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1.
温带针阔混交林土壤碳氮气体通量的主控因子与耦合关系 总被引:3,自引:0,他引:3
中高纬度森林地区由于气候条件变化剧烈,土壤温室气体排放量的估算存在很大的不确定性,并且不同碳氮气体通量的主控因子与耦合关系尚不明确。以长白山温带针阔混交林为研究对象,采用静态箱-气相色谱法连续4a(2005—2009年)测定土壤二氧化碳(CO2)、甲烷(CH4)和氧化亚氮(N2O)净交换通量以及温度、水分等相关环境因子。研究结果表明:温带针阔混交林土壤整体上表现为CO2和N2O的排放源和CH4的吸收汇。土壤CH4、CO2和N2O通量的年均值分别为-1.3 kg CH4hm-2a-1、15102.2 kg CO2hm-2a-1和6.13 kg N2O hm-2a-1。土壤CO2通量呈现明显的季节性规律,主要受土壤温度的影响,水分次之;土壤CH4通量的季节变化不明显,与土壤水分显著正相关;土壤N2O通量季节变化与土壤CO2通量相似,与土壤水分、温度显著正相关。土壤CO2通量和CH4通量不存在任何类型的耦合关系,与N2O通量也不存在耦合关系;土壤CH4和N2O通量之间表现为消长型耦合关系。这项研究显示温带针阔混交林土壤碳氮气体通量主要受环境因子驱动,不同气体通量产生与消耗之间存在复杂的耦合关系,下一步研究需要深入探讨环境变化对其耦合关系的影响以及内在的生物驱动机制。 相似文献
2.
An automated 36 place valve to provide continuous soil respiration measurements was constructed. The valve is fully computer
controlled and can sample and purge the soil atmosphere as frequently as every 75 minutes. The concentrations, automatically
measured by the valve, are essentially identical to those measured manually by gas chromatography in the concentration range
of 0.1 to 1% CO2, and are kept in this range by adjusting the mass of soil and the sampling frequency. Data are transferred automatically
to a computer spreadsheet program for data handling and plotting on either a rate or cumulative basis. The system has proved
reliable over many thousands of analyses and has made detailed analysis of microbial activity on a continuous basis possible. 相似文献
3.
Hiroshi Koizumi Toshie Nakadai Youzou Usami Mitsumasa Satoh Masae Shiyomi Takehisa Oikawa 《Ecological Research》1991,6(3):227-232
In order to assess the validity of conventional methods for measuring CO2 flux from soil, the relationship between soil microbial respiration and ambient CO2 concentration was studied using an open-flow infra-red gas analyser (IRGA) method. Andosol from an upland field in central
Japan was used as a soil sample. Soil microbial respiration activity was depressed with the increase of CO2 concentration in ventilated air from 0 to 1000 ppmv. At 1000 ppmv, the respiration rate was less than half of that at 0 ppmv.
Thus, it is likely that soil respiration rate is overestimated by the alkali absorption method, because CO2 concentration in the absorption chamber is much lower than the normal level. Metabolic responses to CO2 concentration were different among groups of soil microorganisms. The bacteria actinomycetes group cultivated on agar medium
showed a more sensitive response to the CO2 concentration than the filamentous fungi group. 相似文献
4.
Microbial activity is the driving force of the carbon cycle, including the digestion of biomass in the soil, oceans, and oil deposits. This natural diversity of microbial carbon sources poses challenges for humans. Contamination monitoring can be difficult in oil tanks and similar settings. To assess microbial activity in such industrial settings, off‐gas analysis can be employed by considering growth and non‐growth‐associated metabolic activity. In this work, we describe the monitoring of CO2 as a method for measuring microbial activity. We revealed that the CO2 signal corresponds to classical growth curves, exemplified by Pseudomonas fluorescens, Yarrowia lipolytica, and Penicillium chrysogenum. Deviations of the CO2 signal from the growth curves occurred when the yield of biomass on the substrate changed (i.e., the non‐growth‐associated metabolic activities). We monitored CO2 to track the onset of microbial contamination in an oil tank. This experimental setup was applied to determine the susceptibility of heating oil and biodiesel to microbial contamination long before the formation of problematic biofilms. In summary, the measurement of CO2 production by bacteria, yeasts, and molds allowed the permanent monitoring of microbial activity under oil storage conditions without invasive sampling. 相似文献
5.
Anatoly Zyakun Seth Nii-Annang Gabriele Franke Thomas Fischer Franz Buegger Oliver Dilly 《Geomicrobiology journal》2013,30(6):570-584
The dynamics of microbial degradation of exogenous contaminants, n-hexadecane and its primary microbial oxidized metabolite, n-hexadecanoic (palmitic) acid, was studied for topsoils, under agricultural management and beech forest on the basis the changes in O2 uptake, CO2 evolution and its associated carbon isotopic signature, the respiratory quotient (RQ) and the priming effect (PE) of substrates. Soil microbial communities in agricultural soil responded to the n-hexadecane addition more rapidly compared to those of forest soil, with lag-periods of about 23 ± 10 and 68 ± 13 hours, respectively. Insignificant difference in the lag-period duration was detected for agricultural (tlag = 30 ± 13 h) and forest (tlag = 30 ± 14 h) soils treated with n-hexadecanoic (palmitic) acid. These results demonstrate that the soil microbiota has different metabolic activities for using n-hexadecane as a reductive hydrocarbon and n-hexadecanoic acid as a partly oxidized hydrocarbon. The corresponding δ13C of respired CO2 after the addition of the hydrocarbon contaminants to soils indicates a shift in microbial activity towards the consumption of exogenous substrates with a more complete degradation of n-hexadecane in the agricultural soil, for which some initial contents of hydrocarbons are inherent. It is supposed that the observed deviation of RQ from theoretically calculated value under microbial substrate mineralization is determined by difference in the time (Δti) of registration of CO2 production and O2 consumption. Positive priming effect (PE) of n-hexadecane and negative PE of n-hexadecanoic (palmitic) acid were detected in agricultural and forest soils. It is suggested that positive PE of n-hexadecane is conditioned by the induction of microbial enzymes that perform hydroxylation/oxygenation of stable SOM compounds mineralized by soil microbiota to CO2. The microbial metabolism coupled with oxidative decarboxylation of n-hexadecanoic acid is considered as one of the most probable causes of the revealed negative PE value. 相似文献
6.
The variation of soil microbial respiration with depth in relation to soil carbon composition 总被引:1,自引:0,他引:1
The vertical variation in soil microbial respiratory activity and its relationship to organic carbon pools is critical for modeling soil C stock and predicting impacts of climate change, but is not well understood. Mineral soil samples, taken from four Scottish soils at different depths (0–8, 8–16, 16–24, 24–32 cm), were analyzed and incubated in the laboratory under constant temperature and environmental conditions. The vegetation type/plant species showed significant effects on the absolute concentration of C components and microbial activity, but the relative distribution of C and respiration rate with soil depth are similar across sites. Soil C pools and microbial respiratory activity declined rapidly with soil depth, with about 30% of total organic carbon (TOC) and dissolved organic carbon (DOC), and about half microbial carbon (Cmic) and respired CO2 observed in the top 8 cm. The ratio of CO2:TOC generally decreased with soil depth, but CO2:DOC was significantly higher in the top 8 cm of soil than in the subsoil (8–32 cm). No general pattern between qCO2 (CO2:Cmic) and soil depth was found. The vertical distributions of soil C pools and microbial respiratory activity were best fitted with a single exponential equation. Compared with TOC and DOC, Cmic appears to be an adequate predictor for the variation in microbial respiration rate with soil depth, with 95% of variation in normalized respiration rate accounted for by a linear relationship. 相似文献
7.
Summary We have built an autosampler system that delivers the contents of pressurized gas collection vials to the injection port of a gas chromatograph. The three-part system consists of a shuttle base upon which vials move sequentially past a static sampling point, a sampling needle that is driven through vial septa by an air-driven piston, and an air-actuated sample valve that alternately places a sample loop in line with either a sample delivery line from the sample needle or a carrier stream leading to the gas chromatograph. We have used the system to analyze several thousand gas samples taken from soil cores assayed for denitrification activites, and have found the system reliable and capable of producing highly repeatable results.Journal Article No. 11491 of the Michigan State Agricultural Experiment Station, East Lansing, Michigan 48824, USA 相似文献
8.
Increased CO2 fluxes from a sandy Cambisol under agricultural use in the Wendland region,Northern Germany,three years after biochar substrates application
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In recent years, biochar has been discussed as an opportunity for carbon sequestration in arable soils. Field experiments under realistic conditions investigating the CO2 emission from soil after biochar combined with fertilizer additions are scarce. Therefore, we investigated the CO2 emission and its 13C signature after addition of compost, biogas digestate (originating from C4 feedstock) and mineral fertilizer with and without biochar (0, 3, 10, 40 Mg biochar/ha) to a sandy Cambisol in Northern Germany. Biomass residues were pyrolized at ~650°C to obtain biochar with C3 signature. Gas samples were taken biweekly during the growing season using static chambers three years after biochar substrate addition. The CO2 concentration and its δ13C isotope signature were measured using a gas chromatograph coupled to an isotope ratio mass spectrometer. Results showed increased CO2 emission (30%–60%) when high biochar amount (40 Mg/ha) was applied three years ago together with mineral fertilizer and biogas digestate. On average, 59% of the emitted CO2 had a C3 signature (thus, deriving from biochar and/or soil organic matter), independent of the amount of biochar added. In addition, our results clearly demonstrated that only a small amount of released CO2 derived from biochar. The results of this field experiment suggest that biochar most likely stimulates microbial activity in soil leading to increased CO2 emissions derived from soil organic matter and fertilizers mineralization rather than from biochar. Nevertheless, compared to the amount of carbon added by biochar, additional CO2 emission is marginal corroborating the C sequestration potential of biochar. 相似文献
9.
Evaluation of soil respiration and soil CO2 concentration in a lowland moist forest in Panama 总被引:2,自引:0,他引:2
T. A. Kursar 《Plant and Soil》1989,113(1):21-29
Soil gas exchange was investigated in a lowland moist forest in Panama. Soil water table level and soil redox potentials indicate that the soils are not waterlogged. Substantial microspatial variation exists for soil respiration and soil CO2 concentration. During the rainy season, soil CO2 at 40 cm below the surface accumulates to 2.3%–4.6% and is correlated with rainfall during the previous two weeks. Temporal changes in soil CO2 are rapid, large and share similar trends between sampling points. Possible effects of soil CO2 changes on plant growth or phenology are discussed. 相似文献
10.
Non-phototrophic CO
2
fixation by soil microorganisms 总被引:1,自引:0,他引:1
Anja Miltner Frank-Dieter Kopinke Reimo Kindler Draženka Selesi Anton Hartmann Matthias Kästner 《Plant and Soil》2005,269(1-2):193-203
Although soils are generally known to be a net source of CO2 due to microbial respiration, CO2 fixation may also be an important process. The non-phototrophic fixation of CO2 was investigated in a tracer experiment with 14CO2 in order to obtain information about the extent and the mechanisms of this process. Soils were incubated for up to 91 days
in the dark. In three independent incubation experiments, a significant transfer of radioactivity from 14CO2 to soil organic matter was observed. The process was related to microbial activity and could be enhanced by the addition
of readily available substrates such as acetate. CO2 fixation exhibited biphasic kinetics and was linearly related to respiration during the first phase of incubation (about
20–40 days). The fixation amounted to 3–5% of the net respiration. After this phase, the CO2 fixation decreased to 1–2% of the respiration. The amount of carbon fixed by an agricultural soil corresponded to 0.05% of
the organic carbon present in the soil at the beginning of the experiment, and virtually all of the fixed CO2 was converted to organic compounds. Many autotrophic and heterotrophic biochemical processes result in the fixation of CO2. However, the enhancement of the fixation by addition of readily available substrates and the linear correlation with respiration
suggested that the process is mainly driven by aerobic heterotrophic microorganisms. We conclude that heterotrophic CO2 fixation represents a significant factor of microbial activity in soils. 相似文献
11.
Two plant species, Medicago truncatula (legume) and Avena sativa (non-legume), were grown in low-or high-N soils under two CO2 concentrations to test the hypothesis whether C allocation within plant-soil system is interactively or additively controlled
by soil N and atmospheric CO2 is dependent upon plant species. The results showed the interaction between plant species and soil N had a significant impact
on microbial activity and plant growth. The interaction between CO2 and soil N had a significant impact on soil soluble C and soil microbial biomass C under Madicago but not under Avena. Although both CO2 and soil N affected plant growth significantly, there was no interaction between CO2 and soil N on plant growth. In other words, the effects of CO2 and soil N on plant growth were additive. We considered that the interaction between N2 fixation trait of legume plant and elevated CO2 might have obscured the interaction between soil N and elevated CO2 on the growth of legume plant. In low-N soil, the shoot-to-root ratio of Avena dropped from 2.63±0.20 in the early growth stage to 1.47±0.03 in the late growth stage, indicating that Avena plant allocated more energy to roots to optimize nutrient uptake (i.e. N) when soil N was limiting. In high-N soil, the shoot-to-root
ratio of Medicago increased significantly over time (from 2.45±0.30 to 5.43±0.10), suggesting that Medicago plants allocated more energy to shoots to optimize photosynthesis when N was not limiting. The shoot-to-root ratios were
not significantly different between two CO2 levels. 相似文献
12.
The rates of the mineralization processes initiated by the input of plant residues and pyrogenically modified plant material
into gray forest soil under forests and meadows were assayed. While meadow plant residues was mineralized more rapidly than
the forest floor, decomposition of the pyrogenic material resulted in disproportional changes in CO2 emission from soils. Statistical treatment showed that the respiratory activity of CO2 emission by heterotrophic microorganisms, which is a physiological characteristic of microbial communities, is 89% determined
by the substrate quality. The maximal specific growth rate, which reflects the functional changes in microbial communities,
was affected by the cenosis (36%) and the substrate (30%). Most of the carbon of the original plant material (up to 90%) was
removed during the burning of plant substrates. The remaining compounds in the pyrogenically transformed material changed
the process of mineralization in soil compared both to the control variant and to soil enriched with plant residues. Input
of plant residues and ash into the soil resulted in increased total and active biomass, while the maximal specific growth
rate decreased and the generation time for the active biomass increased. In the case of soils with plant residues, these changes
in the state of microbial communities were brief and occurred during the period of intense mineralization (0–5 days), while,
in soils with plant ash, stable changes were revealed after more prolonged incubation. Experimental determination of the microbial
biomass turnover time (MTT) by means of two methods (from the ratio between the microbial biomass and respiration and from
microbial specific growth rates) made it possible to determine the economical coefficient Y for microbial communities metabolizing
the substrates of different availability. Depending on the experimental variant, the Y values varied from 0.22 to 0.51. Decreased
maximal specific growth rate and increased values of Y (the coefficient of efficiency of substrate utilization) showed the
predominant contribution of K-strategists in the mineralization of low available substrates in soil. The balance calculations
and physiological characteristics of the microbial community suggested that the priming effect was most probable in soils
enriched with plant ash. 相似文献
13.
EVGENIA BLAGODATSKAYA SERGEY BLAGODATSKY MAXIM DORODNIKOV YAKOV KUZYAKOV 《Global Change Biology》2010,16(2):836-848
Increasing the belowground translocation of assimilated carbon by plants grown under elevated CO2 can cause a shift in the structure and activity of the microbial community responsible for the turnover of organic matter in soil. We investigated the long‐term effect of elevated CO2 in the atmosphere on microbial biomass and specific growth rates in root‐free and rhizosphere soil. The experiments were conducted under two free air carbon dioxide enrichment (FACE) systems: in Hohenheim and Braunschweig, as well as in the intensively managed forest mesocosm of the Biosphere 2 Laboratory (B2L) in Oracle, AZ. Specific microbial growth rates (μ) were determined using the substrate‐induced respiration response after glucose and/or yeast extract addition to the soil. For B2L and both FACE systems, up to 58% higher μ were observed under elevated vs. ambient CO2, depending on site, plant species and N fertilization. The μ‐values increased linearly with atmospheric CO2 concentration at all three sites. The effect of elevated CO2 on rhizosphere microorganisms was plant dependent and increased for: Brassica napus=Triticum aestivum<Beta vulgaris<Populus deltoides. N deficiency affected microbial growth rates directly (N limitation) and indirectly (changing the quantity of fine roots). So, 50% decrease in N fertilization caused the overall increase or decrease of microbial growth rates depending on plant species. The μ‐value increase was lower for microorganisms growing on yeast extract then for those growing on glucose, i.e. the effect of elevated CO2 was smoothed on rich vs. simple substrate. So, the r/K strategies ratio can be better revealed by studying growth on simple (glucose) than on rich substrate mixtures (yeast extract). Our results clearly showed that the functional characteristics of the soil microbial community (i.e. specific growth rates) rather than total microbial biomass amount are sensitive to increased atmospheric CO2. We conclude that the more abundant available organics released by roots at elevated CO2 altered the ecological strategy of the soil microbial community specifically a shift to a higher contribution of fast‐growing r‐selected species was observed. These changes in functional structure of the soil microbial community may counterbalance higher C input into the soil under elevated atmospheric CO2 concentration. 相似文献
14.
BRUCE A. HUNGATE CHRISTOPHER P. LUND HOLLY L. PEARSON F. STUART CHAPIN III 《Biogeochemistry》1997,37(2):89-109
We examined the effects of growth carbon dioxide (CO2)concentration and soil nutrient availability on nitrogen (N)transformations and N trace gas fluxes in California grasslandmicrocosms during early-season wet-up, a time when rates of Ntransformation and N trace gas flux are high. After plant senescenceand summer drought, we simulated the first fall rains and examined Ncycling. Growth at elevated CO2 increased root productionand root carbon:nitrogen ratio. Under nutrient enrichment, elevatedCO2 increased microbial N immobilization during wet-up,leading to a 43% reduction in gross nitrification anda 55% reduction in NO emission from soil. ElevatedCO2 increased microbial N immobilization at ambientnutrients, but did not alter nitrification or NO emission. ElevatedCO2 did not alter soil emission of N2O ateither nutrient level. Addition of NPK fertilizer (1:1:1) stimulatedN mineralization and nitrification, leading to increased N2Oand NO emission from soil. The results of our study support a mechanisticmodel in which elevated CO2 alters soil N cycling and NOemission: increased root production and increased C:N ratio in elevatedCO2 stimulate N immobilization, thereby decreasingnitrification and associated NO emission when nutrients are abundant.This model is consistent with our basic understanding of how C availabilityinfluences soil N cycling and thus may apply to many terrestrial ecosystems. 相似文献
15.
Carbon dynamics and microbial activity in tallgrass prairie exposed to elevated CO2 for 8 years 总被引:19,自引:0,他引:19
Alterations in microbial mineralization and nutrient cycling may control the long-term response of ecosystems to elevated
CO2. Because micro-organisms constitute a labile fraction of potentially available N and are regulators of decomposition, an
understanding of microbial activity and microbial biomass is crucial. Tallgrass prairie was exposed to twice ambient CO2 for 8 years beginning in 1989. Starting in 1991 and ending in 1996, soil samples from 0 to 5 and 5 to 15 cm depths were taken
for measurement of microbial biomass C and N, total C and N, microbial activity, inorganic N and soil water content. Because
of increased water-use-efficiency by plants, soil water content was consistently and significantly greater in elevated CO2 compared to ambient treatments. Soil microbial biomass C and N tended to be greater under elevated CO2 than ambient CO2 in the 5–15 cm depth during most years, and in the month of October, when analyzed over the entire study period. Microbial
activity was significantly greater at both depths in elevated CO2 than ambient conditions for most years. During dry periods, the greater water content of the surface 5 cm soil in the elevated
CO2 treatments increased microbial activity relative to the ambient CO2 conditions. The increase in microbial activity under elevated CO2 in the 5–15 cm layer was not correlated with differences in soil water contents, but may have been related to increases in
soil C inputs from enhanced root growth and possibly greater root exudation. Total soil C and N in the surface 15 cm were,
after 8 years, significantly greater under elevated CO2 than ambient CO2. Our results suggest that decomposition is enhanced under elevated CO2 compared with ambient CO2, but that inputs of C are greater than the decomposition rates. Soil C sequestration in tallgrass prairie and other drought-prone
grassland systems is, therefore, considered plausible as atmospheric CO2 increases.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
Louise C. Andresen Jennifer A. J. Dungait Roland Bol Merete B. Selsted Per Ambus Anders Michelsen 《PloS one》2014,9(1)
It is vital to understand responses of soil microorganisms to predicted climate changes, as these directly control soil carbon (C) dynamics. The rate of turnover of soil organic carbon is mediated by soil microorganisms whose activity may be affected by climate change. After one year of multifactorial climate change treatments, at an undisturbed temperate heathland, soil microbial community dynamics were investigated by injection of a very small concentration (5.12 µg C g−1 soil) of 13C-labeled glycine (13C2, 99 atom %) to soils in situ. Plots were treated with elevated temperature (+1°C, T), summer drought (D) and elevated atmospheric carbon dioxide (510 ppm [CO2]), as well as combined treatments (TD, TCO2, DCO2 and TDCO2). The 13C enrichment of respired CO2 and of phospholipid fatty acids (PLFAs) was determined after 24 h. 13C-glycine incorporation into the biomarker PLFAs for specific microbial groups (Gram positive bacteria, Gram negative bacteria, actinobacteria and fungi) was quantified using gas chromatography-combustion-stable isotope ratio mass spectrometry (GC-C-IRMS).Gram positive bacteria opportunistically utilized the freshly added glycine substrate, i.e. incorporated 13C in all treatments, whereas fungi had minor or no glycine derived 13C-enrichment, hence slowly reacting to a new substrate. The effects of elevated CO2 did suggest increased direct incorporation of glycine in microbial biomass, in particular in G+ bacteria, in an ecosystem subjected to elevated CO2. Warming decreased the concentration of PLFAs in general. The FACE CO2 was 13C-depleted (δ13C = 12.2‰) compared to ambient (δ13C = ∼−8‰), and this enabled observation of the integrated longer term responses of soil microorganisms to the FACE over one year. All together, the bacterial (and not fungal) utilization of glycine indicates substrate preference and resource partitioning in the microbial community, and therefore suggests a diversified response pattern to future changes in substrate availability and climatic factors. 相似文献
17.
Taiji Kou Jianguo Zhu Zubin Xie Toshihiro Hasegawa Katia Heiduk 《Plant and Soil》2007,299(1-2):237-249
Soil respiration in a cropland is the sum of heterotrophic (mainly microorganisms) and autotrophic (root) respiration. The
contribution of both these types to soil respiration needs to be understood to evaluate the effects of environmental change
on soil carbon cycling and sequestration. In this paper, the effects of free-air CO2 enrichment (FACE) on hetero- and autotrophic respiration in a wheat field were differentiated and evaluated by a novel split-root
growth and gas collection system. Elevated atmospheric pCO2 of approximately 200 μmol mol−1 above the ambient pCO2 significantly increased soil respiration by 15.1 and 14.8% at high nitrogen (HN) and low nitrogen (LN) application rates,
respectively. The effect of elevated atmospheric pCO2 on root respiration was not consistent across the wheat growth stages. Elevated pCO2 significantly increased and decreased root respiration at the booting-heading stage (middle stage) and the late-filling stage
(late stage), respectively, in HN and LN treatments; however, no significant effect was found at the jointing stage (early
stage). Thus, the effect of increased pCO2 on cumulative root respiration for the entire wheat growing season was not significant. Cumulative root respiration accounted
for approximately 25–30% of cumulative soil respiration in the entire wheat growing season. Consequently, cumulative microbial
respiration (soil respiration minus root respiration) increased by 22.5 and 21.1% due to elevated pCO2 in HN and LN, respectively. High nitrogen application significantly increased root respiration at the late stage under both
elevated pCO2 and ambient pCO2; however, no significant effects were found on cumulative soil respiration, root respiration, and microbial respiration.
These findings suggest that heterotrophic respiration, which is influenced by increased substrate supplies from the plant
to the soil, is the key process to determine C emission from agro-ecosystems with regard to future scenarios of enriched pCO2. 相似文献
18.
青藏高原高寒草甸土壤CO2排放对模拟氮沉降的早期响应 总被引:5,自引:0,他引:5
研究大气氮沉降输入对青藏高原高寒草甸土壤-大气界面CO2交换通量的影响,对于准确评价全球变化背景下区域碳平衡至关重要。通过构建多形态、低剂量的增氮控制试验,利用静态箱-气相色谱法测定土壤CO2排放通量,同时测定相关土壤变量和地上生物量,分析高寒草甸土壤CO2排放特征及其主要驱动因子。研究结果表明:低、高剂量氮输入倾向于消耗土壤水分,而中剂量氮输入有利于土壤水分的保持;施氮初期总体上增加了土壤无机氮含量,铵态氮累积效应更为显著;施氮显著增加地上生物量和土壤CO2排放通量,铵态氮的促进效应显著高于硝态氮。另外,土壤CO2排放通量主要受土壤温度驱动,其次为地上生物量和铵态氮储量。上述结果反映了氮沉降输入短期内可能刺激了植物生长和土壤微生物活性,加剧了土壤-大气界面CO2排放。 相似文献
19.
Microbial biomass and activity were determined in cambisol incubated under ambient and increased (up to 2.23 mmol/L) CO2 concentrations. An immediate negative response of the soil microbial community to [CO]2 increase was observed during the first day with respect to microbial biomass, soil respiration and specific respiration activity
(both expressed as CO2 evolution). In contrast, O2 consumption was not affected but anabolic utilization of available substrate increased. These phenomena were observed under
conditions of increased CO2 tension but without any change in O2 concentration. 相似文献
20.
This study examines the effect of elevated CO2 on short-term partitioning of inorganic N between a grass and soil micro-organisms. 15N-labelled NH4+ was injected in the soil of mesocosms of Holcus lanatus (L.) that had been grown for more than 15 months at ambient or elevated CO2 in reconstituted grassland soil. After 48 h, the percentage recovery of added 15N was increased in soil microbial biomass N at elevated CO2, was unchanged in total plant N and was decreased in soil extractable N. However, plant N content and microbial biomass N
were not significantly affected by elevated CO2. These results and literature data from plant–microbial 15N partitioning experiments at elevated CO2 suggest that the mechanisms controlling the effects of CO2 on short- vs. long-term N uptake and turnover differ. In particular, short-term immobilisation of added N by soil micro-organisms
at elevated CO2 does not appear to lead to long-term increases in N in soil microbial biomass. In addition, the increased soil microbial
C:N ratios that we observed at elevated CO2 suggest that long-term exposure to CO2 alters either the functioning or structure of these microbial communities. 相似文献