Plant-Soil Relationships ofBromus tectorumL.: Interactions among Labile Carbon Additions, Soil Invasion Status, and Fertilizer

Robert R Blank,James A Young

doi:10.1155/2009/929120

Abstract

Invasion of western North America by the annual exotic grassBromus tectorumL. (cheatgrass) has been an ecological disaster. High soil bioavailability of nitrogen is a contributing factor in the invasive potential ofB. tectorum. Application of labile carbon sources to the soil can immobilize soil nitrogen and favor native species. We studied the interaction of labile carbon addition (sucrose), with soil invasion status and fertilizer addition on the growth ofB. tectorum. Soils were noninvaded (BNI) andB. tectoruminvaded (BI). Treatments were control, sucrose, combined fertilizer, and sucrose + fertilizer. The greenhouse experiment continued for 3 growth-cycles. After the 1st growth-cycle, sucrose addition reducedB. tectorumaboveground mass almost 70 times for the BI soil but did not significantly reduce growth in the BNI soil.B. tectorumaboveground mass, after the 1st growth-cycle, was over 27 times greater for BI control soils than BNI control soils. Although sucrose addition reduced soil-solution , tissue N was not significantly lowered, suggesting that reduction of soil available N may not be solely responsible for reduction inB. tectorumgrowth. Noninvaded soil inhibits growth ofB. tectorum. Understanding this mechanism may lead to viable control strategies.

Highlights

Soil nutrient availability is a principal determinant in structuring plant communities [1,2,3] and if excessive, it can facilitate invasion by weedy plant species [4, 5]
Soil occupied by B. tectorum (BI) for at least 4 years was grossly similar in properties to soil not yet invaded (BNI) (Table 1)
In the 1st growth cycle following sucrose addition to a soil previously invaded by B. tectorum (BI), aboveground mass of B. tectorum was reduced, an astonishing 98 percent relative to the control soil

Summary

Introduction

Soil nutrient availability is a principal determinant in structuring plant communities [1,2,3] and if excessive, it can facilitate invasion by weedy plant species [4, 5]. The underlying mechanism for this restoration strategy is that sucrose stimulates the proliferation of soil microorganisms, which uptake and immobilize soil inorganic N resources away from plants [12, 16] In this lowered available soil N regime, plants with greater N use efficiency, such as native perennials, have an establishment window without undue competition from fast growing annuals [11, 17, 18]. Invasion by B. tectorum disrupts food-webs, alters soil N dynamics, lowers species diversity, and decreases fungi populations [29, 30] It is reasonable, to suspect that a particular soil invaded by B. tectorum for a period of time might respond differently to treatments such as addition of labile C and fertilizer than that same soil not invaded by B. tectorum. (2) Growth of B. tectorum will be alike in soils invaded by B. tectorum for several years relative to a similar soil not yet invaded

Materials and Methods

Results

Discussion