bluuebunny/crossref_metadata_2025_split huggingface dataset:
Species diversity and ecosystem response to carbon dioxide fertilization: conclusions from a temperate forest model
Authors: BOLKER B.M. , PACALA S.W. , BAZZAZ F.A. , CANHAM C D. , LEVIN S.A. 
Published: April 2006

AbstractThis paper explores how the response of a temperate forest ecosystem to climate change might depend on species diversity and community change. In particular, we look at the dynamics of a model of temperate forest growth under doubled CO2. We combine a detailed, field‐calibrated model of forest dynamics (Pacala et al 1993) with greenhouse data on the range of seedling biomass growth response to doubled CO2 concentrations (Bazzaz et al. 1990; Bazzaz & Miao 1993). Because total ecosystem response to climate change depends delicately on many environmental variables other than CO2, we isolate the effects of community change by comparing runs of the regular model, allowing dynamic community change, with runs of a reduced model that holds species composition static by using a single tree species with average parameters. Simulations that allowed community change instead of holding species composition constant showed a roughly 30% additional increase in total basal area over time scales of 50‐150 years. Although the model omits many possible feedbacks and mechanisms associated with climate change, it suggests the large potential effects that species differences and feedbacks can have in ecosystem models and reinforces the possible importance of diversity to ecosystem function (Naeem et ai 1994; Tilman & Downing 1994) over time scales within the planning horizon for global change policy.
Productivity and water use of wheat under free‐air CO2 enrichment
Authors: KIMBALL BRUCE A. , PINTER PAUL J. , GARCIA RICHARD L. , LaMORTE ROBERT L. , WALL GERARD W. , HUNSAKER DOUGLAS J. , WECHSUNG GABRIELE , WECHSUNG FRANK , KARTSCHALL§ THOMAS 
Published: April 2006

AbstractA free‐air CO2 enrichment (FACE) experiment was conducted at Maricopa, Arizona, on wheat from December 1992 through May 1993. The FACE apparatus maintained the CO2 concentration, [CO2], at 550 μmol mol−1 across four replicate 25‐m‐diameter circular plots under natural conditions in an open field. Four matching Control plots at ambient [CO2] (about 370 μmol mol−1) were also installed in the field. In addition to the two levels of [CO2], there were ample (Wet) and limiting (Dry) levels of water supplied through a subsurface drip irrigation system in a strip, split‐plot design.Measurements were made of net radiation, Rn; soil heat flux, Go; soil temperature; foliage or surface temperature; air dry and wet bulb temperatures; and wind speed. Sensible heat flux, H, was calculated from the wind and temperature measurements. Latent heat flux, λET, and evapotranspiration, ET, were determined as the residual in the energy balance. The FACE treatment reduced daily total Rn by an average 4%. Daily FACE sensible heat flux, H, was higher in the FACE plots. Daily latent heat flux, λET, and evapotranspiration, ET, were consistently lower in the FACE plots than in the Control plots for most of the growing season, about 8% on the average.Net canopy photosynthesis was stimulated by an average 19 and 44% in the Wet and Dry plots, respectively, by elevated [CO2] for most of the growing season. No significant acclimation or down regulation was observed. There was little above‐ground growth response to elevated [CO2] early in the season when temperatures were cool. Then, as temperatures warmed into spring, the FACE plants grew about 20% more than the Control plants at ambient [CO2], as shown by above‐ground biomass accumulation. Root biomass accumulation was also stimulated about 20%. In May the FACE plants matured and senesced about a week earlier than the Controls in the Wet plots. The FACE plants averaged 0.6 °C warmer than the Controls from February through April in the well‐watered plots, and we speculate that this temperature rise contributed to the earlier maturity. Because of the acceleration of senescence, there was a shortening of the duration of grain filling, and consequently, there was a narrowing of the final biomass and yield differences. The 20% mid‐season growth advantage of FACE shrunk to about an 8% yield advantage in the Wet plots, while the yield differences between FACE and Control remained at about 20% in the Dry plots.
El Niño and tree growth near Jerusalem over the last 20 years
Authors: YAKIR DAN , LEV‐YADUN SIMCHA , ZANGVIL AVRAHAM 
Published: April 2006

AbstractA strong correlation is observed between an El Niño index (anomalies in tropical Pacific sea surface temperature) and rainfall in the Judean foothills near Jerusalem over the past 20 years. These relationships clearly influenced the growth of local pine trees, as reflected in the width of their annual tree rings. The ability to predict El Niño events about a year in advance lend a special significance to relationships reported here for ecology, agriculture and water management in this climatic transition zone. To help explain the observed, long‐range teleconnection we propose a possible mechanism based on a newly identified direct cloud connection between equatorial Africa (more directly affected by El Niño) and the Southeastern Mediterranean shoreland. The penetration and contribution of the moisture current from equatorial Africa to this region may depend on a shift in the usual rain generating moisture currents to southwesterly trajectories (passing over north Africa). The occurrence of such shifts is supported by the observed decrease in the mean 18O content of the local precipitation during El Nino winters.
Elevated CO2 decreases seed germination in Arabidopsis thaliana
Authors: ANDALO CHRISTOPHE , GODELLE BERNARD , LEFRANC MADELEINE , MOUSSEAU MARIANNE , TILL‐BOTTRAUD IRÉNE 
Published: April 2006

AbstractThe impact of elevated [CO2] on seed germination was studied in different genotypes of Arabidopsis thaliana from natural populations. Two generations of seeds were studied: the maternal generation was produced in the greenhouse (present‐day conditions), the offspring generation was produced in two chambers where the CO2 concentration was either the present atmospheric concentration (about 350 ppm) or elevated (700 ppm). The seeds were tested for proportion of germinated seeds and mean germination time in both chambers to study the impact of elevated [CO2] during seed production and germination.Elevated [CO2] during maturation of seeds on the mother‐plants decreased the proportion of germinated seeds, while elevated [CO2] during germination had no effect on the proportion of germinated seeds. However, when seeds were both produced and germinated under elevated [CO2] (situation expected by the end of next century), germination was slow and low.Moreover, the effect of the [CO2] treatment differs among genotypes of Arabidopsis: there is a strong treatment × genotype interaction. This means that there is ample genetic variance for a selective response modiying the effects of high levels of [CO2] in natural populations of Arabidopsis thaliana. The outcome at the community level will depend on what seeds are available, when they germinate and the resulting competition following germination.
Appropriate controls in outdoor UV‐B supplementation experiments
Authors: NEWSHAM K.K. , McLEOD A.R. , GREENSLADE P.D. , EMMETT B.A. 
Published: April 2006

Abstract Quercus robur L. saplings were exposed in an outdoor experiment to supplemental levels of UV‐8 (280–315 nm) radiation using treatment arrays of cellulose diacetate‐filtered fluorescent lamps that also produce UV‐A (315–400 nm) radiation. Saplings were also exposed to UV‐A radiation alone using control arrays of the same lamps filtered with polyester and to ambient levels of radiation, using arrays of unenergized lamps. The UV‐B treatment was modulated to maintain a 30% elevation above the ambient level of UV‐B radiation, measured by a broad‐band sensor weighted with an erythemal action spectrum. Saplings exposed to UV‐B radiation beneath treatment arrays developed thicker leaves than those beneath ambient and control arrays. Despite the fact that supplemental levels of UV‐A radiation were only a small percentage of ambient levels, apparent UV‐A effects were also recorded. Significant increases in sapling height, lammas shoot length and herbivory by chewing insects were observed under treatment and control arrays, relative to ambient, but there were no differences between the responses of saplings under treatment and control. These data imply that supplemental UV‐A radiation or other effects associated with energised lamps can significantly affect plant growth parameters and herbivory in outdoor studies. We conclude that the results from current outdoor UV‐B supplementation experiments that lack control exposures using polyester‐filtered lamps need to be interpreted with caution and that future supplementation experiments should include appropriate controls.
THE RENOVATION OF DOWNLAND PERMANENT PASTURE II.
Authors: Norman M. J. T. , Green J. O. 
Published: April 2006

An experiment, A, involving dates and methods of application of 2,4‐D (amine) as a preliminary treatment in the renovation of a poor downland permanent pasture, followed by surface cultivations and sowing of S.24 perennial ryegrass and S.100 white clover, was carried out at Hurley between 1953 and 1955.In spite of initial differences in the establishment of S.24 and S.100, pre‐treatment with herbicide had no effect upon the cover of sown and unsown perennial ryegrass and white clover two years later. At this date, perennial ryegrass contributed one‐quarter and one‐eighth, and white clover one‐third and one‐quarter, to the total cover of renovated and unrenovated plots respectively.The increase in dry‐matter yield resulting from renovation was approximately 10 per cent. This was considered small in relation to the estimated improvement in yield brought about by grazing management and manuring in the course of the trial.In experiment B, plots receiving herbicide were given differential management and manurial treatments after spraying in an attempt to control the ingress of undesirable creeping grasses. The results indicated that this ingress could be checked by close grazing soon after spraying.
COMPARATIVE PRODUCTIVITY OF 27 STRAINS OF GRASS IN THE WEST OF SCOTLAND
Authors: Hunt I. V. 
Published: April 2006

Seasonal productivity from plots of 27 strains of the principal grass species has been compared at Auchincruive over two seasons by a cutting technique. The following conclusions are reached:Peak growth is limited to a short period before the first week in June. Extension at peak‐growth level into the summer gap is not possible by the use of any of these grass strains grown alone.The provision of grass for one cow per acre is possible for up to 142 days by the combination of strains.Extension into the autumn can be achieved by conserving second‐peak growth, which does not mature to the same extent as the first‐peak growth.In combining strains with advantageous growth periods due regard must be paid to their growth at other periods, which may be particularly low.Combination of many strains is not likely to achieve as good a result as the use of 2, or at most 3, well chosen strains.
RED CLOVER SEED STORAGE FOR 23 YEARS
Authors: Evans Gwilym 
Published: April 2006

The moisture content of red clover seed proved to be the most important single factor governing its longevity. Life was conserved considerably better in a heated room, on account of its lower relative humidity, than in an unheated granary.Low temperature (32°–41°F.) was shown to be very beneficial for maintaining viability when the moisture content was excessive (10.32 per cent). By replacing the air in the containers with dry CO2 longevity was increased.A combination of low moisture content, cold storage and replacement of air by dry CO2 enabled red clover seed to germinate 71 per cent after 23 years’ storage and produce vigorous seedlings.Purple and yellow colours may be retained in a considerable proportion of a red clover seed stock long after all the seeds are dead.
THE VIABILITY OVER A PERIOD OF FIFTEEN YEARS OF SEVERELY DRIED RYEGRASS SEED
Authors: Evans Gwilym 
Published: April 2006

Perennial ryegrass seed was dried at temperatures from 50°C to 120°C, the increases of 10°C being made regularly at intervals of 3 hours. The figures for germination capacity obtained immediately after treatment indicated that a lethal zone had been reached with final temperatures above 100°C and moisture contents reduced to 0.09 and 0.00 per cent.It was shown that heat drying to as low as 0.66 per cent moisture at a final temperature of 100°C for 3 hours does not injure the germination capacity over a period of seven years, but after 15 years a greater loss in viability appears than in seed treated less severely. Germination energy figures (6‐days’ test) rather than germination capacity are a more reliable guide to optimum temperatures, duration of heating, and moisture content in the drying of seed for long‐period storage.The most favourable treatment in this series was found to be heating the seed gradually to a maximum temperature of 90°C for 3 hours with a reduction of moisture content to 1.62 per cent. Seed thus treated showed 81 per cent germination after 15 years; for the last eight years the bottles were stored in a cold room, after replacing the air in them with nitrogen.
STUDIES IN CALF MANAGEMENT
Authors: Alder F. E. , Chambers D. T. 
Published: April 2006

Systems of calf grazing were compared in preliminary experiments during 1954 and 1955. Hereford colour‐marked beef calves in the post‐weaning stage were used, all calves having been reared on the nurse‐cow system in loose boxes.The results indicate that autumn‐ and winter‐bom calves can make good progress at pasture during their first summer, husk‐free ground being one of the most important requirements in the production of well‐grown calves.
THE YIELDS OF PURE SOWN PLOTS OF EIGHT WHITE CLOVER STRAINS UNDER CUTTING
Authors: Davies W. Ellis 
Published: April 2006

Eight strains of white clover were compared under a cutting treatment over a three‐year period. The medium‐leaved, persistent strains S.100, S.100 Nomark, Kersey, New Zealand CM. and P.P. generally gave the highest yield of clover, but this was counterbalanced by an increased yield of unsown species in the plots of wild white clovers S.184 and Kent.The unsuitability of Ladino clover for British conditions was shown by its lack of persistency and poor yield. The new strain S.100 Nomark gave a similar total yield to S.100.
THE LOCAL INFLUENCE OF CATTLE DUNG AND URINE UPON THE YIELD AND BOTANICAL COMPOSITION OF PERMANENT PASTURE
Authors: Norman M. J. T. , Green J. O. 
Published: April 2006

A study was made of the local effects on yield and botanical composition of the herbage of cattle dung and urine applied to permanent pasture as simulated defaecations and urinations.A single application of urine had a negligible effect upon botanical composition. In the 2‐ft.‐diameter circle around dung patches there was an increase in cocksfoot, creeping bent, red fescue and white clover, and a decrease in herbs.Urine patches were neglected by grazing stock for short periods only. Herbage around dung patches was neglected for a period varying from 13–18 months. The effect of this neglect was to restrict the spread of white clover around dung patches in comparison with similar plots kept short by cutting.Yield response to urine in the area of deposition lasted for two cuts following application, response to dung for four cuts. An increase in crude‐protein content of the herbage was recorded only in samples taken one month after application of dung or urine, and not later.Increases in crude‐protein yield following spring applications of dung or urine were greater than those following autumn applications. The inferiority of autumn applications may be attributed to winter leaching of nitrogen.
A STUDY OF THE INFLUENCE OF NITROGEN ON THE ROOT WEIGHT AND NODULATION OF WHITE CLOVER IN A MIXED SWARD
Authors: Young Dorothy J. B. 
Published: April 2006

Experiments are described in which a study was made of the top growth, root weight, nodule number, and type of nodules of white clover growing in a grass sward in the field. Soil cores were taken and the clover root‐system examined after removal of soil by washing.The most important factor governing the total number of nodules and the number of large (2 mm. or more in length) nodules under the sward was the amount of clover root‐material present.Nitrogenous fertilisers and the return of dung and urine by grazing sheep reduced the amount of clover root‐weight and consequently the number of nodules found under the pasture. 36 1b. of nitrogen applied in the early spring of 1956 had a beneficial effect on both clover top‐growth and nodulation. 80–100 1b. of nitrogen per acre had no effect on the number of nodules per gram of root. However, the application of 200 1b. of nitrogen per acre caused a significant decrease in the number of large nodules per gram of root.The numbers of large nodules present reached a midsummer peak where nitrogen was not applied.During the autumn many nodules showed part green and part pink colouration or were completely green or brown, an indication of a decline in nitrogen‐fixing ability. Decaying nodules increased considerably in number when the legume was being suppressed by nitrogen application and top growth was poor. The practical application of these results is discussed and methods of maximising the benefit from clover and fertiliser nitrogen are suggested.
GRASSLAND RESEARCH AND THE FUTURE*
Authors: Duckham A. N. 
Published: April 2006

It seems to me that during the next 20 years:

grass as a feed will increasingly over‐shadow grass as a break in tillage cropping or as a fertility builder
the current rapid progress in biochemistry, plant physiology, radiation biology and the physical sciences may revolutionise our knowledge of applied ecology and genetics
as a result of such research, scientific principles will replace much of the present patchwork of empirical husbandry knowledge
these developments, plus forthcoming changes in labour costs and in grazing, harvesting and conservation techniques will call for a drastic re‐appraisal of much of our current thinking and practice in sward establishment and management; this will involve more applied ecological research
the scientist's laboratory and the engineer's workshop will become more important in grassland research whilst husbandry experiments will increasingly depend on scientific instrumentation.
GRASSES IN WINTER
Authors: Beddows A. R. , Jones Ll.I orwerth 
Published: April 2006

The Aberystwyth district experienced exceptionally cold winter weather in 1954, 1955 and 1956, especially during the period from the end of January to early March. Its effect on the grasses, both in the single‐plant nurseries and in the agronomic experimental areas, is briefly described.It was observed that plants which entered the winter carrying a bulk of herbage in a winter‐proud condition were at a disadvantage compared with those which had been reasonably grazed or cut back during the autumn. The younger plants were found to be better able than the older ones to withstand extreme conditions.Suggestions are made as to how some simple‐mixture swards can be managed so as to be reasonably likely to provide keep in situ during the difficult months December to April. The species under consideration are cocksfoot (Dactylis glomerata), timothy (Phleum pratense and P. nodosum), tall fescue (Festuca arundinacea), perennial ryegrass (Lolium perernne) and Italian ryegrass (L. italicum).
IRRIGATION OF GRASSLAND
Authors: Munro I. A. 
Published: April 2006

An experiment to measure the effects of three soil‐moisture deficits and four nitrogen treatments on the yield, utilisation and botanical composition of a four‐years‐old riverside meadow at the University Farm, Sonning, Berkshire, during the grazing seasons of 1955 and 1956 is described.In both years the yield increased with increasing applications of nitrogen and decreased with increasing soil‐moisture deficit. The utilisation of the herbage, by young stock (15 to 18 months old), was significantly better with irrigation. Irrigation improved the botanical composition of the sward: the clover percentage increased on the irrigated plots but nitrogen produced some depression, the depression increasing with increasing soil moisture deficit; meadow fescue increased and the Poa spp. decreased with progressively greater applications of nitrogen, while on the non‐irrigated plots the sward deteriorated still further, with an ingression of Agrostis and Holcus spp.
AN INVESTIGATION INTO UTILISED GRASSLAND PRODUCTION ON TEN FARMS IN NORTH COUNTY DUBLIN
Authors: Deeny M. C. 
Published: April 2006

Utilised grass production on ten small farms in North County Dublin has been estimated using (A) the method adopted by the British Grassland Society Sub‐Committee on the assessment and recording of the utilised output of grassland, and (B) a live‐weight increase method using Woodman's figures.At the beginning of the grazing season all the grazing animals on each farm were weighed. At the same time the records for method A were begun. Altogether 169 animals and 12 sheep were weighed during March‐April. Animals sold during the period of investigation were weighed, where possible.The results obtained using the two methods have been compared. Average percentage difference on ten observations was 11.3%, with a variation of ± 3.7%. On farms 1–5, where only mature stock were kept, the percentage difference was 9.9%± 2.2%. On farms 6–10, where animals of all categories were grazed, the percentage difference averaged 12.8%± 2.2%. In all cases the live‐weight‐increase method gave the higher estimated yield.The techniques used in the estimation of utilised grassland production are discussed. Total output varied between 26.5 cwt. and 9.0 cwt. of utilised S.E. per acre. The significance of the findings is discussed and the value of the methods used is considered.
THE EFFECT OF DEFOLIATION ON THE SEED‐PRODUCING CAPACITY OF BRED STRAINS OF GRASSES
Authors: Roberts Humphrey M. 
Published: April 2006

A leafy strain of timothy and of perennial ryegrass showed no significant reductions in seed yields following grazing at different dates from October to January, when extra nitrogen was applied.Spring and winter + spring grazing, together with extra nitrogen, significantly reduced the seed yield of S50 timothy for three successive harvest years.Perennial ryegrass S101 showed no reduction after spring or winter + spring grazing when defoliation was made not later than mid‐April, but when grazing was delayed until May and drought occurred there was a significant reduction in seed yield.