bluuebunny/crossref_metadata_2025 huggingface dataset:
An analytic signal approach to the interpretation of total field magnetic anomalies1
Authors: Qin Shuang
Published: April 2006

The analytic signal (AS) is defined as the square root of the sum of the squares of the vertical and the two horizontal derivatives of the total magnetic field ΔT. This paper verifies theoretically that peaks of the AS correlate directly with their magnetic causative bodies and are positioned symmetrically over them, i.e. the main feature of the AS is that it is independent of the inclination of the magnetic field. This avoids the difficulties that are often faced in the conventional process of reduction to pole for ΔT, when the direction of magnetization of the causative bodies is not known. In addition, the AS has characteristics similar to the derivative features of the magnetic field, so that it is very sensitive to edge effects of the causative magnetic bodies. The theoretical derivations are tested by comparison with calculations on models, and, in a field example from Hunan Province, China, the AS is applied successfully to the interpretation of ΔT, whereas the conventional process of reduction to pole fails, due to the reverse magnetization of the causative body.
Cost‐effective 3D one‐pass depth migration1
Authors: Sollid A. , Arntsen B.
Published: April 2006

A crucial point in the processing of 3D seismic data is the migration step, both because of its 3D nature and the computational cost involved. The efficiency and accuracy of 3D migration are determined by the wavefield extrapolation technique employed. Wavefield extrapolation based on second‐order differential operators of variable‐length is very efficient and accurate at the same time. Compared to migration based on the McClellan transform and operator splitting, the use of variable‐length second‐order differential operators offers significant advantages. The 3D migration operator has an almost perfect circular symmetry. No positioning errors in the 45° azimuth between the in‐line and cross‐line directions are evident. The method is, in practice, only limited by spatial aliasing and does not require expensive interpolation of data to reduce numerical artifacts. This reduces the computational cost of 3D one‐pass depth migration by a large factor.
The potential of a noise‐reducing antenna for surface NMR groundwater surveys in the earth's magnetic field1
Authors: Trushkin D.V. , Shushakov O.A. , Legchenko A.V.
Published: April 2006

A method of non‐invasive NMR in the earth's field has been developed and is now used for groundwater surveys to depths of investigation of 100 m or more.

A circular wire loop of diameter 100 m, laid out on the ground, is employed to excite and receive the NMR signal in the earth's field. However, in areas with high electromagnetic noise, the NMR measurements may be inaccurate.

To overcome this problem, a noise‐reducing figure‐of‐eight‐shaped antenna, consisting of two touching coils each of diameter 50 m, has been utilized.

Using this antenna, the NMR signal has been calculated for different depths of water‐saturated layers with various inclinations of the geomagnetic field. The model calculations and experimental data have been compared and found to be mutually consistent. The two‐coil antenna is shown to be suitable for studies at depths of up to 30–40 m, which is of practical importance for engineering geology.
Effect of mining subsidence on seismic velocity monitored by a repeated reflection profilel1
Authors: Al‐Rawahy S.Y.S. , Goulty N.R.
Published: April 2006

We have monitored changes in seismic velocity due to longwall coal‐mining in the Selby coalfield, Yorkshire, England by. ten repeated surveys of a surface seismic reflection profile. The direction of face advance in the Barnsley Seam, at 550 m depth, was parallel to the orientation of the profile. The traveltime of a strong reflection event from an anhydrite bed at 150 m depth was measured after processing the data with standard techniques. As the face advanced, the traveltime increased by about 4% overall. In detail, the progressive increase in traveltime correlates well with empirical calculations of differential subsidence between the surface and the anhydrite. However, the magnitude of the change must principally be accounted for by a decrease in seismic velocity, which we attribute to a reduction in the vertical effective stress.
Ultrasonic wave propagation in dry and brine‐saturated sandstones as a function of effective stress: laboratory measurements and modelling1
Authors: Tao G. , King M.S. , Nabi‐Bidhendi M.
Published: April 2006

Compressional and shear‐wave velocities have been measured and a novel approach using digital processing employed to study wave attenuation for brine‐ and gas‐ saturated sandstones, over a range of effective stresses from 5 to 60 MPa. Also measured were the complex conductivity in the brine‐saturated state and permeability in the gas‐saturated state over the same range of stresses as for the velocity measurements. Broadband ultrasonic pulses of P‐ and orthogonally polarized S‐waves in the frequency range 0.3–0.8 MHz are transmitted through the specimen to be characterized for comparison with a reference (aluminium) having low attenuation. The attenuation is calculated in terms of the quality factor Q from the Fourier spectral ratios, using the frequency spectral ratios technique. The corrections necessary for the effects of diffraction due to the finite size of the ultrasonic transducers have been carried out for the case of measurements under lower confining stress. To interpret the laboratory measured velocity and attenuation data under the physical conditions of this study and to estimate the effects of pore structure, numerical modelling of velocities and attenuation as functions of the confining stress have been performed, based on the MIT model. Theoretical models based on several hypothesized attenuation mechanisms are considered in relation to laboratory data of the effects of confining pressure, fluid saturation and pore structure on attenuation. Numerical calculations using these models with the experimental data indicate that friction on thin cracks and grain boundaries is the dominant attenuation mechanism for dry and brine‐saturated sandstones at low effective stresses for the frequencies tested. However, for brine‐saturated sandstones at moderately high effective stresses, fluid flow could play a more important role in ultrasonic S‐wave attenuation, depending on the pore structure of the sample.
Harmonic resonance structure and chaotic dynamics in the earth‐vibrator system1
Authors: Walker David
Published: April 2006

Source‐generated energy in seismic vibrator records includes ultraharmonics, subharmonics, ultra‐subharmonics and possibly chaotic oscillatory behaviour. Nonlinear behaviours can be modelled using a ‘hard‐spring’ form of the Duffing equation. Modelling indicates that a qualitatively similar harmonic resonance structure is present for a broad range of possible mathematical descriptions. Qualitative global system behaviours may be examined without knowledge of actual earth parameters. Non‐linear resonances become stronger, relative to fundamental sweep frequencies, as the driving force increases or damping decreases. System response energy levels are highest when non‐linear resonances are strong. The presence of chaotic energy can indicate the highest energy state of a system reponse. Field data examples are consistent with behaviours predicted by modelling. Conventional correlation and stack uses a fraction of the energy produced in the earth‐vibrator system. A correlation and filtering process that uses a representation of the source dynamics based on the system response can reduce signal degradation due to non‐linear resonance.
Laboratory technique for measurement of spectral induced polarization response of soil sampies1
Authors: Vanhala Heikki , Soininen Heikki
Published: April 2006

Laboratory measurements of soil samples are necessary to assess the effect of mineralogy, grain size distribution, moisture content, and electrolyte composition on the resistivity spectrum of soil material. Laboratory results are also required for the interpretation of field data. Induced polarization phenomena in glacial soils are poorly understood and so far no convenient laboratory techniques are available for its measurement. Coarse grain size and the need to measure unsaturated samples and to monitor the homogeneity of the sample require a sample holder–electrode construction that differs from those presented in Clay mineral Studies.

This study presents a spectral induced polarization laboratory system that is suitable for measuring fine‐ and coarse‐grained and both saturated and unsaturated soil samples. The noise caused by the electrode–electrolyte interface is studied in detail. It is shown that easy‐to‐use platinum or acid‐free steel potential electrodes are convenient over a broad frequency band ranging from 0.016Hz up to more than 1000 Hz. The laboratory experiments and comparisons between laboratory and field results also indicate that sampling and sample packing procedures have only a minor influence on the phase spectrum of glacial soils.
Monitoring subsurface changes over time with cross‐well electromagnetic tomographyt1
Authors: Alumbaugh David L. , Morrison H.F.
Published: April 2006

A fast imaging technique is developed to deduce the spatial conductivity distribution in the earth from low‐frequency (> 1 MHz) cross‐well electromagnetic measurements. A sinusoidally oscillating, vertically orientated, magnetic dipole employed as a source, and it is assumed that the scattering bodies are azimuthally symmetric about the source dipole axis. The use of this model geometry reduces the 3D vector problem to a more manageable 2D scalar form. Additional efficiency is obtained by using the Born series approximation which is derived from nonlinear integral equations that account for the scattered magnetic fields generated by inhomogeneities embedded in a layered earth. Stabilization of the inversion problem is accomplished through the use of bounding constraints and a regularization method which results in a smooth model that fits the data to the desired noise level.

The applicability of cross‐well electromagnetics for imaging and monitoring changes caused by subsurface processes has been tested by simulating plumes of conductive fluid with 2D models. The images that result from inverting these synthetic data indicate that the vertical resolution of the method is better than the horizontal, increasing the noise decreases the image resolution, and incorporating a priori knowledge in the form of positivity constraints improves the results. Although higher operating frequencies are usually associated with better resolution, frequencies as low as 100 Hz can produce acceptable images in simulated oilfield environments.

The imaging scheme has been applied to data collected during a salt‐water injection experiment at the Richmond Field Station test site in Richmond, California. Both the data and the resulting images clearly reveal the presence of the plume and indicate that it is migrating towards the north‐northwest rather than spreading symmetrically about the injection well. Applying the imaging code to synthetic data generated by a 3D sheet model verifies the interpretation of these results.
Accurate and efficient shot‐gather dip moveout processing in the log‐stretch domain1
Authors: Zhou B. , Mason I.M. , Greenhalgh S.A.
Published: April 2006

An accurate analytical expression for shot‐gather dip‐moveout (DMO) in the timespace log‐stretch domain has until now not been published. We present a simpler, alternative derivation of the exact DMO relationships of Blacket al. which correctly take account of the repositioning of the midpoint. A new computationally efficient frequency‐wavenumber(F‐K)DMO operator for shot profiles is then derived, based on these DMO relationships in the time‐space log‐stretch domain. The newly derived DMO operator is, unlike most other log‐stretch DMO operators) accurate for the full range of reflector dips. Along with other schemes which are performed in the log‐stretch domain, it offers considerable time savings over conventional DMO processing. We have compared numerically the impulse response of the new operator with those of a number of other shot‐gather DMO operators, and found it to be superior and well match to the theoretical elliptical DMO response.
Numerical modelling of airborne electromagnetic anomalies originating from low‐conductivity 3D bodies1
Authors: Peltoniemi Markku , Bärs Rainer , Newman Gregory A.
Published: April 2006

Responses of a multifrequency, multicoil airborne electromagnetic (AEM) system were modelled numerically for 3D electrical conductors embedded in a resistive bedrock and overlain by an overburden of low to moderate conductivity. The results cover a horizontal coplanar coil configuration and two frequencies, 7837 Hz and 51 250 Hz. The models studied are single or multiple, poor conductors (conductance lower than 0.1 S) embedded in a host rock of high but finite resistivity (5000 Ωm) and overlain by a layer of overburden with finite thickness and low to moderate conductivity (conductance up to 2 S).

On the basis of the modelling results, limits of detectability for poor conductors have been studied for the various model structures. The results indicate that the anomaly from a steeply dipping, plate‐like conductor will decrease significantly when the conductor is embedded in a weakly conductive host rock and is overlain by a conductive overburden. However, an anomaly is obtained, and its magnitude can even increase with increasing overburden conductivity or frequency. The plate anomaly remains practically constant when only the overburden thickness is varied. Changes in overburden conductivity will cause the plate‐anomaly values to change markedly. If the plate conductance is less than that of the overburden, a local anomaly opposite in sign to the normal type of anomaly will be recorded. Another major consequence is that conductors interpreted with free‐space models will be heavily overestimated in depth or underestimated in conductance, if in reality induction and current channelling in the host rock and overburden make even a slight contribution to the anomalous EM field.

The lateral resolution for the horizontal coplanar coil system was found to be about 1.7 times the sensor altitude. Similarly, the lateral extension of a horizontal conductive ribbon, required to reach the semi‐infinite (half‐space) behaviour, is more than three times the sensor altitude. Finally, screening of a steeply dipping plate, caused by a small, conductive horizontal ribbon, is much more severe than screening of the same plate by an extensive horizontal layer.
A new method for geoelectrical investigations underwater1
Authors: Baumgartner François
Published: April 2006

A new electrical method is proposed for determining the apparent resistivity of multi‐earth layers located underwater. The method is based on direct current geoelectric sounding principles. A layered earth model is used to simulate the stratigraphic target. The measurement array is of pole‐pole type; it is located underwater and is orientated vertically. This particular electrode configuration is very useful when conventional electrical methods cannot be used, especially if the water depth becomes very important. The calculated apparent resistivity shows a substantial quality increase in the measured signal caused by the underwater targets, from which little or no response is measured using conventional surface electrode methods. In practice, however, different factors such as water stratification, underwater streams or meteorological conditions complicate the interpretation of the field results. A case study is presented, where field surveys carried out on Lake Geneva were interpreted using the calculated apparent resistivity master‐curves.
Fluxes of carbon dioxide and water vapour over an undisturbed tropical forest in south‐west Amazonia
Authors: GRACE JOHN , LLOYD JON , MCINTYRE JOHN , MIRANDA ANTONIO , MEIR PATRICK , MIRANDA HELOISA , MONCRIEFF JOHN , MASSHEDER JON , WRIGHT IVAN , GASH JOHN
Published: April 2006

Carbon dioxide and water vapour fluxes were measured for 55 days by eddy covariance over an undisturbed tropical rain forest in Rondonia, Brazil. Profiles of CO2 inside the canopy were also measured.

 During the night, CO2 concentration frequently built up to 500 ppm throughout the canopy as a result of low rates of exchange with the atmosphere. In the early morning hours, ventilation of the canopy occurred.

 Ecosystem gas exchange was calculated from a knowledge of fluxes above the canopy and changes of CO2 stored inside the canopy. Typically, uptake by the canopy was 15 μmol m−2 s−1 in bright sunlight and dark respiration was 6‐7 μmol m−2 s−1 The quantum requirement at low irradiance was: 40 mol photons per mol of CO2.

 Bulk stomatal conductance of the ecosystem was maximal in the early morning (0.4‐1.0 mol m−2 s−1) and declined over the course of the day as leaf‐to‐air vapour pressure difference increased.
Global climate models and ‘dynamic’ vegetation changes
Authors: HENDERSON‐SELLERS A. , McGUFFIE K.
Published: April 2006

Models of global change must come to incorporate changes in terrestrial vegetation. Here we choose a 1‐ year meshing (coupling) period to link a global climate model to a well‐known biophysical representation of the continental surface by means of eleven vegetation functional types. This coupled model is used to answer two questions: Can a ‘standard’ GCM ‘cope' with sudden switches in continental characteristics?’ and Does the climate ‘care’ about the changing underlying vegetation? We find affirmative answers to both questions. Our results also suggest that those content to generate vegetation post facto from climate output have incomplete results.
Was low atmospheric CO2 during the Pleistocene a limiting factor for the origin of agriculture?
Authors: SAGE ROWAN F.
Published: April 2006

Agriculture originated independently in many distinct regions at approximately the same time in human history. This synchrony in agricultural origins indicates that a global factor may have controlled the timing of the transition from foraging to food‐producing economies. The global factor may have been a rise in atmospheric CO2 from below 200 to near 270 μol mol−1 which occurred between 15,000 and 12,000 years ago. Atmospheric CO2 directly affects photosynthesis and plant productivity, with the largest proportional responses occurring below the current level of 350 μol mol−1. In the late Pleistocene, CO2 levels near 200 μol mol−1 may have been too low to support the level of productivity required for successful establishment of agriculture. Recent studies demonstrate that atmospheric CO2 increase from 200 to 270 μol mol−1 stimulates photosynthesis and biomass productivity of C3 plants by 25% to 50%, and greatly increases the performance of C3 plants relative to weedy C4 competitors. Rising CO2 also stimulates biological nitrogen fixation and enhances the capacity of plants to obtain limiting resources such as water and mineral nutrients. These results indicate that increases in productivity following the late Pleistocene rise in CO2 may have been substantial enough to have affected human subsistence patterns in ways that promoted the development of agriculture. Increasing CO2 may have simply removed a productivity barrier to successful domestication and cultivation of plants. Through effects on ecosystem productivity, rising CO2 may also have been a catalyst for agricultural origins by promoting population growth, sedentism, and novel social relationships that in turn led to domestication and cultivation of preferred plant resources.
Past vegetation changes in the Brazilian Pantanal arboreal–grassy savanna ecotone by using carbon isotopes in the soil organic matter
Authors: VICTORIA REYNALDO LUIZ , FERNANDES FERNANDO , MARTINELLI LUIZ ANTONIO , DE CÁSSIA PICCOLO MARISA , DE CAMARGO PLINIO BARBOSA , TRUMBORE SUSAN
Published: April 2006

Measurements of the organic carbon inventory, its stable isotopic composition and radiocarbon content were used to deduce vegetation history from two soil profiles in arboreal and grassy savanna ecotones in the Brazilian Pantanal. The Pantanal is a large floodplain area with grass‐dominated lowlands subject to seasonal flooding, and arboreal savanna uplands which are only rarely flooded. Organic carbon inventories were lower in the grassy savanna site than in the upland arboreal savanna site, with carbon decreasing exponentially with depth from the surface in both profiles. Changes in 13C of soil organic matter (SOM) with depth differed markedly between the two sites. Differences in surface SOM 13C values reflect the change from C3 to C4 plants between the sites, as confirmed by measurements of 13C of vegetation and the soil surface along a transect between the upland closed‐canopy forest and lowland grassy savanna. Changes of 13C in SOM with depth at both sites are larger than the 3–4 per mil increases expected from fractionation associated with organic matter decomposition. We interpret these as recording past changes in the relative abundance of C3 and C4 plants at these sites. Mass balances with 14C and 13C suggest that past vegetational changes from C3 to C4 plants in the grassy savanna, and in the deeper part of the arboreal savanna, occurred between 4600 and 11 400 BP, when major climatic changes were also observed in several places of the South American Continent. The change from C4 to C3, observed only in the upper part of the arboreal savanna, was much more recent (1400 BP), and was probably caused by a local change in the flooding regime.
Plant growth and reproduction along CO2 gradients: non‐linear responses and implications for community change
Authors: ACKERLY D.D. , BAZZAZ F.A.
Published: April 2006

The effects of rising atmospheric CO2 concentrations on natural plant communities will depend upon the cumulative responses of plant growth and reproduction to gradual, incremental changes in climatic conditions. We analysed published studies of plant responses to elevated CO2 to address whether reproductive and total biomass exhibit similar enhancement to elevated vs. ambient CO2 concentrations, and to assess the patterns of plant response along gradients of CO2 concentrations. In six annual plant species, mean enhancement at double ambient vs. ambient CO2 was 1.13 for total biomass and 1.30 for reproductive biomass. The two measures were significantly correlated, but there was considerable scatter in the relationship, indicating that reproductive responses cannot be consistently predicted from enhancement of total biomass. Along experimental CO2 gradients utilizing three concentrations, there was a great diversity of response patterns, including positive, negative, non‐monotonic and non‐significant (flat) responses. The distribution of response patterns differed for plants grown in stands compared to those grown individually. Positive responses were less frequent in competitive environments, and non‐monotonic responses were more frequent. These results emphasize that interpolation of plant response based on enhancement ratios measured at elevated vs. ambient CO2 concentrations is not sufficient to predict community responses to incremental changes in atmospheric conditions. The consequences of differential response patterns were assessed in a simulation of community dynamics for four species of annual plants. The model illustrates that the final community composition at a future point in time depends critically on both the magnitude and the rate of increase of atmospheric CO2.
Land‐use change and the carbon cycle
Authors: HOUGHTON R. A.
Published: April 2006

Changes in land use between 1850 and 1980 are estimated to have increased the global areas in croplands, pastures, and shifting cultivation by 891, 1308, and 30 × 106ha, respectively, reducing the area of forests by about 600 × 106ha, releasing about 100 PgC to the atmosphere, and transferring about 23 PgC from live vegetation to dead plant material and wood products. Another 1069 × 106ha are estimated to have been logged during this period, and the net release of carbon from the combined processes of logging and regrowth contributed 23 PgC to the 100‐PgC release. Annual rates of land‐use change and associated emissions of carbon have decreased over the last several decades in temperate and boreal zones and have increased in the tropics. The average release of carbon from global changes in land use over the decade of the 1980s Is estimated to have been 1.6 ± 0.7 PgC y−1almost entirely from the tropics. This estimate of carbon flux is higher than estimates reported in recent summaries because it is limited here to studies concerned only with changes in land use. Other recent analyses, based on data from forest inventories, have reported net accumulations of carbon as high as 1.1 PgC y−1in temperate and boreal zones. Because the accumulation of carbon in forests may result from natural processes unrelated to land‐use change, estimates based on these inventories should be distinguished from estimates based on changes in land use. Both approaches identify terrestrial sinks of carbon. The argument is made here, however, that differences between the two approaches may help identify the location and magnitude of heretofore ‘missing’ sinks. Before different estimates can be used in this way, analyses must consider similar geographical regions and dates, and they must account for the accumulation and loss of carbon in forest products in a consistent fashion.
Effects of temperature on aphid phenology
Authors: ZHOU XILONG , HARRINGTON RICHARD , WOIWOD IAN P. , PERRY JOE N. , BALE JEFFREY S. , CLARK SUZANNE J.
Published: April 2006

Daily samples between 1964 and 1991 from suction traps throughout Great Britain were used to study the migration phenologies of five aphid species: Brachycaudus helichrysi, Elatobium abietinum, Metopolophium dirhodum, Myzus persicae and Sitobion avenae, and their relationship with temperature. Regression relationships have been established between characteristics of aphid phenology and temperature, latitude and longitude for each species. There were differences between species in the period for which temperature was most strongly associated with aphid phenology. The study indicates that temperature, especially winter temperature, is the dominant factor affecting aphid phenology, for all five species. A 1 °C increase in average winter temperature advanced the migration phenology by 4–19 days depending on species. Effects of temperature on the aphid phenology are similar between holocyclic and anholocyclic species, unlike the effects of temperature on date of first flight record which have been previously shown to be important only in anholocyclic species.
The temporal response of forest ecosystems to doubled atmospheric CO2 concentration
Authors: MCMURTRIE ROSS E. , COMINS HUGH N.
Published: April 2006

Vegetation responses to high [CO2] include both direct photosynthetic effects and indirect effects associated with various plant and soil feedbacks. Synthesis of these direct and indirect effects requires ecosystem process models describing the cycling of carbon and essential mineral nutrients through plants and soils. Here we use the ecosystem model G'DAY to investigate responses to an instantaneous doubling of [CO2]. The analysis indicates that the magnitude and even direction of the growth response to high [CO2] can vary widely on different timescales, because responses on different timescales are determined by different ecosystem‐level feedbacks and hence by different sets of key model parameters. Of particular importance are parameters describing the flexibility of plant and soil nitrogen to carbon (N:C) ratios; large responses occur if N:C ratios decline significantly at high [CO2], with little or no response if N:C ratios are inflexible. According to G'DAY, the CO2‐response changes over time because responses on longer timescales are dictated by the N:C ratios of less rapidly cycled organic matter.
Archival photographs show no climate‐induced changes in woody vegetation in the Sudan, 1943–1994*
Authors: SCHLESINGER WILLIAM H. , GRAMENOPOULOS NICHOLAS
Published: April 2006

An archive of satellite and aircraft photographs of the western Sudan showed no longterm (1943–1994) trends in the abundance of trees despite several decades of recent drought in this region. These data extend the extant historical record of vegetation change in the African Sahel, where recent fluctuations in vegetation greenness have been monitored with the NOAA Advanced Very High Resolution Radiometer since 1980. Despite substantial population turnover, woody vegetation is not yet indicative of the recent climate changes in this region.
Annual cycles of water vapour and carbon dioxide fluxes in and above a boreal aspen forest
Authors: BLACK T. A. , DEN HARTOG G. , NEUMANN H. H. , BLANKEN P.D. , YANG P.C. , RUSSELL C. , NESIC Z. , LEE X. , CHEN S. G. , STAEBLER R. , NOVAK M. D.
Published: April 2006

Water vapour and CO2 fluxes were measured using the eddy correlation method above and below the overstorey of a 21‐m tall aspen stand in the boreal forest of central Saskatchewan as part of the Boreal Ecosystem‐Atmosphere Study (BOREAS). Measurements were made at the 39.5‐m and 4‐m heights using 3‐dimensional sonic anemometers (Kaijo‐Denki and Solent, respectively) and closed‐path gas analysers (LI‐COR 6262) with 6‐m and 4.7‐m long heated sampling tubing, respectively. Continuous measurements were made from early October to mid‐November 1993 and from early February to late‐September 1994. Soil CO2 flux (respiration) was measured using a LI‐COR 6000‐09 soil chamber and soil evaporation was measured using Iysimetry.

The leaf area index of the aspen and hazelnut understorey reached 1.8 and 3.3, respectively. The maximum daily evapotranspiration (E) rate was 5–6 mm d−1. Following leaf‐out the hazelnut and soil accounted for 22% of the forest E. The estimated total E was 403 mm for 1994. About 88% of the precipitation in 1994 was lost as evapotranspiration.

During the growing season, the magnitude of half‐hourly eddy fluxes of CO2 from the atmosphere into the forest reached 1.2 mg CO2 m−2 s−1 (33 μmol C m−2 s−1) during the daytime. Downward eddy fluxes at the 4‐m height were observed when the hazelnut was growing rapidly in June and July. Under well‐ventilated night‐time conditions, the eddy fluxes of CO2 above the aspen and hazelnut, corrected for canopy storage, increased exponentially with soil temperature at the 2‐cm depth. Estimates of daytime respiration rates using these relationships agreed well with soil chamber measurements. During the 1994 growing season, the cumulative net ecosystem exchange (NEE) was ‐3.5 t C ha−1 y−1 (a net gain by the system). For 1994, cumulative NEE, ecosystem respiration (R) and gross ecosystem photosynthesis (GEP = R ‐ NEE) were estimated to be ‐1.3, 8.9 and 10.2 t C ha−1 y−1 respectively. Gross photosynthesis of the hazelnut was 32% of GEP.
Carbon dioxide concentrations within forest canopies—variation with time, stand structure, and vegetation type
Authors: BUCHMANN NINA , KAO WEN–YUAN , EHLERINGER JAMES R.
Published: April 2006

Vertical CO2 profiles (between 0.02 and 14.0 m) were studied in forest canopies of Pinus contorta, Populus tremuloides, and in a riparian forest with Acer negundo and Acer grandidentatum during two consecutive growing seasons. Profiles, measured continuously during 1‐ to 13‐day periods in four to five stands differing in overstorey canopy area index (CAI < 4.5; including leaves, branches and stems), were well stratified, with highest [CO2] just above the forest floor. Canopy [CO2] profiles were influenced by stand structure (CAI, presence of understorey vegetation), and were highly dependent on vegetation type (deciduous and evergreen). A doubling of CAI in Acer spp. and P. tremuloides stands did not show an effect on upper canopy [CO2], when turbulent mixing was high. However, increasing understorey biomass in Acer spp. stands had a profound effect on lower canopy [CO2]. In open stands with a vigorous understorey layer, higher soil respiration rates were offset by increased understorey gas exchange, resulting in [CO2] below those of the convective boundary layer (CBL). Midday depletions up to 20 ppmv below CBL values could be frequently observed in deciduous canopies. In evergreen canopies, [CO2] stayed generally above the CBL background values, [CO2] profiles were more uniform, and gradients were smaller than in deciduous stands with similar CAI. Seasonal changes of canopy [CO2] reflected changes in soil respiration rates as well as plant phenology and gas exchange of both dominant tree and understorey vegetation. Seasonal patterns were less pronounced in evergreen than in deciduous forests.
UNDERGROUND DEVELOPMENT AND RESERVES OF GRASSES A REVIEW
Authors: Weinmann H.
Published: April 2006

“The roots of plants are the least known, least understood and least appreciated part of the plant.”—Weaver and Bruner (125).
GRAZING MANAGEMENT FOR SEED PRODUCTION IN LEAFY STRAINS OF GRASSES
Authors: Green J. O. , Evans T. A.
Published: April 2006

Leafy strains of five grasses were grown for seed and subjected to various cattle grazing treatments between October and April for three harvest years. The grasses were: S.143 cocksfoot, S.215 meadow fescue, S.170 tall fescue, S.59 red fescue and S.23 perennial ryegrass. All but S.59 red fescue (row crop) were studied as row and broadcast crops. The plots were sown under an arable silage crop and received top dressings of nitrogenous fertiliser every year. Yield of seed, and also quantity of herbage in winter, were measured.

October grazing in the seeding year reduced the first crop of seed in all species except ryegrass. Grazing in December improved the yield of meadow fescue throughout the experiment, and of cocksfoot, tall fescue and red fescue after the first year. Several factors might operate to bring about this effect; suggestions are made for further investigation. Repeated grazing from December to March tended to reduce vigour, and so to offset the advantage of removing autumn‐grown herbage. Grazing at intervals from December to late April seriously reduced yield in all species. Tall fescue and red fescue, early flowering species, were most seriously affected, meadow fescue and perennial ryegrass least. Cocksfoot and tall fescue yielded more seed when grown in 2‐ft. rows than when broadcast. Meadow fescue and perennial ryegrass did not. The yield of meadow fescue was less affected by adverse conditions than cocksfoot.
THE SULPHUR CYCLE IN GRASSLAND SOILS
Authors: Walker T. W.
Published: April 2006

In well drained grassland soils, most of the sulphur occurs in the organic matter and the average C : N : S ratio in the A horizon of normal soils is probably 100 : 8 : 1. In the absence of outside sources of sulphur, grasses in a grass/legume association would be almost completely dominant as they compete intensively with legumes for sulphur and could utilise almost all the mineral nitrogen and sulphur made available by the mineralisation of the organic matter. Legumes are thus dependent on outside sources of sulphur without which they will fix little nitrogen. The amount of sulphur needed will depend on the factors governing the amount of nitrogen fixed—climate, species, soils, management—it will be roughly a tenth to a fifteenth of the nitrogen fixed and will vary between 1–2 lb. per acre where the only addition of nitrogen to the soil is from rain or by non‐symbiotic fixation to about 60 lb. per acre under the best New Zealand pastoral conditions. In the absence of fertiliser sulphur, the atmosphere is the most significant, but a highly variable, source. An interesting situation arises in New Zealand where in one rather vigorous climatic zone where nitrogen fixation by legumes is limited to about 100 lb. nitrogen per acre per annum, so little sulphur comes from the atmosphere (probably less than 1 lb. per acre) that sulphur must be applied to enable clovers to make any appreciable growth. Under more favourable conditions where clovers may fix 600 lb. nitrogen per acre it is calculated that some 50 lb. of sulphur is obtained from natural sources and further responses may be obtained from fertiliser sulphur. Less sulphur may be needed when grass/legume associations are grazed than when they are cut for conservation, owing to the retum of sulphur in the urine—but much must depend on which system of utilisation most depresses clover growth and nitrogen fixation. The fate of sulphur when herbage is grazed is closely parallel to that of nitrogen; most of it is excreted in the urine as sulphate. Sulphate (even if applied as gypsum) may be readily lost by leaching from the A horizon and care must be exercised in the choice of forms of sulphur, rates and times of application.
STUDIES ON THE ROOT DEVELOPMENT OF HERBAGE PLANTS
Authors: Williams T. E. , Baker H. K.
Published: April 2006

Various methods of root sampling are reviewed and discussed in relation to the type of information required. The root sampling techniques at the Grassland Research Institute are described and examples of sampling errors are given. Details of a root washing machine are given.
EFFECT OF DEFOLIATION AND SOIL MOISTURE ON GRASSLAND RE‐GROWTH
Authors: Jäntti August , Heinonen Reijo
Published: April 2006

The results of field experiments with leys dominated by Festuca pratensis and Dactylis species appear to concur with the theories proposed by Kramer and Jäntti. Complete defoliation, while the soil moisture was at or near permanent wilting percentage down to about 40 cm. depth, arrested growth almost completely but the growth rate of plants with assimilating parts left was 70 to 90 per cent of the corresponding rate on moist soil. The interaction of defoliation and soil moisture, however, seemed to be confined to cases where defoliation was practically complete. When a 4 cm. stubble was left the effect of drought was relatively no more strong than in swards cut to only 12 cm. Defoliation alone causes heavy crop reductions even in moist soil, and these reductions are evidently more important quantitatively than those resulting from the interaction with soil moisture.
STUDIES ON THE EXTENSION OE THE GRAZING SEASON I.
Authors: Corbett J. L.
Published: April 2006

Plots were sown broadcast with ryegrass, cocksfoot or timothy and were strip‐grazed at various times during three successive winters by store cattle maintained almost entirely on foggage. In the first winter the plots were rested from 2 September. Each was sampled when required for grazing and the mean organic‐matter yield was 2020 Ib. per acre containing 17.5% crude protein. In the two following years, when rested from 15 July and 10 August, November yields were 4340 Ib. (11.8% crude protein) and 3003 Ib. (16.0% crude protein), respectively. Ryegrass yields were 15–30% higher than timothy and 25–50% higher than cocksfoot. Losses during winter due to rotting were related to botanical characteristics and were 40% for ryegrass, 30% for timothy and 10–20% for cocksfoot. Cocksfoot was the most suitable for winter‐grazing since it had the highest stock‐carrying capacity at all times. This was due mainly to high consumption of ryegrass and timothy, not affecting live‐weights, and increasingly poor utilization of the ryegrass produced. It is emphasized that grazing animals should be used when evaluating pastures. Foggage production is considered as a method of herbage conservation and in relation to whole‐year pasture output.
STUDIES ON THE ROOT DEVELOPMENT OF HERBAGE PLANTS
Authors: Baker H. K.
Published: April 2006

The influence of defoliation on the root, stubble and herbage weights of perennial ryegrass during establishment was studied on spaced plants in the greenhouse and field.

In the greenhouse trial the rate of root elongation was reduced by a single defoliation. In both the field and greenhouse, cutting reduced the number of roots and tillers per plant but increased the number of roots per tiller. A few weeks after defoliating plants in the field there was a lower root weight on the cut plants than on the uncut. Eventually the influence of a single cut disappeared, but if the cutting was in the laie summer or autumn the plants commenced the winter with a smaller amount of root and stubble, and this appeared to have a deleterious effect on the earliest spring growth.

Herbage growth in March and April was positively correlated with both root and stubble weights in the previous November.

As the number of cuts during the establishment period (March‐November) was increased from 0–4 the root and stubble weight per plant progressively decreased.

The root and stubble weights decreased during the winter.
THE VALUE OF THE FIBROUS RESIDUE FROM LEAF PROTEIN EXTRACTION AS A FEEDING‐STUFF FOR RUMINANTS
Authors: Raymond W. F. , Harris C. E.
Published: April 2006

The production of a fibrous material as a residue from the process of extracting a protein concentrate from fresh crops is described and the value of this material as a coarse feed for ruminants has been studied in five digestibility experiments with sheep. In these the digestibilities of the residues have been compared with the digestibilities of the corresponding fresh crops. The fibre residues, both fresh and artificially dried, were readily consumed by sheep.

The average digestibilities of the dry matter and organic matter in the fibre residues were respectively 6.4 units and 5.6 units lower than in the corresponding fresh crops. The organic matter content of the fibre residues was higher than that of the fresh crops. Because of this the residues contained 94% as much digestible organic matter per lb. of feed dry matter as did the unprocessed crops. The dry matter of the fibre residues contained from 52%–60% of digestible organic matter and from 1.32% to 2.2% of digestible nitrogen. In respect to the former they are equivalent to medium grade hay, but are superior to this in digestible nitrogen content.

The fibre residues can be readily dried but artificial drying would be unlikely to be economic in commercial practice. Residues have been successfully ensiled, using either molasses or mineral acids as additives but the silage has been found to be quite unpalatable to all classes of ruminants. It is suggested that the fibre residues would best be utilized by feeding directly to stock in yards adjacent to the protein extraction machinery.
STUDIES ON THE EXTENSION OF THE GRAZING SEASON
Authors: Corbett J. L.
Published: April 2006

In a small plot trial good yields of foggage of satisfactory botanical composition with cocksfoot dominant were produced from a mixed‐species pasture after it had been cut for silage in spring and again in summer. Production in the following year was satisfactory. The advantages of using ordinary pastures for winter grazing, especially if this occurs only during their last winter before ploughing, are discussed. From a study of various autumn treatments it is concluded that the optimum management for foggage production in the north‐east of Scotland is to close fields on or near 10 August when 3 cwt. nitro‐chalk per ac. should be applied; a higher rate (6 cwt. per ac), though it increased yields and percentage crude protein immediately, and also during the subsequent summer, conferred no benefits of practical importance. Effects of K fertilizer applications were negligible. Closing as late as the beginning of September gave smaller but useful yields of a higher protein foggage and the sward was less cocksfoot‐dominant. Autumn closing and fertilizer treatments did not affect foggage wastage during winter, which averaged 14 per cent of the initial organic‐matter yield; the percentage of crude protein in standing foggage rose.
SPACED‐PLANT TRIALS AT EAST CRAIGS
Authors: Thomson J. R. , Seaton R. D.
Published: April 2006

In spaced‐plant trials in Scotland, nineteen strains of Dactylis glomerata were assessed for the following characters: habit of growth in early spring, at ear emergence and at flowering; date of ear emergence; length of stem and weight of plant at anthesis; amount of aftermath shooting.

The following characters in a strain were found to be related to its date of ear emergence: habit of growth at ear emergence and at flowering; stem length. No relation was found between date of ear emergence and plant weight, aftermath shooting or spring growth habit. The strains are allotted to grades on the basis of each character and, in an overall classification, all except one fall into two main groups on the basis of relative earliness and lateness.
A POINT‐QUADRAT METHOD FOR THE DESCRIPTION OF PASTURE IN TERMS OF HEIGHT AND DENSITY
Authors: Spedding C. R. W. , Large R. V.
Published: April 2006

The definition of pasture height is discussed and it is suggested that a meaningful and objective measurement of height must be related to the distribution of density. A point‐quadrat method for determining such a “height index” is described and the uses and limitations of the method are discussed.
SOME EFFECTS ON THE YIELDS OF RYEGRASS STRAINS OF VARYING THE GROWING TECHNIQUE AND THE CONDITIONS OF MANAGEMENT
Authors: Lazenby Alec
Published: April 2006

The effects are reported of varying the growing technique, and the conditions of management, on green and air‐dry yields of herbage from five strains of ryegrass during 1952 and 1953. All strains were grown in three ways: as spaced plants, in drill‐rows and in stands broadcast with white clover. There were two experiments, one managed for hay and aftermath, the other cut more frequently.

In both experiments the broadcast plots reached their peak of herbage production first; the spaced plants took longest. There were considerable differences in the seasonal distribution of yields from the different growing techniques during the first harvest year. In 1953, the differences were smaller but the secondary annual peak of herbage production observed in the broadcast plots was not detected in the spaced plants.

The total annual production per unit area was greatest from the broadcast, and least from spaced‐plant plots. Yields on certain occasions, however, were greatest from spaced plants and least from broadcast areas.

The effects of varying the conditions of management were greatest on population samples sown broadcast and least on those growing as spaced plants, their reaction when grown in drills being intermediate.

Differences in plant population in the various growing techniques are discussed in relation to the above results.
SPACED‐PLANT TRIALS AT EAST CRAIGS
Authors: Thomson J. R. , Keppie J. L.
Published: April 2006

Four foreign strains of Lolium perenne L. are classified by comparing them with established strains on the basis of their performance in spaced‐plant trials in Scotland in the years 1953–5.