A reevaluation of alternate bearing in pistachio     

Todd S. Rosenstock  Uriel A. Rosa  Richard E. Plant  Patrick H. Brown 《Scientia Horticulturae》2010

Studies documenting pistachio fruiting patterns (Pistacia vera L.) conclude this species shows evidence of alternate bearing; fruit production fluctuates between an ‘on’ year of high yields and an ‘off’ year of low yields. However, alternate bearing in pistachio has never been statistically tested. We collected yields of 4288 trees over six years to test for alternate bearing in a mature orchard planted with ‘Kerman’ scions grafted onto P. integerrima rootstock – the combination planted on the bulk of the acreage in California. A majority (58%) of the trees exhibited statistically significant alternate bearing patterns. Yet 42% showed yield patterns that were indistinguishable from random fluctuations, the standard measure of alternate bearing (I) was only modest (mean I = 0.48), and I varied considerably among trees (range = 0.04–0.83). These findings support that pistachio shows alternate bearing behavior but suggest alternate bearing is less ubiquitous and fruiting patterns are more complex than previously suspected. The presence of such a diversity of yield dynamics creates considerable challenges for crop management and research.  相似文献   

Wetlands: conservation's poor cousins          下载免费PDF全文

Richard T. Kingsford  Alberto Basset  Leland Jackson 《水产资源保护:海洋与淡水生态系统》2016,26(5):892-916

Balanced exploitation and coexistence of interacting,size‐structured,fish species          下载免费PDF全文

Richard Law  Michael J. Plank  Jeppe Kolding 《Fish and Fisheries》2016,17(2):281-302

This paper examines some effects of exploitation on a simple ecosystem containing two interacting fish species, with life histories similar to mackerel (Scomber scombrus) and cod (Gadus morhua), using a dynamic, size‐spectrum model. Such models internalize body growth and mortality from predation, allowing bookkeeping of biomass at a detailed level of individual predation and growth and enabling scaling up to the mass balance of the ecosystem. Exploitation set independently for each species with knife‐edge, size‐at‐entry fishing can lead to collapse of cod. Exploitation to achieve a fixed ratio of yield to productivity across species can also lead to collapse of cod. However, harvesting balanced to the overall productivity of species in the exploited ecosystem exerts a strong force countering such collapse. If balancing across species is applied to a fishery with knife‐edge selection, size distributions are truncated, changing the structure of the system and reducing its resilience to perturbations. If balancing is applied on the basis of productivity at each body size as well as across species, there is less disruption to size‐structure, resilience is increased, and substantially greater biomass yields are possible. We note an identity between the body size at which productivity is maximized and the age at which cohort biomass is maximized. In our numerical results based on detailed bookkeeping of biomass, cohort biomass reaches its maximum at body masses <1 g, unlike standard yield‐per‐recruit models, where body growth and mortality are independent externalities, and cohort biomass is maximized at larger body sizes.  相似文献   

Is spawning stock biomass a robust proxy for reproductive potential?          下载免费PDF全文

Laurence T Kell  Richard D M Nash  Mark Dickey‐Collas  Iago Mosqueira  Cody Szuwalski 《Fish and Fisheries》2016,17(3):596-616

Reference points based on fishing mortality (F) and spawning stock biomass (SSB) are a requirement of many fisheries management frameworks. SSB is assumed to be a proxy for stock reproductive potential (SRP). Limit reference points based on SSB are used to indicate the level of biomass below which productivity is affected. SSB fails to account for changes in fecundity, egg viability and sex ratio, and it has been argued that total egg production (TEP) provides a better reflection of SRP. We explore how accounting for TEP impacts limit reference points and evidence for a relationship between stock and recruit. Time series of SSB and TEP are compared for three North Sea stocks: cod (Gadus morhua), herring (Clupea harengus) and plaice (Pleuronectes platessa). Dynamics based on TEP are different from those based on SSB for cod and plaice, but the stock–recruit relationships were not ‘improved’ using TEP. Shifts in productivity (spawner per recruit) occur in all three time series and SSB underestimated uncertainty. Yet again, it was shown that assumptions of stationarity about fish population productivity are incorrect. We argue that the use of TEP does improve the realism in our understanding of stock dynamics, and demographically, more complex management strategy evaluation is required to develop management procedures that are robust to uncertainty and integrate F and the demographic health of a stock. Empirical feedback control systems based on fisheries independent indices including surveys of eggs, larvae, recruits, juveniles or spawning adults should be evaluated and compared to traditional approaches.  相似文献   

Is risk consistent across tier‐based harvest control rule management systems? A comparison of four case‐studies          下载免费PDF全文

Catherine M Dichmont  André E Punt  Natalie Dowling  José A A De Oliveira  Lorne R Little  Miriana Sporcic  Elizabeth Fulton  Rebecca Gorton  Neil Klaer  Malcolm Haddon  David C Smith 《Fish and Fisheries》2016,17(3):731-747

There can be substantial differences in data quality and quantity among fished species. Consequently, the quality and type of assessments can also vary substantially. However, all species, especially those that are targeted, need to be managed. Several jurisdictions have developed hierarchical tier systems that categorize stocks based on, for example, the data available for assessment purposes and/or the extent to which quantities on which management advice is based can be estimated. Four case‐studies (Australia's Southern and Eastern Scalefish and Shark Fishery, the USA west coast groundfishery, the USA Alaskan crab fishery and EU fisheries) are used to contrast the types of hierarchical tier systems available, and to assess the extent to which each system constrains risk to be equivalent among the tiers (termed risk equivalency). Only the Australian system explicitly aims to achieve risk equivalency. However, this intent has not been fully operationalized. Our review reveals that best practice is not to define tiers simply on data availability, but also on what the assessments based on those data are capable of estimating. In addition, clearly differentiating the quantification of uncertainty from how decision‐makers wish to address that uncertainty would simplify justification of buffers (the gap between the assessment‐produced target catch or effort and the final management decision that accounts for uncertainty and risk). Risk equivalency can be achieved using management strategy evaluation to select the values for control variables, which determine the buffer given the uncertainty associated with the assessment.  相似文献   

Identification of <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> disease resistance in chickpea genotypes     

Wenhua Du  Xiaochun Zhao  Tokachichu Raju  Phil Davies  Richard Trethowan 《Euphytica》2012,186(3):697-704

Ascochyta blight (AB) disease, caused by the fungus Ascochyta rabiei, is a major yield limiting factor of chickpea in Australia and around the world. The aggressiveness of six A. rabiei isolates was identified using 3 chickpea varieties (Jimbour, Flipper and Yorker). These AB isolates were isolated from chickpea fields in northern NSW, one of the major chickpea production regions in Australia. Each of the six isolates produced a different aggressiveness pattern and isolate 4859 was found to be the most aggressive. The AB resistance in 16 international and Australian chickpea genotypes was then investigated by inoculating the plants with the most aggressive isolate and a mixture of the other 5 isolates. Resistance to both the most aggressive isolate and the mixed isolates has been identified in 5 genotypes (ICCV 98813, Flipper, ICCV 05111, ICCV 98801, Jimbour #1) while 10 entries (Howzat, ICCV 06108 and ICCV 98818, Jimbour, ICCV 96852, ICCV 06107, ICCV 98816, Yorker, FLIP97-114C, ICCV 96853) were moderately resistant. Only one genotype (Bumper) appeared to be susceptible to both inoculums. There was large variation observed in the pathogenicity of the isolates suggesting that the six AB isolates represent several different pathogen strains. Significant differences in leaf infection rate, plant infection rate, plant death rate and disease development were identified among the chickpea genotypes tested. These findings suggest that these chickpea genotypes carry different resistant genes, which can be exploited in breeding programmes to develop high levels of disease resistance.  相似文献   

Food insecurity and maternal depression in rural, low-income families: a longitudinal investigation     

Huddleston-Casas C  Charnigo R  Simmons LA 《Public health nutrition》2009,12(8):1133-1140

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Laboratory and field testing of an automated tension infiltrometer     

Cedric Kechavarzi  Kamila &#x;pongrov  Marc Dresser  Svatopluk Matula  Richard J. Godwin 《Biosystems Engineering》2009,104(2):266-277

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A Numbering System for Labelling Trees and Stumps     

E. C. S. Little 《国际虫害防治杂志》2013,59(1)

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Current knowledge on plant/canopy architectural traits that reduce the expression and development of epidemics     

Bernard Tivoli  Agnès Calonnec  Benjamin Richard  Bertrand Ney  Didier Andrivon 《European journal of plant pathology / European Foundation for Plant Pathology》2013,135(3):471-478

To reduce the use of pesticides, innovative studies have been developed to introduce the plant as the centre of the crop protection system. The aim of this paper is to explain how architectural traits of plants and canopies induce a more or less severe epidemic and how they may be modified in order to reduce disease development. In particular, it focuses on three key questions: i) which processes linked to epidemics can be influenced by architecture ii) how can architecture be characterized relative to these modes of action, and iii) how can these effects be explored and exploited? The roles of plant/canopy architecture on inoculum interception, on epidemic development via the microclimate and on tissue receptivity are discussed. In addition, the concepts of disease avoidance, canopy porosity and an ideotype unfavourable for disease development are described. This paper shows that many advances have already been made, but progress is still required in four main fields: microclimatology, mathematical modelling of plants, molecular genetics and ideotype conception.  相似文献