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Data from: Incorporating temporal dynamics to enhance grazing management outcomes for a long-lived species

Cite this dataset

Larios, Loralee; Hallett, Lauren (2022). Data from: Incorporating temporal dynamics to enhance grazing management outcomes for a long-lived species [Dataset]. Dryad. https://doi.org/10.6086/D1KD6R

Abstract

Identifying successful management strategies for long-lived species is challenging, especially in fluctuating environments, because the response of individual vital rates and overall growth rates to management action can vary over time. A demographic approach that isolates the impact of management and environment on individual vital rates, and assesses their importance for growth rate over time, can indicate whether and why a management strategy is successful.

Here we take a demographic approach to assess the success of grazing management for the perennial grass Stipa pulchra, the state grass of California and a focus of conservation efforts. We tracked S. pulchra populations in paired grazed and ungrazed plots over six years, which included an historic drought and an El Niño rain year, and calculated summary transition matrices for the main effects of year, grazing, and year x grazing interaction for each site. We averaged these summary transition matrices to calculate population growth rates, l, for the main effects of year, grazing, and year x grazing and used life table response experiment (LTRE) analysis to compare how individual vital rates contributed to differences in l between grazed and ungrazed plots over time.

Overall we found that grazing was a successful management strategy; grazed populations maintained a positive average population growth rate whereas ungrazed populations declined. We found that grazing had a larger positive effect on growth rates in wet years than drought years. This was because grazed populations benefited from a greater contribution of adult growth immediately following the end of the drought compared to ungrazed populations, and from adult survival thereafter.

Synthesis and applications. Although Stipa pulchra is the focus of many management efforts, the use of grazing for management is contentious, and there have been few studies that take a demographic approach to understanding S. pulchra responses over time. Our results indicate that conservation and restoration efforts should move beyond recruitment to focus on adult growth and survival for overall population success. To this end, moderate grazing can be a successful strategy to maintain S. pulchra populations and is particularly important in wet years to promote plant growth.

Usage notes

Annual transition values for individual Stipa plants from 2014 through 2019 (JAppl_VC_20141516171819.csv) All values were measured for Stipa pulchra individuals at the Vasco Caves Regional Preserve and Los Vaqueros Watershed, Byron, CA. Please see Larios & Hallett 2022 for details of experimental design and data collection.

Column metadata

secondYear = The second year of the transition (e.g., 2015 indicates the change from 2014 to 2015)

Site = The name of the grazed and ungrazed pair of plots (Plot10, Plot15, Plot2, PlotBN, PlotBS, PlotNCow) within the Vasco Caves Regional Preserve or Los Vaqueros Watershed. Plot10, Plot15, and Plot2 included previously established grazing exclosures, the rest were established at the beginning of the experiment. All grazed plots were sheep grazed except in PlotNCow, which was cattle grazed. See Larios & Hallett 2022 for site details

Plot = The name of the plot within a pair. G indicates a grazed plot, U indicates ungrazed

Treatment = Whether the plot was grazed or not (coded as Grazed and Ungrazed)

Transect = The transect within the plot, named by the distance in meters from the initial transect (transect 0)

Subplot = The subplot within a transect, named by distance in meters along the transect

Individ2 = A unique number for each individual Stipa plant found within a subplot

Grazer = Which type of grazer was in the grazed treatment (coded as either Sheep or Cow)

stage = The stage class of the individual Stipa plant in the first year of the transition (e.g., if secondYear is 2015, stage refers to the life stage in 2014). stage is coded as either seedling (when the individual was observed as a seedling in the first year), continuous (when the individual was a juvenile or adult in the first year), or NA (when the individual did not appear until the second year)

stageNext = The stage class of the individual Stipa plant in the second year of the transition (e.g., the same year as secondYear). stageNext is coded as either seedling (when the individual was observed as a seedling in the second year), continuous (when the individual was either a juvenile or adult), or dead (when the individual was present in the first year but not in the second)

size = The area in cm2 of the individual Stipa plant in the first year of the transition

sizeNext = The area in cm2 of the individual Stipa plant in the second year of the transition

surv = Whether the individual survived the transition from the first to second year, coded as a binary (0 if the individual did not survive, 1 if it did)

offspringNext = Whether the individual was offspring that appeared in the second year of the transition (coded as NA if the individual was present in the first year, and sexual if the individual was a seedling in the second year)

fec = Whether the individual produced seeds in the second year, coded as a binary (0 if the individual did not produce seeds, 1 if it did)

fec1 = The number of culms the individual produced in the second year if it produced seeds

seed = The average estimated number of seeds per culm produced for Stipa plants within that plot pair

Transition Matrices for six populations that were either grazed or ungrazed over five transition periods from 2014 to 2019 (JAppl_Stipa Matrices_2014_2019.csv) All probabilities were estimated from the censused data reported in the annual transition values file entry (JAppl_VC_20141516171819.csv). Please see Larios & Hallett 2022 for details of experimental design and data collection.

Column metadata

secondYear – The second year of the transition (e.g., 2015 indicates the change from 2014 to 2015)

Treatment - Whether the plot was grazed or not (coded as Grazed and Ungrazed)

Site - The name of the grazed and ungrazed pair of plots (Plot10, Plot15, Plot2, PlotBN, PlotBS, PlotNCow) within the Vasco Caves Regional Preserve or Los Vaqueros Watershed. Plot10, Plot15, and Plot2 included previously established grazing exclosures, the rest were established at the beginning of the experiment. All grazed plots were sheep grazed except in PlotNCow, which was cattle grazed. See Larios & Hallett 2022 for site details

sdlg_sdlg – Transition probability for seedlings staying seedlings

juv_sdlg - Transition probability for juvenile fecundity

adult_sdlg - Transition probability for adult fecundity

sdlg_juv - Probability for seedlings transitioning to juveniles

juv_juv - Transition probability for juveniles staying juveniles

adult_juv - Probability for an adult to regress to a juvenile

sdlg_adult - Probability for seedlings transitioning to adults

juv_adult - Probability for juveniles transitioning to adults

adult_adult - Transition probability for adults staying adults

Funding

East Bay Regional Park District