Complexity in modelling forest ecosystems: How much is enough?   总被引：1，自引：0，他引：1  

James P. Kimmins  Juan A. Blanco  Brad Seely  Clive Welham  Kim Scoullar 《Forest Ecology and Management》2008

The levels-of-integration concept in ecology suggests that while the population and community levels of biological organization provide understanding, they do not provide an adequate basis for predicting future states of populations, communities or ecosystems. Empirical models of populations and communities are implicitly ecosystem level because they are based on measures of the results of all past determinants that affected the populations and communities in question. They can be good predictors under unchanging conditions, but they are not able to predict for changing conditions, which requires the explicit representation of those ecological processes that are anticipated to change. The question addressed in this paper is: how does the performance of a “simple” stand-level model change as representations of these processes are added, and how much complexity is enough? Examples are given of change in performance of the ecosystem management model FORECAST run as a light competition model as nutrient regulation of growth and understory interactions are added singly or in combination. These examples are framed in comparisons of simulations for a white spruce stand in the in boreal mixedwood region in northern British Columbia, for a long-term thinning-fertilization trial in a Douglas-fir stand on southern Vancouver Island, and for yield decline in Chinese fir in south eastern China. It is concluded that the effect of adding complexity on the predictions of this model depends on the time scale of the simulation and the management or natural disturbance regime that is being simulated. The results supported Occam's razor: that models should be as simple as possible but as complex as necessary.  相似文献   

Long lasting rubber tree resistance to Microcyclus ulei characterized by reduced conidial emission and absence of teleomorph     

Vincent Le Guen  Jean Guyot  Carlos Raimundo Reis Mattos  Marc Seguin  Dominique Garcia 《Crop Protection》2008,27(12):1498-1503

The resistance of the MDF 180 Hevea brasiliensis cultivar to South American leaf blight caused by Microcyclus ulei has been studied under both controlled conditions of inoculation, and under natural infestation in the Brazilian state of Bahia. Inoculated isolates on this cultivar in most cases developed sporulating lesions and produced conidiospores, but at a moderate level, characteristic of a race non-specific, partial resistance. The teleomorph of M. ulei has never been reported on this cultivar, either in controlled conditions or in natural infestation, whereas it is commonly observed on other susceptible cultivars. This type of resistance has seldom been described for other pathosystems. MDF 180 resistance having also endured for more than 30 years in areas very conducive to the disease can, therefore, be described as a durable resistance. Rubber productivity of this cultivar is not sufficient to allow planting on industrial scale, but its resistance characteristics make it a good progenitor candidate for rubber tree resistance breeding programs.  相似文献   

A transgenic durum wheat line that is free of marker genes and expresses 1Dy10     

Agata Gadaleta  Angelica Giancaspro  Ann E. Blechl  Antonio Blanco 《Journal of Cereal Science》2008

As currently practiced, genetic engineering of monocots requires the use of selective agents, such as herbicides and antibiotics, and marker genes for resistance to favor the multiplication of the initially transformed cells. In the present paper we have used “minimal gene cassettes” and positive selection to generate transgenic durum wheat lines free of herbicide and antibiotic resistance marker genes. Two biolistic transformation experiments were carried out using three “minimal gene cassettes” consisting of linear DNA fragments each excised from the source plasmids. The targeted trait genes were two bread wheat sequences encoding the Dx5 and Dy10 high-molecular-weight (HMW) glutenin subunits, which have been associated with superior bread-making quality and which are absent from durum wheats. The positive selectable marker was the Escherichia coli phosphomannose isomerase (pmi) gene, whose product catalyzes the reversible interconversion of mannose-6-phosphate and fructose-6-phosphate, allowing plant cells to utilize mannose as a carbon source. PCR assays of genomic DNA from regenerated plants identified 15 T₀ plants that contained the pmi marker gene for an overall transformation efficiency of 1.5%, which is similar to biolistic transformation efficiencies of durum wheat with intact circular plasmids. Line TC-52, which initially contained pmi, non-expressed 1Dx5, and expressed 1Dy10 HMW glutenin subunit transgenes, was further investigated. PCR was used to follow inheritance of the pmi marker gene and 1Dx5 from the T₁ to T₃ generations. Transgene expression was monitored by the chlorophenol-red assay for pmi and SDS-PAGE of seed proteins for 1Dy10. From these analyses, we observed that the 1Dy10, 1Dx5 and pmi transgenes were not linked, allowing us in the T₃ generation to identify 1Dy10 transgenic segregants that contained no marker or silent 1Dx5 transgenes. Homozygotes containing and expressing only the 1Dy10 transgene were identified in the T₄ generation. These experiments show that it is possible to combine biolistic transformation by minimal gene cassettes with genetic segregation to make marker-free transgenic wheat plants with new traits.  相似文献   

Design and Validation of Strategy to Increasing the Rate Calving in Traditional Production System Livestock of Michoac~n M~xico Tropical Dry     

G. Salas  E. Garcia  M. Perea  R. Garciduefias  E. Gutierrezl  A. Caratachea  J. P. Flores 《农业科学与技术》2011,(8):1204-1206

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Pasture‐based dairy farm systems increasing milk production through stocking rate or milk yield per cow: pasture and animal responses     

S. R. Fariña  S. C. Garcia  W. J. Fulkerson  I. M. Barchia 《Grass and Forage Science》2011,66(3):316-332

A 2‐year whole‐farm study compared pasture‐based systems increasing milk production per ha by increasing either stocking rate (from 2·5 to 3·8 cows ha^?1) or milk yield per cow (from 6000 to 9000 kg cow^?1 lactation^?1) or both. Four treatments (systems), comprising 30 cows each, were compared under the same management and grazing decision rules. The diet was based on grazed pasture, whereas pellets and conserved fodder were fed when deemed necessary. Milk production per ha increased by 0·49, 0·1 and 0·66 in the systems that increased either stocking rate, milk yield per cow or both respectively. Cows in the ‘high milk yield per cow’ systems had a significantly higher body condition score throughout the lactation, but reproductive performance was similar among all groups. Total pasture utilized (11 t DM ha^?1 year^?1) and pasture nutritive value were similar across all systems. This was associated with the grazing rules applied and the ability of accurately supplementing to meet deficits in available pasture. At the whole‐system level, there was a higher marginal efficiency of supplement use when increasing stocking rate than when increasing milk yield per cow or increasing both (0·18, 0·07 and 0·12 kg milk MJ^?1 of metabolizable energy of supplements respectively).  相似文献   

High?throughput phenotyping of two plant?size traits of Eucalyptus species using neural networks     

Marcus Vinicius Vieira Borges  Janielle de Oliveira Garcia  Tays Silva Batista  Alexsandra Nogueira Martins Silva  Fabio Henrique Rojo Baio  Carlos Ant?nio da Silva Junior  Gileno Brito de Azevedo  Glauce Taís de Oliveira Sousa Azevedo  Larissa Pereira Ribeiro Teodoro  Paulo Eduardo Teodoro 《林业研究》2022,(2):591-599

In forest modeling to estimate the volume of wood, artificial intelligence has been shown to be quite effi-cient, especially using artificial neural networks (A...  相似文献   

Genetic gain in agronomic traits of common bean in the region of Planalto Catarinense     

Juliano Garcia Bertoldo  Leiri Daiane Barili  Naine Martins do Vale  Jefferson Luís Meirelles Coimbra  Diego Stähelin  Altamir Frederico Guidolin 《Euphytica》2010,171(3):381-388

The purpose of this study was to predict the genetic progress in the selection for common bean agronomic traits based on the trait expression, using two indices of adaptive selection. The existence of correlation between various traits in common bean breeding is a major restriction, but some tools that allow breeders to predict the expected gains could optimize results. The following traits were evaluated: (1) plant cycle (days), (2) plant height (in cm), (3) stem diameter (cm), (4) insertion of the first pod (cm); (5) number of pods per plant; (6) number of grains per pod; (7) pod length (cm). Results show the possibility of selecting accessions for several agronomically important traits evaluated together. The only genotype selected by both indices was UDESC 03, confirming the possibility of selecting plants with superior agronomic traits among genotypes of common bean landraces.  相似文献   

Influence of rice development on the function of bacterial blight resistance genes     

Kimberly M. Webb  Epifania Garcia  Casiana M. Vera Cruz  Jan E. Leach 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(3):399-407

Disease resistance genes most commonly used in breeding programs are single, dominant genes with relative effectiveness that is sometimes influenced by plant developmental stage. Knowing the developmental stages at which a resistance gene is functional is important for disease management. In rice, resistance at the seedling stage is crucial, because wounding during transplanting increases the potential for bacterial blight disease, and not all bacterial blight resistance genes are effective at the seedling stage. Effectiveness of the bacterial blight resistance genes Xa4, xa5, and Xa7, all in a common genetic background, was evaluated at different developmental stages by measuring lesion length and bacterial numbers after inoculation with the bacterial pathogen, Xanthomonas oryzae pv. oryzae. The Xa4 and xa5 genes controlled disease at all growth stages. In contrast, Xa7 was not fully functional in very young seedlings, but was completely effective by 21 days after sowing (das). The effects of plant developmental stage on interactions of the Xa7 gene with X. oryzae pv. oryzae strains carrying different mutant avrXa7 alleles were also tested. If a partial or fully functional avrXa7 allele was present, Xa7 resistance was effective at all growth stages tested after the transplant stage (>21 das).  相似文献   

Post-bloom thinning of peaches for canning with hand-held mechanical devices   总被引：1，自引：0，他引：1  

B. Martín  A. Torregrosa  J. Garcia Brunton 《Scientia Horticulturae》2010

Peaches for the canning industry were thinned by hand and with hand-held mechanical devices (one branch brusher and one pneumatic branch shaker) that were used alone and/or combined with hand thinning. Hand thinning was the most time-consuming thinning technique and it was also the most expensive (25 and 30 min tree⁻¹ and 3.43 and 4.11 € tree⁻¹ in 2008 and 2009, respectively). The pneumatic branch shaker together with follow-up hand thinning reduced the time needed to complete the task by 28% at a cost of 2.55 € tree⁻¹ relative to hand thinning (control), but this technique did not remove enough of the green fruit from the trees. A brusher device combined with conventional hand thinning reduced time by 46% with respect to the control at a cost of 1.93 € tree⁻¹. To improve this procedure, workers were instructed to detach only fruits on clusters in follow-up hand thinning and to work directly from the ground without the use of ladders. Accordingly, a time reduction of 82% was achieved at a cost of 0.77 € tree⁻¹ under these conditions.  相似文献   

Correlation of ethylene synthesis in Citrus fruits and their susceptibility to Alternaria alternata pv. citri     

A. Ortuo  I. Nemsa  N. Alvarez  A. Lacasa  I. Porras  A. Garcia Lidn  J.A. Del Río 《Physiological and Molecular Plant Pathology》2008,72(4-6):162-166

The susceptibility of Fortune (Citrus clementina × Citrus reticulata), Citrus paradisi and Citrus limon fruits to Alternaria alternata pv. citri was investigated using different artificial inoculation methods. The results obtained reveal that the C. paradisi and C. limon fruits are less susceptible to A. alternata pv. citri than Fortune fruits, although all showed symptoms of Alternaria brown spot when the cuticle was broken and the flavedo or flavedo + albedo was removed. Furthermore, it was seen that susceptibility to the fungus decreased as the age of the fruit increased. There was a positive correlation between the susceptibility of the different Citrus fruits to A. alternata pv. citri and their “in vivo” ethylene levels, the most susceptible fruit (Fortune) producing more ethylene during growth than the less susceptible C. limon and C. paradisi. This suggests that ethylene may well be considered as a possible marker of Citrus fruit susceptibility to A. alternata pv. citri. Disease development increased when the Fortune fruits were treated with 1 mM ACC (a precursor of ethylene biosynthesis) or 1 mM Ethephon (an ethylene-releasing compound) prior to inoculation with A. alternata pv. citri. The role of ethylene as a factor involved in disease development is discussed.  相似文献