Reinvasion of restored California vernal pools reveals the importance of long‐term restoration planning
Data files
Sep 19, 2023 version files 4.26 MB
Abstract
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.
README: Reinvasion of restored California vernal pools reveals the importance of long‐term restoration planning
https://doi.org/10.25349/D97P6W
# Approach 1: Multi-Year Monitoring Study ("np_percent_cover.csv")
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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 1m2 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.
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## Sharing/Access information
Data was derived from hand-taken field notes of researchers and collaborators.
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# Metadata for Approach 1: Multi-Year Monitoring Study (“metadata.csv”)
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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 1m2 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.
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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.
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## Sharing/Access information
Data was derived from hand-taken field notes of researchers and collaborators.
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# Approach 2: Chronosequence Survey (“chronosequence.csv")
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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 1m2 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.
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## 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.
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## Sharing/Access information
Data was derived from Survey123 records. Survey123 cloud files are available upon request.
Methods
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 1m2 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 1m2 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.