Community-based long-term management to address reinvasion of restored grassland vernal wetlands

Exotic annual grasses can dominate ecosystems by producing a thick layer of dead plant litter, hereafter “thatch”, that promotes the regeneration of exotic grasses and inhibits native plants. Vernal pool wetlands within a grassland matrix are threatened by these exotic annual grasses, meriting the need for long-term management.  We utilized the investment of local community members to test the efficacy of long-term thatch management on urban vernal pool plant assemblages. We recruited over 40 undergraduate students to perform manual annual summer thatch removal around the edges of 15 urban vernal pools for four years.  We coupled thatch removal with annual native seed addition because our analysis of environmental DNA (“eDNA”) in the soil seed bank revealed a lack of native plant species and an abundance of exotic plant species. We measured vegetation composition in a set of 180 permanent monitoring quadrats (12 per experimental pool) over five years to quantify..., Species Composition Surveys
Plant species cover and richness were monitored annually starting in August 2019 before the first treatment year to determine baseline vegetation composition (all species were identifiable even after senescence), and then in June 2020 to 2023.  Percent cover of each native and exotic species was measured in 12 permanent 1-m2 quadrats in each pool (including the six quadrats that were seeded in the experiment) using a quadrat with 1% subdivisions.  Total percent cover of each quadrat often exceeded 100% due to multiple canopy layers of graminoids and forbs.
Additionally, we measured the richness of native and exotic plant species in the seed bank prior to experimental manipulations.  We collected and mixed three 8 cm-deep soil cores from each of the permanent monitoring quadrats using a 4 cm-diameter auger in July 2019.  We spread 50 g of each homogenized sample over PRO-MIX© BX BiofungicideTM potting soil in germination trays.  Trays ..., # Community-based long-term management to address reinvasion of restored grassland vernal wetlands

Dataset DOI: [10.5061/dryad.7m0cfxq79](10.5061/dryad.7m0cfxq79)

## Description of the data and file structure

From 2019 to 2023, we monitored 15 vernal pools within Del Sol Vernal Pool Preserve (Del Sol) and Camino Corto Open Space (Camino Corto).  These grassland vernal pools were created or restored (e.g., topsoil grading, basin excavation, enhancement of berms around pool basins, native seed addition) in the 1980s and 1990s.  However, at the time of the experiment, the pools were surrounded by unrestored grassland that was dominated by exotic annual grasses.  These invasive grasses can produce a thick layer of dead plant matter, or “thatch”, that promotes the regeneration of exotic grasses while inhibiting native plants.  We set up an experiment to test the impacts of annual thatch manipulation, coupled with native seed addition in a fully-factorial design, on native and exotic plant...,