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Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/26/2007 Publication Date: 4/15/2008 Citation: Blank, R.R. 2008. Biogeochemistry of plant invasion: a case study with bromus tectorum l. Journal of Invasive Plant Science and Management. 1:226-238. Interpretive Summary: Limited data exists on the non-native cheatgrass (Bromus tectorum) invasion on biogeochemical cycling. Biogeochemical cycling was quantified along a cheatgrass invasion transect occurring in a native semi-shrub winterfat community in the Honey Lake Valley of northeastern CA, USA. Aboveground biomass g m-2 was significantly greater, with cheatgrass averaging over 90% of the plant mass, on plots invaded for 10 years (280 g) compared to the non-invaded plots (148 g). Compared to the non-invaded plots, vegetation fluxes (g m-2 yr-2) of C were significantly greater and fluxes of Ca, Fe, and Cu were significantly less on plots invaded for 10 years. Soils occupied for 10 years by cheatgrass have significantly greater total N and organic C, and greater availability of Fe, Mn, Cu, ortho-P, Ca, and K compared to non-invaded soil. The data suggest that invasion by cheatgrass facilitates elevated nutrient availability and fosters differential plant nutrient cycling relative to a native non-invaded community. Long-term occupation of environments by cheatgrass may affect the vertical distribution of nutrients, which in concert with other aspects of global change could alter soil evolution and plant successional patterns. Technical Abstract: The exotic invasive annual grass Bromus tectorum L. (cheatgrass) is problematic in the intermountain region of the western United States, often replacing native shrub/perennial grass communities with near monocultures. Limited data exists on the affect of B. tectorum invasion on biogeochemical cycling. Biogeochemical cycling was quantified along a B. tectorum invasion transect occurring in a native semi-shrub Krascheninnikovia lanata (Pursh) A.D.J. Meeuse & Smit (winterfat) community in the Honey Lake Valley of northeastern CA, USA. Five random 1m2 plots were laid out in three B. tectorum invasion classes: non-invaded (NI), invaded for 3 years (I3), and invaded for about 10 years (I10). On each plot, all aboveground vegetation was harvested and separated by species, dried, weighed, and tissue nutrients quantified. In addition, soil samples were collected from 0-30, 30-60, and 60-100 cm depths and various nutrient pools quantified. Aboveground biomass g m-2 was significantly greater, with B. tectorum averaging over 90% of the plant mass, on the I10 plots (280 g) compared to the NI plots (148 g). Compared to the NI plots, vegetation fluxes (g m-2 yr-2) of C were significantly greater and fluxes of Ca, Fe, and Cu were significantly less on I10 plots. Soils occupied for 10 years by B. tectorum have significantly greater total N and organic C, and greater availability of Fe, Mn, Cu, ortho-P, Ca, and K compared to NI soil. For the I10 plots, available soil N (dominantly NO3-) was greatest in the 60-100 cm depth increment, whereas for the other plots, N availability was greatest in the 0-30 cm depth increment. Net N soil mineralization potential was near 0 on the I10 plots at all depth increments. These data suggest that invasion by B. tectorum facilitates elevated nutrient availability, possibly increases system leakiness of N, and fosters differential plant nutrient cycling relative to a native non-invaded community. Elevated nutrient availability promulgated by B. tectorum invasion may increase its competitive stature. Moreover, competition from B. tectorum results in loss of critical native flora, which may impact the quantity and quality of forage for native wildlife. Long-term occupation of environments by B. tectorum, may affect the vertical distribution of nutrients, which in concert with other aspects of global change could alter soil evolution and plant successional patterns. |
