Chloroform Fumigation Extraction Method Research Articles

Assessment of Methods for Measuring Soil Microbial Biomass Carbon in Temperate Fruit Tree-Based Ecosystems

ABSTRACTWe investigated the potential of three methods of quantifying microbial biomass carbon (MBC), viz., chloroform fumigation-extraction (CFE) following organic C estimation through Vance method (CFE-V) and Snyder–Trofymow method (CFE-ST), and substrate-induced respiration (SIR) method in soils under various temperate fruit crops along with a control (no plantation) at 0–20 and 21–40 cm soil depths. CFE methods have shown significant (p < 0.05) increase in chloroform labile C in all orchards over the control in surface soil. The interaction between the fruit crops and methods, although significant (p < 0.01), indicated that CFE-ST and SIR methods were statistically at par with each other within the same fruit crop, except peach plantation (CEF-ST significantly lower than SIR) in 0–20 cm soil depth. The coefficient of variation recorded for chloroform labile organic C estimates by CFE-ST method makes it more precise than CFE-V method, especially in 0–20 cm soil depth. The very close agreement between the methods suggests that over this narrower range (i.e., smaller geographical area) all methods are appropriate for assessing MBC. However, SIR, being most sensitive to orchard plantations and strongly correlated with various soil chemical properties, could preferably be recommended for estimation of MBC in such soils. As an alternative to CFE-V method, CFE-ST may also be used for estimation of chloroform labile organic C in these soils.

Effects of grazing on microbial biomass C, N and respiration in Artemisia frigida rhizosphere soil

Artemisia frigida is a common plant, especially in degraded grasslands, on the Inner Mongolian steppes. To reveal the effects of grazing disturbance on soil microorganisms of the A. frigida rhizosphere, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and basal respiration and correlation were discussed, by the chloroform fumigation extraction method and the LI-7000 CO2/H2O system. Rhizosphere soil of A. frigida (ARS) and non-rhizosphere soil (NRS) under three grazing intensities, no grazing (CK) plot, light grazing (LG) plot, heavy grazing (HG) plot, were chosen as experimental sites in the Inner Mongolian steppes. Results showed that compared with the control group, the soil microbial biomass carbon, nitrogen and basal respiration after light grazing treatment increased by 22.7%, 45.0%, 17.2%, respectively. These bio-indicators in A. frigida rhizosphere soil were higher than non-rhizosphere soil of A. frigida (P < 0.05). Also, the increasing rate of MBN in rhizosphere and non-rhizosphere soil was higher than that of MBC. In the rhizosphere soil of Artemisia frigida, MBC had a positive correlation with organic matter (r = 0.737), total N (r = 0.798), available N (r = 0.945), and total K (r = 0.697). The MBN had a positive correlation with organic matter (r = 0.906), total N (r = 0.915), available N (r = 0.937), and total K (r = 0.691).The basal respiration had a positive correlation with organic matter (r = 0.507), total N (r = 0.446), available N (r = 0.805), and total K (r = 0.898). The light grazing treatment can contribute to a increase to microbial biomass and basal respiration rate. This study provided a theoretical basis for further exploring of ways that A. frigida could help resist grassland degradation.

Effects of nitrogen deposition on soil microbial communities in temperate and subtropical forests in China

Increasing nitrogen (N) deposition has aroused large concerns because of its potential negative effects on forest ecosystems. Although microorganisms play a vital role in ecosystem carbon (C) and nutrient cycling, the effect of N deposition on soil microbiota still remains unclear. In this study, we investigated the responses of microbial biomass C (MBC) and N (MBN) and microbial community composition to 4–5years of experimentally simulated N deposition in temperate needle-leaf forests and subtropical evergreen broadleaf forests in eastern China, using chloroform fumigation extraction and phospholipid fatty acid (PLFA) methods. We found idiosyncratic effects of N addition on microbial biomass in these two types of forest ecosystems. In the subtropical forests, N addition showed a significant negative effect on microbial biomass and community composition, while the effect of N addition was not significant in the temperate forests. The N addition decreased MBC, MBN, arbuscular mycorrhizal fungi, and the F/B ratio (ratio of fungi to bacteria biomass) in the subtropical forests, likely due to a decreased soil pH and changes in the plant community composition. These results showed that microbial biomass and community composition in subtropical forests, compared with the temperate forests, were sensitive to N deposition. Our findings suggest that N deposition may have negative influence on soil microorganisms and potentially alter carbon and nutrient cycling in subtropical forests, rather than in temperate forests.

The high correlation between DNA and chloroform-labile N in various types of soil

Based on the development of a direct DNA extraction method from soil, an estimation of soil microbial biomass by measurement of extracted soil DNA is presented. Chloroform-labile carbon (CLC) and nitrogen (CLN) determined by chloroform fumigation methods have been the major parameters of soil microbial biomass, but to date, there have been few studies of the relationship between DNA and CLN among soils with different characteristics. We applied DNA assays to the estimation of soil microbial biomass in various types of soil in Japan. The quantitative relationships among DNA, CLC and CLN released by the chloroform fumigation–extraction method were examined in 35 soil samples including five different soil types. The amount of DNA was moderately correlated with CLC (r=0.652, n=35), but there was no significant correlation in one of the soil types (fluvisol) representing a typical soil in Japan (r=0.124; n=15). Moreover, there was a strong correlation between DNA and CLN (r=0.887; n=35), and the correlation was high in every major soil type. These findings raise the possibility that DNA could be used to estimate biomass N even among different kinds of soil, with a conversion factor of 2.75 for DNA (μgg−1 soil).

Response of microbial biomass and bacterial community composition to fertilization in a salt marsh in China

The effects of nitrogen (N) addition on microbial biomass, bacterial abundance, and community composition in sediment colonized by Suaeda heteroptera were examined by chloroform fumigation extraction method, real-time quantitative polymerase chain reaction, and denaturing gradient gel electrophoresis (DGGE) in a salt marsh located in Shuangtai Estuary, China. The sediment samples were collected from plots treated with different amounts of a single N fertilizer (urea supplied at 0.1, 0.2, 0.4 and 0.8 g/kg (nitrogen content in sediment) and different forms of N fertilizers (urea, (NH4)2SO4, and NH4NO3, each supplied at 0.2 g/kg (calculated by nitrogen). The fertilizers were applied 1–4 times during the plant-growing season in May, July, August, and September of 2013. Untreated plots were included as a control. The results showed that both the amount and form of N positively influenced microbial biomass carbon, microbial biomass nitrogen, and bacterial abundance. The DGGE profiles revealed that the bacterial community composition was also affected by the amount and form of N. Thus, our findings indicate that short-term N amendment increases microbial biomass and bacterial abundance, and alters the structure of bacterial community.

Effect of grazing intensity on protozoan community, microbial biomass, and enzyme activity in an alpine meadow on the Tibetan Plateau

The alpine meadow has received mounting attention due to its degradation resulting from overgrazing on the Tibetan Plateau. However, belowground biotic characteristics under varied grazing stresses in this ecosystem are poorly understood. Here, the responses of soil protozoan abundance, community composition, microbial biomass, and enzyme activity to five grazing patterns including (1) artificial grassland without grazing (AG), (2) winter grazing (WG), (3) grazing for 7 months within a fence (GF), (4) continuous grazing for a whole year (CG), and (5) natural heavy grazing (HG) were investigated for two continuous years. Soil protozoan community composition was investigated using the most possible number (MPN) method, and soil microbial biomass and enzyme activity were analyzed using chloroform fumigation extraction and substrate utilization methods, respectively. Multivariate statistical analysis, the analysis of variance (ANOVA), multiple comparisons, and correlation analysis were together performed. The WG treatment had the highest abundance of total protozoa (2342–2524 cell g−1). Compared with AG treatment, HG treatment significantly reduced the abundance of soil total, flagellate and ciliate protozoa, and protease activities in 2012 and 2013. Significantly, lower soil microbial biomass nitrogen (MBN) was also observed in the HG (6.60 and 14.6 mg N kg−1) than those in other four treatments (22.3–82.9 mg N kg−1) both in 2012 and 2013, whereas significantly higher microbial biomass carbon (MBC) was observed in HG than that in AG treatment in 2012. Moreover, significantly positive correlations were detected between the abundance of soil protozoa and soil moisture, pH, organic C, total N, and MBN. Our results indicated that soil protozoa showed a negative response to increasing grazing intensities and therefore, suggesting that aboveground grazing practices also exerted strong impact on belowground protozoa, not only on soil microbial characteristics. Soil protozoan community composition was apparently different between the HG treatment and other four grazing patterns and was potentially impacted by altered soil properties and MBC and/or MBN. Our results suggested that moderate grazing may sustain better belowground biotic diversity and ecosystem functioning in this alpine meadow on the Tibetan Plateau.

Examination of residual chloroform interference in the measurement of microbial biomass C by fumigation-extraction

Using the chloroform fumigation-extraction (CFE) method for determining microbial biomass in soils, a presumption is followed, i.e., that chloroform becomes fully evacuated from the fumigated soil before extraction. Otherwise, the C-containing fumigant may comprise an unknown part of the extractable C flush, resulting in certain overestimation of soil microbial biomass. A quantitative assessment of extractable residual chloroform levels in fumigated soils was performed, testing soils varying in clay and organic matter contents. The tests were performed over a broad range of soil moisture conditions as to facilitate a mechanistic interpretation of possible chloroform interactions in the studied soils (i.e., dissolution, sorption). The results support the validity of the CFE method's application in agricultural soils, demonstrating the insignificance of biomass overestimation arising from residual chloroform.

Changes in soil microbial biomass and community composition in coastal wetlands affected by restoration projects in a Chinese delta

Severely degraded wetlands due to the lack of freshwater were restored by reintroducing freshwater through the placement of artificial dikes and channels in the Yellow River Delta (YRD) of China. Many studies have evaluated the performances of this restoration projects in aspects of vegetation, soils, hydrology, wildlife, etc. In contrast, limited information was available on the effects of restoration projects on the soil microbial biomass and community composition. To better understand the wetland restoration, differences in soil microbial biomass and community composition between restored tidal wetlands and unrestored wetlands under the disturbance of petroleum exploitation activities or tidal intrusion were assessed. Surface soils (0–10cm) under three different plant covers (Phragmites australis, Suaeda salsa and bare land) were collected from each three wetland zones. Chloroform fumigation-extraction (CFE) method and phospholipid fatty acid (PLFA) analysis were used to characterize soil microbial biomass and community composition. Our results showed significantly elevated microbial biomass in soils of the restoration zone, as indicated by both microbial biomass carbon and total PLFAs. Soil microbial community composition in the restoration zone also differed significantly from those in the petroleum exploitation zone and tidal zone. The freshwater input of restoration projects induced a soil microbial community shift to the increased relative abundance of fungi and decreased relative abundance of Desulfovibrio bacteria. The significantly promoted fungi in soils under P. australis of the restoration zone reflected the necessity of decomposers of the increased surface plant residues after restoration, which in turn contributed to the organic residues accumulation in soils and large aggregates formation by fungal hyphae. Meanwhile the modified soil carbon pool and aggregate structure following restoration of degraded wetland may favor the colonization of soil organisms. These results indicated that freshwater input had strongly altered soil microbial communities in the restored wetland, which may be of great significance in understanding the soil microbial responses to the restoration projects and the underlying mechanisms of wetland restoration.

Contrastive effects of inorganic phosphorus addition on soil microbial respiration and microbial biomass in tropical monoculture tree plantation soils in Thailand

An incubation experiment was conducted to test the effects of inorganic phosphorus (P) addition on soil microbial activities in tropical monoculture tree plantation soils. The soils taken from an experimental tree plantation site in Nakhon Ratchasima, Thailand were incubated for 48 h with and without adding 100 μg of P (KH2PO4) per gram soil after adjusting the water holding capacity to 80%. During the incubation period, the microbial biomass carbon (MBC) contents determined using the chloroform fumigation extraction method decreased and P addition stimulated the decreased rate significantly. On the other hand, the P addition increased the dissolved organic carbon (DOC) contents and CO2 emissions. The study suggested that P addition had changed soil microbial activities, possibly including a soil microbial community change. Furthermore, the study showed that the stimulated soil respiration by P addition is not necessarily accompanied by increased MBC. The assessment of the effects of P limitation on soil microbial activities should measure at least the effects of P addition on both soil respiration and MBC, possibly combined with soil microbial community analyses.

Relationship between presence of the desert shrub Haloxylon ammodendron and microbial communities in two soils with contrasting textures

Shrubs are usually dominated species for desert ecosystems, and resource islands often occurred around shrubs. It is widely considered that soils beneath shrub canopy have higher microbial diversity and biomass than those outside of the canopy. However, it remains poorly understood how shrubs affect this resource islands along soil profile and functional consequence on soil microbial community changes. Here, we showed distinct patterns of soil physiochemical properties and microbial communities along a soil profile outward from the taproot of Haloxylon ammodendron (C.A.Mey.) in two soils with contrasting textures: Torripsamments and Haplocalcids (USDA Soil Taxonomy). Soil samples were collected in circles with radii of 5, 40, 100 and 200cm respectively around the taproot in four randomly selected horizontal directions, and from respective depths of 0–20, 20–60 and 60–100cm. Microbial biomass and community composition were examined using a chloroform fumigation extraction and phospholipid fatty acids method. Redundancy analysis showed that the spatial variability of soil microbial communities was closely correlated with that of soil water and nutrients in both soils. Soil microbial biomass, soil water and nutrient contents had a similar decreasing trend along the increasing distance from the taproot. The coarse-textured Torripsamments showed stronger variability of soil water and nutrient contents than the fine-textured Haplocacids within the resource islands, and similar results were observed for soil microbial biomass. A clear trend of spatial variability (outward from taproot) for various microbial groups was observed in Torripsamments, but not in Haplocalcids. The biomass decreased to a lesser extent for total fungi than bacteria, and for Gram-positive than Gram-negative bacteria in Torripsamments. Our results suggest that the presence of H. ammodendron plays an important role in shaping the spatial variability of microbial communities in these desert ecosystems. Soil texture may determine the intensity of their spatial variability.

Decomposition, Nitrogen Release and Soil Fertility of Plant Residues Incorporation from Different Pre- Sugarcane Planting Management

The effect of decomposition, nitrogen release and soil fertility of upland rice-legume residues incorporation before sugarcane planting was investigated. The experimental design was randomized complete block design (RCBD) with 4 replications. The following residue and control treatments were implemented: i.e. i) control; no residues incorporation, ii) weed, iii) soybean (Glycine max), iv) sunn hemp (Crotalaria juncea) and v) upland rice. Soil samples and litter bags were collected at 1, 2, 4, 8, 12, 16, 24 and 32 weeks after incorporation. Soil mineral N was analyzed by Flow Injection Analyzer (FIA) and remaining dry weights of litter bag were recorded. Soil microbial biomass was measured by chloroform fumigation extraction method. The results revealed that weed residues treatment had the highest of remaining dry weight and % N remaining in litter bag in most sampling dates. Sunn hemp residues treatment had the highest soil mineral N and was significantly different from the other treatments (p < 0.01) at 4, 8, 12 and 16 weeks after residues incorporation. At final sampling date, the upland rice residues treatment gave the highest microbial biomass N and was significantly different from the other treatments (p < 0.01) and provided the highest relative microbial biomass N but not significantly different from soybean residues treatment. Moreover, soil organic matter could be improved by all residue treatments. However, sunn hemp may be a potential crop for soil N release but upland rice could support rice consumption demand. Thus, the effect of legume-upland rice residue incorporation on sugarcane yield should be further investigated under field conditions.

Potential nitrogen immobilization as influenced by available carbon in Japanese arable and forest soils

Microbial nitrogen (N) immobilization following the addition of organic materials to soils regulates soil N availability, which affects plant growth and N leaching from soils. In this study, the potential for microbial N immobilization was evaluated by short-term incubation experiments following the addition of available carbon (C) under non-limiting conditions of N and phosphorus (P) to seven Japanese arable and forest soils. Glucose was added as a model substrate at concentrations close to microbial biomass C. The forest soils had lower pH and smaller increases in respiration rates after the glucose addition, and higher organic and biomass C compared to the arable soils. Microbial N immobilization, estimated by net decreases in extractable N, was significantly correlated with the concentrations of added glucose and was on average 43 mg N g−1 glucose C during 3- and 7-day incubation for all soils. Net increases in biomass N measured by the chloroform fumigation-extraction method using the common conversion factor of 0.54 at 3 and 7 days after the glucose addition were lower than the microbial N immobilization for all soils, and the biomass N accounted for a smaller portion of immobilized N in the arable soils than in the forest soils. Therefore, the present study suggests that microbial N immobilization would be dependent on the concentrations of available C in organic materials and higher than the increases in biomass N, especially for arable soils when organic materials are added to soils under non-limiting conditions of N and P.

Spatial variability of soil microbial biomass and its relationships with edaphic, vegetational and climatic factors in the Three-River Headwaters region on Qinghai-Tibetan Plateau

This study aims to investigate the level of soil microbial biomass (MB) and analyze the relationships between soil MB and edaphic, vegetational and climatic factors at high elevation sites (>3000m). We collected soil samples from 0 to 10cm soil depth in 259 plots at 55 sites across 6 biomes in Three-River Headwaters (TRH) region at 3280–5127m elevation. Soil microbial biomass carbon and nitrogen (MBC and MBN) were measured with the chloroform fumigation–extraction method. Multivariate stepwise regression analyses were used to analyze the combined effects of edaphic, vegetational and climatic factors on soil MB. We found: (1) soil MBC and MBN had an average of 30.95mmol C/kg dry soil and 5.84mmol N/kg dry soil in TRH, respectively, and their values were found to be negatively correlated with elevation; (2) soil MB was found to be significantly different among different biomes, and this spatial variation could be explained by the levels of soil organic carbon and belowground plant biomass. Our results indicate that the MB at high elevation region might be very low, and the increasing trend of soil microbial biomass with elevation could reverse at higher elevations.

Short-term changes in microbial biomass and activity in soils under black locust trees (Robinia pseudoacacia L.) in the northwest of Turkey

The literature indicates that the presence and activity of microbial biomass could be potential indicators of other changes in mineral soils, making it useful for monitoring and assessing the relationships between plants and soil and their effects on the health and quality of the soil. Therefore, the aim of the study was to determine whether if there were any changes in the C and N content or the basal respiration of microbial biomass in soils under black locust trees (Robinia pseudoacacia L.) between 2013 and 2014. Samples of topsoil (0–6.5 cm) under the black locust were collected randomly from 12 different locations in 2013, and 12 samples were taken from the same locations in 2014. The C and N contents of the microbial biomass were determined by the chloroform fumigation extraction method. Basal respiration was determined by the sodium hydroxide (NaOH) trap method. The results demonstrated that the average C content of microbial biomass (Cmic) increased by about 55 % in soils under black locust and that the average N content (Nmic) of microbial biomass N increased by about 59 %. Both the Cmic and Nmic values were significantly affected by the temporal variation (P 0.05). Thus, it was concluded that the effect of black locust on the C and N content and basal respiration of the microbial biomass was due to the combined result of changing microclimatic conditions and soil characteristics, including the temperature, moisture content, pH, organic C, and total N in the soil. Therefore, this tree is an appropriate and valuable species where poor ecological conditions exist because of its rapid growth rate and its positive effect on the health and quality of soil.

Soil microbial community composition rather than litter quality is linked with soil organic carbon chemical composition in plantations in subtropical China

Purpose Native broadleaf plantations are increasingly being developed as an alternative to coniferous plantations. This studyexaminedtherelationshipsamonglittercarbon(C)quality, soil microbial community composition, and soil organic C (SOC) chemical properties in plantations and how they were affected by tree species. Materials and methods The solid-state 13 C nuclear magnetic resonance spectroscopy (NMR) technique was used to examine SOC chemical composition, and litter and fine root C quality in four plantations of native tree species (Pinus massoniana, Castanopsis hystrix, Michelia macclurei, and Mytilaria laosensis) in Pingxiang, Guangxi Zhuang AutonomousRegion,insubtropicalChina.Soilmicrobialbiomass C and nitrogen (N) were determined by the chloroform fumigation-extraction method and soil bacterial and fungal biomass were measured with the phospholipid fatty acid (PLFA) technique. Results and discussion The proportions of O-alkyl C, alkyl C, aromatic C, and carbonyl C in SOC and the alkyl/O-alkyl C ratio (A/O-A) in litter and fine root samples, soil microbial C and N, microbial C/N ratios, and the amount of PLFAs were significantly different among the four plantations of different species. SOC in the 0–10-cm layer had 43–49 % O-alkyl C, 24–34 % alkyl C, 14–17 % aromatic C, and 9–11 % carbonyl C in SOC. The microbial C/N ratio, the amount of total PLFAs, and bacterial and Gram-positive bacterial population sizes were linked to the proportion of alkyl C in SOC and the A/O-A ratio in soil. The proportion of alkyl C in SOC was not related to the proportion of alkyl C in litter or fine root samples. Conclusions The microbial community composition rather than plant litter or fine root quality was linked to chemical composition of SOC in the studied subtropical plantations. Future research should place more emphasis on the processes involved in the formation of SOC and their association with the microbial community.

Effect of Fire Disturbance on Nutrient Content and Soil Microbial Biomass of Two Forest Types

In the burned area of Betula platyphylla and Larix gmelinii forests shortly after the fire in Yichun,we used the chloroform fumigation extraction method to examine the content of soil microbial biomass carbon( Cmic) and soil microbial biomass nitrogen( Nmic) from the two forest types in different months( June,August,October and December). We explored the relationship between Cmicand Nmic,and the influencing factors including soil water content,soil p H,soil temperature,soil organic carbon and soil total nitrogen after the fire.The overall mean Cmicof the burned plots was lower than that in the unburned plots,and the overall mean Nmic was increased after the fire in B. platyphylla. Compared with the unburned plots,Cmichad no significant effect in different months shortly after the fire,the mean Cmicin June,August,October and December in the burned plots( unburned plots) was 1 389. 6( 1247. 2),886. 7( 759. 0),1 098. 9( 1 052. 6) and 1 421. 4( 1 749. 7) mg·kg- 1,respectively,yet the Nmicwas significant higher than that in the unburned plots in June,August and Octoberwith the mean Nmicof 214. 5( 143. 4),101. 9( 67. 5),119. 6( 89. 4) and 150. 2( 183. 3) mg · kg- 1,respectively. The soil microbial biomass was positively correlated to the soil water content,and Nmicwas influenced by soil p H significantly. Compared with the unburned plots,the overall mean Cmicand Nmicof the burned plots were lower than those in L. gmelini. The soil microbial biomass had no significant effect throughout different months of L. gmelinii. The mean Cmicin June,August,October and December in the burned plots( unburned plots) was 689. 7( 695. 9),612. 3( 910. 4),361. 6( 474. 7) and 1288. 5( 1353. 8) mg·kg- 1,respectively,and the mean Nmicwas 105. 7( 124. 4),91. 4( 111. 4),44. 0( 76. 9) and 118. 9( 134. 5) mg ·kg- 1,respectively. Cmicand Nmicwere significantly positively correlated with soil water content,but negatively with soil p H. The overall mean soil p H,soil organic carbon and soil total nitrogen of the burned plots were higher than the unburned plots,yet oil water content was decreased in Betula platyphylla. The overall mean soil p H,soil organic carbon and soil total nitrogen of the burned plots were lower than that in the unburned plots,however,soil water content was increased after the fire in L. gmelinii.

Effects of vegetation type on microbial biomass carbon and nitrogen in subalpine mountain forest soils

Microbial biomass plays an important role in nutrient transformation and conservation of forest and grassland ecosystems. The objective of this study was to determine the microbial biomass among three vegetation types in subalpine mountain forest soils of Taiwan. Tatachia is a typical high-altitude subalpine temperate forest ecosystem in Taiwan with an elevation of 1800-3952 m and consists of three vegetation types: spruce, hemlock, and grassland. Three plots were selected in each vegetation type. Soil samples were collected from the organic layer, topsoil, and subsoil. Microbial biomass carbon (Cmic) was determined by the chloroform fumigation-extraction method, and microbial biomass nitrogen (Nmic) was determined from the total nitrogen (Ntot) released during fumigation-extraction. Bacteria, actinomycetes, fungi, cellulolytic microbes, phosphate-solubilizing microbes, and nitrogen-fixing microbes were also counted. The Cmic and Nmic were highest in the surface soil and declined with the soil depth. These were also highest in spruce soils, followed by in hemlock soils, and were lowest in grassland soils. Cmic and Nmic had the highest values in the spring season and the lowest values in the winter season. Cmic and Nmic had significantly positive correlations with total organic carbon (Corg) and Ntot. Contributions of Cmic and Nmic, respectively, to Corg and Ntot indicated that the microbial biomass was immobilized more in spruce and hemlock soils than in grassland soils. Microbial populations of the tested vegetation types decreased with increasing soil depth. Cmic and Nmic were high in the organic layer and decreased with the depth of layers. These values were higher for spruce and hemlock soils than for grassland soils. Positive correlations were observed between Cmic and Nmic and between Corg and Ntot.

Partitioning Sources of Ecosystem and Soil Respiration in an Alpine Meadow of Tibet Plateau Using Regression Method

ABSTRACT: Partitioning sources of ecosystem and soil respiration (R eco and Rs) is important for understanding how climate change affects carbon cycling. Plant and microbial biomass analyses and daytime measurements of Reco and Rs were performed for 25 plots in an alpine meadow at elevation 4313 m on the Tibetan Plateau. Plant and microbial biomass were determined by harvesting method and the chloroform fumigation-extraction method, respectively. Respiration fluxes were measured by an automated CO2 flux system (LI-8100, LI-COR Biosciences, Lincoln, NE, USA). Soil respiration can be estimated by a linear or exponential relationship between Reco and aboveground plant biomass (AGB). Microbial respiration (Rm) can be estimated by a linear or exponential relationship between Rs and belowground plant biomass (BGB) or by a multiple relationship between Reco and AGB and BGB. Soil respiration (or Rm) is respiration flux when AGB (or BGB) is extrapolated to zero for the linear and exponential regression methods. Si...

峡谷型喀斯特不同生态系统的土壤微生物数量及生物量特征

Determining the relationship between soil microbial populations and soil microbial biomass in ecosystems can provide useful information for vegetation restoration in the canyon Karst region. Therefore,based on a combination of field investigation and laboratory analysis,we analyzed soil microbial populations and soil microbial biomass at different soildepths as well as their fractal relationships under six typical ecosystems,i. e.,paddy field,dry land,grassland,Shrubbery,plantation forest,and secondary forest,in the canyon Karst region in southwest China. Three plots with size of20 m × 20 m were constructed in each ecosystem type,and five soil samples were collected at four corners and the middle in each plot and then mixed as one sample. The dilution plate method and the chloroform fumigation extraction method were used to determine soil microbial populations and soil microbial biomass.,respectively. The results showed that soil microbial populations and composition varied under different ecosystems in the canyon karst region. Soil microbial populations were largest in the secondary forest,followed by the plantation forest,while least in the dry land,indicating that the project of returning crop land to forests or grassland have a significant impact on increasing the soil microbial populations. Microbial composition in the six ecosystems performed in the order of bacteria actinomycetes fungi. The bacteria number was 26. 66×105—71.64×105cfu /g with the highest proportion of 87. 00% —95. 50% of total soil microbial number; followed by actinomycetes,whose number and proportion were 1. 45 × 105—3. 78×105cfu /g and 4. 21% —12.39%,respectively. However,the fungi quantity was 0. 07×105—0.23×105cfu /g,and the proportion was less than 1%,just only 0. 24% —0. 61%. Under different ecosystem types,soil microbial biomass carbon( MBC),soil microbial biomass nitrogen( MBN),and soil microbial biomass phosphorus( MBP) were diverse,but all of them appeared to be a trend of MBC MBN MBP. Soil MBC and MBN was highest in the secondary forest,while MBP was highest in the plantation forest,in comparison with that MBC was lowest in the dry land,MBN and MBP were lowest in the grass. The ratios of MBC /SOC,MBN /TN and MBP /TP ranged from 0. 44% —0. 97%,2. 13% —3. 13%, and 1. 46% —2. 13%,respectively,with no significant differences among the six ecosystems. The value of MBC /MBN ranged from 3. 06 to 6. 54,which in the secondary forest was significantly higher than that in other ecosystems; however,no significant differences existed among the rest ecosystems. A good fractal relationship existed between soil microbial populations and soil microbial biomass at a highly significant level( P0. 01). Moreover,both soil microbial populations and soil microbial biomass in the six ecosystems decreased as an increase in soil depth. As a result,exploring soil microbial activities could provide the basis for improving the soil fertility of lime soil and boosting vegetation restoration in karst regions.

小兴安岭6种森林类型土壤微生物量的季节变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 小兴安岭6种森林类型土壤微生物量的季节变化特征 DOI: 10.5846/stxb201304050608 作者: 作者单位: 东北林业大学,东北林业大学生态研究中心;黑龙江省森林工程与环境研究所,东北林业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业科研专项资助项目（201204320）；长江学者和创新团队发展计划资助项目（IRT1054） Seasonal dynamics of soil microbial biomass in six forest types in Xiaoxing’an Mountains, China Author: Affiliation: Center for Ecological Research, Northeast Forestry University,,Center for Ecological Research, Northeast Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤微生物是森林生态系统的重要调节者和分解者，其微生物量是陆地生态系统碳氮循环的重要组成部分。采用氯仿熏蒸浸提法测定了小兴安岭6种森林类型不同季节的土壤微生物量碳（MBC）和氮（MBN），并分析了其与土壤环境因子的关系，探讨根系去除对土壤微生物量的影响。结果表明：MBC和MBN的季节变化因森林类型的差异而有所不同，但最高值多发生在8月中旬；MBC和MBN在根系去除后均有不同程度的减少；MBC和MBN分别与土壤有机碳、全氮及含水量呈显著正相关（P < 0.05）；MBN与土壤温度呈极显著正相关（P < 0.01）。显然，研究区的土壤微生物量受土壤温度、湿度及土壤有效养分综合作用的影响。 Abstract:Soil microbes are the most important regulator and decomposer in the forest ecosystem. Soil microbial biomass is an important component of the carbon and nitrogen cycles in the terrestrial ecosystem. The Heilongjiang Liangshui Nature Reserve has full gradient interference, which includes virgin forests, secondary forests, and plantation forests. The reserve provides a good platform to explore soil microbial biomass and to determine the factors influencing soil microbial biomass in the Xiaoxing'an Mountains. We used the chloroform fumigation extraction method to measure and compare the microbial biomass carbon (MBC), the microbial biomass nitrogen (MBN), and the influencing factors (i.e., soil organic carbon, soil total nitrogen, soil water content and soil temperature) throughout the growing season. We also explored the effect of root removal on soil microbial biomass. The experiment included six typical forest types, namely, virgin mixed broadleaved-Korean pine (Pinus koraiensis) forest, selectively cut mixed broadleaved-Korean pine forest, secondary birch (Betula platyphylla) forest, artificial larch (Larix gmelinii) plantation, artificial Korean pine forest, and valley spruce-fir (Picea-Abies) forest. Each forest type consists of three 20 m × 30 m plots, and four 2 m × 2 m root trenching subplots and four 2 m × 2 m control subplots were randomly chosen in each plot. Soil samples from 0 cm to 10 cm soil layers were randomly selected monthly from the six forest types from June 2010 to October 2010. The samples in each plot were mixed as one sample to determine MBC and MBN. Results show that the seasonal changes in the soil microbial biomass of the six forest types were different during the study period. The maximum soil microbial biomass was mostly obtained in mid-August. The MBC and MBN generally showed similar seasonal dynamics in the control and root removal plots. The average values of MBC and MBN for the six forest types varied from 383.5 mg/kg to 1633.6 mg/kg and 47.6 mg/kg to 231.0 mg/kg, respectively, accounting for 1% to 2% and 2% to 4% of the soil organic carbon and nitrogen content. The average soil microbial biomass (MBC and MBN, respectively) of each forest type was recorded as follows: secondary birch forest (1318.8 and 215.5 mg/kg) > artificial Korean pine forest (1137.3 and 169.1 mg/kg) > selectively cut mixed broadleaved-Korean pine forest (980.3 and 153.4 mg/kg) > virgin mixed broadleaved-Korean pine forest (948.9 and 143.6 mg/kg) > artificial larch forest (927.2 and 131.0 mg/kg) > valley spruce-fir forest (606.2 and 95.0 mg/kg). Root removal significantly decreased soil microbial biomass (P < 0.01). The maximum MBC (44%) and MBN (34%) reductions were found in the valley spruce-fir forest and the artificial larch forest, respectively. The minimum MBC (12%) and MBN (11%) reductions were found in the selectively cut mixed broadleaved-Korean pine forest. MBC and MBN were significantly positively correlated with soil organic carbon, soil total nitrogen, and soil water content (P < 0.05), and MBN was significantly positively correlated with soil temperature (P < 0.01). We concluded that the combined effects of soil temperature, soil water content, and soil nutrients contributed to the differences in the soil microbial biomass found across the six forest types. 参考文献 相似文献 引证文献