Soil microbial community of abandoned sand fields

Soil Biology and Biochemistry, 1994

The relationships between soil texture and the proportions of soil organic C and N present in the microbial biomass, the amounts of C and N mineralized per unit of microbial biomass and the C : N ratio of the microbial biomass in Dutch grassland soils were investigated. The proportions of both soil C and N in the microbial biomass were higher in fine-textured soils than in coarse-textured soils. The ratios between C mineralization and microbial biomass C (activity of the microbial biomass) and between N mineralization and microbial biomass C were both negatively correlated with the percentage of soil organic C in the microbial biomass. The activity of the biomass was twice as large in an average sandy or loam soil than in an average clay. While the activity of the microbial biomass was the same in an average sandy and loam soil, the amount of N mineralized per amount of microbial biomass was larger in the sandy soils. This was associated with a higher C:N ratio of the microbial biomass in the sandy soils (average 8) than in the loams (average 5). The amount of N mineralized per amount of microbial biomass was lowest in the clays. This was associated with the lower activity of the microbial biomass and its relatively low C:N ratio (average 6). The observed differences in N mineralization between soil types could be calculated well with a simple food web model using the observed C:N ratios of the microbial biomass.

Applied Soil Ecology, 2009

Soil Biology & Biochemistry, 1993

Disturbance of shrub-steppe soils and alterations in plant cover may affect the distribution, size and activity of soil microorganisms and their ability to biogeochemically cycle essential nutrients. Therefore, the soil microbial biomass and activity and selected soil enzyme activities were determined for two arid ecosystems, an undisturbed perennial shrub-steppe and annual grassland, which was initially shrub-steppe and has been an annual grassland since the disturbance caused by farming ceased in the 1940s. Soils were sampled at O-5 and 5-15cm depths beneath sagebrush (Artemisia fridenfata Nutt.), bluebunch wheatgrass [E/ytrigiu spicata (Pursh) D. R. Dewey] and cryptogamic soil lichen crust at the perennial site and beneath downy brome (Bromus tecforum L.) at the annual grassland site. Soils were analyzed for physical properties, inorganic N, microbial biomass C and N, respiration and several enzymes. The soil pH and bulk density usually increased, while inorganic N, total N and total C decreased as a function of soil depth. Soil microbial biomass C and N, soil respiration and soil dehydrogenase activity were 2-15 times higher in the top 5 cm of soil than at the 5-15 cm depth regardless of plant type. Loss of this surface soil would therefore be detrimental to microbially-mediated cycling of nutrients. Surface soil (&5cm depth) microbial biomass C and N and soil respiration, dehydrogenase and phosphatase activity were influenced by plant type and decreased in the order B. fectorum > A. widentutu = E. spicura > soil crust. Spatial distribution of plant species at the shrub-steppe site resulted in "islands" of enhanced microbial biomass and activity underneath the shrubs and grasses when compared to the interplant areas covered with soil crust. When plant cover was used to compute a landscape estimate of soil microbial biomass C and N for the perennial shrub-steppe and the annual grassland, similar values were obtained. This indicates that while the distribution of microorganisms may be more heterogeneous in the shrub-steppe, the average across the landscape is the same as the more homogeneous annual grassland.

Resonance, 2004

Applied Soil Ecology, 2008

a p p l i e d s o i l e c o l o g y 4 0 (2 0 0 8) 4 3 2-4 4 6

The biological activity of the soil is highest in the upper layer, predominantly the rooting layer, where energy is present. This upper layer is extremely biotic and is, therefore, called a living system. This living system is surprisingly diverse. The basis for this diversity is provided by this spatial and temporal heterogeneity. Mineralization of organic matter or recycling of elements is the collective responsibility of soil fauna and soil microflora. Soil fauna fragments organic structures and influences primary decomposers such as the soil microflora. They also play a role in the synthesis of organic matter and any kind of formation of soil material. Quantification of the role of single species or size groups is extremely difficult since many feeding interactions are still not well understood. In principle, this dynamic system of mineralization of organic matter is sustainable, because of the equilibrium and stability of the soil system. The three key functions related to soil quality are (i) dynamics and mineralization of organic matter, (ii) soil structure formation and maintenance, and (iii) support and control of plant production and species diversity. Although these functions can be carried out by alternative systems, and via alternative pathways, as routes in food webs, it is the author's opinion that some functions are irreplaceable. Therefore, there is concern that repeated stress will lead to impoverishment of the soil community. Disturbance by contaminants, such as heavy metals, can best be measured by fauna, looking at species diversity. In the majority of soils, microorganism diversity is probably never reduced to such a level that it affects the functioning of the decomposer system. It is likely, that only those processes carried out by a few microbial species, such as nitrification and nitrogen fixation, have the potential to show clear responses. Defining the cause of disturbance, such as changes in land use, including desiccation, acidification or fragmentation, determines the direction of monitoring. Using the Dutch Soil Quality Indicator System may be the safest way to monitor soil quality. Indicators of soil quality should be physical chemical biological and visible. This selection should be based on land use, the relationship between soil function and the indicator, spatial and temporal patterns of variation and the importance of this variation, the sensitivity of the measurement to changes in soil management, and comparability with routine sampling and monitoring programmes.

Biology and Fertility of Soils, 1996

A field study was undertaken to determine the effects of different plant species on soil microbial biomass and N transformations in a well drained silty clay loam (Typic Dystrochrept) and a poorly drained clay loam (Typic Humaquept). The crop treatments were faba bean (Vicia faba L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), bromegrass (Bromus inermis L.), reed canarygrass (Phalaris arundinacea L.), and wheat (Triticum aestivum L.). Measurements of microbial biomass C, denitrification capacity, and nitrification capacity were performed periodically in the top 2 -10 cm of soil. On most sampling dates, all three parameters were higher under perennial than under annual species. The nitrification capacity was positively affected by the level of N applied to each species (r = 0.65** for the silty clay loam and 0.84*** for the clay loam) and not directly by the plant. The differences found in microbial biomass C were significantly correlated with the water-soluble organic C present un der each plant species (r = 0.74*** for the silty clay loam and 0.90*** for the clay loam), suggesting differences in C deposition in the soil among plant species. ln the silty clay loam, the denitrification capacity was positively related to the amount of organic C found under each plant species, while in the clay loam, it was dependent on the amount of N applied to each species. There was less denitrification activity per unit biomass un der legume species th an under gramineae, suggesting that, depending on their composition, root-derived materials may be used differently by soil microbes.

Biology and Fertility of Soils

Soil changes induced by crop rotations and soil management need to be quantified to clarify their impact on yield and soil quality. The objective of this study was to investigate the effect of continuous oat (Avena sativa L.) and a lupin (Lupinus albus L.)-oat rotation with and without tillage on soil enzymes, crop biomass and other soil properties In year 1, oat and lupin were grown in undisturbed plots or in plots subjected to disc tillage. Crop residues were incorporated before oat was sown in year 2 in the disc-tilled plots or remained on the soil surface of untilled plots. Soil samples were collected regularly and analysed for pH, organic C, Kjeldahl-N, mineral N, extractable P, and the enzyme activities of b-glucosidase, cellulases, acid phosphatase, proteases, urease, and culturable bacteria and fungi. The main crop and tillage effects on soil parameters were: b-glucosidase activity was greater after lupin than after oat, and the opposite was true for the number of culturable fungi. Organic carbon, phosphatase, cellulase and protease were greater in tilled soil than in the absence of tillage. Associations between variables that were stable over the 2 yr were those for mineral N and urease activity, cellulase activity and pH, and that of phosphatase activity and organic C. Our results contrast with most of the previous information on the effect of tillage on soil enzymes, where the activities were reported to be unchanged or decreased following tillage. This difference may be related to the small organic C content of the soil and to the fact that it was under fallow prior to the start of the experiment. In consequence, incorporation of residues would provide new sources of labile organic C for soil microbes, and result in increased enzymatic activity. The results obtained suggest that in coarse-textured soils poor in organic matter, tillage with residue conservation after a period of fallow rapidly improves several soil characteristics and should be carried out even if it were to be followed by a no-till system in the following years. This should be taken into consideration by land managers and technical advisers.

Journal American Society of Mining and Reclamation, 2007

Nitrogen (N) is usually the nutrient most limiting production in semiarid ecosystems and at very low concentrations can seriously impact ecosystem processes. Soil from five mines, incorporating a number of commonly used land reclamation practices (grazing vs. un-grazed; stockpiled vs. direct hauled soil; shrub mosaic vs. grass seed mix; and stubble mulch vs. hay mulch), were sampled and analyzed for soil total N (TN) and microbial biomass N (MBN). All mines were located in semiarid Wyoming in either mixed-grass or sagebrush steppe ecosystems. The various management practices investigated appeared to have little influence on TN. Reclaimed soils averaged 30% less TN than undisturbed native soils, suggesting that N could potentially limit vegetation production. Only two reclaimed sites (grass and shrub) at Mine 1 contained a greater mass of TN than an undisturbed site, and while the reason is unclear, greater precipitation (20% higher relative to the other sites sampled) may be responsible. The microbial communities present in undisturbed soils appear to uptake N more efficiently than microbial communities present in reclaimed soil, relative to total soil N. As N fertilizer is only rarely used in Wyoming surface mines, N can only accumulate in a reclaimed soil via wet or dry deposition or by N-fixation by free-living microorganisms or through symbiotic relationships. However, as legumes are typically only a small component of the vegetation, presumably deposition and/or microbial fixation of N are responsible for the majority of N accumulation in these ecosystems. Despite the low TN in reclaimed soils, high plant production on these reclaimed soils suggests that TN is not limiting production.

Agrokémia és talajtan (Nyomtatott), 2022

Land use change may modify key soil attributes, influencing the capacity of soil to maintain ecological functions. Understanding the effects of land use types (LUTs) on soil properties is, therefore, crucial for the sustainable utilization of soil resources. This study aims to investigate the impact of LUT on primary soil properties. Composite soil samples from eight sampling points per LUT (forest, grassland, and arable land) were taken from the top 25 cm of the soil in October 2019. The following soil physicochemical parameters were investigated according to standard protocols: soil organic matter (SOM), pH, soil moisture, NH4 +-N, NO3-N, AL-K2O, AL-P2O5, CaCO3, E4/E6, cation exchange capacity (CEC), base saturation (BS), and exchangeable bases (Ca 2+ , Mg 2+ , K + , and Na +). Furthermore, soil microbial respiration (SMR) was determined based on basal respiration method. The results indicated that most of the investigated soil properties showed significant difference across LUTs, among which NO3-N, total N, and K2O were profoundly affected by LUT (p ≤ 0.001). On the other hand, CEC, soil moisture, and Na + did not greatly change among the LUTs (p ≥ 0.05). Arable soils showed the lowest SOM content and available nitrogen but the highest content of P2O5 and CaCO3. SMR was considerably higher in grassland compared to arable land and forest, respectively. The study found a positive correlation between soil moisture (r = 0.67; p < 0.01), Mg 2+ (r = 0.61; p < 0.01), and K2O (r = 0.58; p < 0.05) with SMR. Overall, the study highlighted that agricultural practices in the study area induced SOM and available nitrogen reduction. Grassland soils were more favorable for microbial activity.

Soil Biology & Biochemistry, 2005

The relationship between biodiversity and ecosystem functioning is of major scientific concern today. Few studies though have measured the interactions between soil microorganisms and plant diversity, the purpose of this study was to examine the link between plant diversity and microbial communities in fertilized versus unfertilized grasslands. Experiments were carried out on a permanent grassland in northeastern France where agricultural practices had remained unchanged for the last 13 years. The experimental design included two plots of 300 m 2 (fertilized at 120 kg N ha K1 or non-fertilized). Plots were replicated into three equal sub-plots (100 m 2 ). From each sub-plot, six samples of soil and vegetation were taken at three dates during floristic development. At sampling, ground cover of each species was estimated, and total amount of C and N was determined in aboveground and root biomass. Soil samples were analyzed in order to measure the metabolic fingerprints of microorganisms using Biolog w GN2 microplates. Floristic composition and carbon substrate utilization patterns of rhizobacterial communities were more diversified in unfertilized than fertilized plots. In unfertilized plots, the development of Convolvulus arvensis and two legumes (Trifolium pratense and Trifolium repens) may help maintain observed floristic diversity. Moreover, an inversion of C and N distribution between aboveground and root biomass during the vegetation cycle probably induced a variation of rhizodeposition. This phenomenon could explain the differences of rhizobacterial metabolic fingerprints observed between experimental plots. q

Chemosphere, 2003

Land use and agricultural practices modify both the amounts and properties of C and N in soil organic matter. In order to evaluate land use and management-dependent modifications of stable and labile C and N soil pools, (i) organic C and total N content, (ii) microbial (C mic) and N (N mic) content and (iii) C and N mineralisation rates, termed biologically active C and N, were estimated in arable, grassland and forest soils from northern and southern Germany. The C/N-ratios were calculated for the three levels (i)-(iii) and linked to the eco-physiological quotients of biotic-fixed C and N (C mic /C org , N mic /N t) and biomass-specific C and N mineralisation rate (qCO 2 , qN min). Correlations could mainly be determined between organic C, total N, C mic , N mic and C mineralisation for the broader data set of the land use systems. Generally, the mineralisation activity rate at 22°C was highly variable and ranged between 0.11 and 17.67 lg CO 2-C g À1 soil h À1 and)0.12 and 3.81 lg (dNH þ 4 + dNO À 3)-N g À1 soil h À1. Negative N data may be derived from both N immobilisation and N volatilisation during the experiments. The ratio between C and N mineralisation rate differed significantly between the soils ranging from 5 to 37, and was not correlated to the soil C/N ratio and C mic /N mic ratio. The C/N ratio in the Ôbiologically activeÕ pool was significantly smaller in soils under conventional farming than those under organic farming systems. In a beech forest, it increased from the L, Of to the Ah horizon. The biologically active C and N pools refer to the current microbial eco-physiology and are related to the need for being C and N use efficient as indicated by metabolic qCO 2 and qN min quotients.

European Journal of Soil Biology, 2006

Soil Biology and Biochemistry, 2004

We investigated the relationship between soil organic matter (SOM) content and N dynamics in three grassland soils (0-10 and 10-20 cm depth) of different age (6, 14 and 50 y-old) with sandy loam textures. To study the distribution of the total C and N content the SOM was fractionated into light, intermediate and heavy density fractions of particulate macro-organic matter (150-2000 mm) and the 50-150 mm and !50 mm size fractions. The potential gross N transformation rates (mineralisation, nitrification, NH 4 C and NO 3 K immobilization) were determined by means of short-term, fully mirrored 15 N isotope dilution experiments (7-d incubations). The long-term potential net N mineralisation and gross N immobilization rates were measured in 70-d incubations. The total C and N contents mainly tended to increase in the 0-10 cm layer with increasing age of the grassland soils. Significant differences in total SOM storage were detected for the long-term (50 y-old) conversion from arable land to permanent grassland. The largest relative increase in C and N contents had occurred in the heavy density fraction of the macro-organic matter, followed by the 50-150 and !50 mm fractions. Our results suggest that the heavy density fraction of the macroorganic matter could serve as a good indicator of early SOM accumulation, induced by converting arable land to permanent grassland. Gross N mineralisation, nitrification, and (long-term) gross N immobilization rates tended to increase with increasing age of the grasslands, and showed strong, positive correlations with the total C and N contents. The calculated gross N mineralisation rates (7-d incubations) and net N mineralisation rates (70-d incubations) corresponded with a gross N mineralisation of 643, 982 and 1876 kg N ha K1 y K1 , and a net N mineralisation of 195, 208 and 274 kg N ha K1 y K1 in the upper 20 cm of the 6, 14 and 50 y-old grassland soils, respectively. Linear regression analysis showed that 93% of the variability of the gross N mineralisation rates could be explained by variation in the total N contents, whereas total N contents together with the C-toN ratios of the !50 mm fraction explained 84% of the variability of the net N mineralisation rates. The relationship between long-term net N mineralisation rates and gross N mineralisation rates could be fitted by means of a logarithmic equation (net mZ0.24Ln(gross m)C0.23, R 2 Z0.69, P!0.05), which reflects that the ratio of gross N immobilization-to-gross N mineralisation tended to increase with increasing SOM contents. Microbial demand for N tended to increase with increasing SOM content in the grassland soils, indicating that potential N retention in soils through microbial N immobilization tends to be limited by C availability.

2009

Sagebrush-dominated ecosystems are being transformed by wildfire, rangeland improvement techniques, and exotic plant invasions. These disturbances have substantial effects on the composition and structure of native vegetation, but the effects on ecosystem C and N dynamics are poorly understood. To examine whether differences in dominant vegetation affect the quantity and quality of plant organic matter inputs to soil, ecosystem C and N pools and rates of plant turnover were compared among historically grazed Wyoming big sagebrush, introduced perennial crested wheatgrass, and invasive annual cheatgrass communities. Since low soil moisture during the summer may inhibit the microbial colonization of plant detrital inputs and result in C-limitations to microbial growth, soils were treated with an in situ pulse of plant detritus prior to the onset of the summer dry-season, and rates of soil C and gross N cycling were compared between treated and untreated soils. Finally, because plant detritus is the dominant form of labile C input to soil microbes over a large portion of the year, the decomposition of 13 C-labeled iv annual grass detritus was used to determine the importance of plant detritus versus soil organic matter as microbial substrate. Results revealed large differences in ecosystem C and N pools, and in the quantity of plant C and N inputs to soil among vegetation types, but differences in soil C and N cycling rates were more subtle. Plant biomass pools were greatest for sagebrush stands, but plant C and N inputs to soil were greatest in cheatgrass communities, such that rates of plant C and N turnover appeared to be accelerated in disturbed ecosystems. Earlier release of plant biomass to soil detrital pools stimulated N availability to a greater extent than C availability relative to untreated soils, and this effect could not be predicted from the C:N stoichiometry of plant detritus. Finally, in situ decomposition of cheatgrass detritus was rapid; however, there was no clear evidence of a time-lag during summer in microbial colonization of recently released plant detritus, and microbial consumption of plant detritus did not result in N-limitations to microbial growth.