Short-term CO2 emissions from planted soil subject to elevated CO2 and simulated precipitation     

《Applied soil ecology》2005,28(3):247-257

Carbon dioxide emissions from soils beneath canopies of two Mediterranean plants, Artemisia absinthium L. and Festuca pratensis Huds. cv. Demeter, were monitored over a 7-day period that included an artificial precipitation event of 4 cm. The experiments were conducted using 0.2 m³ soil microcosms inside greenhouses with CO₂ concentrations of either 360 or 500 μmol mol⁻¹. Carbon dioxide flux from the soil surface, as calculated using a diffusive transport model agreed well with CO₂ flux measurements made using a dynamic flow system. Soil CO₂ emissions did not differ significantly between the 360 and 500 μmol mol⁻¹ CO₂ treatments when soils were dry (volumetric soil moisture content ≤9%). A simulated precipitation event caused an immediate exhalation of CO₂ from soil, after which CO₂ emissions declined slightly and remained constant for approximately 36 h. CO₂ emissions from soil microcosms with F. pratensis plants growing in 500 μmol mol⁻¹ CO₂ then rose to levels that were significantly greater than CO₂ emissions from soils in the microcosms exposed to 360 μmol mol⁻¹ CO₂. For A. absinthium growing in 500 μmol mol⁻¹ CO₂, the rise in soil CO₂ emissions following the wetting event was not significantly greater than emissions from soils with A. absinthium growing under 360 μmol mol⁻¹ CO₂. A. absinthium above ground biomass increased by 46.1 ± 17.9% (mean ± S.E., n = 4, P ≤ 0.05). Above ground biomass did not significantly increase for F. pratensis (14.4 ± 6.5%, P ≥ 0.10). Root biomass, on the other hand, increased for both species; by 50.6 ± 17.9% (P ≤ 0.05) for A. absinthium and by 55.9 ± 12.7% (P ≤ 0.05) for F. pratensis. Our results demonstrate two events following precipitation onto dry soils, an immediate release of CO₂ followed by a gradual increase from enhanced biological activity The gradual increase was greater for the herbaceous ruderal perennial F. pratensis under elevated CO₂.  相似文献   

Seasonality of soil biological properties in a poplar plantation growing under elevated atmospheric CO2     

《Applied soil ecology》2006,31(3):162-173

Microorganisms are the regulators of decomposition processes occurring in soil, they also constitute a labile fraction of potentially available N. Microbial mineralization and nutrient cycling could be affected through altered plant inputs at elevated CO_2. An understanding of microbial biomass and microbial activity in response to belowground processes induced by elevated CO₂ is thus crucial in order to predict the long-term response of ecosystems to climatic changes. Microbial biomass, microbial respiration, inorganic N, extractable P and six enzymatic activities related to C, N, P and S cycling (β-glucosidase, cellulase, chitinase, protease, acid phosphatase and arylsulphatase) were investigated in soils of a poplar plantation exposed to elevated CO_2. Clones of Populus alba, Populus nigra and Populus x euramericana were grown in six 314 m² plots treated either with atmospheric (control) or enriched (550 μmol mol⁻¹ CO₂) CO₂ concentration with FACE technology (free-air CO₂ enrichment). Chemical and biochemical parameters were monitored throughout a year in soil samples collected at five sampling dates starting from Autumn 2000 to Autumn 2001.The aim of the present work was: (1) to determine if CO₂ enrichment induces modifications to soil microbial pool size and metabolism, (2) to test how the seasonal fluctuations of soil biochemical properties and CO₂ level interact, (3) to evaluate if microbial nutrient acquisition activity is changed under elevated CO₂.CO₂ enrichment significantly affected soil nutrient content and three enzyme activities: acid phosphatase, chitinase and arylsulphatase, indicators of nutrient acquisition activity. Microbial biomass increased by a 16% under elevated CO₂. All soil biochemical properties were significantly affected by the temporal variability and the interaction between time and CO₂ level significantly influenced β-glucosidase activity and microbial respiration. Data on arylsulphatase and chitinase activity suggest a possible shift of microbial population in favour of fungi induced by the FACE treatment.  相似文献   

Response of soil microbial biomass and enzyme activities to the transient elevation of carbon dioxide in a semi-arid grassland   总被引：1，自引：0，他引：1  

Ellen Kandeler  Arvin R. Mosier  Daniel G. Milchunas  Sabine Rudolph 《Soil biology & biochemistry》2006,38(8):2448-2460

Although elevation of CO₂ has been reported to impact soil microbial functions, little information is available on the spatial and temporal variation of this effect. The objective of this study was to determine the microbial response in a northern Colorado shortgrass steppe to a 5-year elevation of atmospheric CO₂ as well as the reversibility of the microbial response during a period of several months after shutting off the CO₂ amendment. The experiment was comprised of nine experimental plots: three chambered plots maintained at ambient CO₂ levels of 360 μmol mol⁻¹ (ambient treatment), three chambered plots maintained at 720 μmol mol⁻¹ CO₂ (elevated treatment) and three unchambered plots of equal ground area used as controls to monitor the chamber effect.Elevated CO₂ induced mainly an increase of enzyme activities (protease, xylanase, invertase, alkaline phosphatase, arylsulfatase) in the upper 5 cm of the soil and did not change microbial biomass in the soil profile. Since rhizodeposition and newly formed roots enlarged the pool of easily available substrates mainly in the upper soil layers, enzyme regulation (production and activity) rather than shifts in microbial abundance was the driving factor for higher enzyme activities in the upper soil. Repeated soil sampling during the third to fifth year of the experiment revealed an enhancement of enzyme activities which varied in the range of 20-80%. Discriminant analysis including all microbiological properties revealed that the enzyme pattern in 1999 and 2000 was dominated by the CO₂ and chamber effect, while in 2001 the influence of elevated CO₂ increased and the chamber effect decreased.Although microbial biomass did not show any response to elevated CO₂ during the main experiment, a significant increase of soil microbial N was detected as a post-treatment effect probably due to lower nutrient (nitrogen) competition between microorganisms and plants in this N-limited ecosystem. Whereas most enzyme activities showed a significant post-CO₂ effect in spring 2002 (following the conclusion of CO₂ enrichment the previous autumn, 2001), selective depletion of substrates is speculated to be the cause for non-significant treatment effects of most enzyme activities later in summer and autumn, 2002. Therefore, additional belowground carbon input mainly entered the fast cycling carbon pool and contributed little to long-term carbon storage in the semi-arid grassland.  相似文献   

Decomposition kinetics of soil carbon of different age from a forest exposed to 8 years of elevated atmospheric CO2 concentration     

Lina Taneva  Miquel A. Gonzalez-Meler 《Soil biology & biochemistry》2008,40(10):2670-2677

Ecosystem exposure to elevated atmospheric CO₂ concentration can often leads to increased ecosystem carbon (C) fluxes, as well as greater net primary production. Changes in the soil C pool with elevated [CO₂] are more difficult to measure and therefore remain poorly understood. In this study, we carried out a series of laboratory soil incubations, in order to determine whether 8 years of ecosystem exposure to elevated [CO₂] altered decomposition dynamics of two age classes of soil C in a temperate coniferous forest. Our objectives were to determine whether there were differences in the decomposition kinetics of soil C up to 8 years old (C_post-tr) and soil C older than 8 years (C_pre-tr), in the absence of concurrent plant activity. We collected soil from the Duke Forest Free Air CO₂ Enrichment site in North Carolina and incubated whole and crushed (all macroaggregates dispersed) soil from two depth increments (0–5 cm and 5–15 cm) for 102–127 days. We found that mineral soil from the treatment plots had higher respiration rates in the absence of concurrent plant activity than mineral soil from plots under ambient CO₂ conditions. These differences in respiration rate were only significant in 0–5 cm soil and could be largely explained by higher initial respiration rates of soil collected from the CO₂-treated plots. Disruption of soil macroaggregates did not result in a difference in efflux rate in soil from this forest under ambient or elevated CO₂ conditions at either depth. The specific respiration rate of C_post-tr was higher than that of C_pre-tr in the top 5 cm of soil, while the opposite was true for 5–15 cm of soil. Even though C_post-tr was assimilated by the ecosystem more recently than C_pre-tr, their decay constants were similar at both depths. These results suggest that, in the absence of plant activity, the mineralization of soil C of different ages in this forest may be under similar biological and/or biochemical control. Therefore, if the higher initial rates of decomposition of C_post-tr seen in these experiments are sustained in the field, greater labile pool size of recently added C, and potentially faster cycling of this pool, may in part explain higher soil respiration rates and limited soil C accumulation under elevated [CO₂] in this forest.  相似文献   

Interactions between plant species and mycorrhizal colonization on the bacterial community composition in the rhizosphere     

《Applied soil ecology》2005,28(1):23-36

This study assessed the effect of mycorrhizal colonization by Glomus intraradices (Gi) and G. versiforme (Gv) on the bacterial community composition in the rhizosphere of canola, clover and two tomato genotypes (wild type (76R) and its mutant with reduced mycorrhizal colonization (rmc)). Additionally, the effect of light intensity on the rhizosphere bacterial community composition of the tomato genotypes was studied. The bacterial community composition was assessed by denaturing gradient gel electrophoresis (DGGE). In canola, which is considered to be a non-mycorrhizal species, inoculation with Gi increased the shoot dw compared to Gv and the non-mycorrhizal control plants and also induced changes in the bacterial community composition in the rhizosphere. These fungal effects were observed although less than 8% of the root length of canola was colonized. On the other hand, about 50% of the root length of clover was colonized and inoculation with Gv resulted in a higher shoot dw compared to Gi or the control plants but the rhizosphere bacterial community composition was not affected by inoculation. Plant growth, mycorrhizal colonization and bacterial community composition of the two tomato genotypes were affected by a complex interaction between tomato genotype, AM fungal species and light intensity. Low light intensity (photosynthetic photon flux 200–250 μmol m⁻² s⁻¹) increased the shoot–root ratio in both genotypes and reduced colonization in the wild type. The differences in bacterial community composition between the two genotypes were more pronounced at low than at high light intensity (550–650 μmol m⁻² s⁻¹).  相似文献   

Effect of elevated atmospheric CO2 and temperature on disease severity of Fusarium oxysporum f.sp. lactucae on lettuce plants     

《Applied soil ecology》2013

Climate change effects on Fusarium oxysporum f.sp. lactucae (FOL) on lettuce plants grown under simulated climate change were studied. An artificial growing substrate was infested with FOL to reach a final concentration of 1 × 10⁴ CFU g⁻¹ of substrate. A non infested tank was used as control.Subsequently, 32 pots (2 l each) were prepared from the infested tank and other 32 pots were prepared from the non infested tank (control). Lettuce plants were then transplanted into the pots and grown in phytotrons under four simulated environmental conditions: (1) 800 ppm CO₂, 22–26 °C; (2) 800 ppm CO₂, 18–22 °C; (3) 400 ppm CO₂, 22–26 °C and (4) 400 ppm CO₂, 18–22 °C. Substrate samples were collected from each phytotron at 7, 14, 21 and 28 days after transplanting. Plate counts, enzymatic assays, and polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analyses were performed to evaluate the effect of climate change on the microbial population. The abundance of Fusarium spp. and the severity of Fusarium wilt of lettuce varied significantly as a consequence of increased temperature (22–26 °C). Increased CO₂ levels showed no effect on the severity of Fusarium wilt of lettuce and on the abundance of Fusarium spp. On the other hand, the total bacterial abundance was reduced at elevated CO₂ concentration (800 ppm). PCR-DGGE fingerprints of the ascomycete community obtained from DNA directly extracted from infested substrate samples did not change as a consequence of elevated temperature and CO₂.Enzymatic activities were not affected by the elevated CO₂ level. Our study indicates that the CO₂ concentration used in our experiment had no detectable impact on Fusarium wilt of lettuce. Only temperature influenced all observed parameters, but did not affect the fungal species diversity. Other factors, such as nutrient limitation and the effect of plant species needs further study.  相似文献   

Effects of elevated atmospheric CO2 and N fertilization on abundance,diversity and C-isotopic signature of collembolan communities in arable soil     

《Applied soil ecology》2007,35(2-3):219-229

Rising atmospheric CO₂ concentrations are expected to have marked impacts on the carbon (C) turnover in agro-ecosystems through increased plant photosynthetic rates, leading to an enhanced biomass, and wider plant C/N ratios. Through increased carbon allocation below-ground, as well as through changed litter quality, CO₂ enrichment will indirectly affect soil faunal communities. In the present study we investigated how elevated atmospheric CO₂ and two different levels of N fertilization may affect abundance and diversity of collembolans, as important catalysts in decomposition processes, within an agro-ecosystem under winter wheat cultivation. The investigations were carried out in 2002 within a field experiment using the “Free Air CO₂ Enrichment” technique (FACE) at the Federal Agricultural Research Centre (Braunschweig, Germany). Stable C-isotopic analysis of collembolans, soil, and crops gave insight into C translocation. During our investigations δ¹³C values of all components analysed were significantly more negative under FACE compared to ambient air conditions. Stable C-isotopic signatures of collembolans were similar to those of soil under ambient air, but in between those of soil and roots under elevated CO₂ conditions. Our results revealed significant effects of both treatments (CO₂ enrichment and N fertilization) on density and species diversity of collembolans. Overall, collembolans were stimulated under elevated CO₂ conditions, showing an increased abundance of more than 50% (11 240 ind m⁻²) as well as a higher biodiversity (Shannon Weaver index = 2.5; evenness = 0.75) compared to ambient air conditions (7520 ind m⁻²; Shannon Weaver index = 2.2; evenness = 0.72). With regard to N supply, a decrease of about 20–30% under CO₂ enrichment and 45–55% under ambient air conditions in collembolan abundance with no alteration in diversity was recorded under reduced N fertilization. The observed impacts were species-specific.  相似文献   

Bacterial community structure and microbial activity in different soils amended with biogas residues and cattle slurry     

《Applied soil ecology》2013

Anaerobic digestion of organic materials generates residues of differing chemical composition compared to undigested animal manures, which may affect the soil microbial ecosystem differently when used as fertilizers. This study investigated the effects of two biogas residues (BR-A and BR-B) and cattle slurry (CS) applied at rates corresponding to 70 kg NH₄⁺-N ha⁻¹ on bacterial community structure and microbial activity in three soils of different texture (a sandy, a clay and an organic clay soil). 16S rRNA genes were targeted in PCR reactions and bacterial community profiles visualized using terminal restriction fragment length polymorphism. General microbial activity was measured as basal respiration (B-resp), substrate-induced respiration (SIR), specific growth rate (μ_SIR), metabolic quotient (qCO₂) and nitrogen mineralization capacity (NMC). Non-metric multidimensional scaling analysis visualized shifts in bacterial community structure related to microbial functions. There were significant differences in bacterial community structure after 120 days of incubation (+20 °C at 70% of WHC) between non-amended (control) and amended soils, especially in the sandy soil, where CS caused a more pronounced shift than biogas residues. Terminal-restriction fragment (TRF) 307, the predominant peak in CS-amended sandy soil, was identified as possibly Bacillus or Streptococcus. TRF 226, the dominant peak in organic soil amended with BR-B, was classified as Rhodopseudomonas. B-resp significantly increased and SIR decreased in all amendments to organic soil compared with the control, potentially indicating decreased efficiency of heterotrophic microorganisms to convert organic carbon into microbial biomass. This was also reflected in an elevated qCO₂ in the organic soil. The μ_SIR level was higher in the sandy soil amended with BR-A than with BR-B or CS, indicating a shift toward species capable of rapidly utilizing glucose. NMC was significantly elevated in the clay and organic soils amended with BR-A and BR-B and in the sandy soil amended with BR-B and CS. Thus, biogas residues and cattle slurry had different effects on the bacterial community structure and microbial activity in the three soils. However, the effects of biogas residues on microbial activities were comparable in magnitude to those of cattle slurry and the bacterial community structure was less affected. Therefore, we do not see any reason not to recommend using biogas residues as fertilizers based on the results presented.  相似文献   

Chronic nitrogen deposition and the composition of active arbuscular mycorrhizal fungi     

《Applied soil ecology》2013

A growing body of evidence indicates that atmospheric nitrogen (N) deposition can alter the composition and function of arbuscular mycorrhizal fungi (AMF) associated with plant roots. We studied the community of AMF actively transcribing ribosomal genes in the forest floor of northern hardwood forests dominated by sugar maple (Acer saccharum Marsh.) that have been exposed to experimental N deposition since 1994 (30 kg NO₃⁻-N ha⁻¹ year⁻¹). Our objective was to evaluate whether previously observed declines in AM root infection and mycelial production resulted in a compositional shift in the AM fungi actively providing resources to plant symbionts under chronic N deposition. To accomplish this task, we cloned and sequenced the LSU of reverse-transcribed AM fungal rRNA extracted from the forest floor under ambient and experimental N deposition treatments. We found that experimental N deposition did not alter the active community of AMF or AMF diversity, but we did observe a significant decrease in rare taxa under chronic N deposition. Our results indicate that chronic N deposition, at levels expected by the end of this century, can exert a moderate influence on the composition and abundance of AMF associated with plant roots in a wide-spread forest ecosystem in the northeastern North America.  相似文献   

Switch of tropical Amazon forest to pasture affects taxonomic composition but not species abundance and diversity of arbuscular mycorrhizal fungal community     

《Applied soil ecology》2013

Arbuscular mycorrhizal fungi (AMF) community composition and species richness are affected by several factors including soil attributes and plant host. In this paper we tested the hypothesis that conversion of tropical Amazon forest to pasture changes taxonomic composition of AMF community but not community species abundance and richness. Soil samples were obtained in 300 m × 300 m plots from forest (n = 11) and pasture (n = 13) and fungal spores extracted, counted and identified. A total of 36 species were recovered from both systems, with 83% of them pertaining to Acaulosporaceae and Glomeraceae. Only 12 species were shared between systems and spore abundance of the majority of fungal species did not differ between pasture and forest. Spore abundance was significantly higher in pasture compared to forest but both systems did not differ on mean species richness, Shannon diversity and Pielou equitability. Species abundance distribution depicted by species rank log abundance plots was not statistically different between both systems. We concluded that conversion of pristine tropical forest to pasture influences the taxonomic composition of AMF communities while not affecting species richness and abundance distribution.  相似文献   

Responses of canopy and soil climate in a six year free-air CO2 enrichment study with spring crops     

J. Franzaring  P. Högy  M. Erbs  A. Fangmeier 《Agricultural and Forest Meteorology》2010,150(3):354-360

Besides increased growth, plants cultivated under elevated carbon dioxide (CO₂) show reduced transpiration and improved water use efficiency due to decreased stomatal conductances. While growth profits from the longer availability of soil water under CO₂ enrichment, increased canopy temperature may counteract these positive effects. Here we report on time series of soil temperatures and moistures from six years in which spring crops were cultivated in free-air CO₂ enrichment (Mini-FACE) experiments. Besides air and soil climate, temperature and relative humidity were determined in wheat canopies. Measurements rested on five replicates per treatment, representing a control (CON), an ambient air (AMB) and a FACE treatment. While the CON and AMB plots did not receive additional CO₂, concentrations were moderately elevated by 150 μl l^?1 in the FACE plots. Plant growth differed among years due to the different climate and duration of individual experiments. Total biomass production was increased in the FACE treatments but significant effects were found only in one out of six years. In most of the years, soil temperatures tended to be reduced and soil moistures remained higher under elevated CO₂. Because the observed differences recurred during the growing season, we conclude that CO₂ enrichment was responsible for changes of the soil microclimate. At the same time vapour pressure deficit in the canopy significantly differed between the treatments for some days. While canopy heating due to CO₂ enrichment occurred in the early growing season these effects disappeared later suggesting that the stronger increase in leaf area index in the FACE treatments mitigated heating effects over time. The results support the supposed effects of CO₂ enrichment on the canopy climate and indicate a ‘microclimatic paradox’ with higher soil water availability due to the reduced transpiration and stronger canopy heating in FACE plots at least early in the season.  相似文献   

Partitioning soil surface CO2 efflux into autotrophic and heterotrophic components,using natural gradients in soil δ13C in an undisturbed savannah soil     

Peter Millard  Andrew J. Midwood  John E. Hunt  David Whitehead  Thomas W. Boutton 《Soil biology & biochemistry》2008,40(7):1575-1582

We used natural gradients in soil and vegetation δ¹³C signatures in a savannah ecosystem in Texas to partition soil respiration into the autotrophic (Ra) and heterotrophic (Rh) components. We measured soil respiration along short transects from under clusters of C₃ trees into the C₄ dominated grassland. The site chosen for the study was experiencing a prolonged drought, so an irrigation treatment was applied at two positions of each transect. Soil surface CO₂ efflux was measured along transects and CO₂ collected for analysis of the δ¹³C signature in order to: (i) determine how soil respiration rates varied along transects and were affected by localised change in soil moisture and (ii) partition the soil surface CO₂ efflux into Ra and Rh, which required measurement of the δ¹³C signature of root- and soil-derived CO₂ for use in a mass balance model.The soil at the site was unusually dry, with mean volumetric soil water content of 8.2%. Soil respiration rates were fastest in the centre of the tree cluster (1.5 ± 0.18 μmol m^?2 s^?1; mean ± SE) and slowest at the cluster–grassland transition (0.6 ± 0.12 μmol m^?2 s^?1). Irrigation produced a 7–11 fold increase in the soil respiration rate. There were no significant differences (p > 0.5) between the δ¹³C signature of root biomass and respired CO₂, but differences (p < 0.01) were observed between the respired CO₂ and soil when sampled at the edge of the clusters and in the grassland. Therefore, end member values were measured by root and soil incubations, with times kept constant at 30 min for roots and 2 h for soils. The δ¹³C signature of the soil surface CO₂ efflux and the two end member values were used to calculate that, in the irrigated soils, Rh comprised 51 ± 13.5% of the soil surface CO₂ efflux at the mid canopy position and 57 ± 7.4% at the drip line. In non-irrigated soil it was not possible to partition soil respiration, because the δ¹³C signature of the soil surface CO₂ efflux was enriched compared to both the end member values. This was probably due to a combination of the very dry porous soils at our study site (which may have been particularly susceptible to ingress of atmospheric CO₂) and the very slow respiration rates of the non-irrigated soils.  相似文献   

Chemical and microbiological soil quality indicators and their potential to differentiate fertilization regimes in temperate agroecosystems     

《Applied soil ecology》2013

The study examined the interrelationships between chemical and microbiological quality indicators of soil and their ability to differentiate plots under contrasting fertilization regimes. The study was based on a long-term field experiment established on an Udic Ustocrepts in 1966. The soil was cropped with maize (Zea mays L.) and winter wheat (Triticum aestivum L.) and received no organic fertilization (control), wheat straw and maize stalk (crop residue) or cattle manure (manure) in combination with increasing levels of mineral N (N₀ and N₂₀₀). To asses whether seasonal fluctuations of measured properties might mask the effects of fertilization, soil samples were collected four times within a growing season. Manure amendment increased soil TOC and TN, while crop residue amendment had no significant effects. Mineral N increased TN only in April, while in September it decreased water extractable organic C (WEOC). Data of diffuse reflectance Fourier transform mid-infrared spectroscopy (DRIFTS) gave evidence for a higher relative contribution of the aliphatic peak at 2930 cm⁻¹ and a lower relative contribution of the aromatic peaks at 1620 cm⁻¹ and 1520 cm⁻¹ under manure. Manure amendment stimulated enzymatic activities, increased microbial biomass carbon (C_mic) and total phospholipids (PLFAs), and reduced the metabolic quotient (qCO₂). Patterns of PLFAs indicated that manure amendment increased the ratio of Gram-positive to Gram-negative bacteria. Crop residue amendment had no significant effects, while in September mineral N inhibited protease activity and reduced the Gram-positive to Gram-negative ratio. Microbial-related parameters fluctuated over time but their seasonality did not hamper the identification of fertilization-induced effects. The selected properties proved to be valuable indicators of long-term changes of soil quality and were strongly interrelated: changes in soil organic matter content and composition induced by manure amendment were accompanied by changes in abundance and function of the soil microbial community. Partial least square analysis obtained relating DRIFTS spectra to measured soil properties produced accurate predictive models for TOC and PLFAs, and moderately accurate models for C_mic, showing the potential of DRIFTS to be used as a rapid soil testing technique for soil quality monitoring.  相似文献   

Methanotrophic communities in a landfill cover soil as revealed by [13C] PLFAs and respiratory quinones: Impact of high methane addition and landfill leachate irrigation     

Andrea Watzinger  Michael Stemmer  Michael Pfeffer  Frank Rasche  Thomas G. Reichenauer 《Soil biology & biochemistry》2008,40(3):751-762

The soil microbial communities of a landfill cover substrate, which was treated with landfill gas (100 l CH₄ m^?2 d^?1) and landfill leachate for 1.5 years, were investigated by phospholipid fatty acid (PLFA), ergosterol and respiratory quinone analyses. The natural ¹³C depletion of methane was used to assess the activity of methanotrophs and carbon turnover in the soil system. Under methane addition, the soil microbial community was dominated by PLFAs (14:0 and 16:1 isomers) and quinones (ubiquinone-8 and 18-methylene-ubiquinone-8) related to type I methanotrophs, and 18:1 PLFAs contained in type II methanotrophs. While type I methanotrophic PLFAs were ¹³C depleted, i.e. type I methanotrophs were actively oxidising and assimilating methane, ¹³C depletion of 18:1 PLFAs was low and inconsistent with their abundance. This, possibly reflects isotopic discrimination, assimilation of carbon derived from type I methanotrophs and a high contribution of non-methanotrophic bacteria to the 18:1 isomers. Landfill leachate irrigation caused the methanotrophic community to shift closer to the soil surface. It also decreased 18:1 PLFAs, while type I methanotrophs were probably stimulated. Gram positive bacteria, but not fungi, were also ¹³C depleted and consequently involved in the secondary turnover of carbon originating from methanotrophic bacteria. Cy17:0 PLFA was ¹³C depleted in deep soil layers, indicating anaerobic methane oxidation.  相似文献   

Deciduous woodland exposed to elevated atmospheric CO2 has species-specific impacts on anecic earthworms     

《Applied soil ecology》2014

Elevated atmospheric CO₂ induced reductions in litter quality can adversely affect earthworms. However, this understanding is based on laboratory rather than field research and relates to single earthworm and tree species. Here earthworm populations were investigated under Alnus glutinosa, Betula pendula, and Fagus sylvatica in a Free Air Carbon dioxide Enrichment field experiment. Litters from this experiment were also fed to Lumbricus terrestris L. at two rates with live weight change and cast properties assessed. Elevated CO₂ (580 ppmv) reduced litter N (−12%) with a corresponding increase in C:N ratio, especially for A. glutinosa. In the field, elevated CO₂ caused a shift in overall population composition, mainly characterised by reduced anecic biomass (–25%); endogeic and epigeic species were less affected. CO₂ effects on total biomass were most pronounced for A. glutinosa (e.g. field total biomass −47% vs. −11% overall). Growth of L. terrestris was lower when fed elevated CO₂ litter (−18%), although increased inputs of A. glutinosa litter mitigated this effect. In mesocosms, fresh cast respiration was lower (−14%) for elevated CO₂ litter, an effect more pronounced for A. glutinosa (−24%). When normalised for C content, elevated CO₂ effects on cast respiration were again negative and most marked for A. glutinosa litter. Litter N concentration, and possibly ease of litter mineralisation were factors affecting litter resource quality Litter N and P concentrations varied with A. glutinosa > B. pendula > F. sylvatica; F. sylvatica had the highest cellulose content. Field earthworm biomass was higher under A. glutinosa compared with B. pendula and F. sylvatica (+17 and +70%, respectively); live weight increased with A. glutinosa litter in the feeding trial almost three times more than for B. pendula, whereas it decreased for F. sylvatica. Cast respiration was highest for A. glutinosa, intermediate for B. pendula (ca. −36%) and lowest for F. sylvatica (ca. −78%). Earthworm responses to elevated CO₂ were complex, being characteristic of individual tree and earthworm species; responses were more adverse for trees with higher quality litter and for anecic earthworms.  相似文献   

Land use influences soil fungal community composition across central Victoria,south-eastern Australia     

Sabine Kasel  Lauren T. Bennett  Josquin Tibbits 《Soil biology & biochemistry》2008,40(7):1724-1732

Current theory expects that fungi, on the one hand, are spatially ubiquitous but, on the other, are more susceptible than bacteria to disturbance such as land use change due to dispersal limitations. This study examined the relative importance of location and land use effects in determining soil fungal community composition in south-eastern Australia. We use terminal restriction fragment length polymorphism (T-RFLP; primer pair ITS1-F–ITS4) and multivariate statistical methods (NMDS ordinations, ANOSIM tests) to compare relative similarities of soil fungal communities from nine sites encompassing three locations (ca 50–200 km apart) and four land uses (native eucalypt forest, Pinus radiata plantation, Eucalyptus globulus plantation, and unimproved pasture). Location effects were generally weak (e.g. ANOSIM test statistic R ≤ 0.49) and were, in part, attributed to minor differences in soil texture. By contrast, we found clear and consistent evidence of land use effects on soil fungal community composition (R ≤ 0.95). That is, soils from sites of the same land use grouped together in NMDS ordinations of fungal composition despite geographic separations of up to ca 175 km (native eucalypt forests) and 215 km (P. radiata plantations). In addition, different land uses from the same location were clearly separate in NMDS ordinations, despite, in one case, being just 180 m apart and having similar land use histories (i.e. P. radiata versus E. globulus plantation both established on pasture in the previous decade). Given negligible management of all sites beyond the early establishment phase, we attribute much of the land use effects to changes in dominant plant species based on consistent evidence elsewhere of strong specificity in pine and eucalypt mycorrhizal associations. In addition, weak to moderate correlations between soil fungal community composition and soil chemical variables (e.g. Spearman rank correlation coefficients for individual variables of 0.08–0.32), indicated a minor contributing role of vegetation-mediated changes in litter and soil chemistry. Our data provide evidence of considerable plasticity in soil fungal community composition over time spans as short as 6–11 years. This suggests that – at least within geographic zones characterised by more-or-less contiguous forest cover – soil fungal community composition depends most on availability of suitable habitat because dispersal propagules are readily available for colonisation after land use change.  相似文献   

Effect of wetting intensity on soil GHG fluxes and microbial biomass under a temperate forest floor during dry season     

Xingkai Xu  Xianbao Luo 《Geoderma》2012

The increasing frequency of periodic droughts followed by heavy rainfalls is expected for this current century, but little is known about the effects of wetting intensity on the in situ biogenic greenhouse gas (GHG) fluxes of forest soils and soil microbial biomass. To gain new insights into the underlying mechanisms responsible for wetting-induced GHG fluxes in situ, rain simulation field experiments during a natural prolonged drought period were done under a temperate forest in northeast China. The intensity of rainfall-induced CO₂ pulses increased from 0.84 to 2.08 g CO₂–C m^? 2 d^? 1 with the intensity of wetting up to ca. 80% water-filled pore space, which coincided with an increase in soil microbial biomass and with a decrease in soil labile organic C following wetting. Methane uptake rates decreased from 1.76 to 0.87 mg CH₄–C m^? 2 d^? 1 with the intensity of wetting. Wetting dry forest floor increased N₂O fluxes from 6.2 to 25.9 μg N₂O–N m^? 2 d^? 1, but there was no significant difference between all experimental wetted plots. The rainfall-induced N₂O pulses with increasing wetting intensity were opposite to that of the CO₂ pulses, showing a maximum response at the lowest wetting intensity. An analysis of the temperature sensitivity of GHG fluxes indicated that temperature had an increased effect on the in situ CO₂ flux and CH₄ uptake, respectively, under wetted and dry conditions. The global warming potential of GHG fluxes and Q₁₀ value of the temperature response of CO₂ fluxes increased linearly with wetting intensity. The results indicate that the rainfall-induced soil CO₂ pulse is mainly due to enhanced microbial consumption on substrates and highlight the complex nature of belowground C-cycling responses to climate change in northeast China forests that normally experience periodic droughts followed by heavy rainfalls over the year.  相似文献   

The influence of free-air CO2 enrichment on microorganisms of a paddy soil in the rice-growing season     

《Applied soil ecology》2007,35(1):154-162

The atmospheric CO₂ concentration is dramatically rising, and this rise may affect soil methanogens, methanotrophs, nitrifiers, and denitrifiers, which are important microorganisms for the processes of carbon and nitrogen turnover. An experimental platform of free-air CO₂ enrichment (FACE) was established in mid-June of 2001 over a rice–wheat rotation ecosystem located in a suburb of Wuxi, China, and its CO₂ fumigation was continued until mid-February of 2004. Using the most probable number (MPN) method, we measured the numbers of methanogens, methanotrophs, nitrifiers, and denitrifiers by sampling fresh soils from the fields exposed to the elevated and ambient CO₂ during the rice-growing season in 2002. Our results show that the elevated CO₂ significantly increased methanogen populations of the cultivated soil layers during the entire rice-growing season. This positive effect of elevated CO₂ may be attributed to stimulated rice growth, which may provide more substrates for methanogens. The methanotroph population was decreased by elevated CO₂ in the upper soil layer (0–5 cm) but was increased in the lower one (5–10 cm) in most rice-growing stages, and the effect of CO₂ elevation was reversed at rice maturity. Elevated CO₂ increased nitrifier and denitrifier populations in most rice stages, but it occasionally decreased the number of nitrifiers late in the growing season and that of denitrifiers early. The methanogen population gradually increased until the filling stage of rice growth but then declined under either elevated or ambient CO₂. Meanwhile the numbers of methanotrophs and nitrifiers gradually decreased during the entire rice season. The number of denitrifiers in the wet/flooded soil during the growing season was also decreased as compared to the dry soil before rice season.  相似文献   

Estimating heterotrophic and autotrophic soil respiration in a semi-natural forest of Lombardy,Italy     

Chiara Ferréa  Terenzio Zenone  Roberto Comolli  Günther Seufert 《Pedobiologia》2012,55(6):285-294

We studied a semi-natural forest in Northern Italy that was set aside more than 50 years ago, in order to better understand the soil carbon cycle and in particular the partitioning of soil respiration between autotrophic and heterotrophic respiration. Here we report on soil organic carbon, root density, and estimates of annual fluxes of soil CO₂ as measured with a mobile chamber system at 16 permanent collars about monthly during the course of a year. We partitioned between autotrophic and heterotrophic respiration by the indirect regression method, which enabled us to obtain the seasonal pattern of single components.The soil pool of organic carbon, with 15.8 (±4.5) kg m^?2, was very high over the entire depth of 45 cm. The annual respiration rates ranged from 0.6 to 6.9 μmol CO₂ m^?2 s^?1 with an average value of 3.4 (±2.3) μmol CO₂ m^?2 s^?1, and a cumulative flux of 1.1 kg C m^?2 yr^?1. The heterotrophic component accounted for 66% of annual CO₂ efflux. Soil temperature largely controlled the heterotrophic respiration (R² = 0.93), while the autotrophic component followed irradiation, pointing to the role of photosynthesis in modulating the annual course of soil respiration.Most studies on soil respiration partitioning indicate autotrophic root respiration as a first control of the spatial variability of the overall respiration, which originates mainly from the uppermost soil layers. Instead, in our forest the spatial variability of soil respiration was mainly linked to soil carbon, and deeper layers seemed to provide a significant contribution to soil respiration, a feature that may be typical for an undisturbed, naturally maturing ecosystem with well developed pedobiological processes and high carbon stocks.  相似文献   

Application of 13C-labeled litter and root materials for in situ decomposition studies using phospholipid fatty acids     

Jennifer Moore-Kucera  Richard P. Dick 《Soil biology & biochemistry》2008,40(10):2485-2493

Microorganisms play a central role in litter decomposition and partitioning C between CO₂ evolution and sequestration of C into semi-permanent pools in soils. At the ecosystem level, forest stand age influences rates of litter accumulation and quality, and micro-climatology which could affect the microbial community structure and C sequestration processes. Although numerous laboratory experiments have studied the decomposition of model ¹³C-labeled compounds, few studies have verified these findings under field conditions. The objective of this study was to track decomposition of ¹³C-labeled Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) materials into the soil microbial community using ¹³C-phospholipids fatty acid (PLFA) analysis in three different aged forest stands. A field experiment was conducted that had three forest stand age treatments: old-growth (>500 yrs); 8-year-old clear-cut (CC8); and 25-year-old clear-cut (CC25) (landscape reps of n = 2). Each stand age had in situ microcosms that were amended with either ¹³C-labeled surface litter or root material. Microcosms were destructively sampled seven times over a 22-month period and the soil was analyzed for the relative amounts of ¹³C incorporated (¹³C%_INCORP) into PLFAs and the proportional distribution of ¹³C incorporated into PLFAs. The ¹³C%_INCORP was affected by stand age and ¹³C source with greater ¹³C%_INCORP in samples from CC8 than OG or CC25. Also, the level of ¹³C%_INCORP was greater for labeled litter than root material in five out of the seven sample dates. In general, 18:1ω9 and 18:2ω6,9 (common fungal biomarkers) had the greatest amount of ¹³C incorporation throughout the study period in both clear-cut and old-growth sites, especially in plots with ¹³C-labeled litter. Our data showed a low fungal ¹³C-PLFA: bacterial ¹³C-PLFA ratio (0.45) 1 month after incubation was initiated compared to 5, 7 and 9 months after incubation (two of these dates were >1.0). This suggests that initially bacteria played a greater role in the decomposition of the added needles with fungi playing a more important role in subsequent sample dates. Our results illustrate that the use of ¹³C-labeled materials in field studies coupled with¹³C-PLFA profiling is a powerful tool for determining microbial dynamics during decomposition – enabling statistically significant detection of land management treatment effects on C acquisition by microbial functional groups.  相似文献