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Competition Treatments (competition + treatment)
Selected AbstractsSimulated effects of herb competition on planted Quercus faginea seedlings in Mediterranean abandoned croplandAPPLIED VEGETATION SCIENCE, Issue 2 2003Benayas Rey Abstract. We tested simulated effects of herb competition on the performance of planted seedlings of Quercus faginea ssp. faginea in Mediterranean abandoned cropland. We produced three types of environment with respect to herb competition: absence of competition (AC), below-ground competition (BGC), and total competition (TC). We assessed the performance of Q. faginea seedlings in each treatment in five ways: (1) seedling mortality, (2) leaf length and total plant leaf area, (3) water potential, (4) total biomass and biomass allocation, and (5) non-structural carbohydrate storage in different plant organs. We also measured (6) soil moisture at different depths and (7) biomass production of herbs. The TC treatment reduced water availability more than the BGC treatment, in agreement with the most pronounced water stress in seedlings under TC conditions. BGC and TC treatments showed a high and similar seedling mortality, which was one order of magnitude higher than that in the AC treatment. Competition treatments affected glucose concentration in both shoots and roots, and followed the rank TC > BGC > AC. Q. faginea seedlings might compensate a lower water availability through glucose accumulation in leaves to reduce the osmotic potential. There was a maximum starch concentration in the BGC treatment that hints that a moderate resource limitation would limit tissue growth but not carbon assimilation. We conclude that the negative effects of herbs on Q. faginea seedlings are mostly a result of competition for water, and that this competition is noticeable since the earliest stages of the establishment. Complete weed removal is a technique that would strongly improve seedling survivorship. [source] Effects of Plant Population Density and Intercropping with Soybean on the Fractal Dimension of Corn Plant Skeletal ImagesJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2000K. Foroutan-pour Three-year field experiments were conducted to determine whether the temporal pattern of fractal dimension (FD) for corn (Zea mays L.) plant structure is altered by plant population density (PPD) or intercropping with soybean [Glycine max. (L.) Merr.], and how changes in the FD are related to changes in other canopy characteristics. Plants in monocropped corn and intercropped corn,soybean plots were randomly sampled and labelled for later identification. Corn plant structure was photographed from the side that allowed the maximum appearance of details (perpendicular to the plane of developed leaves) and from two fixed sides (side 1: parallel to the row and side 2: perpendicular to the row). Images were scanned and skeletonized, as skeletal images provide acceptable information to estimate the FD of plant structure two-dimensionally by the box-counting method. Differences in the FD estimated from images taken perpendicular to the plane of developed leaves were not significant among competition treatments. An adjustment of corn plants to treatments, by changing the orientation of the plane of developed leaves with respect to the row, was observed. Based on overall FD means, competition treatments were ranked as: high > normal , intercrop , low for side 1 and intercrop > low , normal > high for side 2. Leaf area index (LAI) and plant height had a positive correlation with FD. In contrast, light penetration had a negative correlation with FD. In conclusion, FD provides a meaningful and effective tool for quantifying corn plant structure, measuring the structural response to cultural practices, and modelling corn plant canopies. Zusammenfassung Folgende Ziele der Untersuchungen wurden berücksichtigt: 1) Eine geeignete Methode für die Abschätzung der Anteile (FD) 2-dimensional für Pflanzen mit einer einfachen dreidimensionalen Vegetationsstruktur wie z. B. Mais (Zea mays L.) zu bestimmen; 2) der Frage nachzugehen, ob die zeitlichen Muster von FD bei der Maispflanzenstruktur durch die Bestandesdichte verändert wird (PPD: low, normal und hoch) oder in Mischanbau mit Sojabohnen (Glyzine max. L.) Merr.); und 3) in welcher Beziehung Änderungen in der FD in der Maispflanzenstruktur zu Änderungen in anderen Bestandeseigenschaften stehen. Pflanzen im Reinanbau von Mais und im Mischanbau in Mais-Sojabohnen-Parzellen wurden randomisiert gesammelt und für die spätere Identifikation gekennzeichnet. Die Maispflanzenstruktur wurde von der Seite fotografiert, so dai eine maximale Darstellung der Details (perpendiculär zu der Ebene der entwickelten Blätter) und von zwei festgelegten Seiten (Seite 1: parallel zur Reihe und Seite 2 perpendikulär zur Reihe) verfügbar war. Die Abbildungen wurden gescannt und skelettiert; Skelettabbildungen geben eine akzeptierbare Information zur Abschätzung von FD Pflanzenstrukturen in zweidimensionaler Form über die Box-counting-Methode. Unterschiede in der FD, die sich aus Bildern mit einer perpendikulären Aufnahme zu der Ebene der entwickelten Blätter ergaben, waren nicht signifikant innerhalb der Konkurrenzbehandlungen. Eine Anpassung der Maispflanzen an die Behandlungen durch Änderungen der Orientierung zur Ebene der entwickelten Blätter im Hinblick auf die Reihe, wurde beobachtet. Auf der Grundlage von gesamt FD-Mittelwerten ergab sich, dai Konkurrenzbehandlungen in folgender Reihe auftraten: Hoch (1,192) > (1,178) , zu Mischanbau (1,177) , zu gering (1,170) für Seite 1 und bei Mischanbau (1,147) > gering (1,158) , (1,153) > hoch für Seite 2. Der Blattflächenindex (LAI) und die Pflanzenhöhe hatten eine positive Korrelation zu FD. Im Gegensatz dazu wies die Lichtpenetration eine negative Korrelation zu FD auf. Es kann festgestellt werden, dai FD eine aussagekräftige und zweckmäiige Methode ist, die Maispflanzenstruktur zu quantifizieren, Strukturreaktionen zum Anbauverfahren zu messen und Maispflanzenbestände zu beschreiben. [source] Differential genetic influences on competitive effect and response in Arabidopsis thalianaJOURNAL OF ECOLOGY, Issue 5 2005JAMES F. CAHILL JR Summary 1Competition plays an important role in structuring populations and communities, but our understanding of the genetic basis of competitive ability is poor. This is further complicated by the fact that plants can express both competitive effect (target plant influence upon neighbour growth) and competitive response (target plant growth as a function of a neighbour) abilities, with these ecological characteristics potentially being independent. 2Using the model plant species Arabidopsis thaliana, we investigated patterns of intraspecific variation in competitive effect and response abilities and their relationships to other plant traits and resource supply rates. 3Both competitive effect and response were measured for 11 genotypes, including the Columbia ecotype and 10 derived mutant genotypes. Plants were grown alone, with intragenotypic competition, and with intergenotypic competition in a replicated blocked design with high nutrient and low nutrient soil nutrient treatments. We quantified competitive effect and response on absolute and per-gram bases. 4Competitive effect and response varied among genotypes, with the relative competitive abilities of genotypes consistent across fertilization treatments. Overall, high rates of fertilization increased competitive effect and competitive response abilities of all genotypes. Both competitive effect and response were correlated with neighbour biomass, though genotype-specific traits also influenced competitive response. 5At the genotype level, there was no correlation between competitive effect and response in either fertilization treatment. Overall patterns in competitive response appeared consistent among inter- and intragenotypic competition treatments, indicating that a target genotype's response to competition was not driven by the genetic identity of the competitor. 6These findings indicate that within A. thaliana, there is the potential for differential selection on competitive effect and response abilities, and that such selection may influence different sets of plant traits. The concept of a single competitive ability for a given plant is not supported by these data, and we suggest continued recognition of these dual competitive abilities is essential to understanding the potential role of competition in influencing intra- and interspecific processes. [source] Effects of resource competition and herbivory on plant performance along a natural productivity gradientJOURNAL OF ECOLOGY, Issue 2 2000René Van Der Wal Summary 1,The effects of resource competition and herbivory on a target species, Triglochin maritima, were studied along a productivity gradient of vegetation biomass in a temperate salt marsh. 2,Transplants were used to measure the impact of grazing, competition and soil fertility over two growing seasons. Three parts of the marsh were selected to represent different successional stages; Triglochin reached local dominance at intermediate biomass of salt-marsh vegetation. At each stage, three competition treatments (full plant competition, root competition only, and no competition) and three grazing treatments (full grazing, no grazing on Triglochin, and no grazing on Triglochin or neighbours) were applied to both seedlings and mature plants. 3,Competition and herbivory reduced biomass and flowering of Triglochin. The impact of grazing was strongest at the stage with the lowest biomass, while both herbivory and competition had a significant impact at the stage with the highest biomass. When plants were protected from direct herbivory, competition operated at all three successional stages. 4,Grazing reduced light competition when vegetation biomass was low or intermediate, but at high biomass there was competition for light even when grazing occurred. Herbivore exclusion increased the effects of plant competition. Except at low biomass, the negative impact of plant competition on Triglochin performance was greater than the positive effect of not being grazed. 5,Grazing played a minor role in seedling survival and establishment which were largely controlled by competitive and facilitative effects. 6,Once established, the persistence of Triglochin will be determined largely by grazing. Intense grazing in the younger marsh and increasing competition for light in the older marsh will restrict the distribution to sites with intermediate biomass. [source] | ||||||||||