|MANGLA, SEEMA - Oregon State University|
|RADOSEVICH, STEVEN - Oregon State University|
Submitted to: Plant Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2010
Publication Date: 4/1/2011
Citation: Mangla, S., Sheley, R.L., James, J.J., Radosevich, S.R. 2011. Intra and interspecific competition among invasive and native species during early stages of plant growth. Plant Ecology. 212:531-542.
Interpretive Summary: Most single harvest studies show competition from annual grasses is a major barrier to restoration. Developing new restoration techniques require understanding the degree to which competition among and between species control invasive and native plant growth, especially early in the establishment phase. We determined that the intensity of competition among and between species changes during early stages of plant growth between two invasive (cheatgrass, medusahead) and two natives (bluebunch wheatgrass, Sandberg’s bluegrass) periodically during the establishment phase. Since competition among desired species limit their own establishment at times, opportunities for improving restoration exist from determining the optimum combination of density, species proportion, and their spatial arrangement in various ecosystems and environments.
Technical Abstract: Plant competition is considered to be the primary ecological process limiting the success of grassland restoration. Appropriate restoration techniques require an understanding of the degree to which intra and/or interspecific competition controls native plant growth. The objective of this study was to determine how the intensity of intra and interspecific competition changes during early stages of plant growth. Two invasive (Bromus tectorum and Taeniatherum caput-medusae) and two native (Pseudoroegneria spicata and Poa secunda) species were grown in a diallel competition experiment, either alone or in 1:1 binary combinations and exposed to two levels of N (no N or 400 mg N.Kg-1 soil added) in a greenhouse. Total biomass for each species was quantified over four harvests and competitive effects were calculated for every harvest. Our results suggest that invasive and native species are subject to both intra and interspecific competition; however, the type differed among harvests. Intraspecific competition was intense for native species at the initial harvests and therefore important in contributing to the outcome of final size of native species seedlings. Interestingly, bluebunch wheatgrass imposed interspecific competition on annual grasses at the first two harvests and appeared to be a better competitor than Sandberg’s bluegrass. We found that fast growing invasive species became more competitive compared to slow growing native species with increasing N and appear to establish a positive feedback mechanism between size and resource uptake. Opportunities to improve restoration success exist from determining the optimum combination of density, species proportion, and their spatial arrangement in various ecosystems and environments.