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The fecundity kernel: reproductive analyses to fill the gap in perennial graminoid demography

Partridge, Sade Perez (2021) The fecundity kernel: reproductive analyses to fill the gap in perennial graminoid demography. Masters thesis, Northern Arizona University.

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The goal of this project is to identify the functional traits and environmental conditions that drive variation in fitness (λ) and vital rates (survival, growth, and reproduction) for native perennial graminoids in the ponderosa pine (Pinus ponderosa Dougl. ex Laws.)-bunchgrass ecosystem of the American Southwest. Using our long-term data from 1-m2 vegetation maps, our plan is to quantify individual plant survival, growth, and reproduction for the most abundant perennial graminoids. However, reproduction data, a crucial element of any demographic and population model, remains elusive. My study quantified reproductive output for the ten most abundant perennial graminoid species in the ponderosa pine forests of the Southwest. I modeled the individual graminoid species reproduction using Integral Project Models (IPM) and the fecundity kernel, which requires information on reproductive output (number of seeds), probability of flowering, and recruitment as a function of the continuous state variable, plant size. In perennial graminoids, reproductive output is challenging to quantify because of the large quantity of seeds produced by each plant. I collected seed production data by graminoid species, and simultaneously collected data on the individual plant’s traits, specifically plant size, number of flower stalks, and maximum flower stalk height. These seed production and trait data were collected for each perennial graminoid species growing around the long-term permanent quadrats, which have been mapped annually for 19 years. I then developed equations to predict seed production as a function of these easier to measure plant traits. I also modeled the probability of an individual plant flowering as a function of plant size and the relationship between seeds produced and plant size for each species using regression techniques. To determine an average recruitment rate for each graminoid species, I quantified annual recruitment from the long-term 1-m2 vegetation maps and estimated reproductive output for each species based on plant size for the past 19 years. Finally, I used the reproductive output relationships, the recruit size distribution, and average recruitment rate to model the fecundity data for each of the ten perennial graminoid species. Although the probability of flowering and reproductive output were high for each species, recruitment rate was low indicating low levels of establishment. Population trends based on plant size are summarized in each fecundity kernel, and in general, perennial graminoid species produce offspring when individual plants are larger. Future studies will use IPMs to model vital rates (survival, growth, and reproduction) for these ten graminoids species and determine how tree shading, precipitation and temperature have affected these population trends.

Item Type: Thesis (Masters)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: herbaceous understory; Integral Projection Model; plant functional traits; plant population dynamics; Southwest; vital rates;Ponderosa pine
Subjects: S Agriculture > SD Forestry
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of the Environment, Forestry, and Natural Sciences > School of Forestry
Date Deposited: 11 Feb 2022 20:48
Last Modified: 11 Feb 2022 20:48
URI: https://openknowledge.nau.edu/id/eprint/5687

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