Plant Ecology

, Volume 203, Issue 1, pp 83–98 | Cite as

The effects of nutrient addition on floral characters and pollination in two subalpine plants, Ipomopsis aggregata and Linum lewisii

  • Laura A. Burkle
  • Rebecca E. Irwin


The availability of soil and pollination resources are main determinants of fitness in many flowering plants, but the degree to which each is limiting and how they interact to affect plant fitness is unknown for many species. We performed resource (water and nutrients) and pollination (open and supplemental) treatments on two species of flowering plants, Ipomopsis aggregata and Linum lewisii, that differed in life-history, and we measured how resource addition affected floral characters, pollination, and reproduction (both male and female function). We separated the direct effects of resources versus indirect effects on female function via changes in pollination using a factorial experiment and path analysis. Resource addition affected I. aggregata and L. lewisii differently. Ipomopsis aggregata, a monocarp, responded to fertilization in the year of treatment application, increasing flower production, bloom duration, corolla width, nectar production, aboveground biomass, and pollen receipt relative to control plants. Fertilization also increased total seed production per plant, and hand-pollination increased seeds per fruit in I. aggregata, indicating some degree of pollen limitation of seed production. In contrast, fertilization had no effect on growth or reproductive output in the year of treatment on L. lewisii, a perennial, except that fertilization lengthened bloom duration. However, delayed effects of fertilization were seen in the year following treatment, with fertilized plants having greater aboveground biomass, seeds per fruit, and seeds per plant than control plants. In both species, there were no effects of resource addition on male function, and the direct effects of fertilization on female function were relatively stronger than the indirect effects via changes in pollination. Although we studied only two plant species, our results suggest that life-history traits may play an important role in determining the reproductive responses of plants to soil nutrient and pollen additions.


Floral traits Life-history Nutrient limitation Plant reproduction Pollen limitation Water addition 



We thank P. McDonald for field assistance and the Irwin lab group for discussion and support. W. Bowman, S. Elliott, M. McPeek, P. Muller, M. Price, L. Rolfe, and three anonymous reviewers provided insightful comments on earlier drafts of this manuscript. Field research was funded by a grant from the Colorado Mountain Club, and supplies were provided by a grant from the National Science Foundation (DEB-0089643).


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© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Department of Biological SciencesDartmouth CollegeHanoverUSA
  2. 2.Rocky Mountain Biological LaboratoryCrested ButteUSA

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