On Difficulties with Replacement-Series Methodology in Mixture Experiments

Yong, Taiwen; Yang, Wenyu; Xiang, Dabing; Chen, Xiaorong

doi:10.2307/2403086

Cited by 223 publications

(174 citation statements)

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“…This considers potential interaction between density and species ratios, and has been recommended for competition studies between two species (Fairbank and Watkinson 1985;Connolly 1986;Gibson et al 1999;Sher et al 2000). Cottonwood to saltcedar ratios used in the interspecific study were 2:2, 2:4, 5:15, 10:20, and 15:25 plants/0.25 m 2 .…”

Section: Methodsmentioning

confidence: 99%

Seedling competition between native cottonwood and exotic saltcedar: implications for restoration

2008

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Altered hydrology of southwestern United States rivers has led to a decline in native cottonwood (Populus deltoides). Areas historically dominated by cottonwood have been replaced by invasive saltcedar (Tamarix chinensis). Restoration of historic hydrology through periodic flooding of riparian areas has been a means of restoring native species. However, due to similarity in germination requirements of cottonwoods and saltcedars, flooding may create an unwanted increase in the number of saltcedar seedlings. Therefore, we evaluated competitive aspects of these cooccurring species in an extant riparian habitat in the arid southwestern US. We measured effects of competition between cottonwood and saltcedar seedlings and among cottonwood seedlings during the first growing season following seedling establishment in 360, 0.5 9 0.5-m plots at the Bosque del Apache National Wildlife Refuge, New Mexico. We used five interspecific density treatments and five intraspecific density treatments. Cottonwood seedling biomass and height were twice that of saltcedar seedlings across all density treatments. As density of cottonwood increased, intraspecific competition increased in severity and biomass of cottonwood seedlings decreased. At 4 plants/0.25 m 2 , cottonwood seedlings had the greatest biomass; whereas, survival was highest at 10 plants/ 0.25 m 2 . Our results support greenhouse studies and suggest that if favorable germination conditions are established for cottonwood in floodplains, saltcedar seedlings that cogerminate could be outcompeted by native cottonwood seedlings.

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Section: Methodsmentioning

confidence: 99%

Seedling competition between native cottonwood and exotic saltcedar: implications for restoration

2008

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“…Of these, the competitive ratio is independent of any possible yield advantage of the mixture (Willey and Rao 1980). However, the values of indices may be unstable, being dependent on the experimental design (Inouye and Schaffer 1981, Connolly 1986, HAkansson 1988 (Gibson 1986), herbivores (Whittaker 1979) and the presence or absence of mycorrhiza (Fitter 1977). In a slightly different use of the replacement series, Cottam (1985) showed that the intensity with which herbivores feed on plants may vary according to their proportions in mixtures.…”

Section: Characterization Of Yieldmentioning

confidence: 99%

“…These methods produce equations which depict intra-and intergenotypic competition. They can be based on a model according to which the reciprocal of the yield of an individual plant is linearly related to the stand density (Willey and Heath 1969, Connolly 1986. The advantage of the additive linear reciprocal equation compared to other equations describing competition lies in the biological significance of the regression coefficients in the model (Wright 1981, Spitters 1983.…”

Section: Characterization Of Yieldmentioning

confidence: 99%

“…In addition, the calculated land equivalent ratio value (LER) indicated that the yield advantage would have been marginal. Thus a simple replacement series trial cannot unequivocably demonstrate this to be the case, as the overall density is predetermined and does not necessarily lie at the optimal point of the yield-density function for all the components in pure stand or for the various mixtures (Connolly 1986, HAkansson 1988. This means that even when the relative yield total is greater than unity, one cannot be certain that the mixture was really superior to the monocultures unless maximal yield has been evaluated under the appropriate conditions.…”

Section: Yield Advantagesmentioning

confidence: 99%

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Competition and yield advantage in barley-barley and barley-oats mixtures

Jokinen¹

1991

AFSci

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Competition and yield advantage in barley varietal mixtures and in barley-oats mixtures were investigated. The trials were based on replacement series, but in a few cases the overall density of the stand was varied on the basis of an addition series. Both models of competition, one based on the de Wit model and the other upon a linear regression model, agreed as to which component was the dominant and which was the subordinate in the mixture. The competition coefficients from regression analyses depicted competition between components better in a dense than in a sparse stand. The competitive ability of a genotype did not depend directly upon individual characters of the genotype, such as rate of initial development, earliness, culm height, tillering capacity or grain yield in monoculture (adaptation), A good combination of characters from the viewpoint of competition was provided by the barley cv. Arra with its rapid initial development and rapid culm growth (earliness), the variety being dominant irrespective of number of components in the mixture, stand density, level of nitrogen fertilization or growing season. This suggests that competitive relations and distribution of resources within a mixture are determined at an early stage in the growing period. In other cases the competitive ability of a genotype varied from one environment to another with the competitive relations between components being inconsistent. The dominance of an aggressor usually increased with increasing nitrogen fertilization especially when the total density of the stand was high. As a rule, competition affected all the components of yield with the kernel weight being least affected. The grain yield of varietal mixtures did not differ from the yield of the highest yielding component grown alone, i.e., mixtures did not over yield. The relative yield total of varietal mixtures was higher at low (RYT > 1) than at optimal densities (RYT =1). Also the relative yield total was higher under conditions where the nitrogen fertilization was not optimal. The results of a varietal trial repeated during three successive years indicated that the relative yield total of a given mixture varied from one growing season to another, fluctuating around unity. Thus highly adapted barley varieties appear to compete for the same resources, and the grain yield advantage of such mixtures is marginal. The results of the barley-oats mixture trials revealed that the mixture may over yield. The relative yield totals of barley-oats mixtures were usually equal to or greater than unity the latter suggesting that the mixtures of barley and oats may use resources more efficiently than monocultures, and some grain yield advantage could be achieved with such mixtures. The protein yield of the barley-oats mixtures did not differ from the yield of the highest yielding component grown alone. The ratio of actual and expected protein yield and the relative protein yield total were usually slightly greater than one. The grain yields of mixtures were not consistently more stable than monocultures as determined by the coefficient of variation.

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“…The replacement series design has been criticized for various reasons (Harper 1977;Connolly 1986; Under- (Khan et al1975 Herben and Krahulec 1990;Silvertown and Dale 1991;review in Jolliffe 2000) but has been regarded as a useful design to assess competitive ranks in twospecies interactions (Firbank and Watkinson 1990;Cousens 1991;Cousens and O'Neill 1993). One of the criticisms is a possible dependency of the outcome on the total density used in an experiment (Inouye and Schaffer 1981;Taylor and Aarssen 1989).…”

Section: Discussionmentioning

confidence: 99%

Competitive ranks of three Fucus spp. (Phaeophyta) in laboratory experiments?testing of Keddy's competitive hierarchy model

Karez

2003

Helgoland Marine Research

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Keddy's competitive hierarchy model describes species distribution patterns along gradients under equilibrium conditions and can potentially serve as an explanation for zonation patterns of intertidal seaweeds on rocky shores. One of the assumptions of the model is a competitive hierarchy with the top competitor occupying the benign end of the gradient. Another assumption is the consistency of competitive ranks of species in all environmental conditions included in the shared parts of species' fundamental niches. In laboratory replacement series experiments, the competitive ranks of pairs of Fucus species that occupy adjacent zones in the field were analysed and compared to ranks found in previous field experiments. Unattached thalli of Fucus serratus versus F. vesiculosus or F. vesiculosus versus F. spiralis, respectively, were held in aerated beakers to establish the competitive ranking of the three congeners. Each replacement series was conducted at three total densities. F. vesiculosus was clearly competitively dominant over F. serratus. In competition with F. spiralis, F. vesiculosus was only dominant at its lowest absolute input frequencies, but at higher frequencies dominance was reversed. At high densities, the total ranking was F. spiralis > F. vesiculosus > F. serratus, which is the opposite order to that which would be expected from Keddy's model. Although all three species thrived well under the laboratory conditions, the results did not reflect in situ competitive dominances, which may be an effect of nutrient competition in the laboratory. Keddy's assumption that competitive ranks are consistent over the whole range of fundamental niches cannot be supported for Fucus spp.

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On Difficulties with Replacement-Series Methodology in Mixture Experiments

Cited by 223 publications

References 18 publications

Seedling competition between native cottonwood and exotic saltcedar: implications for restoration

Seedling competition between native cottonwood and exotic saltcedar: implications for restoration

Competition and yield advantage in barley-barley and barley-oats mixtures

Competitive ranks of three Fucus spp. (Phaeophyta) in laboratory experiments?testing of Keddy's competitive hierarchy model

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