土壤微生物量测定方法概述

土壤微生物量是土壤生态系统研究的重要参数之一。常用的土壤微生物量的测定方法主要包括:直接镜检法、熏蒸系列方法、底物诱导系列方法、成分分析法和比色法。对这些具体测定方法、原理及其优缺点进行了简要的评述,并指出了应用这些方法须注意的问题和今后的研究方向。     

Soil Microbial Biomass,Basal Respiration and Enzyme Activity of Main Forest Types in the Qinling Mountains

Different forest types exert essential impacts on soil physical-chemical characteristics by dominant tree species producing diverse litters and root exudates, thereby further regulating size and activity of soil microbial communities. However, the study accuracy is usually restricted by differences in climate, soil type and forest age. Our objective is to precisely quantify soil microbial biomass, basal respiration and enzyme activity of five natural secondary forest (NSF) types with the same stand age and soil type in a small climate region and to evaluate relationship between soil microbial and physical-chemical characters. We determined soil physical-chemical indices and used the chloroform fumigation-extraction method, alkali absorption method and titration or colorimetry to obtain the microbial data. Our results showed that soil physical-chemical characters remarkably differed among the NSFs. Microbial biomass carbon (Cmic) was the highest in wilson spruce soils, while microbial biomass nitrogen (Nmic) was the highest in sharptooth oak soils. Moreover, the highest basal respiration was found in the spruce soils, but mixed, Chinese pine and spruce stands exhibited a higher soil qCO₂. The spruce soils had the highest Cmic/Nmic ratio, the greatest Nmic/TN and Cmic/Corg ratios were found in the oak soils. Additionally, the spruce soils had the maximum invertase activity and the minimum urease and catalase activities, but the maximum urease and catalase activities were found in the mixed stand. The Pearson correlation and principle component analyses revealed that the soils of spruce and oak stands obviously discriminated from other NSFs, whereas the others were similar. This suggested that the forest types affected soil microbial properties significantly due to differences in soil physical-chemical features.     

哈尼梯田生态系统土壤微生物量碳的影响因素

土壤微生物量碳（MBC,Microbial Biomass Carbon）是土壤微生物量的重要组成部分,也是土壤肥力变化的重要指标之一。哈尼梯田肥沃的土壤对哈尼梯田生态系统的维持与循环起到重要作用。以哈尼梯田水源区（乔木林、灌木林、荒草地）和梯田为研究对象,采用氯仿熏蒸法测定了4种不同土地利用类型0-20、20-40、40-60 cm 3个土层的土壤MBC,并分析了其与季节变化、地上植被及土壤理化性质之间的关系。结果表明：4种土地利用类型土壤MBC 3个土层皆以乔木林最高,其次是灌木林、荒草地、梯田,且4种土地利用类型土壤MBC含量都随土层深度的增加而减少,其中乔木林0-20 cm土层土壤MBC含量是40-60 cm土层的3.19倍。4种土地利用类型土壤MBC含量均具有明显的季节变化,总体呈"夏季偏高冬季偏低"的变化模式。相关分析表明,不同土地利用类型地上植被的多样性指数、盖度、优势种高度、枯落物层厚度与每一土层土壤MBC都具有很强的相互关系。土壤MBC与土壤有机碳和土壤孔隙度呈正相关性,与土壤容重呈负相关性。植被生长情况、土壤有机碳和孔隙度含量及季节变化是导致不同土地利用类型土壤微生物量碳差异的主要因素。     

养分管理对农田土壤微生物量的影响

土壤微生物与土壤质量、健康、植物的生产力和农业的可持续发展密切相关。任何对土壤中微生物的扰动都可能影响土壤的长期生产力,并可能产生严重后果。大量研究结果表明,肥料类型、施肥处理年限长短、施肥水平高低及施肥措施都会造成土壤成分的变化,进而影响土壤中微生物的生长以及繁殖。简要介绍了微生物量的几种测定方法,综述了各种养分管理措施对农田生态系统中土壤微生物量的影响,从而了解土壤微生物因人类对土壤的利用而发生的变化,以期为农业的可持续发展和生态环境的保护提供理论依据。     

Effects of Elevated Atmospheric CO2 on Soil Microbial Biomass, Activity, and Diversity in a Chaparral Ecosystem

This study reports the effects of long-term elevated atmospheric CO₂ on root production and microbial activity, biomass, and diversity in a chaparral ecosystem in southern California. The free air CO₂ enrichment (FACE) ring was located in a stand dominated by the woody shrub Adenostoma fasciculatum. Between 1995 and 2003, the FACE ring maintained an average daytime atmospheric CO₂ concentration of 550 ppm. During the last two years of operation, observations were made on soil cores collected from the FACE ring and adjacent areas of chaparral with ambient CO₂ levels. Root biomass roughly doubled in the FACE plot. Microbial biomass and activity were related to soil organic matter (OM) content, and so analysis of covariance was used to detect CO₂ effects while controlling for variation across the landscape. Extracellular enzymatic activity (cellulase and amylase) and microbial biomass C (chloroform fumigation-extraction) increased more rapidly with OM in the FACE plot than in controls, but glucose substrate-induced respiration (SIR) rates did not. The metabolic quotient (field respiration over potential respiration) was significantly higher in FACE samples, possibly indicating that microbial respiration was less C limited under high CO₂. The treatments also differed in the ratio of SIR to microbial biomass C, indicating a metabolic difference between the microbial communities. Bacterial diversity, described by 16S rRNA clone libraries, was unaffected by the CO₂ treatment, but fungal biomass was stimulated. Furthermore, fungal biomass was correlated with cellulase and amylase activities, indicating that fungi were responsible for the stimulation of enzymatic activity in the FACE treatment.     

地膜覆盖玉米对土壤微生物量的影响

通过田间小区试验,对不同施肥条件下黄土塬区地膜覆盖栽培玉米与裸地种植玉米各生长期土壤微生物生物量C、N,P进行了研究,其结果表明：地膜覆盖栽培各生长期玉米地的微生物量C均低于裸地种植玉米地,微生物量N与C的趋势基本一致,其中苗期表现最明显;而微生物量P有所不同,拔节期地膜覆盖玉米地的微生物量P明显低于裸地种植玉米地,抽雄期则是前者明显高于后者。研究表明地膜覆盖种植玉米对土壤微生物量C,N,P产生重要影响,其影响程度与作物生育期有关。     

荒漠草原3种典型群落类型的土壤微生物量碳氮研究

采用氯仿熏蒸-浸提法,以宁夏盐池荒漠草原3种典型群落(柠条、沙蒿、短花针茅)类型为研究对象,分析了不同生境(冠下、丛间)和不同土层间(0~5、5~10、10~15cm)土壤理化性质及微生物量——微生物量碳(MBC)和微生物量氮(MBN)的变化特征。结果表明:(1)3种群落土壤微生物量变化差异较大,柠条、沙蒿和短花针茅群落土壤MBC含量分别为77.00~393.18、17.27~221.71和81.05~173.37mg/kg,MBN含量分别为7.59~64.81、1.43~13.95和4.25~22.13mg/kg,MBC和MBN含量均表现为:冠下丛间,且随土层深度的增加而降低,有明显的"沃岛效应"。(2)群落类型对土壤微生物量碳氮含量的变化有显著影响,3种典型群落类型下土壤微生物量熵(qMB)、碳氮比(C/N)、微生物量碳氮比(MBC/MBN)分别在0.76~4.10、15.02~52.50、5.34~23.07范围内变化,其比值在不同生境和不同土层深度的分布特征有明显差异。(3)3种典型群落类型的土壤MBC与SOC、MBN、qMB具有显著相关关系,土壤C/N与MBC/MBN呈显著正相关关系,表明土壤MBC、MBN具有一定的生物学指示特性,可以作为评价土壤质量的生物学指标。     

Physical and Chemical Correlates of Microbial Activity and Biomass in Composting Municipal Sewage Sludge

Various physical and chemical parameters were monitored to evaluate their influence on the microbial communities present in composting municipal sewage sludge. Temperature, moisture content, depth, pH, protein content, total nitrogen, total carbon, lipid phosphate biomass, and the rates of microbial incorporation of substrates into lipids were measured at several times throughout the 17- to 19-day composting runs. Temperature was found to have the most consistent and dramatic effect on microbial activity and biomass. When temperatures exceeded 55 to 60°C, microbial activity fell dramatically, usually by more than 1 order of magnitude. Microbial activity was generally greatest in samples taken from the 35 to 50°C areas of the composting piles. Changes in the composition of the compost over time included increased pH, increased protein content, and decreased total organic content. The changes in these parameters appeared to reflect the microbial activity and biomass present. The results of this study indicate that the rate of composting may best be optimized by controlling the composting temperatures, provided that the other parameters fall within reasonable limits in the starting material.     

Restoring Soil Ecosystems and Biomass Production of Arundo donax L. under Microbial Communities-Depleted Soil

In recent years, giant reed (Arundo donax L) has received considerable attention as a promising plant for energy production. Giant reed is able to grow in a range of environments, including wetlands and marginal soils, and has shown promise in phytoremediation efforts. A pot experiment was carried out to investigate the ability of giant reed to restore ecosystems of different soils, including bauxite-derived red mud-amended soil and pure red mud (red mud—a waste generated by the Bayer process in the aluminum industry—is strongly alkaline and has a high salt content and electrical conductivity (EC) dominated by sodium). Samples were exposed to high temperatures, which simulate the effects of bushfires. Selected soil properties that were measured included soil dehydrogenase, alkaline phosphatase, urease and catalase activities, soil organic carbon, soil pH, EC, available soil macronutrients NPK, and above- and below-ground plant biomass yield. The results showed that giant reed reduced EC in all autoclaved soils and red mud-contaminated soils by 24–82 %. Significantly, available N was increased, and a slight increase was recorded for available K. The presence of giant reed enhanced the soils’ enzyme activities to recover in all tested autoclaved soils and red mud-contaminated soils; specifically, dehydrogenase activity increased by 262 and 705 % in non-autoclaved and autoclaved soils, respectively, and urease and catalase activities increased by 591 and 385 % in autoclaved soils, respectively. Total bacterial and fungal counts were higher in autoclaved soils than non-autoclaved soils after cultivating giant reed for 12 weeks. Autoclaved soils enabled higher biomass production for giant reed than non-autoclaved soils. These results demonstrate that giant reed is not only able to survive on soil that has lost its microbial community as a result of heat, but can also yield significant amounts of biomass while assisting recovering soil ecosystems after bushfires.     

Microbial Biomass Estimation

ABSTRACT

The development of a fully automated on-line monitoring and control system is very important in bioprocesses. One of the most important parameters in these processes is biomass. This review discusses different methods for biomass quantification. A general definition of biomass and biovolume are presented. Interesting concepts about active but not culturable cells considerations are included as well as concepts that must be taken into account when selecting biomass quantification technology. Chemical methods have had few applications in biomass measurement to date; however, bioluminescence can selectively enumerate viable cells. Photometric methods including fluorescence and scattered light measurements are presented. Reference methods including dry and wet weight, viable counts and direct counts are discussed, as well as the physical methods of flow cytometry, impedancimetric and dielectric techniques.     

复合微生态菌剂对黄瓜根际土壤微生物数量及酶活的影响

采用盆栽试验的方法,研究黄瓜移苗时施入复合微生态菌剂对黄瓜不同生育时期根际土壤中微生物数量和土壤酶活动态变化的影响,结果显示复合微生态菌剂施入前期可提高土壤中细菌和放线菌的数量,随生育时期的延长效果变弱,于生育后期可有效降低真菌和尖孢镰刀菌的数量;复合微生态菌剂处理可提高土壤脲酶、过氧化氢酶、蔗糖酶和中性磷酸酶的活性,但随生育时期的延长,对中性磷酸酶和脲酶的效果减弱。可见复合土壤微生态菌剂的施入应该于适宜时期补施,才能保证其积极的功效。     

Variation in Microbial Activity in Histosols and Its Relationship to Soil Moisture

Microbial biomass, dehydrogenase activity, carbon metabolism, and aerobic bacterial populations were examined in cropped and fallow Pahokee muck (a lithic medisaprist) of the Florida Everglades. Dehydrogenase activity was two- to sevenfold greater in soil cropped to St. Augustinegrass (Stenotaphrum secundatum (Walt) Kuntz) compared with uncropped soil, whereas biomass ranged from equivalence in the two soils to a threefold stimulation in the cropped soil. Biomass in soil cropped to sugarcane (Saccharum spp. L) approximated that from the grass field, whereas dehydrogenase activities of the cane soil were nearly equivalent to those of the fallow soil. Microbial biomass, dehydrogenase activity, aerobic bacterial populations, and salicylate oxidation rates all correlated with soil moisture levels. These data indicate that within the moisture ranges detected in the surface soils, increased moisture stimulated microbial activity, whereas within the soil profile where moisture ranges reached saturation, increased moisture inhibited aerobic activities and stimulated anaerobic processes.     

Seasonal and Diel Variability in Dissolved DNA and in Microbial Biomass and Activity in a Subtropical Estuary

Dissolved DNA and microbial biomass and activity parameters were measured over a 15-month period at three stations along a salinity gradient in Tampa Bay, Fla. Dissolved DNA showed seasonal variation, with minimal values in December and January and maximal values in summer months (July and August). This pattern of seasonal variation followed that of particulate DNA and water temperature and did not correlate with bacterioplankton (direct counts and [³H]thymidine incorporation) or phytoplankton (chlorophyll a and ¹⁴CO₂ fixation) biomass and activity. Microautotrophic populations showed maxima in the spring and fall, whereas microheterotrophic activity was greatest in late summer (September). Both autotrophic and heterotrophic microbial activity was greatest at the high estuarine (low salinity) station and lowest at the mouth of the bay (high salinity station), irrespective of season. Dissolved DNA carbon and phosphorus constituted 0.11 ± 0.05% of the dissolved organic carbon and 6.6 ± 6.5% of the dissolved organic phosphorus, respectively. Strong diel periodicity was noted in dissolved DNA and in microbial activity in Bayboro Harbor during the dry season. A noon maximum in primary productivity was followed by an 8 p.m. maximum in heterotrophic activity and a midnight maximum in dissolved DNA. This diel periodicity was less pronounced in the wet season, when microbial parameters were strongly influenced by episodic inputs of freshwater. These results suggest that seasonal and diel production of dissolved DNA is driven by primary production, either through direct DNA release by phytoplankton, or more likely, through growth of bacterioplankton on phytoplankton exudates, followed by excretion and lysis.     

Microbial Activity in Organic Soils as Affected by Soil Depth and Crop

The microbial activity of Pahokee muck, a lithic medisaprist, and the effect of various environmental factors, such as position in the profile and type of plant cover, were examined. Catabolic activity for [7-¹⁴C]salicylic acid, [1,4-¹⁴C]succinate, and [1,2-¹⁴C]acetate remained reasonably constant in surface (0 to 10 cm) soil samples from a fallow (bare) field from late in the wet season (May to September) through January. Late in January, the microbial activity toward all three compounds decreased approximately 50%. The microbial activity of the soil decreased with increasing depth of soil. Salicylate catabolism was the most sensitive to increasing moisture deep in the soil profile. At the end of the wet season, a 90% decrease in activity between the surface and the 60- to 70-cm depth occurred. Catabolism of acetate and succinate decreased approximately 75% in the same samples. Little effect of crop was observed. Variation in the microbial activity, as measured by the catabolism of labeled acetate, salicylate, or succinate, was not significant between a sugarcane (Saccharum officinarum L.) field and a fallow field. The activity with acetate was insignificantly different in a St. Augustine grass [Stenotaphrum secundatum (Walt) Kuntz] field, whereas the catabolism of the remaining substrates was elevated in the grass field. These results indicate that the total carbon evolved from the different levels of the soil profile by the microbial community oxidizing the soil organic matter decreased as the depth of the soil column increased. However, correction of the amount of carbon yielded at each level for the bulk density of that level reveals that the microbial contribution to the soil subsidence is approximately equivalent throughout the soil profile above the water table.     

熏蒸法测定土壤微生物量碳的改进

自从Ｊｅｎｋｉｎｓｏｎ和Ｐｏｗｌｓｏｎ［１］创造熏蒸培养方法测定土壤微生物量碳，发展到用多种方法来测定土壤微生物量，如土壤ＡＴＰ含量分析方法［２］，基质诱导呼吸法［３］，精氨酸氨化法［４］，熏蒸浸提法［５］，脂肪酸、ＤＮＡ、ＲＮＡ等微生物细胞成分分析...     

Differences of Soil Microbial Biomass and Nitrogen Transformation under Two Forest Types in Central Germany

In order to observe the tree species effect on soil N status, soil microbial biomass C and N (C_mic, N_mic), potential N mineralization and potential nitrification (under laboratory incubation conditions, 22 °C) in different subhorizons (LOf₁, Of₂, Oh and mineral soil at 0–10 cm depth) were determined at three forest sites in central Germany. At each site, two contrasting stands (Beech, Norway spruce or Scots pine) were selected, where the initial soil conditions were similar. Three sampling dates that represented different stages of tree growth were selected: growing season - August, dormant season - November, after budbreak – April. In organic layers, C_mic-to-total C (C_t) ratios under beech and under conifer were 0.72–4.74% and 0.34–2.11%, respectively. N_mic-to-total N (N_t) ratios were 2.47–11.61% and 0.71–5.77%, respectively. Both concentrations of C_mic and N_mic were significantly affected by the stand type and sampling time. Potential N mineralization rates, ranging from 3.7 to 19.7 mg N kg⁻¹ d⁻¹, showed no clear pattern in relation to stand type. However, potential nitrification rates were mostly significantly higher under beech than under contrasting conifer. In mineral soils, concentrations of C_mic and N_mic showed a clear temporal pattern in the order: August>November>April. The average N_mic and N_mic-to-N_t were higher in soils from beech than conifer, while C_mic and C_mic-to-C_t ratios were similar between the two forest types. In organic layers, the highest values of C_mic-to-N_mic ratio and C_mic were found in November samples, especially under beech. By contrast, in mineral soils the highest value of C_mic-to-N_mic ratios were found in April samples, and at that time the C_mic concentrations were the lowest, especially under conifer. These results revealed the differences in microbial growth form and survival strategy associated with different tree species and soil layers.     

Phospholipid Fatty Acid Composition, Biomass, and Activity of Microbial Communities from Two Soil Types Experimentally Exposed to Different Heavy Metals

The phospholipid fatty acid (PLFA) pattern was analyzed in a forest humus and in an arable soil experimentally polluted with Cd, Cu, Ni, Pb, or Zn at different concentrations. In both soil types, there were gradual changes in the PLFA patterns for the different levels of metal contamination. The changes in the forest soil were similar irrespective of which metal was used, while in the arable soil the changes due to Cu contamination differed from those due to the other metals. Several PLFAs reacted similarly to the metal amendments in the two soil types, while others showed different responses. In both soils, the metal pollution resulted in a decrease in the iso-branched PLFAs i15:0 and i17:0 and in the monounsaturated 16:1ω5 and 16:1ω7c fatty acids, while increases were found for i16:0, the branched br17:0 and br18:0, and the cyclopropane cy17:0 fatty acids. In the forest soil, the methyl branched PLFAs 10Me16:0, 10Me17:0, and 10Me18:0 increased in metal-polluted soils, indicating an increase in actinomycetes, while in the arable soil a decrease was found for 10Me16:0 and 10Me18:0 in response to most metals. The bacterial PLFAs 15:0 and 17:0 increased in all metal-contaminated samples in the arable soil, while they were unaffected in the forest soil. Fatty acid 18:2ω6, which is considered to be predominantly of fungal origin, increased in the arable soil, except in the Cu-amended samples, in which it decreased instead. Effects on the PLFA patterns were found at levels of metal contamination similar to or lower than those at which effects on ATP content, soil respiration, or total amount of PLFAs had occurred.     

Potential of Sonchus Arvensis for the Phytoremediation of Lead-Contaminated Soil

Sonchus arvensis is one of the pioneer plant species that were found in the abandoned Bo Ngam Pb mine in Thailand. S. arvensis was collected from three sites. The highest Pb shoot concentration was 9317 mg kg^?1 and the highest translocation factor (TF) and bioaccumulation factor (BF) values were 2.5 and 6.0, respectively. To investigate Pb uptake capacity of S. arvensis, a hydroponic experiment was performed for 15 d. S. arvensis exposed to 5 mg L^?1 Pb solution had the highest Pb shoot accumulation (849 mg kg^?1). In a pot study, S. arvensis was grown in Pb mine soils amended with organic and inorganic fertilizers for 2 mo. The addition of organic fertilizer to the soil increased plant dry biomass sharply. All treatments with ethylene-diamine-tetra-acetic acid (EDTA) had Pb accumulation in shoots greater than 1000 mg kg^?1 and the highest Pb shoot accumulation was found in S. arvensis grown in soil amended with organic fertilizer and EDTA (1397 mg kg^?1). In a field trial study, S. arvensis was grown at three sites in the mine area for 6 mo. S. arvensis could tolerate a total Pb of 100,000 mg kg^?1 in the soil and accumulated Pb in the shoots up to 3664 mg kg^?1 with high TF (2.19) and BF (2.38) values. These results suggest that S. arvensis is a good candidate for Pb phytoremediation.     

Heterotrophic Soil Respiration in Relation to Environmental Factors and Microbial Biomass in Two Wet Tropical Forests

We examined the correlation between fungal and bacterial biomass, abiotic factors such as soil moisture, carbon in the light soil fraction and soil nitrogen to a depth of 0–25 cm and heterotrophic soil respiration using a trenching technique – in a secondary forest (Myrcia splendens, Miconia prasina and Casearia arborea) and a pine (Pinus caribeae) plantation in the Luquillo Experimental Forest in Puerto Rico. Soil respiration was significantly reduced where roots were excluded for 7 years in both the secondary forest and the pine plantation. Microbial biomass was also significantly reduced in the root exclusion plots. In root exclusion treatment, total fungal biomass was on average 31 and 65% lower than the control plots in the pine plantation and the secondary forest, respectively, but the total bacterial biomass was 24 and 8.3% lower than the control plots in the pine plantation and the secondary forest, respectively. Heterotrophic soil respiration was positively correlated with fungal biomass (R²=0.63, R²=0.39), bacterial biomass (R²=0.16, R²=0.45), soil moisture (R²=0.41, R²=0.56), carbon in light fraction (R²=0.45, R²=0.39) and total nitrogen (R²=0.69, R²=0.67) in the pine plantation and the secondary forest, respectively. The regression analysis suggested that fungal biomass might have a greater influence on heterotrophic soil respiration in the pine plantation, while the bacterial biomass might have a greater influence in the secondary forest. Heterotrophic soil respiration was more sensitive to total N than to carbon in the light fraction, and soil moisture was a major factor influencing heterotrophic soil respiration in these forests where temperature is high and relatively invariable.