bluuebunny/crossref_metadata_2025_split huggingface dataset:
The temporal response of forest ecosystems to doubled atmospheric CO2 concentration
Authors: MCMURTRIE ROSS E. , COMINS HUGH N. 
Published: April 2006

AbstractVegetation 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

AbstractAn 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

AbstractWater 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

AbstractVertical 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.
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.
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.
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.
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.
THE EFFECT OF GROWTH‐REGULATING WEEDKILLERS ON THE MORPHOLOGY OF GRASSES
Authors: Jeater R. S. L. 
Published: April 2006

A series of experiments were carried out in 1954 and 1955 designed to investigate the effects of MCPA and 2,4‐D applied at different stages of growth to grasses grown for seed. Single, spaced plants were sprayed at the rate of 1·5 lb. a.e. per acre with 2,4‐D amine in 1954 and with 2,4‐D amine and ester and MCPA ester in 1955. The development of the grass growing point was used as a criterion of the developmental stages at which the plants were sprayed.Some treatments caused abnormal types of growth. S.23 perennial ryegrass and S.143 cocksfoot developed ear malformations, S.53 meadow fescue had leaf and ear malformations, while S.51 timothy showed leaf, stem and ear abnormalities.Leaf malformations developed only after spraying when the growing points showed vegetative primordia while ear abnormalities usually appeared after treatment at most early stages of development. Stem malformation in timothy occurred after spraying at all stages in 1954, but only at the vegetative stages in 1955.The percentage of abnormal ears in a random sample of tillers in all but one case fell as the growing point developed and most damage occurred after treatment when the apex was at the vegetative stage. Normally, treatment when glume ridges were visible on the apex produced no significant difference between the number of abnormal ears in the treated and untreated plots.The results suggest that the chemicals act on that part of the apex which is just beginning its development but is not yet visible as a protuberance on the apex.The type of abnormalities occurring in grasses as a result of spraying with growth regulating weedkillers is similar to those found in cereals after similar treatment.Provided that the chemicals are applied in the 4 to 5 weeks prior to ear emergence the amount of malformation occurring in the grasses will be small.
A COMPARISON OF BROADCAST AND WIDE‐ROW SPACED GRASSES WHEN MANAGED FOR FOGGAGE PRODUCTION
Authors: Gardner A. L. 
Published: April 2006

A small‐plot trial comparing perennial ryegrass, cocksfoot, timothy and meadow fescue sown broadcast and also in 21 inch rows was conducted at Auchincruive from 1954 to 1957. The cutting treatments were arranged so that measurement could be made of both summer and winter production.Of the four species, cocksfoot was the most suitable for foggage production. Perennial ryegrass suffered severely from winter killing. Timothy and meadow fescue, although persistent, did not yield as much as cocksfoot.Total dry‐matter production over three years was higher from the cocksfoot rows than from the broadcast stand. For ryegrass and meadow fescue, broadcasting gave higher yields than row sowing while timothy showed no significant difference between sowing methods.During the winter, all species showed a loss of dry matter. Losses for ryegrass, cocksfoot, timothy and meadow fescue were respectively 34%, 17%, 18% and 24%. Broadcast stands averaged 11% greater loss than the rows.
GRASS‐ALFALFA SEEDING RATIOS AND CONTROL OF ALFALFA DOMINATION IN MIXTURES*
Authors: Kilcher† M. R. 
Published: April 2006

Three grasses, bromegrass, slender wheatgrass and reed canary grass were sown on irrigated land with Ladak alfalfa in varying ratios with the object of determining what effect different proportions of alfalfa to grass would have in preventing alfalfa domination. The total number of seeds, irrespective of the proportions used, was held constant at 2.5 per linear inch of row.The influence of alfalfa on total yield was such that no significant yield differences due to grasses were established. However, the relative stand of grass varied considerably in the different mixtures. Slender wheatgrass did not compete with Ladak alfalfa, and had nearly disappeared from all stands after five crop‐years. Smooth bromegrass swards were dominated by the alfalfa, partrcularly where small amounts of the griass were sown. Reed canary grass and alfalfa maintained strong stands at all ratios of seed mixtures.The best overall ratio of grass to alfalfa by seed numbers was about 2.5: 1, although a higher ratio of grass was found desirable where brome was the grass component.Ratio of grass seed to alfalfa seed offered some measure of control for alfalfa domination, but choice of grass species was more important.
THE EFFECT OF DEFOLIATION ON THE SEED‐PRODUCING CAPACITY OF BRED STRAINS OF GRASSES
Authors: Roberts H. M. 
Published: April 2006

Two leafy strains of cocksfoot, S143 and S37 were subjected to winter, spring and winter + spring defoliation; 2 cwt. per acre of nitro‐chalk was applied after each defoliation, in addition to the standard manuring for all plots.Winter grazing of leafy cocksfoot does not appear to depress the yield of seed appreciably when extra nitrogen is applied.Grazing of cocksfoot in mid‐April is likely to depress the seed yield substantially, especially if followed by a very dry summer.The reaction to hard defoliation by sheep may vary with the growth form of the cocksfoot strain.Grazing appeared to be more detrimental to seed yield than defoliation by cutting.During this investigation, prolonged frost which occurred during the early part of the year appeared to have an adverse effect on cocksfoot seed yield.
PARTIAL WILTING OF GRASS CROPS FOR SILAGE
Authors: Nash M. J. 
Published: April 2006

The aim of this, the final stage of the investigation, was to test the partial wilting process on a farm scale and to draw practical conclusions which might help farmers wishing to try it. Three important conclusions are drawn: (1) filling should be performed rapidly, (2) consolidation should be applied continuously, (3) sealing should be done immediately. Some overheating, a reduction in digestibility and considerable spoiling are likely to occur if herbage, wilted for much more than one day, is ensiled spasmodically with insufficient consolidation.The wilting process is not foolproof and cannot be practised properly without giving great attention to detail, both in the field and at the silo. The method becomes a very much safer one when wilted and bruised, rather than wilted, long herbage is employed.
THE GRAZING ANIMAL AND SWARD PRODUCTIVITY
Authors: Herriott J. B. D. , Wells D.A. , Dilnot Jean 
Published: April 2006

A trial designed to show the effects of animal excreta on sward productivity is described.It was estimated that the grazing sheep returns in a season nutrients capable of immediate uptake by the plant equivalent to 5–6 cwt. nitro‐chalk and 2–21/2 cwt. 60% muriate of potash per acre.A large part of sward yield depended on animal return. Clover depression from the effects of animal excreta and, under mowing treatment, from the effects of fertilizer nitrogen, did not result in marked loss of transferred clover nitrogen. There appeared to be a gain in clover soil‐nitrogen from a reduction of the clover stand.A comparison is made between the restilts obtained from sheep excreta on the sward with those obtained from mowing treatment.The interaction between animal or fertilizer nitrogen and the clover plant is discussed.
GRAZING TRIALS WITH PERENNIAL RYEGRASSES IN IRELAND
Authors: Prendergast J. J. 
Published: April 2006

Four varieties of perennial ryegrass are compared throughout the seeding year and the first four harvest years (1954–58). Two of the varieties, Irish ‘commercial’ and New Zealand, are of ‘early’ type; and the others, Glasnevin and S23 are, ‘late’.New Zealand gave the most grazing, 1% more than ‘commercial’ and Glasnevin, and 5% more than S23.The ‘early’ varieties contrasted markedly with the ‘lates’ in seasonal growth.In persistency and in resistance to invasion by unsown species, the ‘lates’ were better than the ‘earlies’ S23 was outstanding, and New Zealand had an advantage over ‘commercial’. The ‘earlies’ were the more compatible with clover.New Zealand appears to have most merit, but sowing of more than one variety may give better results.
THE EFFECTS OF SEED RATE, CLOVER AND APPLIED NITROGEN ON BROADCAST SEED CROPS OF PASTURE RYEGRASS
Authors: Lewis J. 
Published: April 2006

This investigation was carried out with leafy varieties of perennial ryegrass at four centres near Aberystwyth over a period of three years. Nitrogen applied in spring increased lodging, the number of fertile tillers and also seed yield, except where sowing was made without a cereal cover crop. While reasonable yields were obtained from badly laid crops, it is suggested that lodging prior to anthesis has an adverse effect on seed yield. Clover included as a companion species tended to depress the yield of seed and increase the degree of lodging.Seed rate had less infiuence on lodging and seed yield, but the data show that similar yields were obtained from light seed rates of 4 lb. per acre as from the heavier rates. On the other hand, there was a tendency for the low rate of seeding to produce weedy plots, especially when sown in the absence of a cover crop.
INVESTIGATIONS ON LOCAL STRAINS (VARIETIES) OF HERBAGE PLANTS
Authors: Hawkins R. P. 
Published: April 2006

Data are presented to show the effect on type of multiplying seed of wild white clover obtained from permanent pastures and of seed from old pastures in different localities. The variation in type in samples of commercial wild white clover is shown.The cause of the change in type of certain stocks of Kersey white clover is demonstrated. The steps taken to maintain the original type are described.The value of certain botanical characters in indicating the agronomic behaviour of varieties of white clover is discussed.