Changes In Soil Microbial Activity Research Articles

Effects of Organic Fertilizer of Kitchen Waste on Soil Microbial Activity and Function

Changes in soil microbial activity and ecological function can be used to assess the level of soil fertility and the stability of ecosystems. To assess the fertility and safety of organic fertilizer of kitchen waste (OFK), soils containing 0% (CK), 1%, 3%, and 5% OFK were cultured, and the physical, chemical, and microbial properties of the soils were measured dynamically with routine agrochemical analysis measures and amplicon sequencing. The results showed that compared with those in CK, the contents of organic matter, available phosphorus, available potassium, NH4+-N, and NO3--N in soils with OFK increased by 23.80%-35.13%, 13.29%-29.72%, 16.91%-39.37%, 164.7%-340.2%, and 28.56%-32.71%, respectively. The activities of hydrolases related to the cycle of carbon, nitrogen, and phosphorus (α-glucosidase, leucine aminopeptidase, acid phosphatase, etc.) were also significantly higher than those of the CK treatment. OFK stimulated the growth of soil microorganisms and increased the carbon content of the microbial biomass. The amplicon sequencing analysis found that the microbial community structures of different treatments were significantly different at both the class and genus levels. In addition, it was found that the abundance of beneficial microbes in the soils with OFK increased, whereas pathogenic microbes decreased. RDA results confirmed that soil properties (including soil pH, organic matter, available nutrients, and microbial biomass) had a significant impact on microbial community structure. The results of investing bacterial community based on PICRUSt and FAPROTAX revealed that the function of the soil bacterial community was similar in the four treatments, but OFK supply significantly improved the microbial carbon utilization and metabolic ability. Moreover, by using the FUNGuild software, we found that the application of OFK increased the proportion of saprotroph-symbiotroph and symbiotroph and stimulated the growth of ectomycorrhizal fungi-undefined saprophytic fungi but inhibited plant and animal pathogenic fungi in soil. These results implied that OFK could promote the establishment of symbiotic relationships and inhibit the growth of pathogenic fungi. In summary, OFK could improve soil fertility and hydrolase activity, stimulate the growth of beneficial microorganisms, and defend against pathogens, indicating a promising use as safe and efficient organic fertilizer.

Changes in soil microbial activity and their linkages with soil carbon under global warming

Soil microorganisms play an important role in the carbon (C) cycling of terrestrial ecosystems. However, changes in soil microbial activity and their linkages with soil C under global warming remain unclear. Here, a global meta-analysis of 1272 pairwise observations was conducted to explore the effects of warming on soil microbial activity and their linkages with soil C under different warming duration (0–5, 5–10, and > 10 yr), warming magnitudes (<2 and ≥ 2 °C), ecosystem types (cropland, grassland, shrub, and forest), mean annual precipitation (MAP: 0–400, 400–800, and > 800 mm), and mean annual temperature (MAT: 0–5, 5–10, 10–20, and > 20 °C). Warming overall positively affected soil microbial C, bacteria diversity, fungi richness, and soil C content. Moreover, the positive effects of warming on microbial and soil C gradually weakened and even inhibited with increasing warming duration and magnitudes. Additionally, the soil microbial biomass and microbial diversity shifted from positive to negative relationships with increasing MAP and MAT. Warming mainly affected soil microbial biomass and bacteria diversity in grasslands. Finally, warming induced significant linear relationships of microbial variables with soil C. In conclusion, our results indicated that warming had significant influences on soil microbial activity and soil C cycling, depending on warming duration, magnitudes, ecosystem types, MAP, and MAT. Such findings underscore the important effects of warming on soil C cycling in global ecosystems, which may improve our ability to predict soil biogeochemical cycles in this biome.

Using soil enzyme Vmax as an indicator to evaluate the ecotoxicity of lower-ring polycyclic aromatic hydrocarbons in soil: Evidence from fluorescein diacetate hydrolase kinetics

Fluorescein diacetate hydrolase (FDA hydrolase) is a reliable biochemical biomarker of changes in soil microbial activity and quality. However, the effect and mechanism of lower-ring polycyclic aromatic hydrocarbons (PAHs) on soil FDA hydrolase are still unclear. In this work, we investigated the effects of two typical lower-ring PAHs, naphthalene (Nap) and anthracene (Ant), on the activity and kinetic characteristics of FDA hydrolases in six soils differing in their properties. Results demonstrated that the two PAHs severely inhibited the activities of the FDA hydrolase. The values of Vmax and Km dropped by 28.72–81.24 % and 35.84–74.47 % at the highest dose of Nap, respectively, indicating an uncompetitive inhibitory mechanism. Under Ant stress, the values of Vmax decreased by 38.25–84.99 %, and the Km exhibited two forms, unchanged and decreased (74.00–91.61 %), indicating uncompetitive and noncompetitive inhibition. The inhibition constant (Ki) of the Nap and Ant ranged from 0.192 to 1.051 and 0.018 to 0.087 mM, respectively. The lower Ki of Ant compared to Nap indicated a higher affinity for enzyme-substrate complex, resulting in higher toxicity of Ant than Nap to soil FDA hydrolase. The inhibitory effect of Nap and Ant on soil FDA hydrolase was mainly affected by soil organic matter (SOM). SOM influenced the affinity of PAHs with enzyme-substrate complex, which resulted in a difference in PAHs toxicity to soil FDA hydrolase. The enzyme kinetic Vmax was a more sensitive indicator than enzyme activity to evaluate the ecological risk of PAHs. This research offers a strong theoretical foundation for quality control and risk evaluation of PAH-contaminated soils through a soil enzyme-based approach.

Phosphate fertilization and bioactivator influences on fractions of organic matter and soil microbial biomass

Soil organic matter is considered a potential source of phosphorus (P) for plants because of biological cycling. Bioactivators are characterized as tools that can help soil microbial activity and the availability of P demanded by plants. The objective of this study was to evaluate the influence of the use of bioactivators and phosphate fertilization on the activity of soil microbial biomass and humified fractions of organic matter. The experimental design was completely randomized in a factorial scheme (6 × 2), with the first factor consisting of six doses of phosphorus applied to the soil (0, 30, 60, 90, 120, and 150 kg ha-1 of P2O5), using triple superphosphate as the source, and the second factor being the presence or absence of soil and plant bioactivator application, with four replications. The evaluated characteristics were soil microbial biomass carbon (SMBC), soil basal respiration (SBR), microbial biomass nitrogen (MBN), metabolic quotient (qCO2), microbial quotient (qmic), total organic carbon (TOC), fulvic acid fraction carbon (FAC), humic acid fraction carbon (HAC), and humin fraction carbon (HUMC). The use of soil and plant bioactivators and mineral phosphate fertilizer promoted changes in soil microbial activity. Increasing doses of phosphate fertilization promoted a reduction in the carbon characteristics of microbial biomass and basal soil respiration in the presence or absence of soil and plant bioactivators. Moreover, the use of bioactivator promoted higher averages for soil microbial biomass carbon, soil basal respiration, metabolic quotient, humic acid and humin and reduced the levels of microbial quotient, total organic carbon and fulvic acid.

Carbon and Nitrogen Dynamics in Mexican Management Forest: Simulation of Biomass Harvesting and C and N Amendments

AbstractSustainable silvicultural management requires the maintenance of long-term ecosystem processes. We used the CENTURY model to simulate the impact of wood extraction and organic amendments on aboveground biomass, carbon (C) storage, and the availability of nitrogen (N) in the two dominant silvicultural methods in Mexico: the silvicultural development method (SDM) and irregular forest management (IFM). The values of the mean absolute percentage error for the SDM and IFM were 2.1% and 3.3% for C in aboveground biomass, 5.7% and 5.0% for soil organic carbon (SOC), and 14.9% and 21.6% for N, respectively. Simulation for the SDM (1967–2068) suggested a reduction of ~7% in C in soil, microbial biomass, and litter, 9% in aboveground biomass C, and ~20% in the mineral N available. For IFM, the simulation (2009–2019) suggested a reduction of 14% in the accumulation of aboveground biomass and 13% in the mineral N available. Simulation of the adoption of management practices suggested that N mineral availability would increase by 2%–3% without drastically reducing the SOC, improving aboveground biomass production by ~7%, in each management system.Study ImplicationsIn Mexico, current silvicultural management is causing alterations in the biological and chemical processes of the soil, but the future impacts on the production of forest wood and loss of fertility cannot be estimated by direct measurements. We simulated two silvicultural management alternatives with two rotation cycles and measured the response in terms of SOC, nitrogen availability, and aboveground biomass. The model shows that improving forest residue management by adding organic amendments to the soil would counteract changes in soil microbial activity, nitrogen availability, SOC, and aboveground biomass in the future. Managers should consider this information to reorient current crop residue management to achieve the objectives and the sustainability of forest management in Mexican temperate forests.

Changes in Soil Microbial Activity, Bacterial Community Composition and Function in a Long-Term Continuous Soybean Cropping System After Corn Insertion and Fertilization.

Corn-soybean rotation and fertilization are common practices improving soil fertility and crop yield. Their effects on bacterial community have been extensively studied, yet, few comprehensive studies about the microbial activity, bacterial community and functional groups in a long-term continuous soybean cropping system after corn insertion and fertilization. The effects of corn insertions (Sm: no corn insertion, CS: 3 cycles of corn-soybean rotations and CCS: 2 cycles of corn-corn-soybean rotations) with two fertilization regimes (No fertilization and NPK) on bacterial community and microbial activity were investigated in a long-term field experiment. The bacterial communities among treatments were evaluated using high-throughput sequencing then bacterial functions were predicted based on the FaProTax database. Soil respiration and extracellular enzyme activities were used to assess soil microbial activity. Soil bacterial community structure was significantly altered by corn insertions (p < 0.01) and fertilization (p < 0.01), whereas bacterial functional structure was only affected by corn insertion (p < 0.01). The activities of four enzymes (invertase, β-glucosidase, β-xylosidase, and β-D-1,4-cellobiohydrolase) involved in soil C cycling were enhanced by NPK fertilizer, and were also enhanced by corn insertions except for the invertase and β-xylosidase under NPK fertilization. NPK fertilizer significantly improved soil microbial activity except for soil metabolic quotient (qCO2) and the microbial quotient under corn insertions. Corn insertions also significantly improved soil microbial activity except for the ratio of soil induced respiration (SIR) to basal respiration (BR) under fertilization and the qCO2 was decreased by corn insertions. These activity parameters were highly correlated with the soil functional capability of aromatic compound degradation, which was the main predictors of bacterial functional structure. In general, the combination of soil microbial activity, bacterial community and corresponding functional analysis provided comprehensive insights into compositional and functional adaptations to corn insertions and fertilization.

Changes in soil carbon and nitrogen accessibility with the application of biochars with different morphological and physical characteristics

The recent literature indicates that, depending on the feedstocks and pyrolysis temperature, biochar can be a good source of nutrients. On the contrary, some biochars are not good sources of available carbon and other nutrients, but their porous structure seems to be a suitable microenvironment for microbial colonization. We investigated the response of soil biological parameters, microbial biomass carbon and nitrogen (MBC and MBN), in relation to mobile N species. Five different biochars were produced at different temperatures (300, 350, 400, 450, and 500 °C) from the same feedstock (woodchips). The physicochemical and morphological characteristics of the individual biochar samples were described, and incubation was carried out with the application of 2% biochar to two different soil types (luvisol and fluvisol). The addition of 2% biochar did not change the pH in the slightly acid soils used in the experiment, in spite of the alkaline character of biochar. The increasing amounts of total and nitrate-available nitrogen during the experiment are probably related to changes in soil microbial activity. The amount of soluble carbon was constant during the experiment, confirming its stability in the soil, most likely because of the high amount of lignin in the feedstock. The influence of biochar on the soil microbiome was determined on the basis of the concentrations of MBC and MBN. Microbial biomass was increased in both soils treated with biochar produced at lower temperatures. The physicochemical characteristics of the biochar as well as the sorption behavior of N-NO3− and N-NH4+ indicate that at a pyrolysis temperature of 400 °C, biochar properties change substantially. However, these findings are only valid for biochar produced from woodchips, and the long-term effects of biochar application on soil properties need to be investigated in further studies.

Disentangling the direct and indirect effects of cropland abandonment on soil microbial activity in grassland soil at different depths

Cropland abandonment strongly affects plant-soil interactions. However, knowledge remains limited about how the production and diversity of plants and soil physicochemical parameters drive changes in soil microbial activity (such as microbial biomass, respiration, and enzyme activity) after cropland abandonment. Here, we investigated a grassland restoration chronosequence (0–30 years) to determine the dynamics of soil microbial biomass, respiration, and enzyme activity in the Loess Hilly, Region (China). Overall, cropland abandonment caused an increase in soil microbial activity primarily in the 0–20 cm soil layers. The metabolic quotient in the 0–10 cm layer decreased linearly with time since abandonment (recovery years). Structural equation models showed that recovery years directly and indirectly affected changes to soil microbial activity. Plant species richness, aboveground biomass, and soil organic carbon explained a large proportion of the variability in soil microbial activity in the 0–20 cm layer. However, the variability in soil microbial activity was mostly explained by plant species richness, belowground biomass, and soil total nitrogen in the 20–50 cm layers. Our results indicate that during recovery after cropland abandonment, changes in soil microbial activity are driven by plant characteristics and soil physicochemical parameters, with different drivers at different soil depths.

Substitution of Norway spruce for Douglas-fir: changes of soil microbial activities as climate change induced shift in species composition – a case study

Abstract Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) is the most common utilized introduced tree species in the tem-is the most common utilized introduced tree species in the temperate zone, planted in many European countries. Also, in the Czech Republic it represents the most planted exotic species as well. Its planted area exceeds 6,000 ha and represents 0.25% of the forest area of the country. In the last years, this species is supposed as convenient substitution for declining Norway spruce (Picea abies [L.] Karst.) stands under current climatic change (extreme drought, bark beetle outbreak). The changed species composition affects also soil dynamic processes, including litter decomposition and transformation. In the presented study, the respiration rate and nitrification intensity were compared in the stand parts dominated by Norway spruce and Douglas-fir in comparable site conditions (410 m a.s.l., 650 mm, 8 ºC, gleyic Luvisol, fresh oak-fir site with Oxalis acetosella, age 97 years). Analyses were performed in laboratory conditions by standard methods determining actual (basal) and potential respiration activity and intensity of ammonia and nitrate ion production. Admixture of Douglas-fir considerably intensified decomposition activities (soil respiration) and profoundly increased the nitrification rate in the surface humus and uppermost mineral soil layer – Ah horizon. Increased interest in the Douglas-fir silviculture needs increased care for forest soil dynamics with respect of nitrogen balance.

Determining the Effects of Animal Decomposition on Soil Microbes

When animals die and decompose, they undergo various taphonomic stages eventually breaking down and becoming one with the earth again. Factors that affect decomposition have been studies but there is very little literature on the effects of animal decomposition on soil microbial communities. In this project, we studied the changes in soil microbial activity at sites of animal decomposition during various taphonomic stages. Soil microbial activity was calculated using Biolog 96-well ecoplates, incubated at 30℃, with readings at 0, 24, and 72 hours. Preliminary tests were conducted at a known gravesite where a carcass decomposed last spring. Soil samples were collected from the head, abdominopelvic region, and an off-site control 2 meters away from the grave. Initially, the soil samples underwent three testing methods. Samples were tested with fresh, frozen, and dried soil. Fresh soil yielded the highest microbial activity followed by the frozen soil; dried soil did not yield any microbial activity. Preliminary results of the fresh soil showed a high level of microbial activity at the one-year-old gravesite compared to the off-site control. The percent functional diversity at 72 hours, for the fresh soil samples, were as follows: Head- 67.7%, Abdominopelvic- 58.1%, and the off-site control- 54.8%. Future research includes testing six fresh animal specimens at one-week intervals.

Changes in soil microbial activity, essential oil quantity, and quality of Thai basil as response to biofertilizers and humic acid

Thai basil (Ocimum basilicum var. thyrsiflorum) is an important medicinal plant that used in pharmaceutical, cosmetic, and food industries. In order to evaluate the effect of biofertilizers and humic acid on secondary metabolites of Thai basil, a factorial experiment; fertilizer treatments (Control, NF (nitrogen-fixing bacterium), PS (phosphate solubilizing bacteria), combination of NF and PS, chemical fertilizer, combination of NF and PS + 50% chemical fertilizer) and humic acid (0 and 20 kg ha−1) was conducted. The soil microbial respiration and carbon biomass, soil organic matter, leaf nitrogen and phosphorus elements, number and size of glandular trichomes as well as the quantity and quality of the essential oil were evaluated. Results showed that the application of biofertilizers greatly caused to increase 60% in soil microbial respiration (1.11 CO2 g−1 dry soil day−1) and 3-fold in carbon biomass (117.47 mg C 100 g−1 dry soil) than control. The use of humic acid enhanced the soil organic matter by 2-fold (1.15%) more than control. The highest value of phosphorus element (0.67%), size of glandular trichomes in upper (411.11 μm2) and lower (419.31 μm2) surfaces, and essential oil content (2.81%) were obtained in the inoculation of plants by PS and the lowest values were observed in control. The combination of NF and PS + 50% chemical fertilizer led to increment 45% in the nitrogen element (3.42%), 1.5-fold in number of glandular trichomes in upper (5.03 number mm−2) and lower (6.22 number mm−2) surfaces and 80% essential oil yield (7.89 g m−2) compared to the control. The maximum amount of methyl chavicol (66.26%), eucalyptol (12.98%), linalool (5.42%), and β-pinene (2.15%) was recorded in combination of NF and PS + 50% chemical fertilizer and the minimum amounts were detected in control. Despite the positive effect of the simultaneous application of humic acid and biofertilizers treatment on the soil organic matter, nitrogen element and some major oil components, humic acid had no significant impact on the phosphorus concentration, size of glandular trichomes and essential oil content and yield. Further investigation is needed to use humic acid in plant nutrition management. In conclusion, combination of NF and PS + 50% chemical fertilizer can be recommended as a suitable solution to reduce the demand for chemical fertilizers and their environmental hazards in warm regions.

Effects of Mixing Feldspathic Sandstone and Sand on Soil Microbial Biomass and Extracellular Enzyme Activities—A Case Study in Mu Us Sandy Land in China

Microbial biomass, extracellular enzyme activity, and their stoichiometry in soil play an important role in ecosystem dynamics and functioning. To better understand the improvement of sand soil quality and the limitation of soil nutrients after adding feldspathic sandstone, we investigated changes in soil microbial activity after 10 months of mixing feldspathic sandstone and sand, and compared the dynamics with soil properties. We used fumigation extraction to determine soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), and microplate fluorometric techniques to measure soil β-1,4-glucosidase (BG), β-1,4-xylosidase (BX), β-D-cellobiohydrolase (CBH), N-acetyl-β-glucosaminidase (NAG), and Alkaline phosphatase (AKP). We also measured soil organic carbon (SOC), pH, electrical conductivity (EC), soil inorganic carbon (SIC), and soil water content (SWC). Our results showed that the soil microbial biomass C, N, P, and individual extracellular enzyme activities significantly increased in mixed soil. Similarly, the soil microbial biomass C:N, C:P, N:P, MBC:SOC, and BG:NAG significantly increased by 54.3%, 106.3%, 33.1%, 23.0%, and 65.4%, respectively. However, BG:AKP and NAG:AKP decreased by 19.0% and 50.3%, respectively. Additionally, redundancy analysis (RDA) and Pearson’s correlation analysis showed that SWC, SOC, porosity and field capacity were significantly associated with soil microbial biomass indices (i.e., C, N, P, C:N, C:P, N:P in microbial biomass, and MBC:SOC) and extracellular enzyme activity metrics (i.e., individual enzyme activity, ecoenzymatic stoichiometry, and vector characteristics of enzyme activity), while pH, EC, and SIC had no correlation with these indices and metrics. These results indicated that mixing feldspathic sandstone and sand is highly susceptible to changes in soil microbial activity, and the soil N limitation decreased while P became more limited. In summary, our research showed that adding feldspathic sandstone into sand can significantly improve soil quality and provide a theoretical basis for the development of desertified land resources.

Changes in Soil Microbial Activity and Community Composition as a Result of Selected Agricultural Practices

For a constantly growing human population, healthy and productive soil is critical for sustainable delivery of agricultural products. The soil microorganisms play a crucial role in soil structure and functioning. They are responsible for soil formation, ecosystem biogeochemistry, cycling of nutrients and degradation of plant residues and xenobiotics. Certain agricultural treatments, such as fertilizers and pesticides applications, crop rotation, or soil amendment addition, influence the composition, abundance and function of bacteria and fungi in the soil ecosystems. Some of these practices have rather negative effects; others can help soil microorganisms by creating a friendlier habitat or providing nutrients. The changes in microbial community structure cannot be fully captured with traditional methods that are limited only to culturable organisms, which represent less than 1% of the whole population. The use of new molecular techniques such as metagenomics offers the possibility to better understand how agriculture affects soil microbiota. Therefore, the main goal of this review is to discuss how common farming practices influence microbial activity in the soil, with a special focus on pesticides, fertilizers, heavy metals and crop rotation. Furthermore, potential practices to mitigate the negative effects of some treatments are suggested and treatments that can beneficially influence soil microbiota are pointed out. Finally, application of metagenomics technique in agriculture and perspectives of developing efficient molecular tools in order to assess soil condition in the context of microbial activities are underlined.

Restoring a degraded marsh using thin layer sediment placement: Short term effects on soil physical and biogeochemical properties

Recent interest has focused on wetland restoration techniques that introduce a thin layer of sediment onto degrading marsh surfaces. A restoration project in Avalon, New Jersey, received 5–19 cm of dredged sediment onto vegetated marsh areas and 32–82 cm of sediment into degraded open water panne features interspersed within the degraded marsh plain. There were significant differences in soil physical properties between the placed dredged sediments and the buried native marsh and panne soils. For example, six months after project implementation, application of dredged sediment increased surface panne bulk density from 0.22 ± 0.02 g cm−3 to 0.83 ± 0.09 g cm−3, surpassing the threshold required for Spartina alterniflora Loisel. establishment. Soil nutrient and microbial properties also differed between placed sediments and buried marsh/panne soils. Notably, buried marsh soils remained microbially active demonstrating the capacity for buried soils to provide labile nutrient sources, such as ammonium, during vegetation recruitment. Results suggest that thin layer sediment placement techniques may jump-start marsh recovery by maintaining native vegetation seed sources, rhizomes, and microbes in near-surface soils compared to other restoration approaches. Examining short term changes in soil microbial activity may provide early indicators of restoration outcome, although, additional research is required to more accurately predict changes in soil properties over time.

Seasonal dynamics of soil microbial activity after biochar addition in a dryland maize field in North-Western China

Soil microbes are of great importance in assessing key ecosystem functions due to their high sensitivity and capacity of providing ecologically relevant information. Benefits of biochar have been demonstrated, including enhancing carbon (C) sequestration and improving soil fertility. Considerable attention has been taken to effects of biochar on soil properties; however, information regarding effects of biochar on seasonal changes of soil microbial activities in field experiments in dryland soil was not well known. Based on a 2-year spring maize (Zea mays L.) field experiment, we examined changes in soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), urease and alkaline phosphatase activities with three biochar application rates (0, 10, and 30tha−1) at 0–10cm and 10–20cm soil layers in year 2013 and 2014 in silty loam soils on the Loess Plateau in North-Western China. Our results indicated that biochar increased MBC except at silking stage (R1) in 2013, whereas it tended to decrease MBC except at 6-leaf stage (V6) in 2014. MBN in the shallower (0–10cm) soil layer in 2013 and MBP in 2014 generally increased with biochar rates. Significant positive correlations between microbial biomass and soil water content (SWC) were observed. Results also showed that there were considerable fluctuations in enzymes activities across the growth periods and depths. Biochar significantly increased alkaline phosphatase activities in 2014, and resulted in small but detectable shifts in soil urease activities in both years. These results provided evidence that biochar addition could be an effective management practice for soil microbial activities throughout crop growing season in a dry agricultural system, although soil factors from different climates might lead to some shifts of effects of biochar.

Biochar amendment and phosphorus fertilization altered forest soil microbial community and native soil organic matter molecular composition

Fertilizer application to nutrient-deficient forest soils may alleviate soil nutrient limitations, but long-term application may be cost-prohibitive and logistically challenging to apply to large areas. Biochar has been proposed as a soil amendment to increase soil carbon storage and may emulate fertilizer application by increasing soil nutrient availability. However, biochar may also stimulate microbial activity, potentially accelerating native soil organic matter (OM) decomposition and altering soil OM molecular composition. Here we compare changes in soil microbial activity and native OM composition in a P-limited temperate hardwood forest in Ontario, Canada 3 years after the amendment of biochar and P fertilizer using a factorial design experiment. Phospholipid fatty acid analysis indicated that fungal activity was stimulated by biochar and biochar + P addition but not P amendment alone, while bacterial activity increased with all treatments. Concentrations of solvent-extractable acyclic and cyclic lipids, base-hydrolyzable cutin and suberin components, and lignin-derived phenols increased with biochar and biochar + P amendment and to a lesser extent with P fertilization. Biomarker ratios indicated soil OM compositional shifts toward greater proportions of cyclic versus acyclic aliphatic lipids and lignin-derived phenol monomers versus dimers with biochar and biochar + P amendment, but not with P fertilization. Solution-state nuclear magnetic resonance analysis of base-extractable soil OM showed increased proportions of aliphatic lipids and lignin and fewer carbohydrates with all treatments. The results suggest that biochar amendment may alleviate nutrient deficiencies in P-limited forest ecosystems. However, biochar altered the soil microbial community structure and shifted the native soil OM composition toward a greater proportion of recalcitrant OM, which may alter soil OM turnover and nutrient cycling rates with long-term biochar amendment.

Chronic Nitrogen Deposition Has a Minor Effect on the Quantity and Quality of Aboveground Litter in a Boreal Forest.

There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal soils. However, key underlying mechanisms explaining this increase have not been resolved. Two potentially important mechanisms are that aboveground litter production increases, or that litter quality changes in response to N enrichment. As such, our aim was to quantify whether simulated chronic N deposition caused changes in aboveground litter production or quality in a boreal forest. We conducted a long-term (17 years) stand-scale (0.1 ha) forest experiment, consisting of three N addition levels (0, 12.5, and 50 kg N ha-1 yr-1) in northern Sweden, where background N deposition rates are very low. We measured the annual quantity of litter produced for 8 different litter categories, as well as their concentrations of C, N, phosphorus (P), lignin, cellulose and hemi-cellulose. Our results indicate that mosses were the only major litter component showing significant quantitative and qualitative alterations in response to the N additions, indicative of their ability to intercept a substantial portion of the N added. These effects were, however, offset by the other litter fractions where we found no changes in the total litter fluxes, or individual chemical constituents when all litter categories were summed. This study indicates that the current annual litter fluxes cannot explain the increase in soil C that has occurred in our study system in response to simulated chronic N application. These results suggest that other mechanisms are likely to explain the increased soil C accumulation rate we have observed, such as changes in soil microbial activity, or potentially transient changes in aboveground litter inputs that were no longer present at the time of our study.

Comparative assessment of microbial enzyme activity with compost and sewage sludge amendment

Changes in soil microbial activities were investigated to examine the effect of aerobically digested sewage sludge (SS) and compared with compost under incubation conditions over 63 days. Sandy soil was amended with 0.25, 0.5, 1.0 and 1.5 % w/w of compost and sewage sludge. Enzyme activity (dehydrogenase, alkaline phosphatase, acid phosphatase, phytase and urease) were examined at an interval of 3, 7, 14, 21, 28, 42 and 63 days. At the end of the experiment the change in organic carbon, nitrogen, potassium and phosphorus was also recorded.Results indicated that enzyme activities were substantially enhanced in presence of both amendments for first few days and the higher increases were measured at 1.5% of compost and sewage sludge amendment. Then an overall decrease in enzyme activity was recorded. Both the amendments also significantly increased the organic carbon, nitrogen and potassium of the soil while increase in available phosphorus was only recorded in treatment receiving compost. The present experiment indicated that addition of compost and sewage sludge have positive effect on soil microbial activity and can be safely used as soil amendment without having any adverse effect. Though, a previous examination of sewage sludge to be used must be made for heavy metals and pathogens.

Changes in soil microbial activity and physicochemical properties in agricultural soils in Eastern Spain

Agricultural land management greatly affects soil properties. Microbial soil communities are the most sensitive and rapid indicators of perturbations in land use and soil enzyme activities are sensitive biological indicators of the effects of soil management practices. Citrus orchards frequently have degraded soils and this paper evaluates how land management in citrus orchards can improve soil quality. A field experiment was performed in an orchard of orange trees (&lt;em&gt;Citrus Sinensis&lt;/em&gt;) in the Alcoleja Experimental Station (Eastern Spain) with clay-loam agricultural soils to assess the long-term effects of herbicides with inorganic fertilizers (H), intensive ploughing and inorganic fertilizers (P) and organic farming (O) on the soil microbial properties, and to study the relationship between them. Nine soil samples were taken from each agricultural management plot. In all the samples physicochemical parameters, basal soil respiration, soil microbial biomass carbon, microbial indexes (BSR/C, Cmic/C and BSR/Cmic) and enzymatic activities (urease, dehydrogenase, ß-glucosidase and acid phosphatase) were determined. The results showed significant differences between the different agricultural management practices for the microbial properties and soil microbial indexes, since these were strongly associated with the soil organic matter content. Unlike herbicide use and intensive ploughing - management practices that both showed similar microbial soil properties - the organic management practices contributed to an increase in the soil biology quality, aggregate stability and organic matter content.

Restoration of tropical peat soils: The application of soil microbiology for monitoring the success of the restoration process

In South East Asia, increased population and agricultural demands, especially for oil palm cultivation, have led to peatland conversion, resulting in environmental degradation. To conserve peatland’s function as a biodiversity and carbon reservoir, restoration of an oil palm plantation after burning in tropical peat swamp area was carried out by revegetation using native peat swamp forest plants, together with land rewetting. To monitor the success of the restoration process, soil sampling was carried from that restoration area as well as surrounding natural forest and burned oil palm plantation as comparisons. Analyses of physico-chemical and biological revealed substantial differences after 3.5 years of restoration between the restored soil and both burned oil palm plantation and the natural forest soils. These differences were seen in both physical and chemical characteristics (including water holding capacity (WHC), bulk density (ρb), organic matter, and concentration of ammonium, nitrate and phosphate) as well as the activity and diversity of soil microbial community. Increased viable microbial biomass (118% compared with burned oil palm plantation soil) and substrate utilising capacity (31% increase compared with the natural forest soil) as determined by Community Level Physiological Profiling (CLPP) indicated that the restoration of the soil has resulted in significant changes in soil microbial activity. Analysis of all the parameters measured using Principal Component Analysis (PCA) allowed examination of the relationship between the physical-chemical and biological properties of each of the three soils and revealed that, as like other ecosystems, pH and soil phosphatase activity may be useful management parameters in terms of monitoring the restoration progress of tropical peatlands.