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41.
The winter season has been identified as a significant contributor to N2O emissions from boreal soils, but our understanding of the processes regulating these emissions is fragmentary. We investigated potential N-sources and pathways involved in N2O formation in a frozen boreal forest soil by labeling soil samples with 15N-containing substrates, and measured rates of 15N2O/15N2 formation under both oxic and anoxic conditions. Our results showed that all N2O produced in the frozen samples originate from denitrification, but the rate-limiting factor is NO3− availability, which is largely governed by nitrification. This suggests that N2O formation in frozen boreal soils may be sustained for a prolonged period of time, but is governed by a delicate balance of the O2 regime. 相似文献
42.
David J. Gilbert Jeremy R. McKenzie Nicholas M. Davies 《Journal of Agricultural, Biological & Environmental Statistics》2001,6(2):281-291
We found evidence that tagging induced trap shyness in snapper (Pagrus auratus), i.e., tagged fish had a reduced probability of recapture by the method by which they had originally been caught. Tagging experiments in 1985 and 1994 involving single release over a short period and single recapture were conducted on a closed population (SNA 1: East Northland-Hauraki Gulf-Bay of Plenty). Initial capture was by trawling and by line fishing, while recapture over an extended period included other methods. A test for trap shyness that removed the possible effects of spatial and fish size heterogeneity gave a significant result for both years. The data suggested that the trap shyness effect might have been smaller for trawl-released fish than for line-released fish. However, we estimated a single trap shyness factor (0.71). There was also some evidence for attenuation of trap shyness over time. 相似文献
43.
Godfree Chigeza Steve Boahen Melaku Gedil Eric Agoyi Hapson Mushoriwa Nicholas Denwar Therese Gondwe Abush Tesfaye Alpha Kamara Oladeji Emmanuel Alamu David Chikoye 《Plant Breeding》2019,138(4):455-464
Formal public sector soybean breeding in Africa spans over four decades, and it was initiated by the International Institute of Tropical Agricultural (IITA). As the demand of soybean continues to outstrip production, strategic projects such the Tropical Legume (TL) were initiated, in which the main goal was to enhance the productivity of soybean in the farmers’ fields in Sub‐Saharan Africa. One of the strategies to enhance the productivity of soybean in the farmers’ fields is through developing and deploying improved soybean varieties in the target countries. Through the TL I and TL II projects, a number of varieties were released in the target countries, Kenya, Nigeria, Malawi and Mozambique by employing participatory variety selection (PVS). This review provides highlights of the achievements made by IITA breeding programme and insights of what needs to be done to enhance yield improvement for soybean in Africa using demand‐driven breeding approaches. 相似文献
44.
Krystina D. Mossop Nicholas P. Moran David G. Chapple Bob B. M. Wong 《Landscape Ecology》2017,32(5):1065-1078
Context
Dispersal has important fitness consequences for individuals, populations, and species. Despite growing theoretical insights into the evolution of dispersal, its behavioral underpinnings remain empirically understudied, limiting our understanding of the extent and impact of responses to landscape-level heterogeneity of environments, and increasing the risk of inferring species-level responses from biased population sampling.Objectives
We asked if predictable ecological variation among naturally fragmented arid waterbodies is correlated with disparate dispersal responses of populations of the desert goby Chlamydogobius eremius, which naturally inhabits two habitat “types” (permanent springs, ephemeral rivers), and different levels of hydrological connectivity (high and low) that potentially convey different costs and benefits of dispersal.Methods
To test for possible behavioral divergence between such populations, we experimentally compared the movement behaviors (correlates of emigration and exploration) of wild-caught fish. We used two biologically relevant spatial scales to test movement relevant to different stages of the dispersal process.Results
Behavior differed at both spatial scales, suggesting that alternative dispersal strategies enable desert gobies to exploit diverse habitat patches. However, while emigration was best predicted by the connectivity (flood risk) of fish habitats, exploration was linked to their habitat type (spring versus river).Conclusions
Our findings demonstrate that despite a complex picture of ecological variation, key landscape factors have an overarching effect on among-population variation in dispersal traits. Implications include the maintenance of within-species variation, potentially divergent evolutionary trajectories of naturally or anthropogenically isolated populations, and the direction of future experimental studies on the ecology and evolution of dispersal behavior.45.
Randomized complete block (RCB) design is the most widely used experimental design in biological sciences. As number of treatments increases, the block size become larger and it looses the capacity to control the variance within block, which is its original purpose. A method known as post hoc blocking could be used in these cases to improve the genetic parameter estimation and thus obtain an unbiased assessment of the performance of a given treatment. In trufgrass breeding, as other breeding program, this is a common challenge. The goal of this study was to test the capacity of different post hoc blocking designs to improve the genetic parameter estimation of zoysiagrass (Zoysia spp.). We evaluated two post hoc blocking designs; row–column (R–C) and incomplete block (IB) designs on five genotype trials located in Florida. The results showed that post hoc R–C design had superior model fitting than both the original RCB and the post hoc IB designs when studied at the single measurement level and at the site level. The narrow-sense heritability (0.24–0.40) and the genotype-by-measurement correlation (0.57–0.99) did not change significantly when R–C was compared to the original RCB design. The ranking of the top performing genotypes changed considerably when comparing RCB to R–C design, but the degree depended on the location analyzed. We conclude that the change in the ranking of the top (potentially select individuals) is coming from the better control of intra-block environmental variation, and this could potentially have a significant impact on the breeding selection process. 相似文献
46.
47.
Li Y Xin J Gao Y Zhang J Nicholas RA Lin Y 《Veterinary journal (London, England : 1997)》2009,179(1):137-141
In this study, six Chinese strains of Mycoplasma mycoides subsp. mycoides small colony type (MmmSC) isolated between 1953-1960 were analysed and their molecular characteristics compared to those of the African PG1 and Afade strains, the European C305 and 138/5 strains and the closely related caprine M. mycoides subsp.mycoides large colony type Y-goat strain. PCR amplification of long DNA fragments showed that the six Chinese strains, the PG1 strain and the Y-goat strain, just like Afade, did not have the 8.84 kb deletion characteristic of the European strains C305 and 138/5. In comparison, the lppB gene sequence of the six MmmSC Chinese strains was found to be 99% homologous to that of PG1and Afade, but <93% homologous to the Y-goat sequence. The anti-rLppB antiserum reacted with PG1, Y-goat and the six Chinese strains at 67 kDa sites in Western blot, indicating that the lppB gene and its encoding protein exist in the Chinese strains. Multilocus sequence analysis (MLSA) of MmmSC strains from various regions confirmed that the Chinese strains were identical to the African and Australian cluster. This finding was further supported by the outcome of selective primer amplification. Based on these results, it is suggested that CBPP in China may have originated from Australia. 相似文献
48.
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50.
In vitro antimycoplasmal activity of six Jordanian medicinal plants against three Mycoplasma species
Al-Momani W Abu-Basha E Janakat S Nicholas RA Ayling RD 《Tropical animal health and production》2007,39(7):515-519
The in vitro effect of six Jordanian traditional medicine plant methanolic extracts were tested against 32 isolates of Mycoplasma species; Mycoplasma mycoides subsp. mycoides LC (6), Mycoplasma capricolum subsp. capricolum (8) and M. putrefaciens (18), all isolated from either nasal swabs or milk, from sheep and goats in different regions in Jordan. All Mycoplasma species showed susceptibility to Artemisia herba-alba and Artemisia arborescens with MIC ranges from 3.125–12.5 mg/ml. Allium sativum and Punica grantum showed limited activity against some Mycoplasma isolates. Olea europea and Citrullus colocynthis showed no in vitro activity against any of the Mycoplasma species tested. Artemisia herba-alba and Artemisia arborescens may therefore be useful for the treatment of mycoplasma infections.
The authors are British Civil Servants and as such their work is subject to British Crown Copyright. This means the exclusive
copyright for the article cannot be transferred. 相似文献