# Implications of germination tolerances on invasion potential of Arthraxon hispidus

## TL;DR

This study explores how Arthraxon hispidus, an invasive grass, germinates under various environmental conditions, showing it can thrive in many regions.

## Contribution

The study reveals the germination tolerances of Arthraxon hispidus, highlighting its potential to invade new areas.

## Key findings

- Arthraxon hispidus germinates well across a wide range of temperatures and pH levels.
- It can germinate in high salinity and low osmotic potential, indicating resilience to drought.
- Burial depth significantly reduces its germination success, suggesting a short-lived seed bank in moist environments.

## Abstract

Arthraxon hispidus is an introduced, rapidly spreading, and newly invasive grass in the eastern United States, yet little is known about the foundational biology of this aggressive invader. Germination responses to environmental factors including salinity, pH, osmotic potential, temperature, and burial depth were investigated to better understand its germination niche. Seeds from six populations in the Mid-Atlantic US germinated 95% with an average mean time to germination of 3.42 days of imbibition in the dark at 23°C. Germination occurred across a temperature range of 8–37°C and a pH range of 5–10 (≥83%), suggesting that neither pH nor temperature will limit germination in many environments. Arthraxon hispidus germination occurred in high salinity (342 mM NaCl) and osmotic potentials as low as -0.83MPa. The NaCl concentration required to reduce germination by 50% exceeded salinity concentrations found in soil and some brackish water saltmarsh systems. While drought adversely affects A. hispidus, 50% germination occurred at osmotic potentials ranging from -0.25 to -0.67 MPa. Given the climatic conditions of North America, drought stress is unlikely to restrict germination in large regions. Finally, emergence greatly decreased with burial depth. Emergence was reduced to 45% at 1–2 cm burial depths, and 0% at 8 cm. Emergence depths in concert with adequate moisture, germination across a range of temperatures, and rapid germination suggests A. hispidus’ seed bank may be short-lived in moist environments, but further investigation is warranted. Given the broad abiotic tolerances of A. hispidus and a widespread native range, A. hispidus has the potential to germinate in novel territories beyond its currently observed invaded range.