Search

Symbiosis with arbuscular mycorrhizal (AM) fungi improves plant nutrient capture from the soil, yet there is limited knowledge about the diversity, structure, functioning, and assembly processes of AM fungi‐related microbial communities. Here, 16S rRNA gene sequencing and metagenomic sequencing were used to detect bacteria in the rhizosphere of Lotus japonicus inoculated with and without AM fungi, and the L. japonicus mutant ljcbx (defective in symbiosis) inoculated with AM fungi in southern grassland soil. Our results show that AM symbiosis significantly increased bacterial diversity and promoted deterministic processes of bacterial community construction, suggesting that mycorrhizal symbiosis resulted in the directional enrichment of bacterial communities. AM fungi promoted the enrichment of nine bacteria, including Ohtaekwangia, Niastella, Gemmatimonas, Devosia, Sphingomonas, Novosphingobium, Opitutus, Lysobacter, Brevundimonas, which are positively correlated with NPK‐related parameters. Through a functional identification experiment, we found that six of these genera, including Brevundimonas, Lysobacter, Ohtaekwangia, Sphingomonas, Devosia, and Gemmatimonas, demonstrated the ability to mineralize organophosphate and dissolve inorganic phosphorus, nitrogen, and potassium. Our study revealed that AM fungi can regulate rhizosphere bacterial community assembly and attract specific rhizosphere bacteria to promote soil nutrient turnover in southern grasslands. [ABSTRACT FROM AUTHOR]

Abundant and functionally diverse earthworm communities in perennials deliver ecosystem services like increasing nutrient availability by incorporating organic matter. This study aimed to analyse the decomposition of annual and perennial energy crop residues, and the subsequent nutrient release, depending on earthworm functional diversity. In a laboratory experiment, two ecological earthworm groups—anecics (detritivorous Lumbricus terrestris (L.)) and endogeics (geophagous Aporrectodea caliginosa and A. rosea)—were incubated with wilted cup plant (Silphium perfoliatum) and maize (Zea mays) litter for 4 or 8 weeks. Decomposition and consumption rates were calculated. The C, N and P in litter and casts were analysed. Mineralisation was a function of earthworm biomass and the number of individuals. Functional diversity had no beneficial effect. Decomposition was found to be highest in treatments with detritivorous earthworms, i.e., higher earthworm biomass, yet consumption and nutrient turnover in relation to earthworm biomass were higher in treatments with geophages indicating enhanced competition. N limitation became apparent in both litter treatments and was predominant with cup plant litter. N limitation and recalcitrant cell wall compounds affected consumption rates and the egestion of total C and P. While N in casts was lower than expected, P was increased. We observed that the effects manifested at different stages of decomposition of maize and cup plant, highlighting differences in temporal development of decomposition and nutrient turnover between litter types. Our results indicate that earthworms promote decomposition of recalcitrant litter and nutrient turnover, but N limitation may hamper nutrient release. Cup plant systems offer a suitable habitat for soil-dwelling organisms, but management approaches must consider the adequate input of organic matter as an energy and nutrient source to enhance ecosystem service provision. [ABSTRACT FROM AUTHOR]

The effective performance of ameliorative functions by water protection plantations is largely determined by the development of the forest litter, its structure, capacity, quality composition, and degree of mineralization. Therefore, the aim of the study was to identify the features of the formation of the forest litter of pine plantations of the Ukrainian interfluves of the Dnipro and Desna. The study of forest litter was carried out on the accounting sites in all age groups of plantations, in which 22 test plots were laid. Litter samples were taken in between rows and directly in rows of forest plantations. During the analysis of the qualitative composition of the forest litter of young plantations, the dominance of the upper horizon of the inactive fraction, which consisted mainly of needles and branches, was revealed. Here, the share of inactive litter in the conditions of moist poor pine site and moist relatively poor pine site was 8.13 t/ha or 85.1% and 12.54 t/ha or 92.1%, respectively. A large amount of dust, which forms the active fraction, was recorded in the lower horizon. Its stocks were 5.3-5.6 times higher than the reserves of inactive litter. In general, in young pine forests in the conditions of moist poor pine site, the stock of inactive litter is 15.10 t/ha (28.1%), while its presence in of moist poor pine site is 17.91 t/ha, 36.5%. In middle-aged pine forests, the share of the active litter fraction increases, which is a consequence of the active action of its decomposition processes. The share of active litter is 79.3% or 155.29 t/ha in mature stands of the conditions of moist poor pine site. This is evidence of the intensification of the processes of mineralization and activation of the circulation of substances. Three horizons are clearly distinguished in the litter of plantations of older age groups, with a strong connection between them. The lower layer of the forest litter of water conservation plantations is permeated with physiologically active roots, which forms its dense type of structure. Under such conditions, during the separation of the lower layer of litter from the upper one, it does not fall apart and its structure remains dense. The presence of strongly intertwined physiologically active roots in the third horizon of the litter is evidence of the activation of microbiological processes, which are also accelerated by the interception of moisture and the accumulation of humus particles of the soil by the lower layers of the forest litter. To prevent the development of flood processes, the effective performance of water regulation and water purification functions, it is recommended to create water conservation plantations with the formation of the identified type of forest litter. [ABSTRACT FROM AUTHOR]

Degraded soils (including salinized, eroded, and low organic matter) resulting from natural and human effects are universal in arid and semi-arid regions all over the world. Bentonite and humic acid (BHA) are increasingly being tested to remediate these degraded lands, with potential benefits on crop production and soil health. A field study was conducted to quantify the effects of BHA application at six rates (0, 6, 12, 18, 24, and 30 Mg ha−1) on (i) dynamic changes in soil properties and (ii) oat crop productivity parameters in a dryland farming ecosystem. The specific objective of this paper was to determine the residual effects four to five years after a one-time BHA application on soil health and crop performance. The findings demonstrated that with the increasing rates of one-time BHA application, soil profile water storage displayed a piecewise linear plus plateau increase, whereas soil electrical conductivity, pH, and bulk density were all reduced significantly (p < 0.05) in the 0–20 cm and 20–60 cm layers. The improved soil environments gave rise to an increased activity of soil enzymes urease, invertase, and catalase that, respectively, reached peak values of 97%, 37%, and 32% of the control at the rates of 18 to 24 Mg BHA ha−1. In turn, this boosted soil nutrient turnover, leading to a 40% higher soil available P. Compared with the control treatment, application of BHA at the estimated optimum rate (roughly 24 Mg ha−1) increased grain yield by 20%, protein yield by 62%, water use efficiency by 41%, and partial factor productivity of N by 20%. The results of this study indicated for the first time that a one-time BHA application would be a new and effective strategy to combat land degradation and drought, and promote a sustainable soil micro-ecological environment in dryland agroecosystems under a varying climate scenario. [ABSTRACT FROM AUTHOR]

Subordinate species have relatively low abundance compared to dominant species; however, they may contribute significantly to functional diversity and ecosystem functionality, particularly if they differ strongly from the dominants in key traits. Here we investigated whether this phenomenon might be applied to litter decomposition as a key carbon and nutrient cycling process.We hypothesized that species litter mass‐weighted predictions of community‐level litter decomposition based on dominant rates only, would deviate strongly from observed community‐level rates, and that predictions would improve as subordinates with strongly contrasting traits were combined with those of their dominant counterparts.We tested this hypothesis through a 1‐year field decomposition experiment across a chronological sequence in a subtropical evergreen broadleaved forest. The experiment included the single‐species litter of evergreen dominants, evergreen subordinates and deciduous subordinates, respectively, as well as community‐level litter mixtures.The expected community‐weighted mean decomposition rates based on the evergreen dominants alone, with or without the addition of evergreen subordinates, deviated strongly from those of observed community litter mixtures at the middle and late succession stages, but not at the early stage. When adding deciduous subordinates to this expectation, there was no longer any difference to the observed community litter decomposition rate across succession stages. Deciduous subordinates alone explained 7%, 21% and 15% of the total variation in community litter mixture decomposition rate for early, middle and late successional stages, respectively, which is more than would be expected from their litter mass fraction.Synthesis. Deciduous subordinates with strongly contrasting nutritional and water‐storage traits compared to the dominant evergreens significantly impacted litter decomposition at the community‐level in spite of their low abundance. This study highlights the importance of 'being different' for subordinates to be influential in ecosystem carbon cycling. [ABSTRACT FROM AUTHOR]

Degraded lands resulting from human and natural causes are widespread in arid and semiarid regions throughout the world. Polyacrylamide (PAM) soil amendments are increasingly used to remediate these degraded lands with the potential benefits on soil health and crop production. However, the scientific evidence of farm‐scale use of one‐time versus repeated application of PAM has not been reported. The specific objective of this research was to determine the effects of single versus multiple annual PAM application on (a) the dynamic changes in soil quality parameters and (b) oat crop productivity indicators in a dryland farming ecosystem. Our data illustrated that multiple years of annual application of PAM significantly increased soil profile water storage, whereas it reduced soil bulk density and electrical conductivity in the top (0–20 cm) and deeper layers (20–60 cm) over those for the control or single PAM application. The improved soil microecological environments led to increased activities of soil enzymes urease (up to 106%), invertase (94%), and catalase (45%). These in turn promoted soil nutrient turnover and availability (e.g., 76% higher soil alkaline N) and crop growth leading to the improvement in grain protein (up to 31%), protein yield (58%), and partial factor productivity of nitrogen (20%), than did the control treatment. Taken together, these soil and crop performance indicators suggest that repeated annual PAM application for a minimum of 2–3 years would be an effective strategy to combat drought and land degradation and foster sustainable crop production in dryland agriculture under a changing climate scenario. [ABSTRACT FROM AUTHOR]

Aims: The litter decomposition effects of N deposition in combination with management practices are still unclear. The aims of this study were to test the individual and interactive effects of the two factors on Moso bamboo leaf litter decomposition. Methods: The experiment was conducted in Moso bamboo forests over a 24-month period and included three N addition treatments (low N, 30 kg N ha yr;medium N, 60 kg N ha yr; and high N, 90 kg N ha yr) and two management practices (conventional management and intensive management). Results: The low-N treatment significantly increased the annual decomposition rate, whereas the high-N treatment significantly decreased the annual decomposition rate ( P < 0.05). Intensive management alone did not significantly influence decomposition, but it amplified both the positive effects of the low-N treatment and the negative effects of the high-N treatment on litter decomposition. Intensive management weakened the positive effects of N addition on N loss but enhanced the positive effects on P loss during the early stage. Conclusions: The effects of increasing N deposition in a plantation ecosystem were altered by the management practices, and these changes should be considered when estimating the biological effects of N deposition at regional and global scales. [ABSTRACT FROM AUTHOR]

Global change is altering the movement of materials across landscapes in ways that likely have major consequences for the functioning and stability of ecosystems. For example, the export of dissolved organic carbon (DOC) from terrestrial to aquatic ecosystems is increasing globally. This browning phenomenon is expected to alter the stability of recipient aquatic ecosystems, but theory provides contrasting predictions about the form and direction of this response. We created a gradient in terrestrial DOC supply by adding humic substances on weekly basis to 10 experimental ponds (106 L each) over a growing season. The manipulation of terrestrial DOC supply had strong effects on the chemical, physical, and biological properties of the pond ecosystems. Light attenuation linearly increased with terrestrial DOC supply, which created a shading effect that negatively influenced whole-pond gross primary production and respiration. Despite this, bacterial contributions to basal energy mobilization and respiration increased with terrestrial DOC supply indicating that aquatic food webs were subsidized by terrestrial inputs. After establishing the DOC gradient, we used dynamic linear models to test the subsidy-stability hypothesis by measuring the resilience and sensitivity of each pond to a pulse nutrient perturbation. We found that recovery from the perturbation decreased nonlinearly along a gradient in terrestrial DOC supply. Reciprocal transplant experiments indicated that owing primarily to its light attenuating properties and recalcitrant nature, terrestrial DOC diminished aquatic ecosystem stability by reducing nutrient turnover rates (NTR). Together, our results demonstrate that global-changemediated alterations in the movement of material and energy between habitats can have unpredictable and dramatic impacts on the reliability of ecosystem services. [ABSTRACT FROM AUTHOR]

The article focuses on a study to quantify litter production and associated nutrient turn over in selected developed stands of silvipasture systems involving the trees Acacia tortilis, Albizia amara, Hardwichia binata for the rehabilitation of degraded lands at Indian Grassland and Fodder Research Institute in India. Approaches to soil fertility assessment plays a vital role in soil organic matter. In a land ecosystem, the litter supply and root residues control nutrient cycling and energy transfers. It is a significant aspect of nutrient cycling that returns nutrients to the soil. The silvipasture systems for rehabilitating degraded lands have a great use in maintaining soil organic matter by litter fall and root residues from the tree component. Variations in litter fall pattern of tree species are also cited.

Rising atmospheric CO2 is expected to alter plant tissue quality which in turn could affect litter quality, decomposition, andcarbon and nutrient turnover. We tested this hypothesis using leaf litter of beech (Fagus sylvatica) and branchlets (wood + bark) of spruce (Picea abies) produced under contrasting CO2 concentrations in model ecosystems. Both types of litter produced under elevated CO2 had significantly lower N concentrations, but showedno CO2-related differences in carbon and lignin concentrations. Decomposition rates (mass loss) assessed in a natural temperate forest was significantly slower in litter produced at high CO2. However, this effect became stronger in beech leaves but gradually disappeared in spruce branchlets over the 331-d exposure period. Irrespective of CO2 treatment beech leaf litter lost 16%of its initial N content. Spruce branchlets produced at low CO2 lost 50% of their initial N content, and those produced at high CO2 lost 26%. Two isopod species representing native macro-decomposers consumed 36% more of the high CO2-produced beech litter than they did of low CO2-produced beech litter. Only small, and non-significant increases in consumption of high CO2-produced spruce branchlets were observed. Isopods feeding on high CO2 litter also produced more feces than those feeding litter from low CO2. Our results indicate that CO2-induced litter quality changes influence only certain stages of decomposition, and that these stages differ between different litter types. Inhibitory effects of elevated CO2, however,may be compensated by the positive feed back of intensified 'litter processing' of low quality litter by macro-decomposers. Consequently,the entire cycle of litter production and decomposition must be included in our analysis of the potential effects of rising CO2 on [ABSTRACT FROM AUTHOR]

Extensive areas of inland dunes are commonly overplanted with Scots pine (Pinus sylvestris). However, thus far the pine litterfall has not been investigated in detail in Scots pine stands overgrowing the landforms. Therefore, the aim of this study was to analyse the mass and chemical composition of litterfall in a dune Scots pine forest, paying special attention to the differences in the properties of the particular categories of litterfall (needles, twigs, bark, cones, residue) occurring in different seasons. The secondary goal of the research was to investigate the possible effect of contrasting slope aspect on litterfall properties. Litterfall was examined for three years on a north- and south-facing dune slope using the litter trap method. The mass and chemical composition (C, N, P, K, Mg, Mn, Ca, Fe, Al) of each litterfall category was analysed. Average annual mass of litterfall ranged from 322.0 ± 2.6 (slope N) to 361.9 ± 34.2 (slope S) g m−2 year−1. Fluctuations in the annual concentrations of N, P, K and Mg were determined, which was the result of their gradual withdrawal from needles before they were dropped in autumn. Immobile or poorly mobile elements (i.e., Mn, Ca, Fe and Al) were found to be steadily accumulated during the year in fallen tissues. The studied elements can be set in the following order as regards the annual pools which return to a topsoil with litterfall: C > N > Ca > K > Mg > Mn > Al > P > Fe on slope N and C > Ca > N > K > Mg > Al > P > Mn > Fe on slope S. Despite the fact that the residue (seeds etc.) constitutes a much smaller part of the total litterfall mass than the needles, comparable amounts of N, P, K, Al and Fe return to a topsoil with both these categories. The only element for which we determined differences in concentrations regarding slope aspect was Mn: the concentrations were significantly higher for needles, twigs, bark and cones on the N than the S slope. [ABSTRACT FROM AUTHOR]

Rivers are important ecosystems under continuous anthropogenic stresses. The hyporheic zone is a ubiquitous, reactive interface between the main channel and its surrounding sediments along the river network. We elaborate on the main physical, biological, and biogeochemical drivers and processes within the hyporheic zone that have been studied by multiple scientific disciplines for almost half a century. These previous efforts have shown that the hyporheic zone is a modulator for most metabolic stream processes and serves as a refuge and habitat for a diverse range of aquatic organisms. It also exerts a major control on river water quality by increasing the contact time with reactive environments, which in turn results in retention and transformation of nutrients, trace organic compounds, fine suspended particles, and microplastics, among others. The paper showcases the critical importance of hyporheic zones, both from a scientific and an applied perspective, and their role in ecosystem services to answer the question of the manuscript title. It identifies major research gaps in our understanding of hyporheic processes. In conclusion, we highlight the potential of hyporheic restoration to efficiently manage and reactivate ecosystem functions and services in river corridors. [ABSTRACT FROM AUTHOR]