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191.
This paper suggests that the energy flow on which all living structures depend only started up slowly, the low-energy, initial
phase starting up a second, slightly more energetic phase, and so on. In this way, the build up of the energy flow follows
a bootstrapping process similar to that found in the development of computers, the first generation making possible the calculations
necessary for constructing the second one, etc. In the biogenetic upstart of an energy flow, non-metals in the lower periods
of the Periodic Table of Elements would have constituted the most primitive systems, their operation being enhanced and later
supplanted by elements in the higher periods that demand more energy. This bootstrapping process would put the development
of the metabolisms based on the second period elements carbon, nitrogen and oxygen at the end of the evolutionary process
rather than at, or even before, the biogenetic event. 相似文献
192.
Jacob Bendix 《植被学杂志》1999,10(2):243-252
Abstract. Mechanical damage by floodwaters is frequently invoked to explain the distribution of riparian plant species, but data have been lacking to relate vegetation to specific estimates of flood damage potential. This research uses detailed estimates of unit stream power (an appropriate measure of the potential for mechanical damage) in conjunction with vegetation cover data to test this relationship at 37 valley-bottom sites in the Transverse Ranges of Southern California. A computer program, HEC-2, was used to model the slope and the variation in flow depth and velocity of the 20-yr flood across the sites. Regression models tested the influence of stream power (and of height above the water table) on the woody species composition of 393 4-m cross-section segments of the valley-bottom sites. Results indicate that unit stream power does have a significant effect on the riparian vegetation, but that the amount of that influence and its importance relative to the influence of height above the water table varies between watersheds. Some species are found primarily in locations of high stream power, while others are limited to portions of the valley bottom that experience only low stream power. 相似文献
193.
Man-Lai Tang 《Biometrical journal. Biometrische Zeitschrift》1999,41(7):827-839
An efficient recursive polynomial multiplication method is proposed for exact unconditional power calculation for unordered 2 × K contingency table with up to moderate sample size. Our method can be applied to the family of cell-additive statistics which includes the Freeman-Halton statistic, the Pearson χ2 statistic and the likelihood ratio statistic. We illustrate our proposed method by several numerical examples. 相似文献
194.
A commonly used measure of ordinal association in two-way contingency tables is Goodman and Kruskal's gamma. In a randomized clinical trial setting, the row variable may consist of increasing doses of a drug and placebo (i.e., treatments) and the column variable may be an ordinal response variable (e.g., physician's global evaluation of treatment effectiveness). Typically, patients are randomly assigned to treatments (rows) such that the row totals are fixed and the rows form a product-multinomial sample of the ordinal response variable. For the above situation, we provide the asymptotic variance of gamma using the delta method. The population version of gamma and its standard error can be estimated by their sample counterparts, enabling us to construct approximate tests and confidence intervals using the normal distribution. 相似文献
195.
Seasonal occurrence of Aphis glycines and physiological responses of soybean plants to its feeding 总被引:1,自引:0,他引:1
The soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) is an important pest of soybean in China. To monitor and manage this pest effectively it is neces-sary to understand its population dynamics and demographics, as well as the physiological responses of soybean plants to its feeding. In this study, using field surveying and suction-trap monitoring, we investigated the population dynamics of the soybean aphid in Xiuyan County, Liaoning Province in northeastern China during 2009-2012. The results indicatedthat the population dynamics of the soybean aphid followed a unimodal curve distribution, with the insect generally colonizing soybean fields from the middle of June to early Julyand the population reaching a peak between early July and early August. On the whole, soybean aphids occurred in suction-traps at least 2 weeks earlier than they were foundin field surveys. A total of 72 alates were collected by suction-trapping over the 4 years, with the earliest alate captures occurring on 28 May in 2009, 2011, 2012 and 4 June in 2010. The life table parameters clearly showed that this aphid had a short doubling time (4.73 ± 0.21 days), and 7.36± 0.98 nymphs were produced by a soybean aphid adult during its lifetime (13.57 ± 0.30 days). Finally, biochemical assays indicated that the amount of malondialdehyde and the activities of four defense-related enzymes in soybean leavessignificantly changed between 0 day and 7 days of aphid infestation. Polyphenol oxidase (PPO) and catalase (CAT) activities increased more dramatically after 1 day of aphid feed-ing. In addition, significantly higher levels of superoxide dismutase and CAT were found after aphid feeding for 7 days, whereas there was no significant change in the activitiesof peroxidase and PPO. Consequently, this study will be beneficial in determining the seasonal occurrence of the soybean aphid and selecting insect-resistant soybean varieties,and thus in developing a theoretical framework for appropriate management strategies. 相似文献
196.
Every proposed vegetation classification is sooner or later confronted with an accumulation of new data, which has to be assigned to existing vegetation units. Calculation of similarity indices between new relevés (vegetation plots) and constancy columns of established vegetation units is a suitable method for computerised assignment of relevés to these units. This paper compares several similarity indices using simulated data set where either randomly distributed or diagnostic species prevail in the species composition of the tested relevé. Traditional indices, based only on species composition, produce different results than similarity indices that consider species fidelity. However, both types of indices failed in some situations and thus cannot be widely accepted as suitable methods of additional relevé assignment. Therefore a combined Frequency-Positive Fidelity Index (FPFI) is proposed. This new index includes compositional similarity of an assigned relevé with vegetation unit and retains the advantages and lacks the disadvantages of tested indices. The calculation of all these indices is available in the JUICE program (http://www.sci.muni.cz/botany/juice.htm). 相似文献
197.
Large numbers of epiphytes are extracted from cloud forests for ornamental use and illegal trade in Latin America. We examined the potential effects of different harvesting regimes on the population dynamics of the epiphytic bromeliads Tillandsia multicaulis and Tillandsia punctulata. The population dynamics of these species were studied over a 2-year period in a tropical montane cloud forest in Veracruz, Mexico. Prospective and retrospective analyses were used to identify which demographic processes and life-cycle stages make the largest relative contribution to variation in population growth rate (λ). The effect of simulated harvesting levels on population growth rates was analysed for both species. λ of both populations was highly influenced by survival (stasis), to a lesser extent by growth, and only slightly by fecundity. Vegetative growth played a central role in the population dynamics of these organisms. The λ value of the studied populations did not differ significantly from unity: T. multicaulis λ (95% confidence interval) = 0.982 (0.897–1.060) and T. punctulata λ = 0.967 (0.815–1.051), suggesting population stability. However, numerical simulation of different levels of extraction showed that λ would drop substantially even under very low (2%) harvesting levels. Matrix analysis revealed that T. multicaulis and T. punctulata populations are likely to decline and therefore commercial harvesting would be unsustainable. Based on these findings, management recommendations are outlined. 相似文献
198.
RAT BLGN 《Molecular ecology resources》2007,7(3):416-417
A simple Microsoft Excel Macro application (kgtests) that performs the k and g tests for detecting population expansion is described. The application, being an Excel Macro, facilitates the ease of preparation of the input file and makes it possible to use the application in any machine that can run Excel. 相似文献
199.
Kai‐Yun Wang Yong Zhang Hong‐Yan Wang Xiao‐Ming Xia Tong‐Xian Liu 《Insect Science》2008,15(6):569-576
Development, survivorship, pupal weight, oviposition, and life table parameters of the oriental tobacco budworm, Helicoverpa assulta Guenée, were evaluated in the laboratory on an artificial diet, pepper (Capsicum frutescens L.), and tobacco (Nicotiana tobacum L.). We found that the average developmental time of immature stages was longest on tobacco (36.2 d), intermediate on pepper (34.4 d), and shortest on artificial diet (33.5 d). Immature survival from egg to pupa varied from 31% on tobacco, 43% on pepper, and 74% on artificial diet. Pupal weight ranged from 197.4 mg/pupa on tobacco, 233.1 mg/pupa on pepper and 253.4 mg/pupa on artificial diet. The average numbers of eggs laid by adults reared as larvae on the artificial diet, pepper, or tobacco were 614, 421 and 334 eggs/female, respectively. Numbers of remaining eggs in ovaries of the adult females reared as larvae on the artificial diet, pepper, or tobacco were 16, 26, and 42 eggs/female, respectively. The longevity of adult females developed from larvae reared on the three diets was not significantly different, whereas the longevity of male adults from the larvae reared on artificial diet was longer (16.8 d) than that for males reared on tobacco (13.8 d) and pepper (13.3 d). The intrinsic, finite, gross, and net rates of increase were highest for females reared as larvae on artificial diet, lowest for females emerging from larvae reared on tobacco, and intermediate for females emerging from larvae reared on pepper. Generation times and doubling time of H. assulta were shortest for larvae fed artificial diet, intermediate from larvae reared on pepper, and longest from larvae reared on tobacco. We concluded that the artificial diet was the most suitable larval diet of H. assulta followed by pepper, and tobacco. 相似文献
200.
Hwijong Yi Soondo Bae Jin Kyo Jung Gil‐Hah Kim Yonggyun Kim Youngnam Yoon Yunwoo Jang Tae‐Wook Jung Rameswor Maharjan 《Entomological Research》2019,49(11):483-489
The soybean pod borer, Maruca vitrata is one of the key insect pests of tropical legumes. It damages tender leaf axils, flower buds, flowers and pods by webbing and boring clusters of flowers and pods. In this study, we investigated the survival and life table parameters of M. vitrata on several leguminous crops; soybean (cvs. Daewon, Poongsannamool and Socheongja), azuki bean (cv. Hongeon), mung bean (cv. Sanpo), and cowpea (cv. Jangchae), compared to artificial diet to assess the antibiosis resistance to M. vitrata. The life‐variables of M. vitrata were significantly affected by the tested legume cultivars. None of the larvae fed cowpea cultivar Jangchae survived. The azuki bean cultivar Hongeon and mung bean cultivar Sanpo were found susceptible to M. vitrata, whereas cowpea cultivar Jangchae and soybean cultivar Daewon showed antibiosis resistance to M. vitrata. Further studies should examine the chemicals associated with leguminous crop cultivars and its mechanism to develop a control method against M. vitrata. 相似文献