Irrigation of seed carrots on a sandy loam soil     

J. E. Ayars  R. B. Hutmacher  J. J. Steiner  A. B. Mantel  S. S. Vail 《Irrigation Science》1991,12(4):193-198

Summary Little research has been reported which quantifies the response of a carrot (Daucus carrota L. var sativa DC.) seed crop to water management. While the area of seed production of this crop in the United States is less than 3000ha, the return ranges from US $2000 to $ 10 000 ha^–1. Because of the need to mature and dry the seed on the plant, carrot seed is generally grown in areas with negligible summer rain and thus depends on irrigation to supply the crop water requirement. A study was conducted to determine the effect of irrigation water management on seed production and crop water use of carrots grown by the root-to-seed method. Two carrot types (Nantes and Imperator) were evaluated in 9 irrigation treatments over a three year study period. Irrigation treatments which replaced a percentage of the calculated crop evapotranspiration on either a daily basis or when a soil water depletion reached 30 mm were used. A trickle irrigation system with the laterals placed on the carrot bed was used to apply a uniform and accurate amount of water. There was a marked difference in the crop response to the water management of the two carrot types used. The Nantes type exhibited a positive response to moderate water deficits in terms of improved pure live seed (PLS) yield while the Imperator achieved its maximum yield when it was not stressed. Higher irrigation applications in the Nantes type resulted in reduced yields while the Imperator was not affected after its non-stress water requirement was met. Soil water data indicated that the most active zone of extraction of water was to a depth of 1.5 m in the soil profile. As the depth of applied water approached the crop water requirement, the depth of extraction was reduced. Increasing the frequency of irrigation also tended to reduce the depth of extraction of soil water. A total crop water use of approximately 550 to 620 mm was needed to achieve the best PLS yield which is roughly equal to potential evapotranspiration in the San Joaquin Valley, during the time that the crop water use was calculated. In such a climate, the irrigation interval should not exceed 3 to 5 days depending on the time of year.  相似文献   

A tool for community-based assessment of the implications of development on water security in hillside watersheds   总被引：1，自引：0，他引：1  

J. C. Luijten  E. B. Knapp  J. W. Jones 《Agricultural Systems》2001,70(2-3):603-622

Development and population growth in Latin American countries with steep slope farming are likely to further increase pressures on water and land resources. A methodology was developed for assessing water availability and use under different development pathways at a watershed scale to determine whether water security is a potential problem, and if so, under what conditions it is likely to occur. This methodology makes use of a GIS-based spatial water budget model for simulating stream water availability, water use and stream flow control on a daily basis at a watershed scale. Here, we analysed water availability under three plausible development scenarios for the 3246 ha Cabuyal River watershed in southwest Colombia in the year 2025: Corporate Farming (CF), Ecological Watershed (EW), and Business as Usual (BU). Simulated average river flows at the watershed outlet were, respectively, 874, 796 and 925 l s⁻¹ for the CF, EW and BU scenarios. The contribution of base flow to river flow (base flow index) was on average, 80.8, 85.6 and 77.9%, respectively, for the three scenarios. The watershed had the potential to meet the anticipated increase in water use under each explorative scenario. However, dams were necessary to store irrigation water in the CF scenario, otherwise over 60% of the available water would have been used during the dry season. Such a high figure raises concerns about effects on aquatic and riparian ecology, concentrations of potential contaminants, water reserves for especially low rainfall years, and the watershed resilience to meet temporarily higher water needs during the day. Analyses indicated that current water-use conflicts in the watershed can be resolved if irrigation water supply is separated from drinking water supply. This study helped reduce some of the complexity associated with the interdependencies between land and water resources, the impact of using them, and spatial linkages within the watershed. Results of this study can be used for teaching local stakeholders about basic landscape responses and helping multi-institutional alliances to become proactive and to guide development to the benefit of local communities.  相似文献   

Operational limits to the Priestley-Taylor formula   总被引：4，自引：0，他引：4  

K. J. McAneney  B. Itier 《Irrigation Science》1996,17(1):37-43

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Unravelling the impacts of disturbance type and regeneration on movement of threatened species     

Finnegan  Laura  Viejou  Rebecca  MacNearney  Doug  Pigeon  Karine E.  Stenhouse  Gordon B. 《Landscape Ecology》2021,36(9):2619-2635

Landscape Ecology - Anthropogenic disturbance alters animal movements. Large mammals require vast areas to meet their needs, and they encounter anthropogenic disturbances frequently during daily...  相似文献   

Exploring the common ground of landscape ecology and landscape archaeology through a case study from eastern Anatolia,Turkey     

Arıkan  Bülent  Mohr  Franziska  Bürgi  Matthias 《Landscape Ecology》2021,36(8):2295-2315

Landscape Ecology - Landscape archaeology has a lot to offer to landscape ecology, being an interdisciplinary approach that emphasizes the study of long-term human–environment dynamics. We...  相似文献   

How to consider history in landscape ecology: patterns,processes, and pathways     

Tappeiner  Ulrike  Leitinger  Georg  Zariņa  Anita  Bürgi  Matthias 《Landscape Ecology》2021,36(8):2317-2328

Landscape Ecology - Landscape ecology early on developed the awareness that central objects of investigation are not stable over time and therefore the historical dimension must be included, or at...  相似文献   

Habitat suitability and connectivity modeling reveal priority areas for Indiana bat (Myotis sodalis) conservation in a complex habitat mosaic     

Cable  Ashleigh B.  O’Keefe  Joy M.  Deppe  Jill L.  Hohoff  Tara C.  Taylor  Steven J.  Davis  Mark A. 《Landscape Ecology》2021,36(1):119-137

Context

Conservation for the Indiana bat (Myotis sodalis), a federally endangered species in the United States of America, is typically focused on local maternity sites; however, the species is a regional migrant, interacting with the environment at multiple spatial scales. Hierarchical levels of management may be necessary, but we have limited knowledge of landscape-level ecology, distribution, and connectivity of suitable areas in complex landscapes.

Objectives

We sought to (1) identify factors influencing M. sodalis maternity colony distribution in a mosaic landscape, (2) map suitable maternity habitat, and (3) quantify connectivity importance of patches to direct conservation action.

Methods

Using 3 decades of occurrence data, we tested a priori, hypothesis-driven habitat suitability models. We mapped suitable areas and quantified connectivity importance of habitat patches with probabilistic habitat availability metrics.

Results

Factors improving landscape-scale suitability included limited agriculture, more forest cover, forest edge, proximity to medium-sized water bodies, lower elevations, and limited urban development. Areas closer to hibernacula and rivers were suitable. Binary maps showed that 30% of the study area was suitable for M. sodalis and 29% was important for connectivity. Most suitable patches were important for intra-patch connectivity and far fewer contributed to inter-patch connectivity.

Conclusions

While simple models may be effective for small, homogenous landscapes, complex models are needed to explain habitat suitability in large, mixed landscapes. Suitability modeling identified factors that made sites attractive as maternity areas. Connectivity analysis improved our understanding of important areas for bats and prioritized areas to target for restoration.

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Diagnostic and public health investigation of Mycobacterium tuberculosis infection in a dog in Ontario,Canada     

Luke A. J. Haydock  Anthony C. G. Abrams-Ogg  J. Scott Weese  Michael R. Goldstein  Amy B. Clifford  Adrian Sebastian  Elizabeth H. Rea  Frances B. Jamieson  Carla Duncan  Olga Andrievskaia  Mirjana Savic  Durda Slavic  Robert A. Foster  Christopher J. Greenwood  Tamara L. MacDonald  Jacqueline E. Scott  Andrea Sanchez 《Journal of veterinary diagnostic investigation》2022,34(2):292

A 4-y-old, female mixed-breed dog was presented to the Ontario Veterinary College for further evaluation of multiple pulmonary and hepatic masses, intrathoracic lymphadenitis, and recent development of a pyogranulomatous pleural effusion. Along with other comprehensive tests, a thoracic lymph node biopsy was performed, and Mycobacterium tuberculosis complex infection was confirmed by real-time PCR. The dog’s condition declined post-operatively, and euthanasia was elected. Postmortem examination confirmed severe granulomatous pneumonia, hepatitis, intrathoracic and intraabdominal lymphadenitis, omentitis, and nephritis. Line-probe assays performed on samples collected postmortem confirmed the species as M. tuberculosis. 24-loci MIRU-VNTR genotyping, spoligotyping, and whole-genome sequencing revealed relations to known human isolates, but no epidemiologic link to these cases was investigated. Given the concern for potential human exposure during this animal’s disease course, a public health investigation was initiated; 45 individuals were tested for M. tuberculosis exposure, and no subsequent human infections related to this animal were identified. Our case highlights the need for more readily available, minimally invasive testing for the diagnosis of canine mycobacteriosis, and highlights the ability of canid species to act as potential contributors to the epidemiology of M. tuberculosis infections.  相似文献   

Improving Drought Tolerance of Rice by Designed QTL Pyramiding   总被引：4，自引：0，他引：4  

Drought is the most important factor limiting rice yields in the rainfed areas of Asia. To overcome the problem  we developed a new strategy ''''designed QTL pyramiding'''' to more efficiently develop drought tolerant 《分子植物育种》2007,5(2):205-206

Drought is the most important factor limiting rice yields in the rainfed areas of Asia. To overcome the problem, we developed a new strategy ＇designed QTL pyramiding＇ to more efficiently develop drought tolerant （DT） rice cultivars. In the first phase of this strategy, we developed large numbers of introgression lines （ILs） in elite backgrounds using backcross （BC） breeding, each of which carries multiple genomic segments for improved DT from a known donor. Then, we genotyped all ILs with SSR markers to track the genomewide pattern of introgression in the DT ILs of 16 BC populations derived from crosses between 2 recipients （IR64 and Teqing） and four different donors. X^2 tests and linkage disequilibrium analyses of introgression in the DT ILs revealed significant frequency shifts at many loci across the genome and non-random associations at the multilocus level as a result of selection for DT in the ILs, which led us to the discovery of putative genetic networks underlying DT in the ILs. The networks each containing all DT loci detected in ILs from a BC population showed some interesting features.  相似文献   

TILLING and Ecotilling the Plant Kingdom     

The modern crop scientist has a large amount of available nucleotide sequence information to identify genes of potential agronomic importance.…… 《分子植物育种》2007,5(2):238-239

The modem crop scientist has a large amount of available nucleotide sequence information to identify genes of potential agronomic importance. Using reverse genetic approaches, specific genes can be disrupted, and hypotheses regarding gene function directly tested in vivo. Although a number of reverse genetic methods have been introduced, many are limited in application because they are organism-specific, expensive, transgenic, or only transiently disrupt gene function. However, traditional mutagenesis using chemical mutagens has been widely used as a forward genetics strategy to create many new crop plant varieties at relatively low cost. Mutagens such as ethyl methanesulphonate （EMS） cause stable point mutations and thus produce an allelic series of truncation and missense changes that can provide a range of phenotypes （Greene et al., 2003）. TILLING （targeting induced local lesions IN genomes） is a high-throughput reverse genetic strategy that combines traditional mutagenesis and SNP discovery methods （Colbert et al., 2001; McCallum et al., 2000）. To identify mutations, target regions of-l.5 kb are amplified with fluorescently labeled gene specific primers. Heteroduplexes are then formed between wild-type and mutant strands, mismatches are cleaved by incubation with a single-strand specific nuclease,  相似文献