Bulk Organic Matter Research Articles

Quantifying effects of root systems of planted and natural vegetation on rill detachment and erodibility of a loessial soil

The objectives of this study were to evaluate different root parameters for estimating rill detachment, and to compare and quantify the effectiveness of planted and natural vegetation on soil physical characteristics and in reducing rill detachment and erodibility. Laboratory-concentrated-flow flume tests were performed under a flow discharge of 3 L min−1 and a slope of 15° with intact soil samples. A silt loam soil (Calcic Cambisol, in Loess Plateau in China) was sampled in 2015 from laboratory with planted ryegrass (Lolium perenne L.) and in 2014 from natural vegetation fields under 12 to 36-a restoration. The results indicated that root length density was the best parameter for estimating the effects of roots on rill detachment and erodibility for both planted ryegrass and natural vegetation, with exponential reduction equations. The exponents were more negative for natural vegetation (−0.411) than for planted species (−0.217) because of the existence of more complex root networks under more diverse natural vegetation. Rill erodibility of soil samples with roots decreased exponentially from the baseline erodibility of the root-free soil as RLD increased. Root systems of the restored natural vegetation ameliorated soil characteristics (bulk density, aggregate stability and organic matter content) more profoundly than those of the laboratory tests due to stronger bonding and binding effects, resulting in a lower absolute soil detachment rate for a given root density. There existed a vertical decay distribution pattern of root densities with soil depth for natural vegetation and planted ryegrass, and this distribution of root systems reached a steady state after 12 years natural vegetation restoration. More vegetation types under more different hydraulic conditions should be evaluated in future studies to provide better scientific bases for modelling their impacts on rill detachment and erodibility.

Paleoenvironmental response of midlatitudinal wetlands to Paleocene–early Eocene climate change (Schöningen lignite deposits, Germany)

Abstract. The early Paleogene is marked by multiple negative carbon isotope excursions (CIEs) that reflect massive short-term carbon cycle perturbations that coincide with significant warming during a high-pCO2 world, affecting both marine and terrestrial ecosystems. Records of such hyperthermals from the marine–terrestrial interface (e.g., estuarine swamps and mire deposits) are therefore of great interest as their present-day counterparts are highly vulnerable to future climate and sea level change. Here, we assess paleoenvironmental changes of midlatitudinal late Paleocene–early Eocene peat mire records along the paleo-North Sea coast. We provide carbon isotope data of bulk organic matter (δ13CTOC), organic carbon content (%TOC), and palynological data from an extensive peat mire deposited at a midlatitudinal (ca. 41∘ N) coastal site (Schöningen, Germany). The δ13CTOC data show a carbon isotope excursion of −1.3 ‰ (mean decrease in δ13CTOC; −1.7 ‰ at the onset of CIE) coeval with a conspicuous Apectodinium acme. Due to the exceptionally large stratigraphic thickness of the CIE at Schöningen (10 m of section) we established a detailed palynological record that indicates only minor changes in paleovegetation leading into and during this event. Instead, paleovegetation changes mostly follow natural successions in response to changes along the marine–terrestrial interface. The available age constraints for the Schöningen Formation hamper a solid assignment of the detected CIE to a particular hyperthermal such as the Paleocene–Eocene Thermal Maximum (PETM) or any succeeding hyperthermal event such as the Eocene Thermal Maximum 2 (ETM2). Compared to other nearby peat mire records (Cobham, UK; Vasterival, F) it appears that wetland deposits around the Paleogene North Sea have a consistent CIE magnitude of ca. −1.3 ‰ in δ13CTOC. Moreover, the Schöningen record shares major characteristics with the Cobham Lignite PETM record, including evidence for increased fire activity prior to the CIE, minor plant species change during the hyperthermal, a reduced CIE in δ13CTOC, and drowning of the mire (marine ingressions) during much of the Schöningen CIE event. This suggests that either the Schöningen CIE reflects the PETM or that early Paleogene hyperthermals similarly affected paleoenvironmental conditions of a major segment of the paleo-North Sea coast.

Neogene vegetation shift in the Nepalese Siwalik, Himalayas: A compound‐specific isotopic study of lipid biomarkers

AbstractThe late Neogene vegetation change of C4 plants replacing C3 plants is widely documented across the world. This vegetation shift has been particularly well‐documented in the Himalayan foreland based on δ13C isotopic data from palaeosol carbonates and bulk organic matter in the Siwalik sedimentary rocks of Pakistan, India and Nepal, showing asynchronous expansion of C4 plants between 8 and ~5 Ma, 9 and 6 Ma, and around 7 Ma, respectively. In this study, compound‐specific isotopic analysis of lipid biomarkers extracted from shale and palaeosols in the palaeomagnetically age‐constrained Nepalese Siwalik is utilized to better understand this vegetation shift. This is the first comprehensive lipid biomarker study in the Nepalese Siwalik, with new isotopic results from the previously undocumented Karnali River section. The δ13C n‐alkane (C27‐31) results from the Surai Khola section suggest C3 plants were dominant between 12 and 8.5 Ma. A stepwise expansion of C4 plants that started gradually at 8.5 Ma escalated rapidly after 5.4 Ma, so that by 5.2 Ma C4 vegetation dominated the landscape. This dramatic ecological shift at the Miocene‐Pliocene boundary was likely linked with an intriguing tectonic‐climate coupling in the Himalayan‐Tibetan region, prompting wetter summers and drier winters that drove C4 grass expansion. However, in the Karnali River section, the data show no clear sign of C4 plant expansion until 5.2 Ma (youngest sample age). In the two study locations separated laterally by ~200 km along tectonic‐strike, this different trend of vegetation change likely indicates local controls like river‐catchment influence. However, it is possible that, similar to the Surai Khola section, C4 plants dominated after 5.2 Ma in the Karnali River section. This study also suggests that the past vegetation makeup of an area is better reconstructed using isotopic signatures of molecular markers than of bulk organic matter or pedogenic nodules.

Resource recovery from digested manure centrate: Comparison between conventional and aquaporin thin-film composite forward osmosis membranes

We compared the performance of conventional and aquaporin thin-film composite forward osmosis (FO) membranes (denoted as HTI and AQP membrane, respectively) for concentration of digested manure centrate. Results show that the two FO membranes were capable to concentrate digested centrate for resource recovery. During concentration of digested manure centrate, a cohesive fouling layer formed on the HTI membrane surface, resulting in more dramatic flux decline and less fouling reversibility in comparison to the AQP membrane. The two FO membranes exhibited effective and comparable rejection of bulk organic matter, total phosphorus, and heavy metals, leading to their notable enrichment in digested manure centrate. By contrast, ammonium nitrogen (NH4+-N) was only retained by approximately 40% using the two FO membranes with a slightly higher retention by the HTI membrane, since it was less negatively charged. As a result, total nitrogen was ineffectively rejected by the two FO membranes. It is noteworthy that the HTI membrane also contributed to higher rejection of most antibiotics than the AQP membrane, possibly due to enhanced retention by the fouling layer and retarded forward diffusion. Results from this study evidence the outperformance of the AQP membrane as a new generation FO membrane over its conventional counterpart with respect to antifouling property, while further improvement in membrane selectivity, particularly of monovalent cations (e.g. NH4+-N), is needed to advance FO applications in resource recovery from challenging waste streams.

Late-Holocene sedimentation and sodium carbonate deposition in hypersaline, alkaline Nasikie Engida, southern Kenya Rift Valley

Continental rift systems are often characterized by geothermal activity and associated discharge of hot groundwater, which can substantially impact the water, solute and sediment budgets of rift-valley lakes. Hot-spring inflow can result in complex lake hydro- and geochemistry, but also buffers against the desiccation of closed-basin lakes in dry climate regimes. Consequently, hydrothermally fed lakes can potentially provide continuous sedimentary records from regions where other types of paleoenvironmental archives are lacking. This is illustrated by Nasikie Engida, a shallow hypersaline and alkaline (soda) lake in the semiarid Rift Valley of southern Kenya. Here, inflow of hot-spring water has maintained a shallow but permanent water body and continuous deposition of sediments through past climate episodes when many other lakes in the eastern (Gregory) branch of the East African Rift System stood dry. We present the first data on late-Holocene sedimentation in this remarkable lacustrine system, typified by authigenic nahcolite [NaH(CO3)] formation during part of its recorded history. Our data include measurements of bulk-sediment and mineralogical composition, clastic-mineral grain size and magnetic susceptibility. Analytical issues related to the large amount of salts within the sediments, both as crystals and in solution in the pore water, are discussed. We also present exploratory time series of the stable-isotope composition of bulk organic matter and authigenic nahcolite. Core lithostratigraphy and preliminary radiocarbon dating indicate that Nasikie Engida has accumulated finely laminated sediments continuously since ca. 2850 cal year BP, which is remarkable given its current maximum depth of only 1.6 m. Synsedimentary nahcolite appears abruptly ~ 2260 cal year BP and since then has been deposited regularly, in the form of distinct pure layers up to several cm thick. Its formation has been enabled by high pCO2, supplied principally from geothermal sources, accumulating in a high-density brine. Although Nasikie Engida has likely been saline over the entire time span covered by the studied sediment sequence, variation in nahcolite deposition and bulk-sediment composition suggests multi-decadal to centennial oscillations in water-column stability and stream inflow driven by variation in climatic moisture balance. Further analyses of this paleoenvironmental archive may thus produce the first continuous climate-proxy record from a vast dry region of equatorial East Africa. Moreover, Nasikie Engida’s extraordinary setting makes it a unique modern analogue for the interpretation of ancient nahcolite-bearing salt-lake deposits.

Evaluation of Heavy Metals Content in Simulated Solid Waste Food Compost

Composting is one of the solid waste management (SWM) methods where the organic component decomposed biologically under controlled conditions. In this study, a 0.166 m3 bioreactor tank was designed to compose 59.2Kg of simulated common municipal solid food waste having a bulk density, organic matter, organic carbon, pH, nitrogen content, C/N and nitrification index (NH4-N/ NO3-N) of 536.62 kg/m3, 62.34%, 34.76%, 6.53, 1.86%, 23 and 0.34 respectively. The bioreactor operated aerobically for 30 days, and anaerobically for 70 days, until the end of the composting process. Results proved that the composting process could reduce the mass of the waste by 69%. Nitrogen content, C/N, nitrification index, NPK, and germination index (GI) were found to be 1.52%, 14.54, 0.31, 1.52%, 1.53%,0.85 % and 85.5% indicating that the obtained compost is stable and mature according to the standards. Twelve heavy metals of Zinc (Zn), Cupper (Cu), Molybdenum (Mo), Zirconium (Zr), Strontium (Sr), Rubidium (Rb), Manganese (Mn), Scandium (Sc), Iron (Fe), Titanium (Ti), Calcium (Ca) and Potassium (K) were detected by using Niton (XRF) device. Results of Cu and Zn were within the limits of the standards, while the rest were considered acceptable as standards did not restrict them.

Organotin compounds in touristic marinas of the northern Adriatic Sea: occurrence, speciation and potential recycling at the sediment-water interface.

Butyltin compound (BTC) contamination was evaluated in two north Adriatic marinas, San Rocco (Italy) and Lucija (Slovenia). BTC sedimentary concentrations (121 ± 46 and 352 ± 30 ng Sn g-1 in San Rocco and Lucija, respectively) evidenced the past use of antifouling paints, confirmed by the reduced tributyltin content (~ 46%) with respect to the sum of BTC. Elemental and organic carbon isotopic (δ13C) analyses of bulk sediments and its lipid and humic substances were performed in order to evaluate their role in BTC partitioning and preservation. The δ13C of sedimentary bulk and refractory organic matter suggested that diagenetic processes could play a role in the preservation or release of pollutants. No contamination was found in water collected from the benthic chamber and thus, fluxes at the sediment-water interface were not assessed, except for MBT efflux at Lucija (28.9 ng Sn m-2 day-1). Nevertheless, BTC concentrations in porewaters (up to 75 ng Sn l-1) and rather low sediment-porewater partitioning coefficients (Kd) with respect to the data reported in the literature would suggest a potential risk of the reintroduction of BTC into the water column at both sites: at Lucija, sedimentary contamination is high despite the greater Log Kd, whilst at San Rocco, the low BTC concentration is associated with a reduced sediment affinity.

The organic signature of an experimental meat-cooking fireplace: The identification of nitrogen compounds and their archaeological potential

A better understanding of the operation and use of prehistoric fires is fundamental to interpreting the organization of living spaces. Following a previous study that focused on the organic signatures of fireplaces fueled with wood and/or bones, this study targeted the completion of an experimental reference database through the addition of a wood-fueled fireplace dedicated to the cooking of meat. Different sedimentary features of this experimental fireplace were visually identified (e.g. darkening, reddening), sampled, and subjected to geochemical analysis. Corg and N contents were quantified, samples were extracted with organic solvents and analyzed through GC–MS and bulk organic matter was characterized through py(TMAH)-GC–MS. Five different samples were studied and compared with a control sample, representative of the local background. A significant increase of Corg and N contents was measured for the three samples presenting darkened or charred caracteristics. The meat-cooking fireplace seems to be characterized by the strong contribution of nitrogen, which was visible in elementary analyses as well as in the molecular composition of solvent extracts, and bulk organic matter. More specifically, compounds containing nitrile functions, amides, N-heterocyclic and N-aromatic compounds could be detected in solvent extracts. Amines, amides, N-heterocyclic and N-aromatic compounds could be identified in py(TMAH)-GC–MS. Some of these compounds present a relative stability in soils and could therefore aid in our comprehension and functional interpretations of archaeological fireplaces, and may, more particularly, make it possible to highlight the use of fireplaces for the cooking of meat.

Soil detachment by overland flow on hillslopes with permanent gullies in the Granite area of southeast China

Permanent gullies are often initiated from rill erosion, followed by the formation of abrupt, deep and wide gullies when topsoil and subsoil are carried away by fast-flowing surface water. Few studies have been performed to evaluate soil detachment processes on hillslopes with permanent gullies, which may significantly affect the further development of gully erosion. Soil detachment was investigated by using natural undisturbed soil samples collected in different spatial locations (upper catchment, middle slope, lower slope, and scour channel) of hillslopes with permanent gullies. The relationships of soil detachment capacity with soil property, root system, and hydraulic parameters were quantified. Selected samples were tested in a hydraulic flume (3.8 m length × 0.2 m width) under five different shear stresses (3.67, 7.81, 10.50, 13.97 and 17.28 Pa). Soil detachment capacity was found to be significantly greater in the scour channel than in the other three hillslope positions. For the initial and stable gullies, the soil detachment capacity was notably reduced in the middle slope relative to the upper catchment and lower slope, while a different trend was observed in the active gully. The variability of soil detachment capacity at different spatial locations showed a negative correlation to bulk density, soil cohesion, clay, organic matter, and root density (P < 0.05), and a positive correlation to total porosity (P < 0.01). The rill erodibility (Kr) showed a power function decrease with soil bulk density, organic matter, and root density (P < 0.01). Critical shear stress (τc) had a significant and positive correlation with soil cohesion. Based on the WEPP model, detachment capacity of soil on hillslopes with permanent gullies could be achieved by using measurable parameters such of shear stress, bulk density, organic matter, root density, and soil cohesion.

Alfalfa planting significantly improved alpine soil water infiltrability in the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau is undergoing serious water and soil conservation problem resulted from grassland degradation, that is not conductive to the sustainability of grassland ecologicla function and agriculture productivity. The soil infiltrability has significance in reducing runoff yield and soil loss. However, characterization of the soil infiltration capacity of planted grasslands, such as alfalfa (Medicago Sativa), with different growing years in this high-altitude alpine region is still lacking. In this study, the variation of soil infiltration rate and characteristics were analyzed in alfalfa grasslands with three growth years (two-, four- and seven-year-old). A corn cropland was used as the control field, and the infiltration was monitored using the automatic soil infiltrability measurement system. To determine the influence factors on infiltration rate (IR), soil characteristics and root dry weight density (RDWD) at 0–30 cm soil depth were measured. The results indicated that the comprehensive index of soil water infiltration capacity (FIR) of the seven-year-old alfalfa grassland (0.69) was the highest, followed by the two- (0.05) and four-year-old (0.11) grasslands, being these values significantly higher than that of the corn field (-0.85, P < 0.05). SWC was positively correlated with IR during the fast infiltration stage (IR-I). The soil bulk density and organic matter were negatively correlated with IR, while RDWD was positively related to IR. Our results showed that alfalfa planting improved soil infiltrability, and this upgrade increased with the age growth. This study provided significant information to introduce soil-erosion-control practices for alpine soil and highlights the importance of ecological function of planted grasslands in alpine area of the Qinghai-Tibetan Plateau.

Diatom-inferred ecological responses of an oceanic lake system to volcanism and anthropogenic perturbations since 1290 CE

The impacts of natural- and human-induced processes on lake ecosystems in remote oceanic islands remain to be fully elucidated. These lakes are excellent candidates to analyze the importance of anthropogenic vs. natural forces driving lacustrine long-term ecological evolution from previous pristine pre-colonized conditions. Disentangling the effects of both is particularly relevant in highly active volcanic areas, where catastrophic eruptions can act as an atypical natural driver altering the lake's long-term ecological trajectories. In this paper we study past ecological changes occurring in Lake Azul (São Miguel island), a crater lake from the remote Azorean archipelago, to address which were the main causes of its long-term trophic history. We analyzed diatom assemblages, sedimentology, and bulk organic matter of sediments deposited since ca. 1290 CE, when a huge local eruption occurred. This episode drove the evolution of Lake Azul through six distinct phases, commencing with a restart of ecological succession after tephra deposition disrupted biogeochemical cycling. The alteration was so profound that the lake underwent a state of oligotrophic conditions for approx. 650 yr. Nutrients were sourced by fish-induced internal recycling and the overflow of the near Lake Verde during this period, rather than by allochthonous nutrient inputs modulated by climate variability and/or vegetation cover changes in the watershed after the official Portuguese colonization. It was only after recent artificial fertilization when the system overcame the volcanic-induced long-term resilience. This over-fertilization and a reduction in water turnover exacerbated the recent symptoms of eutrophication after 1990 CE. Contrary to other studies, Lake Azul constitutes an uncommon case of long-term resilience to trophic change induced by a cataclysmic volcanic eruption. It brings new insights into the fate of lake ecosystems which might be affected by similar events in the future.

Comparison of different approaches for estimating soil water characteristic curves from saturation to oven dryness

Three approaches were compared for estimating continuous soil water characteristic curves (SWCCs) from easily accessible soil properties. The approaches included combining the Mohammadi and Vanclooster (2011) method (the MV method) with the van Genuchten (1980) model (MV-vG approach), the modified MV-vG approach, and combining the Jensen et al. (2015) method with the Fredlund and Xing (1994) model (the J-FX approach). A total of 195 disturbed soil samples and 195 undisturbed soil cores were collected from 1-m soil profiles in an arid region of northwestern China. Particle size distribution (PSD) and organic matter (OM) content were determined. The volumetric water content and matric potential data pairs of each sample during the drying process were measured using a high speed centrifuge. All of the measured soil properties were used to evaluate the applicability of the approaches for continuous SWCC estimation. The MV method has a robust physical basis and is independent of any experimental SWCC data pairs. Some intrinsic shortcomings affect the estimation of continuous SWCC by the MV-vG approach. The integration of a soil structure feature improved the estimation of the modified MV-vG approach. The estimation of the J-FX approach for SWCC is robust for the five textural classes, and outperformed the MV-vG approach and the modified MV-vG approach. The good performance of the J-FX approach can be attributed in part to the fact that it distinguishes the dominant forces governing water retention of dry and wet ranges, and relates the PSD, specific surface area, and OM content to the pore size distribution. All these factors are vital for soil water retention, but have been simplified or ignored by the MV method. Both the modified MV-vG approach and the J-FX approach are promising for estimating continuous SWCCs at a regional scale. The modified MV-vG approach may be suitable for rigid soils with medium textures at potentials above wilting point. The J-FX approach is applicable for the whole range of water retention from saturation to oven dryness for soils with substantially varying bulk density, soil texture and organic matter content at a regional scale. The results of this study are fundamental for use in simulating the transfer of water and solutes in layered-structured soil profiles and for estimating the vegetation carrying capacity of soil available water in arid regions.

Marsh edge erosion and associated carbon dynamics in coastal Louisiana: A proxy for future wetland-dominated coastlines world-wide

Coastal wetland loss through marsh edge erosion is a serious problem in Louisiana. The majority of studies on coastal land loss use aerial and satellite photographic analysis while field and site-specific measurements are limited. The aim of this study was to spatially and temporally measure coastal marsh edge erosion and investigate factors responsible for differences in erosion including shoreline orientation, soil physio-chemical properties, and wind speed and duration. A total of 33 transects across six island sites in northern Barataria Basin, Louisiana were established. Transects on shorelines facing different compass directions were measured for erosion for up to 2 years. Soils were analyzed for physiochemical properties including bulk density, organic matter, total carbon, nitrogen, and phosphorus. Bathymetric surveys were conducted to determine the extent of the erosive bay bottom profile. In addition, 14C dating of the basal organic matter (1.5–1.6 m) was conducted. Erosion rates ranged from 49.27 to 324.85 cm y-1 with a mean value of 141.69 ± 22.45 cm y−1. As expected, erosion rates were significantly different (p < 0.001) between protected and unprotected sites. The erosion rate was not correlated with wind speed (r = -0.07), weakly correlated with compass direction of shoreline (r = 0.25) and water level (r = 0.25) but strongly correlated with duration of wind (r = 0.60). Erosion rate was negatively correlated (r = -0.45) with bulk density and positively correlated with organic matter content (r = 0.42) of the top 40 cm of the soil. Over time, the marsh is eroded down to a depth of 1.5 m, which correlates to annual loss of 1.82 ± 0.29 m3 volume of marsh per meter shoreline length including a loss of organic matter (141.5 ± 22.55 kg m−1) and carbon (63.32 ± 10.09 kg m−1) previously preserved for up to 850 years. As a consequence, annual CO2 emissions for Barataria Basin were estimated to be 1.56 ± 0.26 million tCO2e y−1. Results can inform coastal managers as to the most vulnerable marshes to target restoration efforts. Due to high relative sea level rise in coastal Louisiana, these results can also be used to inform the world's stable coastlines on the relative vulnerability of their coastal marshes in the near future, due to projected eustatic sea level. Consequently, the eroding coastlines across the globe may be a significant source of CO2 emissions in near future, as millennial age stored soil carbon is released in a relatively short time, potentially overwhelming human efforts to slow rising atmospheric CO2 levels.

Stable Isotope Constraints on Marine Productivity Across the Cretaceous‐Paleogene Mass Extinction

AbstractThe effects of the Cretaceous‐Paleogene (K/Pg) mass extinction (~66 Ma) on marine primary and export productivity remain debated. We studied changes in carbon and nitrogen cycling in eight neritic and upper bathyal sections with expanded K/Pg boundary clay layers in the western Tethys and northeastern Atlantic Ocean, by measuring stable carbon isotopes of bulk carbonate (δ13Ccarb) and organic matter (δ13Corg), nitrogen isotopes in bulk organic matter (δ15N), and selected compound‐specific carbon isotopic records (δ13Clipid). Negative carbon isotope excursions (CIEs) in δ13Ccarb, δ13Corg,and δ13Clipidare temporally and spatially heterogeneous as well as decoupled from each other, suggesting that factors affecting the δ13C of dissolved inorganic carbon, as well as isotopic fractionation during carbon fixation across the K/Pg, are more complex than commonly assumed. The negative CIEs in δ13Corgand δ13Clipidat each site are smaller in amplitude and shorter in duration than those in δ13Ccarb, but in most sections both carbon pools recovered to preboundary conditions within the time of deposition of the boundary clay layer (&lt;103–104Kyr) or shortly thereafter. This rapid recovery is supported by limited δ15N data, which mostly suggests moderate or minor changes in redox conditions (except in Denmark), marine productivity, and phytoplanktonic nitrate utilization in the earliest Danian. Our results indicate that carbon cycling and primary productivity in neritic and upper bathyal regions recovered to preboundary levels faster (&lt;104Kyr) than in oceanic regions (105–106years), likely sustained by resilient noncalcifying phytoplankton with resting stages, consistent with modeling and proxy studies.

Effects of the Physicochemical Properties of Lignocellulosic Artificial Soil Containing Bacillus subtilis on the Growth of Lespedeza cyrtobotrya

In this study, we prepared lignocellulosic artificial soil that contains Bacillus subtilis (peat moss/perlite/ steam-exploded oak wood/microbial culture = 3:1:3:3, w/w/w/w) for use in the restoration of damaged soil areas. The prepared lignocellulosic artificial soil was mixed with soil at ratios of 0%, 25%, 50%, 75%, and 100%. These mixed soils were then applied to fields, and the resultant physicochemical properties and their effects on the plant growth of Lespedeza cyrtobotrya were observed. The mixture of the prepared artificial soils (mixed at ratios of 25%–100%) with soil had a bulk densities of &lt;0.04 g/cm3, porosities of &gt;85%, pH values between 4.3 and 4.7, electrical conductivities of &lt;0.5 dS/m, C/N ratios between 15.0 and 26.5, organic matter content between 23.6% and 43.2%, and bacterial densities between 157 × 106 and 624 × 106 CFU/g. In addition, the prepared artificial soils mixed with soil at ratios of 25%–50% exhibited higher plant growth rates for L. cyrtobotrya compared with the control. Overall, we identified positive correlations between the plant growth of L. cyrtobotrya and soil bulk density, porosity, water-holding capacity, C/N ratio, organic matter, and bacterial densities.

Comparing carbon accumulation in restored and natural wetland soils of coastal Louisiana

Louisiana's chronic wetland deterioration has resulted in massive soil organic matter loss and subsequent carbon release through oxidation. To combat these losses, and reestablish ecosystem function, goods, and services, many restoration projects have been constructed or planned throughout coastal Louisiana. There are significant data gaps and conflicting results regarding wetland contributions to global warming, especially related to carbon sequestration in restored wetlands. An exceptionally large data set was used to derive carbon accumulation rates from key soil characteristics and processes. Assessments and comparisons of bulk density, organic matter, total carbon, vertical accretion (short- and longer-term), and carbon accumulation rates were made across time (chronosequence) and space (i.e., coastwide, watershed basins, and vegetation zones). Carbon accumulation rates in the Louisiana coastal zone were generally correlated to hydrogeomorphology, with higher rates occurring in zones of high river connectivity or in swamp or higher salinity tolerant marsh. On average, naturally occurring wetlands had higher carbon accumulation rates than restoration sites. Although some restoration measures were higher, and most showed increasing carbon accumulation rates over time. Results demonstrate that although wetland restoration provides many ecosystem benefits, the associated carbon sequestration may also provide useful measures for climate change management.

Composted Sugarcane By-product Press Mud Cake Supports Wheat Growth and Improves Soil Properties

Restoring soil fertility is essential to sustain crop production in order to meet the needs of the ever-blooming population. In this light, the present investigation was conducted on the same soil for two consecutive years (2014–2015 and 2015–2016) in Punjab, Pakistan, to determine the influence of press mud compost (PMC) and mineral fertilizers (NPK) on wheat growth, yield and soil properties. The experiment was composed of an unfertilized control and five inter-exchanging combinations of NPK and PMC (100:0, 75:25, 50:50, 25:75, 0:100). 100% PMC (900 kg ha−1) was intermediate in wheat growth and yield between unfertilized and 100% NPK, this latter being the recommended dose of mineral nutrients (120, 100 and 60 kg ha−1 of the respective N, P2O5, and K2O). The 50:50 combination of NPK and PMC determined the best growth and final yield (+ 19% vs. 100% NPK), despite an approximately 40% lower nutrient supply with respect to 100% NPK. Soil traits bulk density, pH, organic matter, total N, and available nutrients P and K significantly improved with 100% PMC. Based on the ANOVA, the 50:50 combination of NPK and PMC was no worse than 100% PMC in bulk density, available P and K, and it was a good compromise between 100% NPK and 100% PMC in organic matter content. Therefore, conjunctive use of PMC and NPK fertilizers appeared a good choice to improve wheat productivity and soil properties. Additionally, the use of PMC will lower the reliance on mineral fertilizers while restoring soil fertility and assuring environmental protection.

Bulk density and organic carbon contents of soil pedons influenced by different tree species

Abstract. Bulk density and organic matter content of soil are important soil attributes used in predicting the productivity potentials of soil and overall soil quality. The distribution of soils bulk density and organic carbon in horizons of soil pedons under different three tree species (Hevea brasiliensis – rubber, Pentaclethra macrophylla – oil bean and Irvingia gabonensis – ogbono) in Owerri, Southeastern Nigeria were investigated. A random survey method was used in field sampling. In all, three profile pits were dug, one in each site. A total of 36 soil samples were collected and analyzed for the study. Samples were collected at different horizon levels (A, AB, Bt1 and Bt2). Three representative samples were collected from each horizon. Bulk density, organic carbon and other routine analyses were performed using routine laboratory techniques. Mean, coefficient of variation and correlation analyses were analyzed. From the results obtained bulk density increased with depth, ranging from 1.05-1.81 g cm-3 in the rubber plantation, 1.02-1.70 g cm-3 in ogbono plantation and 1.11-1.57 g cm-3 in oil bean plantation. Bulk density decreased with the increase the organic carbon content. However, mean bulk density values irrespective of tree species did not exceed critical limits ranging from 1.28 to 1.32 g cm-3 as appropriate. Organic carbon ranged from 0.06-0.89 g kg-1 in rubber plantation, 0.42-0.87 g kg-1 in ogbono plantation and 0.72-1.25 g kg-1 in oil bean plantation. The epipedal horizons contained higher organic carbon than the endo-pedal horizons. The average organic carbon contents of the pedons were lower than the critical value irrespective of the tree species. The oil bean plantation had higher organic carbon and total nitrogen than the ogbono and rubber plantation while the ogbono plantation contained higher available phosphorus than the other two plantations studied.

Initiation and Development of Wetlands in Southern Florida Karst Landscape Associated With Accumulation of Organic Matter and Vegetation Evolution

AbstractBiological processes exert important controls on geomorphic evolution of karst landscapes because carbonate mineral dissolution can be augmented and spatially focused by production of CO2 and biogenic acids from organic matter (OM) decomposition. In Big Cypress National Preserve in southwest Florida, depressional wetlands (called cypress domes) dissolved into surface‐exposed carbonate rocks and exhibit regular patterning (size, depth, and spacing) within the pine upland mosaic. To understand when wetland basins began to form and the role of spatially varying OM decomposition on bedrock weathering, we constructed age profiles of sediment accretion using compound‐specific radiocarbon analysis of long‐chain fatty acids and measured bulk OM properties and biomarker proxies (fatty acids and lignin phenols) in different zones (center vs. edge) of the wetlands. Based on compound‐specific radiocarbon analysis, landscape patterning likely began in the middle to late Holocene, with wetlands beginning to form earlier at higher elevations than at lower elevations within the regional landscape. Dominant vegetation appears to have shifted from graminoids to woody plants around 3,000 calendar years before the present, as reflected in downcore bulk carbon isotope data and lignin concentration, likely from increased precipitation and hydroperiods. OM is mostly accumulated in wetland centers, and wetland centers exhibit more carbonate dissolution due to inundation limiting atmospheric ventilation of CO2. Landscape development and patterning thus arise from interactions between hydrology, ecology, and ecological community evolution that control carbonate mineral dissolution.

Latitudinal variations in &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;30&amp;lt;/sup&amp;gt;Si and &amp;lt;i&amp;gt;δ&amp;lt;/i&amp;gt;&amp;lt;sup&amp;gt;15&amp;lt;/sup&amp;gt;N signatures along the Peruvian shelf: quantifying the effects of nutrient utilization versus denitrification over the past 600 years

Abstract. The stable sedimentary nitrogen isotope compositions of bulk organic matter (δ15Nbulk) and the silicon isotope composition of diatoms (δ30SiBSi) both mainly reflect the degree of past nutrient utilization by primary producers. However, in ocean areas where anoxic and suboxic conditions prevail, the δ15Nbulk signal ultimately recorded within the sediments is also influenced by water column denitrification, causing an increase in the subsurface δ15N signature of dissolved nitrate (δ15NO3-) upwelled to the surface. Such conditions are found in the oxygen minimum zone off the coast of Peru, where, at present, an increase in subsurface δ15NO3- from north to south along the shelf is observed due to ongoing denitrification within the poleward-flowing subsurface waters, while the δ30Si signature of silicic acid (δ30Si(OH)4) at the same time remains unchanged. Here, we present three new δ30SiBSi records between 11 and 15∘ S and compare these to previously published δ30SiBSi and δ15Nbulk records from Peru covering the past 600 years. We present a new approach to calculate past subsurface δ15NO3- signatures based on the direct comparison of δ30SiBSi and δ15Nbulk signatures at a latitudinal resolution for different time periods. Our results show that, during the Current Warm Period (CWP, since 1800 CE) and prior short-term arid events, source water δ15NO3- compositions have been close to modern values, increasing southward from 7 to 10 ‰ (between 11 and 15∘ S). In contrast, during the Little Ice Age (LIA) we calculate low δ15NO3- values between 6 ‰ and 7.5 ‰. Furthermore, the direct δ30SiBSi versus δ15Nbulk comparison also enables us to relate the short-term variability in both isotope compositions to changes in the ratio of nutrients (NO3-:Si(OH)4) taken up by different dominating phytoplankton groups (diatoms and non-siliceous phytoplankton) under the variable climatic conditions of the past 600 years. Accordingly, we estimate a shift from a 1:1 (or 1:2) ratio during the CWP and a 2:1 (up to 15:1) ratio during the LIA, associated with a shift from overall high nutrient utilization to NO3--dominated (and thus non-siliceous phytoplankton) utilization.