Sodium Chloride Effects on Seed Germination, Growth, and Water Use of Lepidium alyssoides, L. draba, and L. latifolium: Traits of Resistance and Implications for Invasiveness on Saline Soils

In the semiarid southwestern United States, long-term drought, soil salinity, and land-use intensification have increased the risk of invasive plants that threatens landscape biodiversity. Soil-related factors that regulate plant invasions are not adequately known. We evaluated the salinity responses of three invasive plant species during a 3-mo plant growth period in a greenhouse and during a 2–wk seed germination study in the laboratory. The species included the indigenous Lepidium alyssoides A. Gray var. alyssoides (mesa pepperwort) and the exotic, invasive L. draba L. (whitetop) and L. latifolium L. (perennial pepperweed). A NaCl solution at –0.2 MPa reduced germination of L. alyssoides by ≈ 20% and had no effect on germination of L. draba and L. latifolium, merely delaying their mean germination time by a day or less. Reductions in seedling dry matter production and evapotranspiration (ET) were observed following irrigation with NaCl solutions at –0.1 MPa and –0.2 MPa. However, on the basis of ET and total plant dry matter production under common experimental conditions, the salt resistance of these species greatly exceeded that of salt sensitive bean (Phaseolus vulgaris L.) and equaled or exceeded that of salt-resistant cotton (Gossypium hirsutum L.). Below-ground propagating structures giving rise to clonal shoots were observed for all Lepidium spp., consistent with other reports. The results indicate that vegetative propagule pressure and relatively high resistance to salinity at germination and seedling growth stages could contribute to the invasiveness of these species under saline conditions. A broader impact of the findings is in their application to the larger diversity of invasive species to aid in the understanding of soil salinity and how it may govern plant invasions. This dataset could improve risk assessment measures to favor biodiversity in rangelands and natural ecosystems of semiarid regions.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Salinity an Environmental “Filter” Selecting for Plant Invasiveness? Evidence from Indigenous Lepidium alyssoides on Chihuahuan Desert Shrublands

A better understanding of site-specific factors such as soil salinity that regulate plant invasions is needed. We conducted a 3-mo greenhouse study to evaluate the salinity responses of three local maternal sources of Lepidium alyssoides, which is an indigenous species shown to aggressively colonize disturbed shrubland sites in the southwestern United States, including those affected by high salinity and sodicity. Results indicated that there were little or no population effects on plant evapotranspiration (ET), growth, and tissue Na and Cl concentrations. Significant reductions in seedling growth and ET were largely independent of various isosmotic saline irrigation solutions that included NaCl, Na2SO4, and CaCl2, each at − 0.1 MPa and − 0.2 MPa, suggesting that ET and growth were controlled by solution osmotic potential. The combined Na and Cl concentrations in leaves were 9–10% of dry weight with no visible sign of injury. However, increasing leaf mortality and abscission as a proportion of total leaf production was observed in the high-salt treatments (− 0.2 MPa), with a combined Na and Cl concentration reaching 16% with high NaCl. Under saline conditions, considerable foliage salt loads of this species could deposit high-salt litter to potentially alter a landscape to its own favor and to the detriment of other salt-sensitive species. Results of this study add to a limited quantitative database on site-specific salinity factors governing plant invasions by showing the potential for these populations to behave invasively under saline conditions and, thus, potential for soil salinity assessment to predict incipient populations. However, due to its halophytic traits and indigenous status, L. alyssoides may alternatively provide ecosystem services to salinized shrublands of the arid and semiarid southwestern United States.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information