Competition intensity and its importance: results of field experiments with Anthoxanthum odoratum

Sammul, Marek; Kull, Kalevi; Oksanen, Lauri; Veromann, Peeter

doi:10.1007/pl00008887

Cited by 66 publications

(76 citation statements)

References 46 publications

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“…Our results support the view of Mulder et al (2004) that minor species may have little ability to increase productivity in the absence of common species and of Smith and Knapp (2003) that dominant species can maintain a high biomass production in the absence of rare and uncommon species. These opposing impacts of neighbor removal on dominant versus minor species may explain why responses to neighbor removal are not consistent, ranging from positive (Sammul et al 2000;Gerdol et al 2002), to neutral (BretHarte et al 2004Totland et al 2004), to negative (Shevtsova et al 1997;Aksenova et al 1998). In general, our results support our Wrst two hypotheses: removing species has much greater impacts than removing an equivalent amount of biomass, and dominant species are more able to respond to this treatment than minor species.…”

Section: Biomass Changes Following Removal Treatments: Dominant Versusupporting

confidence: 85%

Species removal and experimental warming in a subarctic tundra plant community

Rixen

Mulder

2009

Oecologia

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Neighbor interactions are likely to play an important role in subarctic plant communities. We conducted experiments in Interior Alaska in which we crossed species removal with greenhouse warming manipulations. We examined changes in community biomass, and in plant survival and growth of individual species in response to experimental warming and to: (1) removal of whole species versus an equivalent amount of biomass across many species, and (2) removal of subdominant (locally common) versus minor (locally uncommon) plants. Community biomass indicated compensation in growth after removal of minor species and after biomass removal without elimination of entire species, but under-compensation after removal of subdominants. Growth and survival of individual species showed facilitation between some species. Warming increased growth of dominant vascular plants, but at the same time reduced survival, and these impacts were greater for larger, more mesic species than for the smaller species associated with drier habitats. Growth of mosses was reduced by the warming. Removal effects did not differ between warming and ambient conditions. The results indicate that common species are able to reduce resources for others (competitive effect) and increase their growth after neighbor removal, whereas locally uncommon species are not able to respond rapidly to increased resources made available by neighbor removal. Therefore, the impact of the presence of common species on locally uncommon species was facilitative overall, but not vice versa. The balance between disturbances such as changes in temperature and species losses from the community will likely be crucial in determining shifts in subsequent community composition.

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Section: Biomass Changes Following Removal Treatments: Dominant Versusupporting

confidence: 85%

Species removal and experimental warming in a subarctic tundra plant community

Rixen

Mulder

2009

Oecologia

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“…All plants were allowed to grow for 75 days before harvest. Because the roots of C. lasiocarpa and D. angustifolia in the mixtures were closely intertwined, only the aboveground portions were harvested in the mixture as described previously (Fowler 1982;Sammul et al 2000;Garcia-Serrano et al 2007). After harvest, plants in the monoculture were divided into aboveground and belowground portions while aboveground portions in the mixture were divided into C. lasiocarpa and D. angustifolia.…”

Section: Plant Materials and Experimental Designmentioning

confidence: 99%

Effects of hydrology and competition on plant growth in a freshwater marsh of northeast China

Zhang

Mao

Gong

et al. 2013

Journal of Freshwater Ecology

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Hydrology and competition are major determinants of plant zonation patterns in wetlands. We conducted a pot experiment to investigate effects of water levels on plant growth of two dominant species from the Sanjiang Plain (Deyeuxia angustifolia and Carex lasiocarpa) in monoculture and mixtures (i.e., 2:1, 1:1, and 1:2 mixtures of C. lasiocarpa and D. angustifolia). Water level had significant effects on the biomass of both species (p < 0.05). The aboveground biomass of C. lasiocarpa increased with decreasing water level in both monoculture and mixtures and the same was true for belowground biomass in monoculture. Waterlogging (10 cm water level) and natural drought reduced the aboveground and belowground biomass of D. angustifolia in monoculture and waterlogging (20 and 10 cm water levels) also reduced the aboveground biomass in mixtures. The relative yield of C. lasiocarpa was greater than 1.0 in the 1:1 mixture (t ¼ 3.49) and the 1:2 mixture (t ¼ 6.63) at 20 cm water level (i.e., the performance of individuals was better in mixtures than that in the monoculture), and the same was true for D. angustifolia in the 2:1 mixture (t ¼ 10.23) and the 1:1 mixture (t ¼ 4.12) at À10 cm water level. The relative yield of C. lasiocarpa increased with increasing water level in the 1:1 and 1:2 mixtures but decreased for D. angustifolia in the 2:1 mixture. Moreover, the species with smaller initial proportion usually had higher relative yield in mixtures. This would tend to promote the coexistence of these two species. Our results suggest that hydrologic regime change has the potential to produce marked influences on plant productivity and ecosystem carbon budget in the Sanjiang Plain. Moreover, competition is an additional important determinant of plant distribution and community structure in this area.

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“…In a comparison of three plant species C imp decreased with fertility but it was suggested that competitive importance was dependent on the ability of the species to tolerate low resource availability (Gaucherand et al 2006). Sammul et al (2000), using a different calculation of competitive importance, reported a correlation between both C int and C imp when competition was calculated using the number of shoots rather than biomass, and Welden et al (1988) detected no relationship between importance or intensity and a water stress gradient for desert shrubs. We observed a reduction in competitive importance due to clipping under the high resource conditions for F. campestris, which further supports arguments that competition in CSR theory is best measured with this index because the measure of competition declines when additional processes are in place.…”

Section: Competitive Intensity and Competitive Importancementioning

confidence: 99%

Using three pairs of competitive indices to test for changes in plant competition under different resource and disturbance levels

Carlyle¹,

Fraser²,

Turkington³

2010

Journal of Vegetation Science

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Questions: How do different resource and disturbance levels interact to affect competition? How do different indices of competition change the interpretation of how competition changes under different resource and disturbance conditions? Location: Greenhouse, Thompson Rivers University, Kamloops, British Columbia, Canada. Methods: Three pairs of indices that have been used to differentiate the predictions of Grime (CSR) and Tilman's (R Ã ) theories were used to assess competition on two species of temperate bunchgrass, (Pseudorogeneria spicata and Festuca campestris) grown in a greenhouse on stress and disturbance gradients. Stress was created by manipulating the amount of water (high, low) and concentration of nutrient solution (high, low) added to pots, while disturbance was created by clipping (clipped, unclipped) in a fully factorial design. Plants were grown individually or with a single neighbour. The three pairs of indices were: (1) absolute and relative competition; (2) competitive effect and response; and, (3) competitive importance and intensity. Results: Absolute competition and competitive importance were the only indices responsive to the resource gradient, which supports CSR theory, and also the only ones to record an effect of disturbance on the strength of competition -under high resource conditions. The other indices showed few responses along the gradients, which supports R Ã theory. Measures of competitive effect and response did not differentiate the two theories. Conclusion: We show that some indices of competition show a decline with increased stress and disturbance, while other indices do not. Therefore, it is necessary to choose a competition index appropriate to the question being asked. Competitive importance and absolute competition were responsive to changes in stress and disturbance, while the other indices were not.Keywords: Absolute and relative competition; Clipping; Competitive effect and response; CSR strategy theory; Drought; Festuca campestris; Importance and intensity of competition; Nutrient availability; Pseudoroegneria spicata; R Ã theory. Nomenclature: Douglas et al. (1994).Abbreviations: C ab 5 absolute competition; C int 5 competitive intensity; C imp 5 competitive importance; C e 5 competitive effect; C r 5 competitive response.

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Competition intensity and its importance: results of field experiments with Anthoxanthum odoratum

Cited by 66 publications

References 46 publications

Species removal and experimental warming in a subarctic tundra plant community

Species removal and experimental warming in a subarctic tundra plant community

Effects of hydrology and competition on plant growth in a freshwater marsh of northeast China

Using three pairs of competitive indices to test for changes in plant competition under different resource and disturbance levels

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