DOI: 10.25349/d97p6w
title: Reinvasion of restored California vernal pools reveals the importance of long‐term restoration planning

description: Ecological restoration often focuses on short‐term intervention efforts
 with the goal of creating restored ecosystems that do not require
 continuous human maintenance. Here, we ask: Do short‐term restoration
 efforts result in self‐sustaining native assemblages, or do these restored
 ecosystems require long‐term management to prevent reinvasion of exotic
 species? We address this question using restored vernal pool wetlands in
 coastal California. Restoration efforts in vernal pool ecosystems are
 often hindered because many restored vernal pools exist within a grassland
 matrix that is highly invaded by exotic annual grasses and forbs. To test
 whether restored pools experienced reinvasion, we assessed plant species
 abundance and diversity at varying times after intensive weeding had
 ceased. The central bottom of pools, where inundation duration is the
 longest, showed stable or even increasing native cover and no trends in
 exotic abundance over time. However, exotic cover and richness increased
 in the upland edges of the pools, where drier conditions allow exotic
 grasses from the surrounding unrestored grassland to grow. Our findings
 indicate that edges of restored ecosystems are susceptible to invasion
 over time, but that this depends on abiotic and biotic conditions within
 the ecosystem, such as pool shape and landscape matrix, that can
 potentially be manipulated through initial planning (e.g., constructing
 circular pools) and long‐term management (e.g., annual weeding). Our
 findings highlight the importance of ongoing monitoring and adaptive
 management and support a paradigm shift away from short‐term interventions
 and toward viewing restoration as a longstanding relationship with the
 land that may require continuous human management.
description: Approach 1: Multi-Year Monitoring Study
 ("np_percent_cover.csv") From 2016 to 2019,
 we monitored seven restored vernal pools within UCSB’s North Parcel, which
 consists of vernal pools built amidst university faculty housing.  Within
 each restored vernal pool, we established a series of permanent monitoring
 quadrats.  We delineated each pool into central (experiencing longest
 inundation period), transition (inundated or hydric soil during longest
 inundation period), and upland (inundated during extreme storms but
 otherwise non-hydric soils) zones (Figure 2A).  Within each of these
 zones, we haphazardly placed three 1m<sup>2</sup> quadrats,
 for a total of nine quadrats per pool.  We monitored the vernal pools
 monthly from November 2016 to December 2019.  Because the pools were
 different ages at the start of the experiment, sampling over three years
 allowed us to evaluate the vegetation community in pools ages two to nine
 years old.  Within each quadrat, we determined the identity and percent
 cover of all species present.  We also recorded the percent cover of bare
 ground, water, and thatch (dead plant matter).  Additionally, we estimated
 the number and percent cover of germinating seedlings for native species. 
 Because low-growing graminoids and forbs were often overlaid by taller
 species, total percent cover could exceed 100% in each quadrat.
 Approach 2: Chronosequence Survey
 ("chronosequence.csv") The 69 pools surveyed
 in this study were restored between 1986 and 2017.  In the spring of 2019,
 we conducted vegetation surveys in each pool when the majority of the
 native species were at peak biomass.  For each pool, we laid out two
 transects bisecting the pool along its elliptical major and minor axes
 (Figure 2B).  Every other meter along each transect, we laid down a
 1m<sup>2</sup> quadrat with 10% subdivisions.  We identified
 every plant species present and estimated its percent cover in each
 quadrat.  We also estimated percent cover of bare ground and thatch. 
 Because low-growing graminoids and forbs were overlaid with taller
 species, total percent cover could exceed 100% in each quadrat.  We also
 categorized each quadrat as being in the central, transition, or upland
 zone of the pool.  To
 measure relative elevation, we used a laser level to calculate the
 elevation of each quadrat above the deepest point of the pool.  To
 determine pool hydroperiod, we installed 0.8m rulers in the deepest part
 of each pool in January 2019 and recorded the depth of the water in each
 pool every week beginning 11 January until all the pools dried up by 5
 July.  To measure the site and pool area, we used a Trimble GPS to map out
 the perimeters of the sites and the pools.  We also used these data to
 calculate each pool’s perimeter-to-area ratio and the distance of each
 pool from the edge of the restoration site.
description: # Reinvasion of restored California vernal pools reveals the importance of
 long‐term restoration planning
 [https://doi.org/10.25349/D97P6W](https://doi.org/10.25349/D97P6W) \#
 Approach 1: Multi\-Year Monitoring Study
 \("np\_percent\_cover\.csv"\) — From 2016 to 2019, we monitored
 seven restored vernal pools within UCSB’s North Parcel, which consists of
 vernal pools built amidst university faculty housing.  Within each
 restored vernal pool, we established a series of permanent monitoring
 quadrats.  We delineated each pool into central (experiencing longest
 inundation period), transition (inundated or hydric soil during longest
 inundation period), and upland (inundated during extreme storms but
 otherwise non-hydric soils) zones (Figure 2A).  Within each of these
 zones, we haphazardly placed three 1m<sup>2</sup> quadrats,
 for a total of nine quadrats per pool.  We monitored the vernal pools
 monthly from November 2016 to December 2019.  Because the pools were
 different ages at the start of the experiment, sampling over three years
 allowed us to evaluate the vegetation community in pools ages two to nine
 years old.  Within each quadrat, we determined the identity and percent
 cover of all species present.  We also recorded the percent cover of bare
 ground, water, and thatch (dead plant matter).  Additionally, we estimated
 the number and percent cover of germinating seedlings for native species. 
 Because low-growing graminoids and forbs were often overlaid by taller
 species, total percent cover could exceed 100% in each quadrat.   \#\#
 Data stored in tidy format as \.csv\.  Each row corresponds to the percent
 cover recorded of one species in the specified quadrat\.  “Month” and
 “Year” are the month and year the quadrat was monitored\.  “Plot” is the
 name of the vernal pool in which the permanent quadrat resides\. 
 “Replicate” is the unique ID of each permanent quadrat\.  “Species” is the
 four\-letter code of each plant species\, with the first two letters being
 the first two letters of the genus and the last two letters being the
 first two letters of the species\, e\.g\.\, *Festuca perennis* is coded as
 “FEPE”.  Exceptions are codes ‘THATCH” (dead plant matter), “WATER”
 (standing water), “BARE” (bare ground), and “UNK GRASS” (unknown,
 unidentifiable grass).   See “metadata” file for full species names and
 associated codes.  “percent\_cover” is the percent cover of each species
 estimated in the quadrat, and “abundance” is the number of individuals of
 each species counted in each quadrat. <br> \#\# Sharing/Access
 information Data was derived from hand-taken field notes of researchers
 and collaborators. <br> <br> <br> <br> <br>
 \# Metadata for Approach 1: Multi\-Year Monitoring Study
 \(“metadata\.csv”\) — From 2016 to 2019, we monitored seven restored
 vernal pools within UCSB’s North Parcel, which consists of vernal pools
 built amidst university faculty housing.  Within each restored vernal
 pool, we established a series of permanent monitoring quadrats.  We
 delineated each pool into central (experiencing longest inundation
 period), transition (inundated or hydric soil during longest inundation
 period), and upland (inundated during extreme storms but otherwise
 non-hydric soils) zones (Figure 2A).  Within each of these zones, we
 haphazardly placed three 1m<sup>2</sup> quadrats, for a total
 of nine quadrats per pool.  We monitored the vernal pools monthly from
 November 2016 to December 2019.  Because the pools were different ages at
 the start of the experiment, sampling over three years allowed us to
 evaluate the vegetation community in pools ages two to nine years old. 
 Within each quadrat, we determined the identity and percent cover of all
 species present.  We also recorded the percent cover of bare ground,
 water, and thatch (dead plant matter).  Additionally, we estimated the
 number and percent cover of germinating seedlings for native species. 
 Because low-growing graminoids and forbs were often overlaid by taller
 species, total percent cover could exceed 100% in each quadrat. <br>
 This file contains additional information about the species recorded in
 this monitoring survey, including the full scientific species names that
 correspond to the four-letter species codes used in the
 “np\_percent\_cover.csv” dataset.   \#\# Data stored in tidy format as
 \.csv\.  Each row corresponds to one species\.  “Species” is the
 four\-letter code of each plant species\, with the first two letters being
 the first two letters of the genus and the last two letters being the
 first two letters of the species\, e\.g\.\, *Festuca perennis* is coded as
 “FEPE”.  Exceptions are codes ‘THATCH” (dead plant matter), “WATER”
 (standing water), “BARE” (bare ground), and “UNK GRASS” (unknown,
 unidentifiable grass).   See “metadata” file for full species names and
 associated codes.  “Species\_Full\_Name” is the full scientific name of
 the species.  “Native\_Status” describes each species as either “N”
 (native) or “E” (exotic) to California.  “Growth\_Form” is the growth form
 of each species, either “A” for annual, “P” for perennial, or “AP” for
 annual-perennial (i.e., can be annual or perennial).  “Bloom\_Start” and
 “Bloom\_End” are the months in which the species starts to flower and
 ceases to flower, as numeric months.  “Dominant\_Zone” is the zone in
 which each species is most likely to be found in a vernal pool, either “E”
 (Edge of the vernal pool adjacent to upland”, “T” (Transition zone
 adjacent to edge), or “C” (Central bottom of the vernal pool). 
 “Max\_Height” is the maximum height that the species usually grows, in
 cm.  “Family” is the plant family of the species. “Growth\_Habit” is the
 growth habit of the species, either graminoid, forb, shrub, or tree. 
 “Wetland\_Obligate” categorizes each species as a wetland obligate (“Y”
 for Yes, “N” for No).  “Disturbance\_Favored” categorizes each species as
 a species that grows well in disturbance (“Y” for Yes, “N” for No). 
 Species information was gathered from Calflora.org and Calscape.org. Blank
 cells indicate missing data, e.g., there is no consensus on whether or not
 a species is a wetland obligate. <br> \#\# Sharing/Access
 information Data was derived from hand-taken field notes of researchers
 and collaborators. <br> <br> <br> <br> <br>
 <br> \# Approach 2: Chronosequence Survey
 \(“chronosequence\.csv"\) — The 69 pools surveyed in this study were
 restored between 1986 and 2017.  In the spring of 2019, we conducted
 vegetation surveys in each pool when the majority of the native species
 were at peak biomass.  For each pool, we laid out two transects bisecting
 the pool along its elliptical major and minor axes (Figure 2B).  Every
 other meter along each transect, we laid down a 1m<sup>2</sup>
 quadrat with 10% subdivisions.  We identified every plant species present
 and estimated its percent cover in each quadrat.  We also estimated
 percent cover of bare ground and thatch.  Because low-growing graminoids
 and forbs were overlaid with taller species, total percent cover could
 exceed 100% in each quadrat.  We also categorized each quadrat as being in
 the central, transition, or upland zone of the pool. To measure relative
 elevation, we used a laser level to calculate the elevation of each
 quadrat above the deepest point of the pool.  To determine pool
 hydroperiod, we installed 0.8m rulers in the deepest part of each pool in
 January 2019 and recorded the depth of the water in each pool every week
 beginning 11 January until all the pools dried up by 5 July.  To measure
 the site and pool area, we used a Trimble GPS to map out the perimeters of
 the sites and the pools.  We also used these data to calculate each pool’s
 perimeter-to-area ratio and the distance of each pool from the edge of the
 restoration site. <br> \#\# Data stored in tidy format as \.csv\. 
 Each row corresponds to the percent cover recorded of one species in the
 specified quadrat\.  “location” is the name for the restoration site in
 which the quadrat resides\.  “pool\_id” is the name of the vernal pool in
 which the quadrat resides\.  “site\_area\_m2” is the area of the
 restoration site\, in m2\, in which each pool resides\.  “pool\_area\_m2” 
 is the area of the pool\, in m2\, in which each quadrat resides\. 
 “pool\_circumference\_ft” is the length of the perimeter of the pool in
 ft\, in which the quadrat resides\.  “pool\_edge\_ratio” is the ratio of
 the pool’s perimeter to its area\, in m2/m\.   “edge\_distance\_max” is
 the distance\, in m\, from the edge of the pool to the farthest edge of
 the restoration site in which each pool resides\.  “restoration\_year” is
 the year in which restoration of a pool began\.  “time\_since” is the
 number of years between the start of restoration and the data collection
 in 2019\.  “period” is the inundation period\, in days\, of each pool\. 
 “depth\_cm” is the depth of the deepest point of each pool when it is
 fully inundated\. "global\_id" is a unique identifier for the
 row in the Survey123 cloud server\. "monitor\_names" contains
 the names of the field researchers who collected the vegetation data\. 
 “transect\_axis” is the transect\, either the “major” \(longest\) or
 “minor” \(perpendicular to longest\)\, that the quadrat resides\. 
 “total\_transect\_length” is the total length of the transect\, in
 meters\, on which the quadrat resides\.  “transect\_notes” are any
 observational notes about the transect recorded by the researcher in the
 field\.  “transect\_distance\_of\_quadrat” is the distance along the
 transect\, in meters\, that the quadrat is located\, and
 “side\_oft\_transect” indicates whether the quadrat was justified to the
 “Right” or “Left” of the transect\.  “vegetation\_zone” is the zone in
 which the quadrat resides\, either “edge” \(edge of the vernal pool
 adjacent to upland”\, “transition” \(adjacent to edge\)\, or “bottom”
 \(central bottom of the vernal pool\)\.  “quadrat\_notes” are any
 observational notes about the quadrat recorded by the researcher in the
 field\.  “percent\_bare\_ground” is the estimated percent cover of bare
 ground in the quadrat\.  “percent\_thatch” is the estimated percent cover
 of thatch \(dead plant matter\) in the quadrat\. 
 “count\_of\_native\_species\_automatically\_calculated” is the native
 species richness of the quadrat\, automatically calculated from the number
 of species with recorded percent cover\. 
 “sum\_of\_native\_species\_automatically\_calculated” is the total cover
 of all native species in the quadrat\, automatically calculated from the
 percent cover of each native species estimated in the quadrat\. 
 “count\_of\_non\_native\_species\_automatically\_calculated” is the
 non\-native species richness of the quadrat\, automatically calculated
 from the number of species with recorded percent cover\. 
 “sum\_of\_native\_species\_automatically\_calculated” is the total cover
 of all non\-native species in the quadrat\, automatically calculated from
 the percent cover of each species estimated in the quadrat\.  
 “count\_of\_unknown\_species\_automatically\_calculated” is the
 unidentifiable species richness of the quadrat\, automatically calculated
 from the number of species with recorded percent cover\. 
 “sum\_of\_unknown\_species\_automatically\_calculated” is the total cover
 of all unidentifiable species in the quadrat\, automatically calculated
 from the percent cover of each species estimated in the quadrat\.  
 “sum\_of\_all\_cover\_automatically\_calculated” is the total cover of all
 cover types \(species\, bare ground\, thatch\) in the quadrat\,
 automatically calculated from the percent cover of each cover type
 estimated in the quadrat\.  “type” is the native status of the species in
 California\, either “native”\, “nonnative” or “unknown” \(or “other” for
 non\-plant cover types\)\.  “species” is the scientific species name of
 the plant species\, which was selected from a dropdown menu of known
 species in the sites \(this is "NA" if the row corresponds to
 non\-plant cover types\)\. “percent\_cover” is the estimated percent cover
 of the species in each quadrat\.  “creation\_date” is the date that the
 survey was created\.  “creator” is the account name of the researcher
 recording the data\.  “edit\_date” is the date that a survey was edited\,
 if corrections were made after data were taken in the field \(e\.g\.\,
 identifying unidentified species\, correcting typographical errors\)\. 
 “editor” is the account name of the researcher who edited the survey\.  
 “quadrat\_id” is a unique identifier for each quadrat\, comprised of a
 concatenation of the “location”\, “pool\_id”\, and
 “transect\_distance\_of\_quadrat”\.  “topo\_0\_m” is the elevation of each
 quadrat\, in m\. <br> \#\# Sharing/Access information Data was
 derived from Survey123 records.  Survey123 cloud files are available upon
 request.