DOI: 10.5061/dryad.ngf1vhj48
title: Positive indirect effects outweigh negative direct effects of ungulate grazers on population growth of a grassland herb

description: Herbivores can affect plant population growth both directly through the
 damage they inflict on a focal species and indirectly by moderating
 conditions for plant recruitment, nutrient cycling, competition, and other
 biotic interactions, for example, through trampling, defecation, and
 grazing on surrounding vegetation. Still, the relative importance of
 direct vs. indirect effects of herbivores on plant vital rates
 (establishment, survival, fecundity), size, and population growth rate is
 poorly known. We quantified direct and indirect effects of ungulate
 grazers on the population growth rate of the short-lived perennial herb
 Primula farinosa, using integral projection models based on demographic
 data collected over 7 years in exclosures and open control plots in nine
 grassland populations in southern Sweden. Grazers had negative direct
 effects on P. farinosa population growth rate, but these were, on average,
 more than balanced by positive indirect effects. As predicted, the
 strength of the direct negative effect tended to increase with grazing
 intensity. The positive indirect effect was mainly linked to improved
 conditions for plant recruitment and was strongest in populations where
 vegetation height differed most between exclosure and control. Simulations
 indicated that indirect effects of ungulate grazers on population growth
 rate via interactions with pollinators, seed predators, and small
 herbivores were weak. Our study illustrates how both the overall, direct,
 and indirect effects of grazing on plant population growth rate can be
 identified and quantified, and thereby provides a more complete
 understanding of how grazers influence plant fitness, abundance, and
 distribution. Such insight will be crucial for predictions of the effects
 of environmental change on population viability and the management of
 declining species.
description: This data set includes data from a demographic study conducted
 from 2010 to 2016 in control plots and exclosures in nine populations of
 the short-lived perennial herb Primula farinosa in alvar grasslands on the
 island Öland, southern Sweden. During annual censuses, we recorded the
 size, survival, reproductive status (vegetative or flower-producing),
 flower production, and grazing damage to individually marked and mapped
 plants in 1 m<sup>2</sup> squares. For flowering plants
 escaping grazing, we in addition recorded the total number of fruits
 produced, and the number of fruits consumed by the seed predator. In
 addition, we marked and mapped any new recruits. The data have been
 analyzed with code produced in R. Files with code are deposited with the
 data set.
description: # Positive indirect effects outweigh negative direct effects of ungulate
 grazers on population growth of a grassland herb
 [https://doi.org/10.5061/dryad.ngf1vhj48](https://doi.org/10.5061/dryad.ngf1vhj48) ## Description of the data and file structure We quantified direct and indirect effects of ungulate grazers on the population growth rate of the short-lived perennial herb *Primula farinosa*, using integral projection models based on demographic data collected over 7 years in exclosures and open control plots in nine grassland populations in southern Sweden. ### Files and variables #### File: demo.csv **Description:** This file includes all raw data on which the analyses in the paper are based. ##### Variables * Running number: Row number in the data set * pop: Population name. The study was conducted in 9 populations * treat: Treatment: hagn = exclosure, kontroll = control * transitions: Transition. Indicates the years considered. 11-12 = 2011-2012, 12-13 = 2012-2013 etc * Individnr: Plant ID * Morph: Scape morph K = Short, L = Long * Stjalklangd: Length of scape (mm) * PlStat: Plant status first year of transition. 1 = Flower-producing, 2 = Vegetative * BlomStatus: Inflorescence status at fruit maturation first year of transition (code used at plant census in the field): 1 = Intact, 2 = Grazed, 3 = Withered, 4 = Plant not found, 5 = Plant marker not found, 6 = Plant marker moved out of place * size: Leaf rosette diameter at the time of fruit maturation (mm), first year of transition. Value imputed for plants that were vegetative in 2011. * AbortBlm: Number of aborted flowers first year of transition * TotFrukt: Total number of fruits first year of transition * PredFrukt: Number of fruits consumed by the seed predator first year of transition * New: 0 = plant present before first year of transition, 1 = new plant first year of transition * PlStatNext: Plant status second year of transition (code used at plant census in the field): 1 = Flower-producing, 2 = Vegetative, 3 = Dead, 4 = Plant not found, 5 = Plant marker not found * BlomStatusNext: Inflorescence status at fruit maturation, second year of transition (code used at plant census in the field): 1 = Intact, 2 = Grazed, 3 = Withered, 4 = Plant not found, 5 = Plant marker not found, 6 = Plant marker moved out of place * sizeNext: Leaf rosette diameter at the time of fruit maturation (mm), second year of transition * AbortBlmnext: Number of aborted flowers second year of transition * TotFruktNext: Total number of fruits second year of transition * PredFruktNext: Number of fruits consumed by the seed predator second year of transition * NewNext: 0 = plant present before second year of transition, 1 = new plant second year of transition * sq.size: Square root leaf rosette diameter at the time of fruit maturation (mm), first year of transition * sq.sizeNext: Square root leaf rosette diameter at the time of fruit maturation (mm), second year of transition * surv: Survival second year: 0 = Dead, 1 = Alive * flowering: Flower-producing first year of transition. 0 = No, 1 = Yes * Grazed: Inflorescence grazed first year of transition. 0 = No, 1 = Yes * NbIntactFruit: Number of intact fruits first year of transition * TotFlow: Number of flowers first year of transition * fruitPredRate: Proportion of initiated fruits consumed by the seed predator * FrInit: Proportion of flowers initiating fruit development * index: Number indicating a particula Population x treatment x transition combination * mean_fr_pred: For each Population x treatment x transition combination, the mean proportion of fruits consumed by the seed predator in the other treatment in that population x transition is given (this is used in simulations of indirect effects of grazers due to interactions with seed predators) * mean_fr_init: For each Population x treatment x transition combination, the mean proportion of flowers initiating fruit development in the other treatment in that population x transition is given (this is used in simulations of indirect effects of grazers due to interactions with pollinators) * NbIntactFruit_IndPL: Estimated number of intact fruits the first year if observed fruit initiation is replaced by the mean proportion of flowers initiating fruit development in the other treatment in that population x year combination * NbIntactFruit_IndSP: Estimated number of intact fruits the first year if observed seed predation is replaced by the mean proportion of initiated fruits consumed by the seed predator in the other treatment in that population x year combination * NbIntactFruit_IndPLSP: Estimated number of intact fruits the first year if observed fruit initiation and seed predation are replaced by mean proportion of flowers initiating fruit development and mean proportion of initiated fruits consumed by the seed predator in the other treatment in that population x year combination ## Code/software #### File: Demo_3a-_BOOTSTRAPPING_vital_rates_majviva.Rmd **Description:** R code to estimate bootstrapped confidence intervals around vital rates #### File: Demo_3a-_determining_vital_rates.Rmd **Description:** R code to estimate vital rates **File: Demo_6-_LTRE_on_IPM_elements.Rmd** **Description:** R code to conduct the LTRE analysis #### File: Demo_4a_-_IPMs_BOOTSTRAPPING_control_no_grazing.Rmd **Description:** R code to estimate bootstrapped confidence intervals of the difference in stochastic population growth rate between the control and the exclosure treatment. #### File: Demo_4a_-_IPMs.Rmd **Description:** R code to estimate stochastic population growth rate #### File: Demo_4a_-_IPMs.Rmd **Description:** R code to estimate stochastic population growth rate