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High Fertility (high + fertility)
Selected AbstractsLiveweight gains of lambs from Caucasian clover/ryegrass and white clover/ryegrass swards on soils of high and low fertilityGRASS & FORAGE SCIENCE, Issue 2 2007A. D. Black Summary The high nutritive value and persistence under a wide range of climatic and soil fertility conditions make Caucasian clover a potentially useful forage legume but there is little information about the performance of livestock grazing Caucasian clover/grass swards. This study compared liveweight gains of lambs grazing Caucasian clover/perennial ryegrass and white clover/perennial ryegrass swards on high fertility (Olsen P 20 mg L,1, SO4 -S 12 mg kg,1) and low fertility (Olsen P 11 mg L,1, SO4 -S 7 mg kg,1) soils from 1998 to 2001 in the South Island of New Zealand. Mean annual liveweight gains were 1178 kg ha,1 for Caucasian clover/perennial ryegrass and 1069 kg ha,1 for white clover/perennial ryegrass swards at high fertility compared with 1094 kg ha,1 and 1015 kg ha,1, respectively, at low fertility. There was a higher mean proportion of clover in Caucasian clover/perennial ryegrass (0·19) than white clover/perennial ryegrass (0·11) swards, but there were no differences in total herbage production between the two clover/perennial ryegrass swards. The mean concentration of crude protein in the herbage of Caucasian clover (302 g kg DM,1) was higher than that in white clover (287 g kg DM,1) and grass herbage (227 g kg DM,1). Estimated mean metabolizable energy concentrations in the herbage were 12·5 MJ kg DM,1 for the two clovers and 11·6 MJ kg DM,1 for grass herbage. The difference in liveweight gain between swards on soils of high and low fertility was associated with an increase in total herbage production of similar composition and nutritive value, giving a greater number of grazing days for the swards on soils of high than low fertility. [source] Selective defoliation by sheep according to slope and plant species in the hill country of New ZealandGRASS & FORAGE SCIENCE, Issue 4 2003I. F. López Abstract The objective of the study was to evaluate the grazing behaviour by sheep in hill country paddocks in New Zealand which had received two long-term fertilization and stocking rate treatments [high fertility,high stocking rate (HH); low fertility,low stocking rate (LL)]. Herbage accumulation and selective grazing were evaluated within low slope (LS), medium slope (MS) and high slope (HS) categories. Transects lines were placed and tillers of Agrostis capillaris and Lolium perenne in the LS category; A. capillaris, Anthoxanthum odoratum and L. perenne in the MS category; and A. capillaris and A. odoratum in the HS category were marked. The leaf length of each marked tiller was measured and used to determine selective grazing over 3 weeks during each season. The highest herbage accumulation rates were during spring and the lowest in summer and winter. The LS category showed the highest herbage accumulation rates and HS the lowest. Except for autumn, the marked tillers were more frequently grazed in the HH than in the LL paddock. During summer, autumn and spring, grazing frequency in the slope categories was in the order LS > MS > HS. During winter sheep did not discriminate between slope category. During summer, autumn and spring, sheep did not selectively graze the species studied but this was not the case during winter. Overall, sheep selectively grazed L. perenne. In all the seasons L. perenne consistently had the longest leaves but within species there was no consistent relationship between leaf length and probability of being grazed. Selective grazing changed through the year according to herbage accumulation rate. Sheep concentrated grazing in the category LS when herbage accumulation rate was high, but they did not discriminate between slope categories in winter when herbage accumulation rate was low. [source] Genetic identity of interspecific neighbours mediates plant responses to competition and environmental variation in a species-rich grasslandJOURNAL OF ECOLOGY, Issue 5 2007JASON D. FRIDLEY Summary 1Although outbreeding populations of many grassland plants exhibit substantial genetic and phenotypic variation at fine spatial scales (< 100 m2), the implications of local genetic diversity for community structure are poorly understood. Genetic diversity could contribute to local species diversity by mediating the effects of competition between species and by enhancing species persistence in the face of environmental variation. 2We assayed the performance of three genotypes each of a dominant tussock grass (Koeleria macrantha [Ledeb.] J.A. Schultes) and dominant sedge (Carex caryophyllea Lat.) derived from a single 10 × 10 m quadrat within a limestone grassland in Derbyshire, UK. Genotypes were grown in monoculture and grass,sedge mixtures of different genetic composition in two environments of contrasting fertility. Species mixtures also included one genotype of the subordinate forb Campanula rotundifolia L. 3When grown without neighbours, intraspecific genotypes responded similarly to environmental treatments. One genotype of the sedge performed worse in both environments than the other two sedge genotypes. 4When grown in species mixtures, genotype performance was significantly influenced by the genetic identity of the neighbouring species for both the sedge and the grass. At high fertility, differential genotype performance was not sufficient to alter the expectation of competitive exclusion of the sedge by the grass. However, at low fertility, the competitive dominant depended on the genetic identity of both the grass and the sedge. In addition, each genotype of the grass performed best next to a different genotype of the sedge, and the identity of the best genotype pairings switched with environment. 5Performance of a single genotype of the subordinate Campanula was not predictable by fertility alone, but by how fertility interacted with different neighbouring genotypes of both the grass and the sedge. 6Results support the hypothesis that the genetic identity of interspecific neighbours influences plant performance in multispecies assemblages and mediates species' responses to environmental variation. Such interactions could be a key factor in the contribution of local intraspecific genetic diversity to species diversity. [source] Interactions between non-native plant species and the floristic composition of common habitatsJOURNAL OF ECOLOGY, Issue 6 2006L. C. MASKELL Summary 1We investigated the role of non-native species (neophytes) in common British plant communities using botanical data from two stratified random surveys carried out in 1990 and 1998. 2We found that from 16 851 plots surveyed in 1998 there were 123 non-native species found mostly in arable, tall grass/herb and fertile grassland habitats. Invasive non-native species, e.g. Fallopia japonica, Impatiens glandulifera and Rhododendron ponticum, were uncommon in this survey. 3Between 1990 and 1998 the total number of non-native species increased but the mean number of species per sample plot decreased. The mean cover of non-natives increased from 1.2% to 1.9%. 4There were positive spatial and temporal relationships between non-native and native species diversity. However, there was a weak negative relationship between changes in non-native cover and native diversity. 5The species composition and ecological traits of communities containing non-natives were very different from those that did not contain them. 6In the British countryside non-native species were mainly found in habitats with anthropogenic associations, high fertility, high number of ruderal species and high diversity. There is also an indication that successional shifts where competitive invasive species dominate involve non-native species. 7National-scale changes in plant community composition are likely to be closely correlated with external land-use impacts. Changes such as eutrophication, nitrogen deposition and increased fertility in infertile habitats are likely to benefit both native and non-native invasive species; however, currently these trends benefit native species much more often than non-natives. 8Non-native species are known to have significant effects on native species at local scales in many countries; however, at the landscape scale in Great Britain they are best considered as symptoms of disturbance and land-use change rather than a direct threat to biodiversity. [source] Importance of assemblage-level thinning: A field experiment in an alpine meadow on the Tibet plateauJOURNAL OF VEGETATION SCIENCE, Issue 4 2006Yanjiang Luo Anon. (1998) Abstract Question: Which fraction of the decrease in species richness under fertilization can be explained by assemblage-level thinning? Location: An alpine meadow on the eastern Tibet plateau. Methods: 60-m2 plots were randomly assigned to a control or one of four levels of ammonium phosphate fertilizer. Treatments were repeated for three years. The effect of as semblage-level thinning was decided based on similarity in quadrats within and between fertilizing levels, bootstrap simulation based on random thinning of the high density (low production, low fertility) quadrats and correlation of species' biomass in low fertility and high fertility. Results: Fertilization increased production, reduced species richness and reduced density of individuals. Heavily fertilized quadrats are more similar in species composition in 2000 but less similar in 2001 and 2002. Rarefaction showed that a decrease in density can account for 32.3-42.9% decrease of species richness, but the simulated species richness is always significantly higher than the observed one. When production and species richness are similar at two levels of fertilization, species biomass in the higher fertility treatment is positively correlated with biomass at lower fertility. When the two fertilizer levels differed in production and species richness, there was no evidence of correlation in species biomass, suggesting that assemblage level thinning cannot explain all the loss of species. Conclusion: Although a decrease in density could explain much of the decrease (up to 42.9%) in species richness when this alpine meadow was fertilized, other important mechanisms such as interspecific competition cannot be ignored. Future studies should investigate the effect of assemblage level thinning on species diversity, and search for mechanisms responsible for a decrease in diversity. [source] Validation of plant functional types across two contrasting landscapesJOURNAL OF VEGETATION SCIENCE, Issue 2 2002Michael Kleyer Disturbance; Fertility; Logistic regression; Trait; Urban landscape Abstract. The validation of plant functional type models across contrasting landscapes is seen as a step towards the claim that plant functional types should recur regionally or even globally. I sampled the vegetation of an urban landscape on a range of sites representing gradients of resource supply and disturbance intensity. A group of plants with similar attributes was considered a ,functional type', if the species significantly co-occurred in a certain segment of the gradient plane of resource supply and disturbance intensity. Vegetative and regeneration traits were considered. A similar study was performed in a nearby agricultural landscape (Kleyer 1999). The logistic regression models from the urban landscape were applied to the data set of the agricultural landscape and vice versa. Although the overall environment of the two landscapes was very different, recurrent patterns of several functional types were found. At high fertility and high disturbance levels, annual species predominated with a persistent seed bank, high seed output, and short vertical expansion. When disturbances changed from below-ground to above-ground, the sexual regeneration mode was replaced by the vegetative mode, while vertical expansion remained low. At medium disturbance intensities, the vertical expansion and vegetative regeneration increased with fertility, while the seed bank remained mostly transient to short-term persistent and lateral expansion and sexual regeneration was intermediate. At low disturbances and low resource supplies, seed bank longevity, and vertical and lateral expansion tended to be long. Diversity of groups of plants with similar attributes was highest at intermediate disturbance levels and low fertility. These results correspond with Grime's humped-back model and Connell's intermediate disturbance hypothesis. [source] Proteins of the accessory sex glands associated with the oocyte-penetrating capacity of cauda epididymal sperm from holstein bulls of documented fertilityMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2007Arlindo A. Moura Abstract We previously reported that accessory sex gland fluid (AGF) from high fertility (HF) bulls influenced the oocyte-penetrating capacity of cauda epididymal sperm from low fertility (LF) bulls, based on in vitro fertilization (IVF) assays. The present study determined if AGF proteins were associated with these effects. Nineteen IVF assays with 12 bulls were grouped as follows. Group I (n,=,8): assays where sperm from LF bulls exposed to AGF from HF bulls had greater oocyte penetration than exposed to homologous AGF. Group II (n,=,7): sperm from LF bulls to AGF from HF bulls versus homologous AGF showed no significant differences. Group III (n,=,4): sperm from LF bulls treated with homologous AGF had greater fertility than sperm treated with AGF from HF bulls. Sire fertility was based on nonreturn rates (NNR) and AGF collected by artificial vagina from bulls with cannulated vasa deferentia. Two-dimensional SDS,PAGE maps of AGF were analyzed by PDQuest and proteins identified by tandem mass spectrometry and Western blots. Differences in spot intensity between AGF of HF and LF bulls were compared across groups of IVF assays (P,<,0.05). The expression of BSP A1/A2 and A3, BSP 30 kDa, clusterin, albumin, phospholipase A2 (PLA2), and osteopontin was greater in the AGF of HF bulls in Group I as compared to Groups II and III. Conversely, there was less nucleobindin in the AGF of HF bulls in Group I than in Groups II and III. This is the first report of nucleobindin (58 kDa/pI 5.6) in male reproductive fluids, using both immunoblots and mass spectrometry. Thus, the effect of AGF from HF bulls on epididymal sperm is likely the result of specific proteins expressed in the AGF. Mol. Reprod. Dev. © 2006 Wiley-Liss, Inc. [source] Reproduction and lifespan: Trade-offs, overall energy budgets, intergenerational costs, and costs neglected by research,AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2009Grazyna Jasienska In human females allocation of resources to support reproduction may cause their insufficient supply to other metabolic functions, resulting in compromised physiology, increased risks of diseases and, consequently, reduced lifespan. While many studies on both historical and contemporary populations show that women with high fertility indeed have shorter lifespans. This relationship is far from universal: a lack of correlation between fertility and lifespan, or even an increased lifespan of women with high fertility have also been documented. Reduced lifespan in women with high fertility may be undetectable due to methodological weaknesses of research or it may be truly absent, and its absence may be explained from biological principles. I will discuss the following reasons for a lack of the negative relationship, described in some demographic studies, between the number of children and lifespan in women: (1) Number of children is only a proxy of the total costs of reproduction and the cost of breastfeeding is often higher than the pregnancy cost but is often not taken into account. (2) Costs of reproduction can be interpreted in a meaningful way only when they are analyzed in relation to the overall energy budget of the woman. (3) Trade-offs between risks of different diseases due to reproduction yield different mortality predictions depending on the socio-economic status of the studied populations. (4) Costs of reproduction are related not only to having children but also to having grandchildren. Such intergenerational costs should be included in analysis of trade-offs between costs of reproduction and longevity. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] Molecular cytogenetic analysis of a durum wheat ×Thinopyrum distichum hybrid used as a new source of resistance to Fusarium head blight in the greenhousePLANT BREEDING, Issue 5 2001Q. Chen Abstract Fusarium head blight (FHB, scab), caused by Fusarium graminearum Schwabe, is a serious and damaging disease of wheat. Although some hexaploid wheat lines express a good level of resistance to FHB, the resistance available in hexaploid wheat has not yet been transferred to durum wheat. A germplasm collection of Triticum durum× alien hybrid lines was tested as a potential source of resistance to FHB under controlled conditions. Their FHB reaction was evaluated in three tests against conidial suspensions of three strains of F. graminearum at the flowering stage. Two T. durum×Thinopyrum distichum hybrid lines, ,AFR4' and ,AFR5,, expressed a significantly higher level of resistance to the spread of FHB than other durum-alien hybrid lines and a resistant common wheat line ,Nyu-Bay'. Genomic in situ hybridization using total genomic DNA from alien grass species demonstrated that ,AFR5' had 13 or 14 alien genome chromosomes plus 27 or 28 wheat chromosomes, while ,AFR4' had 22 alien genome and 28 wheat chromosomes. All of the alien chromosomes present in these two lines belonged to the J genome. ,AFR5' is likely to be more useful as a source of FHB resistance than ,AFR4' because of its relatively normal meiotic behaviour, high fertility and fewer number of alien chromosomes. ,AFR5' shows good potential as a source for transferring FHB resistance gene into wheat. The development of T. durum addition lines carrying resistance genes from ,AFR5' is underway. [source] Projections of the Ethnic Minority Populations of the United Kingdom 2006,2056POPULATION AND DEVELOPMENT REVIEW, Issue 3 2010David Coleman The ethnic minority populations in the UK are growing substantially through immigration, a youthful age structure, and in some cases relatively high fertility. Their diverse demographic and socioeconomic characteristics have attracted considerable academic and policy attention, especially insofar as those distinctive characteristics have persisted in the generations born in the UK. No official projections of the UK ethnic populations have been published since 1979. This article provides projections to 2056 and beyond of 12 ethnic groups. Given overall net immigration and vital rates as assumed in the office for National Statistics 2008-based Principal Projection, and the ethnic characteristics estimated here, the ethnic minority populations (including the Other White) would increase from 13 percent of the UK population in 2006 to 28 percent by 2031 and 44 percent by 2056, and to about half the 0,4 age group in 2056. Alternative projections assume various lower levels of immigration. Possible implications of projected changes are discussed. [source] ,Low' fertility and population replacement in ScotlandPOPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 1 2007John MacInnes Abstract It has been argued that Scotland faces population ageing and decline that will have potentially serious economic and social consequences, and that the origin of these processes lie in its low and declining fertility rates. After considering alternatives to the total period rate measure of fertility, empirical evidence and theoretical argument about low fertility and its consequences is briefly reviewed. The paper argues that low fertility in general may not be the problem it is often purported to be, that Scotland has relatively high fertility, and that pro-natalist policies are neither desirable nor necessary. It suggests that low fertility and population ageing may be viewed as positive developments, and that within Europe, Scotland is distinguished more by its excess of early deaths than by any shortage of births. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||