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1.
Jaroslav Šnajdr Vendula Valášková Veˇra Merhautová Jana Herinková Tomáš Cajthaml Petr Baldrian 《Soil biology & biochemistry》2008,40(9):2068-2075
Extracellular lignocellulose-degrading enzymes are responsible for the transformation of organic matter in hardwood forest soils. The spatial variability on a 12 × 12 m plot and vertical distribution (0–8 cm) of the ligninolytic enzymes laccase and Mn-peroxidase, the polysaccharide-specific hydrolytic enzymes endoglucanase, endoxylanase, cellobiohydrolase, 1,4-β-glucosidase, 1,4-β-xylosidase and 1,4-β-N-acetylglucosaminidase and the phosphorus-mineralizing acid phosphatase were studied in a Quercus petraea forest soil profile. Activities of all tested enzymes exhibited high spatial variability in the L and H horizons. Acid phosphatase and 1,4-β-N-acetylglucosaminidase exhibited low variability in both horizons, while the variability of Mn-peroxidase activity in the L horizon, and endoxylanase and cellobiohydrolase activities in the H horizon were very high. The L horizon contained 4× more microbial biomass (based on PLFA) and 7× fungal biomass (based on ergosterol content) than the H horizon. The L horizon also contained relatively more fungi-specific and less actinomycete-specific PLFA. There were no significant correlations between enzyme activities and total microbial biomass. In the L horizon cellulose and hemicellulose-degrading enzymes correlated with each other and also with 1,4-β-N-acetylglucosaminidase and acid phosphatase activities. Laccase, Mn-peroxidase and acid phosphatase activities correlated in the H horizon. The soil profile showed a gradient of pH, organic carbon and humic compound content, microbial biomass and enzyme activities, all decreasing with soil depth. Ligninolytic enzymes showed preferential localization in the upper part of the H horizon. Differences in enzyme activities were accompanied by differences in the microbial community composition where the relative amount of fungal biomass decreased and actinomycete biomass increased with soil depth. The results also showed that the vertical gradients occur at a small scale: the upper and lower parts of the H horizon only 1 cm apart were significantly different with respect to seven out of nine activities, microbial biomass content and community composition. 相似文献
2.
S. Papa E. Cembrola A. Pellegrino A. Fuggi A. Fioretto 《European Journal of Soil Science》2014,65(2):274-285
Forest soils contain a large amount of organic matter (OM) and therefore represent a considerable carbon reserve. The amount of OM sequestered in the soil is dependent on annual input of litter and its quality. The aim of this study was to investigate the quantity and quality of OM, the microbial capacity to degrade it and its recalcitrance to further degradation, by considering some extracellular enzyme activities in a beech (Fagus sylvatica L.) forest in south Italy (Mediterranean area). Our attention was focused on the decomposition continuum of the litter horizon and upper soil layer. Because fungi are the major decomposers of plant material, fungal biomass was also measured and its relationship with enzyme activities was tested. The results showed that: (i) the litter horizon and the upper soil layer differed in chemical characteristics and biological activities; (ii) within the litter horizon, the three layers detected for their different degree of degradation (L, recently fallen, not decomposed and not compressed material; F, partially decomposed and fragmented but macroscopically recognizable material; H, compressed and strongly fragmented) differed more in chemical characteristics than in biological activities; (iii) the enzyme activities and fungal biomass changed during the study period but a clear relationship with succession of seasons was evident only for cellulase, laccase, peroxidase and fungal biomass; and (iv) the upper soil layer included 42% OM and less than 50% of that was susceptible to further decomposition. This percentage was 30% in the OM of L. 相似文献
3.
Petra Kahle Christel Baum Barbara Boelcke Josefine Kohl Roland Ulrich 《植物养料与土壤学杂志》2010,173(5):737-746
Short‐rotation forestry (SRF) on arable soils has high potentials for biomass production and leads to long‐term no‐tillage management. In the present study, the vertical distributions of soil chemical and microbial properties after 15 y of SRF with willows and poplar (Salix and Populus spp.) in 3‐ and 6‐year rotations on an arable soil were measured and compared to a pertinent tilled arable site. Two transects at different positions in the relief (upper and lower slope; transect 1 and 2) were investigated. Short‐rotation forestry caused significant changes in the vertical distribution of all investigated soil properties (organic and microbial C, total and microbial N, soil enzyme activities), however, the dimension and location (horizons) of significant effects varied. The rotation periods affected the vertical distribution of the soil properties within the SRF significantly. In transect 1, SRF had higher organic‐C concentrations in the subsoil (Bv horizon), whereas in transect 2, the organic‐C concentrations were increased predominantly in the topsoil (Ah horizon). Sufficient plant supply of P and K in combination with decreased concentrations of these elements in the subsoil under SRF pointed to an effective nutrient mobilization and transfer from the deeper soil horizons even in the long term. In transect 1, the microbial‐C concentrations were higher in the B and C horizons and in transect 2 in the A horizons under SRF than under arable use. The activities of β‐glucosidases and acid phosphatases in the soil were predominantly lower under SRF than under arable use in the topsoil and subsoil. We conclude, that long‐term SRF on arable sites can contribute to increased C sequestration and changes in the vertical distribution of soil microbial biomass and soil enzyme activities in the topsoil and also in the subsoil. 相似文献
4.
Soil organic matter, microbial biomass and enzyme activities in a tropical agroforestry system 总被引:14,自引:0,他引:14
The effects of growing trees in combination with field crops on soil organic matter, microbial biomass C, basal respiration
and dehydrogenase and alkaline phosphatase activities were studied in soils under a 12-year-old Dalbergia sissoo (a N2-fixing tree) plantation intercropped with a wheat (Triticum aestivum) – cowpea (Vigna sinensis) cropping sequence. The inputs of organic matter through D. sissoo leaf litter increased and crop roots decreased with the increase in tree density. Higher organic C and total N, microbial
biomass C, basal soil respiration and activities of dehydrogenase and alkaline phosphatase were observed in treatments with
tree-crop combination than in the treatment without trees. Soil organic matter, microbial biomass C and soil enzyme activities
increased with the decrease in the spacing of the D. sissoo plantation. The results indicate that adoption of the agroforestry practices led to an improved organic matter status of
the soil, which is also reflected in the increased nutrient pool and microbial activities necessary for long-term productivity
of the soil. However, tree spacing should be properly maintained to minimize the effects of shading on the intercrops.
Received: 21 February 1997 相似文献
5.
M. A. Sánchez-Monedero C. Mondini M. L. Cayuela A. Roig M. Contin M. De Nobili 《Biology and Fertility of Soils》2008,44(6):885-890
The hydrolysis of the fluorescein diacetate (FDA), related to several soil hydrolases, has been utilised to estimate the potential
microbial activity of soil freshly amended with a wide range of organic amendments and compared to the size and activity of
soil microflora, measured by the microbial biomass C (B
C) and CO2 evolution, respectively. Three different composting mixtures at different phases of the composting process were added to
a semi-arid soil and incubated for 2 months under laboratory conditions. The addition of the organic amendment immediately
increased B
C and both measures of microbial activity (FDA and CO2 evolution). Highly significant correlations were found between FDA hydrolysis and B
C for soil amended with the three composting mixtures (r = 0.81–0.96; P < 0.01), regardless of the origin, composition and degree of stability of the organic amendments. FDA hydrolysis, conversely
to CO2 evolution, was unaffected by the disturbance caused by the soil amendment, indicating that the two parameters probably reflect
different aspects of soil microbial activity. FDA hydrolysis could serve as an alternative estimation of the microbial biomass
in freshly amended soils, despite the disturbance caused by the exogenous organic matter. 相似文献
6.
《Applied soil ecology》2009,41(3):401-410
Changes in enzyme activities during litter decomposition provide diagnostic information on the dynamics of decay and functional microbial succession. Here we report a comparative study of enzyme activities involved in the breakdown of major plant components and of other key parameters (microbial respiration, fungal biomass, N, lignin and cellulose contents) in homogeneous leaf litter of Quercus ilex L. incubated in three evergreen oak woods in Southern Italy (Campania), differing for chemical and physical soil characteristics and microclimatic conditions. The results showed that the litter mass loss rates were similar in the three wood sites. Independently of the incubation sites, cellulase, xylanase and peroxydase activities showed seasonal variations with maximum and minimum levels in wet and dry periods, respectively, and this pattern closely matched microbial respiration. Activities of α- and β-amylase, instead, were high at the beginning of incubation and quickly decreased with decomposition progress because their substrate was rapidly depleted. Laccase activity, in contrast, was low at the beginning of incubation but after 6 months it increased significantly. The increase of laccase activity was correlated to an increase in fungal biomass, probably reflecting a major shift in the litter microbial community. As concerns quality changes, N and lignin content did not significantly change during decay. The cellulosic component started being degraded after about 6 months in the litter incubated in two of the three wood sites and from the start of decomposition in the third site. Apart from minor differences in the levels of certain enzyme activities, the data showed that the functional microbial succession involved in the decomposition of Q. ilex leaf litter did not change appreciably in response to differences in soil and microclimatic conditions in the incubation sites. 相似文献
7.
T. A. Breland 《Biology and Fertility of Soils》1997,25(3):233-239
A mechanistic dynamic model (Verberne et al. 1990) was used to simulate mineralization of white-clover materials in a loam
(25% clay) and a sandy loam soil (5% clay). I tested the model‘s ability to simulate the observed temporal patterns and to
take account of altered physical protection as affected by soil compaction or spatial residue distribution. With default parameter
values, the model greatly overestimated net N mineralization. The model was very sensitive to changes in the C/N ratio of
the microbial biomass. Reducing this value from 8.0 to 6.0 improved the model performance. Nevertheless, initial N mineralization
was appreciably overestimated. Two hypotheses may explain the discrepancies: (1) the C/N ratio of the microbial biomass is
initially low (3–4) and gradually increases because of a succession from bacterial- to fungal-dominated biomass (H
1); (2) the C/N ratio of the substrates first attacked by microorganisms, i.e. water-soluble components such as sugars and
free amino acids, is higher than the average value (6.0) assumed for the readily decomposable fraction (H
2). Conceptually, this fraction originally included N-containing polymers (proteins and nucleic acids), which in large part
are water insoluble and probably attacked somewhat later than the monomers. Modification of the model, either by implementing
a dynamic C/N ratio of the biomass and the effect of faunal grazing or by increasing the C/N ratio of the easily decomposable
fraction, improved the model performance substantially. The two hypotheses need to be tested experimentally. The model adequately
simulated measured effects of spatial residue distribution and soil compaction on N mineralization after adjustment or parameter
values regulating physical protection of microbial biomass and metabolites. Moreover, there was a good agreement between simulated
and measured microbial biomass N in the two soils.
Received: 9 December 1996 相似文献
8.
Giancarlo Renella Ute Szukics Loretta Landi Paolo Nannipieri 《Biology and Fertility of Soils》2007,44(2):321-329
The aim of this work was to calculate indices of hydrolase production (Pr) and persistence (Pe) through simple arithmetical
calculations. Changes in acid and alkaline phosphomonoesterase, phosphodiesterase, urease, protease, and β-glucosidase activities
were monitored under controlled conditions in seven soils with a wide range of properties, in which microbial growth was stimulated
by adding glucose and nitrogen. Glucose mineralization was monitored by CO2–C evolution, and microbial growth was quantified by determining the soil adenosine triphosphate (ATP) content. Hydrolase
Pr and Pe indices were numerically quantified by the following relationships: Pr = H / t
H
and Pe = (r / H)Δt, respectively, where H indicates the peak value of each measured hydrolase activity, t
H
is the time of the peak value, r indicates the residual activity value, and Δt is the time interval t
r − t
H, where t
r is the time of the residual activity value. Addition of glucose and N-stimulated soil respiration increased ATP content and
stimulated the production of the measured hydrolase activities in all soils; the measured variable reached a maximum value
and then decreased, returning to the value of the control soil. Apart from β-glucosidase activity, whose activity was not
stimulated by glucose and N addition, the other measured hydrolase activities showed a trend that allowed us to calculate
the Pr and Pe indices using the above-mentioned equations. Acid phosphomonoesterase and protease Pr values were significantly
higher in soils under forest or set aside management; the alkaline phosphomonoesterase and phosphodiesterase Pr values were
generally higher in the neutral and alkaline soils, and the urease Pr values showed no obvious relationships with soil pH
or management. Concerning the persistence of enzyme activities, Pe values of the acid phosphomonoesterase activity were significantly
higher in the acidic soils, and those of urease activity were higher in acidic soils and the Bordeaux neutral soil. No relationships
were observed between Pe values of alkaline phosphomonoesterase, phosphodiesterase, or protease activities and soil pH or
management. The different responses of hydrolases were discussed in relation to soil properties, microbial growth, and regulation
at the enzyme molecular level. 相似文献
9.
Spatial changes of soil fungal and bacterial biomass from a sub-alpine coniferous forest to grassland in a humid, sub-tropical region 总被引:7,自引:0,他引:7
Fungal and bacterial biomass were determined across a gradient from a forest to grassland in a sub-alpine region in central
Taiwan. The respiration-inhibition and ergosterol methods for the evaluation of the microbial biomass were compared. Soil
fungal and bacterial biomass both significantly decreased (P<0.05) with the shift of vegetation from forest to grassland. Fungal and bacterial respiration rates (evolved CO2) were, respectively, 89.1 μl CO2 g–1 soil h–1 and 55.1 μl CO2 g–1 soil h–1 in the forest and 36.7 μl CO2 g–1 soil h–1 and 35.7 μl CO2 g–1 soil h–1 in the grassland surface soils (0–10 cm). The fungal ergosterol content in the surface soil decreased from the forest zone
(108 μg g–1) to the grassland zone (15.9 μg g–1). A good correlation (R
2=0.90) was exhibited between the soil fungal ergosterol content and soil fungal CO2 production (respiration) for all sampling sites. For the forest and grassland soil profiles, microbial biomass (respiration
and ergosterol) declined dramatically with depth, ten- to 100-fold from the surface organic horizon to the deepest mineral
horizon. With respect to fungal to bacterial ratios for the surface soil (0–10 cm), the forest zone had a significantly (P<0.05) higher ratio (1.65) than the grassland zone (1.05). However, there was no fungal to bacterial ratio trend from the surface
horizon to the deeper mineral horizons of the soil profiles.
Received: 30 March 2000 相似文献
10.
Microbial biomass C and N, and activities related to C and N cycles, were compared in needle and leaf litter, and in the uppermost 10 cm of soil under the litter layer in Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and silver birch (Betula pendula L.) stands, planted on originally similar field afforestation sites 23–24 years ago. The ground vegetation was differentiated under different tree species, consisting of grasses and herbs under birch and pine, and mosses or no vegetation with a thick layer of needles under spruce. The C:N ratio of the soils was 13–21 and the soil pHCaCl
2 3.8–5.2. Both showed little variation under different tree species. Microbial biomass C and N, C mineralization, net ammonification, reduction) did not differ significantly in soil under different tree species either. Birch leaf litter had a higher pHCaCl
2 (5.9) than spruce and pine needle litter (pH 5.0 and 4.8, respectively). The C:N ratio of spruce needles was 30, and was considerably higher in pine needles (69) and birch leaves (54). Birch leaves tended to have the highest microbial biomass C and C mineralization. Spruce needles appeared to have the highest microbial biomass N and net formation of mineral N, whereas formation of mineral N in pine needles and birch leaves was negligible. Microbial biomass C and N were of the same order of magnitude in the soil and litter samples but C mineralization was tenfold higher in the litter samples. 相似文献
11.
M. Pawlett D. W. Hopkins B. F. Moffett J. A. Harris 《Biology and Fertility of Soils》2009,45(4):361-369
The effect of liming and earthworms on the composition and function of soil microbial communities was investigated in an upland
soil from the UK in order to understand interactions between the biotic and abiotic components of soil systems. A factorial
experiment was established using soils from the Sourhope Farm, near Kelso, with lime or no lime added, with or without earthworms
added and a combined treatment of both lime and earthworm additions. The soils were incubated and destructively sampled after
180 days. Measurements of soil microbial biomass, dehydrogenase activity, phenotypic structure (by phospholipid fatty acid
analysis (PLFA) and responses to four carbon substrates (d-glucose, l-arginine, α-ketoglutaric acid, α-cyclodextrin) were determined. Statistically significant results were limited to the litter
layers, with no significant observations in either the H or Ah horizons. There were significant decreases in the soil microbial
biomass and microbial activity in the litter layers caused by the addition of earthworms; liming reduced microbial biomass
only. The addition of earthworms caused a significant difference in the PLFA principle component analysis (PCA) profile, as
did liming. For the PLFA PCA profile, earthworm plus lime treatment was indistinguishable from the liming result. Addition
of earthworms significantly suppressed the response to glucose; this effect was removed by liming. This indicates that liming
may significantly alter the ecological interactions between earthworms and the microbial community. 相似文献
12.
华北平原典型农田土壤微生物生物量碳氮磷库的县域分布特征——以河北省曲周县为例 总被引:2,自引:1,他引:2
土壤微生物生物量是土壤中的活性养分库,直接参与土壤碳氮磷硫等元素的形态转化与生物地球化学循环过程,是反映土壤肥力与质量的重要生物指标。基于网格法采样,运用地统计学方法分析华北平原典型农田土壤微生物生物量碳氮磷库的空间分布特征及影响因子。结果表明:河北省曲周县域农田耕层(0~30 cm)土壤微生物生物量库在空间上呈斑块状分布,具有中等变异强度和明显的空间自相关性,微生物生物量碳(MBC)、微生物生物量氮(MBN)、微生物生物量磷(MBP)库储量分别为(C)64.14×103t、(N)24.55×103t、(P)2.80×103t,作物产量与MBC和MBN存在显著正相关关系。不同种植体系下单位质量土壤MBC、MBN、MBP的量存在显著差异,小麦/玉米轮作体系下单位质量土壤微生物生物量的平均量高于棉花连作。土壤微生物生物量库的大小和空间分布均受种植体系和土壤肥力的影响,其中土壤有机碳含量是影响土壤微生物生物量库容及空间分布的一个主要因子。研究结果表明土壤微生物生物量库是我国北方典型农田土壤中不可忽视的潜在有效养分库。 相似文献
13.
Soil microbial communities and their activities are altered by land use change; however impacts and extent of these alterations are often unclear. We investigated the functional responses of soil microbes in agricultural soil under sugarcane and corresponding native soil under Eucalyptus forest to additions of contrasting plant litter derived from soybean, sugarcane and Eucalyptus in a microcosm system, using a suite of complimentary techniques including enzyme assays and community level physiological profiles (CLPP). Initially agricultural soil had 50% less microbial biomass and lower enzyme activities than forest soil, but significantly higher nitrification rates. In response to litter addition, microbial biomass increased up to 11-fold in agricultural soil, but only 1.8-fold in forest soil, suggesting a prevalence of rapidly proliferating ‘r’ and slower growing ‘K’ strategists in the respective soils. Litter-driven change in microbial biomass and activities were short lived, largely returning to pre-litter addition levels by day 150. Decomposition rates of sugarcane and soybean litter as estimated via CO2 production were lower in agricultural than in forest soil, but decomposition of more recalcitrant Eucalyptus litter was similar in both soils, contradicting the notion that microbial communities specialise in decomposing litter of the dominant local plant species. Enzyme activities and community level physiological profiles (CLPP) were closely correlated to microbial biomass and overall CO2 production in the agricultural soil but not the forest soil, suggesting contrasting relationships between microbial population dynamics and activity in the two soils. Activities of enzymes that break down complex biopolymers, such as protease, cellulase and phenol oxidase were similar or higher in the agricultural soil, which suggests that the production of extracellular biopolymer-degrading enzymes was not a factor limiting litter decomposition. Enzyme and CLPP analyses produced contrasting profiles of microbial activity in the two soils; however the combination of both analyses offers additional insights into the changes in microbial function and community dynamics that occur after conversion of forest to agricultural land. 相似文献
14.
Jürgen K. Friedel Otto Ehrmann Michael Pfeffer Michael Stemmer Tobias Vollmer Michael Sommer 《植物养料与土壤学杂志》2006,169(2):175-184
Microbial biomass, respiratory activity, and in‐situ substrate decomposition were studied in soils from humid temperate forest ecosystems in SW Germany. The sites cover a wide range of abiotic soil and climatic properties. Microbial biomass and respiration were related to both soil dry mass in individual horizons and to the soil volume in the top 25 cm. Soil microbial properties covered the following ranges: soil microbial biomass: 20 µg C g–1–8.3 mg C g–1 and 14–249 g C m–2, respectively; microbial C–to–total organic C ratio: 0.1%–3.6%; soil respiration: 109–963 mg CO2‐C m–2 h–1; metabolic quotient (qCO2): 1.4–14.7 mg C (g Cmic)–1 h–1; daily in‐situ substrate decomposition rate: 0.17%–2.3%. The main abiotic properties affecting concentrations of microbial biomass differed between forest‐floor/organic horizons and mineral horizons. Whereas microbial biomass decreased with increasing soil moisture and altitude in the forest‐floor/organic horizons, it increased with increasing Ntot content and pH value in the mineral horizons. Quantities of microbial biomass in forest soils appear to be mainly controlled by the quality of the soil organic matter (SOM), i.e., by its C : N ratio, the quantity of Ntot, the soil pH, and also showed an optimum relationship with increasing soil moisture conditions. The ratio of Cmic to Corg was a good indicator of SOM quality. The quality of the SOM (C : N ratio) and soil pH appear to be crucial for the incorporation of C into microbial tissue. The data and functional relations between microbial and abiotic variables from this study provide the basis for a valuation scheme for the function of soils to serve as a habitat for microorganisms. 相似文献
15.
M. von Lützow L. Zelles I. Scheunert J. C. G. Ottow 《Biology and Fertility of Soils》1992,13(3):130-134
Summary Seasonal effects of liming, irrigation, and acid precipitation on microbial biomass N and some physicochemical properties of different topsoil horizons in a spruce forest (Picea abies L.) were measured throughout one growing season. The highest biomass N was recorded in autumn and spring in the upper soil horizons, while the lowest values were obtained in summer and in deeper horizons. The clearest differences between the different soil treatments were apparent in autumn and in the upper horizons. Liming increased the microbial biomass N from 1.7% of the total N content to 6.8% (Olf1 layer) and from 1% to 2% of the total N content in the Of2 layer. The main inorganic-N fraction in the deeper horizons was NO
inf3
sup-
. An increase in cation exchange capacity was observed down to the Oh layer, while soil pH was only slightly higher in the Olf1 and Of2 layers after liming. The effects of irrigation were less marked. The microbial biomass N increased from 1.7% of total N to 4.8% in the Olf1 layer and from 1% to 2% of total N in the Of2 layer. In the Olf1 layer an increase in C mineralization was observed. Acid precipitation decreased the microbial biomass N in the upper horizons from 4.8% of total N to 1.8% in the Olf1 layer and from 2% to 0.5% in the Of2 layer. No significant changes in soil pH were observed, but the decrease in cation exchange capacity may result in a decrease in the proton buffering capacity in the near future. 相似文献
16.
Limitations to the respiratory activity of heterotrophic soil microorganisms exert important controls of CO2 efflux from soils. In the northeastern US, ecosystem nutrient status varies across the landscape and changes with forest succession following disturbance, likely impacting soil microbial processes regulating the transformation and emission of carbon (C). We tested whether nitrogen (N) or phosphorus (P) limit the mineralization of soil organic C (SOC) or that of added C sources in the Oe horizon of successional and mature northern hardwood forests in three locations in central New Hampshire, USA. Added N reduced mineralization of C from SOC and from added leaf litter and cellulose. Added P did not affect mineralization from SOC; however, it did enhance mineralization of litter- and cellulose- C in organic horizons from all forest locations. Added N increased microbial biomass N and K2SO4-extractable DON pools, but added P had no effect. Microbial biomass C increased with litter addition but did not respond to either nutrient. The direction of responses to added nutrients was consistent among sites and between forest ages. We conclude that in these organic horizons limitation by N promotes mineralization of C from SOC, whereas limitation by P constrains mineralization of C from new organic inputs. We also suggest that N suppresses respiration in these organic horizons either by relieving the N limitation of microbial biomass synthesis, or by slowing turnover of C through the microbial pool; concurrent measures of microbial growth and turnover are needed to resolve this question. 相似文献
17.
Alberto Agnelli Judith Ascher Maria Teresa Ceccherini Giacomo Pietramellara 《Soil biology & biochemistry》2004,36(5):859-868
We studied the distribution of the indigenous bacterial and fungal communities in a forest soil profile. The composition of bacterial and fungal communities was assessed by denaturing gradient gel electrophoresis (DGGE) of total and extracellular DNA extracted from all the soil horizons. Microbial biomass C and basal respiration were also measured to assess changes in both microbial biomass and activity throughout the soil profile. The 16S rDNA-DGGE revealed composite banding patterns reflecting the high bacterial diversity as expected for a forest soil, whereas 18S rDNA-DGGE analysis showed a certain stability and a lower diversity in the fungal communities. The banding patterns of the different horizons reflected changes in the microbial community structure with increasing depth. In particular, the DGGE analysis evidenced complex banding patterns for the upper A1 and A2 horizons, and a less diverse microflora in the deeper horizons. The low diversity and the presence of specific microbial communities in the B horizons, and in particular in the deeper ones, can be attributed to the selective environment represented by this portion of the soil profile. The eubacterial profiles obtained from the extracellular DNA revealed the presence of some bands not present in the total DNA patterns. This could be interpreted as the remainders of bacteria not any more present in the soil because of changes of edaphic conditions and consequent shifting in the microbial composition. These characteristic bands, present in all the horizons with the exception of the A1, should support the concept that the extracellular DNA is able to persist within the soil. Furthermore, the comparison between the total and extracellular 16S rDNA-DGGE profiles suggested a downwards movement of the extracellular DNA. 相似文献
18.
Plant canopy effects on litter accumulation and soil microbial biomass in two temperate forests 总被引:2,自引:0,他引:2
The objective of this study was to determine whether differences in canopy structure and litter composition affect soil characteristics
and microbial activity in oak versus mixed fir-beech stands. Mean litter biomass was greater in mixed fir-beech stands (51.9t
ha−1) compared to oak stands (15.7t ha−1). Canopy leaf area was also significantly larger in mixed stands (1.96m2 m−2) than in oak stands (1.73m2 m−2). Soil organic carbon (C
org) and moisture were greater in mixed fir-beech stands, probably as a result of increased cover. Soil microbial biomass carbon
(C
mic), nitrogen (N
mic), and total soil nitrogen (N
tot) increased slightly in the mixed stand, although this difference was not significant. Overall, mixed stands showed a higher
mean C
org/N
tot ratio (22.73) compared to oak stands (16.39), indicating relatively low rate of carbon mineralization. In addition, the percentage
of organic C present as C
mic in the surface soil decreased from 3.17% in the oak stand to 2.26% in the mixed stand, suggesting that fir-beech litter may
be less suitable as a microbial substrate than oak litter. 相似文献
19.
The objectives of this work were to (a) investigate the short-term effects of applications of mineral fertilizer, municipal
solid waste (MSW) compost, and two sewage sludges (SSs) subjected to different treatments (composting and thermal drying)
on microbial biomass and activity of soil by measuring microbial biomass C, adenosine 5′-triphosphate content, basal respiration,
and dehydrogenase, catalase, urease, phosphatase, β-glucosidase, and N-α-benzoyl-l-argininamide-hydrolyzing activities and (b) explore the relationships between soil microbiological, biochemical, and chemical
properties and wheat yields under semiarid field conditions by principal component analysis. The additions of MSW compost,
SS compost, and thermally dried SS did not affect significantly soil microbial biomass, as compared to mineral fertilization
and no amendment. However, microbial activity increased in organically amended soils, probably due to the stimulating effect
of the added decomposing organic matter. Changes in soil microbiological and biochemical properties showed no significant
relationships with wheat yields, probably because plant growth was primarily water-limited, as typically occurs in semiarid
regions. 相似文献
20.
Influence of soil properties on microbial populations, activity and biomass in humid subtropical mountainous ecosystems of India 总被引:1,自引:0,他引:1
Microbial populations, biomass, soil respiration and enzyme activities were determined in slightly acid organic soils of
major mountainous humid subtropical terrestrial ecosystems, along a soil fertility gradient, in order to evaluate the influence
of soil properties on microbial populations, activity and biomass and to understand the dynamics of the microbial biomass
in degraded ecosystems and mature forest. Although the population of fungi was highest in the undisturbed forest (Sacred Grove),
soil respiration was lowest in the 7-year-old regrowth and in natural grassland (approximately 373 μg g–1 h–1). Dehydrogenase and urease activities were high in "jhum" fallow, and among the forest stands they were highest in the 7-year-old
regrowth. Microbial biomass C (MBC) depended mainly on the organic C status of the soil. The MBC values were generally higher
in mature forest than in natural grassland, 1-year-old jhum fallow and the 4-year-old alder plantation. The MBC values obtained
by the chloroform-fumigation-incubation technique (330–1656 μg g–1) did not vary significantly from those obtained by the chloroform-fumigation-extraction technique (408–1684 μg g–1), however, the values correlated positively (P<0.001). The enzyme activities, soil respiration, bacterial and fungal populations and microbial biomass was greatly influenced
by several soil properties, particularly the levels of nutrients. The soil nutrient status, microbial populations, soil respiration
and dehydrogenase activity were greater in Sacred Grove, while urease activity was greater in grassland.
Received: 14 October 1998 相似文献