Submitted to: Plant Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2014
Publication Date: 2/11/2014
Citation: Bansal, S., Sheley, R.L., Blank, R.R., Vasquez, E. 2014. Plant litter effects on soil nutrient availability and vegetation dynamics: changes that occur when annual grasses invade shrub-steppe communities. Plant Ecology. 215:367-378. doi: 10.1007/s11258-014-0307-1.
Interpretive Summary: Changes in the quantity and source material of plant litter is occurring in sagebrush-steppe ecosystems as they are invaded by exotic annual grasses, which can impact soil nutrient cycling and thus facilitate or inhibit further invasion. We conducted a 5-year study in which litter was manipulated in spring in communities with differing levels of invasion to determine the impact on soil nitrogen mineralization and vegetation dynamics. In highly invaded communities, litter biomass (prior to removal) was negatively related to mineralization rates, which inhibited exotic annual grass production.
Technical Abstract: Premise of the study: Changes in the quantity and source material of plant litter are occurring in many ecosystems as they are invaded by exotic species, which impacts soil nutrient cycling, seedling establishment, and long-term plant community composition. These changes may facilitate or inhibit further invasion, as may occur in sagebrush-steppe communities invaded by exotic annual grasses. Methods: We conducted a 5-year study in which litter was partially or completely removed in spring in communities with differing levels of invasion to determine the role of above-ground litter on soil nitrogen mineralization and vegetation dynamics. Key results: Litter removal had minimal effects on mineralization rates. In contrast, the original quantity of litter biomass (prior to removal) was positively related to mineralization rates in non-invaded (native) communities and negatively related in highly invaded communities. In partially-invaded communities, litter removal had negative effects on exotic annual grass production during a warm/dry year, while removal had negative effects on native perennial grasses during a cool/wet year, causing a shift in the relative abundances between native and invasive grasses. Structural equation modeling revealed that native litter favored and exotic litter inhibited exotic grass production. Conclusion: We show that litter can facilitate invasion into native or partially-invaded communities or inhibit invasion in highly invaded communities, and that the direction and magnitude of responses to litter manipulation were weather-dependent. Further, we reveal that legacy impacts of plant litter (even after its removal) continue to influence ecosystem processes, demonstrating a long afterlife effect of plants on their habitat.