摘要
This study was conducted in southern Tunisia in the growing seasons of 2013 and 2014, and aimed to compare the effects of exotic and endogenous shrub species （Haloxylon persicum and Retama raetam, respectively） on understory vegetation and soil nutrients. For each shrub species, the canopied sub-habitat （under the shrub crown） and un-canopied sub-habitat （in open grassland area） were distinguished. The concentrations of soil nutrients （organic matter, total nitrogen and extractable phosphorus） were found to be significantly higher （P〈0.05） under R. raetam canopy than under H. persicum canopy and in open area. The result also showed that the presence of shrubs improved all the values of understory vegetation parameters （floristic composition, density, total plant cover and dry matter） and all these values were significantly higher under endogenous species canopy than under exotic species canopy. These results highlighted the positive effect of endogenous shrubs on understory vegetation and soil nutrients compared to the exotic ones in the Saharan areas of Tunisia.
This study was conducted in southern Tunisia in the growing seasons of 2013 and 2014, and aimed to compare the effects of exotic and endogenous shrub species （Haloxylon persicum and Retama raetam, respectively） on understory vegetation and soil nutrients. For each shrub species, the canopied sub-habitat （under the shrub crown） and un-canopied sub-habitat （in open grassland area） were distinguished. The concentrations of soil nutrients （organic matter, total nitrogen and extractable phosphorus） were found to be significantly higher （P〈0.05） under R. raetam canopy than under H. persicum canopy and in open area. The result also showed that the presence of shrubs improved all the values of understory vegetation parameters （floristic composition, density, total plant cover and dry matter） and all these values were significantly higher under endogenous species canopy than under exotic species canopy. These results highlighted the positive effect of endogenous shrubs on understory vegetation and soil nutrients compared to the exotic ones in the Saharan areas of Tunisia.
