Summary
The continuing nitrogen (N) deposition observed worldwide alters ecosystem nutrient cycling and ecosystem functioning. Litter decomposition is a key process contributing to these changes, but ...the numerous mechanisms for altered decomposition remain poorly identified.
We assessed these different mechanisms with a decomposition experiment using litter from four abundant species (Achnatherum sibiricum, Agropyron cristatum, Leymus chinensis and Stipa grandis) and litter mixtures representing treatment‐specific community composition in a semi‐arid grassland under long‐term simulation of six different rates of N deposition.
Decomposition increased consistently with increasing rates of N addition in all litter types. Higher soil manganese (Mn) availability, which apparently was a consequence of N addition‐induced lower soil pH, was the most important factor for faster decomposition. Soil C : N ratios were lower with N addition that subsequently led to markedly higher bacterial to fungal ratios, which also stimulated litter decomposition.
Several factors contributed jointly to higher rates of litter decomposition in response to N deposition. Shifts in plant species composition and litter quality played a minor role compared to N‐driven reductions in soil pH and C : N, which increased soil Mn availability and altered microbial community structure. The soil‐driven effect on decomposition reported here may have long‐lasting impacts on nutrient cycling, soil organic matter dynamics and ecosystem functioning.
Microcystin-LR (MC-LR) is prevalent in water and can be translocated into soil-crop ecosystem via irrigation, overflow (pollution accident), and cyanobacterial manure applications, threatening ...agricultural production and human health. However, the effects of various input pathways on the bioaccumulation and toxicity of MCs in terrestrial plants have been hardly reported so far. In the present study, pot experiments were performed to compare the bioaccumulation, toxicity, and health risk of MC-LR as well as its degradation in soils among various treatments with the same total amount of added MC-LR (150 μg/kg). The treatments included irrigation with polluted water (IPW), cultivation with polluted soil (CPS), and application of cyanobacterial manure (ACM). Three common leaf-vegetables in southern China were used in the pot experiments, including
L.,
L., and
L. All leaf vegetables could bioaccumulate MC-LR under the three treatments, with much higher MC-LR bioaccumulation, especially root bioconcentration observed in ACM treatment than IPW and CPS treatments. An opposite trend in MC-LR degradation in soils of these treatments indicated that ACM could limit MC-LR degradation in soils and thus promote its bioaccumulation in the vegetables. MC-LR bioaccumulation could cause toxicity to the vegetables, with the highest toxic effects observed in ACM treatment. Similarly, bioaccumulation of MC-LR in the edible parts of the leaf-vegetables posed 1.1~4.8 fold higher human health risks in ACM treatment than in IPW and CPS treatments. The findings of this study highlighted a great concern on applications of cyanobacterial manure.
Reasonable nutrient and water management is effective ways to improve productivity and biodiversity of degraded grasslands. However, little is known about the effects of nutrient and water addition ...on soil inorganic phosphorus (P) fractions in old-field grasslands. Based on a field experiment with nutrient addition (N: 10 g·m
·a
, P: 10 g·m
·a
) and water addition (180 mm water irrigated during plant growing season) in Duolun County, Inner Mongolia in 2005, we examined the changes of inorganic P fractions and Olsen-P contents in the topsoil (0-10 cm). Results showed that 11-year P addition significantly increased total inorganic P (TIP) content, and that exogenous P was mostly transformed into calcium phosphate (Ca-P: 62.6%-69.2%), and then into aluminium phosphate (Al-P: 19.9%-25.1%), ferric phosphate (Fe-P) and occluded P (O-P). Phosphorus incorporated with nitrogen (N) addition significantly increased Fe-P and Al-P contents by declining soil pH and activating Fe
and Al
in soil. Water addition alone signifi
We summarized the effects of fertilization and water addition on some soil properties and plant community characteristics in a long-term field experiment established in 2005 in a degraded grassland ...in Duolun, Inner Mongolia, China. The results showed that nitrogen (N) addition resulted in surface soil acidification and decreased acid buffering capacity, increased the availability of carbon (C), N, phosphorus (P), sulfur (S) and DTPA-extractable iron (Fe), manganese (Mn), and copper (Cu) contents, depleted the sum of base cations calcium (Ca), magnesium (Mg), potassium (K) and sodium (Na), decreased the diversity of soil microbial community. Nitrogen addition enhanced the uptake of N, P, S, K, Mn, Cu and Zn by plants, while inhibited plant Fe uptake, but with no effect on the uptake of Ca or Mg. Nitrogen addition increased aboveground net primary productivity (ANPP) but declined plant species diversity and community stability. Phosphorus addition alone increased total P and Olsen-P contents and fungal abundanc
In this study, we measured the responses of soil bacterial diversity and community structure to nitrogen (N) and water addition in the typical temperate grassland in northern China. Results showed ...that N addition significantly reduced microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) under regular precipitation treatment. Similar declined trends of MBC and MBN caused by N addition were also found under increased precipitation condition. Nevertheless, water addition alleviated the inhibition by N addition. N addition exerted no significant effects. on bacterial α-diversity indices, including richness, Shannon diversity and evenness index under regular precipitation condition. Precipitation increment tended to increase bacterial α-diversity, and the diversity indices of each N gradient under regular precipitation were much lower than that of the corresponding N addition rate under increased precipitation. Correlation analysis showed that soil moisture, nitrate (NO3(-)-N) and ammonium (NH4+-N)
Biodiversity can effectively actuate ecosystem multifunctionality, and the relationships primarily depend on the circumstances. However, the relative functional importance of particular components in ...complex biocoenosis, such as abundant and rare taxa, influencing soil multifunctionality changes across environmental gradients and remains limited understanding. Here, 152 independent soil samples from aridity (from 0.47 to 0.97) and elevation (from 142 to 2766 m a.s.l.) gradients across steppes of northern China were collected and analyzed to obtain information of soil bacterial community and soil functional properties, which were further utilized to evaluate how the relationships between the diversities of abundant and rare species and soil multifunctionality respond to changes in aridity and elevation. At aridity and elevation levels of ~0.85 and ~1100 m a.s.l., respectively, abrupt variations of the connections between soil multifunctionality and diversities of abundant or rare taxa occurred. Moreover, the results revealed a significantly positive effect of richness of abundant taxa on soil multifunctionality in the less arid and higher elevation areas, whereas a strongly positive relationship was exhibited between diversity of rare species and soil multifunctionality in the more arid and higher elevation regions. Specially, regardless of higher or lower aridity levels, both contributions of abundant and rare taxa to soil multifunctionality were extremely weak in the lower elevation regions. Our study highlights the importance of aridity and elevation impacting the contributions of abundant and rare taxa in regard to soil multifunctionality, which can positively provide some theoretical bases for promoting ecosystem sustainability and productivity under global climate change.
•Abrupt shifts occurred at aridity and elevation levels of about 0.85 and 1100 m a.s.l., respectively.•Abundant taxa showed a positive effect in the less arid and higher elevation areas.•Rare taxa exhibited a positive effect in the more arid and higher elevation areas.•Both abundant and rare taxa showed weak effects in the lower elevation regions.
We experimentally present an acoustic metasurface (AMS) with sub-wavelength thickness based on the meta-molecule consisting of eight different sized double-split hollow spheres (DSHSs). By designing ...the discontinuous phase profile covered 2π span induced by the DSHSs, the AMS can manipulate the reflected acoustic waves in a way that could not be imitated by natural materials. Both simulations and experiments show that the AMS can realize anomalous reflection, i.e., a normal incident wave can be reflected into an oblique direction. Moreover, the reflection angle can be flexible controlled by mechanically tuning the spatial distance of the DSHSs in the AMS, which is consistent with the generalized Snell׳s law.
•We presented an acoustic metasurface (AMS) consisting of double-split hollow spheres.•Both simulations and experiments show that the AMS can realize anomalous reflection.•The reflection angle can be flexible controlled by mechanically tuning the spatial distance of the DSHSs in the AMS.
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