Exotic plant invasions may alter ecosystem carbon processes, especially when native plants are displaced by plants of a different functional group. Forb invasions into grasslands are common, yet little is known about how they impact carbon cycling. We conducted a field study over 2 years from April 2010 to March 2012 in China to examine changes in soil respiration(R_(soil)) following invasion of exotic perennial forb species(Alternanthera philoxeroides or Solidago canadensis) into an annual grassland dominated by a native annual graminoid(Eragrostis pilosa). Measurements of R_(soil)were taken once a week in stands of the native annual graminoid or one of the forb species using static chamber-gas chromatograph method. Aboveground litterfall of each of the three focal species was collected biweekly and litter decomposition rates were measured in a 6-month litterbag experiment. The monthly average and annual cumulative R_(soil)increased following invasion by either forb species. The increases in cumulative R_(soil)were smaller with invasion of Solidago(36%)than Alternanthera(65%). Both invasive forbs were associated with higher litter quantity and quality(e.g., C:N ratio) than the native annual graminoid. Compared to the native annual graminoid, the invasive forbs Alternanthera(155%) and Solidago(361%) produced larger amounts of more rapidly decomposing litter, with the litter decay constant k being 3.8, 2.0 and 1.0 for Alternanthera, Solidago and Eragrostis, respectively. Functional groups of the invasive plants and the native plants they replaced appear to be useful predictors of directions of changes in R_(soil), but the magnitude of changes in R_(soil)seems to be sensitive to variations in invader functional traits. Exotic plant invasions may alter ecosystem carbon processes, especially when native plants are displaced by plants of a different functional group. Forb invasions into grasslands are common, yet little is known about how they impact carbon cycling. We conducted a field study over 2 years from April 2010 to March 2012 in China to examine changes in soil respiration (R_ (soil)) following invasion of exotic perennial forb species (Alternanthera philoxeroides or Solidago canadensis) into an annual grassland dominated by a native annual graminoid (Eragrostis pilosa). Measurements of R soil (soil) were taken once a week in stands of the native annual graminoid or one of the forb species using a static chamber-gas chromatograph method. Aboveground litterfall of each of the three focal species was collected biweekly and litter decomposition rates were measured in a 6-month litterbag experiment. The monthly average and annual cumulative R_ (soil) increased the following invasion by either forb species. Compared with higher litter quantity and quality (eg, C: N ratio) than the native annual graminoid. Both ases in cumulative R (soil) were smaller with invasion of Solidago (36%) than Alternanthera (65%). to the native annual graminoid, the invasive forbs Alternanthera (155%) and Solidago (361%) produced larger amounts of more rapidly decomposing litter, with the litter decay constant k being 3.8, 2.0 and 1.0 for Alternanthera, Solidago and Eragrostis, respectively. Functional groups of the invasive plants and the native plants they replaced appear to be useful predictors of directions of changes in R_ (soil), but the magnitude of changes in R_ (soil) seems to be sensitive to variations in invader functional traits.