decreases in soil organic C (SOC), soil microbial biomass (SMB) C, and the role of SMB as a source of mineralizable C were measured during a long-term inc...

Soil organic matter is the earth's largest terrestrial reservoir of carbon (C). Thus, it serves as a major control on atmospheric carbon dioxide (CO2) levels. To better understand these controls, decreases in soil organic C (SOC), soil microbial biomass (SMB) C, and the role of SMB as a source of mineralizable C were measured during a long-term inc...

This chapter discusses soil microbiology, ecology, and biochemistry. Winogradsky (1856–1953) is recognized as the founder of soil microbiology for his contributions to nitrification, anaerobic N2 fixation, sulfur oxidation, and microbial autotrophy. He succeeded in isolating two bacterial types involved in nitrification with the keen insight that t...

The current paradigm in soil organic matter (SOM) dynamics is that the proportion of biologically resistant SOM will increase when total SOM decreases. Recently, several studies have focused on identifying functional pools of resistant SOM consistent with expected behaviours. Our objective was to combine physical and chemical approaches to isolate...

The literature was reviewed and analyzed to determine the feasibility of using a combination of acid hydrolysis and CO2-C release during long-term incubation to determine soil organic carbon (SOC) pool sizes and mean residence times (MRTs). Analysis of 1100 data points showed the SOC remaining after hydrolysis with 6 M HCl ranged from 30 to 80% of...

Different positions within soil macroaggregates, and macroaggregates of different sizes, have different chemical and physical properties which could affect microbial growth and interactions among taxa. The hypothesis that these soil aggregate fractions contain different eubacterial communities was tested using terminal restriction fragment length p...

Acid hydrolysis is used to fractionate the soil organic carbon pool into relatively slow- and fast-cycling compartments on soils from Arizona, the Great Plains states and Michigan collected for carbon isotope tracer studies related to soil carbon sequestration, for studies of shifts in C3/C4 vegetation, and for "pre-bomb" soil-carbon inventories. P...

Even modest temperature increases could cause large releases of CO2 from the soil; a one-degree temperature increase could prompt soil carbon losses (as CO2) equivalent to five times the annual CO2 release from all fossil fuel burning. But, such forecasts are based on short-term data that implicitly assume all of the carbon in the soil is uniformly...

Several chemical fractionation methods purport to isolate soil carbon that is biochemically resistant to decomposition. These fractions are often 1300-1500 years older than whole soil C. The standard model of soil carbon dynamics suggests that biochemcially resistant C should not be lost quickly upon cultivation or land use change, decompose rapidl...

Carbon (C) can be sequestered in the mineral soil after the conversion of intensively cropped agricultural fields to more extensive land uses such as afforested and natural succession ecosystems. Three land-use treatments from the long-term ecological research site at Kellogg biological station in Michigan were compared with a nearby deciduous fore...

In this study, we investigated the impact of cropping system management on C and N pools, crop yield, and N leaching in a long-term agronomic experiment in Southwest Michigan. Four management types, conventional (CO), integrated fertilizer (IF), integrated compost (IC), and transitional organic (TO) were applied to two crop sequences, a corn (Zea m...

Large-scale outbreaks of defoliating insects are common in temperate forests. These outbreaks are thought to be responsible for substantial cycling of nitrogen (N), and its loss from the system. Gypsy moth (Lymantria dispar) populations within poplar plots were manipulated over 2 years so that the ecosystem-wide consequences of catastrophic defolia...

Factors controlling soil organic matter (SOM) dynamics in soil C sequestration and N fertility were determined from multi-site analysis of long-term, crop rotation experiments in Western Canada. Analyses included bulk density, organic and inorganic C and N, particulate organic C (POM-C) and N (POM-N), and CO2-C evolved during laboratory incubation....

Soil organic nitrogen was quantified by solid-state 15N cross-polarization nuclear magnetic resonance spectroscopy (NMR) during a 14-month laboratory incubation of a sandy loam soil amended with 15N-clover. In whole soil and particle-size fractions, the clover-derived N was always 85–90% amide, 5–10% guanidinium N of arginine, and 5% amino. Quantit...

The hypothesis that soil light fraction and heavy fraction harbor distinct eubacterial communities and have differing numbers and sizes of bacterial cells was tested in three agronomic cropping systems. This hypothesis would imply that these soil fractions are distinct microbial habitats. Shoot residue and rhizosphere soil were also included in the...

Interpretation of soil organic C (SOC) dynamics depends heavily on analytical methods and management systems studied. Comparison of data from long-term corn (Zea mays)-plot soils in Eastern North America showed mean residence times (MRTs) of SOC determined by 14C dating were 176 times those measured with 13C abundance following a 30-yr replacement...

The uniformity, low cost and ease of application associated with inorganic fertilizers have diminished the use of organic nutrient sources. Concern for food safety, the environment and the need to dispose of animal and municipal wastes have focused attention on organic sources of N such as animal-derived amendments, green manures, and crop rotation...

Nitrification potential is the maximum capacity of a soil’s population of nitrifying bacteria to transform NH4+-N to NO3−-N. Time of season and the effect of several management practices on nitrification potentials were measured via an amended slurry method, shaken for 24 h at 25 °C. Management strategies that reduce potential nitrification rates w...

Management practices that influence the quantity of C inputs returned to the soil from cropping systems and compost applications alter subsequent biotic activity broadly, contribute to seasonal fluctuations in nutrient dynamics, and may increase C sequestration. The effects of crop rotations and compost applications on soil-C sequestration and deco...

We examined the impacts on U.S. agriculture of transient climate change assimulated by 2 global general circulation models focusing on the decades of the 2030s and 2090s. We examined historical shifts in the location of crops and trends in the variability of U.S. average crop yields, finding that non-climatic forces have likely dominated the north...

Terminal restriction fragment length polymorphism (T-RFLP) is a culture-independent method of obtaining a genetic fingerprint of the composition of a microbial community. Comparisons of the utility of different methods of (i) including peaks, (ii) computing the difference (or distance) between profiles, and (iii) performing statistical analysis wer...

Glomalin is a soil proteinaceous substance produced by arbuscular mycorrhizal fungi. Most of the information available concerning this protein has been collected in relation to its role in soil aggregation. In this study, we explored the distribution of glomalin across soil horizons, decomposition of glomalin, and relationship with soil C and N in...

Forested ecosystems have been identified as potential C sinks. However, the accuracy of measurement and understanding of the underlying mechanisms for soil organic C (SOC) storage in forested ecosystems needs to be improved. The objective of this study was to use aggregate and soil organic matter (SOM) fractionation techniques to identify SOC pools...

Giant congenital nevi involve an approximately 5% risk of malignant transformation. We report about a 27-year-old patient who developed malignant melanoma after radiation of a large congenital nevus of the foot which was initially misinterpreted as a trophic disorder. The mechanisms and probability of malignant transformation and prophylactic thera...

The design of sustainable N management strategies requires a better understanding of the processes influencing the ability of soils to supply N to a growing crop. Although commonly ignored, the release of C by plant roots may have a tremendous impact on soil organic matter turnover under certain soil conditions. The main objective of this study was...

Große kongenitale Naevi bringen ein ca. 5-prozentiges Risiko der malignen Entartung mit sich. Wir berichten über einen 27-jährigen Patienten, bei dem es nach einer Strahlentherapie eines angeborenen Naevus am Fuß zur Entstehung eines metastasierenden malignen Melanoms kam, das zunächst als trophische Störung missdeutet wurde. Es werden der Mechanis...

The relationship between soil structure and the ability of soil to stabilize soil organic matter (SOM) is a key element in soil C dynamics that has either been overlooked or treated in a cursory fashion when developing SOM models. The purpose of this paper is to review current knowledge of SOM dynamics within the framework of a newly proposed soil...

Highbush blueberries (Vaccinium corymbosum L.) are long lived perennial plants that are grown on acidic soils. The goal of this study was to determine how blueberry cultivation might influence the nitrification capacity of acidic soils by comparing the nitrification potential of blueberry soils to adjacent noncultivated forest soils. The net nitrif...

Information on the mean residence time (MRT) of soil organic carbon (SOC) on different soil types and management regimes is required for pedo-geological, agronomic, ecological and global change interpretations. This is best determined by carbon dating the total soil together with acid hydrolysis and carbon dating of the non-hydrolyzable residue (NH...

Large-scale outbreaks of defoliating insects are common in temperate forests. The effects of defoliation on tree physiology are expected to cascade through the entire forest ecosystem, altering carbon, nitrogen, and water fluxes, and subsequently affecting nitrogen cycling and plant-herbivore interactions. If these post-defoliation changes are larg...