Soil respiration and carbon balance of gray forest soils as affected by land use

 Soil respiration was measured by closed chamber and gradient methods in soils under forest, sown meadow and crops. Annual total soil respiration determined with the closed chamber method ranged from 180 to 642 g CO₂-C m^–2 year^–1 and from 145 to 382 g CO₂-C m^–2 year^–1 determined with the CO₂ profile method. Soil respiration increased in the order: cropland<sown meadow<forest. The C balance calculated as the difference between net primary production (sink) and respiration of heterotrophs (source) suggested an equilibrium between the input and output of C in the cropland, and sequestration of 135 and 387 g CO₂-C m^–2 year^–1 in the forest and meadow, respectively. Received: 1 December 1997     

Soil loss and soil water content affected by land levelling in Penedès vineyards,NE Spain

This paper analyses the differences in soil moisture, runoff and sediment concentration resulting from land levelling works carried out before new vineyard establishment in a reference wine region of NE Spain. In low disturbed soils, low differences in soil moisture were observed, while in high disturbed soils, soil moisture and water infiltration of the surface were always lower than in the low disturbed ones, while soil sealing was higher in high disturbed than in the low disturbed soils. Differences in runoff and sediment concentrations were also observed. The most disturbed plot showed a higher sediment concentration in runoff, which together with higher runoff volumes gave higher erosion rates and soil losses than the low disturbed one. The differences within the most disturbed soils were high after high intensity rainfall events, while no significant variations were observed in the least disturbed ones.     

省域土壤有机碳空间分布的主控因子——土壤类型与土地利用比较

基于河北省第二次全国土壤普查数据,运用方差分析和回归分析对比了河北省土壤类型和一级土地利用类型对0～20 cm深土壤有机碳空间分布的影响,探讨了省域土壤有机碳空间分布的主控因子。研究结果表明,土壤类型和土地利用是河北省表层土壤有机碳密度空间分布的重要影响因子。其中土壤类型对土壤有机碳密度空间分布的影响与土壤分类级别相关,土壤分类级别越低,对土壤有机碳密度空间变异的反映能力越大。与土壤类型相比,土地利用对表层土壤有机碳密度空间分异的解释能力要大于土类,但小于亚类和土属。为此,在省域尺度对土壤有机碳密度进行区域预测和估算时应将土地利用和土壤类型结合起来作为土壤有机碳空间分布的主控因子,优先考虑土地利用后,在相同土地利用类型内再尽量以低级土壤分类进行空间预测或估算。     

Soil organic carbon and nutrients in smallholding land uses in southern Ethiopia

This study assessed the soil organic C (SOC) and soil nutrients in smallholding home garden, woodlot, grazing land, and cropland at two soil depths and two sites in Wolaita Zone, southern Ethiopia. The results showed that soil properties were significantly influenced by land use. The home garden had significantly higher (p < 0.05) SOC and soil nutrients when compared to the cropland. When the home garden was compared to the woodlot and grazing land uses, it had significantly higher (p < 0.05) values except in SOC, total N (TN), cation exchange capacity (CEC), and exchangeable Ca. Cropland, in comparison with grazing land and woodlot, had a non‐significant difference except TN. The SOC stock (0–40 cm) in the home garden, woodlot, grazing land and cropland was 79.5, 68.0, 65.0, and 58.1 Mg ha^?1, respectively. Home garden significantly differed (p ≤ 0.05) in SOC only from cropland, and this was attributed not only to the relatively higher organic input in the home garden but also to the little organic matter input and frequently tillage of the cropland. The similar SOC among the home garden, woodlot and grazing lands may imply that the balance between inputs and outputs could be nearly similar for the land uses. Soil TN and CEC had a nearly similar pattern of difference as in SOC among the land uses because of their close relationship with SOC. In general, the land use influence on soil nutrients can be in the order: home garden > wood land ≈ grazing land ≈ cropland, with home garden showing the least difference from the woodlot and the greatest from the cropland. In the agroecosystem, in general, the influence of smallholding home garden on SOC and soil nutrient was marginally different from Eucalyptus woodlot and grazing lands but evidently different from cropland.     

Soil organic carbon distribution in relation to land use and its storage in a small watershed of the Loess Plateau, China

Soil organic carbon (SOC) is an important component in agricultural soil, and its stock is a major part of global carbon stocks. Estimating the SOC distribution and storage is important for improving soil quality and SOC sequestration. This study evaluated the SOC distribution different land uses and estimated the SOC storage by classifying the study area by land use in a small watershed on the Loess Plateau. The results showed that the SOC content and density were affected by land use. The SOC content for shrubland and natural grassland was significantly higher than for other land uses, and cropland had the lowest SOC content. The effect of land use on the SOC content was more significant in the 0-10 cm soil layer than in other soil layers. For every type of land use, the SOC content decreased with soil depth. The highest SOC density (0-60 cm) in the study area was found in shrublandII (Hippophae rhamnoides), and the other land uses decreased in the SOC density as follows: natural grassland > shrublandI (Caragana korshinskii) > abandoned cropland > orchard > level ground cropland > terrace cropland > artificial grassland. Shrubland and natural grassland were the most efficient types for SOC sequestration, followed by abandoned cropland. The SOC stock (0-60 cm) in this study was 23,584.77 t with a mean SOC density of 4.64 (0-60 cm).     

Soil organic matter quantity and quality in mountain soils of the Alay Range, Kyrgyzia, affected by land use change

 Changes in soil management practices influence the amount, quality and turnover of soil organic matter (SOM). Our objective was to study the effects of deforestation followed by pasture establishment on SOM quantity, quality and turnover in mountain soils of the Sui Checti valley in the Alay Range, Kyrgyzia. This objective was approached by analysis of total organic C (TOC), N, lignin-derived phenols, and neutral sugars in soil samples and primary particle-size soil fractions. Pasture installation led to a loss of about 30% TOC compared with the native Juniperus turkestanica forests. The pasture soils accumulated about 20% N, due to inputs via animal excrement. A change in land use from forest to pasture mainly affected the SOM bound to the silt fraction; there was more microbial decomposition in the pasture than in the forest silt fraction, as indicated by lower yields of lignin and carbohydrates, and also by a more advanced oxidative lignin side-chain oxidation and higher values of plant : microbial sugar ratios. The ratio of arabinose : xylose was indicative of the removal of carbohydrates when the original forest was replaced by pasture, and we conclude that this can be used as an indicator of deforestation. The accumulation of lignin and its low humification within the forest floor could be due to the extremely cold winter and dry summer climate. Received: 10 March 1999     

Regional simulation of long-term organic carbon stock changes in cropland soils using the DNDC model: 2. Scenario analysis of management options

The development of successful agricultural policies in response to the Kyoto Protocol is aided by the identification of regions where the effects of soil organic carbon (SOC) sequestration measures can be maximized. We describe a modelling approach which incorporates a spatial analysis of the results from regional simulation under different management alternatives. SOC stock changes in Flemish cropland soils, simulated with the DNDC model, were previously fitted to a large data set of SOC measurements for the period 1990–2000. Using the results of this study, simulations with DNDC of SOC stock changes during the period 2006–2012 including the Kyoto commitment period were carried out at the community level for a business‐as‐usual (BAU) scenario and seven alternative agricultural management options for SOC sequestration. The baseline SOC stock decreased during that period by 0.15 t OC ha⁻¹ year⁻¹ compared with 0.48 t OC ha⁻¹ year⁻¹ in the 1990s. All alternative scenarios resulted in net SOC storage compared with the BAU scenario, but none of the individual scenarios were able to increase the average absolute SOC stock. Overall, spatial variability in SOC storage for the selected management options was strongly dependent on the current distribution of crops and associated management. The modelling approach used in this study provides a case study in regional scale modelling of SOC sequestration and is applicable to other regions in Europe with comparable intensive agriculture.     

Estimates of carbon stock changes in Belgian cropland

Abstract. Article 3.4 of the Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere by improved management of agricultural soils. To make use of this possibility, a good estimate of soil organic carbon (SOC) stocks and baseline emissions (in 1990) are crucial factors. Over 210 000 topsoil (0–24 cm) measurements have been made in Belgian cropland in the period 1989–1999, which are available for seven different agro-pedological regions and for three periods (1989–91, 1992–95, 1996–99). We used this extensive SOC data set to estimate SOC stocks and fluxes in Belgian cropland. The measurements of SOC were extrapolated to 1 m depth using an exponential SOC depth distribution model, based on another large data set of over 5184 fully described soil profiles on Belgian cropland made during the National Soil Survey. The SOC data were combined with cropland area figures to calculate SOC stocks to 1 m depth. The 1990 baseline SOC flux of Belgian cropland was then obtained using two different calculation methods, which each yielded similar results and showed that SOC stocks were decreasing in the 1990s at a mean rate of 608 kton OC yr⁻¹. Consequently, a large part of the Belgian cropland acted as a net source of CO₂ emissions during the period 1989–1999.     

不同土地利用和施肥方式下黑土碳平衡的研究

本研究进行了东北黑土不同土地利用(草地GL、裸地BL)与农田施肥管理方式(无肥NF、化肥NPK及化肥+有机肥处理NPKOM)下草本植物与作物净初级生产力(NPP)和净生态系统生产力(NEP)以及土壤碳排放的估算,目的是揭示自然与农田生态系统及经过土壤大气界面的碳收支平衡。土壤生长季碳排放总量(Rgs)、全年碳排放总量(Rann)以及全年微生物异养呼吸总量(Rm)以如下顺序递减:NPKOMGLNPKNFBL,5个处理之间存在显著差异(P0.05),但是草地与农田化肥+有机肥处理之间差异不显著(P0.05)。净初级生产力表现:GLNPKOMNPKNFBL,5个处理之间存在显著差异(P0.05)。草地总生物量及固碳量显著高于农田各处理(P0.05),草地NPP总量与农田各处理相比增加32%~96%。化肥+有机肥处理和化肥处理NPP总量比无肥处理高46%和49%。草地与农田的NEP均为正值,表明草地与农田在生态系统尺度上均是大气CO2的"汇"。对大气土壤界面碳平衡的分析表明,当前管理方式下,草地土壤是大气碳库的净汇,而裸地和农田土壤是净源。农田不同施肥处理土壤有机碳含量呈下降趋势,但增加有机肥的投入可增强土壤的固碳容量,达到新的碳平衡。     

Organic carbon in soils of Germany: Status quo and the need for new data to evaluate potentials and trends of soil carbon sequestration

Uncertainties in estimates of soil carbon (C) stocks and sequestration result from major gaps in knowledge of C storage in soils, land‐use history, the variability of field measurements, and different analytical approaches applied. In addition, there is a lack of long‐term datasets from relevant land‐use systems. As in many European countries, a national database on soil organic carbon (SOC) including all relevant information for the determination of soil C stocks is likewise missing in Germany. In this paper, we summarize and evaluate the present state of knowledge on organic‐C contents/pools in soils of Germany and discuss the need for the acquisition and access to new data on soil organic carbon. Despite the number of agricultural sites under permanent soil monitoring, regional surveys on SOC, comprehensive ecosystem studies, and long‐term field experiments, there is a striking lack of data in Germany particularly with regard to agricultural soils. Apart from a missing standardization of methods and homogeneous baseline values, the implementation of a periodic, nation‐wide soil inventory on agricultural soils is required in order to simultaneously record information on land use, land‐use change, and agricultural practice. In contrast, the existing national inventory of forest soils provides information on C‐stock changes in forest soils, although there is some concern with regard to the representativeness of the sampling design to adequately address the problem of spatial heterogeneity and temporal variability. It is concluded that the lack of comprehensiveness, completeness, actuality, data harmonization, and standardized sampling procedures will further prevent the establishment of a SOC database in Germany with regard to the monitoring of trends in soil C pools and fluxes and the assessment of long‐term C‐sequestration potentials of soils under different land use. A future soil inventory should represent the heterogeneity of organic matter through functionally different SOC pools, topsoil characteristics as well as content, pool, and flux data for the deeper mineral‐soil compartments.     

Soil carbon and nitrogen sequestration following the conversion of cropland to alfalfa forage land in northwest China

Soil C and N contents play a crucial role in sustaining soil quality and environmental quality. The conversion of annually cultivated land to forage grasses has potential to increase C and N sequestration. The objective of this study was to investigate the short-term changes in soil organic C (SOC) and N pools after annual crops were converted to alfalfa (Medicago sativa L. Algonguin) forage for 4 years. Soil from 24 sets of paired sites, alfalfa field versus adjacent cropland, were sampled at depths of 0–5, 5–10 and 10–20 cm. Total soil organic C and N, particulate organic matter (POM) C and N were determined. Organic C, total N, POM-C, and POM-N contents in the 0–5 cm layer were significantly greater in alfalfa field than in adjacent cropland. However, when the entire 0–20 cm layer was considered, there were significant differences in SOC, POM-C and POM-N but not in total N between alfalfa and crop soils. Also, greater differences in POM-C and POM-N were between the two land-use treatments than in SOC and total N were found. Across all sites, SOC and total N in the 0–20 cm profile averaged 22.1 Mg C ha⁻¹ and 2.3 Mg N ha⁻¹ for alfalfa soils, and 19.8 Mg C ha⁻¹and 2.2 Mg N ha⁻¹ for adjacent crop soils. Estimated C sequestration rate (0–20 cm) following crops to alfalfa conversions averaged 0.57 Mg C ha⁻¹ year⁻¹. Sandy soils have more significant C accumulation than silt loam soils after conversion. The result of this suggests that the soils studied have great C sequestration potential, and the conversion of crops to alfalfa should be widely used to sequester C and improve soil quality in this region.     

Regional simulation of long-term organic carbon stock changes in cropland soils using the DNDC model: 1. Large-scale model validation against a spatially explicit data set

Because of the large spatial and temporal variability of soil organic carbon (SOC) dynamics, a modelling approach is crucial in detailed regional analyses. Several estimates of regional scale SOC sequestration potential have been made using dynamic soil organic matter (SOM) models which have been linked to spatial databases contained within a Geographic Information System. In all these previous studies, a large‐scale model validation, which provides information on the general model performance for the study area under concern, was impossible because of lack of data. A data set of over 190 000 SOC measurements, grouped as means per community and covering the period 1989–2000 was available for Flanders in northern Belgium. In order to validate the DNDC model at a large spatial scale, we used this data set along with detailed pH, soil texture and crop areas which were all available at the municipality scale to simulate SOC stocks for the entire study area during the period 1990–2000. A minor adjustment of the initial distribution of SOC in the model's SOC pool was necessary to fit the simulated SOC stock changes to the measured decrease of −475 kg OC ha⁻¹ year⁻¹ (0–30 cm). Although DNDC was able to simulate the SOC stock changes well for the whole study area, the simulated decrease in the SOC stocks was overestimated for communities predominantly having sandy textures and underestimated for communities with silt loam to silt textures. This study also urges caution with the application of SOM models at regional scales after limited validation or calibration at the field scale as these do not guarantee good simulation of spatial variation in SOC changes.     

福建省不同耕地土壤和土地利用类型对“碳源/汇”的贡献差异研究

农田生态系统无论作为全球温室气体的“源”还是“汇”,均对大气CO2浓度的年际变化产生重要影响.以我国亚热带地区——福建省不同地理位置的闽侯县、浦城县、同安县和永定县为典型研究区,利用这4个县1982年23 869个样点和2008年12 521个样点实测数据建立的1∶5万土壤类型-土地利用方式数据库,分析了近30年来福建省不同土类、亚类、土属和土地利用方式耕地有机碳密度变化,并利用尺度上推的方法估算了全省两期耕地土壤有机碳储量.结果表明,近30年来福建省耕地总体上表现为弱的“碳汇”,土壤有机碳密度和储量分别上升了0.24 kg m-2和4.26 Tg,但不同土壤类型和土地利用方式在“碳汇/源”中的贡献程度差异很大.从土壤类型来看,紫色土、酸性紫色土和石灰泥田分别在土类、亚类和土属级别中的“碳汇”贡献最大,有机碳密度分别提高了0.63、0.63和1.25 kg m-2;而滨海盐土、滨海盐土和黄泥砂土则分别在土类、亚类和土属级别中的“碳源”贡献最大,有机碳密度分别下降了0.59、0.59和1.08 kg m-2.从土地利用方式来看,灌溉水田是全省最主要的“碳汇”,有机碳密度提高了0.27 kg m-2,而水浇地是全省最主要的“碳源”,有机碳密度下降了0.36 kg m-2.因此,在今后的福建省农田土壤有机碳管理政策中应重点考虑有机碳密度下降、面积较大的土壤类型及土地利用方式的有效管理.     

Effects of potato–grain rotations on soil erosion, carbon dynamics and properties of rangeland sandy soils

The potential for wind erosion in South Central Colorado is greatest in the spring, especially after harvesting of crops such as potato (Solanum tuberosum L.) that leave small amounts of crop residue in the surface after harvest. Therefore it is important to implement best management practices that reduce potential wind erosion and that we understand how cropping systems are impacting soil erosion, carbon dynamics, and properties of rangeland sandy soils. We evaluate the effects of cropping systems on soil physical and chemical properties of rangeland sandy soils. The cropping system included a small grain–potato rotation. An uncultivated rangeland site and three fields that two decades ago were converted from rangeland into cultivated center-pivot-irrigation-sprinkler fields were also sampled. Plant and soil samples were collected in the rangeland area and the three adjacent cultivated sites. The soils at these sites were classified as a Gunbarrel loamy sand (Mixed, frigid Typic Psammaquent). We found that for the rangeland site, soil where brush species were growing exhibited C sequestration and increases in soil organic matter (SOM) while the bare soil areas of the rangeland are losing significant amounts of fine particles, nutrients and soil organic carbon (SOM-C) mainly due to wind erosion. When we compared the cultivated sites to the uncultivated rangeland, we found that the SOM-C and soil organic matter nitrogen (SOM-N) increased with increases in crop residue returned into the soils. Our results showed that even with potato crops, which are high intensity cultivated cropping systems, we can maintain the SOM-C with a rotation of two small grain crops (all residue incorporated) and one potato crop, or potentially increase the average SOM-C with a rotation of four small grain crops (all residue incorporated) and one potato crop. Erosion losses of fine silt and clay particles were reduced with the inclusion of small grains. Small grains have the potential to contribute to the conservation of SOM and/or sequester SOM-C and SOM-N for these rangeland systems that have very low C content and that are also losing C from their bare soils areas (40%). Cultivation of these rangelands using rotations with at least two small grain crops can reduce erosion and maintain SOM-C and increasing the number of small grain crops grown successfully in rotation above two will potentially contribute to C and N sequestration as SOM and to the sequestration of macro- and micro-nutrients.     

Manuring and rotation effects on soil organic carbon concentration for different aggregate size fractions on two soils in northeastern Ohio, USA

Soil carbon (C) sequestration is important to the mitigation of increasing atmospheric concentration of CO₂. This study was conducted to assess soil aggregation and C concentration under different management practices. The effects of crop rotation, manure application and tillage were investigated for 0–5 and 5–10 cm depths on two silt loam soils (fine-loamy, mixed, active, mesic Aquic Fragiudalfs and fine-loamy, mixed, active, mesic Aeric Fragiadalf) in Geauga and Stark Counties, respectively, in northeastern Ohio, USA. Wet sieve analysis and gravity fractionation techniques were used to separate samples in aggregate and particle size groups, respectively. In the Stark County farms water stable aggregate (WSA) is higher in wooded (W) controls (WSA = 94.8%) than in cultivated soils with poultry manure (PM, 78.7%) and with chemical fertilizers (CF, 79.0%). Manure applications did not increase aggregation compared to unmanured soils. The C concentrations (%) within aggregates (C_agg) are higher in W than in cultivated soils (W = 5.82, PM = 2.11, CF = 1.96). Soil C (%) is enriched in the clay (W = 9.87, PM = 4.17, CF = 4.21) compared to silt (4.26, 1.04 and 0.98, respectively) and sand (0.93, 0.14 and 0.32, respectively) fractions. In the Geauga County farm, continuous corn (CC) with conventional tillage has lower WSA (83.1%) than soils with rotations (R) (93.9%), dairy manure (DM) application (93.2%) and no-till (NT) (91.1%). The C concentrations within macroaggregates (C_agg) were higher in W soils (4.84%) than in cultivated soils (ranging from 2.65 to 1.75%). The C (%) is enriched in clay (W = 8.56, CC = 4.18, R = 5.17, DM = 5.73, NT = 4.67) compared to silt (W = 2.35, CC = 0.90, R = 0.96, DM = 1.57, NT = 1.06) and sand (W = 0.44, CC = 0.33, R = 0.13, DM = 0.41, NT = 0.18). Cultivation decreased C concentration whereas reduced tillage, rotation and manure enhanced C concentration in soil.     

Total and mineralizable soil carbon as affected by tillage in the Argentinean Pampas

This study was carried out in experimental plots established at Marcos Juárez, in the Pampean Region (center of Argentina) on Typic Argiudolls, with high silt content. The aim of this work was to study the effects of two tillage systems (reduced tillage and no-tillage) on the amount of total organic C, potentially mineralizable C, C released by respiration, and C stock in the topsoil of a corn (Zea mays L.)–wheat (Triticum aestivum L.)/soybean (Glycine max L. Merr.)–soybean rotation. No-tillage showed C stock greater than reduced tillage only at 0–5 cm depth, but not at 0–20 cm, even though in situ respiration was lower. As a consequence, no tillage did not show a differential capacity for C sequestration in comparison with reduced tillage.     

Potential carbon stock in Japanese forest soils – simulated impact of forest management and climate change using the CENTURY model

Forest management and climate change may have a substantial impact on future soil organic carbon (SOC) stocks at the country scale. Potential SOC in Japanese forest soils was regionally estimated under nine forest managements and a climate change scenario using the CENTURY ecosystem model. Three rotations (30, 50, 100 yr) and three thinning regimes were tested: no‐thinning; 30% of the trees cut in the middle of the rotation (e.g. 15 year in a 30‐yr rotation) and thinned trees all left as litter or slash (ThinLef) and the trees from thinning removed from the forest (ThinRem). A climate change scenario was tested (ca. 3 °C increase in air temperature and 9% increase in precipitation). The model was run at 1 km resolution using climate, vegetation and soil databases. The estimated SOC stock ranged from 1600 to 1830 TgC (from 6800 to 7800 gC/m²), and the SOC stock was largest with the longest rotation and was largest under ThinLef with all three rotations. Despite an increase in net primary production, the SOC stock decreased by 5% under the climate change scenario.     

In situ and potential CO2 evolution from a Fluventic Ustochrept in southcentral Texas as affected by tillage and cropping intensity

Quality of agricultural soils is largely a function of soil organic matter. Tillage and crop management impact soil organic matter dynamics by modification of the soil environment and quantity and quality of C input. We investigated changes in pools and fluxes of soil organic C (SOC) during the ninth and tenth year of cropping with various intensities under conventional disk-and-bed tillage (CT) and no tillage (NT). Soil organic C to a depth of 0.2 m increased with cropping intensity as a result of greater C input and was 10% to 30% greater under NT than under CT. Sequestration of crop-derived C input into SOC was 22±2% under NT and 9±4% under CT (mean of cropping intensities ± standard deviation of cropping systems). Greater sequestration of SOC under NT was due to a lower rate of in situ soil CO₂ evolution than under CT (0.22±0.03 vs. 0.27±0.06 g CO₂–C g⁻¹ SOC yr⁻¹). Despite a similar labile pool of SOC under NT than under CT (1.1±0.1 vs. 1.0±0.1 g mineralizable C kg⁻¹ SOC d⁻¹), the ratio of in situ to potential CO₂ evolution was less under NT (0.56±0.03) than under CT (0.73±0.08), suggesting strong environmental controls on SOC turnover, such as temperature, moisture, and residue placement. Both increased C sequestration and a greater labile SOC pool were achieved in this low-SOC soil using NT and high-intensity cropping.     

Dominant bacteria in soils of Marble Point and Wright Valley, Victoria Land, Antarctica

A combination of culture-independent and culturing methods was used to assess the diversity of soil bacterial communities from four locations along 77 °S in Victoria Land, Antarctica. Soil samples were from the coast at Marble Point, in the Wright Valley from Bull Pass and near Lake Vanda, and from Mt. Fleming near the polar plateau. Total carbon and nitrogen, and water content of the soils were low, whereas total P was very high. The pH of the soils varied from extremely alkaline to slightly acid and electrical conductivity was medium to high on the coast and very high in inland soils from Bull Pass and Mt. Fleming. The average monthly air temperature was similar (−18 °C to −24 °C) at all the sites; however, in summer surface soil temperatures were >0 °C at Marble Point and in the Wright Valley for a total of 1100 and 1700 h, respectively. Marble Point soil had the most potential to support bacterial growth and activity with a mean total of 310 h per year when surface soils had a liquid volumetric soil moisture content >5%. Highest counts of culturable heterotrophs occurred in soil from Marble Point, whereas Mt. Fleming soil contained few organisms and had no liquid soil moisture recorded. Seven hundred and twenty-eight clones and 71 bacterial isolates were screened by restriction fragment length polymorphisms, and representatives of those dominant ribotypes that occurred more than 3 times were sequenced. The dominant ribotypes grouped within the bacterial divisions Bacteroidetes, Actinobacteria, Proteobacteria, Thermus-Deinococcus, Acidobacteria, Firmicutes and Cyanobacteria. The closest relatives of the amplicon library clones or cultured bacteria include the genera Hymenobacter, Gillisia, Arthrobacter, Rubrobacter, Friedmanniella, Deinococcus and Leptolyngbya. Many of the clones and bacteria were most similar to others from Antarctic sources, in particular a cyanobacterium-dominated cryptoendolithic community in Beacon sandstone. Some ribotypes were more prevalent in drier soils of the Wright Valley, including relatives of Deinococcus, Rubrobacter and clone FBP460 from Beacon sandstone. Bacterial communities from Marble Point soils were more diverse than those of the Wright Valley. Very few bacteria were isolated from Mt. Fleming soil.