Interactions Among the Effects of Herbivory, Competition, and Resource Limitation on Chaparral Herbs
Swank SE and Oechel WC. 1991. Interactions Among the Effects of Herbivory, Competition, and Resource Limitation on Chaparral Herbs. Ecology. 72(1):104-115
Older chaparral stands are frequently characterized by gaps in the canopy and by a lack of herbaceous vegetation in these openings. Many causes for the lack of herb growth in gaps have been postulated, including lack of seeds in the soil, limited nutrients and water, competition with shrubs for resources, interference competition (i.e., allelopathy), and herbivory. An experiment was conducted to assess the individual and combined effects of four main factors (trenching to reduce root competition, caging to reduce herbivory, nutrient addition, and water addition) on herb germination, survival, and growth in chaparral dominated by chamise, Adenostoma fasciculatum. We found strong interactions among these treatments. Therefore, no single factor can be regarded as causing the absence of herbs in chaparral. Herb establishment was limited by herbivory and root competition with shrubs for limited nutrients and/or water. Survival was enhanced by trenching, caging, and water. Growth was enhanced by nutrient addition, but the magnitude of this nutrient effect became appreciable only within trenched, caged plots. The vegetative cover of annual herbs in gaps was limited by the combined effects o herbivory, competition with the roots and shrubs, inadequate nutrients, and inadequate water.
- Type
- Journal Article
- Authors
- Swank, Sarah; Oechel, Walter
- Units
- SODN
- Keywords
- Adenostoma fasciculatum, allelopathy, California, chaparral herbs, Competition, Germination, Grazing, herb biomass, Herbivory, resource limitation, Seedling