Environmental resistance strongly deters, but does not eliminate, propagule pressure

This study investigates the dynamics between propagule pressure and environmental resistance in plant invasion using Oxalis stricta L. (common yellow woodsorrel) as a model species. Oxalis stricta is a North American forb that can become invasive in native and novel habitats. A simulated invasion was conducted in a controlled glasshouse environment with propagule pressure from proximate reproducing plants and environmental resistance from planted turfgrass communities (biotic) and environmental heterogeneity in moisture and fertility (abiotic). Whereas O. stricta successfully established and proliferated in bare soil (essentially disturbed) environments with high propagule pressure, its invasion into established plant communities – and subsequent reproduction – was largely inhibited. Additionally, O. stricta reproduction was highest at intermediate levels of O. stricta cover, suggesting that negative density dependence somewhat limited reproductive output. Still, O. stricta was able to ..., The experiment was conducted in a climate-controlled glasshouse bay (3.5 x 6.5 m) November 2020-March 2021. The glasshouse bay walls and floor were thoroughly cleaned before initiating the experiment, and all outside ventilation was kept closed. Eight mature O. stricta plants were collected from plants that naturally colonized plant containers in the glasshouse and placed (2 each) in 4, 27.8 x 54.5 x 6.2 cm trays filled with commercial potting soil. The four O. stricta source trays were placed on growing tables at one end of the glasshouse bay (Fig. 1, S1). The plants were producing ballistic dispersing seeds at the beginning of the experiment. Thirty-two experimental trays were filled with commercial planting soil and half (16) were planted with an equal mix (30 cm3 seeds per species) of the field/turf graminoids and herbaceous plants (hereafter, “plant resistance trays”). Eight experimental trays were each placed on tables at 1, 2, 3 and 4 m distance from the O. stricta source trays. ..., , # Environmental resistance strongly deters, but does not eliminate, propagule pressure

The experiment was conducted in a climate-controlled glasshouse bay (3.5 × 6.5 m) from November 2020 to March 2021. Eight mature *O. stricta* plants producing ballistic seeds were placed in four trays at one end of the bay. Thirty-two experimental trays, half planted with a mix of graminoids and herbaceous plants, were positioned at 1–4 m from the source trays and assigned one of four treatments (control, watering, fertilization, or both). Trays were watered and fertilized according to treatment, and *O. stricta* cover, seedpod production, and seed input (via Styrofoam traps) were monitored weekly.

**Description of the data and file structure**

Cover.data.csv

* Ident = line identifier

- Week = study week

* Date = date of measurement

- Tray = experimental tray identification (number = row; letter = tray)

* Row = experimental row;

- number = meters from source population

* Cover =
percen...,