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1.
Elevated concentration of atmospheric carbon dioxide will affect carbon cycling in terrestrial ecosystems. Possible effects include increased carbon input into the soil through the rhizosphere, altered nutrient concentrations of plant litter and altered soil moisture. Consequently, the ongoing rise in atmospheric carbon dioxide might indirectly influence soil biota, decomposition and nutrient transformations.N-mineralisation and activities of the enzymes invertase, xylanase, urease, protease, arylsulfatase, and alkaline phosphatase were investigated in spring and summer in calcareous grassland, which had been exposed to ambient and elevated CO 2 concentrations (365 and 600 μl l −1) for six growing seasons.In spring, N-mineralisation increased significantly by 30% at elevated CO 2, while there was no significant difference between treatments in summer (+3%). The response of soil enzymes to CO 2 enrichment was also more pronounced in spring, when alkaline phosphatase and urease activities were increased most strongly by 32 and 21%. In summer, differences of activities between CO 2 treatments were greatest in the case of urease and protease (+21 and +17% at elevated CO 2).The stimulation of N-mineralisation and enzyme activities at elevated CO 2 was probably caused by higher soil moisture and/or increased root biomass. We conclude that elevated CO 2 will enhance below-ground C- and N-cycling in grasslands. 相似文献
2.
通过盆栽试验,分析了不同来源有机物料(鸡粪、牛粪、菇渣)对菜用蚕豆生长和品质、根际土化学和生物学性状的影响。结果表明:(1)3种有机物料对蚕豆分枝数、荚干重、籽粒干重、大粒重、大粒蚕豆占比、籽粒淀粉含量均有积极作用,其中牛粪和菇渣能显著(P<0.05)提高大粒蚕豆占比,鸡粪能显著(P<0.05)提高二粒荚和三粒荚的占比,并且对籽粒淀粉含量的提升效果最为明显(比对照增加69.1%);(2)3种有机物料增加了根际土中细菌、真菌数量,显著(P<0.05)提高了根际土中性转化酶、脲酶、酸性磷酸酶、多酚氧化酶活性(除牛粪使中性转化酶活性提高不显著外),其中鸡粪对细菌数量、中性转化酶活性、脲酶活性的提高程度均最大;(3)鸡粪能显著(P<0.05)增加根际土有机碳、全氮、NH 4+-N含量,牛粪、鸡粪能显著(P<0.05)提高土壤p H。大粒蚕豆占比与土壤酸性磷酸酶活性、有效磷含量呈显著正相关。蚕豆淀粉含量与细菌数量、中性转化酶活性、有机碳、全氮、NH 4+-N含量呈显著正相关,这说明有... 相似文献
3.
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 CO 2–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)Δ t, 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 Δ t 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
4.
The long-term (9 years) effect of pig slurry applications vs mineral fertilization on denitrifying activity, N 2O production and soil organic carbon (C) (extractable C, microbial biomass C and total organic C) was compared at three soil depths of adjacent plots. The denitrifying activities were measured on undisturbed soil cores and on sieved soil samples with acetylene method to estimate denitrification rates under field or potential conditions. Pig slurry applications had a moderate impact on the C pools. Total organic C was increased by +6.5% and microbial biomass C by ≥25%. The potential denitrifying activity on soil suspension was stimulated (×1.8, P<0.05) 12 days after the last slurry application. This stimulation was still apparent, but not significant, 10 months later and, according to both methods of denitrifying activity measurement ( r
2=0.916, P<0.01 on sieved soil; r
2=0.845, P<0.001 on soil cores), was associated with an increase in microbial biomass C above a threshold of about 105 mg kg −1. The effect of pig slurry on denitrification and N 2O reduction rates was detected on the surface layer (0–20 cm) only. However, no pig slurry effect could be detected on soil cores at field conditions or after NO 3
− enrichments at 20°C. Although the potential denitrifying activity in sieved soil samples was stimulated, the N 2O production was lower ( P<0.03) in the plot fertilized with pig slurry, indicating a lower N 2O/(N 2O + N 2) ratio of the released gases. The pig-slurry-fertilized plot also showed a higher N 2O reduction activity, which is coherent with the lower N 2O production in anaerobiosis. 相似文献
5.
The North Otago Rolling Downlands (NORD) of New Zealand is currently undergoing a large change in land use with subsequent intensification as a result of a new large community irrigation scheme. To assess the effect of this change, a 4‐year monitoring survey was established on two common Pallic soil types of the area to determine the influence of irrigation term (short, <5 years vs. long, >5 years) and grazing animal (cattle vs. sheep) on a range of physical and organic matter soil quality parameters. This 4‐year survey also included the historical land use of dryland sheep farming in the absence of irrigation water. Irrigation term had no significant ( P > 0.05) effect on soil physical parameters (percentage macroporosity and bulk density) for 3 of 4 years and no significant effect ( P > 0.05) on topsoil total carbon or nitrogen contents. However, irrigation term had a significant ( P < 0.01) but biologically small effect on the ratio of carbon to nitrogen with narrowing of the range under longer term irrigation. A significant difference between the dryland and irrigated surveys was found for macroporosity (dryland sheep 17.3% v/v vs. irrigated sheep 13.4% v/v; P < 0.001) and for the C:N ratio (dryland sheep 10.7 vs. irrigated sheep 10.2; P < 0.05). The change in macroporosity under irrigation is likely to take effect within 1 or 2 years of land‐use change as little discernable differences in soil physical properties were evident from land under short‐ or long‐term irrigation. 相似文献
6.
探讨秸秆还田与施氮对高纬度黑土区春玉米产量与温室气体排放特性的影响,对促进粮食增产和降低环境代价具有重要意义。本研究通过位于黑土区的大田定位试验,利用静态箱-气相色谱计数方法,在秸秆还田与不还田和3个氮素用量(纯N:120 kg·hm~(-2),240 kg·hm~(-2)和300 kg·hm~(-2))条件下,研究了春玉米不同生育时期农田土壤CO2、N2O和CH4综合温室效应与排放强度,以及土壤过氧化氢酶和脲酶活性的变化。结果表明:无秸秆还田时,高氮用量处理春玉米产量最高;秸秆还田后,中等氮用量处理(240 kg·hm~(-2))春玉米产量最高,且与无秸秆还田的高氮处理间无显著差异。无秸秆还田时,随施氮量增加,CO2、N2O和CH4排放量均显著提高,综合温室效应和土壤温室气体排放量与强度显著增加(P0.05);增施氮肥配合秸秆还田,增加了CO2和N2O的排放量,而土壤CH4的碳汇功能增强,温室气体排放量与强度未显著提高(P0.05)。无秸秆还田,增施氮肥降低了土壤过氧化氢酶活性但提高了土壤脲酶活性;而秸秆还田使得增施氮肥引起的土壤过氧化氢酶活性降低的幅度加大但土壤脲酶活性提高的幅度变小。因此,秸秆还田后配合中等用量氮处理(240 kg·hm~(-2))玉米产量最高,且能够抑制单纯增施氮肥对综合温室效应和土壤温室气体排放强度的促进作用,推荐在生产中参考使用。 相似文献
7.
In this study, we investigated the effects of lanthanum (La), one of the rare earth elements (REEs), on microbial biomass
C as well as the decomposition of 14C-labelled glucose in a fluvo-aquic soil in 28 days. The soil was collected from the field plots under maize/wheat rotation
in Fengqiu Ecological Experimental Station of Chinese Academy of Sciences, Henan Province, China. Application of La decreased
soil microbial biomass C during the experimental period, and there was a negative correlation ( P < 0.01) between microbial biomass and application rate of La. La increased microbial biomass 14C after 14C glucose addition, and the increase was significant ( P < 0.05) at the rates of more than 160 mg kg −1 soil. La slightly increased 14CO 2 evolution at lower rates of application but decreased it at higher rates 1 day after 14C glucose addition, while there was no significant effect from days 2 to 28. For the cumulative 14CO 2 evolution during the incubation of 28 days, La slightly increased it at the rates of less than 120 mg kg −1 soil, while significantly decreased ( P < 0.05) it at the rate of 200 mg kg −1 soil. The results indicated that agricultural use of REEs such as La in soil could decrease the amount of soil microbial
biomass and change the pattern of microbial utilization on glucose C source in a short period. 相似文献
8.
Alkaline and acid phosphomonoesterase, β-glucosidase, arylsulfatase, protease and urease activities, CO 2-C evolution and ATP content were monitored in long-term Cd-contaminated (0-40 mg Cd kg −1 dry weight soil) sandy soils, kept under maize or ‘set aside’ regimes, amended with plant residues. The organic matter input increased soil respiration, ATP contents and hydrolase activities in all soils. However, the Cd-contaminated soils had significantly higher metabolic quotients ( qCO 2), as calculated by the CO 2-to-ATP ratio, and significantly lower hydrolase activities and hydrolase activity-to-ATP ratios for alkaline phosphomonoesterase, arylsulfatase and protease activities, compared with the respective uncontaminated soils. The ratios between acid phosphomonoesterase, β-glucosidase and urease activities and ATP were unaffected. A significantly higher qCO 2/ μ ratio, an expression of maintenance energy, was observed in most of the contaminated soils, indicating that more energy was required for microbial synthesis in the presence of high Cd concentrations. It was concluded that exposure to high Cd concentrations led to a less efficient metabolism, which was responsible for lower enzyme activity and synthesis and lower hydrolase activity-to-ATP ratios observed in these Cd-contaminated soils. 相似文献
9.
To gain insight into microbial function following increased atmospheric CO 2 concentration, we investigated the influence of 9 years of enriched CO 2 (600 μl litre −1) on the function and structural diversity of soil microorganisms in a grassland ecosystem under free air carbon dioxide enrichment (FACE), as affected by plant species ( Trifolium repens L. and Lolium perenne L. in monocultures and mixed culture) and nitrogen (N) supply. We measured biomass and activities of enzymes covering cycles of the most important elements (C, N and P). The microbial community was profiled by molecular techniques of phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analysis. The enrichment in CO 2 increased soil microbial biomass (+48.1%) as well as activities of invertase (+36.2%), xylanase (+22.9%), urease (+23.8%), protease (+40.2%) and alkaline phosphomonoesterase (+54.1%) in spring 2002. In autumn, the stimulation of microbial biomass was 25% less and that of enzymes 3–12% less than in spring. Strong correlations between activities of invertase, protease, urease and alkaline phosphomonoesterase and microbial biomass were found. The stimulation of microbial activity in the enriched atmosphere was probably caused by changes in the quantity and kind of root litter and rhizodeposition. The response of soil microorganisms to enriched CO 2 was most pronounced under Trifolium monoculture and under greater N supply. The PLFA analysis revealed that total PLFA contents were greater by 24.7% on average, whereby the proportion of bioindicators representative of Gram‐negative bacteria increased significantly in the enriched CO 2 under less N‐fertilized Lolium culture. Discriminant analysis showed marked differences between the PLFA profiles of the three plant communities. Shannon diversity indices calculated from DGGE patterns were greater (+12.5%) in the enriched CO 2, indicating increased soil bacterial diversity. We conclude that greater microbial biomass and enzyme activity buffer the potential increase in C sequestration occurring from greater C addition in enriched CO 2 due to greater mineralization of soil organic matter. 相似文献
10.
Hierarchical Bayesian (HB) methods are useful tools for modeling multifaceted, nonlinear phenomena such as those encountered in ecology, and have been increasingly applied in environmental sciences, e.g., to estimate soil gas flux from different soil textures or sites. We have developed a model of soil carbon dioxide (CO 2) flux based on soil temperature ( T, 5 cm depth) and water-filled pore space (WFPS, 5 cm depth) using HB theory. The HB model was calibrated using a dataset of CO 2 flux measured from bare soils belonging to four texture classes in 14 upland field sites in a watershed in central Hokkaido, Japan, in the nonsnow-cover season from 2003 to 2011. The numerical software HYDRUS-1D was used to simulate daily WFPS, and the estimated values were significantly correlated with the measured WFPS ( R2 = 0.68, P < 0.001). Compared to a nonhierarchical Bayesian model (Bayesian pooled model), the CO 2 predictions with the HB model more accurately represented texture-specific observations. The simulation–observation fit of the CO 2 flux model was R2 = 0.64 ( P < 0.001). More than 90% of the observed daily data were within the 95% confidence interval. The HB model exhibited high uncertainty for high CO 2 flux values. The HB model calibration revealed differing sensitivity of CO 2 flux to T and WFPS in different soil texture classes. CO 2 flux increased with an increase in T, and it increased to a lesser degree with a finer texture, possibly because the clay and silt facilitated soil aggregation, thus reducing temperature fluctuations. WFPS values between 0.48 and 0.64 resulted in optimal conditions for CO 2 flux. The minimum WFPS value increased with an increase in clay content ( P < 0.05). Although only a small number of soil types were studied in only one season in this study, the HB model may provide a method for predicting how the effects of soil temperature and moisture on CO 2 flux change with texture, and soil texture could be regarded as an upscaling factor in future research on regional extrapolation. 相似文献
11.
Soil cultivation changes and usage of agricultural wastes can have profound impacts on greenhouse gas (GHG) emission from soil. In this study, the effects of soil cultivation and organic amendment on GHG emission were investigated using aerobic incubation. Surface soil (0–20 cm) from (1) rice–legume consecutive rotation (Rice) and (2) recently (<3 years) converted from rice field to plastic-covered intensive vegetable and flower production (VegC) were collected in Kunming, P.R. China. Rose ( Rosa rugosa Thunb.) residues and cattle manure were applied at 5% by weight. Results indicated that N 2O and CO 2 fluxes were significantly influenced by soil cultivation, organic amendment, incubation time and their interaction ( p <0.05). Applying cattle manure increased, while rose residue decreased, cumulative N 2O emissions from soil (84 days). Rose residue application significantly increased cumulative CO 2 emissions with peak values of 6371 (Rice) and 7481 mg kg ?1 (VegC), followed by cattle manure addition figure of 2265 (VegC) and 3581 mg kg ?1 (Rice). Both were significantly higher ( p <0.05) than the un-amended Control at 709 (VegC) and 904 mg kg ?1 (Rice). Our study demonstrates that a low C/N ratio in cattle manure is better than a high C/N ratio in rose residue in regard to reducing the global warming potential of agricultural soil. 相似文献
12.
In semi-arid regions wastewater irrigation is a valuable resource for agricultural production. The contamination of irrigated
soils with surfactants is one of the ecological risks related to irrigating with untreated wastewater. In this study, the
effects of branched alkylbenzene sulfonates (ABS) on microbial biomass, respiratory activity, and denitrification capacity
of soil samples (eutric vertisols) taken from an irrigation district in the Mexico City area were investigated in laboratory
experiments. Increasing concentrations of ABS lead to a decrease in soil microbial biomass and an increase in soil respiratory
activity as well as in the metabolic quotient ( qCO 2) of the soils. Denitrification capacity was lowest without the addition of ABS and highest at a medium ABS concentration
of 50 μg g –1. Denitrification capacity seems to be highly sensitive to ABS addition at moderate concentrations. From the laboratory results,
high rates of denitrification and N 2O evolution from fields irrigated with wastewater containing ABS are expected.
Received: 11 November 1997 相似文献
13.
Abstract The study aimed at quantifying the rates of soil CO 2 efflux under the influence of common tillage systems of moldboard plow (PT), chisel plow (CT), rotary tiller (RT), heavy disc harrow (DT), and no-tillage (NT) for 46 days in October and November in a field left fallow after wheat harvest located in southern Turkey. The NT and DT plots produced the lowest soil CO 2 effluxes of 0.3 and 0.7 g m ?2 h ?1, respectively, relative to the other plots ( P < 0.001). Following the highest rainfall amount of 87 mm on the tenth day after the tillage, soil CO 2 efflux rates of all the plots peaked on the 12th day, with less influence on soil CO 2 efflux in the NT plot than in the conventional tillage plots. Soil evaporation in NT (64 mmol m ?2 s ?1) was significantly lower than in the PT (85 mmol m ?2 s ?1) and RT (89 mmol m ?2 s ?1) tillage treatments ( P < 0.01). The best multiple-regression model selected explained 46% of variation in soil respiration rates as a function of the tillage treatments, soil temperature, and soil evaporation ( P < 0.001). The tillage systems of RT, PT, and CT led, on average, to 0.23, 0.22, and 0.18 g m ?2 h ?1 more soil CO 2 efflux than the baseline of NT, respectively ( P≤0.001). 相似文献
14.
To determine the sum of ‘direct’ and ‘indirect’ effects of climatic change on enchytraeid activity and C fluxes from an organic soil we assessed the influence of temperature (4, 10 and 15 °C incubations) on enchytraeid populations and soil CO 2 and CH 4 fluxes over 116 days. Moisture was maintained at 60% of soil dry weight during the experimental period and measurements of enchytraeid biomass and numbers, and CO 2 and CH 4 fluxes were made after 3, 16, 33, 44, 65, 86 and 116 days. Enchytraeid population numbers and biomass increased in all temperature treatments with the greatest increase produced at 15 °C (to over threefold initial values by day 86). Results also showed that enchytraeid activity increased CO 2 fluxes by 10.7±4.5, 3.4±4.0 and 26.8±2.6% in 4, 10 and 15 °C treatments, respectively, with the greatest CO 2 production observed at 15 °C for the entire 116 day incubation period ( P<0.05). The soil respiratory quotient analyses at lower temperatures (i.e. 4-10 °C) gave a Q 10 of 1.7 and 1.9 with and without enchytraeids, respectively. At temperatures above 10 °C (i.e. 10-15 °C) Q 10 significantly increased ( P<0.01) and was 25% greater in the presence of enchytraeids (Q 10=3.4) than without (Q 10=2.6). In contrast to CO 2 production, no significant relationships were observed between net CH 4 fluxes and temperature and only time showed a significant effect on CH 4 production ( P<0.01).Total soil CO 2 production was positively linked with enchytraeid biomass and mean soil CO 2-C production was 77.01±6.05 CO 2-C μg mg enchytraeid tissue −1 day −1 irrespective of temperature treatment. This positive relationship was used to build a two step regression model to estimate the effects of temperature on enchytraeid biomass and soil CO 2 respiration in the field. Predictions of potential CO 2 production were made using enchytraeid biomass data obtained in the field from two upland grassland sites (Sourhope and Great Dun Fell at the Moor House Nature Reserve, both in the UK). The findings of this work suggest that a 5 °C increase in atmospheric temperature above mean ambient temperature could have the potential to produce a significant increase in enchytraeid biomass resulting in a near twofold increase in soil CO 2 release from both soil types. The interaction between temperature and soil biology will clearly be an important determinant of soil respiration responses to global warming. 相似文献
15.
In order to investigate the effects of microorganisms and their urease activities in macrophytic root zones on pollutant removal, four small-scale plots (SSPs) of vertical/reverse-vertical flow wetlands were set up to determine: a) the relationship between the abundance of microorganisms in the root zones and water purification efficiency; and b) the relationship between urease activities in the root zones and pollutant removal in a constructed wetland system. Total numbers of the microbial population (bacteria, fungi, and actinomyces) along with urease activities in the macrophytic root zones were determined. In addition, the relationships between microbial populations and urease activities as well as the wastewater purification efficiencies of total phosphorus (TP), total Kjeldahl nitrogen (TKN), biochemical oxygen demand in 5 days (BOD 5), and chemical oxygen demand (COD) were also analyzed. The results showed that there was a highly significant positive correlation ( r = 0.9772, P < 0.01) between the number of bacteria in the root zones and BOD 5 removal efficiency and a significant negative correlation ( r = -0.9092, P < 0.05) between the number of fungi and the removal efficiency of TKN. Meanwhile, there was a significant positive correlation ( r = 0.8830, P < 0.05) between urease activities in the root zones and the removal efficiency of TKN. Thus, during wastewater treatment in a constructed wetland system, microorganism and urease activities in the root zones were very important factors. 相似文献
16.
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 CO 2 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 CO 2 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 CO 2 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
17.
选取祁连山排露沟流域海拔2 900~3 300 m的青海云杉林为研究对象,通过野外采样和室内分析,研究了不同海拔梯度青海云杉林土壤理化性质和酶活性的分布特征,并探讨二者之间的关系。结果表明:(1)随着海拔的升高,土壤含水量、有机质、全氮、速效钾含量逐渐增大;而土壤容重、pH、全钾含量逐渐减小;土壤全磷含量先减小后增大,速效磷含量没有明显的变化规律。(2)随着海拔的升高,土壤蔗糖酶活性和碱性磷酸酶活性总体上呈增强趋势;脲酶活性总体上呈先减弱后增强趋势,蛋白酶活性变化幅度较小且差异不显著(P0.05)。(3)土壤酶活性和土壤有机质、氮、磷、钾等密切相关,其中蔗糖酶、脲酶、蛋白酶与土壤全氮、全钾、速效钾具有显著相关性(P0.05)。(4)4种土壤酶活性间呈显著或极显著相关,酶促反应具专一性和共同性特点。 相似文献
18.
Land‐use change and soil management play a vital role in influencing losses of soil carbon (C) by respiration. The aim of this experiment was to examine the impact of natural vegetation restoration and long‐term fertilization on the seasonal pattern of soil respiration and cumulative carbon dioxide (CO 2) emission from a black soil of northeast China. Soil respiration rate fluctuated greatly during the growing season in grassland (GL), ranging from 278 to 1030 mg CO 2 m ?2 h ?1 with an average of 606 mg CO 2 m ?2 h ?1. By contrast, soil CO 2 emission did not change in bareland (BL) as much as in GL. For cropland (CL), including three treatments [CK (no fertilizer application), nitrogen, phosphorus and potassium application (NPK), and NPK together with organic manure (OM)], soil CO 2 emission gradually increased with the growth of maize after seedling with an increasing order of CK < NPM < OM, reaching a maximum on 17 August and declining thereafter. A highly significant exponential correlation was observed between soil temperature and soil CO 2 emission for GL during the late growing season (from 3 August to 28 September) with Q 10 = 2.46, which accounted for approximately 75% of emission variability. However, no correlation was found between the two parameters for BL and CL. Seasonal CO 2 emission from rhizosphere soil changed in line with the overall soil respiration, which averaged 184, 407, and 584 mg CO 2 m ?2 h ?1, with peaks at 614, 1260, and 1770 mg CO 2 m ?2 h ?1 for CK, NPK, and OM, respectively. SOM‐derived CO 2 emission of root free‐soil, including basal soil respiration and plant residue–derived microbial decomposition, averaged 132, 132, and 136 mg CO 2 m ?2 h ?1, respectively, showing no difference for the three CL treatments. Cumulative soil CO 2 emissions decreased in the order OM > GL > NPK > CK > BL. The cumulative rhizosphere‐derived CO 2 emissions during the growing season of maize in cropland accounted for about 67, 74, and 80% of the overall CO 2 emissions for CK, NPK, and OM, respectively. Cumulative CO 2 emissions were found to significantly correlate with SOC stocks (r = 0.92, n = 5, P < 0.05) as well as with SOC concentration (r = 0.97, n = 5, P < 0.01). We concluded that natural vegetation restoration and long‐term application of organic manure substantially increased C sequestration into soil rather than C losses for the black soil. These results are of great significance to properly manage black soil as a large C pool in northeast China. 相似文献
19.
An incubation experiment with soil water content treatments of 0.15 (W1), 0.20 (W2), and 0.40 (W3) g g^-1 soil was carried out for two months to investigate the activities of important enzymes involved in C, N, P, and S cycling in a paddy soil from the Taihu Lake region, China, under waterlogged and aerobic conditions. Compared with air-dried soil, waterlogging resulted in a significant decrease (P ≤ 0.05) of fluorescein diacetate (FDA) and /3-D-glucosidase activities, and this effect was enhanced with increasing waterlogging time. Waterlogging also significantly inhibited (P ≤ 0.05) arylsulfatase as well as alkaline and acid phosphatase activities, but did not decrease the activities with the increase in waterlogging time. Short-term waterlogging did not affect urease activity, but prolonged waterlogging decreased it markedly. In contrast, the aerobic incubation (W1 and W2 treatments) significantly increased (P ≤ 0.05) FDA, alkaline phosphatase, and /3-D-glucosidase activities. With aerobic treatments the activities of FDA and alkaline phosphatase increased with incubation time, whereas /3-D-glucosidase activity decreased. A significant difference (P ≤ 0.05) was usually observed between the W1 and W2 treatments for the activities of FDA as well as alkaline and acid phosphatase; however,/3-D-glucosidase and urease were usually not significant (P ≤ 0.05). No activity differences were observed between waterlogging and aerobic incubation for arylsulfatase and urease. 相似文献
20.
PurposeA large-scale managed reed wetland in Yancheng Biosphere Reserve of China has been irrigated by treated papermaking wastewater (TPW) for approximately 8 to 12 years. This report details the risk evaluation of long-term TPW irrigation on the soil and its microbial viability, providing important perspective on the suitability of TPW reuse for irrigation. Materials and methodsAn extensive field survey was employed for assessing the impacts of long-term TPW irrigation of reed fields (F1 to F6), as compared to river water irrigated field, on soil physicochemical properties, accumulation of heavy metals (Cu, Cd, Pb), soil enzyme activities (i.e., urease, invertase, catalase, and polyphenol oxidase), and soil microbial community metabolic profiles. Results and discussionThe results revealed that long-term TPW reuse for irrigation resulted in a slight increase of pH value, while a remarkable increase was identified regarding to soil organic carbon, as expected from the organic carbon content of the wastewater, but was not proportional to the time of irrigation. TPW irrigation caused a remarkable increase in soil electrical conductivity and resulted in soil salinization, having strong correlation with the duration of irrigation. Soil salinization increase in irrigated area was mainly due to the high sodium content of the wastewater applied for irrigation. Furthermore, soil enzymes displayed significantly increased activities (except for catalase) in the irrigated fields, while the microbial ability of utilizing carbon source was enhanced. The diversity of microbial communities was boomed due to the increase of soil organic matter, as evidenced by the calculated diversity indices. However, a remarkable increase of heavy metals was also identified regarding Cd and Pb concentrations, which may pose potential risks to human health. ConclusionsThe input of excessive pollutants and nutrients will disrupt the equilibrium mechanism of the wetland ecosystem. Although long-term TPW irrigation may increase the soil fertility and microbial activity, heavy metals (i.e., Cd and Pb) in wastewater can be accumulated in the soil. Furthermore, alkaline TPW caused an increase in soil salinity. Therefore, more cautions should be exercised in the reuse of TPW for irrigation. 相似文献
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