Ashe juniper (Juniperus ashei : Cupressaceae) canopy and litter effects on understory vegetation in a juniper-oak savanna
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Development of dense stands of Ashe juniper (Juniperus ashei) results in diminished understory herbaceous production and diversity. This study was conducted to examine effects of juniper canopy, shade, soil alteration, and litter accumulation on recruitment and establishment of understory species. Four canopy treatments (with juniper canopy, juniper canopy removed, juniper canopy removed and artificial shade added, and grassland control) and two litter treatments (present or absent) were studied. Recruitment of planted Bouteloua curtipendula, Leptochloa dubia, and Sophora secundiflora seeds was monitored. Thirteen months after planting, a subset of the intact juniper canopy, juniper canopy removed, and grassland treatments was sampled for plant density by species. Removal of Ashe juniper canopies resulted in increased recruitment of planted B. curtipendula and L. dubia. Shade initially did not affect recruitment adversely, but restricted it over time. Reduced recruitment of seeded species in Ashe juniper litter appeared to be due primarily to the interaction of physical features of the litter and the moisture regime rather than chemical alteration or allelopathy. Grass and forb establishment increased with removal of the Ashe juniper canopy and litter. Establishment of S. secundiflora or other shrubs was not affected by the presence of shade, juniper canopy, or juniper litter.