Temperature gradient chambers for research on global environment change. III. A system designed for rice in Kyoto, Japan

Synthesis and validation of crop models for assessment of of the impact of elevated atmospheric CO₂ concentration and anticipated global warming on crop production require crop response data obtained under field-like conditions. The temperature gradient chamber (TGC) with the facility for CO₂ enrichment allows the creation of various CO₂ and temperature regimes for crops over the entire growth period with relatively inexpensive construction and running costs. The TGC develops a temperature gradient along its longitudinal axis using solar energy during the day and heating at night while maintaining the natural diurnal cycle. The temperature gradient and the CO₂ concentration in the TGC are regulated by computer control of the air ventilation rate through the TGC and of the CO₂ release rate. Longitudinal gradients of CO₂ concentration and water vapour pressure deficit of air in the TGC were generally less than 5% and ±0.2 kPa, respectively. A CO₂ enrichment experiment on rice in the TGC showed that a doubling of the CO₂ concentration markedly enhanced crop dry matter production. Temperature had less effect on dry matter production, although panicle dry weight was greatly decreased at higher temperature as a result of high-temperature-induccd sterility of rice spikelets. Since rice spikclets are most sensitive to high temperature at the moment of flowering, and their flowering habit is highly synchronized with the diurnal courses of environmental conditions, the TGC is a useful tool in understanding rice responses to changes in atmosphere and temperature.     

Temperature gradient chambers for research on global environment change. II. A twin-wall tunnel system for low-stature, field-grown crops using a split heat pump

A temperature gradient chamber (TGC) is described which enables elevated CO₂ concentrations and a dynamic temperature gradient to be imposed on field crops throughout their life cycle under standard husbandry. Air is circulated through two double-walled polyethylene-covered tunnels connected to a split heat pump system to give a near-linear temperature gradient along each tunnel. Solar energy gain along each tunnel and exchange with outer tunnel air flow contribute to the temperature gradient and also produce diurnal and seasonal temperature fluctuations corresponding to ambient conditions. Mean temperature gradients of between 3 and 5°C have been recorded throughout the growing seasons of crops of lettuce, carrot, cauliflower and winter wheat. Elevated or present CO₂ concentrations are maintained in each of two pairs of tunnels throughout the cropping season using pure CO₂ injected through motorized needle valves. This system can realistically simulate aspects of the effects of projected future environmental change on crop growth, development and yield, and in particular tin-possible interaction of the effects of increased CO₂ and temperature.     

Temperature-controlled open-top chambers for global change research

To enable experiments on the interactive effects of elevated atmospheric CO₂ and increased air temperature on physiological processes in trees to be carried out, we altered the standard design of open-top chambers by replacing blowers with evaporative coolers and in-line heaters, with a feedback control system to maintain ambient or elevated air temperatures within the chambers. Ambient and elevated (+ 4 °C) temperature regimes were attained consistently and reliably throughout the growing season, with high reproducibility between chambers. From May through December the average of nearly 300,000 temperature measurements was 18.5 °C in ambient air, 18.9 ± 0.6 °C in six ambient chambers, and 22.4 ± 0.9 °C in six elevated temperature chambers. The difference in soil temperature between ambient and elevated chambers was 1.2 °C. Absolute humidity (vapour pressure) in the chambers was higher than that of ambient air, but it was generally similar between temperature treatments. Vapour pressure deficit therefore was higher in elevated temperature chambers than in ambient chambers, and this difference is considered an inseparable part of the temperature treatment. The addition of a temperature control system to open-top chambers removes what has been an important flaw in this important tool for global change research.     

A compact lighting system for use with portable leaf chambers to measure photosynthesis

Abstract. A compact, portable lighting system, developed for the measurement of photosynthesis in the field with portable chambers and applicable to the laboratory, is described. The system consists of a miniature 50-W, 12-V tungsten-halogen lamp and a light guide which is constructed with randomized fibre bundles and mounted above the window of a portable assimilation chamber. The light guide distributes light uniformly across the leaf surface; the photon irradiance at the leaf surface is monitored by measuring the irradiant emitted from one fibre-optic bundle using a sensor connected to the body of the light guide. Up to 1600 μmol quanta photosynthetic active radiation m⁻²s⁻¹ may be achieved at the leaf surface; irradiance may be varied by wire mesh screens of different densities. Leaf temperature follows air temperature outside the chamber to within ±2 °C over the range 10–30 °C and within the range of photon irradiances from 0 to 1600/μmol quanta m ⁻²s. The power supply for the lamp is a 12-V, 24-A h lead-acid battery and the photon irradiance at the leaf surface gradually decreases by c. 3% over 2.5 h of measurement. With this system, response of photosynthetic rate to irradiance and to CO₂ partial pressure at constant irradiance may be measured in the field, independent of natural variations in solar irradiance.     

Open top chambers for exposing plant canopies to elevated CO2 concentration and for measuring net gas exchange

Open top chamber design and function are reviewed. All of the chambers described maintain CO₂ concentrations measured at a central location within ±30 ppm of a desired target when averaged over the growing season, but the spatial and temporal range within any chamber may be closer to 100 ppm. Compared with unchambered companion plots, open top chambers modify the microenvironment in the following ways: temperatures are increased up to 3°C depending on the chamber design and location of the measurement; light intensity is typically diminished by as much as 20%; wind velocity is lower and constant; and relative humidity is higher. The chamber environment may significantly alter plant growth when compared with unchambered controls, but the chamber effect on growth has not been clearly attributed to a single or even a few environmental factors.A method for modifying an open top chamber for tracking gas exchange between natural vegetation and the ambient air is described. This modification consists of the addition of a top with exit chimney to reduce dilution of chamber CO₂ by external ambient air, is quickly made and permits estimation of the effects of elevated CO₂ and water vapor exchange.The relatively simple design and construction of open top chambers make them the most likely method to be used in the near future for long-term elevated CO₂ exposure of small trees, crops and grassland ecosystems. Improvements in the basic geometry to improve control of temperature, reduce the variation of CO₂ concentrations, and increase the turbulence and wind speed in the canopy boundary layer are desirable objectives. Similarly, modifications for measuring water vapor and carbon dioxide gas exchange will extend the usefulness of open top chambers to include non-destructive monitoring of the responses of ecosystems to rising atmospheric CO₂.     

Air pressure in clamp-on leaf chambers: a neglected issue in gas exchange measurements

Air pressure in leaf chambers is thought to affect gas exchange measurements through changes in partial pressure of the air components. However, other effects may come into play when homobaric leaves are measured in which internal lateral gas flow may occur. When there was no pressure difference between the leaf chamber and ambient air (DeltaP=0), it was found in previous work that lateral CO(2) diffusion could affect measurements performed with clamp-on leaf chambers. On the other hand, overpressure (DeltaP>0) in leaf chambers has been reported to minimize artefacts possibly caused by leaks in chamber sealing. In the present work, net CO(2) exchange rates (NCER) were measured under different DeltaP values (0.0-3.0 kPa) on heterobaric and homobaric leaves. In heterobaric leaves which have internal barriers for lateral gas movement, changes in DeltaP had no significant effect on NCER. For homobaric leaves, effects of DeltaP>0 on measured NCER were significant, obviously due to lateral gas flux inside the leaf mesophyll. The magnitude of the effect was largely defined by stomatal conductance; when stomata were widely open, the impact of DeltaP on measured NCER was up to 7 mumol CO(2) m(-2) s(-1) kPa(-1). Since many other factors are also involved, neither DeltaP=0 nor DeltaP>0 was found to be the 'one-size fits all' solution to avoid erroneous effects of lateral gas transport on measurements with clamp-on leaf chambers.     

Modification and testing of a domestic freezer for use in studies of plant growth and survival at low temperatures

Modifications of a domestic freezer are described, which convert it to a versatile controlled environment chamber capable of maintaining temperatures between ambient and - 18 °C and therefore useful in investigations both of plant growth at low positive temperatures and of survival of sub-zero temperatures. The temperature control mechanism can provide a wide range of diurnal temperature regimes and of cooling and warming rates. Measurements in two such chambers showed air temperatures were always uniform to within ° 1 °C of set temperature except in a 6 cm band round the inside walls, where they were lower by 0°6 °C, at most; CO₂ concentration was always close to 300 v.p.m.; relative humidity was usually in the range 80–90% and photon flux densities during the light period were 180 ° 10 μmol m^-2 s^-1. The uniformity of environmental conditions within each chamber was confirmed by measurements of leaf growth and plant survival of tillers of a single genotype of perennial ryegrass growing in pots of compost. These tests also confirmed the lower temperature of the 6 cm band adjacent to the chamber walls. Although temperature settings were identical, air and compost temperatures were 0°3 °C higher in one of the two chambers tested. Although this difference did not result in significant differences in plant survival, significant differences in leaf lamina extension were found between cabinets. Problems encountered in the design and testing of the chambers are discussed.     

Multichannel automated chamber system for continuous monitoring of CO2 exchange between the agro-ecosystem or soil and the atmosphere

A multichannel automated chamber system was developed for continuous monitoring of CO₂ exchange at multiple points between agro-ecosystem or soil and atmosphere. This system consisted of an automated chamber subsystem with a CO₂ concentration analyzer and a data logging subsystem. Both subsystems were under the control of a programmable logic controller (PLC). The automated chamber subsystem contained 18 chambers (50 cm × 50 cm × 50 cm) and a compressor. The chamber lids were closed and can be automatically opened. During measurement, one of the 18 chambers was kept closed for three minutes for measuring and the other chambers were kept open to maintain the natural soil conditions to the maximum extent. Environmental variables were simultaneously measured using sensors and recorded by the data logger. The reliability of the multichannel automated chamber system was tested and the results showed that the turbulence of the fans had no significant effect on the CO₂ exchange. The changes in the air and the temperature of soil and soil moisture inside the chambers, caused by the enclosure of the chambers, were not significant. The net ecosystem CO₂ exchange for the wheat ecosystem was ?2.35 μmol·m^?2·s^>?1 and the soil respiration was 3.87 μmol·m^?2·s^>?1 in the wheat field, and 6.61 μmol·m^?2·s^>?1 in the apple orchard.     

A chamber for the simulation of radiation freezing of plants

Frost injury to plants can occur following episodic radiation frosts. In the UK this is particularly important to spring sown crops such as potatoes. Most laboratory based frost studies simulate freezing using either conductive or convective freezing chambers. Such frost tests do not simulate overnight freezing events adequately. A freezing chamber based on radiative cooling is described which mimics overnight radiative freezing. The chamber is rectangular in design (1 m × lm × 2 m high) with a radiative cooling plate at the top of the chamber cooled to -40°C to -45°C using HFC coolants, which acts as a cold black body. The sides of the chamber are also cooled to variable temperatures down to -5°C in order to prevent the chamber walls radiating to the plant material during testing. Using thermocouples to measure air temperature and plant temperature the chamber has been characterised to simulate the radiative cooling conditions found in the UK during autumn and spring. Exotherm detection upon plant freezing is simplified by virtue of the reduction in temperature fluctuation normally experienced at the plant surface during natural freezing. Radiation frosts and subsequent frost damage to potatoes have been recorded in the temperature range -4°C to –5°C. The equipment is recommended for studies of frost damage to plants normally caused by episodic radiation frost events.     

Bioaerosols of subterraneotherapy chambers at salt mine health resort

Nowadays, an inhalation of naturally generated aerosols has again become a widely practiced method of balneological treatment of various respiratory diseases. The aim of this study was to characterize the microbial aerosol of subterraneotherapy chambers at the Bochnia Salt Mine Health Resort in southern Poland. The measurements were carried out using a 6-stage Andersen impactor over a period of 1 year in both indoor (i.e., two subterranean chambers, where curative treatments took place) and outdoor air. The maximum bacterial aerosol concentrations in the chambers reached 11,688 cfu/m³. In such interiors, a high-performance method of microbial contaminant reduction need be introduced, especially when large groups of young patients are medically cured. Respecting fungal aerosol, its average indoor concentration (88 cfu/m³) was significantly lower than outdoor level (538 cfu/m³). It confirms that ventilation system provides efficient barrier against this type of biologically active propagules. Among identified micro-organisms, the most prevalent indoors were Gram-positive cocci, which constituted up to 80 % of airborne microflora. As highly adapted to the diverse environments of its human host (skin, respiratory tract), they can be easily released in high quantities into the air. The number of people introduced into such subterranean chambers should be in some way limited. The analysis of microclimate parameters revealed that temperature and relative humidity influenced significantly the level of bacterial aerosol only. Hence, a constant control of these parameters should be scrupulously superintended at this type of subterranean premises.     

Ion exposure chambers for small animals

Ion exposure chambers that have been designed and tested for use in biological and behavioral research with small animals are described in this report. The chambers exhibit an acceptable degree of uniformity in ion concentration, current density, and electric field within the exposure area. Gaseous by-products of corona discharge (O3 and NO2) have been measured and found to be less than .01 ppm and less than .1 ppm, respectively. Filtered air is fed to the individual exposure chambers, and temperature and humidity are well controlled. Noise due to corona and the air delivery system has been measured.     

Do open-top chambers overestimate the effects of rising CO2 on plants? An analysis using spring wheat

The microclimate in facilities for studying effects of elevated CO₂ on crops differs from ambient conditions. Open-top chambers (OTCs) increase temperature by 1–3 °C. If temperature and CO₂ interact in their effect on crops, this would limit the value of OTC experiments. Furthermore, interaction of CO₂ and temperature deserves study because increases in atmospheric CO₂ concentration are expected to cause global warming. This paper describes two experiments in which a recently developed cooling system for OTCs was used to analyse the effects of temperature on photosynthesis, growth and yield of spring wheat (Triticum aestivum L., cv. Minaret). Two levels of CO₂ were used (350 and 700 ppm), and two levels of temperature, with cooled OTCs being 1.6–2.4 °C colder than noncooled OTCs. Photosynthetic rates were increased by elevated CO₂, but no effect of temperature was found. Cross-switching CO₂ concentrations as well as determination of A–C_i curves showed that plant photosynthetic capacity after anthesis acclimated to elevated CO₂. The acclimation may be related to the effects of CO₂ on tissue composition: elevated CO₂ decreased leaf nitrogen concentrations and increased sugar content. Calculations of the seasonal mean crop light-use efficiency (LUE) were consistent with the photosynthesis data in that CO₂ increased LUE by 20% on average whereas temperature had no effect. Both elevating CO₂ and cooling increased grain yield, by an average of 11% and 23%, respectively. CO₂ and temperature stimulated yield via different mechanisms: CO₂ increased photosynthetic rate, but decreased crop light interception capacity (LAI), whereas cooling increased grain yield by increasing LAI and extending the growing season with 10 days. The effects of CO₂ and temperature were not additive: the CO₂ effect was about doubled in the noncooled open-top chambers. In most cases, effects on yield were mediated through increased grain density rather than increased individual grain weights. The higher growth response to elevated CO₂ in noncooled vs. cooled OTCs shows that a cooling system may remove a bias towards overestimating crop growth response to CO₂ in open-top chambers.     

Plant growth chambers for the simultaneous control of soil and air temperatures, and of atmospheric carbon dioxide concentration

Many facilities for growing plants at elevated atmospheric concentrations of CO₂ ([CO₂]) neglect the control of temperature, especially of the soil. Soil and root temperatures in conventional, free-standing pots often exceed those which would occur in the field at a given air temperature. A plant growth facility is described in which atmospheric CO₂ can be maintained at different concentrations while soil and air temperatures mimic spatial and temporal patterns seen in the field. It consists of glasshouse-located chambers in which [CO₂] is monitored by an infra-red gas analyser and maintained by injection of CO₂ from a cylinder. Air is cooled by a heat exchange unit. Plants grow in soil in 1.2 m long containers that are surrounded by cooling coils and thermal insulation. Both [CO₂] and temperature are controlled by customized software. Air temperature is programmed to follow a sine function of diurnal time. Soil temperature at a depth of 0.55 m is programmed to be constant. Temperature at 0.1 m depth varies as a damped, lagged function of air temperature; that at 1.0 m as a similar function of the 0.55 m temperature. [CO₂] is maintained within 20 μmol mol^?1 of target concentrations during daylight. A feature of the system is that plant material is labelled with a ¹³C enrichment different from that of carbon in soil organic matter. The operation of the system is illustrated with data collected in an experiment with spring wheat (Triticum aestivum L., cv Tonic) grown at ambient [CO₂] and at [CO₂] 350 μmol mol^?1 greater than ambient.     

Effects of air temperature, photoperiod and leaf age on foliar senescence of western larch (Larix occidentalis Nutt.) in environmentally controlled chambers

We induced foliar senescence in western larch (Larix occidentalis Nutt.) needles (100 to 400 d old) in chambers set to combinations of photoperiod (8 or 16 h) and air temperature (8 or 15°C). We used regression analysis to estimate the effects of air temperature, photoperiod, provenance and leaf age on the date of decline in chlorophyll, photosynthesis, and chlorophyll a/b ratio. Increased air temperature delayed the decline in chlorophyll and photosynthesis without affecting chlorophyll a/b: seedlings with 200-d-old needles placed under 8h days and 8°C lost chlorophyll, photosynthesis and chlorophyll a/b in 22, 37 and 63d, respectively, while those senescing under 15°C lost them in 54, 61 and 63d. Extended photoperiod delayed the decline in chlorophyll but not photosynthesis or chlorophyll a/b ratio: the 200-d-old needles placed in 8°C and 16 h photoperiod lost chlorophyll, photosynthesis, and chlorophyll a/b in 34, 37 and 63 d, compared with 22, 37 and 63 d for seedlings in 8 h days. Our analysis shows that it is possible to quantify the extent to which the timing and process of senescence vary with environmental conditions.     

Multi-objective environment chamber system for studying plant responses to climate change

This paper describes the technical information and performance of a new multi-objective chamber system enabling the control of environmental variables (e.g., temperature, CO₂, air humidity, wind speed, and UV-B radiation) for understanding plant responses to climate change. Over a whole growing season, four different climate scenarios were evenly programmed into the system’s 16 chambers as ambient environment (AMB), elevated temperature (ET), elevated CO₂ concentration (EC) and elevated temperature and CO₂ concentration (ETC). Simultaneously, the chamber effects were assessed regarding the physiological responses and growth of a boreal perennial grass (reed canary grass, Phalaris arundinacea L.). During the growing season, the chamber system provided a wide variety of climatic conditions for air temperature (T _a), relative humidity (RH) and CO₂ concentration (C _a) in the AMB chambers following outside conditions. The target temperature (+3.5°C) was achieved to a good degree in the ET and ETC chambers, being on average 3.3°C and 3.7°C higher than ambient conditions, respectively. The target concentration of CO₂ (700 ppm) was also well achieved in the EC and ETC chambers, being on average 704 ppm and 703 ppm, respectively. The stable airflow condition inside all of the chambers provided a homogeneous distribution of gases and temperature. The decreases in RH and increases in vapour pressure deficit (VPD) in the elevated temperature chambers were also maintained at a low level. Chamber effects were observed, with some physiological and growth parameters of plants being significantly lower in the AMB chambers, compared to outside conditions. The plant growth was negatively affected by the reduced radiation inside the chambers.     

Red to far-red ratio correction in plant growth chambers - growth responses and influence of thermal load on garden pea

Plant growth chambers are commonly used to minimize environmental variation but the light sources used vary considerably from natural light and from each other. Incandescent globes are often used to add more far-red light, with the aim of producing a more natural red to far-red ratio (R:FR), but also add to thermal load. High-intensity discharge lamps are often used to produce higher irradiances, more akin to natural light, but the thermal implications are rarely considered because air temperature is controlled. This paper examines the spectral properties and thermal implications of growth chamber light sources and takes a whole-plant physiology approach, by examining growth responses of a photoperiodic pea line ( Pisum sativum L. cv. Torsdag) in the same growth chamber type under different light sources – in essence using plants to study the controlled environments rather than vice-versa. High R:FR delayed flowering and inhibited internode extension in pea. However, the addition of far-red-rich incandescent globes in the proportions provided in the growth chambers (400–500 W) did little to reduce R:FR, did not induce earlier flowering and actually further inhibited internode length. Leaflet size and yield were significantly reduced. While air temperature was maintained at 20°C in all experiments, radiant temperature was significantly higher under high irradiance and/or with incandescent added, and soil temperatures were elevated. Growth responses under these lights were similar to the effect caused by elevating the air temperature. An alternative method of controlling R:FR, without thermal load implications, using light-emitting diodes is described.     

Dosimetry in magnetic fields with dedicated MR-compatible ionization chambers

MR-integrated radiotherapy requires suitable dosimetry detectors to be used in magnetic fields. This study investigates the feasibility of using dedicated MR-compatible ionization chambers at MR-integrated radiotherapy devices. MR-compatible ionization chambers (Exradin A19MR, A1SLMR, A26MR, A28MR) were precisely modeled and their relative response in a 6MV treatment beam in the presence of a magnetic field was simulated using EGSnrc. Monte Carlo simulations were carried out with the magnetic field in three orientations: the magnetic field aligned perpendicular to the chamber and beam axis (transverse orientation), the magnetic field parallel to the chamber as well as parallel to the beam axis. Monte Carlo simulation results were validated with measurements using an electromagnet with magnetic field strength upto 1.1 T with the chambers in transverse orientation. The measurements and simulation results were in good agreement, except for the A26MR ionization chamber in transverse orientation. The maximum increase in response of the ionization chambers observed was 8.6% for the transverse orientation. No appreciable change in chamber response due to the magnetic field was observed for the magnetic field parallel to the ionization chamber and parallel to the photon beam.Polarity and recombination correction factor were experimentally investigated in the transverse orientation. The polarity effect and recombination effect were not altered by a magnetic field.This study further investigates the response of the ionization chambers as a function of the chambers’ rotation around their longitudinal axis. A variation in response was observed when the chamber was not rotationally symmetric, which was independent of the magnetic field.     

Direct effects of atmospheric carbon dioxide concentration on whole canopy dark respiration of rice

The purpose of this study was to test for direct inhibition of rice canopy apparent respiration by elevated atmospheric carbon dioxide concentration ([CO₂]) across a range of short‐term air temperature treatments. Rice (cv. IR‐72) was grown in eight naturally sunlit, semiclosed, plant growth chambers at daytime [CO₂] treatments of 350 and 700 μmol mol^?1. Short‐term night‐time air temperature treatments ranged from 21 to 40 °C. Whole canopy respiration, expressed on a ground area basis (R_d), was measured at night by periodically venting the chambers with ambient air. This night‐time chamber venting and resealing procedure produced a range of increasing chamber [CO₂] which we used to test for potential inhibitory effects of rising [CO₂] on R_d. A nitrous oxide leak detection system was used to correct R_d measurements for chamber leakage rate (L) and also to determine if apparent reductions in night‐time R_d with rising [CO₂] could be completely accounted for by L. The L was affected by both CO₂ concentration gradient between the chamber and ambient air and the inherent leakiness of each individual chamber. Nevertheless, after correcting R_d for L, we detected a rapid and reversible, direct inhibition of R_d with rising chamber [CO₂] for air temperatures above 21 °C. This effect was larger for the 350 compared with the 700 μmol mol^?1 daytime [CO₂] treatment and was also increased with increasing short‐term air temperature treatments. However, little difference in R_d was found between the two daytime [CO₂] treatments when night‐time [CO₂] was at the respective daytime [CO₂]. These results suggest that naturally occurring diurnal changes in both ambient [CO₂] and air temperature can affect R_d. Because naturally occurring diurnal changes in both [CO₂] and air temperature can be expected in a future higher CO₂ world, short‐term direct effects of these environmental variables on rice R_d can also be expected.     

Biotic validation of small open-top chambers in a tundra ecosystem

Small open‐top chambers (OTC) are used widely in ecosystem warming experiments. The efficacy of the open‐top chamber as an analogue of climatic warming is examined. Twenty‐four small OTCs were used to passively warm canopy temperatures in wet meadow tundra at Barrow, Alaska, during two consecutive summers with contrasting surface air‐temperatures. Fortuitously, the seasonal average temperature regime within chambers in the colder year (1995) was similar to the controls of the warmer year (1996); this allowed a comparison of natural vs. chamber warming. All measured plant responses behaved similarly to both year and treatment 68% of the time. A comparison of the populations of the warmer summer's control with the cooler summer's OTC found no statistical difference in 80% of the response variables measured. A meta‐analysis also found no significant difference between the responses of the two populations. These results give empirical biotic validation for the use of the OTC as an analogue of regional climate warming.     

Testing the Use of Static Chamber Boxes to Monitor Greenhouse Gas Emissions from Wood Chip Storage Heaps

This study explores the use of static chamber boxes to detect whether there are fugitive emissions of greenhouse gases (GHGs) from a willow chip storage heap. The results from the boxes were compared with those from 3-m stainless steel probes inserted into the core of the heap horizontally and vertically at intervals. The results from probes showed that there were increases of carbon dioxide (CO₂) concentrations in the heap over the first 10 days after heap establishment, which were correlated with a temperature rise to 60 °C. As the CO₂ declined, there was a small peak in methane (CH₄) concentration in probes orientated vertically in the heap. Static chambers positioned at the apex of the heap detected some CO₂ fluxes as seen in the probes; however, the quantities were small and random in nature. A small (maximum 5 ppm) flux in CH₄ occurred at the same time as the probe concentrations peaked. Overall, the static chamber method was not effective in monitoring fluxes from the heap as there was evidence that gases could enter and leave around the edges of the chambers during the course of the experiment. In general, the use of standard (25 cm high) static chambers for monitoring fluxes from wood chip heaps is not recommended.