DOI: 10.5061/dryad.95x69p8jm
title: Is it best to add native shrubs to a coastal sage scrub restoration project as seeds or as seedlings?

description: Ecological restoration frequently involves the addition of native plants,
 but the effectiveness (in terms of plant growth, plant survival, and cost)
 of using seeds versus container plants has not been studied in many plant
 communities. It is also not known if plant success would vary by species
 or based on functional traits. To answer these questions, we added several
 shrub species to a coastal sage scrub restoration site as seeds or as
 seedlings in a randomized block design. We measured percent cover,
 density, species richness, size, survival, and costs. Over the two years
 of the study, shrubs added to the site as seeds grew more and continued to
 have greater density than plants added from containers. Seeded plots also
 had greater native species richness than planted plots. However, shrubs
 from containers had higher survival rates, and percent cover was
 comparable between the planted and seeded treatments. Responses varied by
 species depending on functional traits, with deep-rooted
 evergreen species establishing better from container plants.  Our
 cost analysis showed that it is more expensive to use container plants
 than seed, with most of the costs attributed to labor and supplies needed
 to grow plants. Our measurements of shrub density, survival, species
 richness, and growth in two years in our experimental plots lead us to
 conclude that coastal sage scrub restoration with seeds is optimal for
 increasing density and species richness with limited funds, yet the
 addition of some species from container plants may be necessary if key
 species are desired as part of the project objectives.
description: Plant density data were collected in April and May of 2017 and
 2018. We randomly placed a 50 cm by 50 cm quadrat near the center of each
 plot and then counted all native and non-native species rooted within the
 quadrat. The native/non-native density and species richness were
 calculated based on the species identity and number of plants found in
 each quadrat. To measure percent cover, we installed
 five 4 m vegetation sampling transects, spaced 0.5 m apart from each other
 with point data collected every 1 m to reach a total of 25 points per
 plot. At each point, we recorded all species present. The raw transect
 data has been rearranged to list each plant (or ground cover) in its own
 row. To evaluate the differences in overall plant
 health between seeded and planted individuals, we flagged individuals in
 both treatments and recorded survivorship over time. We collected plant
 size measurements on flagged native shrubs, measuring height, width, and
 length. Shrubs were checked on several different dates and either measured
 or noted as dead. We used these data to calculate the average lifespan
 (the number of days between the estimated date of germination and the date
 of measurement). We used size measurements from 5/26/18
 to compare final size, and the change in size from 5/30/17 to 5/26/18 to
 compare growth. Relative growth was calculated as the relative change in
 size (height or width) using the formula: (size on 5/26/18 − size on
 5/30/17) ∕ size on 5/30/17. We kept track of the hours
 of labor spent during the first year of our study (2016-2017) to compare
 differences in the time devoted to seeding or planting. We also kept a
 record of all relevant expenses related to the project.
description: The data from block 5 has been removed from all datasets. This
 block was overrun with non-native invasive plants and yielded no useful
 information.<br> Dead individuals were always excluded from all
 datasets.<br> Blocks A-G (the “New” blocks) were not used in our
 analyses due to the very poor survivorship of both seeded and planted
 plants in all plots.