Author
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Espeland, Erin |
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Submitted to: Prairie Naturalist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/5/2015 Publication Date: 6/10/2015 Citation: Espeland, E.K. 2015. Inter- and intra-specific interactions in germination and seedling establishment of cheatgrass and Russian wildrye. Prairie Naturalist. 47(1):4-12. Interpretive Summary: Cheatgrass growth has been shown to be affected by soil type and soil borne pathogens. In this experiment, I test if competitive relationships between cheatgrass and Russian wild rye are different in three soil types. Soils were collected from 1) a cheatgrass population, 2) a wild rye population 12 meters away with no cheatgrass present (PJ), and 3) the intermediately-located expanding edge of the wild rye population into the cheatgrass population (PX). Neither species affected the other’s growth on any soil type (no interspecific competition). Within-speices competition was observed and plant size was reduced by neighbors of the same species. The presence of wild rye seeds in the wild rye-conditioned soil (type 2 above) strongly inhibited cheatgrass emergence. Similarly, the presence of wild rye seeds in the cheatgrass soil (type 1 above) stimulated cheatgrass emergence. Wild rye emergence fraction was less as more wild rye seeds were present in all soil types but this intraspecific compeittion was not observed in a laboratory germination experiment in a soil-free environment. Russian wild rye is able to establish within cheatgrass populations because it is not affected by cheatgrass competition when water is not limiting. It is likely that seed-borne biota (i.e. bacteria or fungi) from wild rye seeds interact with free-living soil biota to inhibit cheatgrass emergence in wild rye-conditioned soils. Understanding this biotic interaction will allow us to discover native plant materials that prevent cheatgrass population expansion and also allow us to develop biocontrol for cheatgrass. Technical Abstract: Cheatgrass (Bromus tectorum L.) growth has been shown to be affected by soil type and soil borne pathogens. In this experiment, I test if competitive relationships between B. tectorum and Russian wild rye (Psathryrostachys juncea (Fisch.) Nevski) are different in three soil types. Soils were collected from 1) a B. tectorum population (BT), 2) a P. juncea population 12 meters away with no B. tectorum present (PJ), and 3) the intermediately-located expanding edge of the P. juncea population into the B. tectorum population (PX). Intraspecific competition was observed for both species and neither species affected the other’s growth on any soil type (no interspecific competition). The presence of P. juncea seeds in the PJ soil strongly inhibited B. tectorum emergence. Similarly, the presence of P. juncea seeds in the BT soil stimulated B. tectorum emergence. Intraspecific inhibition of emergence of P. juncea was observed in all soil types but not in a laboratory germination experiment. Psathryrostachys juncea is able to establish within B. tectorum populations because it is not affected by B. tectorum competition when water is not limiting. It is likely that seed-borne biota in P. juncea interact with soil biota to inhibit B. tectorum emergence in P. juncea-conditioned soils. Understanding this biotic interaction will allow us to discover native plant materials that prevent B. tectorum population expansion and also allow us to develop biocontrol for B. tectorum. |
