The distribution of flowering across the growing season is governed by each species’ evolutionary history and climatic variability. However, global change factors, such as eutrophication and invasion, can alter plant community composition and thus change the distribution of flowering across the growing season. We examined three ecoregions (tall-, mixed, and short-grass prairie) across the U.S. Central Plains to determine how nutrient (nitrogen (N), phosphorus, and potassium (+micronutrient)) addition alters the temporal patterns of plant flowering traits. We calculated total community flowering potential (FP) by distributing peak-season plant cover values across the growing season, allocating each species’ cover to only those months in which it typically flowers. We also generated separate FP profiles for exotic and native species and functional group. We compared the ability of the added nutrients to shift the distribution of these FP profiles (total and sub-groups) across the growing season. In all ecoregions, N increased the relative cover of both exotic species and C3graminoids that flower in May through August. The cover of C4 graminoids decreased with added N, but the response varied by ecoregion and month. However, these functional changes only aggregated to shift the entire community’s FP profile in the tall-grass prairie, where the relative cover of plants expected to flower in May and June increased and those that flower in September and October decreased with added N. The relatively low native cover in May and June may leave this ecoregion vulnerable to disturbance-induced invasion by exotic species that occupy this temporal niche. There was no change in the FP profile of the mixed and short-grass prairies with N addition as increased abundance of exotic species and C3 graminoids replaced other species that flower at the same time. In these communities a disturbance other than nutrient addition may be required to disrupt phenological patterns.
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This work used data from the Nutrient Network (http://www.nutnet.org) experiment, funded at the site-scale by individual researchers. Coordination and data management have been supported by funding to E. Borer and E. Seabloom from the National Science Foundation Research Coordination Network (NSF-DEB-1042132) and Long Term Ecological Research (NSF-DEB-1234162 to Cedar Creek LTER) programs, and the Institute on the Environment (DG-0001-13).
Relevant plant cover data are available at https://dx.doi.org/10.6084/m9.figshare.4810663. The complete set of plant traits, including species, reported flowering period, functional group, and consulted flora, are available at https://dx.doi.org/10.6084/m9.figshare.4037022. Effect size data available in S1 Table.
Biederman, Lori; Mortensen, Brent; Fay, Philip; Hagenah, Nicole; Knops, Johannes; La Pierre, Kimberly; Laungani, Ramesh; Lind, Eric; McCulley, Rebecca L.; Power, Sally; Seabloom, Eric; and Tognetti, Pedro, "Nutrient Addition Shifts Plant Community Composition Towards Earlier Flowering Species in Some Prairie Ecoregions in the U.S. Central Plains" (2017). Plant and Soil Sciences Faculty Publications. 84.