Phosphorus (P) is an indispensable element for all life on Earth and, during the past decade, concerns about the future of its global supply have stimulated much research on soil P and method ...development. This review provides an overview of advanced state‐of‐the‐art methods currently used in soil P research. These involve bulk and spatially resolved spectroscopic and spectrometric P speciation methods (1 and 2D NMR, IR, Raman, Q‐TOF MS/MS, high resolution‐MS, NanoSIMS, XRF, XPS, (µ)XAS) as well as methods for assessing soil P reactions (sorption isotherms, quantum‐chemical modeling, microbial biomass P, enzymes activity, DGT, 33P isotopic exchange, 18O isotope ratios). Required experimental set‐ups and the potentials and limitations of individual methods present a guide for the selection of most suitable methods or combinations.
Understanding human impacts on drylands is crucial in a global scenario of forest degradation and biodiversity loss. This study analyzed foliar concentrations of nitrogen (N) and phosphorous (P) in ...the Brazilian seasonally dry tropical forests (Caatinga). Foliar patterns of N, P, and the N/P ratio were assessed both within and among botanical families. To do this, 10 plots were established in an anthropized area and 10 in a conserved area. Within each plot, leaves from all tree species and soil samples from four random points were collected. Stoichiometric analyses were performed on the leaves of 136 trees from 14 botanical families. Significant differences were observed in soil P concentrations, organic matter content, and cation exchange capacity, with the highest values found in the conserved area. Foliar N and P concentrations and N/P were also higher in the conserved area for the F+ (nitrogen-fixing Fabaceae), F- (non-nitrogen-fixing Fabaceae), and NF (non-Fabaceae) groups, indicating greater efficiency in nutrient retention and cycling. When comparing species found in both areas, Aspidosperma pyrifolium (NF), Bauhinia forficata (F-), and Mimosa ophthalmocentra (F+) showed significant differences in foliar N concentrations and foliar P (for A. pyrifolium and B. forficata only). Degradation of the Caatinga directly impacts nutrient cycling.
•Foliar N and P concentrations, and N/P ratio, are higher in the conserved area.•Species richness in conserved area influences the higher soil nutrient production.•Anthropogenic impacts reduce Caatinga species richness and nutrient availability.•Fixing Fabaceae efficiently absorb foliar N and P in this semi-arid region.•Degradation of the Caatinga directly impacts nutrient cycling.
Land application of farmyard manure (FYM) is a widespread agronomic practice used to enhance soil fertility, but its long-term effects on soil microbial carbon (C) and nitrogen (N) cycling have not ...been investigated in detail. Topsoils (0–23 cm) and subsoils (23–38 cm) were collected from a field trial on a sandy-textured soil where FYM had been applied at high (50–25 t ha−1 yr−1, 28 yr) and low rates (10 t ha−1 yr−1, 16 yr), and compared to soil treated only with synthetic NPK fertilisers. The turnover rate of key components of soil organic matter (SOM; proteins, peptides, amino acids, cellulose, and glucose) were evaluated by 14C labelling and measuring cellobiohydrolase, β-glucosidase, β-1,4-N-acetylglucosaminidase, L-leucine aminopeptidase, protease, and deaminase activities, whereas gross NH4+ and NO3− production and consumption were determined by 15N-isotope pool dilution. Microbial communities were determined using phospholipid fatty acid (PLFA) profiling. Our results indicate that long-term FYM addition significantly enhanced the accumulation of soil C and N, soil organic N (SON) turnover, exoenzyme activity, and gross NO3− production and assimilation. Rates of protein, peptide, and amino acid processing rate were 169–248, 87–147, and 85–305 mg N kgDWsoil−1 d−1, respectively, gross NH4+ and NO3− production and consumption were 1.8–5.8 mg N kgDWsoil−1 d−1, and the highest rates were shown under the high FYM treatment in topsoil and subsoil. The half-life of cellulose and glucose decomposition under the high FYM treatment were 16.4% and 31.0% lower than them in the synthetic NPK fertiliser treatment, respectively, indicating higher rates of C cycling under high manure application as also evidenced by the higher rate of CO2 production. This was ascribed to an increase in microbial biomass rather than a change in microbial community structure. Based on the high pool sizes and high turnover rate, this suggests that peptides may represent one of the dominant forms of N taken up by soil microorganisms. We conclude that long-term FYM application builds SOM reserves and induces faster rates of nutrient cycling by boosting microbial biomass rather than by changing its community composition.
•The influence of manure application on soil C/N cycling was evaluated.•14C labeling and 15N-pool dilution techniques were used.•Manure application significantly affects C/N cycling in soil by boosting microbial biomass.•Peptides may be important for terrestrial cycling and supply of N.
Microplastics (MPs, <5 mm in diameter) have been widely recognized as a critical environmental issue due to their extensive use and low degradation rate. Based on current evidence, our aim is to ...evaluate whether MPs represent an emerging threat to plant-soil health in agroecosystems. We assess the ecological risks to plant-microbe-soil interactions associated with MPs and discuss the consequences of MPs on soil carbon (C), nutrient cycling, as well as greenhouse gas emissions in agroecosystems. We also identify knowledge gaps and give suggestions for future research. We conclude that MPs can alter a range of key soil biogeochemical processes by changing its properties, forming specific microbial hotspots, resulting in multiple effects on microbial activities and functions. Mixed effects of MPs on plant growth and performance can be explained by the direct toxicity of MPs or the indirect alteration in soil physical structures and microbial communities (i.e. symbiotic arbuscular mycorrhizal fungi). Because of the diverse nature of MPs found in soils, in terms of polymer type, shape and size, we also see differing effects on soil organic matter (SOM) decomposition, nutrient cycling, and greenhouse gases production. Importantly, increased bioavailable C from the decomposition of biodegradable MPs, which enhances microbial and enzymatic activities, potentially accelerates SOM mineralization and increases nutrient competition between plant and microbes. Thus, biodegradable MPs appear to pose a greater risk to plant growth compared to petroleum-based MPs. Although MPs may confer some benefits in agroecosystems (e.g. enhanced soil structure, aeration), it is thought that these will be far outweighed by the potential disbenefits.
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•MPs can alter rhizodeposition input and soil organic matter decomposition.•Effects on soil C and nutrient cycling depend on MP types, concentration, size, and shape.•Nano-sized MPs can accumulate in roots and be transported to the shoot.•Bio-based MPs can exert strong negative effects on plant by increasing nutrient competition.
The crucial biogeochemical processes such as carbon and nutrient cycling are increasingly altered at the ecosystem scale by global environmental changes. Although soil extracellular enzyme activities ...(EEAs) play a critical role in biogeochemical processes, the global patterns of soil EEAs in a changing world remain elusive. Here, we synthesized eight EEAs involved in carbon (C), nitrogen (N) and phosphorus (P) acquisition in response to seven global change factors based on 132 peer-reviewed papers. Our results showed that elevated CO2 concentration had no significant effects on soil EEAs. Nitrogen addition stimulated C-acquisition (9.1%) and P-acquisition (9.9%) EEAs, but suppressed oxidase activity (−6.8%). Phosphorus addition decreased P-acquisition EEA (−19.8%), while combined N and P addition increased C-acquisition EEA (30.7%). Moreover, decrease in precipitation dramatically suppressed oxidase activity (−47.2%), increase in precipitation marginally stimulated N-acquisition EEA (16.7%), while warming significantly decreased oxidase activity (−10.9%) and had minor positive effect on hydrolytic enzymes. Overall, our results provide some evidence (with exceptions) for the resource allocation theory of microbial enzyme production, and indicate that EEAs are generally more sensitive to nutrient addition than to atmospheric and climate change. We have shown that global environmental changes can alter EEAs, which have implications for soil carbon storage, nutrient cycling, and plant productivity. Further research is needed to elucidate the underlying mechanisms driving the responses of EEAs to global change and to collect data from particularly non-forest ecosystems (e.g., wetland, tundra and desert) and global-change drivers (other than N addition) that lack of EEA data. Our synthesis of the responses of soil enzyme activities to global-change drivers can be used to develop better representations of microbial processes in ecosystem and earth system models.
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•We performed a global meta-analysis of soil enzymes in response to global change drivers.•Data include eight enzymes and seven drivers from field experiments in natural ecosystems.•Enzymes are more sensitive to nutrient addition than to atmospheric and climate change.
Microorganisms mediate nutrient cycling in soils, and thus it is assumed that they largely control responses of terrestrial ecosystems to anthropogenic nutrient inputs. Therefore, it is important to ...understand how increased nitrogen (N) and phosphorus (P) availabilities, first, affect soil prokaryotic and fungal community composition and second, if and how changes in the community composition affect soil element cycling. We measured soil microbial communities and soil element cycling processes along a nine-year old experimental N-addition gradient partially crossed with a P-addition treatment in a temperate grassland. Nitrogen addition affected microbial community composition, and prokaryotic communities were less sensitive to N addition than fungal communities. P addition only marginally affected microbial community composition, indicating that P is less selective than N for microbial taxa in this grassland. Soil pH and total organic carbon (C) concentration were the main factors associated with prokaryotic community composition, while the dissolved organic C-to-dissolved N ratio was the predominant driver of fungal community composition. Against our expectation, plant biomass and plant community structure only explained a small proportion of the microbial community composition. Although microbial community composition changed with nutrient addition, microbial biomass concentrations and respiration rates did not change, indicating functional redundancy of the microbial community. Microbial respiration, net N mineralization, and non-symbiotic N2 fixation were more strongly controlled by abiotic factors than by plant biomass, plant community structure or microbial community, showing that community shifts under increasing nutrient inputs may not necessarily be reflected in element cycling rates. This study suggests that atmospheric N deposition may impact the composition of fungi more than of prokaryotes and that nutrient inputs act directly on element-cycling rates as opposed to being mediated through shifts in plant or microbial community composition.
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•Nutrient inputs differentially impacted microbial communities and element cycling.•Soil pH and total organic carbon were main drivers of prokaryotic communities.•DOC:DN ratio was the predominant driver of fungal community composition.•Element cycling was controlled by abiotic factors, not by microbial community change.•Microbial community change may not necessarily change ecosystem functioning.
Microplastic surfaces could be colonized by microorganisms and form biofilms in aquatic ecosystem, which can participate in the nitrogen (N) and phosphorus (P) cycles. In this work, polypropylene ...squares were deployed in a pond for 30 days for microplastic biofilms colonization and then were transported to indoor microcosms at an environmental relevant level to study their effects on N and P cycling. Results showed that microplastic biofilms could accelerate ammonia and nitrite oxidation as well as denitrification. Presence of microplastic biofilms accumulated P temporarily and increased alkaline phosphatase activities (APA) in the system. Later in the experiment, disintegration of matured biofilms released N and P into the water. Mass balance calculation suggested possible N input caused by biological nitrogen fixation. Our results demonstrated that microplastics associated biofilms have the ability to alter the N and P cycling processes in aquatic system. However, additional works are required to further quantify the extent of such impact.
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•Microplastic biofilms can impact N and P cycles in aquatic ecosystems.•N and P can be release to water due to disintegration of matured biofilms.•Microplastic biofilms harbor distinctive algae community from water.•Nitrate addition showed minor impact in systems with or without microplastic biofilms.
•Sludge contains recyclable and agronomical valuable macro and micronutrients.•Sludge application on cropland reduces need of synthetic fertilizers, causing sustainability of agriculture.•Sludge can ...contain harmful organic and inorganic contaminants.•In some cases, sludge application on cropland can contaminate water, soil & food chain.•Interaction of inorganic and organic compounds with environment should be investigated for long-term risks.
Digested sludge is a good source of plant nutrients. However, depending on the feedstock, it might contain heavy metals, metalloids, organic compounds, pathogens, and pharmaceuticals, which can cause adverse effects on crop growth and contaminate the groundwater, soil, and food chain.
The aim of this review is to focus on the potential risks of inorganic and organic contaminants to plant growth, soil, groundwater, and consequently the food chain and environment related to the utilization of digested sludge as a fertilizer on cropland.
Inorganic compounds, such as metals and metalloids, in sludge can occasionally cause reductions in soil microbial biomass. In general, the uptake of metals and organic contaminants does not appear to cause a significant hazard to the plants and the concentrations do not surpass the maximum values allowed in soil. Organic compounds, harmful for human health or the environment, are to a large extent decomposed or volatilized from the land treated with sludge, which decreases their leaching into the environment. Many of the organic compounds are lipophilic and can be bound to soil organic matter. In conclusion, the application of sludge on cropland might be a sustainable management practice; however, further investigations are needed to determine the accumulation and persistence of possible hazardous emerging chemicals and pathogens in the environment and formation of harmful intermediate reaction of inorganic and organic compound products.
•Soil physicochemical property and microbial biomass decline with forest conversion.•Fungal α diversity decrease with a decline of soil property and microbial biomass.•The decline in plant and fungi ...diversity reduced enzyme activity.•Fungal composition and structure were deeply affected by forest conversion.•Forest conversion may have a negative influence on C-, N-, and P-cycling.
Considerable natural or secondary forests have been converted to plantations in response to the growing needs for timber, paper, and fuel. Soil fungal communities are sensitive to ecosystem transformation and play an important role in aboveground-belowground linkages and biogeochemical cycling. However, the effect of forest conversion on fungal community structure and functions and driving mechanisms remains unclear. We investigated the response of soil fungal communities and the corresponding change in soil physicochemical biological properties and enzymatic activities to the natural broad-leaved forest (NBF) converted to the Chinese fir (Cunninghamia lanceolata) plantation (CFP) in subtropical China with ITS rRNA amplicon sequencing. Soil physicochemical properties, microbial biomass, fungal alpha diversities, and enzymatic activities decreased with forest conversion, including pH, soil water content, soil organic carbon, available phosphorus, total nitrogen, nitrate nitrogen, microbial biomass carbon and nitrogen, urease, protease, and acid phosphatase. Fungal community composition and structure were also strongly affected by forest conversion. Ascomycota had a higher read abundance in the NBF, but Basidiomycota showed a higher read abundance in the CFP. The read abundance of saprotroph and arbuscular mycorrhizal fungi increased with forest conversion, while that of ectomycorrhizal fungi decreased. Some fungal guilds—dung saprotrophs, lichenized fungi, endophytes, and lichen parasites—were even nearly lost in the CFP. These changes in fungal communities are all closely correlated to soil physicochemical properties, microbial biomass, and enzymatic activities. Overall, our study emphasizes the negative effect of the NBF conversion to the CFP on C, N, and P cycling mediated by fungi—and recommends replacing monoculture coniferous forests with mixed forests in reforestation to improve soil degradation.
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