Soil Nutrient Dynamics Research Articles

Plant mycorrhizal associations mediate the zoogeochemical effects of calving subsidies by a forest ungulate.

Animals interact with and impact ecosystem biogeochemical cycling-processes known as zoogeochemistry. While the deposition of various animal materials (e.g. carcasses and faeces) has been shown to create nutrient hotspots and alter nutrient cycling and storage, the inputs from parturition (i.e. calving) have yet to be explored. We examine the effects of ungulate parturition, which often occurs synchronously during spring green-up and therefore aligns with increased plant nitrogen demand in temperate biomes. Impacts of zoogeochemical inputs are likely context-dependent, where differences in material quality, quantity and the system of deposition modulate their impacts. Plant mycorrhizal associations, especially, create different nutrient-availability contexts, which can modify the effects of nutrient inputs. We, therefore, hypothesize that mycorrhizal associations modulate the consequences of parturition on soil nutrient dynamics and nitrogen pools. We established experimental plots that explore the potential of two kinds of zoogeochemical inputs deposited at ungulate parturition (placenta and natal fluid) in forest microsites dominated by either ericoid mycorrhizal (ErM) or ectomycorrhizal (EcM) plants. We assess how these inputs affect rates of nutrient cycling and nitrogen content in various ecosystem pools, using isotope tracers to track the fate of nitrogen inputs into plant and soil pools. Parturition treatments accelerate nutrient cycling processes and increase nitrogen contents in the plant leaf, stem and fine root pools. The ecosystem context strongly modulates these effects. Microsites dominated by ErM plants mute parturition treatment impacts on most nutrient cycling processes and plant pools. Both plant-fungal associations are, however, equally efficient at retaining nitrogen, although retention of nitrogen in the parturition treatment plots was more than two times lower than in control plots. Our results highlight the potential importance of previously unexamined nitrogen inputs from animal inputs, such as those from parturition, in contributing to fine-scale heterogeneity in nutrient cycling and availability. Animal inputs should therefore be considered, along with their interactions with plant mycorrhizal associations, in terms of how zoogeochemical dynamics collectively affect nutrient heterogeneity in ecosystems.

Human-induced land use changes and phosphorus limitation affect soil microbial biomass and ecosystem stoichiometry.

Soil and microbial biomass carbon (C), nitrogen (N), and phosphorus (P) play an important role in soil nutrient dynamics in biogeochemical cycles of terrestrial ecosystems. However, increased human activities as a result of agricultural intensification on soil nutrients and microbial C:N:P stoichiometry are poorly understood in this fragile forest-savanna transition agroecosystem. This study aimed to (i) assess soil and microbial C, N, and P stoichiometry in different land use systems, and (ii) examine the effect of soil and microbial C, N, and P stoichiometry on soils susceptible to human-induced land use changes. A total of 82 composite soil samples at a depth of 0-20 cm were sampled from forest, savanna, grassland, fallow and cropland for laboratory analysis. The results revealed that the concentrations of C, N, and P were low in Fallow and Cropland compared to other land use systems. Analysis of variance in microbial C, N, and P stoichiometric ratios revealed a significant decreasing tendency compared to soil C:N, C:P and N:P ratios with no statistical significance (p < 0.05). The C:P and N:P ratios were low compared to the C:N ratio in land uses. A significant positive correlation was observed between MBC and MBN (0.95; p < 0.01), and with C and N (0.69; p < 0.01). There were significant interactive effects of land use on soil and microbial variables. The estimated microbial C:N:P stoichiometric ratios (21:2:1) were well constrained in the study area. The transition from Forest to Cropland resulted in 64%, 52%, and 71% reduction in C, N, and P, respectively. This implies that phosphorus is the main factor limiting productivity. The low availability of phosphorus in these tropical soils may have resulted in low C:P and N:P ratios. Therefore, we conclude that our results highlight the importance of phosphorus limitation on ratios of microbial C:P and N:P in landuse systems. Nutrient inputs such as fertilizers, manure and crop residues should be applied to croplands to improve soil and microbial C, N and P levels. Further, effects of land use on soil nutrient status and stoichiometry at 1-meter depth will be considered in our future work.

Effect of fertigation on nutrient dynamics of gray-brown soils and apple (Malus pumila) yields in intensive orchards of Kazakhstan

Over the past 13 years, drip irrigation in intensive orchards has gained popularity in southern Kazakhstan. However, its impact on soil has not been studied before. Our research group conducted experiments from 2019 to 2022 in intensive orchards to study the dynamics of fertigation, the application of fertilizers through irrigation water, on soil nutrient levels. Experiments were conducted in Southern Kazakhstan at "Kentau" LLP on intensive orchards with a planting scheme of 0.8*3.5m from 2019 to 2022 with the aim of determining the dynamics of the impact of fertigation on the content of available nutrient elements in the soil. The effectiveness of traditional root feeding method was compared with fertigation (drip application of mother liquor) on large areas of 136.5 hectares in laboratories at the Kazakh National Agrarian Research University and the Laboratory of TOO "KosAgroKommertz". Results showed that proper calculation of fertilizer doses for fertigation resulted in cyclic changes in soil nutrient levels (up to 23%), depending on the season and phenological phase of apple trees. The correlation between fruit quality and quantity was influenced by timing and assimilability of nutrients and method of application. Implementation of recommended fertilization methods resulted in increased yield, although the young age of some orchards may have contributed to the results. Under optimal nutrient management plans, nutrient levels in the soil showed noticeable fluctuations depending on the phenological phases of apple trees, which can be used to adjust fertigation practices. The study also revealed that fertigation can affect soil properties such as bulk density, soil density, and humus content, with potential long-term implications for soil health and fertility. In conclusion, fertigation significantly impacts soil nutrient levels in intensive orchards in southern Kazakhstan, and careful management of fertilizer doses and application timing is crucial for maximizing its effectiveness. Further research is needed to understand the long-term effects of fertigation on soil health and fertility, and its implications for sustainable agriculture practices. The findings contribute to knowledge on fertigation dynamics in Kazakhstan, serving as a basis for further studies and practical applications in agricultural management.

Dung beetles diversity and their role in nutrient cycling in livestock systems of the dry Chaco

Dung beetles represent one of the main animal groups involved in the cycling of cattle dung, modifying soil physicochemical properties, and reducing parasite incidence. However, their diversity and activity in cattle areas depends on conserving critical resources and conditions, including native vegetative composition, microclimatic and soil conditions. Whereas most previous studies were conducted in humid forests, our objective was to experimentally study the diversity and role of dung beetles in soil nutrient dynamics in native forests and shrub savannas with cattle ranching in the dry Chaco of Argentina. Using pitfall traps, we collected dung beetles in both habitats. In cow exclusions, we buried two plastic containers filled with soil and two kg of fresh cow dung on the surface and covered one with a mosquito net to prevent the access of dung beetles. After three months, we collected soil samples and analyzed nutrient contents and soil structure. Contrary to previous studies, the abundance and richness of dung beetles were higher in savannas than in native forests. In both habitats, the activity of dung beetles strongly increases phosphorous and potassium contents; however, consistent with the higher abundance, this effect was more marked in shrub savannas. In addition, we observed higher contents of total organic carbon, electrical conductivity, and calcium in native forests. Our results emphasize the critical role of dung beetles in maintaining soil quality in the most extended cattle management practices of the dry Chaco. Moreover, our results were opposite to previous studies conducted in humid forests, which could be associated with greater tolerance of native species to extreme microclimate conditions in the dry Chaco.

Composition, distribution, health risks, and drivers of phthalates in typical red paddy soils.

The accelerated accumulation of phthalate esters (PAEs) in paddy soils poses a serious threat to human health. However, related studies mainly focus on facility vegetable fields, drylands, and orchards, and little is known about paddy soils. In this study, 125 samples were collected from typical red paddy fields to investigate the pollution characteristics, sources, health risks, and main drivers of PAEs. Soil physicochemical properties, enzyme activity, and bacterial community composition were also measured simultaneously. The results showed that eight PAE congeners were detected ranging from 0.17 to 1.97 mg kg-1. Di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP), and di-isobutyl phthalate (DIBP) were the most abundant PAE congeners, accounting for 81% of the total PAEs. DEHP exhibited a potential carcinogenic risk to humans through the intake route. The main PAEs were positively correlated with soil organic matter (SOM) and soil water content (SWC) contents. Low levels of PAEs increased bacterial abundance. Furthermore, most PAE congeners were positively correlated with hydrolase activity. Soil acidity and nutrient dynamics played a dominant role in the bacterial community composition, with PAE congeners playing a secondary role. These findings suggest that there may be a threshold response between PAEs and organic matter and nutrient transformation in red paddy soils, and that microbial community should be the key driver. Overall, this study deepens the understanding of ecological risks and microbial mechanisms of PAEs in red paddy soils.

Interaction impact of biocompost on nutrient dynamics and relations with soil biota, carbon fractions index, societal value of CO2 equivalent and ecosystem services in the wheat-rice farming

This experiment aimed to understand the recycled industrial biocompost interaction with fertilizers doses on soil nutrient dynamics, soil organic carbon (SOC) fraction indexes, microbial population, positive ecosystem services, carbon dioxide (CO2) societal values and economy in wheat (Triticum aestivum L.)–rice (Oryza sativa L.) production. Based on the field and lab data, a significant interaction was observed between the biocompost and fertilizer levels; the fertilizer doses (FD)3 × biocompost (BC)1 were observed 80.6 grain and 56.0% higher straw yield in the wheat-rice crops than FD0 × BC9. Based on the results of soil organic carbon (SOC), the treatment FD3 × BC1 was observed more very labile (5.06 g kg−1) and moderately labile (4.26 g kg−1) carbon (C) fractions. However, C liability and recalcitrant indexes were recorded as non-significant. Further, the interaction effects of FD3 × BC1 found 65.7% more CO2 sequestration over FD0 × BC9. In terms of microbial dynamics, at 45 days after sowing (DAS), the treatment FD3 × BC4 was found to be the highest soil bacteria (56.6 × 107), fungi (32.3 × 105), and actinomycetes (49.1 × 106 cfu g−1) population. Further, regarding ecosystem services, the FD3 × BC1 found a maximum of US$ 1236 and 322 ha−1 year−1 grain and straw-based ecosystem services, respectively. However, the treatment FD3 × BC1 observed the maximum societal value (US$ 2041 ha−1). In contrast, higher economic values of 77.9 and 138.8% gross and net returns were recorded in the FD3 × BC1 compared to FD0 × BC9 in the wheat-rice cropping sequence (WRCS), respectively. Therefore, the study's hypothesis was to know the impact of the biocompost with fertilizers doses to enhance the nutrient and microbial dynamics, increasing SOC fractions (active and passive) and pools, CO2 sequestration, and restoring the soil health in the WRCS.

Post Manure Application Time and Rate on Soil Nutrient Changes and Seed Proximate Contents of Egusi Melon (Colocynthis citrullus L.)

ABSTRACT The efficiency of manure application is a function of quantity and time of application. Two field trials were conducted to determine the effects of time and quantity of manure application on soil nutrient dynamics and proximate contents in Abeokuta, Nigeria, by cultivating egusi melon with 0, 5, 10, and 15 t.ha−1 poultry manure (PM) applied at 2 and 4 weeks before planting (WBP). Melon was planted at 2 and 4 weeks after manure application (WAMA). The year of cultivation affected post cropping soil nutrient contents. Soil organic matter was not reduced with 10 t.ha−1 application. It also maintained soil nitrogen content and increased exchangeable potassium. Soil calcium and magnesium content increased with cropping. In 2017, planting with 5 t.ha−1 PM applied at 2 WBP gave the highest exchangeable acidity content, but from 10 t.ha−1 PM applied at 4 WBP, in 2018. Soil calcium and magnesium contents were higher with 2 years cropping. It was highest with either 10 t.ha−1 PM at 2 WBP or 5 t.ha−1 PM at 4 WBP. Soil magnesium content was highest with 10 t.ha−1 PM at 2 WBP. Cropping increased soil sand and clay particles but reduced silt particles. Seed crude protein was reduced with 2 years cropping. It was highest from 15 t.ha−1 PM applied at 2 WBP in 2017. Seed fat and carbohydrate contents were increased with 2 years cropping. For soil calcium and magnesium contents, 10 t.ha−1 PM applied at 2 WBP poultry manure is optimum.

The competition between Bidens pilosa and Setaria viridis alters soil microbial composition and soil ecological function

Bidens pilosa is recognized as one of the major invasive plants in China. Its invasion has been associated with significant losses in agriculture, forestry, husbandry, and biodiversity. Soil ecosystems play an important role in alien plant invasion. Microorganisms within the soil act as intermediaries between plants and soil ecological functions, playing a role in regulating soil enzyme activities and nutrient dynamics. Understanding the interactions between invasive plants, soil microorganisms, and soil ecological processes is vital for managing and mitigating the impacts of invasive species on the environment. In this study, we conducted a systematic analysis focusing on B. pilosa and Setaria viridis, a common native companion plant in the invaded area. To simulate the invasion process of B. pilosa, we constructed homogeneous plots consisting of B. pilosa and S. viridis grown separately as monocultures, as well as in mixtures. The rhizosphere and bulk soils were collected from the alien plant B. pilosa and the native plant S. viridis. In order to focus on the soil ecological functional mechanisms that contribute to the successful invasion of B. pilosa, we analyzed the effects of B. pilosa on the composition of soil microbial communities and soil ecological functions. The results showed that the biomass of B. pilosa increased by 27.51% and that of S. viridis was significantly reduced by 66.56%. The organic matter contents in the bulk and rhizosphere soils of B. pilosa were approximately 1.30 times those in the native plant soils. The TN and NO3– contents in the rhizosphere soil of B. pilosa were 1.30 to 2.71 times those in the native plant soils. The activities of acid phosphatase, alkaline phosphatase, and urease in the rhizosphere soil of B. pilosa were 1.98–2.25 times higher than in the native plant soils. Using high-throughput sequencing of the 16S rRNA gene, we found that B. pilosa altered the composition of the soil microbial community. Specifically, many genera in Actinobacteria and Proteobacteria were enriched in B. pilosa soils. Further correlation analyses verified that these genera had significantly positive relationships with soil nutrients and enzyme activities. Plant biomass, soil pH, and the contents of organic matter, TN, NO3–, TP, AP, TK, and AK were the main factors affecting soil microbial communities. This study showed that the invasion of B. pilosa led to significant alterations in the composition of the soil microbial communities. These changes were closely linked to modifications in plant traits as well as soil physical and chemical properties. Some microbial species related to C, N and P cycling were enriched in the soil invaded by B. pilosa. These findings provide additional support for the hypothesis of soil-microbe feedback in the successful invasion of alien plants. They also offer insights into the ecological mechanism by which soil microbes contribute to the successful invasion of B. pilosa. Overall, our research contributes to a better understanding of the complex interactions between invasive plants, soil microbial communities, and ecosystem dynamics.

Basalt addition improves the performance of young grassland monocultures under more persistent weather featuring longer dry and wet spells

Global warming is altering the intra-annual variability of precipitation patterns in the mid-latitudes, including a shift towards longer dry and wet spells compared to historic averages. Such fluctuations will likely alter soil water and nutrient dynamics of managed ecosystems which could negatively influence their functioning (e.g., productivity and fodder quality). Here, we investigated whether basalt addition could attenuate effects of increasingly persistent precipitation regimes (PR) on two agricultural grassland monocultures differing in drought resistance (low: Lolium perenne (LP) vs high: Festulolium (FL)) and digestibility (high: LP, low: FL), while improving soil C sequestration. In total, 32 experimental mesocosms were subjected to either a low (1-day wet/dry alternation) or a highly (30-day wet/dry alternation) persistent PR over 120 days, keeping total precipitation equal. In half of these mesocosms, we mixed basalt with the top 20 cm soil layer at a rate of 50 t ha−1. Overall, 30-day PR increased average water availability resulting in improved aboveground biomass and shoot digestibility for both species, in spite of elevated physiological stress. These PR also increased shoot Si, K, N and C but reduced Ca accumulation. Basalt addition generally increased soil Al, Ni, Mg, Ca, P, K and Si availability without altering root biomass or total soil carbon. Moreover, differences in root N content and C:N ratio between species were reduced. Interestingly, basalt modified the PR effects on productivity. Within 30-day PR, basalt stimulated aboveground biomass (±14%) and root Si and K contents without altering plant digestibility, palatability, crude protein content or Ni/Al content. These results indicate that basalt can stimulate grassland productivity and soil nutrient availability under more persistent PR without negatively affecting fodder quality. Hence, basalt application may improve the performance of young temperate grassland monocultures under climate change, though dry soil conditions may limit effects on soil C sequestration during summer.

Agricultural management practices impact soil properties more than soil microarthropods

Soil biology is a fundamental aspect of soil quality; thus, it is imperative to understand how agricultural management impacts soil organisms. Among soil biota, microarthropods such as mites (Acari) and springtails (Collembola) act at multiple trophic levels, influencing soil microbial communities and nutrient dynamics. We investigated how agricultural management influences soil microarthropods at the U.S. Department of Agriculture (USDA) Agricultural Research Service Farming Systems Project (FSP), a long-term study comparing the sustainability and productivity of conventional and organic agriculture, in Beltsville, Maryland. We sampled soil and soil microarthropods from plots under conventional management—tilled and no till—and under organic management. Though soils managed using organic practices had significantly higher values for organic matter and several key nutrients, we found no significant differences in microarthropod abundance and QBS-ar score among agricultural systems. All agricultural plots scored lower in both metrics than undisturbed areas evaluated for comparison. Thus, differences in abiotic soil factors do not necessarily translate into differences in the biotic community; these differences may only be apparent with greater taxonomic resolution than used in this study. These results demonstrate the utility of the QBS-ar index in evaluating impacts of agricultural management on biological components of soil quality, specifically soil arthropod communities.

Effects of the combined application of biochar and humic substances on the improvement of saline cropland in the Yellow River Delta of China

AbstractSoil salinization has become a global environmental problem with the potential to cause serious land degradation. Thus, improving salt‐affected soils and enhancing the nutrient utilization efficiency of saline farmlands through scientific and effective measures are urgent scientific problems. In this study, a 2‐year field experiment was conducted to evaluate the effects of different soil amendments and their combinations on the dynamics of soil salinity, soil nutrients, and crop yield in a moderately salinized soil (EC1:5 of 0.78 dS m−1 and total salt content of 3.06 g kg−1). Nine soil treatments were implemented: biochar (B), lignocellulose (L), humic acid (H), fulvic acid (F), biochar + humic acid (B + H), biochar + fulvic acid (B + F), lignocellulose + humic acid (L + H), lignocellulose + fulvic acid (L + F), and control (CK). The results demonstrated that the application of F led to a certain reduction on the contents of soil salt, Na+, and Cl− among the soils amended with a single amendment application. The combined application of B and F or H could increase the soil desalination rate and increase the mineral N and Olsen‐P concentrations at a soil depth of 0–20 cm, which improved the grain yield, biological yield, N recovery efficiency (REN), N agronomic efficiency (AEN), N partial factor productivity (PFPN), P agronomic efficiency (AEP), and P partial factor productivity (PFPP). Although the single application of L led to decreases in the grain yield, biological yield, REN, AEN, PFPN, REP, AEP, PFPP, and P physiological efficiency (PEP), the combined application of L and F had superior effects on enhancing the winter wheat grain yield and accumulative nutrient use efficiency. In conclusion, the combined application of B and F or H is recommended to ameliorate salt‐affected soils and improve nutrient availability.

Fragment size and diversity of mulches affect their decomposition, nutrient dynamics, and mycorrhizal root colonisation

Plant-based mulch has been proposed as a sustainable way of maintaining soil fertility. However, the role of mulch diversity, quality, and size in decomposition dynamics, and their effect on crop yield, has not been fully explored. We investigated how mulch quality, proxied by the constituent plant species diversity, and residue size drive mulch decomposition, nutrient release, crop nutrition, and yield. A rhizotron experiment was set up with barley as a model crop, with the addition of mulch of two particle sizes (1.5 and 30 cm) and four different plant residue mixes of differing biodiversity (17, 12, 6, and 1 species) in a fully factorial design. Soil nutrient dynamics were measured at advanced decomposition stages, together with residue quality, arbuscular mycorrhizal fungal (AMF) root colonisation, and crop yield. Residue mass loss was significantly affected by its chemical composition. Initial NDF content was more restricted factor in C and N mineralisation than C:N or lignin. Long residues retained significantly higher C and N content, than short residues. Crop yield was not affected by residue type or size. Residue size significantly affected barley growth rate, influencing seed protein content. Soil available K was significantly increased by residues with a higher initial C:N ratio. Short residues resulted in higher soil Zn. Residues of higher diversity resulted inhigher AMF root colonisationof the barley plants. Generally, long residue mulches maintain higher fertilisation capacity at advanced stage of decomposition than short ones, without a deleterious effect on crop yield. Further investigation should evaluate the effect of continuous application of long residue mulches on soil fertility and microbial symbiosis.

Opposite response of N2O emissions in different seasons to warming and precipitation addition on a temperate steppe

AbstractClimate change is an important issue that affects both global warming and precipitation, and the main cause is increased N2O emissions. Temperature and moisture are key factors in grassland ecosystem's response to climate change, and they can affect N2O fluxes. To clarify the impacts of warming and precipitation changes on N2O fluxes, an experiment was conducted in a semiarid steppe in Inner Mongolia, China over a nine‐year period (2011–2019). Plant productivity and soil nutrient dynamics were examined concurrently from 2017 to 2019, and N2O fluxes were monitored in response to different treatment conditions: control (C), warming (W), precipitation addition (P), and warming and precipitation addition (WP). The results showed that N2O emissions in the growing season were higher than those in the nongrowing season. Warming and precipitation addition had no significant effect on N2O fluxes compared with ambient conditions. Compared with P treatment, warming increased N2O flux in nongrowing season and decreased it in growing season. N2O flux was positively correlated with soil temperature and moisture (p &lt; 0.05). Warming had a significant positive effect on soil NH4+‐N, whereas additional precipitation had a large positive effect on soil total nitrogen and soil nitrate nitrogen. With the WP treatment, soil microbial biomass nitrogen (MBN) and soil microbial biomass carbon (MBC) increased by 53.8% and 41.9%, respectively. The decrease in N2O emissions during the growing season in the W treatment compared with the P treatment may be largely attributed to the greater dominance of Leymus chinensis. The results highlight that changes in species dominance play an important role in regulating N2O emissions, and that the N2O fluxes in the nongrowing season account for a large proportion of the changes in N2O fluxes. Therefore, The warming effects on N2O emissions during nongrowing seasons should be further investigated.

Effect of inter-tillage weeding on rice yield, rice growth, and nutrient dynamics without agrochemical and fertilizer application: Results of a three-year study

Traditionally, frequent inter-tillage is believed to increase rice yield without the application of chemicals. However, research on rice growth and soil nutrient dynamics under such cultivation management is lacking. In this study, we performed rice cultivation without applying agrochemicals and fertilizers to elucidate the influence of inter-tillage, especially, three years after switching to no chemical application. The rice growth, rice yield, and nutrient (N, P, and K) dynamics over three years (2018–2020) were assessed, including three different treatments: 0-, 2-, and 5-times inter-tillage (0-T, 2-T, and 5-T, respectively) and conventional cultivation as rough reference. In the first year, the brown rice yield in inter-tillage fields (531–566 g/m2) was higher than the regional average yield for conventional rice cultivation (497 g/m2) after several years of fallow with herbicide. In the second year, following nutrient consumption in the first year, the yield in inter-tillage fields (220–272 g/m2) was less than the regional average yield (547 g/m2). There was no significant variation (P < 0.05) in yields in the three inter-tillage fields in the first and second years. However, in the third year, the order of yield achieved in experimental fields was 5-T (354 g/m2) > 2-T (209 g/m2) > 0-T (173 g/m2), although these yields were lower than the regional average yield (561 g/m2). The exchangeable ammonium concentration in the soil and the ammonium concentration in the soil solution from inter-tillage fields decreased in the third year compared to the second year's results. However, the rice yield, growth, and nitrogen concentration in rice plants in 5-T increased in the third year. Our findings indicate that several years of inter-tillage make the soil environment effectively suitable for fertilizer- and chemical-free rice cultivation.

Influence of Rice Straw Biochar Application on Soil Nutrient Dynamics and Rice Productivity Under Different Irrigation Regimes

Influence of Rice Straw Biochar Application on Soil Nutrient Dynamics and Rice Productivity Under Different Irrigation Regimes

Mixed-Species Acacia Plantation Decreases Soil Organic Carbon and Total Nitrogen Concentrations but Favors Species Regeneration and Tree Growth over Monoculture: A Thirty-Three-Year Field Experiment in Southern China

Mixed-species plantations of trees with N-fixing species have the potential of promoting forest productivity and soil fertility. However, few studies in the literature have addressed the advantages of mixed-species plantations of leguminous trees over monocultures of leguminous trees based on in situ inventories over a long time period. Here, we monitored the dynamics of tree community composition, vegetation biomass, soil nutrients, and soil microbial phospholipid fatty acids (PLFAs), in an Acacia mangium monoculture plantation during 33 years of development and compared it with a mixed-species plantation of A. mangium associated with 56 native species which were underplanted 14 years after the initial establishment. Leaf N and phosphorus (P) concentrations of three main species in the overstory and understory of the A. mangium monoculture were measured. Our results showed that the soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP) concentrations significantly increased over time during the approximately thirty years of A. mangium monoculture plantation, while the disadvantages were associated with new species regeneration and the increment of vegetation biomass. In the A. mangium monoculture plantation, leaf N concentration of A. mangium,Rhodomyrtus tomentosa, and Dicranopteris dichotoma continuously increased from 21 to 31 years, while the leaf P concentration of A. mangium and R. tomentosa decreased. The mixed-species plantations of A. mangium with native tree species had lower SOC and soil TN concentrations, more new tree species recruitment in the understory, and faster vegetation biomass increment than the A. mangium monoculture. However, the PLFAs of soil microbial groups were slightly different between the two types of plantations. We conclude that improved soil N nutrient condition by A. mangium monoculture benefits N absorption by A. mangium, R. tomentosa, and D. tomentosa, while low soil AP limits P absorption by A. mangium and R. tomentosa. Meanwhile, transforming the A. mangium monoculture into a mixed-species plantation via the introduction of multiple native species into the A. mangium monoculture decreases SOC and TN concentrations but the advantages include improving forest regeneration and maintaining forest growth in a long-term sequence. These findings provide useful and practical suggestions for managing forest monocultures of A. mangium in subtropical regions.

The Complex, Unique, and Powerful Imaging Instrument for Dynamics (CUPI2D) at the Spallation Neutron Source (invited).

The Oak Ridge National Laboratory is planning to build the Second Target Station (STS) at the Spallation Neutron Source (SNS). STS will host a suite of novel instruments that complement the First Target Station's beamline capabilities by offering an increased flux for cold neutrons and a broader wavelength bandwidth. A novel neutron imaging beamline, named the Complex, Unique, and Powerful Imaging Instrument for Dynamics (CUPI2D), is among the first eight instruments that will be commissioned at STS as part of the construction project. CUPI2D is designed for a broad range of neutron imaging scientific applications, such as energy storage and conversion (batteries and fuel cells), materials science and engineering (additive manufacturing, superalloys, and archaeometry), nuclear materials (novel cladding materials, nuclear fuel, and moderators), cementitious materials, biology/medical/dental applications (regenerative medicine and cancer), and life sciences (plant-soil interactions and nutrient dynamics). The innovation of this instrument lies in the utilization of a high flux of wavelength-separated cold neutrons to perform real time in situ neutron grating interferometry and Bragg edge imaging-with a wavelength resolution of δλ/λ ≈ 0.3%-simultaneously when required, across a broad range of length and time scales. This manuscript briefly describes the science enabled at CUPI2D based on its unique capabilities. The preliminary beamline performance, a design concept, and future development requirements are also presented.

Long-term warming-induced trophic downgrading in the soil microbial food web

Climatic warming has been hypothesized to accelerate organic matter decomposition by soil microorganisms and thereby enhance carbon (C) release to the atmosphere. However, the long-term consequences of soil warming on belowground biota interactions are poorly understood. Here we investigate how geothermal warming by 6 °C for more than 50 years affects soil microbiota. Using metatranscriptomics we obtained comprehensive profiles of the prokaryotic, eukaryotic and viral players of the soil microbial food web. When compared to ambient soil temperature conditions, we found pronounced differences in taxa abundances within and between trophic modules of the soil food web. Specifically, we observed a ‘trophic downgrading’ at elevated temperature, with soil fauna decreasing in abundance, while predatory bacteria and viruses became relatively more abundant. We propose that the drivers for this shift are previously observed decreases in microbial biomass and soil organic carbon, and the increase in soil bulk density (decrease in soil porosity) at elevated temperature. We conclude that a trophic downgrading may have important implications for soil carbon sequestration and nutrient dynamics in a warming world.

Wild boar (Sus scrofa) has minor effects on soil nutrient and carbon dynamics

ABSTRACT Wild boar populations have increased worldwide, but the consequences of their disturbances on boreal forest ecosystems are largely unknown. We investigated how wild boars affect soil processes in a Swedish boreal forest. We estimated effects on ecosystem functioning using phospholipid fatty acid analyses (PLFA) to characterise microbial groups, and by measuring soil respiration, soil carbon (C), nitrogen (N) and phosphorus (P) concentrations, as well as the availability of NO3 − and NH4 +. We compared samples collected inside wild boar enclosures with adjacent reference areas without wild boar disturbance. We found no difference in soil microbial composition, except for a consistently higher fungi:bacteria ratio in the enclosures. These results are contrary to our hypothesis that rooting raises nitrogen levels, which in turn result in more bacteria. Soil nutrient levels showed inconsistent patterns, suggesting that substrate changes – as opposed to nutrient changes – stimulated fungal growth. Soil respiration was lower in the enclosures, contradicting earlier findings suggesting increased soil CO2 emissions from wild boar rooting. Overall, our study suggests that increased wild boar abundance has a minor impact on soil processes in boreal forests. Future studies should determine if the modest impacts remain across time and boreal forests.

Biomass composite with exogenous organic acid addition supports the growth of sweet sorghum (Sorghum bicolor 'Dochna') by reducing salinity and increasing nutrient levels in coastal saline-alkaline soil.

In coastal saline lands, organic matter is scarce and saline stress is high. Exploring the promotion effect of intervention with organic acid from biological materials on soil improvement and thus forage output and determining the related mechanism are beneficial to the potential cultivation and resourceful, high-value utilization of coastal mudflats as back-up arable land. Three exogenous organic acids [humic acid (H), fulvic acid (F), and citric acid (C)] were combined with four kinds of biomass materials [cottonseed hull (CH), cow manure (CM), grass charcoal (GC), and pine needle (PN)] and applied to about 0.3% of medium-salt mudflat soil. The salinity and nutrient dynamics of the soil and the growth and physiological differences of sweet sorghum at the seedling, elongation, and heading stages were observed under different treatments to screen for efficient combinations and analyze the intrinsic causes and influencing mechanisms. The soil salinity, nutrient dynamics, and forage grass biological yield during sweet sorghum cultivation in saline soils differed significantly (p < 0.05) depending on the type of organic acid-biomass composite applied. Citric acid-pine needle composite substantially reduced the soil salinity and increased the soil nutrient content at the seedling stage and improved the root vigor and photosynthesis of sweet sorghum by increasing its stress tolerance, allowing plant morphological restructuring for a high biological yield. The improvement effect of fulvic acid-pine needle or fulvic acid-cow manure composite was manifested at the elongation and heading stages. Citric acid-pine needle composite promoted the growth of saline sweet sorghum seedlings, and the effect of fulvic acid-pine needle composite lasted until the middle and late stages.