Cheatgrass invasion “engineers” the soil to facilitate its growth

Authors: Blank, Robert - Bob; Morgan, Tye

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/4/2011
Publication Date: 1/28/2012
Citation: Blank, R.R., Morgan, T.A. 2012. Cheatgrass invasion “engineers” the soil to facilitate its growth [abstract]. Society for Range Management. 65:0162.

Interpretive Summary:

Technical Abstract: We tested the hypothesis that, over-time, cheatgrass occupation of a site, “engineers” the soil such that it is more favorable to its own growth. Testing was done in a greenhouse using rhizotrons (30 x 6 x 100 cm). Eight replicates each were filled with either freshly-collected soil occupied by winterfat (A horizon) or a similar winterfat soil (A horizon) invaded by cheatgrass for 10 years. Six replicates of each soil were sown to cheatgrass and 2 replicates were unplanted controls. The experiment was conducted over two growth cycles of 70 days each with water not limited. After each growth cycle, cheatgrass was harvested at soil level, dried, weighed, and analyzed for nutrients. Removable rhizotron backings allowed root and soil sampling. Three replicate cores (5.5 cm diameter) were extracted at the edges and center at 10, 40, and 80 cm. Roots were separated from each core by sieving, dried, and weighed. The remaining soil was analyzed for nutrients. After the 1st growth cycle, above-ground cheatgrass biomass grown in the invaded soil was over 3 times greater than cheatgrass grown in the non-invaded soil, and over 2 times greater after the 2nd growth cycle. Root biomass was significantly greater for cheatgrass grown in the invaded soil, but only at the 10 cm depth. For both growth cycles, cheatgrass tissue from the invaded soil had significantly greater N concentration. After the 1st growth cycle, cheatgrass tissue grown in the invaded soil had significantly less tissue P, Mn, and Cu than cheatgrass grown in the non-invaded soil. Overall, the invaded soil had greater mineral N, which may explain superior growth of cheatgrass. The invaded soil also had far higher availability of P and Mn than the non-invaded soil, which contradicts their smaller presence in plant tissue. These data support the hypothesis, that conditioning a soil with cheatgrass, over-time, enhances its nutrient availability and growth potential.