scholarly journals The Theory and Application of Plant Competition Models: an Agronomic Perspective

2003 ◽  
Vol 92 (6) ◽  
pp. 741-748 ◽  
Author(s):  
S. E. PARK
Keyword(s):  
Plant Competition ◽  
Competition Models

Partitioning the union of disks in plant competition models

1979 ◽  
Vol 205 (1160) ◽  
pp. 423-423
Keyword(s):  
Explicit Form ◽  
Plant Competition ◽  
Boundary Curve ◽  
Point Of View ◽  
General Point ◽  
Continuity Properties ◽  
Competition Models ◽  
Change Of Scale ◽  
The Common

The problem of partitioning the union of disks, which arises in theories of competition between plants, is analysed from a general point of view. Some simple and natural assumptions such as connectedness, invariance under translation, rotation and change of scale, and monotonicity and continuity properties of the partition sets are imposed. From these it is proved that the partition is specified by giving a boundary curve between two disks with the very explicit form: R α x ─ | r ─ x | α = R α y ─ | r ─ y | α , α ≽ 1, where R x , R y are the radii of the disks, x , y are their centres and r is a point on the boundary. This includes the Johnson-Mehl construction (α = 1), the common chord (α = 2) and the perimeter of the larger disk (α → ∞). Larger disks dominate smaller ones if and only if α > 1, so that η = 1 ─ 1/α, 0 ≼ η < 1, is a natural index measuring the strength of domination.

Research advances in plant competition in agroforestry systems

2009 ◽  
Vol 17 (2) ◽  
pp. 379-386 ◽  
Author(s):  
Rong MAO ◽  
De-Hui ZENG
Keyword(s):  
Plant Competition ◽  
Agroforestry Systems

scholarly journals Pricing and Return Policies in a Competitive Market: A Consumer-Valuation Based Analysis with Valuation Uncertainties

2021 ◽  
Vol 13 (3) ◽  
pp. 1432
Author(s):  
Huifang Jiao ◽  
Xuan Wang ◽  
Chi To Ng ◽  
Lijun Ma
Keyword(s):  
Competitive Market ◽  
Two Dimensional ◽  
Competitive Markets ◽  
Return Policies ◽  
Numerical Investigations ◽  
Return Policy ◽  
Consumer Valuation ◽  
Competition Models ◽  
Monopoly Market ◽  
Duopoly Market

In this study, we develop a series of consumer-valuation-based models to investigate the pricing and return policies of the sellers in a competitive e-commerce market. Differing from the competition models in literature, a novel two-dimensional valuation structure is built, which considers the valuations of a consumer on two products and the valuation differentiation of all consumers on each product. We consider both monopoly and duopoly (competitive) markets. In each market, two models are respectively developed, one with and one without the return policies. We derive the solutions for the four models, and conduct some analytical and numerical investigations. The results show that return policy with a partial refund is always chosen by the sellers in both monopoly and duopoly markets. Return policy benefits the seller in a monopoly market, but may not benefit the sellers in a duopoly market. In the duopoly models, one seller can be considered as a monopoly seller who meets a new competitor. Our results show that the monopoly seller will reduce its price by no more than 20% when there comes a competitor, and, counter-intuitively, it will meanwhile adopt a severer return policy to the consumers.

scholarly journals The Effect of Mycorrhizal Fungi and PGPR on Tree Nutritional Status and Growth in Organic Apple Production

Agronomy ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1402
Author(s):  
Sebastian Przybyłko ◽  
Wojciech Kowalczyk ◽  
Dariusz Wrona
Keyword(s):  
Nutritional Status ◽  
Mycorrhizal Fungi ◽  
Negative Impact ◽  
Nitrogen Nutrition ◽  
Nutrient Use Efficiency ◽  
Plant Competition ◽  
Fruit Production ◽  
Organic Fertilizers ◽  
Nutrition Status ◽  
Tree Roots

The desire to reduce the negative impact of crops on the environment, as well as the growing concern for consumer health, is increasing interest in organic fruit production. In this context, the development of new environmentally friendly agrotechnical methods which allows for reducing the use of organic fertilizers by improving the nutrient use efficiency and consequently decreasing the leaching of them is a task of a great importance. The main purpose of this study was to evaluate the effect of mycorrhizal arbuscular fungi (AMF) combined with plant-growth-promoting rhizobacteria (PGPR) on growth and nutritional status of apple trees cultivated on a silty-loam, rich in clay minerals and humus soil under organic farming conditions. Thus, a trial was established in an experimental orchard in Wilanów in Central Poland with three cultivars (‘Topaz’, ‘Odra’, and ‘Chopin’) and a promising clone, U 8869. Trees were or were not inoculated with AMF + PGPR within a split-block experimental design with four replicates. According to the results, mycorrhizal frequency obtained in the inoculated tree roots was on average two-fold higher than in the roots of the control plants. After four years of AMF + PGPR inoculation, 24% higher trunk cross-section area (TCSA) was observed, with the nitrogen and magnesium concentrations in leaves increasing, on average, by 7.8% and 64.2%, and phosphorus and potassium content decreasing by 37.2% and 46.5%, respectively. This study shows that using AMF + PGPR inoculum supports tree roots colonization by AMF. As a result, better nitrogen nutrition status is observed that promote vigorous growth of trees and more efficient uptake of magnesium from the bulk soil. On the other hand, lower phosphorus content in inoculated tree leaves might be explained by a dilution effect, and potassium decrease could occur as a result of fungus–plant competition in conditions of this element deficiency in soil.

scholarly journals Competition Effects and Productivity in Oat–Forage Legume Relay Intercropping Systems under Organic Farming Conditions

Agriculture ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 99
Author(s):  
Viktorija Gecaitė ◽  
Aušra Arlauskienė ◽  
Jurgita Cesevičienė
Keyword(s):  
Grain Yield ◽  
Organic Farming ◽  
Field Experiments ◽  
Plant Competition ◽  
Nutrient Content ◽  
Forage Legume ◽  
Forage Legumes ◽  
Medicago Lupulina ◽  
Competition Effects ◽  
Productivity Indicators

Cereal-legume intercropping is important in many low-input agricultural systems. Interactions between combinations of different plant species vary widely. Field experiments were conducted to determine yield formation regularities and plant competition effects of oat (Avena sativa L.)–black medick (Medicago lupulina L.), oat–white clover (Trifolium repens L.), and oat–Egyptian clover (T. alexandrinum L.) under organic farming conditions. Oats and forage legumes were grown in mono- and intercrops. Aboveground dry matter (DM) measured at flowering, development of fruit and ripened grain, productivity indicators, oat grain yield and nutrient content were established. The results showed that oats dominated in the intercropping systems. Oat competitive performance (CPo), which is characterized by forage legumes aboveground mass reduction compared to monocrops, were 91.4–98.9. As the oats ripened, its competitiveness tendency to declined. In oat–forage legume intercropping systems, the mass of weeds was significantly lower compared to the legume monocrops. Oats and forage legumes competed for P, but N and K accumulation in biomass was not significantly affected. We concluded that, in relay intercrop, under favourable conditions, the forage legumes easily adapted to the growth rhythm and intensity of oats and does not adverse effect on their grain yield.

Simultaneous Zip Bifurcation and Limit Cycles in Three Dimensional Competition Models

2006 ◽  
Vol 5 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Eduardo Sáez ◽  
Eduardo Stange ◽  
Iván Szántó
Keyword(s):  
Limit Cycles ◽  
Three Dimensional ◽  
Competition Models
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