Soil Core Method Research Articles

Comparison of minirhizotron and soil core methods for quantifying root biomass in a temperate alley cropping system

A study was carried out in southern Indiana, USA with the objective of comparing soil core sampling and the minirhizotron technique in quantifying fine root biomass and root distribution patterns in an alley cropping system with black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial variation in tree rooting pattern was investigated prior to planting maize. Tree fine root biomass was quantified at distances of 0, 1.1, 2.3, 3.5, and 4.3 m where 0 m represents the tree row and 4.3 m represents the middle of the alley. Root samples were collected to a depth of 90 cm using a hydraulic auger. Maize rooting pattern was determined 65 days after planting to the same depth. Using plexiglass access tubes installed near the actual soil core locations and a minirhizotron camera root images were recorded on a VHS tape. These images were later analyzed using a raster based GIS software (ERDAS-IMAGINE). Regression analysis revealed significant relationships between root surface area measurements from minirhizotron observations and fine root biomass data from soil coring for all species. Predicted fine root biomass data were also in close agreement with actual fine root biomass for all species examined. Maize root biomass was slightly, but not significantly, underestimated by the minirhizotron technique in the top 30 cm soil layer. No significant underestimation or overestimation of root biomass in surface or deeper soil layers was observed for the tree species. The results indicate that minirhizotron can be used in quantifying fine root biomass if site and species specific predictive models can be developed.

Comparison of Tension Infiltrometer, Pressure Infiltrometer, and Soil Core Estimates of Saturated Hydraulic Conductivity

Saturated hydraulic conductivity (KSAT) is an important soil property that is difficult to measure. Positive‐head tension infiltrometer (TI) and single‐ring pressure infiltrometer (PI) techniques show promise for measuring KSAT, but there have been few field tests or comparisons with other methods. The TI, PI, and classical undisturbed soil core (SC) methods for measuring KSAT were compared on single‐grain sand, structured loam, and cracking‐clay loam soils under conventional tillage (CT), no‐tillage (NT), and native woodlot (WL) managements. Of the 27 between‐method correlations (3 methods × 3 soils × 3 managements), only four were significant (P < 0.05). The TI method yielded lower KSAT values under high‐permeability conditions (KSAT ≥ 10−4 ms−1) relative to the other methods, as evidenced by lower geometric mean KSAT (KGM), lower maximum KSAT (KMAX), and lower minimum KSAT (KMIN) values. The 0.10‐m diam. by 0.10‐m‐long SC method cores may have been too small to yield representative estimates of KSAT in the cracking‐clay loam and in the NT and WL managements of the sand and loam, as indicated by high coefficients of variation (CVs), inconsistent KGM values, or high KMAX values relative to the other methods. Erratic KMAX and KMIN values, along with high CVs, suggest that the 0.10‐m‐diam. PI ring may have been too small to adequately sample the cracking clay loam soil under CT and NT management. Further work appears warranted for developing KSAT measurement methods, interpreting KSAT results, and determining appropriate KSAT methods for various soil types and conditions.

Root growth of cauliflower ( Brassica oleracea L. botrytis) under unstressed conditions: Measurement and modelling

Root observations were carried out on cauliflower using the minirhizotron and the soil core method in two years on two locations with different soil types, a loess loam and a humic loamy sand. Total root length (RL) (cm cm-2) of cauliflower was correlated to total shoot dry weight (Wsh) (g m-2) RL=0.0124(±0.005)s*Wsh, r2=0.76. There was an acceptable correlation (r2=0.88) between the minirhizotron and the soil core methods for the sub-soil data, whereas the minirhizotron method underestimated rooting intensity for the top soil. Changes in rooting depth over time could be described for both soil types using a segmented function of temperature sum, consisting of an early exponential and a later linear phase. The increase of rooting depth during the linear phase was 0.107(±0.01) cm °C-1 d-1. A simple descriptive root growth model based on the assumptions of a negative exponential decline of root length density (RLD) with soil depth, of a fixed ratio of RLD at the top of the soil profile and at rooting depth (rRLD) and of a fixed fraction of dry matter increase allocated to fine-roots (ffR) was formulated and used to describe the temporal and spatial variation of RLD found in the field. Slightly different estimates of ffR and of rRLD could be found for the different soil types, indicating a higher fraction of fine-root dry matter for the loess loam soil and a somewhat deeper root system for the humic loamy sand soil. A cross validation using the parameter values obtained from adjusting to the rooting data of one soil type for predicting RLD values of the other soil type, however, indicated that still quite satisfactory estimates (r2=0.91 and 0.95) of RLD could be obtained.

A sampling technique for the determination of dissolved methane in soil solution

A sampling technique was developed to sample floodwater and soil solution from wetland ricefields for the determination of dissolved CH4. The method was compared with the soil core method used in the measurement of entrapped CH4. This was done to assess if dissolved CH4 determination could be an alternative to soil-entrapped CH4 measurements since the latter is time-consuming, laborious and destructive in nature.The dynamics of both dissolved CH4 and entrapped CH4 follow the same seasonal pattern. They have the same degree of spatial and temporal variability. However, the sampling procedure developed for the determination of dissolved CH4 is relatively simple, easy and convenient compared to that for soil-entrapped CH4 measurements. It also allows in-situ solution sampling at different soil depths. Therefore, it is recommended that dissolved CH4 measurements can be an alternative to soil-entrapped CH4 determinations.

Comparison of two versions of the acetylene inhibition/soil core method for measuring denitrification loss from an irrigated wheat field

Two versions of the acetylene inhibition (AI)/soil core method were compared for the measurement of denitrification loss from an irrigated wheat field receiving urea-N at a rate of 100 kg ha–1. With AI/soil core method A, the denitrification rate was measured by analysing the headspace N2O, followed by estimation of N2O dissolved in the solution phase using Bunsen absorption coefficients. With AI/soil core method B, N2O entrapped in the soil was measured in addition to that released from soil cores into the headspace of incubation vessels. In addition, the two methods were also compared for measurement of the soil respiration rate. Of the total N2O produced, 6–77% (average 40%) remained entrapped in the soil, whereas for CO2, the corresponding figures ranged from 12–65% (average 44%). The amount of the entrapped N2O was significantly correlated with the water-filled pore space (WFPS) and with the N2O concentration in the headspace, whereas CO2 entrapment was dependent on the headspace CO2 concentration but not on the WFPS. Due to the entrapment of N2O and CO2 in soil, the denitrification rate on several (18 of the 41) sampling dates, and soil respiration rate on almost all (27 of the 30) sampling dates were significantly higher with method B compared to method A. Averaged across sampling dates, the denitrification rate measured with method B (0.30 kg N ha–1 day–1) was twice the rate measured with method A, whereas the soil respiration rate measured with method B (34.9 kg C ha–1 day–1) was 1.6 times the rate measured with method A. Results of this study suggest that the N2O and CO2 entrapped in soil should also be measured to ensure the recovery of the gaseous products of denitrification by the soil core method.

Assessing fine-root biomass and production in a Scots pine stand: Comparison of soil core and root ingrowth core methods

Soil core and root ingrowth core methods for assessing fine-root (< 2 mm) biomass and production were compared in a 38-year-old Scots pine (Pinus sylvestris L) stand in eastern Finland. 140 soil cores and 114 ingrowth cores were taken from two mineral soil layers (0–10 cm and 10–30 cm) during 1985–1988. Seasonal changes in root biomass (including both Scots pine and understorey roots) and necromass were used for calculating fine-root production. The Scots pine fine-root biomass averaged annually 143 g/m2 and 217 g/m2 in the upper mineral soil layer, and 118 g/m2 and 66 g/m2 in the lower layer of soil cores and ingrowth cores, respectively. The fine-root necromass averaged annually 601 g/m2 and 311 g/m2 in the upper mineral soil layer, and 196 g/m2 and 159 g/m2 in the lower layer of soil cores and ingrowth cores, respectively. The annual fine-root production in a Scots pine stand in the 30 cm thick mineral soil layer, varied between 370–1630 g/m2 in soil cores and between 210 – 490 g/m2 in ingrowth cores during three years. The annual production calculated for Scots pine fine roots, varied between 330–950 g/m2 in soil cores and between 110 – 610 g/m2 in ingrowth cores. The horizontal and vertical variation in fine-root biomass was smaller in soil cores than in ingrowth cores. Roots in soil cores were in the natural dynamic state, while the roots in the ingrowth cores were still expanding both horizontally and vertically. The annual production of fine-root biomass in the Scots pine stand was less in root ingrowth cores than in soil cores. During the third year, the fine-root biomass production of Scots pine, when calculated by the ingrowth core method, was similar to that calculated by the soil core method. Both techniques have sources of error. In this research the sampling interval in the soil core method was 6–8 weeks, and thus root growth and death between sampling dates could not be accurately estimated. In the ingrowth core method, fine roots were still growing into the mesh bags. In Finnish conditions, after more than three growing seasons, roots in the ingrowth cores can be compared with those in the surrounding soil. The soil core method can be used for studying both the annual and seasonal biomass variations. For estimation of production, sampling should be done at short intervals. The ingrowth core method is more suitable for estimating the potential of annual fine-root production between different site types.

Significance of litter- and humus-layer quality for rates and forms of N cycling in moder- to rawhumus-moder profiles under Scots pine (Pinus sylvestris L.)

In three Scots pine stands in northeastern Germany along a gradient of air pollutant deposition loads (particularly sulfate and alkaline dust), the net N release by decomposition, net N immobilization by microorganisms, net N in- and output via soil solution, net N uptake by plants and net N exudation were studied utilizing the soil core method. Apart from NH4-N and NO3-N dissolved organic nitrogen (DON) was measured. The chemical properties of the organic horizons are altered with respect to what is expected from the classification of the moder and rawhumus-moder profiles. These changes are due to former air pollution and site management impacts. Lowest pH values (3.8 in H2O) and widest C:N ratios (27) are found in the moder at the background site Neuglobsow. High concentrations of total extractable N (250 mg N kg−1 d.m.) at this site are explained by the fairly high proportion of extracted DON (64%). The high DON concentrations are correlated to the low pH as well as to high concentrations of total N. Both conditions may stimulate specific microbial activity, known to control the mobilization of soluble organic matter. A shift of the dominant N form to mineral N, especially to NO3-N is observed at the former pollution site Rosa, where pH values are at about 5.2 (H2O). At Rosa the annual net N turnover (189 kg N ha−1 yr−1) is by far higher than at the two other sites (Neuglobsow: 45 and Taura: 70 kg ha−1 yr−1). This holds also true for the annual net N losses (Rosa: 29 kg N ha−1 yr−1, Taura: 9 kg N ha−1 yr−1). At Neuglobsow, instead, net N input of 9 kg ha−1 yr−1 was observed. At the site with the lowest N-input via deposition/fertilization, i.e. Neuglobsow, DON plays an important role for the N fluxes, especially for the N uptake by plants.

Denitrification estimates in monoculture and rotation corn as influenced by tillage and nitrogen fertilizer

Denitrification in agricultural soils results in loss of N for crop growth and production of N2O, a greenhouse gas. Agricultural management must be evaluated for denitrification losses in order to develop minimum N loss systems. Field estimation of denitrification losses is necessary to evaluate crop management effects. Two methods of field denitrification measurements, a soil core (SC) incubation and an in situ closed chamber (CC), were assessed in monoculture corn (Zea mays L.) and corn in rotation with soybean (Glycine max L. Merill) and alfalfa (Medicago sativa L.). Relative estimates of denitrification by the two methods depended on soil texture, with the CC method showing more treatment effects. Denitrification losses were higher with no-till than conventional tillage at one site, and were generally higher with corn than soybean. Nitrogen losses were linear with added N in monoculture corn plots, and ranged from 1.1 to 4.1% of added N. Losses were not related to added N in corn following alfalfa or soybean. Ratios of N2O/(N2O + N2) as measured with the SC method were lower at the Ste. Rosalie (1) site than at the Chicot site (0.95 to 2.84), but ratios of N2O/(N2O + N2) measured with the CC method were similar for the sites, from 0.46 to 1.20. Denitrification losses measured by either method were related to soil moisture and nitrate content in the soils. Corn production should be carried out with conventional tillage and minimum fertilizer N rates for minimum denitrification. Key words: Rotations, corn, soybean, denitrification, closed chamber, soil core

A SOIL CORE METHOD FOR ESTIMATING N-MINERALIZATION AND DENITRIFICATION DURING COVER CROP DECOMPOSITION

A soil core method is described for monitoring rates and extent of N-mineralization and denitrification from intact leguminous cover crops (e.g., hairy vetch) as a function of soil water content. The method also allows for estimates of N-fixation in order to perform N-mass balances. Field conditions were simulated by growing cover crops in soil cores from seed to biomass levels comparable to the field, followed by harvest/kill. Soil cores were wetted periodically using a rain simulator. After simulated rain events, samples of leachate were obtained and soil water content adjusted by application of a vacuum (15 kPa) to the bottom of cores. The use of a PVC/silica filter (bubble point = 30 kPa) allowed for cores to be drained to field capacity without pulling ambient air through the soil. N-fixation (before harvest/kill) and N-mineralization (after harvest/kill) were determined by comparing NO − [over] 3 leached from vetch with fallow cores. Denitrification was determined by periodically sealing cores, injecting and recirculating acetylene throughout cores, and quantifying N2O production after 48 h. Preliminary experiments with hairy vetch (Vicia villosa) indicate that plants are reasonably efficient at taking up soil NO − [over] 3, intact roots decompose fairly rapidly in soil (<6 weeks), and there is potential for substantial losses of soil NO − [over] 3 as a result of denitrification at soil water contents ≥70%.

A comparison between minirhizotron and soil coring methods of estimating root distribution in young almond trees under trickle irrigation

SummaryThe minirhizotron method and the soil coring method were used to study the development of the root system (down to 105 cm) of almond trees cv. Atocha on ‘Pestaneta’ almond rootstock. The study was carried out during the first years of development of the trees under trickle irrigation. Most of the roots (about 80%) developed within the wetted zone of the trickle line in the top 60 cm of soil. The greatest root length density (RLD) was within 30 cm of the soil surface but decreased rapidly with depth. Outside the wetted zone, the greatest root development occurred at about 60 cm depth. When the RLD values obtained by the minirhizotron and soil coring methods were compared, the former was seen to underestimate the RLD values particularly in the top layers of soil so much so that the root distribution patterns established by the methods were not comparable. However, a significant relationship was established between the measurements obtained by both methods at different soil depths.

Wetland Denitrification: Influence of Site Quality and Relationships with Wetland Delineation Protocols

AbstractDenitrification, the microbial conversion of NO3‐ to N gases, is important to wetland biogeochemistry and water quality maintenance functions. We measured denitrification along toposequences from forested upland‐wetland transition zones to red maple wetlands in Rhode Island. The sites were located on different soil parent materials derived from different geomorphic features including glacial outwash, granitic glacial till, basaltic glacial till, and alluvium. Each toposequence contained four or five different natural soil drainage classes. We assessed spatial and temporal variation in denitrification relative to site quality (parent material), water table dynamics, hydric soil and hydrophytic vegetation status, and a “growing season” defined as soil temperature &gt;5°C. Denitrification rate was measured by intensive sampling during a 2‐yr period using an acetylene‐based intact soil core method. Annual estimates of denitrification were produced by extrapolating measured rates over the intervals between sample dates. Soils that were very poorly drained or that had developed on nutrient‐rich parent materials had higher denitrification than more well‐drained and/or less fertile soils. Nitrogen inputs from adjacent ecosystems also appeared to be a key regulator of denitrification rates. Annual denitrification ranged from 1 to &gt;130 kg N ha−1 yr−1 and was lower in Year 2 than in Year 1 in all soils. There were poor relationships between spatial and temporal patterns of denitrification and patterns of hydric soils and hydrophytic vegetation within the wetlands. Wetland delineation and classification protocols based on soils, vegetation, or hydrology do not appear to encompass the capacity of a wetland to support denitrification.

Denitrification, N2-fixation and fermentation during anaerobic incubation of soils amended with glucose and nitrate

Nitrate and glucose additions were investigated for their role in the C and N dynamics during anaerobic incubation of soil. A gas-flow soil core method was used, in which the net production of N2, N2O, NO, CO2, and CH4 under a He atmosphere could be monitored both accurately and frequently. In all experiments clayey silt loam soil samples were incubated for 9 days at 25 °C. Addition of nitrate (50 mg KNO3-N kg-1 soil) had no effect on total denitrification and CO2 production rates, while the N2O/N2 ratio was affected considerably. The cumulative N2O production exceeded the cumulative N2 production for 6 days in the treatment with nitrate addition, compared to 1.2 days in the unamended treatment. Glucose addition stimulated the microbial activity considerably. The denitrification rates were limited by the growth rate of the denitrifying population. During denitrification no significant differences were observed between the treatments with 700 mg glucose-C kg-1 and 4200 mg glucose-C kg-1, both in combination with 50 mg KNO3-N kg-1. The N2 production rates were remarkably low, until NO inf3 sup- exhaustion caused rapid reduction of N2O to N2 at day 2. During the denitrification period 15–18 mg N kg-1 was immobilised in the growing biomass. After NO inf3 sup- shortage, a second microbial population, capable of N2-fixation, became increasingly important. This change was clearly reflected in the CO2 production rates. Net volatile fatty acid (VFA) production was monitored during the net N2-fixation period with acetate as the dominant product. N2-fixation faded out, probably due to N2 shortage, followed by increased VFA production. In the high C treatment butyrate became the most important VFA, while in the low C treatment acetate and butyrate were produced at equal rates. During denitrification no VFA accumulation occurred; this does not prove, however, that denitrification and fermentation appeared sequentially. The experiments illustrate clearly the interactions of C-availability, microbial population and nitrate availability as influencing factors on denitrification and fermentation.

Influence of cropping on the content, composition and dynamics of organic residue in the soil of the plough layer

Organic residue (OR) forms the undecomposed part of soil organic matter (SOM). The majority of it originates from plant remains, but to a certain extent it may also be derived from manure and from the remains of heterotrophic soil organisms. The OR content and dynamics are influenced by management practices (crop rotation, tillage, manuring). The main objective of this work was to study the effect of cropping on the content, fractional composition (coarse and fine fragments) and annual turnover of nonhumified SOM or OR in arable Podzoluvisol in the conditions of south Estonia and to evaluate the role of OR in the humus status of soil. Using the soil-coring method, the OR content and composition and underground phytomass (UGP) as a source of OR in the plough layer were studied. The soil cores (252) were taken during 1991–1992 from three long-term field trials cropped with wheat, barley, rye, potatoes and short-term clover-grass mixtures. The sample plots selected from field trials were tilled conventionally and fertilized according to normal Estonian soil management practice (with a mean rate of N80P23K40 kg ha-1 year-1). The average OR content in arable soil ranged from 1.0 to 1.6 g ash-free dry matter (DMaf) kg-1 soil. The greatest amount of UGP (2.85 g DMaf kg-1), as a source of OR in soil, was estimated for the 2-year clovergrass mixture. Soil organic carbon accumulated in the composition of OR forms 5.7% of the total organic carbon pool of the plough layer. In regular cropping systems the OR content and pool seem to fluctuate within limits determined by the pedoecological conditions of the soil.

Nitrous oxide emission from an agricultural soil subjected to different freeze-thaw cycles

Nitrous oxide (N 2O) emissions from soils have been implicated as the causes of potential greenhouse warming and important nitrogen (N) loss. Soil freeze-thaw cycles have a significant effect on N 2O emission. In this study, potential rates of N 2O emission from an agricultural soil were examined in the laboratory by a soil core method. Spring soil cores from a sandy loam under conventional tillage and inorganic fertilizer management practices were distributed to four different freeze-thaw treatment groups. One group of the soil cores was not refrozen during the experiment, with the others subjected to one, two and three freeze-thaw cycles, respectively. The N 2O flux from the soil core increased with increasing numbers of freeze-thaw cycles. The means of the fluxes ranged from 0.24 to 0.65 kg ha −1 day −1 for non-frozen soil cores and about 60% higher value were found for one freeze-thaw cycle treatment. The results also showed that the first freeze-thaw cycle promoted N 2O flux as a pulse and the same patterns were found for additional freeze-thaw cycles. The information in this study should allow estimation of the potential rates of N 2O emission contributed by freeze-thaw events for specific locations based on the soil climate data for the location.

Semicontinuous Measurement of Soil Atmosphere Gases with Gas‐Flow Soil Core Method

AbstractTo study denitrification, a method was developed for simultaneous measurement of CO2, N2, N2O, and NO production in soil cores. The technique does not interfere with biochemical processes in the soil and is fully automated to enable highly time‐resolved measurements for prolonged periods. Soil cores (intact or repacked) are connected to individual gas‐tight circuits (up to nine). Gas is continuously circulated through the soil cores to avoid diffusional problems. Each individual circuit can be automatically sampled for chromatographic gas analysis. The N2O production rates can be measured accurately down to 0.04 µg N kg−1 measuring interval−1 (MI). Determination of N2, CO2, and O2 production rates is less sensitive: 0.09 mg N kg−1 MI−1, 0.04 mg C kg−1 MI−1, and 0.02 mg O kg−1 MI−1, respectively. Dynamically changing gas production rates are monitored accurately, and total N gas production under anaerobiosis is balanced by NO3− disappearance.

Bromide Transport Detection in Tilled and Nontilled Soil: Solution Samplers vs. Soil Cores

AbstractExperimental validation of solute transport models is often met with unsatisfying or ambiguous results. Aside from the inherent difficulty in conducting these experiments, the lack of a standard set of methodologies employed in these studies may be an impediment. This study was conducted to determine if the method employed in the sampling of soil solutes could influence the results of model validation attempts. A narrow pulse of KBr was uniformly applied to two 25‐m2 plots, one tilled and the other undisturbed, on a level Ulm clay loam (fine, montmorillonitic, mesic Ustollic Haplargid). Solute movement was then monitored for the next 388 d using replicated ceramic cup solution samplers at depths of 0.15, 0.30, 0.80, 1.20, 1.60, and 2.00 m and by the periodic removal of replicate soil cores in 0.05‐m increments to a maximum depth of 3.70 m. Overall, the methods yielded consistent information regarding the mean convective transport of Br−. Both methodologies indicated deeper and more rapid movement of Br− in the nontilled soil, although the shallow solution samplers appear to miss the most rapidly moving solute. By the conclusion of the experiment, the difference between the centers of mass of the Br− plumes in the tilled and nontilled soil was at least 0.6 m. The soil core and solution sampler methods appear to yield inconsistent measures of the solute dispersion but we attribute the differences to the effects of incomplete mass recovery and, we argue, follow naturally from the instrument window of the sampling methodology relative to the observed soil heterogeneity.

Evaluation of the use of food baits for detecting wireworms ( Agriotes spp., Coleoptera: Elateridae) in fields intended for arable crop production

A replicated trial was carried out in Herefordshire, UK to investigate the efficacy of vegetable and cereal-based baits for assessing wireworm populations in grass fields intended for arable crop production. Baits were placed either in the bottom of a hole or in a simple trap placed in a hole. Wireworm capture using baits was compared with that using unbaited traps and holes and a standard soil core method of sampling for wireworms. Overall, more wireworms were captured from holes or traps baited with the cereal seed mixtures than from those baited with carrot or potato. Significant numbers of wireworms were also found just outside cereal-baited traps. Soil core samples captured a similar number of wireworms to the vegetable baits. Processing times for individual samples (assessed by hand search or a combination of hand search and flotation) were also recorded. The use of food baits is potentially a more sensitive and less labour-intensive means of detecting wireworms in fields intended for arable production than the methods currently used.

Comparison of clod and core methods for determination of soil bulk density

Abstract An interagency forest monitoring program has been initiated on a systematic network of forested plots often accessible only by foot traffic along a compass line. Extensive site classification and physiochemistry data are being collected for vegetation and soil indicators of forest health. In order to select a suitable technique for obtaining an estimate of mineral soil bulk density, conventional clod and core methods were compared across a wide range of forest soils within the Coastal Plain of southeastern Virginia. Replicate soil clods and cores were collected from two to four horizons within each of six pedons representing different soil series. Following analysis, the sample data were used to evaluate main and interaction effects due to differences in the method, series, horizon, and texture effects. Differences between the clod and core data were highly significant on average (P < 0.001) as were all of the main effects. Both methods exhibited high precision (average CV < 5%) within the indivi...

Factors controlling denitrification rates in upland and swamp forests

Spatial patterns of denitrification and temporal variation in the factors controlling this process were studied in three forested ecosystems in northern Lower Michigan. Two forest stands were randomly located within each of two well-drained upland forests (sugar maple–red oak/Maianthemum and sugar maple–basswood/Osmorhiza ecosystems) and one swamp ecosystem (silver maple–red maple/Osmunda ecosystem). Potential N mineralization, nitrification, and microbial respiration were measured in each forest stand using a 33-week laboratory incubation. Factors controlling denitrification were investigated in each ecosystem by treating soil samples with factorial combinations of NO3−, C, and Ar (anaerobic conditions). We also investigated the separate production of N2 and N2O during denitrification, and the factors controlling these fluxes, in a different experiment. Seasonal patterns of denitrification were quantified using an intact soil core method. Potential nitrification and microbial respiration were consistently highest in the swamp forest and lowest in the sugar maple–red oak/Maianthemum ecosystem (582 vs. 3 μg NO3−-N•g−1 and 5275 vs. 1254 μg CO2-C•g−1, respectively). Nitrate availability was the most important factor controlling denitrification in the swamp ecosystem, whereas increased soil water content resulted in the greatest response in the upland forests. Although NO3− significantly increased denitrification in the upland ecosystems, water additions elicited an even greater response. In addition, N2O production in the upland forests accounted for 70 to 90% of the total gaseous N loss; N2O accounted for only 25% of this loss in the swamp forest. Mean denitrification (intact soil cores) in the sugar maple–red oak/Maianthemum ecosystem (12 μg N2O-N•m−2•d−1) was significantly lower than rates measured in the sugar maple–bass-wood/Osmorhiza and silver maple–red maple/Osmunda ecosystems (24 and 39 μg N2O-N•m−2•d−1, respectively). Denitrification reached a maximum during June and July in the sugar maple–basswood/Osmorhiza ecosystem, whereas peaks occurred in May and September in the silver maple–red maple/Osmunda ecosystem. Denitrification in the sugar maple–red oak/Maianthemum forest was variable throughout the year and consistently low. Although variability was high, results suggest that denitrification and the factors controlling this process can be predicted using the spatial distribution of ecosystems.

Comparison of Soil Coring and Ingrowth Methods for Measuring Belowground Production

EcologyVolume 73, Issue 5 p. 1918-1921 Article Comparison of Soil Coring and Ingrowth Methods for Measuring Belowground Production Christopher Neill, Christopher NeillSearch for more papers by this author Christopher Neill, Christopher NeillSearch for more papers by this author First published: 01 October 1992 https://doi.org/10.2307/1940044Citations: 90AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume73, Issue5October 1992Pages 1918-1921 RelatedInformation