DOI: 10.5061/dryad.15dv41nw6
title: Ecological data from: Combining botanical collections and ecological data to better describe plant community diversity

description: In this age of rapid biodiversity loss, we must continue to refine our
 approaches to describing variation in life on Earth. Combining knowledge
 and research tools from multiple disciplines is one way to better describe
 complex natural systems. Understanding plant community diversity requires
 documenting both pattern and process. We must first know which species
 exist, and where (i.e., taxonomic and biogeographic patterns), before we
 can determine why they exist there (i.e., ecological and evolutionary
 processes). Floristic botanists often use collections-based approaches to
 elucidate biodiversity patterns, while plant ecologists use
 hypothesis-driven statistical approaches to describe underlying processes.
 Because of these different disciplinary histories and research goals,
 floristic botanists and plant ecologists often remain siloed in their
 work. Here, using a case study from an urban greenway in Colorado, USA, we
 illustrate that the collections-based, opportunistic sampling of floristic
 botanists is highly complementary to the transect- or plot-based sampling
 of plant ecologists. We found that floristic sampling captured a community
 species pool four times larger than that captured using ecological
 transects, with rarefaction and non-parametric species estimation
 indicating that it would be prohibitive to capture the “true” community
 species pool if constrained to sampling within transects. We further
 illustrate that the discrepancy in species pool size between approaches
 led to a different interpretation of the greenway’s ecological condition
 in some cases (e.g., transects missed uncommon cultivated species escaping
 from nearby gardens) but not others (e.g., plant species distributions
 among functional groups were similar between species pools). Finally, we
 show that while using transects to estimate plant relative abundances
 necessarily trades off with a fuller assessment of the species pool, it is
 an indispensable indicator of ecosystem health, as evidenced by three
 non-native grasses contributing to 50% of plant cover along the highly
 modified urban greenway. We suggest that actively fostering collaborations
 between floristic botanists and ecologists can create new insights into
 the maintenance of species diversity at the community scale.
description: We sampled plant communities along the High Line Canal greenway,
 a 66-mile recreational trail that passes through 11 municipalities in the
 Denver-Metro area of Colorado. The trail runs alongside a 71-mile earthen
 canal (owned by Denver Water), which was excavated in the late 1800s to
 support agriculture and human settlement in what was historically native
 plains and foothills shrubland vegetation. The greenway thus represents a
 human-created waterway that is highly managed, yet supports a species pool
 that contains native flora. The greenway’s length (with
 the Canal’s inception located at 39.48362, -105.11293) is demarcated by
 mile markers that we used to generate a random subset of 45 locations at
 which the botanical and ecological field crews could synchronize their
 data collection. As is typical for collections-based floristic surveys,
 the botanical crew sampled exhaustively from early spring (7 May) through
 late summer (28 September) to capture early-, middle-, and late-season
 species. Starting at each of the 45 mile markers, the crew walked in the
 Canal’s downstream direction, searching the greenway for newly encountered
 species to collect and accession to the Kathryn Kalmbach Herbarium (KHD)
 at Denver Botanic Gardens . Most mile marker locations were sampled once
 during the inventory, but a few were revisited if they occurred in a
 vegetation type that would not be re-encountered later in the season at
 the other mile markers (e.g., mile markers zero and one at the inception
 of the Canal were the only locations in the foothills shrubland
 Ecoregion). We used a staggered sampling design in
 which 5 mile markers spanning the southwestern to northeastern extent of
 the Canal were sampled every other week from May to September. The
 floristic survey was carried out over 57 days, comprising 850 search-hours
 and an estimated distance covered of 42 miles (calculated from our daily
 starting and stopping waypoints logged with a GPS unit). The botanical
 crew consisted of two botanists trained in the local flora and one to two
 additional non-botanists who assisted with specimen collection. All
 members of the crew searched for species within an ~50 to 75-foot-wide
 viewshed moving from the bed of the Canal, up the Canal bank, across the
 greenway trail, and over to the property line that marked the end of
 Denver Water’s ownership. High-veracity (with identifying structures)
 herbarium specimens were accessioned for every species encountered during
 the floristic survey (numbering 1570 specimens, including duplicates;
 collections data available). Identifications were made using
 Ackerfield's Flora of Colorado (2015), Wingate's Illustrated
 Keys to the Grasses of Colorado (1994), and Wingate's Sedges of
 Colorado (2017). The ecological sampling was carried
 out over 10 days, from May 22, 2018 to June 6, 2018, to capture a snapshot
 of plant communities around peak biomass. This method of deploying a
 concerted sampling effort over a short time period is common in ecological
 sampling, because it is often of interest to detect treatment differences
 that could be obscured by confounding time lags between sample dates (as
 opposed to the floristic botany goal of exhaustively delineating a species
 pool over time). At each of the 45 miles markers, we laid a 12 m × 2 m
 transect, the length of which captured habitat variation across the
 greenway corridor. We used the line-point intercept method to make field
 observations of plant species presence every 0.25 m along the 12 m
 transect (as well as bare ground, plant litter, and rocks, which we do not
 report herein). In the associated data set, the “first hit” was used to
 generate the reported percent cover estimates (number of hits per species
 per total number of hits), while the “second hit” was used to add species
 to our presence list. We also searched each of the two, one-meter-wide
 belt transects for additional species that were not encountered along the
 line-point transect. Voucher specimens were collected for the species
 encountered during the observational ecological sampling (collected
 outside the transects so as not to influence long-term sampling). However,
 given the short time period of the ecological sampling, not all specimens
 had flowers or fruits, and therefore were not of sufficient quality to be
 curated. All specimens were kept during the field season and subsequent
 analyses to facilitate identifications, but only higher quality specimens
 were accessioned to the herbarium. Please note that one example specimen
 exists for potentially hundreds of field observations (i.e., each time a
 species was encountered along the transects). We chose
 the line-point method as the most appropriate for our system, with its
 narrow and steep canal bank that could not accommodate other plot designs.
 Additionally, our aim with the ecological transects was to estimate not
 only species presence, but also composition. For questions about
 composition, the line-point method is highly repeatable across individuals
 and rapidly deployed, thereby maximizing sampling replicates across many
 locations in a single season. Such transects will capture fewer species
 than other methods (e.g., Modified-Whitaker plots); however, any bounded
 sampling approach will cover considerably less area than can be achieved
 with opportunistic sampling based in the floristic tradition of using the
 habitat itself as the sampling unit. Importantly, we note that it was not
 our goal to equalize the temporal or spatial scales of the two sampling
 approaches (which in our experience is not often done in practice), but
 rather to sample in a manner that is broadly consistent with
 collections-based versus ecological disciplines. The particulars of our
 comparison, such as the sampling window and the use of transects rather
 than any number of plot types, contextualize the results.
description: <strong>Transect Observations Data</strong>
 This data set contains each measurement taken via the line-point
 intercept method in each transect surveyed as well as each additional
 species observed within the 2 meter wide belt transects. InOut values
 indicate whether the species was observed within the transect via the
 line-point intercept method (I) or as an additional species within the 2
 meter wide belt transect (O). Transect.Point.Hit values indicate the
 distance from the transect's origin at which the observaiton was
 recorded. Hit.Number values indicate whether the species was detected as
 top canopy (1) or lower canopy (2) per the line-point intercept method.
 NULL values recorded in Species.Hit indicate the detection of  ground
 surface (non-plant value, such as bare soil). Transect.Latitude indicates
 that latitude at which the site of the transect was established.
 Transect.Longitude indicates the longitude at which the site of the
 transect was established.