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11.
The process-based model CenW was used to model the growth of Pinus radiata in New Zealand. The model was parameterised by comparison with data from 101 permanent sample plots, consisting of 1309 individual observations of stands at different ages of up to 32 years. The data covered the range of conditions under which P. radiata is grown in New Zealand. Observations consisted of stand density, and height and/or basal area. Input parameters consisted of site water-holding capacity, soil texture and soil nitrogen concentration, and daily records of minimum and maximum air temperatures, precipitation, solar radiation and atmospheric humidity. Using the same plant parameters for the full data set from all locations, we obtained excellent correspondence between predictions and observed data. Model efficiencies ranged from 0.828 to 0.892 for four growth indices that were either directly observed (height, basal area) or derived from the data (stand volume, mean stem diameter).Within New Zealand, stand productivity was found to be particularly sensitive to mean annual air temperature and mean total annual precipitation, with optima reached from 12-15 °C and 1500-2000 mm, respectively. Productivity exhibited little sensitivity to site fertility as soil nutrition was generally adequate for most sites. Spatial projections showed highest productivity in the moderately wet, warm northern and western regions of the North Island and lowest for cold sites at higher elevation, dry eastern areas of the South Island and the extremely wet sites on the West Coast of the South Island. The model runs provided robust estimates of productivity across the diverse environmental conditions in New Zealand. 相似文献
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Michael S. Watt David J. PalmerLindsay S. Bulman 《Forest Ecology and Management》2011,261(11):1792-1798
Despite being a damaging foliar disease of Pinus species little research has characterised spatial variation in disease severity of Dothistroma needle blight at a macroscale. Using an extensive dataset describing Dothistroma needle blight severity (Ssev) on plantation grown Pinus radiata stands distributed widely across New Zealand the objectives of this research were to (i) develop a regression model describing Ssev, (ii) use this model to identify key drivers of Ssev, their functional form and relative importance, and (iii) develop spatial predictions of Ssev for New Zealand P. radiata under current climate. Using an independent validation dataset, the final model accounted for 72% of the variance in Ssev using four significant (P < 0.001) explanatory variables and an isotrophic exponential model to account for the spatial covariance in the data. Ssev was most sensitive to mean air temperature from November to April (TNov-Apr), followed by mean relative humidity from October to April (RHOct-Apr), mean total November rainfall (PNov), and then stand age (A). There was a quadratic correlation between A and Ssev with Ssev increasing to a maxima at 12 years before declining. Ssev exponentially increased to a threshold with increases in both PNov and RHOct-Apr. The relationship between Ssev and TNov-Apr was quadratic with Ssev increasing to a maximum at TNov-Apr of 15.5 °C before declining at higher values of TNov-Apr. Spatial predictions of Ssev varied widely throughout New Zealand. Values of Ssev were highest in moderately warm wet environments in the North Island, and on the west coast of the South Island. In contrast, relatively low values of Ssev were predicted in drier eastern and southern regions of New Zealand. 相似文献
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W. D. Watt 《Water, air, and soil pollution》1987,35(1-2):27-35
Within the present North American range of Atlantic salmon, severe acid rain effects are limited to the Southern Upland area of Nova Scotia. In the Southern Upland, long range transport of H2SO4 has caused many rivers to decline in pH to the point where their Atlantic salmon stocks have been destroyed or much diminished. Chemical records show a declining pH trend in N.S. rivers since the early 1950s. Eighty % of the annual variation in H+ concentration can be accounted for by a multiple linear regression model on excess sulphate, total Al and organic anions. It is technically feasible to restore the acidified salmon habitat by the addition of limestone; the total cost of mounting a liming program to restore the lost habitat has been estimated at $4.75 × 106 yr?1. The pre-acidification Atlantic salmon production capacity of the Southern Upland was estimated from physical habitat surveys and tag return data to be about 45 000 fish yr?1. Acidification has caused a 50% decline to the current production level of about 23 000 fish yr?1. The costs of the liming program, when compared to the economic benefits of the anticipated salmon enhancement, are economically unjustifiable. The eradication of salmon from such large regions will hinder future programs to reestablish the species in their former range when pollution of the atmosphere is eventually brought under control. Present plans are for a small liming program to establish a series of refuges for the preservation of nuclei of native salmon stocks. 相似文献
14.
Mammalian epidermis is maintained by self-renewal of stem cells, but the underlying mechanisms are unknown. Deletion of Rac1, a Rho guanosine triphosphatase, in adult mouse epidermis stimulated stem cells to divide and undergo terminal differentiation, leading to failure to maintain the interfollicular epidermis, hair follicles, and sebaceous glands. Rac1 exerts its effects in the epidermis by negatively regulating c-Myc through p21-activated kinase 2 (PAK2) phosphorylation. We conclude that a pleiotropic regulator of cell adhesion and the cytoskeleton plays a critical role in controlling exit from the stem cell niche and propose that Rac and Myc represent a global stem cell regulatory axis. 相似文献
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Diagnostic tests for small ruminant lentiviruses 总被引:1,自引:0,他引:1
de Andrés D Klein D Watt NJ Berriatua E Torsteinsdottir S Blacklaws BA Harkiss GD 《Veterinary microbiology》2005,107(1-2):49-62
Maedi visna virus and caprine arthritis encephalitis virus are closely related retroviruses that cause chronic inflammatory disease in small ruminants. The infections are characterised by insidious onset and slow progression. Diagnosis of infection is usually by serological testing. A variety of assays are available for this purpose, though the relative sensitivity and specificity of these assays has not been compared systematically. Here we review recent developments in laboratory diagnostic methods and their use in field diagnosis. The results suggest that a combination of ELISA and PCR might afford optimal detection of SRLV infection. 相似文献
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