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Citation. Davis, M. A.; Villinski, J.; Banks, K.; Buckman-Fifield, J.; Dicus, J.; Hofmann, S. 1991. Combined effects of fire, mound-building by pocket gophers, root loss and plant size on growth and reproduction in Penstemon grandiflorus. American Midland Naturalist 125:150-161.   [1038  E133  LTER]

Abstract. A 3-yr study examined how plant size and disturbances by fire and pocket gophers affected patterns of growth and reproduction in 2124 Penstemon grandiflorus plants. A late spring burn significantly reduced the probability of reproducing and the probability of increasing in size class both during the year of the burn and during the following year. Mound-building and tunneling behavior of pocket gophers create areas with sparse vegetation. Plants growing naturally in areas with these pocket gopher disturbances showed no change in the probability of reproducing, but did exhibit a significantly higher probability of increasing in size class, and therefore of reproducing sooner. Plants transplanted into an experimentally devegetated pen from which gophers were excluded exhibited greater rates of subsequent growth and reproduction than plants transplanted into a reference pen (naturally vegetated, gophers also excluded). A root removal experiment, designed to simulate gopher herbivory of roots, showed that root loss did not result in a decrease in rate of flowering or pod production in surviving plants. There was no evidence of a fire x vegetation cover interaction on Penstemon growth and reproduction. However, the effects of fire and gophers on growth and reproduction are mediated by plant size, with small plants being those most effected.

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