Denitrification in undisturbed cores from a solodized solonetz B horizon

Summary An electrolytic respirometer was used to study the effects of oxygen, moisture and glucose on denitrification in undisturbed cores from a solodized solonetz B horizon. Under the experimental conditions, nitrous oxide present after 144 h was a reasonable index of total denitrification. Nitrous oxide evolution was positively correlated with moisture, quantity of added glucose, and negatively correlated with per cent oxygen. With glucose present, denitrification proceeded at high oxygen and moderate moisture levels, but was most rapid at low oxygen and high moisture. At low oxygen content, denitrification increased with increasing water content. In horizons with high potential denitrifying activity, denitrification could occur under field conditions at moderate aeration and moderately high moisture contents.This work was supported by the Australian Wheat Industry Research Council as part of a programme of investigation of nitrogen conservation in Australian wheat soils.Formerly holder of an Australian Wheat Industry Research Council Studentship, and Associate Professor, respectively, Department of Agronomy, University of New England, Armidale, New South Wales, Australia. The senior author is now with CSIRO, P.O. Box 21, Katherine, N.T. 5780, Australia.     

CO2 efflux from a Mediterranean semi-arid forest soil. II. Effects of soil fauna and surface stoniness

Many forest soils in the Mediterranean basin areshallow and contain high amounts of gravel in theorganic layers. Recent studies on soil organic matteraccumulation have shown high amounts of organic matteroccurring mainly in soils with high levels ofstoniness at the soil surface. The gravel layer mayaffect the microclimatic conditions of the soilsurface and probably the distribution and activity ofsoil fauna.In order to quantify the combined effects soil fauna(epigeic macrofauna and earthworms) and stoniness onthe release of soil CO₂, we performed a threefactor field experiment by using a series ofreconstructed soil profiles. Factors 1 and 2 consistedof the exclusion/presence of soil epigeic macrofaunaand earthworms, and factor 3 of the presence/absenceof a gravel layer intermingled with the H horizon. Weincubated ¹⁴C straw in the H horizon and carriedout three 40 mm rainfall simulations.Soil respiration primarily depended on the season. Theeffects of soil fauna were generally small and did notcoincide with periods of high faunal activity. Thelargest effects of both earthworms and soil epigeicfauna were found after wetting the soil in summer. Theeffects of the earthworms were concentrated in themineral soil while the effects of the epigeic faunawere concentrated in the H horizon and mainly arosetowards the end of the experiment. This suggests thatthe effects of epigeic fauna may have beenunderestimated due to the length of the experiment.The gravel layer increased the effect of faunaprobably by creating more favorable microclimaticconditions. The accumulation of organic matter insoils with high levels of stoniness cannot beexplained by the effect of gravel on soil microclimatenor by its effect on the activity of soil fauna.     

Soil Organic Carbon Content Decreases in Both Surface and Subsoil Mineral Horizons by Simulated Future Increases in Labile Carbon Inputs in a Temperate Coniferous Forest

Soils represent important pools of soil organic carbon (SOC) that can be greatly influenced by labile C inputs, which are expected to increase in future due to CO₂ enrichment of atmosphere and a concomitant rise in plant primary productivity. Studying effects of variable labile C inputs on SOC pool helps to understand how soils respond to global change. However, this knowledge is missing for coniferous forest soils despite being widespread throughout the northern temperate zone. We conducted a 7-month field manipulation experiment to study the effects of variable labile C inputs (simulated by additions of C₄ sucrose) on the C content in soil fractions and on microbial abundance in the organic (O), surface mineral (A), and subsoil mineral (B) horizons of a temperate coniferous forest soil. SOC in less-protected soil fractions and total organic C were substantially decreased by labile C additions that simulated future increases in C inputs. The SOC losses were comparable between the A and B horizon (40% vs. 30%). However, because sucrose availability estimated from its incorporation into soil fractions and microbial biomass sharply decreased with soil depth, the loss of C was higher in the B than in the A horizon when related to the amount of sucrose added. Utilization of sucrose was highest by fungi in the O horizon and by bacteria in the mineral soil horizons. The results indicate that future increases in labile C inputs to coniferous forest soils will cause rapid and substantial losses of SOC in both the surface and subsoil mineral horizons.

     

Persistence of Denitrifying Enzyme Activity in Dried Soils

The effects of air drying soil on denitrifying enzyme activity, denitrifier numbers, and rates of N gas loss from soil cores were measured. Only 29 and 16% of the initial denitrifying enzyme activity in fresh, near field capacity samples of Maury and Donerail soils, respectively, were lost after 7 days of air drying. The denitrifying activity of bacteria added to soil and activity recently formed in situ were not stable during drying. When dried and moist soil cores were irrigated, evolution of N gas began, and it maximized sooner in the dried cores. This suggests that the persistence of denitrifying enzymes permits accelerated denitrification when dried soils are remoistened. Enzyme activity increased significantly in these waterlogged cores, but fluctuations in enzyme activity were small compared with fluctuations in actual denitrification rate, and enzyme activities were always greater than denitrification rates. Apparent numbers of isolatable denitrifiers (most-probable-number counts) decreased more than enzyme activity as the soils were dried, but after the soils were rewetted, the extent of apparent growth was not consistently related to the magnitude of N loss. We hypothesize that activation-inactivation of existing enzymes by soil O₂ is of greater significance in transient denitrification events than is growth of denitrifiers or synthesis of new enzymes.     

Anthropogenic transformation of soil and vegetation resulting from afforestation in southern steppes

Recent data (2006–2008) on characteristics of the vegetation and soils of the solonetzic complex in areas with tree failures within the Volgograd-Elista-Cherkessk forest shelterbelt have been compared with those obtained prior to afforestation (1950). The results show that the vegetation and soils have changed profoundly. Solonetzic agrozems in tree failure sites have been occupied by herbaceous plant communities similar in composition to natural communities. Anthropogenically altered soils formed under forest plantations have no natural analogs. The initial strongly saline shallow (crusty) solonetz soils with a chloride-sulfate or sulfate-chloride composition of salts have transformed into slightly saline solonetzic and solonchakous agrozems with sodium sulfate salinity or with increased alkalinity in the middle of the soil profile and a dealkalized arable horizon.     

Possibility of existence and multiplication of Mycobacteria in the soil

The time of the survival of Mycobacterium bovis in the soil of pastures depended on the physicochemical composition and biological activity of the soil. In clay soils M. bovis retained their virulence for as long as 2 months (at the depth of 2 cm in high- and medium-posted solonetz) to 12 months (at the depth of 10 cm in crust solonetz). The M. bovis strains under study multiplied in soil extracts (the term of observation was 8 months). The cultures grown at 20-24 degrees C were found to have the prolonged exponential phase in comparison with that of the cultures grown at 37.5-38.5 degrees C. In the deep litter and the soil under it M. avium remained viable for 10 years.     

Snow vole (Chionomys nivalis Martins) affects the redistribution of soil organic matter and hormone‐like activity in the alpine ecosystem: ecological implications

In alpine environments, colonies of snow vole (Chionomys nivalis Martins) cause strong pedoturbation, which may affect humification process and soil organic matter (SOM) cycling, with repercussions on the hormone‐like activity of organics. We investigated the effect of snow vole pedoturbation on the chemical and spectroscopic features of soil organic fractions, and the potential hormone‐like activity of humic and fulvic acids (HA, FA). The study site was located on the high‐mountain environment of the Majella massif (central Italy). Pedoturbated and regular soils were morphologically described and characterized for pH and content of total organic carbon, total extractable carbon, HA, and FA. Both HA and FA were extracted and investigated using attenuated total reflectance/Fourier transform infrared (ATR/FTIR), nuclear magnetic resonance with high‐resolution magic angle spinning (HRMAS‐NMR), and ¹H‐¹³C heteronuclear single quantum coherence (HSQC). HA and FA were also tested for their auxin‐like and gibberellin‐like activities. Results provide evidences that bioturbated and regular soils contain a poorly decomposed SOM, but HA and FA with a well‐defined molecular structure. The HA and FA from both bioturbated and regular soils show a hormone‐like activity with a different allocation along the soil profile. In the regular soil, the highest auxin‐like activity was shown by HA and FA from Oe1 horizon, while gibberellin‐like activity was expressed by FA from Oe2 horizon. Burrowing activity determines a redistribution of organics throughout the profile with a relatively high auxin‐like activity in the FA from straw tunnel wall (STW) and gibberellin‐like activity in the HA from vole feces (VF). The relative high presence of carboxylic acids, amides, proteins, and amino acids in the FA from STW and the aromatic moieties in the HA from VF put evidences for their different behavior. The fact that snow vole activity has modified the chemical and biological properties of SOM in these soils otherwise considered governed only by low temperature has important ecological implications such as the preservation of soil fertility and vegetal biodiversity.     

Characterization of solid and dissolved carbon in a spruce-fir Spodosol

Organic substances are an integral part of the biogeochemistry of many elements in forest ecosystems. However, our understanding of the composition, chemistry, and reactions of these materials are incomplete and sometimes inconsistent. Therefore, we examined in detail dissolved organic carbon (DOC) in forest floor leachates over a two-year period (1992–1993), soil C, and DOC adsorption by a mineral soil to determine the relationship between soil solid and solution C characteristics in a spruce-fir ecosystem. The structural composition of DOC, DOC fractions (hydrophobic and hydrophilic acids, hydrophilic neutrals), and soil samples from the organic and mineral horizons were also analyzed using¹³C nuclear magnetic resonance (NMR) spectroscopy.Total DOC in forest floor leachates ranged from 7.8 to 13.8 mmol L^–1 with an average of 8.6 mmol L^–1. Concentrations were highest in September of both 1992 and 1993. Fractionation of the forest floor DOC indicated these solutions contained high organic acid contents that averaged 92% of the total DOC. Hydrophobic acids were also preferentially adsorbed by the B horizon. The¹³C NMR data suggested alkyl, carbohydrate, aromatic, and carboxylic C were the primary constituents for organic and mineral soils, DOC, and DOC fractions. Compositional changes of C were observed as aromatic and carbohydrate decreased, whereas alkyl, methoxy, and carbonyl moieties increased with depth. However, C composition changed little among the three organic layers based on the similarity of alkyl/carbohydrates ratios as determined from NMR area integration, suggesting that in this acid soil, decomposition proceeds rather slowly. Hydrophobic acids contained high contents of aromatic C, whereas hydrophilic acids were comprised primarily of carboxylic C. Hydrophilic neutrals were rich in carbohydrate C. Results indicated that these DOC fractions were unaltered during the isolation process. Carboxylic C groups appeared to dissolve easily and were probably the primary contributor to organic acidity in our organic dominate leachates. Results also suggested that DOC materials adsorbed on the B horizon underwent further biodegradation. Several seasonal patterns of C composition were observed in the forest floor leachates and DOC fractions collected between 1992 and 1993.Overall, the evidence from this study suggested that (i) DOC levels were mainly controlled by biological activity, (ii) forest floor DOC was comprised primarily of organic acids, (iii) contact of soil leachates with B horizon material affected DOC quantitatively and qualitatively, (iv) phenolic, carboxylic, and carbonyl C appeared to dissolve readily in the forest Oa horizon, (v) DOC materials adsorbed on the B horizon selectively underwent further decomposition, and (vi) C composition is a function of the extent of decomposition and DOC fractions.     

Rates of Decomposition Processes in Mountain Soils of the Sudeten as a Function of Edaphic-Climatic and Biotic Factors

The rate of grass litter decomposition was studied in soils of the Karkonosze Mountains of the Sudeten at different altitudes. Parallel structural-functional investigations of the soil animal population on the example of soil macrofauna were carried out and heavy metals were assayed in the soil at stationary plots to reveal the effects of both natural and anthropogenic factors on the soil biological activity. The recent contamination of soil in the Sudeten by heavy metals and sulfur does not affect the spatial distribution and abundance of the soil-dwelling invertebrates and the decomposition rates. The latter correlated to a high level of soil saprotroph activity. The activity of the decomposition processes depends on the soil content of organic matter, conditions of soil drainage, and the temperature of upper soil horizon.     

若尔盖高原湿地泥炭沼泽土亚硝酸盐还原酶（nirK）反硝化细菌群落结构分析

若尔盖泥炭湿地是世界少有的低纬度永久冻土湿地,具有高海拔、高紫外辐射、高有机质的特点。该区域N2O的排放量对全球气候变暖有重要影响。对若尔盖高原湿地泥炭沼泽土中的亚硝酸盐还原酶(nir K)反硝化细菌群落结构多样性进行分析,以期揭示该区域N2O释放的微生物调控机制。基于若尔盖高原湿地泥炭沼泽土的理化性质和反硝化活性(PDA),结合限制性酶切片段长度多态性(Restriction fragment length polymorphism,RFLP)技术、克隆文库及分子测序对该生态系统中的nir K反硝化细菌群落结构及多样性进行分析。反硝化活性测定结果显示:阿西地区麦溪地区分区地区,反硝化活性与土壤有机碳、总氮和丰富度呈显著正相关(P0.05)。Shannon-wiener多样性指数以阿西最高、分区最低。3个样品中共测序15条nir K基因代表序列,系统发育表明若尔盖高原湿地优势nir K反硝化菌群为变形门菌群。其中,阿西地区主要为α-变形菌门,麦溪地区主要为β-变形菌门,分区地区无法确定优势种群。冗余分析(Redundancy analysis,RDA)显示:有效钾和有效磷是影响nir K反硝化细菌群落结构的关键环境因子。本论文显示,若尔盖高原湿地存在着明显的反硝化作用,调控这些反硝化作用的nir K反硝化细菌多样性较高,且与土壤有效钾和有效磷密切相关。     

Impact of spruce forest and grass vegetation cover on soil micromorphology and hydraulic properties of organic matter horizon

Two organic matter horizons developed under a spruce forest and grass vegetation were chosen to demonstrate the impact of a different vegetation cover on the micromorphology, porous system and hydraulic properties of surface soils. Micromorphological studies showed that the decomposed organic material in the organic matter horizon under the grass vegetation was more compact compared to the decomposed organic material in the organic matter horizon under the spruce forest. The detected soil porous system in the organic matter horizon under the spruce forest consisted of two clusters of pores with different diameters that were highly connected within and between both clusters. The soil porous system in the organic matter horizon under the grass vegetation consisted of one cluster of pores with the larger diameters and isolated pores with the smaller diameter. The retention ability of the organic matter horizon under the grass vegetation was higher than the retention ability of the organic matter horizon under the spruce forest. Presented at the International Conference on Bioclimatology and Natural Hazards, Poľana nad Detvou, Slovakia, 17–20 September 2007.     

Effect of Dissemination of 2,4-Dichlorophenoxyacetic Acid (2,4-D) Degradation Plasmids on 2,4-D Degradation and on Bacterial Community Structure in Two Different Soil Horizons

Transfer of the 2,4-dichlorophenoxyacetic acid (2,4-D) degradation plasmids pEMT1 and pJP4 from an introduced donor strain, Pseudomonas putida UWC3, to the indigenous bacteria of two different horizons (A horizon, depth of 0 to 30 cm; B horizon, depth of 30 to 60 cm) of a 2,4-D-contaminated soil was investigated as a means of bioaugmentation. When the soil was amended with nutrients, plasmid transfer and enhanced degradation of 2,4-D were observed. These findings were most striking in the B horizon, where the indigenous bacteria were unable to degrade any of the 2,4-D (100 mg/kg of soil) during at least 22 days but where inoculation with either of the two plasmid donors resulted in complete 2,4-D degradation within 14 days. In contrast, in soils not amended with nutrients, inoculation of donors in the A horizon and subsequent formation of transconjugants (10⁵ CFU/g of soil) could not increase the 2,4-D degradation rate compared to that of the noninoculated soil. However, donor inoculation in the nonamended B-horizon soil resulted in complete degradation of 2,4-D within 19 days, while no degradation at all was observed in noninoculated soil during 89 days. With plasmid pEMT1, this enhanced degradation seemed to be due only to transconjugants (10⁵ CFU/g of soil), since the donor was already undetectable when degradation started. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes showed that inoculation of the donors was followed by a shift in the microbial community structure of the nonamended B-horizon soils. The new 16S rRNA gene fragments in the DGGE profile corresponded with the 16S rRNA genes of 2,4-D-degrading transconjugant colonies isolated on agar plates. This result indicates that the observed change in the community was due to proliferation of transconjugants formed in soil. Overall, this work clearly demonstrates that bioaugmentation can constitute an effective strategy for cleanup of soils which are poor in nutrients and microbial activity, such as those of the B horizon.     

Effect of dissemination of 2,4-dichlorophenoxyacetic acid (2,4-D) degradation plasmids on 2,4-D degradation and on bacterial community structure in two different soil horizons

Transfer of the 2,4-dichlorophenoxyacetic acid (2,4-D) degradation plasmids pEMT1 and pJP4 from an introduced donor strain, Pseudomonas putida UWC3, to the indigenous bacteria of two different horizons (A horizon, depth of 0 to 30 cm; B horizon, depth of 30 to 60 cm) of a 2,4-D-contaminated soil was investigated as a means of bioaugmentation. When the soil was amended with nutrients, plasmid transfer and enhanced degradation of 2,4-D were observed. These findings were most striking in the B horizon, where the indigenous bacteria were unable to degrade any of the 2,4-D (100 mg/kg of soil) during at least 22 days but where inoculation with either of the two plasmid donors resulted in complete 2,4-D degradation within 14 days. In contrast, in soils not amended with nutrients, inoculation of donors in the A horizon and subsequent formation of transconjugants (10(5) CFU/g of soil) could not increase the 2,4-D degradation rate compared to that of the noninoculated soil. However, donor inoculation in the nonamended B-horizon soil resulted in complete degradation of 2,4-D within 19 days, while no degradation at all was observed in noninoculated soil during 89 days. With plasmid pEMT1, this enhanced degradation seemed to be due only to transconjugants (10(5) CFU/g of soil), since the donor was already undetectable when degradation started. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes showed that inoculation of the donors was followed by a shift in the microbial community structure of the nonamended B-horizon soils. The new 16S rRNA gene fragments in the DGGE profile corresponded with the 16S rRNA genes of 2,4-D-degrading transconjugant colonies isolated on agar plates. This result indicates that the observed change in the community was due to proliferation of transconjugants formed in soil. Overall, this work clearly demonstrates that bioaugmentation can constitute an effective strategy for cleanup of soils which are poor in nutrients and microbial activity, such as those of the B horizon.     

Local environmental correlates of variability in the organic soils of moorland and alpine vegetation,Mt Sprent,Tasmania

Abstract Data on soils, vegetation and environment were collected between 510 and 1050m a. s. l. on Mt Sprent, southwestern Tasmania, traversing the Gymnoschoenus sphaerocephalus sedgeland-alpine vegetation boundary. One or more of the following horizons were found in almost all soil pits (downwards from the surface to the bed rock) fibric peat, hemic peat, sapric peat, organic sand, sand and clay. Mean total soil depth, mean organic soil depth, mean humification of the soil surface horizon, pH and mean organic content of the surface horizon all decline with altitude, while the redness of the soil and the mean depth of the mineral and gravel layers increase. At four intensively studied sites at 620, 850, 930 and 1040 m the relationships between phytosociological, topographic and water-table variables, and soil characteristics were determined. The pH of the topsoil was significantly positively related to water-table depth at three sites, but there were no other relationships between local environmental variation and soil characteristics that were consistent between most of the four sites, despite a large number of locally significant relationships. The alpine and sedgeland soils differ most markedly in colour, number of horizons and degree of humification of the surface horizon. The vegetation at each site was separated into communities along a drainage gradient. The mesoscale differences in soils seem most likely to be attributable to a vegetation productivity gradient.     

Diversity of nitrite reductase (nirK and nirS) gene fragments in forested upland and wetland soils

The genetic heterogeneity of nitrite reductase gene (nirK and nirS) fragments from denitrifying prokaryotes in forested upland and marsh soil was investigated using molecular methods. nirK gene fragments could be amplified from both soils, whereas nirS gene fragments could be amplified only from the marsh soil. PCR products were cloned and screened by restriction fragment length polymorphism (RFLP), and representative fragments were sequenced. The diversity of nirK clones was lower than the diversity of nirS clones. Among the 54 distinct nirK RFLP patterns identified in the two soils, only one pattern was found in both soils and in each soil two dominant groups comprised >35% of all clones. No dominance and few redundant patterns were seen among the nirS clones. Phylogenetic analysis of deduced amino acids grouped the nirK sequences into five major clusters, with one cluster encompassing most marsh clones and all upland clones. Only a few of the nirK clone sequences branched with those of known denitrifying bacteria. The nirS clones formed two major clusters with several subclusters, but all nirS clones showed less than 80% identity to nirS sequences from known denitrifying bacteria. Overall, the data indicated that the denitrifying communities in the two soils have many members and that the soils have a high richness of different nir genes, especially of the nirS gene, most of which have not yet been found in cultivated denitrifiers.     

Root biomass distribution of planted <Emphasis Type="Italic">Haloxylon ammodendron</Emphasis> in a duplex soil in an oasis: desert boundary area

Duplex soils, consisting of a sandy surface soil (A-horizon) and silty-clay subsoil (B-horizon), occur in a boundary area between oasis and desert in northwestern China and create a challenging habitat for restoration of plant growth. We conducted an experiment in a 10-year-old H. ammodendron plantation forest to determine the influence of physical properties of duplex soil on water infiltration and plant root growth. We used a trenching method to assess root biomass, and classified roots into two diameter classes: fine (<2 mm) and coarse (>2 mm). Following a 26.7 mm rain event, water infiltrated to the B- horizon; further deep percolation was hindered by low hydraulic conductivity, so that B horizon remained at high available soil moisture for an extended period of time. Root biomass increased rapidly in, or very close to the B horizon, especially for coarse roots. The subsoil formed a barrier to root penetration, but may also reflect the accumulation of water resources at the boundary between the A- and B-horizon. Shoot growth and root distribution, shrub height and canopy area, and total root biomass were negatively correlation with depth to the B horizon, and that was reflected by quadratic functions. We conclude that the texture and structure of duplex soils influenced the soil environment for water infiltration and storage, indicating that the B-horizon underlying sand in duplex soils is advantageous for the growth, and development of planted sand-stabilizing vegetation. These results have important implications for sustainable development of sand-fixing plantations in desert ecosystems.     

顺德生态乐园之土壤及其合理利用建议

广东省顺德生态乐园内的土壤形成发育受气候、生物、地形地貌、母质母岩和人为干扰等５大因素的影响,其中人为活动是导致土层结构破坏和水土流失的主要原因。酸度高、肥力低、土质较好是园内土壤的一个共同特征。在各类土壤中,坡地赤红壤的面积最大,超过７０％,但坡项土层瘠薄。水稻土有较长耕作历史,并已形成了潜育层和潴育层,但土壤肥力并不高。泥炭土有较高的有机质含量,但土壤过酸,速效养分含量过低,难以直接利用。因此     

工矿区不同类型生物结皮对大气降尘重金属的富集规律及其影响因子

大气降尘是矿区土壤重金属的主要来源,而生物结皮对大气降尘重金属有显著的富集作用。为探究不同类型生物结皮对大气降尘重金属的富集规律及其影响因子,选取宁东典型火电厂周边生物结皮广布区作为试验样地,3类生物结皮作为研究对象,并以临近裸土作为对照,对比分析了生物结皮富集大气降尘过程中土壤理化性质、酶活性及重金属含量的变化,采用相关分析、冗余分析和方差分解方法探讨了不同类型生物结皮的结皮层(A层)和层下土壤(B层)重金属含量与其土壤物理、化学性质及酶活性之间的关系。结果表明：燃煤烟尘是矿区大气降尘重金属污染的主要来源,涉及重金属元素包括Cd、Cr、Hg、Pb、Zn、As。生物结皮对源自大气降尘的重金属元素均具有显著的富集作用,且在不同演替阶段生物结皮间的富集规律完全一致：藓结皮>混生结皮>藻结皮;重金属综合污染指数评价结果显示：生物结皮对重金属具有表层富集效应,表现为A层污染程度高于B层。不同类型生物结皮A、B层综合污染指数存在显著差异,排序为：藓结皮>混生结皮>藻结皮;和对照相比,三类生物结皮均能通过富集大气降尘增加其A、B层养分和细颗粒物含量并改善土壤质地。方差分解结...     

Glomalin, an arbuscular-mycorrhizal fungal soil protein, responds to land-use change

Glomalin is a soil proteinaceous substance produced by arbuscular mycorrhizal fungi. Most of the information available concerning this protein has been collected in relation to its role in soil aggregation. In this study, we explored the distribution of glomalin across soil horizons, decomposition of glomalin, and relationship with soil C and N in an agricultural field, a native forest, and an afforested system. Glomalin was present in A, B, and C horizons in decreasing concentrations. Land-use type significantly affected glomalin concentrations (mg cm^–3), with native forest soils having the highest concentrations of the three land-use types in both A and B horizons. In terms of glomalin stocks (Mg ha^–1), calculated based on corrected horizon weights, the agricultural area was significantly lower than both afforested and native forest areas. As measured after a 413 day laboratory soil incubation, glomalin was least persistent in the A horizon of the afforested area.. In agricultural soils and native soils, ca. 50% of glomalin was still remaining after this incubation, indicating that some glomalin may be in the slow or recalcitrant soil C fraction. Comparison of glomalin decomposition with CO₂-C respired during incubation indicates that glomalin makes a large contribution to active soil organic C pools. Soil C and N were highly correlated with glomalin across all soils and within each land-use type, indicating that glomalin may be under similar controls as soil C. Our results show that glomalin may be useful as an indicator of land-use change effects on deciduous forest soils.