Both arbuscular mycorrhizal (AM) fungi and phosphate solubilizing bacteria (PSB) are involved in phosphorus (P) mobilization and turnover but the influence of their interaction on organic P ...mineralization in the root free soil (hyphosphere) have been little studied. We investigated the interactive effects of an AM fungus (Rhizophagus irregularis, RI) and/or PSB (Pseudomonas alcaligenes, PA) on phytate mineralization and subsequent transfer to the host plant (Medicago sativa) using a two-compartment microcosm with a central 30 μm nylon mesh barrier. The root growth compartment containing 5 mg inorganic P (Pi, KH2PO4) kg−1 soil was inoculated with RI or uninoculated and the AM fungal hyphal soil containing 75 mg organic P (Po, Na-phytate) plus 0 or 5 mg Pi kg−1 soil was inoculated with PA or uninoculated. Sole inoculation with RI increased shoot P content compared with the uninoculated treatment and dual inoculation with both RI and PA did not increase shoot P compared with sole RI inoculation. Sole PA inoculation significantly increased microbial biomass P (MBP). Compared with sole PA inoculation soil MBP increased under zero-Pi addition but decreased under 5 mg Pi kg−1 soil addition in the dual inoculation RI/PA treatment. The uninoculated microcosms had the lowest acid phosphatase activity and the highest phytate-P remaining in the soil. Inoculation with PA led to higher acid phosphatase activity and lower phytate-P than did RI. Dual RI/PA inoculation had the highest acid phosphatase activity and the lowest phytate-P remaining in the soil. Addition of 5 mg Pi kg−1 soil to the hyphal compartment decreased phytate-P remaining in the RI and/or PA treatments. The phytate-P remaining in the soil was negatively correlated with soil acid phosphatase activity or MBP in the presence of RI but there was no correlation between shoot P and soil phytate-P. In conclusion, our results indicate that the mineralization of soil phytate was promoted by the interaction between the AM fungus and its hyphosphere PSB.
•Hyphosphere AM fungus–PSB interaction on phytate mineralization is studied.•PSB play a major role in phytate mineralization.•PSB competes for P with AM fungus in available P limited soil.•AM fungus primes PSB on phytate mineralization and turnover.
Purpose
Soil acidification from chemical N fertilization has worsened and is a major yield-limiting factor in the red soil (Ferralic Cambisol) of southern China. Assessment of the acidification ...process under field conditions over a long term is essential to develop strategies for maintaining soil productivity. The objective of this study was to quantify soil acidification rates from chemical fertilizers and determine the amount of manure needed to inhibit the acidification process.
Materials and methods
A long-term experiment with various fertilizations was carried out during 1990–2008 in a wheat–corn cropping system in the red soil of southern China. Treatments included non-fertilized control, chemical N only (N), chemical N and P (NP), chemical N, P and K (NPK), pig manure only (M), and NPK plus M (NPKM; 70 % total N from M). All N treatments had an input of 300 kg N ha
−1
year
−1
. Annual soil sampling was carried out for pH measurement and acidity analysis.
Results and discussion
Soil pH decreased sharply from an initial pH of 5.7 and then stabilized after 8 to 12 years of fertilization in the N, NP, and NPK treatments with a final pH of 4.2, 4.5, and 4.5, respectively. These three treatments significantly increased soil exchangeable acidity dominated by Al, decreased soil exchangeable base cations (Ca
2+
and Mg
2+
), and elevated acidification rates (3.2–3.9 kmol H
+
ha
−1
year
−1
). In contrast, the manure applications (M or NPKM) showed either an increase or no change in soil pH and increases in soil exchangeable base cations.
Conclusions
Urea application to the intensive cropping system accelerated acidification of the red soil during the 18-year field experiment. As 70 % or more total N source, continuous manure application can fully prevent or reverse red soil acidification process. As an effective animal waste management tool, manure incorporation into the acidic soil can promote the overall agricultural sustainability.
The presence of DNA in the cytoplasm is normally a sign of microbial infections and is quickly detected by cyclic GMP-AMP synthase (cGAS) to elicit anti-infection immune responses. However, chronic ...activation of cGAS by self-DNA leads to severe autoimmune diseases for which no effective treatment is available yet. Here we report that acetylation inhibits cGAS activation and that the enforced acetylation of cGAS by aspirin robustly suppresses self-DNA-induced autoimmunity. We find that cGAS acetylation on either Lys384, Lys394, or Lys414 contributes to keeping cGAS inactive. cGAS is deacetylated in response to DNA challenges. Importantly, we show that aspirin can directly acetylate cGAS and efficiently inhibit cGAS-mediated immune responses. Finally, we demonstrate that aspirin can effectively suppress self-DNA-induced autoimmunity in Aicardi-Goutières syndrome (AGS) patient cells and in an AGS mouse model. Thus, our study reveals that acetylation contributes to cGAS activity regulation and provides a potential therapy for treating DNA-mediated autoimmune diseases.
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•Acetylation suppresses cGAS activity•Aspirin directly acetylates cGAS•Aspirin inhibits cGAS-mediated interferon production•Aspirin alleviates DNA-induced autoimmunity in AGS mouse models and patient cells
Activation of the DNA sensor cGAS requires a deacetylation step, and its aspirin-induced acetylation can limit innate immune responses.
Arbuscular mycorrhizal fungi (AMF) are ubiquitous in soil and form nutritional symbioses with ~80% of vascular plant species, which significantly impact global carbon (C) and nitrogen (N) ...biogeochemical cycles. Roots of plant individuals are interconnected by AMF hyphae to form common AM networks (CAMNs), which provide pathways for the transfer of C and N from one plant to another, promoting plant coexistence and biodiversity. Despite that stable isotope methodologies (
C,
C and
N tracer techniques) have demonstrated CAMNs are an important pathway for the translocation of both C and N, the functioning of CAMNs in ecosystem C and N dynamics remains equivocal. This review systematically synthesizes both laboratory and field evidence in interplant C and N transfer through CAMNs generated through stable isotope methodologies and highlights perspectives on the system functionality of CAMNs with implications for plant coexistence, species diversity and community stability. One-way transfers from donor to recipient plants of 0.02-41% C and 0.04-80% N of recipient C and N have been observed, with the reverse fluxes generally less than 15% of donor C and N. Interplant C and N transfers have practical implications for plant performance, coexistence and biodiversity in both resource-limited and resource-unlimited habitats. Resource competition among coexisting individuals of the same or different species is undoubtedly modified by such C and N transfers. Studying interplant variability in these transfers with
C and
N tracer application and natural abundance measurements could address the eco physiological significance of such CAMNs in sustainable agricultural and natural ecosystems.
Relationships between abiotic (soil temperature and number of freeze-thaw cycles) or biotic factors (chemical elements, microbial biomass, extracellular enzymes, and decomposer communities in litter) ...and litter decomposition rates were investigated over two years in subalpine forests close to the Qinghai-Tibet Plateau in China. Litterbags with senescent birch, fir, and spruce leaves were placed on the forest floor at 2,704 m, 3,023 m, 3,298 m, and 3,582 m elevation. Results showed that the decomposition rate positively correlated with soil mean temperature during the plant growing season, and with the number of soil freeze-thaw cycles during the winter. Concentrations of soluble nitrogen (N), phosphorus (P) and potassium (K) had positive effects but C:N and lignin:N ratios had negative effects on the decomposition rate (k), especially during the winter. Meanwhile, microbial biomass carbon (MBC), N (MBN), and P (MBP) were positively correlated with k values during the first growing season. These biotic factors accounted for 60.0% and 56.4% of the variation in decomposition rate during the winter and the growing season in the first year, respectively. Specifically, litter chemistry (C, N, P, K, lignin, C:N and lignin:N ratio) independently explained 29.6% and 13.3%, and the microbe-related factors (MBC, MBN, MBP, bacterial and fungal biomass, sucrase and ACP activity) explained 22.9% and 34.9% during the first winter and the first growing season, respectively. We conclude that frequent freeze-thaw cycles and litter chemical properties determine the winter decomposition while microbe-related factors play more important roles in determining decomposition in the subsequent growing season.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Soils play a vital role in the global carbon (C) cycle, yet little is known about the calcium (Ca)-mediated stabilization of soil organic carbon (SOC) in calcareous soils. With wet sieving, density ...fractionation and an incubation experiment from field soils, we investigated the effects of long-term fertilization on the Ca-mediated stabilization of aggregate-associated organic C and on the SOC stock at a soil depth of 0–20 cm in a reclaimed Cambisol on the Loess Plateau of China. Compared to the initial soil, after ten years the SOC stock increased by 50%, 76%, 94% and 110% in soils amended with no fertilizer (control), 100% chemical fertilizer, 50% chemical fertilizer plus 50% chicken manure compost and 100% chicken manure compost, respectively. The specific C mineralization rate (SCMR, rate per unit SOC) decreased as silt and clay > macroaggregate > microaggregate, indicating that SOC in microaggregates was more stable than in macroaggregates and the silt and clay fraction. The exchangeable Ca in the bulk soil (P < 0.001) and soil aggregates (P < 0.001) were positively correlated with the SOC, whereas the Ca carbonate (CaCO3) was negatively correlated with the SCMR (P < 0.001). The application of compost not only increased the exogenous C inputs but also promoted the transformation of CaCO3 to exchangeable Ca compared with the sole chemical fertilization. Furthermore, organic fertilization significantly increased the organic C in the heavy fraction (> 2.0 g cm−3) compared with the sole chemical fertilization, which was positively correlated with the mass proportion of macroaggregates (P < 0.001). These results indicate that organic fertilization can enhance the availability of Ca for C binding possibly by forming organo-Ca complexes, which in turn improve soil aggregation, and thus contribute to a long-term SOC sequestration in reclaimed soils of the Loess Plateau of China.
•Exchangeable Ca was positively correlated with soil organic carbon (C).•CaCO3 was negatively correlated with the specific C mineralization rate.•Organic C in microaggregates was relatively stable.•The formation of organo-Ca complexes improved soil aggregation.•Organic fertilization promoted soil aggregation and enhanced C sequestration.
Biochar amended to soil may improve soil aggregation and in turn increase soil organic carbon (SOC) stabilization. In an intensive wheat–maize rotation system of the North China Plain, we ...investigated effects of one-year biochar application on soil aggregate-size distribution and structure stability, and aggregate-associated C concentrations. Three biochar (<1mm diameter, from corncob at 360°C for 24h) treatments were examined as no biochar amendment control, rate at 4.5 (B4.5) and 9.0tha−1year−1 (B9.0). Soil samples were collected from 0–10 and 10–20cm depths and separated into six water-stable aggregate sizes (≥5, 2–5, 1–2, 0.5–1, 0.25–0.5 and 0.053–0.25mm). Results showed that neither soil aggregation nor aggregate stability was significantly affected by biochar amendments. In contrast, more SOC was accumulated in the large fractions (≥5 and 2–5mm) under B9.0 than under the other two treatments. Meanwhile, more C occluded in the large fractions (≥5, 2–5 and 1–2mm) under both B4.5 and B9.0 than under no-biochar control, suggesting that biochar-C was physically protected within these aggregate fractions. Our data indicated that biochar application could be a potential pathway to improve native SOC and black C stabilization in the intensive cropping system of the North China Plain.
•One-year biochar amendment did not change soil aggregation.•Higher SOC and black C accumulated in large fractions under one-year biochar amendment.•Biochar was physically protected within soil aggregates.•Biochar amendment has potential to improve soil C stabilization.
Glomalin-related soil protein (GRSP) is known as an important microbial by-product which is crucial for preserving or accumulating soil organic carbon (SOC). However, the underlying mechanisms are ...not well understood. In this study, we investigated the chemical structures of GRSP and its relationship with SOC using
C nuclear magnetic resonance (NMR) in three tropical forests. The three forests, including a planted forest (PF), a secondary forest (MF) and a primary forest (BF), were selected to represent the natural successional process after disturbance in southern China. Results showed that the average concentrations of GRSP were (3.94 ± 1.09) mg cm
and accounting for (3.38 ± 1.15)% of the SOC in the top 10 cm soil. NMR analysis indicated rich aromatic C (~30%) and carboxyl C (~40%) in GRSP, and abundant alkyl C (~30%) and O-alkyl C (~50%) in SOC. The recalcitrance indexes (RI), as defined as the ratio of sum of alkyl C and aromatic C over sum of O-alkyl C and carboxyl C, was (98.6 ± 18.9)%, (145.5 ± 10.9)% and (20.7 ± 0.3)% in GRSP higher than that in SOC in the PF, MF and BF, respectively. This study demonstrated that the stubborn structure of GRSP probably regulate the resistance of SOC sequestration in tropical forests, especially in the planted and secondary forests.
Forests play an important role in global carbon cycles. However, the lack of available information on carbon stocks in dead organic matter, including woody debris and litter, reduces the reliability ...of assessing the carbon cycles in entire forest ecosystems. Here we estimate that the national DOM carbon stock in the period of 2004-2008 is 925 ± 54 Tg, with an average density of 5.95 ± 0.35 Mg C ha
. Over the past two decades from periods of 1984-1988 to 2004-2008, the national dead organic matter carbon stock has increased by 6.7 ± 2.2 Tg carbon per year, primarily due to increasing forest area. Temperature and precipitation increase the carbon density of woody debris, but decrease that of litter. Additionally, the woody debris increases significantly with above ground biomass and forest age. Our results can improve estimates of the carbon budget in China's forests and for better understanding of effects of climate and stand characteristics on dead organic matter distribution.Reliable estimates of the total forest carbon (C) pool are lacking due to insufficient information on dead organic matter (DOM). Here, the authors estimate that the current DOM C stock in China is 925 ± 54 Tg and that it grew by 6.7 ± 2.2 Tg C/yr over the past two decades primarily due to increasing forest area.
A surface roughening method, a combination of mechanical roughening and chemical etching, was developed for the fabrication of stable super-hydrophobic surfaces on aluminum alloy foils. The ...microstructure and wettability of super-hydrophobic surfaces were characterized by means of SEM, EDX, XPS and water contact angle measurement. The chemical etchants were aqueous solutions of nitric acid and copper nitrate. The effects of roughening methods, as well as the concentration of nitric acid and copper nitrate, on the super-hydrophobicity of the surfaces have been discussed. The results indicate that the super-hydrophobic surface has a binary structure consisting of microscale crater-like pits and nanoscale reticula. Stable super-hydrophobic aluminum alloy surfaces with contact angles greater than 150° are obtained at the optimum concentrations of nitric acid of 5
wt% or 10–20
wt% and copper nitrate of 2.1–20.5
mM, respectively.
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