Effects of CO2enrichment on plant-soil relationships of Lepidium latifolium

Abstract

The exotic crucifer Lepidium latifolium L. (perennial pepperweed) is invading wetland and riparian habitats throughout the western United States. Based on previous field studies, our working hypothesis proposed that L. latifolium elevates soil nutrient acquisition ability in response to CO2 enrichment. Replicates of L. latifolium were grown in a high fertility and low fertility soil (along with unplanted controls) in a glasshouse at ambient and elevated CO2 concentrations (360 and 699 µmol mol −1 , respectively). Plants were harvested after 81 days and numerous plant and soil attributes measured. Above-ground plant mass was influenced by a significant CO2 treatment × soil interaction ( P 20% and increased, though not significant, tissue C:N ratio by 38% in high fertility soil and by 51% in low fertility soil. For most soil attributes measured, there was a main effect or interaction with soil fertility level. Soil attributes differed between soil fertility levels and, with the exception of SO 2− 4 , were not influenced by the presence of L. latifolium. Soil attributes increased by CO2 enrichment included acetate extractable Mg 2+ (high fertility soil only), net 30 day N mineralization potential (unplanted control soils only), available N (high fertility soil), bicarbonate extractable P, soil-solution SO 2− 4 (L. latifolium planted pots only), and soil-solution Mg 2+ (high fertility control soil only). Collectively, these data tangentially support our working hypothesis that CO2 enrichment increases nutrient availability. That availability of some nutrients increases without plant growth (control soils), however, suggests an interaction of elevated CO2 with soil microflora.