Does An Exotic Invasive Grass Facilitate The Invasion Of A Woody Species Into Remnant Prairies?: A Study of The Native, Prosopis glandulosa And the Alien, Sorghum halapense




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The native tree, Prosopis glandulosa, and the exotic grass, Sorghum halepense, have been invading native prairies in the Southwest U.S. since the 1800s. My objectives were to determine if S. halepense was driving shifts in the abiotic and biotic structure of a native prairie and in doing so facilitating the invasion of P. glandulosa. Both field and greenhouse experiments were established to address these objectives. The presence of S. halepense lowered light and increased soil N in the field relative to the native prairie. Plant species diversity and the number of woody species were higher in an invaded zone than a native zone. Litter inhibited P. glandulosa germination in the field. More seeds germinated in the invaded zone than the native zone. Competition from neighbors inhibited seedling growth. Soil abiotic resources and community structure were being altered in a way that facilitated seedling recruitment but not growth of P. glandulosa.