Based on the investigated data of the herbaceous layer under Prunus armeniaca pure forests andPrunus armeniaca-Hippophae rhamnoides mixed forests on different sites in Wuqi County,Shaanxi Province,the succession direction of the herbaceous layer under Prunus armeniaca plantations on different sitesand the ecological restoration effects of these plantations were analyzed by applying the methods of spatiotemporal inter-substitution.Results show that the undergrowth of Prunus armeniaca pure forests on shadygentle,shady steep and sunny gentle slopes changed from the community of Artemisia sacrorum-Lespedezadavuricato the communities of either Carex lanceolata or Artemisia sacrorum-Carex lanceolata.Vegetation of these communities tended to change from xeromorphic to mesophytic.The coverage and biomass ofthe undergrowth in these forests increased with increasing age,while the species diversity decreased slightly.This suggests a forward succession of the undergrowth in single-species Prunus armeniaca forests at thethree site types.In comparison,the index of community characteristics of herbaceous layer under the Prunusarmeniaca-Hippophae rhamnoides mixed forests at the three site types were better than Prunus armeniacapure forests.In single-species Prunus armeniacaforests on sunny steep slope,however,the species composition of the herbaceous layer changed from Potentilla acaulis and Artemisia sacrorum to Glycyrrhiza uralensis and Carex lanceolata.Species diversity,coverage,and biomass decreased significantly over time andthe vegetation tended to change to xeromorphic,indicating? regressive succession.We suggest that treeswith the characteristics of low water consumption and low growing speed,such as Prunus armeniaca,shouldbe placed on shady gentle,shady steep and sunny gentle slopes.Furthermore,the mode of these kinds oftrees mixed with local shrubbery,such as Hippophae rhamnoides,is more positive.For sunny steep slope,however,vegetation of shrubbery with moderate growth rate or grassland that occurs naturally is more suitable.