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Faunal interchange and Miocene terrestrial vertebrates of southern Asia
- John C. Barry, Michele E. Morgan, Alisa J. Winkler, Lawrence J. Flynn, Everett H. Lindsay, Louis L. Jacobs, David Pilbeam
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- Journal:
- Paleobiology / Volume 17 / Issue 3 / Summer 1991
- Published online by Cambridge University Press:
- 14 July 2015, pp. 231-245
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Problems of stratigraphic completeness and poor temporal resolution make analysis of faunal change in terrestrial sequences difficult. The fluvial Neogene Siwalik formations of India and Pakistan are an exception. They contain a long vertebrate record and have good chronostratigraphic control, making it possible to assess the influence of biotic interchange on Siwalik fossil communities. In Pakistan, the interval between 18 and 7 Ma has been most intensively studied and changes in diversity and relative abundance of ruminant artiodactyls and muroid rodents are documented with temporal resolution of 200,000 years. Within this interval, diversity varies considerably, including an abrupt rise in species number between 15 and 13 Ma, followed by a decline in ruminant diversity after 12 Ma and a decline in muroid diversity in two steps at 13 and 10 Ma. Significant changes in relative abundance of taxa include an increase in bovids between 16.5 and 15 Ma, a decrease in tragulids after 9 Ma, and a very abrupt increase in murids at 12 Ma. Megacricetodontine rodents also decrease significantly at 12 Ma, and smaller declines are recorded among myocricetodontine and copemyine rodents after 16 Ma. An increase of dendromurine rodents at 15.5 Ma is also observed. There is also a trend of progressive size increase among giraffoids and bovids throughout the sequence.
We have also investigated relationships between biotic interchange and diversity, body size, and relative abundance, concluding that (1) the rapid increase in ruminant and muroid diversity was largely due to immigration, whereas in situ speciation had only a secondary role; (2) during intervals of increasing diversity, resident lineages did not have higher than average rates of in situ speciation; (3) during intervals with rising diversity, greater extinction did not accompany increased immigration; (4) during intervals with falling diversity, there may have been greater extinction in recently invading lineages; and (5) change in diversity was independent of changes in relative abundance and body size.
Faunal and Environmental Change in the Late Miocene Siwaliks of Northern Pakistan
- John C. Barry, Michèle E. Morgan, Lawrence J. Flynn, David Pilbeam, Anna K. Behrensmeyer, S. Mahmood Raza, Imran A. Khan, Catherine Badgley, Jason Hicks, Jay Kelley
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- Journal:
- Paleobiology / Volume 28 / Issue S2 / Spring 2002
- Published online by Cambridge University Press:
- 14 July 2015, pp. 1-71
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The Siwalik formations of northern Pakistan consist of deposits of ancient rivers that existed throughout the early Miocene through the late Pliocene. The formations are highly fossiliferous with a diverse array of terrestrial and freshwater vertebrates, which in combination with exceptional lateral exposure and good chronostratigraphic control allows a more detailed and temporally resolved study of the sediments and faunas than is typical in terrestrial deposits. Consequently the Siwaliks provide an opportunity to document temporal differences in species richness, turnover, and ecological structure in a terrestrial setting, and to investigate how such differences are related to changes in the fluvial system, vegetation, and climate. Here we focus on the interval between 10.7 and 5.7 Ma, a time of significant local tectonic and global climatic change. It is also the interval with the best temporal calibration of Siwalik faunas and most comprehensive data on species occurrences. A methodological focus of this paper is on controlling sampling biases that confound biological and ecological signals. Such biases include uneven sampling through time, differential preservation of larger animals and more durable skeletal elements, errors in age-dating imposed by uncertainties in correlation and paleomagnetic timescale calibrations, and uneven taxonomic treatment across groups. We attempt to control for them primarily by using a relative-abundance model to estimate limits for the first and last appearances from the occurrence data. This model also incorporates uncertainties in age estimates. Because of sampling limitations inherent in the terrestrial fossil record, our 100-Kyr temporal resolution may approach the finest possible level of resolution for studies of vertebrate faunal changes over periods of millions of years.
Approximately 40,000 specimens from surface and screenwash collections made at 555 localities form the basis of our study. Sixty percent of the localities have maximum and minimum age estimates differing by 100 Kyr or less, 82% by 200 Kyr or less. The fossils represent 115 mammalian species or lineages of ten orders: Insectivora, Scandentia, Primates, Tubulidentata, Proboscidea, Pholidota, Lagomorpha, Perissodactyla, Artiodactyla, and Rodentia. Important taxa omitted from this study include Carnivora, Elephantoidea, and Rhinocerotidae. Because different collecting methods were used for large and small species, they are treated separately in analyses. Small species include insectivores, tree shrews, rodents, lagomorphs, and small primates. They generally weigh less than 5 kg.
The sediments of the study interval were deposited by coexisting fluvial systems, with the larger emergent Nagri system being displaced between 10.1 and 9.0 Ma by an interfan Dhok Pathan system. In comparison to Nagri floodplains, Dhok Pathan floodplains were less well drained, with smaller rivers having more seasonally variable flow and more frequent avulsions. Paleosol sequences indicate reorganization of topography and drainage accompanying a transition to a more seasonal climate. A few paleosols may have formed under waterlogged, grassy woodlands, but most formed under drier conditions and more closed vegetation.
The oxygen isotopic record also indicates significant change in the patterns of precipitation beginning at 9.2 Ma, in what may have been a shift to a drier and more seasonal climate. The carbon isotope record demonstrates that after 8.1 Ma significant amounts of C4 grasses began to appear and that by 6.8 Ma floodplain habitats included extensive C4 grasslands. Plant communities with predominantly C3 plants were greatly diminished after 7.0 Ma, and those with predominantly C4 plants, which would have been open woodlands or grassy woodlands, appeared as early as 7.4 Ma.
Inferred first and last appearances show a constant, low level of faunal turnover throughout the interval 10.7–5.7-Ma, with three short periods of elevated turnover at 10.3, 7.8, and 7.3–7.0 Ma. The three pulses account for nearly 44% of all turnover. Throughout the late Miocene, species richness declined steadily, and diversity and richness indices together with data on body size imply that community ecological structure changed abruptly just after 10 Ma, and then again at 7.8 Ma. Between 10 and 7.8 Ma the large-mammal assemblages were strongly dominated by equids, with more balanced faunas before and after. The pattern of appearance and disappearance is selective with respect to inferred habits of the animals. Species appearing after 9.0 Ma are grazers or typical of more open habitats, whereas many species that disappear can be linked to more closed vegetation. We presume exceptions to this pattern were animals of the mixed C3/C4 communities or the wetter parts of the floodplain that did not persist into the latest Miocene. The pace of extinction accelerates once there is C4 vegetation on the floodplain.
The 10.3 Ma event primarily comprises disappearance of taxa that were both common and of long duration. The event does not correlate to any obvious local environmental or climatic event, and the pattern of species disappearance and appearance suggests that biotic interactions may have been more important than environmental change.
The 7.8 Ma event is characterized solely by appearances, and that at 7.3 Ma by a combination of appearances and disappearances. These two latest Miocene events include more taxa that were shorter ranging and less common, a difference of mode that developed between approximately 9.0 and 8.5 Ma when many short-ranging and rare species began to make appearances. Both events also show a close temporal correlation to changes in floodplain deposition and vegetation. The 7.8 Ma event follows the widespread appearance of C4 vegetation and is coincident with the shift from equid-dominated to more evenly balanced large-mammal assemblages. The 7.3 to 7.0 Ma event starts with the first occurrence of C4-dominated floras and ends with the last occurrence of C3-dominated vegetation. Absence of a consistent relationship between depositional facies and the composition of faunal assemblages leads us to reject fluvial system dynamics as a major cause of faunal change. The close correlation of latest Miocene species turnover and ecological change to expansion of C4 plants on the floodplain, in association with oxygen isotopic and sedimentological evidence for increasingly drier and more seasonal climates, causes us to favor explanations based on climatic change for both latest Miocene pulses.
The Siwalik record supports neither “coordinated stasis” nor “turnover pulse” evolutionary models. The brief, irregularly spaced pulses of high turnover are characteristic of both the stasis and pulse models, but the high level of background turnover that eliminates 65–70% of the initial species shows there is no stasis in the Siwalik record. In addition, the steadily declining species richness and abrupt, uncoordinated changes in diversity do not fit either model.
Variation in harvest index of maize (Zea mays) and common bean (Phaseolus vulgaris) grown in a marginal rainfall area of Kenya
- C. J. Pilbeam
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- Journal:
- The Journal of Agricultural Science / Volume 126 / Issue 1 / February 1996
- Published online by Cambridge University Press:
- 27 March 2009, pp. 1-6
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Maize (Zea mays L.) and common bean (Phaseolus vulgaris L.) were grown in five seasons, beginning in the long rains 1990 and ending in the short rains 1992, at Kiboko, Kenya under a range of different management conditions (N fertilization, irrigation, population density and intercropping). Seed weight was plotted against total dry weight to determine harvest index for both crops. For bean the intercept of this relationship for each experiment, with one exception, was not significantly different from zero, so that the slopes of the regressions were the harvest indices. Harvest indices for bean varied more between seasons (0·38–00·85) than from the effects of management practices (00·53–0·71). Over all seasons and treatments, the index for bean did not vary systematically with crop weight, and averaged 0·50. By contrast, a similar analysis for maize over all seasons and treatments, showed that the harvest index varied with crop dry weight, approaching an asymptotic value as dry weight increased. The regression intercepts for the different experiments were significantly different from each other, and in three cases differed significantly from zero. Therefore, although the slopes for the different experiments were parallel, they did not always represent the harvest index.
Factors influencing disease resistance in high and low tannin Vicia faba
- F. Kantar, P. D. Hebblethwaite, C. J. Pilbeam
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- Journal:
- The Journal of Agricultural Science / Volume 127 / Issue 1 / August 1996
- Published online by Cambridge University Press:
- 27 March 2009, pp. 83-88
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The in vitro resistance of five white and four coloured-flowered lines and cultivars of Vicia faba to seed and root inoculation with spore suspensions of the pathogenic soil-borne fungi, Fusarium culmorum and Pythium debaryanum, was investigated under aseptic conditions in the UK. The presence of foliar diseases was also assessed in the field in 1989/90. White-flowered lines were more susceptible than coloured genotypes to fungal infection during germination but equally resistant during seedling growth. High-tannin containing seed coats had chemical and physical properties which protected seeds against fungal infection during germination. Frequent cracking of the seed coat in a zero-tannin line was associated with a greater fungal contamination of seeds. Resistance to the foliar diseases Uromyces viciae-fabae and Botrytis fabae was not related to flower colour. The results are discussed in relation to emergence in white-flowered types.
Effects of plant population density on determinate and indeterminate forms of winter field beans (Vicia faba) 1. Yield and yield components
- C. J. Pilbeam, P. D. Hebblethwaite, H. E. Ricketts, T. E. Nyongesa
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- Journal:
- The Journal of Agricultural Science / Volume 116 / Issue 3 / June 1991
- Published online by Cambridge University Press:
- 27 March 2009, pp. 375-383
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Using an indeterminate cultivar, Bourdon, and a determinate selection, 858 (provided by Plant Breeding International, Cambridge), of winter field bean, the effect of plant population density on yield was investigated in field trials at the University of Nottingham at Sutton Bonington in three consecutive seasons beginning in 1985/86.
Plant morphology had no effect on the optimum plant density, which for both entries lay between 10 and 20 plants/m2. Bourdon yielded significantly more (2 t/ha, on average) than 858 and this was attributable to more pods/pod-bearing stem, more seeds/pod and heavier seeds. Selection 858 was also less winter hardy.
Yield was most closely correlated with number of seeds/plant, but other components were almost as important, highlighting the plasticity of yield in Vicia faba and the difficulties in attempting to increase yield by selecting for particular components of yield.
In contrast to spring beans, the indeterminate cultivar of winter field bean produced as many branches as the determinate entry and both produced fewer branches at higher densities. There was no difference between the two growth habits in the relative contribution of each stem class to the yield of the whole plant. Higher-order branches contributed less than the main stem to final yield.
Effects of plant population density on spring-sown field beans (Vicia faba) with different growth habits
- C. J. Pilbeam, G. Duc, P. D. Hebblethwaite
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- Journal:
- The Journal of Agricultural Science / Volume 114 / Issue 1 / January 1990
- Published online by Cambridge University Press:
- 27 March 2009, pp. 19-33
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Determinate varieties of Vicia faba are smaller and may require higher plant population densities than their conventional indeterminate counterparts to attain high yields. This hypothesis was examined at the University of Nottingham farm at Sutton Bonington, UK, and at INRA, Dijon, France in 1986 and 1987. The determinate varieties Ticol and TP667 and indeterminate M5.1 and Maris Bead were sown in the spring to give a range of densities of 10–100 plants/m2.
Yields generally increased as population density increased. The optimum density for determinate varieties was higher than for indeterminate varieties. Indeterminate varieties yielded more than determinate varieties at all plant densities, perhaps because of their larger canopy. Seed yields were affected by year and location. Greater yields were associated with heavier seeds and more seeds per pod.
Although several yield components, when expressed per unit area, were significantly correlated with seed yield, their coefficients of determination were never very large. This confirmed the plasticity of yield in field beans.
Effects of plant population density on determinate and indeterminate forms of winter field beans (Vicia faba) 2. Growth and development
- C. J. Pilbeam, P. D. Hebblethwaite, T. E. Nyongesa, H. E. Ricketts
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- Journal:
- The Journal of Agricultural Science / Volume 116 / Issue 3 / June 1991
- Published online by Cambridge University Press:
- 27 March 2009, pp. 385-393
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In studies at the University of Nottingham at Sutton Bonington in two consecutive seasons beginning in 1986/87, Bourdon, an indeterminate cultivar, and 858, a determinate selection (provided by Plant Breeding International, Cambridge), were compared under six target plant population densities ranging from 10 to 80 plants/m2.
As the season progressed, total dry matter production increased to a maximum and then declined. However, growth rates slowed at pod set because, it is suggested, of the change in the chemical composition of the newly synthesized biomass, from carbohydrate to protein, at that time. Leaf area duration was greater in Bourdon than in 858, especially during pod set, but it bore no relation to seed yield. Specific leaf area was unaffected by competition for light. It is proposed that changes in plant population density affect the competition for assimilates within a plant rather than the competition for light between different plants. Losses of branches and reproductive nodes, with time, are cited as evidence for this. The apparent causes of the lower yield of determinate forms of winter field bean relative to indeterminate forms are discussed.
Analysis of maize–common bean intercrops in semi-arid Kenya
- C. J. Pilbeam, J. R. Okalebo, L. P. Simmonds, K. W. Gathua
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- Journal:
- The Journal of Agricultural Science / Volume 123 / Issue 2 / October 1994
- Published online by Cambridge University Press:
- 27 March 2009, pp. 191-198
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Maize (Zea mays L.) and common bean (Phaseolus vulgaris L.) were each sown at four plant densities, including zero, in a bivariate factorial design at Kiboko Rangeland Research Station, Kenya during the long and short rains of 1990. The design gave nine intercrops with different proportions of maize and beans, and six sole crops, three of maize and three of beans. Seed yields in both the sole crops were not significantly affected by plant density, so the mean yield was used to calculate the Land Equivalent Ratio (LER), which averaged 1·09 in the long rains but only 0·87 in the short rains. These low values were apparently due to the fact that beans failed to nodulate and fix nitrogen in the study area. The difference in LER between seasons was probably caused by differences in the amount and distribution of rain in relation to crop growth. Maize was more competitive than bean, each maize plant being equivalent to between 0·7 and 3·4 bean plants depending upon the treatment and the season.
Effects of autumn sowing dates on growth and yield of indeterminate and determinate field beans (Vicia faba)
- C. J. Pilbeam, P. D. Hebblethwaite, H. E. Ricketts, O. A. Hassan
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- Journal:
- The Journal of Agricultural Science / Volume 114 / Issue 3 / June 1990
- Published online by Cambridge University Press:
- 27 March 2009, pp. 339-352
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Determinate forms of field bean (Vicia faba L.), because of their altered growth habit, may differ in phenology from indeterminate cultivars and so their responses to environmental conditions may necessitate different optimum sowing dates. This was studied in autumn-sown field beans at the University of Nottingham at Sutton Bonington by standard growth analysis techniques, final yield components and monitoring of crop growth stages in an indeterminate cultivar, Bourdon, and two determinate populations, 858 and 796 (provided by Plant Breeding International, Cambridge), in three consecutive seasons beginning in 1985/86.
Bourdon yielded significantly more (2·4 t/ha, on average) than the determinate selections as a result of more pod-bearing nodes per stem and seeds per pod and a greater individual seed weight. There was, however, no correlation between seed yield and canopy size, either in total or during pod filling. Determinacy, contrary to expectation, did not increase harvest index. In fact, the reproductive stems of Bourdon had higher harvest indices than those of 858. The yield disadvantage of determinates was therefore exacerbated by the existence of reproductive stems, which, by prolonging the maturation phase, may also detract from a further potential benefit of the determinate habit, namely an increase in yield stability.
There seemed to be no cultivar differences in the temperature requirement for the initiation of developmental processes. An average accumulation of 1239 °C days was required from sowing to flowering. Differences between this and other work in the calculated base temperature for flowering were cautiously explained by the lack of data distinguishing day and night temperature in this experiment and by the use of autumn-sown rather than spring-sown cultivars. It is also suggested that photoperiod may be important in initiating flowering.
Both determinate and indeterminate forms gave the greatest seed yields from the earliest sowing dates.
Analysis of Water Budgets in Semi-Arid Lands from Soil Water Records
- C. J. Pilbeam, C. C. Daamen, L. P. Simmonds
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- Journal:
- Experimental Agriculture / Volume 31 / Issue 2 / April 1995
- Published online by Cambridge University Press:
- 03 October 2008, pp. 131-150
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Four components of the water budget for a growing season, namely storage, drainage, transpiration and direct evaporation from the soil surface, were estimated using a suite of techniques. The only data requirements were rainfall, neutron probe measurements of soil water content and microlysimeter measurements of evaporation from the soil. Data from four growing seasons at Kiboko, Kenya between 1990 and 1992 were used to provide examples of the estimations. Drainage was significant (about 10% of rainfall) in one season only; in the other seasons, total evaporation comprised at least 95% of the seasonal rainfall.
Drainage was determined using a relationship between unsaturated hydraulic conductivity and soil water content that was determined during the early part of the rainy season when water was penetrating to depth. This analysis made it possible to identify a critical water content at the base of the soil profile, above which there would be significant drainage. However, there are large errors associated with estimation of drainage if significant drainage occurs.
Estimates of direct evaporation from the soil surface were used as the basis of distinguishing transpiration from total evaporation. Microlysimetry was used to develop a model of evaporation from these sandy soils, which was based on the assumption that the evaporation from the soil surface following heavy rainfall is a unique function of time from rainfall, and little influenced by the presence of a sparse crop. This method showed that direct evaporation from the soil accounted for between 70 and 85% of total evaporation in seasons when total evaporation estimates ranged from 150 to 325 mm.
RESPONSE OF WHEAT–RICE AND MAIZE/MILLET SYSTEMS TO FERTILIZER AND MANURE APPLICATIONS IN THE MID-HILLS OF NEPAL
- D. P. Sherchan, C. J. Pilbeam, P. J. Gregory
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- Journal:
- Experimental Agriculture / Volume 35 / Issue 1 / February 1999
- Published online by Cambridge University Press:
- 01 February 1999, pp. 1-13
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Farmers in the mid-hills of Nepal have a mix of rainfed land on which millet is grown in relay after maize (maize/millet), and irrigated land on which wheat is grown sequentially after rice (wheat–rice). Double cropping is the norm but the diminishing quantities of organic materials, coupled with the trend towards increased use of inorganic fertilizers, have raised questions about the long-term productivity and sustainability of the cropping systems. The aim of this work was to examine the long-term effects (eight years) on grain yield of additions of manure and fertilizer either singly or in combination. Maize/millet and wheat–rice rotations were established on a Dystochrept at Pakhribas Agricultural Centre at about 1450 m altitude. Manure and fertilizer applications were applied to the maize (eight combinations in May) and the wheat (different rates in seven combinations in November) every year with the succeeding crops (millet and rice) utilizing residual nutrients. Yields of maize, millet and rice were greater when manure rather than fertilizer was applied but yields of wheat were less. The combined application of manure and fertilizer significantly increased yields of maize and wheat compared with applications of either manure or fertilizer alone. However, for the subsequent crops (millet and rice) there was either a small residual benefit of the combined application when compared with fertilizer alone, or no benefit when compared with manure alone. Overall, the combined application increased total grain yields by about 35% in the maize/millet rotation and by 16% in the wheat–rice rotation. There was no trend in yields in response to treatment with time.
Effect of rotation on the recovery of 15N-labelled fertilizer applied to wheat grown in Northern Syria
- C. J. PILBEAM, A. M. McNEILL, H. C. HARRIS, R. S. SWIFT
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- Journal:
- The Journal of Agricultural Science / Volume 129 / Issue 4 / December 1997
- Published online by Cambridge University Press:
- 01 December 1997, pp. 397-407
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Wheat was grown in rotation with three different crops, namely wheat, chickpea and lentil, and with a fallow, in three consecutive seasons beginning in 1992 in NW Syria. Two rates of N fertilizer (0 and 30 kg N ha−1) were superimposed on these four rotations, giving eight treatments which were replicated three times in each season. 15N-labelled fertilizer was applied to microplots within the fertilized plots at sowing when unlabelled fertilizer was broadcast on the rest of the plot.
Yields of grain and dry matter were generally greatest when wheat followed a fallow, and least in the continuous wheat rotation; this was significant in 1993 and 1994. Applications of N fertilizer had no effect on productivity in 1992, but in the other two seasons grain yields were increased by 550 kg ha−1, on average. Depending on the season, between 8 and 26% of the 15N-labelled fertilizer was recovered in the shoot dry matter, while between 18 and 54% of the fertilizer remained as N in the soil at harvest, mostly in the 0–20 cm soil layer. More than half the fertilizer in the crop at harvest had been taken up by the end of March, although by March the plants were only c. 10% of their mass at harvest. Conversely, <35% of the soil-derived N in the crop at harvest had generally been taken up by March. This temporal difference in the pools of N utilized by the crop was attributed to the drying of the soil surface layers where most of the N fertilizer remained. Approximately 50% of the 15N-labelled fertilizer was unaccounted for in the crop and 0–40 cm soil layer at harvest.
The yield benefit of growing wheat in rotation with a fallow or either grain legume rather than continuously, ranged from nothing to the equivalent of a fertilizer application of at least 30 kg N ha−1 to continuous wheat, depending upon the season and the previous crop. Only in the season where the residual effect of the rotation on wheat yields was greatest (1993) did the preceding grain legume crop or fallow appear to contribute between 10 and 20 kg N ha−1 to the wheat crop. Otherwise they contributed no N at harvest. While a fallow may increase the availability of water to the succeeding wheat crop, the benefit from the preceding grain legumes may lie in their effect on the soil physical structure or on the increased availability of other limiting nutrients rather than additional N.
Effect of fertilizer rate and form on the recovery of 15N-labelled fertilizer applied to wheat in Syria
- C. J. PILBEAM, A.M. McNEILL, H. C. HARRIS, R. S. SWIFT
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- Journal:
- The Journal of Agricultural Science / Volume 128 / Issue 4 / June 1997
- Published online by Cambridge University Press:
- 01 June 1997, pp. 415-424
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15N-labelled fertilizer was applied at different rates (0, 30, 60, 90 kg N ha−1) and in different forms (urea or ammonium sulphate) to wheat grown in Syria in three seasons (1991/92, 1992/93 and 1994/95).
Recovery of 15N-labelled fertilizer in the above-ground crop at harvest was low (8–22%), with the amount of 15N-labelled fertilizer recovered in the crop increasing as the rate of application increased. Fertilizer application caused a significant increase in the amount of unlabelled soil N in the crop, suggesting that the application of N fertilizer caused a ‘real’ added nitrogen interaction. Recovery of 15N-labelled fertilizer in the crop was unaffected by the form of the fertilizer.
On average 31% (14–54%) of the 15N-labelled fertilizer remained in the soil at harvest, mostly in the 0–20 cm layer. At the lowest application rate (30 kg N ha−1) most of the residual fertilizer was as organic N, but at the higher application rates (60 and 90 kg N ha−1), a greater proportion of the 15N-labelled fertilizer was recovered as inorganic N, presumably as the result of top-dressing N in dry conditions in the spring. The amount of 15N-labelled fertilizer remaining in the soil increased as the fertilizer rate increased, but was unaffected by the form of fertilizer applied.
Losses of 15N-labelled fertilizer were large (>35%), probably caused by gaseous losses, either through volatilization of N from the calcareous soil, or through denitrification from wet soils rich in organic residues.
N fertilization strategies in the West Asia/North Africa (WANA) region should take note of the low recovery of N fertilizer by the crop in the season of application, and the resultant large quantities of residual fertilizer.
PROPORTION OF TOTAL NITROGEN AND FIXED NITROGEN IN SHOOTS OF LENTIL AND CHICKPEA GROWN IN A MEDITERRANEAN-TYPE ENVIRONMENT
- C. J. PILBEAM, M. WOOD, M. J. JONES
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- Journal:
- Experimental Agriculture / Volume 33 / Issue 2 / April 1997
- Published online by Cambridge University Press:
- 01 April 1997, pp. 139-148
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Shoot dry matter yield, shoot nitrogen yield and amount of nitrogen derived from fixation are collated for chickpea (Cicer arietinum L.) cv. ILC482 and lentil (Lens culinaris Medic.) cv. ILL8 grown at the ICARDA research station Tel Hadya, Syria over a period of 17 years. Regression analyses of shoot nitrogen yield on shoot dry matter and of the amount of nitrogen fixed on shoot nitrogen yield were undertaken for both species. The intercepts for both analyses with lentil were not significantly different from zero, so the slopes of the lines represented the concentration of nitrogen in the plant tissue (20.6 g kg−1 dry matter) and the proportion of nitrogen derived from fixation 0.75. Data for other cultivars of lentil grown at Tel Hadya and at four other locations in Syria fell within the 95% confidence limits of the original analyses. The intercept of the regression of shoot nitrogen yield on shoot dry matter yield for chickpea grown at Tel Hadya was not significantly different from zero, so the concentration of nitrogen in the plant tissue was constant (17.8 g kg−1 dry matter). The proportion of nitrogen derived from fixation increased asymptotically as the shoot nitrogen yield increased. Data for other cultivars of chickpea grown in different locations were generally similar to those for cv. ILC482 grown at Tel Hadya. It is proposed that generalized relationships between shoot nitrogen yield and shoot dry matter yield, and between amount of nitrogen fixed and shoot nitrogen yield can be established for lentil and chickpea grown in the West Asia–North Africa region. Consequently the amounts of nitrogen fixed by the two crops could be predicted from a knowledge of dry matter production alone.
Neogene Siwalik mammalian lineages: species longevities, rates of change, and modes of speciation
- Lawrence J. Flynn, John C. Barry, Michele E. Morgan, David Pilbeam, Louis L. Jacobs, Everett H. Lindsay
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- Journal:
- The Paleontological Society Special Publications / Volume 6 / 1992
- Published online by Cambridge University Press:
- 26 July 2017, p. 101
- Print publication:
- 1992
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The Siwalik sequence, particularly the interval from 18 to 7 Ma, provides one of the few terrestrial data sets that allows direct measurement of temporal durations of mammalian species. Its data are drawn from a single biogeographic subprovince and superposed collections likely represent successive samples of single lineages. Observed temporal ranges underestimate total species longevities if (1) species existed in other biogeographic provinces before or after the temporal ranges recorded in the Siwaliks, or (2) the fossil record inadequately samples species durations in the Siwalik subprovince. Some data, notably from Afghanistan, China, and Thailand, bear on the first variable. The second can be controlled by considering data quality, in this case the temporal distribution of good data sets, to assess the scale of accuracy available for defining range endpoints. In general, range endpoints can be estimated to the nearest 0.1 million years.
The diverse Rodentia give a mean species longevity of 2.2 million years for the Miocene Siwaliks. This includes single records, but of course ignores unretrieved rare or short-lived taxa. The diverse Artiodactyla yield 3.1 million years. The difference may reflect greater body size and longer generation time; large Perissodactyla and Proboscidea have longer temporal ranges. Carnivorous mammals also show about 3 million year durations. Given these data, the average longevity for Sivapithecus species (1.6 million years) is modest. The deposits of the Clarks Fork Basin, Wyoming, offer a Paleogene data set comparable to that of the Neogene Siwaliks. Paleocene-Eocene mammals of North America yield shorter longevities (most less than one million years).
Extinction is the dominant mode of species termination for Siwalik mammals. Most taxa originated by immigration (as at about 13.5 Ma) or abrupt speciation. There are some cases for insitu transformation of lineages, for example in the genera Punjabemys, Antemus, Percrocuta, Dorcatherium, Giraffokeryx, and Selenoportax. The rodent Kanisamys shows a rate of increase in tooth size of 0.5 darwins. This overall rate is moderate by Paleogene standards, but includes an interval of more rapid change between 9.0 and 8.5 Ma.