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41.
不同林龄马尾松人工林土壤微生物群落结构和功能多样性演变 总被引：1，自引：0，他引：1
土壤微生物在森林生态系统中起着至关重要的作用,研究人工林演变中土壤微生物群落结构特征,对评价人工林土壤质量动态变化和维持土壤微生态平衡具有重要意义。以亚热带地区马尾松人工林为研究对象,采用磷脂脂肪酸(Phospholipid fatty acid,PLFA)和BIOLOG技术研究不同林龄(13 a,25 a,38 a和58 a)对土壤微生物群落结构和代谢功能多样性的影响。结果表明:不同林龄土壤微生物类群均以细菌为主,其次为真菌和放线菌,最后为原生动物;土壤微生物总PLFAs量、真菌数量和真菌/细菌均表现为13 a最高,38 a最低;土壤细菌、革兰氏阳性细菌(G+)、革兰氏阴性细菌(G–)和放线菌数量均25a最高。层次聚类和主成分分析(PCA)结果表明,林龄对土壤微生物群落结构产生显著影响,13 a和25 a林龄分别与38 a和58 a林龄的土壤微生物群落结构差异较大。冗余分析表明,有机碳、全氮和pH是土壤微生物群落结构的主要影响因素。不同林龄土壤平均颜色变化率(AWCD)和微生物功能多样性指数(香农指数、辛普森指数和McIntosh指数)总体表现为25 a13 a58 a38 a;不同林龄土壤微生物对碳源的利用存在差异,各林龄利用的主要碳源为氨基酸类、羧酸类和酚类,其中25a在各碳源中利用率最高。PLFA和BIOLOG综合分析可知,马尾松人工林种植25 a后,土壤微生物群落结构稳定性和功能代谢活性明显降低,加剧了土壤微生态失衡。 相似文献
42.
Elevated CO2 usually promotes plant growth, whereas elevated O3 often has a negative effect, especially on root biomass. Thus both these gases can indirectly affect the soil microbial community. We exposed Agrostis capillaris and Lathyrus pratensis to realistic levels of O3 (40-50 ppb) and CO2 (ambient air + 100 ppm) in open-top chambers during 2002-2004. The experiment shows negative effects of both O3 and CO2, especially on the bulk soil of L. pratensis, in terms of the decreased biomasses of total (25% and 31%), actinobacterial (29% and 31%), bacterial (26% and 33%) and mycorrhizal (AM fungal) (31% and 35%) indicator subgroups, analysed by the PLFA (phospholipid fatty acid) method. The fungal:bacterial PLFA biomass ratio decreased in the bulk soil of A. capillaris, especially with elevated CO2 alone (38%). These longer-term changes are considered to arise mainly from differences between the plant functional types (i.e. grass cf. N2-fixing legume) in litter quality and soil C:N ratio. The results also point to interactions and multi-trophic feedbacks between elevated O3, plant, parasitic rust fungi and soil readily available P, accompanied by a shift in N balance in favour of plants rather than soil microorganisms. 相似文献
43.
Natalia Ladygina 《Soil biology & biochemistry》2010,42(2):162-168
Plant species effects on microbial communities are attributed to changes in microbial community composition and biomass, and may depend on plant species specific differences in the quality of resources (carbon) inputs. We examined the idea that plant-soil feedbacks can be explained by a chance effect, which is the probability of a highly productive or keystone plant species is present in the community and will influence the functions more than the number of species per se. A 13C pulse labelling technique was applied to three plant species and a species mixture in a greenhouse experiment to examine the carbon flow from plants to soil microbial communities. The 13C label was given as CO2 to shoots of a legume (Lotus corniculatus), a forb (Plantago lanceolata), a grass (Holcus lanatus) and a mixture of the three species. Microbial phospholipid fatty acids (PLFA) was analysed in order to determine the biomass and composition of the soil microbial community. The incorporation of the stable isotope into soil microorganisms was determined through GC-IRMS analyses of the microbial PLFAs. Plant species identity did not influence the microbial biomass when determined as total carbon of microbial phospholipid fatty acids. However, the labelled carbon showed that the grass monoculture (H. lanatus) and the plant mixture allocated more 13C into bacteria and actinomycete biomass than the other plant species. H. lanatus monocultures had also the highest amounts of 13C allocated to AM-fungi and saprophytic fungi. The carbon allocation from plants to soil microorganisms in a plant species mixture can thus be explained by the presence of a highly productive species that influence soil functions. 相似文献
44.
Soil microorganisms are key regulators of the biogeochemical phosphorus (P) cycle. Microbial P limitation in highly weathered tropical soils has been reported, but whether it affects the cellular P content of indigenous soil microorganisms and its biochemical composition is unknown. We investigated the effect of microbial P limitation by measuring respiration, microbial growth, community composition and P content of microbial cells in a Ferralsol with low amounts of available P as affected by amendments with C substrates with ample nitrogen (CN) with and without extra phosphate (P). Microbial biomass and community composition were quantified by phospholipid fatty acid (PLFA) analyses. Cellular P content and P pools (PLFA, DNA and RNA per cell) were determined after extraction of microbial cells from soil by density gradient centrifugation. The apparent microbial growth rate during exponential increase in respiration rates in response to CNP addition was 0.072 h−1, compared to 0.017 h−1 for the CN amendment (no extra P added). This suggests that the microbial growth after a combined C and N addition was retarded by P limitation in the native soil (without added P). The net increase in microbial biomass, however, reached similar levels for both the CN and CNP treatment (measured at the point in time when respiration rates peaked). This outcome was unexpected since maximum respiration rates were about three times higher in the CNP compared to the CN treatment. Total P in extracted cells ranged from 2.1 to 8.9 fg P cell−1 (microscopic counts), with a tendency for lower values for treatments without C amendments. Only 10-25% of the measured total P in extracted cells was accounted for by the measured RNA, DNA and PLFA. This low percentage could partly be due to underestimation of the RNA pool (degradation during extraction). PLFA analyses showed that substrate induced growth, regardless of P addition, led to a change in microbial community composition and was dominated by fungi. The extraction of microbial cells from soil by density gradient centrifugation, however, discriminates against fungi. Accordingly, the extracted cells were not fully representative for the entire soil microbiota regarding the community composition and metabolic state. Nevertheless, for the first time microbial cell P content and P pools are reported for microorganisms that actually grew in soil and not in chemostat or batch cultures. 相似文献
45.
Christiane Kramer Mats Fröberg Luz Maria Cisneros Dozal Dachun Zhang Guaciara M. Santos 《Soil biology & biochemistry》2010,42(7):1028-56
Microbial communities in soil A horizons derive their carbon from several potential sources: organic carbon (C) transported down from overlying litter and organic horizons, root-derived C, or soil organic matter. We took advantage of a multi-year experiment that manipulated the 14C isotope signature of surface leaf litter inputs in a temperate forest at the Oak Ridge Reservation, Tennessee, USA, to quantify the contribution of recent leaf litter C to microbial respiration and biomarkers in the underlying mineral soil. We observed no measurable difference (<∼40‰ given our current analytical methods) in the radiocarbon signatures of microbial phospholipid fatty acids (PLFA) isolated from the top 10 cm of mineral soil in plots that experienced 3 years of litterfall that differed in each year by ∼750‰ between high-14C and low-14C treatments. Assuming any difference in 14C between the high- and low-14C plots would reflect C derived from these manipulated litter additions, we estimate that <∼6% of the microbial C after 4 years was derived from the added 1-4-year-old surface litter. Large contributions of C from litter < 1 year (or >4 years) old (which fell after (or prior to) the manipulation and therefore did not differ between plots) are not supported because the 14C signatures of the PLFA compounds (averaging 200-220‰) is much higher that of the 2004-5 leaf litter (115‰) or pre-2000 litter. A mesocosm experiment further demonstrated that C leached from 14C-enriched surface litter or the O horizon was not a detectable C source in underlying mineral soil microbes during the first eight months after litter addition. Instead a decline in the 14C of PLFA over the mesocosm experiment likely reflected the loss of a pre-existing substrate not associated with added leaf litter. Measured PLFA Δ14C signatures were higher than those measured in bulk mineral soil organic matter in our experiments, but fell within the range of 14C values measured in mineral soil roots. Together, our experiments suggest that root-derived C is the major (>60%) source of C for microbes in these temperate deciduous forest soils. 相似文献
46.
We have investigated the structure of a microbial community in semi-natural sandy grassland in southeast Sweden. The sand is rich in lime, but in most places the soil is decalcified in the upper layers, and therefore this site shows a large variation in pH within short distances. We collected samples at three different soil depths (0-10 cm, 10-20 cm and 20-30 cm) and found the pH to range from 5 to 8 in the topsoil and from 4.5 to 9.5 in the deepest layer. The abundance of saprophytic fungi and bacteria was investigated using signature phospholipid fatty acids and arbuscular mycorrhizal fungi (AMF) using the neutral lipid fatty acid 16:1ω5. The PLFA pattern of the topsoil was different from that in the other two layers, as indicated by principal component analysis. The saprotrophic fungi were associated with high pH, and bacteria with low pH in these sandy soils. No relation was found between pH and AMF in the topsoil, while a positive relation was found in the deepest soil layer. The saprophytic fungi-to-bacteria ratio was constant with depth, while the AMF-to-bacteria ratio increased with soil depth. The results showed that high soil pH favoured fungal saprophytes in sandy grasslands and that AMF are relatively more abundant than the other two groups in deeper soil layers; particularly so when the pH is high. 相似文献
47.
M. Rubino J.A.J. Dungait R.P. Evershed P. De Angelis A. Lagomarsino A. Merola M.F. Cotrufo 《Soil biology & biochemistry》2010,42(7):1009-1016
Partitioning of the quantities of C lost by leaf litter through decomposition into (i) CO2 efflux to the atmosphere and (ii) C input to soil organic matter (SOM) is essential in order to develop a deeper understanding of the litter-soil biogeochemical continuum. However, this is a challenging task due to the occurrence of many different processes contributing to litter biomass loss. With the aim of quantifying different fluxes of C lost by leaf litter decomposition, a field experiment was performed at a short rotation coppice poplar plantation in central Italy. Populus nigra leaf litter, enriched in 13C (δ13C ∼ +160‰) was placed within collars to decompose in direct contact with the soil (δ13C ∼ −26‰) for 11 months. CO2 efflux from within the collars and its isotopic composition were determined at monthly intervals. After 11 months, remaining litter and soil profiles (0-20 cm) were sampled and analysed for their total C and 13C content. Gas chromatography (GC), GC-mass spectrometry (MS) and GC-combustion-isotope ratio (GC/C/IRMS) were used to analyse phospholipid fatty acids (PLFA) extracted from soil samples to identify the groups of soil micro-organisms that had incorporated litter-derived C and to determine the quantity of C incorporated by the soil microbial biomass (SMB). By the end of the experiment, the litter had lost about 80% of its original weight. The fraction of litter C lost as an input into the soil (67 ± 12% of the total C loss) was found to be twice as much as the fraction released as CO2 to the atmosphere (30 ± 3%), thus demonstrating the importance of quantifying litter-derived C input to soils, in litter decomposition studies. The mean δ13C values of PLFAs in soil (δ13C = −12.5‰) showed sustained incorporation of litter-derived C after one year (7.8 ± 1.6% of total PLFA-C). Thus, through the application of stable 13C isotope analyses, we have quantified two major C fluxes contributing to litter decomposition, at macroscopic and microscopic levels. 相似文献
48.
Daniel L. Mummey Jeffrey T. Clarke Callie A. Cole Benjamin G. O’Connor James E. Gannon Phillip W. Ramsey 《Soil biology & biochemistry》2010,42(7):1138-1147
Knowledge of how forest management influences soil microbial community interactions is necessary for complete understanding of forest ecology. In this study, soil microbial communities, vegetation characteristics and soil physical and chemical properties were examined across a rectangular 4.57 × 36.58 m sample grid spanning adjacent coniferous forest and clearcut areas. Based on analysis of soil extracted phospholipid fatty acids, total microbial biomass, fungi and Gram-negative bacteria were found to be significantly reduced in soil of the clearcut area relative to the forest. Concurrent with changes in microbial communities, soil macroaggregate stability was reduced in the clearcut area, while no significant differences in soil pH and organic matter content were found. Variography indicated that the range at which spatial autocorrelation between samples was evident (patch size) was greater for all microbial groups analyzed in the clearcut area. Overall, less spatial structure could be resolved in the forest. Variance decomposition using principal coordinates of neighbor matrices spatial variables indicated that soil aggregate stability and vegetation characteristics accounted for significant microbial community spatial variation in analyses that included the entire plot. When clearcut and forest areas were analyzed separately, different environmental variables (pH in the forest area and soil organic matter in the clearcut) were found to account for variation in soil microbial communities, but little of this variation could be ascribed to spatial interactions. Most microbial variation explained by different components of microbial communities occurred at spatial scales other than those analyzed. Fungi accounted for over 50% of the variation in bacteria of the forest area but less than 11% in the clearcut. Conversely, AMF accounted for significant variation in clearcut area, but not forest, bacteria. These results indicate broadly disparate controls on soil microbial community composition in the two systems. We present multiple lines of evidence pointing toward shifts in fungi functional groups as a salient mechanism responsible for qualitative, quantitative and spatial distribution differences in soil microbial communities. 相似文献
49.
Natalia Ladygina Frederic Henry Robert Koller Alia Rodriguez Ilja Sonnemann Susanne Wurst 《Soil biology & biochemistry》2010,42(12):2266-2275
The productivity and diversity of plant communities are affected by soil organisms such as arbuscular mycorrhizal fungi (AMF), root herbivores and decomposers. However, it is unknown how interactions between such functionally dissimilar soil organisms affect plant communities and whether the combined effects are additive or interactive. In a greenhouse experiment we investigated the individual and combined effects of AMF (five Glomus species), root herbivores (wireworms and nematodes) and decomposers (collembolans and enchytraeids) on the productivity and nutrient content of a model grassland plant community as well as on soil microbial biomass and community structure. The effects of the soil organisms on productivity (total plant biomass), total root biomass, grass and forb biomass, and nutrient uptake of the plant community were additive. AMF decreased, decomposers increased and root herbivores had no effect on productivity, but in combination the additive effects canceled each other out. AMF reduced total root biomass by 18%, but decomposers increased it by 25%, leading to no net effect on total root biomass in the combined treatments. Total shoot biomass was reduced by 14% by root herbivores and affected by an interaction between AMF and decomposers where decomposers had a positive impact on shoot growth only in presence of AMF. AMF increased the shoot biomass of forbs, but reduced the shoot biomass of grasses, while root herbivores only reduced the shoot biomass of grasses. Interactive effects of the soil organisms were detected on the shoot biomasses of Lotus corniculatus, Plantago lanceolata, and Agrostis capillaris. The C/N ratio of the plant community was affected by AMF.In soil, AMF promoted abundances of bacterial, actinomycete, saprophytic and AMF fatty acid markers. Decomposers alone decreased bacterial and actinomycete fatty acids abundances but when decomposers were interacting with herbivores those abundances were increased. Our results suggests that at higher resolutions, i.e. on the levels of individual plant species and the microbial community, interactive effects are common but do not affect the overall productivity and nutrient uptake of a grassland plant community, which is mainly affected by additive effects of functionally dissimilar soil organisms. 相似文献
50.
Recent studies suggest the long-standing discrepancy between measured and modeled leaf litter decomposition in drylands is, in part, the result of a unique combination of abiotic drivers that include high soil surface temperature and radiant energy levels and soil-litter mixing. Temperature and radiant energy effects on litter decomposition have been widely documented. However, under field conditions in drylands where soil-litter mixing occurs and accelerates decomposition, the mechanisms involved with soil-litter mixing effects are ambiguous. Potential mechanisms may include some combination of enhanced microbial colonization of litter, physical abrasion of litter surfaces, and buffering of litter and its associated decomposers from high temperatures and low moisture conditions. Here, we tested how soil-litter mixing and soil moisture interact to influence rates of litter decomposition in a controlled environment. Foliar litter of two plant species (a grass [Eragrostis lehmanniana] and a shrub [Prosopis velutina]) was incubated for 32 weeks in a factorial combination of soil-litter mixing (none, light, and complete) and soil water content (2, 4, 12% water-filled porosity) treatments. Phospholipid fatty acids (PLFAs) were quantified one week into the experiment to evaluate initial microbial colonization. A complementary incubation experiment with simulated rainfall pulses tested the buffering effects of soil-litter mixing on decomposition.Under the laboratory conditions of our experiments, the influence of soil-litter mixing was minimal and primarily confined to changes in PLFAs during the initial stages of decomposition in the constant soil moisture experiment and the oscillating soil moisture conditions of the rainfall pulse experiment. Soil-litter mixing effects on CO2 production, total phospholipid concentrations, and bacterial to total PLFA ratios were observed within the first week, but responses were fairly weak and varied with litter type and soil moisture treatment. Across the entire 32-week incubation experiment, soil moisture had a significant positive effect on mass loss, but soil-litter mixing did not. The lack of strong soil-litter mixing effects on decomposition under the moderate and relatively constant environmental conditions of this study is in contrast to results from field studies and suggests the importance of soil-litter mixing may be magnified when the fluctuations and extremes in temperature, radiant energy and moisture regimes common dryland field settings are in play. 相似文献