bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling temporal variability in the carbon balance of a spruce/moss boreal forest
Authors: FROLKING S. , GOULDEN M.L. , WOFSY S.C. , FAN S‐M. , SUTTON D.J. , MUNGER J.W. , BAZZAZ A. M. , DAUBE B.C. , CRILL P. M. , ABER J. D. , BAND L.E. , WANG X. , SAVAGE K. , MOORE T. , HARRISS R.C. 
Published: April 2006

AbstractA model of the daily carbon balance of a black spruce/feathermoss boreal forest ecosystem was developed and results compared to preliminary data from the 1994 BOREAS field campaign in northem Manitoba, Canada. The model, driven by daily weather conditions, simulated daily soil climate status (temperature and moisture profiles), spruce photosynthesis and respiration, moss photosynthesis and respiration, and litter decomposition. Model agreement with preliminary field data was good for net ecosystem exchange (NEE), capturing both the asymmetrical seasonality and short‐term variability. During the growing season simulated daily NEE ranged from ‐4 g C m‐2d‐1(carbon uptake by ecosystem) to + 2 g C m‐2d‐1(carbon flux to atmosphere), with fluctuations from day to day. In the early winter simulated NEE values were + 0.5 g C m‐2d‐1, dropping to + 0.2 g C m‐2d‐1in mid‐winter. Simulated soil respiration during the growing season (+ 1 to + 5 g C m‐2d‐1) was dominated by metabolic respiration of the live moss, with litter decomposition usually contributing less than 30% and live spruce root respiration less than 10% of the total. Both spruce and moss net primary productivity (NPP) rates were higher in early summer than late summer. Simulated annual NEE for 1994 was ‐51 g C m‐2y‐1, with 83% going into tree growth and 17% into the soil carbon accumulation. Moss NPP (58 g C m‐2y‐1) was considered to be litter (i.e. soil carbon input; no net increase in live moss biomass). Ecosystem respiration during the snow‐covered season (84 g C m‐2) was 58% of the growing season net carbon uptake. A simulation of the same site for 1968–1989 showed = 10–20% year‐to‐year variability in heterotrophic respiration (mean of + 113 g C m‐2y‐1). Moss NPP ranged from 19 to 114 g C m‐2y‐1; spruce NPP from 81 to 150 g C m‐2y‐1; spruce growth (NPP minus litterfall) from 34 to 103 g C m‐2y‐1; NEE ranged from +37 to ‐142 g C m‐2y‐1. Values for these carbon balance terms in 1994 were slightly smaller than the 1969–89 means. Higher ecosystem productivity years (more negative NEE) generally had early springs and relatively wet summers; lower productivity years had late springs and relatively dry summers.
Early needle senescence and thinning of the crown structure of Picea abies as induced by chronic SO2pollution. I. Model deduction and analysis
Authors: SLOVIK STEFAN 
Published: April 2006

AbstractRegarding time ranges of years, a rationale has been developed which is capable of explaining observed ‘spruce decline’ symptoms observed when spruce is exposed to air containing ambient levels of SO2. It integrates and interrelates (i) ecophysiological data (tree morphology, assimilate partitioning, canopy turnover, senescence physiology, stomatal conductance, canopy throughfall, sulphur metabolism, tonoplast symport), (ii) pedological data (soil leaching, cation recycling, litter decomposition, forest nutrition), and (iii) meteorological data (site elevation, length of the annual trunk growth period, SO2‐pollution). Furthermore, it can explain field observations at numerous sites of spruce decline in central Europe where SO2 is implicated as a factor of forest decline: (i) thinning of the canopy structure; (ii) early needle senescence; (iii) cation deficiency; (iv) low SO2 tolerance at sites with depleted soils in the mountains; (v) synergism of SO2pollution and acidic precipitation; (vi) recovery after liming, fertilization and after decreasing SO2 pollution; and (vii) higher SO2 tolerances of deciduous angiosperms. Different SO2tolerance strategies are identified that are employed by more SO2‐tolerant tree species. Ecophysiological SO2tolerance factors interact in a complex synergistic or antagonistic manner. It is concluded that chronic SO2 pollution at ambient concentrations predisposes mainly evergreen gymnosperms to suffer under synergistic environmental stresses (frost, drought, pathogens, etc.). Thinning of the crown structure is massive at extreme sites, where several stresses act simultaneously on the trees (depleted soils, high SO2 pollution, acidic rain, etc.). Mathematical formulations allow precise definitions of terms such as cooperativity, synergism, antagonism, vitality, predisposition, latency, etc. This universal rationale, which is applicable to all tree species, is exemplified here for Norway spruce (Picea abies [L.] Karst.). Integration of parameters yields an ordinary differential equation, which can be solved analytically. It predicts reversible dynamics of crown structures and gives an ecophysiological background to‘damage’.
THE COMPOSITION OF A SHEEP'S NATURAL DIET
Authors: Tribe D. E. 
Published: April 2006

SummaryTbe protein, carbohydrate, fat, vitamin and mineral contents of plants are known to differ at different stages of growth and between species; for this reason it is plainly important for the husbandman to know what plants and parts of plants bis animals prefer. Tbis paper reviews available information concerning the composition of a sheep's natural diet and discusses the experimental difficulties involved in its collection.
STUDIES ON THE PRODUCTIVITY OF FIRST YEAR LEY GRASS WHEN CUT AT DIFFERENT STAGES OF GROWTH, ENSILED AND FED TO BEEF CATTLE
Authors: Dodsworth T. L. , McK. Campbell W. H. 
Published: April 2006

A number of feeding trials, designed to determine the fattening value of grass silage for beef cattle, have been carried out during the last four years in Aberdeenshire. A general account of these trials has been published, (3, 4) and a detailed account of some of the results of Trial No. 9 is in the press (5). The chemical analysis required in Trial 9 was performed by Dr. A. J. G. Bamett, Department of Biological Chemistry, Univeristy of Aberdeen. Some aspects of these analytical results have already been published (1, 2).During two of these trials, carried out on the Duthie Craibstone Farm, data was eollected during the silage making periods as well as for the actual feeding trials. It was therefore possible to relate the liveweight increase obtained in the feeding trials to the acreage of grass cut. This has been done and the results obtained are now presented.Both trials were designed to determine the fattening value of silage made from grass cut at three different stages of maturity. In both cases the acreage of grass available had to be cut a number of times in order to obtain the tonnage of silage required for the feeding trials. The results obtained therefore represent the full seasonal yields per acre of grass, grass eilage and liveweight increase which can be obtained when first year ley grass is cut at difFerent stages of growth, and when different cutting frequencies are practised. In both trials a control group of cattle was fed on swedes and oat straw. A comparison can then be made of the stock carrying and fattening capacities of swedes and silage.
THE RENOVATION OF DOWNLAND PERMANENT PASTURE
Authors: Norman M. J. T. , Green J. O. 
Published: April 2006

An experiment involving surface cultivations and seeding of poor downland permanent pasture, followed by controlled sheep grazing at two levels of nitrogen manuring, was conducted at Hurley, between 1951 and 1955.Two series of sowings were made. In 1952, establishment of spring‐sown perennial ryegrass was more successful than that of summer‐sown ryegrass, while in 1955 the reverse was true. Differences in establishment were attributed to the degree of competition from the original herbage and to soil moisture conditions. In spite of a relatively low establishment, development of perennial ryegrass on plots which received 5 cwt. Nitro‐Chalk per acre annually following the 1952 spring and summer sowings was satisfactory. Development of white clover was satisfactory only after spring sowing without nitrogen. Cocksfoot, timothy and meadow fescue failed to establish. On the area treated in 1952, first‐class pasture species (perennial ryegrass, cocksfoot and white clover) contributed, by 1955, nearly 60 per cent to sown plots receiving nitrogen, and approximately 40 per cent to sown plots without nitrogen. Without cultivations and sowing, the proportion of first‐class species was approximately 30 per cent at both levels of nitrogen. The mean increase in dry matter yield due to cultivations and sowing two and three years after treatment was 11 per cent, while the mean increase due to nitrogen was 30 per cent. Both nitrogen manuring and sowing increased the nitrogen content of the herbage and the proportion of total annual yield recorded in spring and autumn.
STUDIES ON THE ROOT DEVELOPMENT OF HERBAGE PLANTS
Authors: Baker H. K. 
Published: April 2006

The effects of cutting on the root, stubble and herbage growth of perennial ryegrass during establishment was studied under sward conditions.Although a few weeks after a cutting treatment there was a smaller root weight on the cut than on the uncut swards, this difference eventually disappeared.By the autumn the frequently cut swards had considerably more plants and tillers per unit area than the uncut plots. As a result of these changes in plant density the root weight per unit area of the sward was not decreased by increasing the cutting frequency during establishment. However, the root weight per plant (and per tiller) was decreased by increases in the cutting frequency.The root and stubble weights increased during the spring, summer and early autumn of the first year and decreased during the winter. In the second season the root weight increased to a maximum in December whilst the stubble weight rose during the spring and summer and decreased after September.Although the percentage of total soluble carbohydrate was consistently higher in the stubble than the roots or herbage the quantity was similar in both roots and stubble, and in these organs the major soluble carbohydrate was fructosan.During the winter both the percentage and the total quantify of soluble carbohydrate in the stubble and roots decreased considerably.Herbage growth in February and March was not correlated with the root weight per unit area in the previous autumn but was positively correlated with the root weight per plant. The highest herbage yield in the early spring came from plots which were leniently treated in the previous autumn: these plots had a low plant and tiller density but the root weight per plant or per tiller was relatively high.In April the rate of herbage growth tended to be positively correlated with the sward density. In May and June the highest herbage yields came from the open swards. It was suggested that during this latter period moisture, and/or nitrogen, may have been the limiting factor, so that the open sward benefited from less interplant competition.
THE EFFECT OF DUNG AND URINE AND ITS INTERACTIONS WITH APPLIED NITROGEN, PHOSPHORUS AND POTASSIUM ON THE CHEMICAL COMPOSITION OF PASTURE
Authors: Watkin B. R. 
Published: April 2006

The importance of the grass/clover balance of a pasture in determining the effects of manurial returns and fertiliser applications on the chemical composition of the sward is shown.The response to applied nitrogen was very dependent on the presence or absence of the animal excrements. For example, the N recovery from an application of 18 cwt. per acre of nitro‐chalk was only 2% in the absence but 68% in the presence of the grazing animal.Urine caused a marked increase in the N and K content and the yield of pasture, particularly when returned in quantity to a high‐producing grass‐dominant sward, and at the same time tended to depress the Ca, P and Mg content. Urine K was superior to fertiliser K, per pound of K returned or applied, in raising the K content of the pasture.By comparison, dung had little direct effect on chemical content; even when returned in large amounts it affected the Ca and K content of the pasture to a relatively small extent. The P returned in the dung had little effect on the P content of the pasture and was inferior to superphosphate in this respect.Together, as in normal grazing, dung and urine tended to counter or enhance their individual effects.There was a positive correlation between the Mg and P content of the pasture and a negative correlation between Mg and K. Brief mention is made of the possible importance of the nutrient balance in pasture as a factor in animal health.
THE STABILITY OF S23 PERENNIAL RYEGRASS DURING SEED MULTIPLICATION
Authors: Cooper J. P. 
Published: April 2006

In outbreeding species, such as perennial ryegrass, most plants are heterozygous for genes controlling agronomic characters and varieties must usually be based on more than one plant to avoid inbreeding depression. This leads to the possibility of change under the selective action of seed multiplication.Several stocks of S23 perennial ryegrass were examined to see whether such a change occurred; Irish, Kent and Hunsballe were grown for comparison.The characters recorded were date of ear emergence, winter requirement before heading, and leaf size, rate of leaf appearance, tillering and dry‐weight production in the young seedling.A slight shift towards earliness of heading occurred during seed multiplication, but no regular change in the other characters could be detected. The S23 stocks could readily be distinguished from Hunsballe and, less easily, from Irish, as early as the sixth leaf stage.It is concluded that although considerable genetic variation for all these characters exists within the S23 stocks, changes during seed multiplication are not inevitable but depend on the management of the crop.
LEAFINESS, CHEMICAL COMPOSITION AND YIELD OF SOME LUCERNE VARIETIES
Authors: Zaleski A. , Dent J. W. 
Published: April 2006

The leaf: stem ratio on green and dry weights, chemical composition and yield of dry‐matter and protein per acre were determined for ten varieties of lucerne at the National Institute of Agricultural Botany during 1955–8. The first cut was taken when about 20% of the flowers were open and the subsequent cuts when 10–15% were open.The mean leaf: stem ratio, based on green weights, showed no significant difference between varieties. The early varieties, however, contained a higher proportion of dry‐matter in the leaf and a lower proportion in the stem than did the mid‐season and late types. As a result, the early types tended to show a higher leaf: stem ratio based on dry‐matter than the mid‐season and late types.The early types also contained a significantly higher percentage of protein than the mid‐season and late types, and had a lower crude fibre content for the whole plant.Highly significant differences were established between varieties and types in the total yields of dry‐matter and protein from three cuts in each of three seasons, when all were cut at similar stages of maturity. The heaviest yields of dry‐matter and protein were secured from Eynsford, Chartrain‐villiers and Du Puits, the lowest from certified Provence and Grimm, both of which came from an environment vastly different from that of Cambridge. Gamma, an early variety, had the highest percentage of crude protein at each cut during the three year period, but it was similar to FD 100 and Marais in total dry matter yield.
DETERMINATION OF THE DRY WEIGHT OF HERBAGE BY DRYING METHODS
Authors: Greenhill W. L. 
Published: April 2006

An investigation has been made with the object of establishing a satisfactory drying method for use in determining the dry weight of air‐dry herbage. In one experiment, drying was carried out at various temperatures over P2O5 and also at a sustained high vacuum: in a second experiment, oven drying was carried out at atmospheric pressure at various temperatures and for various periods.Decomposition has been found to occur at comparatively low temperatures while, on the other hand, the intensity with which some of the moisture is held suggests that it may not all be removed at “safe” temperatures, even at very low vapour pressures.The best technique that can be suggested at the present time is drying over P2O5 at 40°C. For less accurate results oven‐drying at atmospheric pressure at 80°C for 16 hours is proposed.
THE GRASSLANDS OF YORKSHIRE'S WEST RIDING
Authors: Jones John 
Published: April 2006

In the West Riding of Yorkshire there is great variation in farm practice as well as in the character and productivity of the grasslands.Such natural Features as the weather and the form and type of the land coupled with man's influence help to explain why most of the grass and rough grazings occupy the western areas whereas arable crops are concentrated in the east.The distribution of grass as a percentage of total crops and of grass (excluding rough grazings) of cattle and of sheep are each illustrated in a diagram.In describing the Riding's grassland pattern the county is divided into two main regions—the Pennines and the lowlands.Sub‐divisions of these areas have been used to simplify this account of grassland husbandry.
CLOVER NITROGEN AND SWARD PRODUCTIVITY
Authors: Herriott J. B. D. , Wells D. 
Published: April 2006

Under mowing conditions in the absence of the animal, ultra‐simple swards based either on ryegrass or cocksfoot gave large increases in yield of dry matter and nitrogen from the inclusion of white clover in the seeds mixture. Raising the clover seed rate from 1 to 3 lb./acre gave a further response in yield.As the swards aged, the continuing effect of increased clover seed rate was dependent on applied nitrogen.The rate of transference of nitrogen from clover to the soil depended upon the species of the associated grass, the clover seed rate, the age of the sward and the degree of reduction of the clover in the sward.Suppression of clover led to an increase in soil nitrogen, particularly with high seed rates of clover.Dry matter response to applied nitrogen (69 lb./acre/annum) was greater in cocksfoot than in ryegrass. Fertilizer nitrogen had little effect on the yield of nitrogen from the sward except where the high seed rate of clover had been used.
AGRONOMIC CHARACTERISTICS OF RYEGRASS PLANTS OBTAINED FROM AN ELEVEN YEAR OLD SWARD
Authors: Gardner A. L. 
Published: April 2006

The investigation compared the agronomic characteristics of Irish and S 23 perennial ryegrass plants grazed for 11 years with newly propagated Irish and S 23.The sample drawn from the surviving Irish population displayed the following characters relative to the newly propagated plants: the date of ear emergence was 2 days later, the growth habit at emergence was similar, the aftermath was more leafy.The S 23 subjected to the same management as the Irish was identical with newly propagated S 23, apart from earlier ear emergence. The possible reason for this and the consequent limitations of the results are discussed.
THE PRODUCTION OF EARLY SPRING GRASS
Authors: Baker H. K. 
Published: April 2006

Spring nitrogen significantly increased the yields of early spring grass. The response per lb. of nitrogen applied in the early spring ranged from 9 to 28 lb. of dry matter, depending upon the weather. Autumn nitrogen significantly increased herbage yields during the autumn. The increase per lb. of nitrogen ranged from 12 to 22 lb. of dry matter.Autumn nitrogen caused significant increases in the yield of early spring grass in 1956, but these increases were very small and not of practical importance.The effects of autumn grazing on spring yields were not consistent and were small when compared with the effects of spring nitrogen. Both autumn grazing and autumn nitrogen tended to reduce the percentage of soluble carbohydrates in the stubble and roots of grasses in November.
STUDIES OF THE GROWTH OF A HYP ARRHENIA‐DOMINANT GRASSLAND IN NORTHERN RHODESIA
Authors: Brockington N. R. 
Published: April 2006

The results of studies preliminary to management trials on this type of grassland are reported. The annual growth cycle of the community is described in terms of herbage yields and chemical composition. It is shown that repeated cutting at an early growth stage will prevent the rapid deterioration in quality of the herbage which is evident in the uninterrupted growth cycle. Changes in the sward with repeated cutting are described.The second phase of growth, after the main flush has flowered and set seed, may be enhanced by cutting in the second half of the wet season; it is suggested that this aftermath growth might be used for grazing in the first part of the dry season.The annual growth cycles cf six component species of the community grown as pure stands are described, together with the yields and chemical composition of the herbage obtained from them with repeated cutting.The results of fertilizer trials on this type of grassland are given, and it is shown that substantial increases in yield of dry matter and percentage crude protein may be obtained with the application of sulphate of ammonia. Responses to dressings of superphosphate are largely conditional on alleviating the nitrogen deficiency, and there is a significant nitrogen/phosphorus interaction. Both marinate of potash and agricultural lime have little effect on growth and production at the levels tested.Investigation of the practice of burning the grassland in the late dry season, after resting from grazing in the previous wet season, confirms that this is an effective means of checking the encroachment of woody species, but the flush of new grass growth induced by the fire is of such small bulk as to be of no importance in grazing management.
THE EFFECT OF NITROGENOUS FERTILIZER ON AN ESTABLISHED WHITE CLOVER SWARD
Authors: Cowling D. W. 
Published: April 2006

The effect of nitrogenous fertilizer on a white clover sward was studied to obtain information to be used in the evaluation of white clover in grassland. There was no evidence of a yield response. The weight of nodules was depressed by the addition of fertilizer.Where management is adjusted to maintain white clover in swards receiving large quantities of nitrogenous fertilizer the clover may use part of this fertilizer at the expense of symbiotic fixation.The relation of the results obtained to the assessment of the benefit derived from white clover in mixed swards is briefly discussed.
STUDIES IN THE DIGESTIBILITY OF HERBAGE
Authors: Minson D. J. , Kemp C. D. 
Published: April 2006

Data from 291 digestion trials have been used to derive regression equations relating the organic‐matter digestibility of herbage to the nitrogen percentage of its dry matter and to the nitrogen percentage in the organic matter of the resulting faces.The residual errors are very high and it is shown that the deviations from the lines are not randomly distributed but have a seasonal trend. The seasonal biases have been calculated, and the inclusion of month of cutting as a factor is found to improve the two regressions to some extent. Monthly regressions have also been calculated. Even with these, however, the errors are still too high for many practical purposes.