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Title: ECOLOGICAL SYNDROMES OF INVASION IN SEMIARID RANGELANDS AND THEIR IMPLICATIONS FOR LAND MANAGEMENT AND RESTORATION

Author
item GERMINO, MATTHEW - IDAHO STATE UNIVERSITY
item Seefeldt, Steven
item HILL, JUDSON - IDAHO STATE UNIVERSITY
item WEBER, KEITH - IDAHO STATE UNIVERSITY

Submitted to: Society for Ecological Restoration Abstracts
Publication Type: Proceedings
Publication Acceptance Date: 7/20/2004
Publication Date: 7/26/2004
Citation: Germino, M.J., Seefeldt, S.S., Hill, J., Weber, K.T. 2004. Ecological syndromes of invasion in Semiarid rangelands and their implications for land management and restoration. In: Proceedings of the Society for Ecological Restoration. 16th International Conference for Ecological Restoration, August 24-26, 2004, Victoria, Canada. 2004 CDROM.

Interpretive Summary: Exotic plant invasions are occurring throughout the rangelands of western North America. A better understanding of why they occur would help land managers target causes and not just symptoms of invasion. The objective of the research was to determine whether fire would increase resources for plants in a way that would favor exotic plant species over established native flora. Changes in soil water availability were measured. There was increased soil water available for plants 0.4 m below the soil surface in burned compared to unburned areas. Carbon uptake was 50% greater in spotted knapweed (an exotic plant) compared to native grasses due to greater water uptake from deep soils. Removal of sagebrush will reduce competition for deeper soil water and give deep rooted perennial exotic plants a competitive advantage in infested rangelands. Managing rangeland plant communities to utilize available soil water may be an important way to reduce infestations of exotic plants.

Technical Abstract: An understanding of why infestations occur helps land managers target causes and not just symptoms of invasions. Syndromes, which are recurring sets of symptoms that are characteristic of a particular disorder or disease, help link basic and generalizable science with the specific treatment needs of individuals in clinical practice, or sites in land management. We hypothesized that management-related disturbances increase site resources in ways that selectively favor ecophysiological traits of invasive compared to established flora. In rangelands of Montana and Idaho, we measured 1) the effects of prescribed fire and shrub removal on plant community composition and soil water availability, and 2) differences in photosynthesis and water relations in Centaurea maculosa (spotted knapweed; CEMA) and established flora (mainly grasses). Soil water increased substantially below about 0.4 m depth in disturbed compared to control plots. Carbon uptake was about 50% greater in CEMA than the grasses, due apparently to greater water uptake from deep soils and correspondingly greater water status in CEMA. These results point to a possible ecological syndrome that may be applicable in some form to vast areas of sagebrush-steppe that 1) are disturbed in ways that 2) cause unusually low abundances of native, deep-rooted perennials, and 3) as a consequence, have unusually abundant deep soil water, and 4) are therefore more easily invaded by CEMA and similar exotic perennial forbs. If correct, this syndrome suggests that managing semiarid communities for complete utilization of soil water may be an important way that rangeland managers can avoid infestations by exotic perennial forbs.