Β-glucosaminidase Activities Research Articles

Apolipoprotein A-I Inhibits Increased Activity of Chitotriosidase and β-Glucosaminidase in the Liver of Mice with BCG-Induced Tuberculous Inflammation

Apolipoprotein A-I Inhibits Increased Activity of Chitotriosidase and β-Glucosaminidase in the Liver of Mice with BCG-Induced Tuberculous Inflammation

Apolipoprotein A-I inhibits the increased activities of chitotriosidase and β-glucosaminidase in the liver of mice with BCG-induced tuberculosis inflammation

The aim of the investigation was to study the activity of lysosomal chitinases ( chitotriosidase and β- glucosaminidase ) in the liver of mice using a model of BCG- induced tuberculous inflammation after intravenous administration of apolipoprotein A-I. Material and methods . The study was carried out on male CBA mice weighing 20–22 g. Disseminated tuberculous inflammation was modeled by a single intraperitoneal injection of 0.5 mg of BCG vaccine . The activity of chitinases was determined using fluorescent substrates 4-methylumbelliferyl β-D- N,N ′,N ′′- triacetylchitotrioside and 4-methylumbelliferyl N- acetyl -β-D- glucosaminide . Results and discussion . BCG- infection of animals after 4 weeks caused a significant increase in the activity of endogenous chitinases in comparison with the control group : chitotriosidase – 3.05 times (p <0.001), β- glucosaminidase – 1.76 times (p <0.01). Intravenous administration of apolipoprotein A-I to animals against the background of BCG infection inhibited the increased enzyme activity , values did not significantly differ from the control values . Conclusions . The results of these studies indicate the ability of apolipoprotein A-I to reduce the increased activity of endogenous lysosomal chitinases in the liver of mice with BCGinduced tuberculous inflammation .

Soil enzyme stoichiometry revealed the changes of soil microbial carbon and phosphorus limitation along an elevational gradient in a Pinus taiwanensis forest of Wuyi Mountains, Southeast China

Understanding changes in soil enzyme activities and ecoenzymatic stoichiometry is important for assessing soil nutrient availability and microbial nutrient limitation in mountain ecosystems. However, the variations of soil microbial nutrient limitation across elevational gradients and its driving factors in subtropical mountain forests are still unclear. In this study, we measured soil properties, microbial biomass, and enzyme activities related to carbon (C), nitrogen (N), and phosphorus (P) cycling in Pinus taiwanensis forests at different altitudes of Wuyi Mountains. By analyzing the enzyme stoichiometric ratio, vector length (VL), and vector angle (VA), the relative energy and nutrient limitation of soil microorganisms and its key regulatory factors were explored. The results showed that β-glucosaminidase (BG) activities increased along the elevational gradient, while the activities of β-N-acetyl glucosaminidase (NAG), leucine aminopeptidase (LAP), acid phosphatase (AcP) and (NAG+LAP)/microbial biomass carbon (MBC) and AcP/MBC showed the opposite trend. Enzyme C/N, enzyme C/P, enzyme N/P, and VL were enhanced with increasing elevation, while VA decreased, indicating a higher degree of microbial P limitation at low elevation and higher C limitation at high elevation. In addition, our results suggested that dissolved organic carbon and microbial biomass phosphorus are critical factors affecting the relative energy and nutrient limitation of soil microorganisms at different elevations. The results would provide a theoretical basis for the responses of soil carbon, nitrogen, and phosphorus availability as well as the relative limitation of microbial energy and nutrition to elevational gradients, and improve our understanding of soil biogeochemical cycle process in subtropical montane forest ecosystems.

Variations in soil aggregation, microbial community structure and soil organic matter cycling associated to long-term afforestation and woody encroachment in a Mediterranean alpine ecotone

Afforestation and subsequent expansion of trees on former grasslands may significantly impact the structure and activity of the soil microbial community, altering soil aggregation and affect its potential to store and cycle organic matter (OM). We investigated OM dynamics in aggregate-size topsoil samples collected along a Mediterranean alpine ecotone consisting of three vegetation types (grassland/shrubland, mixed shrubland-pine, and pine forest) in central Spain. Analytical determinations of soil organic carbon (SOC), total nitrogen (TN), particulate OM (POM), mineral-associated OM (MaOM), and the stable isotopic composition of carbon were conducted in each of the four aggregate-size fractions considered. Additionally, the structure of the microbial community (assessed as PLFA abundance), and the β-glucosidase and β-glucosaminidase activities were determined in bulk soil samples. More than half of the soil mass was contained within small macroaggregates regardless of vegetation type. SOC and TN values increased with decreasing aggregate-size classes across all vegetation types. The stability of microaggregates was negatively affected by the expansion of woody vegetation, which resulted in tree-dominated stands showing comparatively lower SOC and TN values in the smaller aggregate-size classes. On the other hand, these vegetation dynamics promoted soil macro-aggregation. While SOC contents did not show significant differences between land covers, vegetation shifts induced changes in the soil microbial community. Soil δ13C values, the abundance of gram-positive bacteria and β-glucosidase activity were significantly higher in grasslands/shrublands than in forests, while significantly higher fungi/bacteria ratio was observed in forests. Small macroaggregates appear to play a key role in the stabilisation of relatively unprocessed OM across all vegetation types, as suggested by their significantly higher concentrations of POM. However, this fraction represents the most labile pool of OM, and as such, it is the most exposed to mineralisation. We conclude that the afforestation and potential vegetation shifts experienced in Mediterranean alpine grasslands lead to distinct changes in soil microbial communities, aggregation and soil OM dynamics, which given the strong temperature sensitivity to decomposition commonly reported in cold environments, suggests that soil OM in these high-elevation ecosystems may become highly vulnerable to environmental change.

Effect of Quicklime on Microbial Community in Strong Acidic Soil

Quicklime has been used to improve acidic soils for several decades. The influence of quicklime on the microbial community in strong acidic soil of tobacco plants was investigated. Quicklime at concentrations of 0.75, 2.5, and 4.5 g·kg−1 was mixed with the soil for an incubation experiment. The soil physicochemical properties and enzyme activities of each samples were measured, and microbial diversity of the samples at different periods were determined using high-throughput sequencing. Quicklime had a significant impact on the pH, cation exchange capacity, NO3−–N, NH4+–N, K, and P of the soil. Additionally, quicklime contributed to the increased soil urease and soil β-glucosaminidase activities. According to high-throughput sequencing, the microbial diversity had not significantly increased by the 20th day due to quicklime. Similarly, on the 50th day, the diversity of bacteria significantly increased whereas that of fungi was not affected when the quicklime concentration was 0.75 g·kg−1. Rhodanobacter, Gaiellales, Streptomyces, Terrabacter, and Acidobacteriales were the key bacterial genera and Mortierella, Penicillium, Trichoderma, Aspergillus, Talaromyces, and Fusarium were the fungal genera which were affected on the 50th day. Redundancy analysis indicted that pH was an important environmental factor affecting fungal and bacterial communities. Quicklime concentration of 0.75 g·kg−1 positively affected the microbial community in strongly acidic soils of tobacco plants (pH <5).

Cover crop biomass and species composition affect soil microbial community structure and enzyme activities in semiarid cropping systems

Cover crops are promoted to increase soil organic carbon (SOC) storage and improve soil biological health in agricultural systems. However, cover crop effects on soil microbial communities – key regulators of SOC and nutrients – and functioning are not clear in semiarid environments. This study investigated the response of soil microbial community structure and enzyme activities to cover crop integration under limited-irrigation winter wheat (Triticum aestivum)-sorghum (Sorghum bicolor)-fallow rotation. The study had a randomized complete block design with eight treatments and three replications. Treatments were pea (Pisum sativum); oat (Avena sativa); canola (Brassica napus L.); and mixtures of pea + oat (POmix), pea + canola (PCmix), pea + oat + canola (POCmix), and pea + oat + canola + hairy vetch (Vicia villosa) + forage radish (Raphanus sativus L.) + barley (Hordeum vulgare L.) (diverse-mix) as cover crops; and a fallow. Soil samples were collected in the summer of 2017 and 2018 from 0 to 15 cm depth of each plot established in fall 2015. Microbial community size and structure were evaluated via ester-linked fatty acid methyl ester (EL-FAME) analysis, which showed that total microbial community size and fungal community were similar between soils under oats and diverse-mix, and were 31% and 41% greater than fallow, respectively. The FAME marker for arbuscular mycorrhizal fungi (AMF) was 84% greater under oats than fallow. The combined enzyme activity of acid phosphatase, β-glucosidase, and β-glucosaminidase was 294 mg p-nitrophenol (PNP) kg−1 soil h−1 under diverse-mix, which was greater than fallow (204 mg PNP kg−1 soil h−1, p = 0.021) in 2018. Cover cropping during fallow period in a crop-fallow rotation could increase total microbial community size, fungal abundance, and enzyme activities associated with carbon (C) and nutrient cycling. Among cover crops, oat and its mixture with legumes (pea and hairy vetch) and brassicas (canola and forage radish) were most effective in improving soil health and biogeochemical cycling in a hot and dry semiarid climate.

Soil microbial and nutrient responses over seven years of organic apple orchard maturation

Seven years of twelve treatment combinations of annual compost, wood chips, shredded paper mulch, or mow-and-blow ground cover and poultry litter, organic commercial, or no fertilizer control surface applications on soil decomposition and microbial activity were evaluated in an organic apple orchard. Because soil amendments were surface applied, microbial biomass, enzyme activities, organic matter, dissolved organic carbon (DOC) and dissolved total nitrogen (N), ammonium-N, and nitrate-N concentrations were measured in March from 2007 to 2013 at 0–0.1 and 0.1–0.3 m soil depths where biochemical activity and nutrient availability were expected to be greatest and where tree roots were expected to be located. Ground covers were applied by volume based on horticulture management and these applications rather than fertilizers were stronger drivers of soil nutrient and microbial property responses. Dehydrogenase and β-glucosaminidase activities were 1.5 times greater in 2008 and 2009, respectively, under mow-and-blow as compared to other ground covers. Enzymes may be sensitive indicators separating living and non-living mulch effects on soil during establishment of fruit tree orchards in the southeastern U.S. Organic matter (OM) and soil water content increased in all ground covers during the study. At greatest differences, soil OM and DOC were more than twice and dissolved total N and nitrate-N were more than three and five times greater in compost than other ground cover treatments. Relative differences between compost and other ground covers did not persist to the same extent during the seven years. Orchard floor management may need different strategies during different stages of orchard development.

Effect of Select Surfactants on Activities of Soil Enzymes Involved in Nutrient Cycling

ABSTRACTExperiments were conducted to investigate the impact of commonly used herbicides and surfactants on the activity of acid phosphatase, β-glucosidase, arylsulfatase, β-glucosaminidase, and dehydrogenase, using two soils (silt loam and silty clay loam) from Mid-Missouri, USA. The surfactants used in this study were alkylphenol ethoxylate + alcohol ethoxylate (ACTIVATOR 90), polyethoxylate (Agri-Dex®) and a blend of ammonium sulfate, drift reduction/deposition polymers, and an antifoam agent (THRUST®). The herbicides were glyphosate, atrazine, and bentazon. Surfactants and herbicides were applied to soils at the label rate, either alone or combined. In general, enzyme activity was enhanced more in silt loam soil than in silty clay loam soil. Acid phosphatase displayed the greatest amount of enzymatic activity within soils; dehydrogenase displayed the most inhibition, whilst β-glucosidase and β-glucosaminidase fluctuated based on treatment. ACTIVATOR 90 appeared to have the most inhibitory effect on enzymatic activity within soils compared to the control.

Microbial Compositions and Enzymes of a Forest Ecosystem in Alabama: Initial Response to Thinning and Burning Management Selections

Prescribed burning and tree thinning are commonly used restoration practices for US forests management to increase forest productivity and enhance plant and animal diversity. The impact of these practices in Alabama’s Bankhead National Forest (BNF) to soil microbial components and overall forest soil health are unknown. We hypothesized that microbial assemblages and enzyme activities are continuously changing in forest ecosystems especially due to management selections. Therefore, the objective of this study was to assess changes in microbial community compositions (fungal vs bacterial populations) via fatty acid methyl ester (FAME) profiling and several enzyme activities (β-glucosaminidase, acid phosphatase, arylsulfatase, β-glucosidase, xylanase, laccase, and manganese peroxidase) critical to soil organic matter (SOM) dynamics and biogeochemical cycling. In this forest, heavily-thinned plots without burning or less frequent burning treatments seemed to provide more favorable conditions (higher pH and lower C:N ratios) for C and N mineralization. This may explain a slight increase (by 12%) detected in fungi:bacteria (F:B) ratio in the heavily-thinned plots relative to the control. Thinned (lightly and heavily) plots showed greater ligninolytic (laccase and MnP) activities and lower β-glucosidase and β-glucosaminidase activities compared to the no-thinned plots probably due to increase depositions of woody recalcitrant C materials. We observed significant but negative correlations between the ligninolytic laccase and manganese peroxidase (Lac and MnP) enzymes respectively, with MBC (?0.45* and ?0.68** respectively) and MBN (?0.43* and ?0.65** respectively). Prescribed burning treatment reduced microbial biomass C and N of the 9-yr burned plot/lightly thinned plotsprobably due to depletion of labile C sources with the high temperatures, leaving mostly recalcitrant C sources as available soil substrates. Gram-positive bacteria (i15:0, a15:0, i17:0, and a17:0), actinomycetes (10-Me17:0, 10-Me18:0), AMF (16:1ω5c), and saprophytic fungi (18:1ω9c), largely contributed to the microbial compositions. This study bridges knowledge gaps in our understanding of microbial community compositions and enzyme-mediated processes in repeatedly burned and thinned forest ecosystems.

Mechanisms Involved in Soil Ammonium Production in a Mauritia flexuosa Palm Swamp Community

When soils are water saturated, the reduced forms of soil nitrogen such as ammonium are favored. Under anaerobiosis, ammonium production has been explained by several mechanisms such as organic nitrogen mineralization (ONM), dissimilatory nitrate reduction to ammonium (DNRA) and the release of adsorbed ammonium during microbial reduction of iron oxides (MRFeO). Nevertheless, in anaerobic soils the dominance of one mechanism over the others is still debated. Nitrogen appears to influence the reproductive dynamics of Mauritia flexuosa, the dominant canopy species of the “morichal” ecosystem. Even though M. flexuosa has been classified as “vulnerable”, ammonium production in morichal soils is not well understood. Considering this, we evaluated in a morichal soil from SE Venezuela, the mechanisms associated with ammonium production under anaerobic conditions. To this end, we designed an anaerobic incubation experiment to follow over time the concentrations of nitrate, extractable ferrous iron and ammonium together with the activity of β-glucosaminidase as an index of N mineralization. To account for the relative importance of ONM, DNRA and MRFeO on ammonium production, we used multiple linear regression models. The results showed that the three mechanisms are involved in ammonium production. However, ONM is the main source of ammonium in the initial 15 days of soil incubation, while MRFeO explains ammonium produced after 15 days of soil incubation. However, under climate change scenarios these mechanisms may be altered, thereby increasing the N limitation of morichales and consequently its vulnerability. Since morichales are threatened ecosystems, that play a key ecological, economic and cultural role, studies on the soil nitrogen dynamics are important to design and evaluate effective management, conservation and protection strategies. This study can be a relevant contribution in this area.

Effects of thinning intensity on nutrient concentration and enzyme activity in Larix kaempferi forest soils

As the decomposition of lignocellulosic compounds is a rate-limiting stage in the nutrient mineralization from organic matters, elucidation of the changes in soil enzyme activity can provide insight into the nutrient dynamics and ecosystem functioning. The current study aimed to assess the effect of thinning intensities on soil conditions. Un-thinned control, 20 % thinning, and 30 % thinning treatments were applied to a Larix kaempferi forest, and total carbon and nitrogen, total carbon to total nitrogen ratio, extractable nutrients (inorganic nitrogen, phosphorus, calcium, magnesium, potassium), and enzyme activities (acid phosphatase, β-glucosidase, β-xylosidase, β-glucosaminidase) were investigated. Total carbon and nitrogen concentrations were significantly increased in the 30 % thinning treatment, whereas both the 20 and 30 % thinning treatments did not change total carbon to total nitrogen ratio. Inorganic nitrogen and extractable calcium and magnesium concentrations were significantly increased in the 20 % thinning treatment; however, no significant changes were found for extractable phosphorus and potassium concentrations either in the 20 or the 30 % thinning treatment. However, the applied thinning intensities had no significant influences on acid phosphatase, β-glucosidase, β-xylosidase, and β-glucosaminidase activities. These results indicated that thinning can elevate soil organic matter quantity and nutrient availability, and different thinning intensities may affect extractable soil nutrients inconsistently. The results also demonstrated that such inconsistent patterns in extractable nutrient concentrations after thinning might not be fully explained by the shifts in the enzyme-mediated nutrient mineralization.

Arbuscular mycorrhizal fungal activity responses to winter cover crops in a sunflower and maize cropping system

The symbiosis between plants and arbuscular mycorrhizal fungi (AMF) benefits the health, nutrition and abiotic stress tolerance of the host plant. The maintenance of potential AMF inoculum in the winter is important because it will affect the colonization process in the subsequent crop. The objective of this study was to evaluate the effect of winter cover crops (CC) on AMF parameters (root colonization, length of hyphae and number of AMF spores), other variables indirectly related to AMF (the easily extractable glomalin-related soil protein (EE-GRSP) and the enzymatic activity of β-glucosaminidase), along with water-stable aggregates (WSA) as a soil quality indicator. In addition, the effect of two sampling dates on the variables in maize and the relationships among all of the variables were studied. The samples were obtained from a field experiment established in 2006 located in Aranjuez (Central Spain) under a Mediterranean semiarid climate. The treatments were winter cover crops of barley (Hordeum vulgare L.) or vetch (Vicia villosa L.) and fallow as a control. The study covered two seasons in 2011–12 and 2012–13 with sunflower (Helianthus annuus L.) and maize (Zea mays L.) as the main crop, respectively, with both sown in the spring. The main crops were irrigated according to the crop demand. Compared with the bare fallow conditions, cover crops improved most of the variables, maintaining the benefits of CC on AMF under the semiarid conditions of the Mediterranean climate. Barley as a cover crop gave the best results, whereas the performance of vetch was poorer. In sunflower, barley increased by 80% the hyphae length and β-glucosaminidase activity and by 30% other variables compared with the fallow; whereas in maize, 60–70% increments were found in AMF spores and the hyphae length and 2-fold in the enzyme activity. The sampling date affected all of the variables analyzed in the maize crop, except for the EE-GRSP and the WSA. Positive relationships were found between the variables directly related to AMF, EE-GRSP content and β-glucosaminidase activity. This suggests that the variables indirectly related to AMF, mainly the EE-GRSP, could be used as indicators of AMF. Finally, the enhancement of soil aggregate stability by the CC via AMF promotion was corroborated.

Soil quality differences in a row-crop watershed with agroforestry and grass buffers

Agroforestry buffers are believed to enhance soil quality parameters in agricultural landscapes. Soil enzyme activities, water stable aggregates (WSA), soil organic carbon (SOC), and total nitrogen (N) have been identified as good indices of soil quality. The objective of this study was to quantify soil quality differences among agroforestry buffer (AGF), grass waterway (GWW), grass buffer (GB), and row crop (RC) areas and distance from the tree base on corn (Zea mays L.)-soybean (Glycine max L.) watershed. Soil samples from AGF at 0, 30, 60, 90 cm distances from the tree base, and from AGF, GWW, GB, and RC areas were collected from summit, shoulder, and foot-slope landscape positions at the paired watershed study near Novelty, MO. Soil enzyme activity, WSA, soil C, and N were determined and data were analyzed statistically. The highest SOC and N percentages were found in AGF and the lowest in RC. β-Glucosidase activity was not significantly different among AGF, GWW, and RC. β-Glucosaminidase and dehydrogenase activities were significantly lower in RC treatment than all other treatments. Fluorescein diacetate (FDA) hydrolase activity was not significant among all treatments. WSA percentage was significantly higher in GWW and AGF as compared to others. Landscape position was not significantly different for all measured soil quality parameters. β-Glucosidase, β-glucosaminidase activities, WSA, and soil N did not differ significantly with distance from the tree base. SOC and FDA hydrolase activity were significantly lower at the tree base. Results imply that permanent vegetation has improved the soil quality by enhancing soil microbial activity and organic matter accumulation, thereby contribute positively to watershed restoration.

Quality Assessment of a Battery of Organic Wastes and Composts Using Maturity, Stability and Enzymatic Parameters

Chemical and biological parameters (NH4 +–N/NO3 −–N ratio, humification indices, and the activities of hydrolytic exoenzymes), commonly used to assess compost maturity and/or stability, were considered for the quality evaluation of a battery of organic materials, intended to be land applied. Acid and alkaline phosphatases, β-glucosidase, proteases and β-glucosaminidase activities proved to be reliable tests to distinguish the organic materials that were in an active stage of microbial activity, highly correlated to the chemical parameters NH4 +–N content and NH4 +–N/NO3 −–N ratio. In fact, these chemical parameters evidenced as important in the quality assessment of an organic material, strongly correlated with the biological parameters. The same was not true for the majority of the humification indices, which proved inadequate to compare the quality of such diverse organic materials. This was demonstrated by a multivariate statistical treatment of data, performed with these results in combination with results from the Dewar self-heating test, respiration activity and germination index, obtained in previous studies. Concluding, in a similar scenario, where the organic materials in evaluation are varied, both in the raw material an in the stability of the organic matter, the quality should be assessed by the integrated use of both chemical and biological parameters.

Main factors controlling microbial community structure and function after reclamation of a tailing pond with aided phytostabilization

Reclamation on bare tailing ponds has the potential to represent soil genesis in Technosols favoring the understanding of the changes of microbial communities and function. In this study we used phytostabilization aided with calcium carbonate and pig slurry/manure to reclaim an acidic bare tailing pond with the aim of investigating the effect of amending and different species on microbial community structure and function. We sampled after two years of amending and planting: unamended tailing soil (UTS), non-rhizospheric amended tailing soil (ATS), rhizospheric soil from four species, and non-rhizospheric native forest soil (NS), which acted as reference. The application of amendments increased pH up to neutrality, organic carbon (Corg), C/N and aggregate stability, while decreased salinity and heavy metals availability. No effect of rhizosphere was observed on physicochemical properties, metals immobilization and microbial community structure and function. To account for confounding effects due to soil organic matter, microbial properties were expressed per Corg. The high increments in pH and Corg have been the main factors driving changes in microbial community structure and function. Bacterial biomass was higher in UTS, without significant differences among the rest of soils. Fungal biomass followed the trend UTS<ATS=rhizospheric soils<NS. Bacterial growth increased and fungal growth decreased with increasing pH, despite the high availability of metals at low pH. Enzyme activities were lower in UTS, with β-glucosidase and β-glucosaminidase activities highly correlated with bacterial growth. Microbial activities were not correlated with the exchangeable fraction of heavy metals, indicating that microbial function is not strongly affected by these metals, likely due to the efficiency of the reclamation procedure to reduce metals toxicity. Changes in microbial community composition were largely explained by changes in pH, heavy metals availability and Corg, with increments in fungal and actinobacterial proportions with soil amending.

Soil Quality of a Mature Alley Cropping Agroforestry System in Temperate North America

Long-term effects of alley cropping on soils in the temperate zone are not widely known. Management, landscape, and soil depth effects on soil physical and biological properties were examined in a silver maple (Acer saccharinum L.) no-till corn (Zea mays L.)- soybean (Glycine max L.) rotation established in 1990 in northeast Missouri. Soils from crop alleys and tree rows were collected along transects traversing upper to lower landscape positions at three depths. Fluorescein diacetate hydrolase (FDA), β-glucosidase, β-glucosaminidase, and dehydrogenase activities were measured. Soil bulk density, aggregate stability, carbon (C), nitrogen N), and enzyme activities decreased with soil depth in alley and tree rows except for glucosaminidase. Soil physical and biological parameters did not differ significantly between alley and tree row. Landscape position effects were not significant for management or depth. Tree establishment improves soil quality in the crop alley as the system matures with improvements extended throughout the soil profile.

Short-term effects of plant litter on the dynamics, amount, and stoichiometry of soil enzyme activity in agroecosystems

Addition of plant litter can affect soil enzyme activity at three scales: dynamics, amount, and stoichiometry. In this study, we examined the dependence of soil enzyme activity at all three scales on litter quality. Soils of similar texture were collected from conventional and organic farming systems, the Center for Environmental Farming Systems, Goldsboro, North Carolina, USA. Soil samples were then amended with senescent pine needles, grass materials, and soybean residues of C:N ratio 139, 50, and 9, respectively, at 2 mg C g−1 soil, and the activities of soil β-glucosidase, exoglucanase, β-glucosaminidase, and phenol oxidase were measured over the course of 90-d incubation. Relationships between the dynamics of enzyme activity and litter quality appeared to be enzyme specific. Time patterns of soil β-glucosidase and β-glucosaminidase activity were independent of litter quality, with rapid increase in enzyme activity and reaching a peak several weeks after litter addition. In contrast, time patterns of polymer-degrading enzymes (exoglucanase and phenol oxidase) were dependent on litter quality. Exoglucanase activity showed a concave function with time following the addition of soybean residues or grass materials, but increased slightly following the addition of pine needles. Cumulative activities of soil enzymes were upregulated following litter addition and could be qualitatively assessed by litter C:N ratio. The activity of β-glucosaminidase was negatively related to litter C:N ratio, being greatest in soybean residues-amended soil. Litter of a low C:N ratio was generally better than litter of a high C:N ratio for increasing soil cellulase activity and vice versa for phenol oxidase. However, the stoichiometry of soil enzyme activity was decoupled with litter C:N ratio. Soybean residues and pine needles at opposite ends of the litter C:N range were more similar in the ratio of C- to N-acquiring enzyme activity. We also examined pH effects on the expression of added enzymes. Soil enzyme activities were enhanced as soil pH increased from 6 to 8. pH-associated changes in enzyme activity were generally smaller as compared to changes caused by other factors during the 42-d incubation. Our results suggest that litter effects on the dynamics, amount, and stoichiometry of soil enzyme activity were independent of soil pH. Litter C:N was a good indicator for the total amount, but not for the dynamics or stoichiometry of soil enzyme activity.

Combining phytoextraction and biochar addition improves soil biochemical properties in a soil contaminated with Cd

The main goal of phytoremediation is to improve ecosystem functioning. Soil biochemical properties are considered as effective indicators of soil quality and are sensitive to various environmental stresses, including heavy metal contamination. The biochemical response in a soil contaminated with cadmium was tested after several treatments aimed to reduce heavy metal availability including liming, biochar addition and phytoextraction using Amaranthus tricolor L. Two biochars were added to the soil: eucalyptus pyrolysed at 600°C (EB) and poultry litter at 400°C (PLB). Two liming treatments were chosen with the aim of bringing soil pH to the same values as in the treatments EB and PLB. The properties studied included soil microbial biomass C, soil respiration and the activities of invertase, β-glucosidase, β-glucosaminidase, urease and phosphomonoesterase. Both phytoremediation and biochar addition improved soil biochemical properties, although results were enzyme specific. For biochar addition these changes were partly, but not exclusively, mediated by alterations in soil pH. A careful choice of biochar must be undertaken to optimize the remediation process from the point of view of metal phytoextraction and soil biological activity.

Short-term effect of tillage and crop rotation on microbial community structure and enzyme activities of a clay loam soil

A field study was carried out to analyze the short-term (2 years) effect of tillage and crop rotation on microbial community structure and enzyme activities of a clay loam soil. The experimental design was a split-plot arrangement of treatments, consisting of two tillage treatments—ridge tillage (RT) and no-tillage (NT)—in combination with two crop rotation treatments—corn (Zea mays L.) monoculture and a 2-year corn-soybean (Glycine max L.) rotation. Phospholipid fatty acid (PLFA) profiles were used to assess soil microbial community structure. No-tillage resulted in significantly higher total PLFAs compared to the RT treatment, which was accompanied by higher activities of protease, β-glucosaminidase, and β-glucosidase. This suggests a close link between soil microbial communities and enzyme activities in response to tillage. The increase of total microbial lipid biomass in the NT soils was due to the increase in both fungal and bacterial PLFAs. Crop rotation had little effect on soil bacterial communities and enzyme activities, but it significantly influenced soil fungal communities, particularly arbuscular mycorrhizal fungi. Soils under monoculture corn had higher fungal biomass than soils under corn-soybean rotation regardless of tillage treatment.

Soil enzyme activities during the 2011 Texas record drought/heat wave and implications to biogeochemical cycling and organic matter dynamics

Extreme droughts and heat waves due to climate change may have permanent consequences on soil quality and functioning in agroecosystems. During November 2010 to August 2011, the Southern High Plains (SHP) region of Texas, U.S., a large cotton producing area, received only 39.6mm of precipitation (vs. the historical avg. of 373mm) and experienced the hottest summer since record keeping began in 1911. Several enzyme activities (EAs) important in biogeochemical cycling were evaluated in two soils (a loam and a sandy loam at 0–10cm) with a management history of monoculture (continuous cotton) or rotation (cotton and sorghum or millet). Samplings occurred under the most extreme drought and heat conditions (July 2011), after precipitation resulted in a reduction in a drought severity index (March 2012), and 12 months after the initial sampling (July 2012; loam only). Eight out of ten EAs, were significantly higher in July 2011 compared to March 2012 for some combinations of soil type and management history. Among these eight EAs, enzymes key to C (β-glucosidase, β-glucosaminidase) and P cycling (phosphodiesterase, acid and alkaline phosphatases) were significantly higher (19–79%) in July 2011 than in March 2012 for both management histories regardless of the soil type (P>0.05). When comparing all sampling times, the activities of alkaline phosphatase, aspartase and urease (rotation only) showed this trend: July 2011>March 2012>July 2012. Activities of phosphodiesterase, acid phosphatase, α-galactosidase, β-glucosidase and β-glucosaminidase were higher in July 2011 than July 2012 in at least one of the two management histories. Total C was reduced significantly from July 2011 to March 2012 in the rotation for both soils. Only the activities of arylsulfatase (avg. 36%) and asparaginase showed an increase from July 2011 to March 2012 for both soil types, which may indicate they have a different origin/location than the other enzymes. EAs continued to be a fingerprint of the soil management history (i.e., higher EAs in the rotation than in monoculture) during the drought/heat wave. This study provided some of the first evidence of the adverse effects of a natural, extreme drought and heat wave on soil quality in agroecosystems as indicated by EAs involved in biogeochemical cycling.