Germination biology of four climatically varied populations of the invasive species African lovegrass (Eragrostis curvula)

Abstract

African lovegrass [Eragrostis curvula (Schrad.) Nees] is a highly invasive C4 perennial grass that threatens global biodiversity. Appropriate management of the species has been hampered by a lack of knowledge of the species’ seed ecology, resulting in significant economic and environmental impacts within various environments. Consequently, this study explored the effects of a selection of environmental factors (photoperiod, alternating temperature, pH and salinity) by analysing several measures of germination on four geographically distinct populations of E. curvula to assist in its extirpation from infested sites. Seeds were collected in Australia from Maffra and Shepparton, Victoria; Tenterfield, New South Wales and Midvale, Western Australia. Key results showed that seeds from Maffra (54% vs. 79%), Tenterfield (38% vs. 61%) and Shepparton (34% vs. 71%) had significantly reduced germination in complete darkness compared to an alternating 12 hours light and 12 hours dark photoperiod, whereas Midvale had consistent germination (91% vs. 99%). Temperatures between 17/7 OC reduced germination for Maffra (42% vs. 73%), Tenterfield (34% vs. 55%) and Shepparton (33% vs. 59%) compared to the mean of all other temperature combinations, whereas, Midvale had consistent germination. Furthermore, germination for all populations was consistent between pH 4 and 9. For salinity, germination was significantly reduced at ≥100 mM for Maffra (29% vs. 67%), ≥150 mM for Tenterfield (29% vs. 94%) and Shepparton (39.5% vs. 81.5%), and 250 mM for Midvale (39% vs. 82%) compared to the mean of all other concentrations. Although each trial was conducted independently, they can be used to generate species targeted management. Such strategies include maintaining high levels of quarantine and hygiene programs to avoid future spread, where practical apply light-limiting strategies (mulching, tilling or scraping) for the Maffra, Tenterfield and Shepparton populations; and maintaining management efforts year round as the species can germinate under a wide range of conditions.

Germination biology, distribution and control of the invasive species Eragrostis curvula [Schard. Nees] (African Lovegrass): A global synthesis of current and future management challenges

“…Eragrostis curvula seed germination can occur at any time of the year, but it is most common within the warmer months of the year, between the seasons of spring to autumn (Table 1) (Firn, 2009; Roberts et al, 2021). Eragrostis curvula growth and germination can be suppressed by native species if its germination is delayed by up to three weeks compared with co‐occurring species (Firn et al, 2010b).…”

“…Therefore, it is critical for E. curvula to develop mechanisms for early emergence and establishment to avoid direct competition from co‐occurring native species (Firn et al, 2010b). Such mechanisms used by E. curvula to achieve this include quick germination and seedling growth (Roberts et al, 2021), early flowering times and fast growth rates (Han et al, 2012) and the production of thousands of small seeds (Johnston and Cregan, 1979). However, when temperatures are below 10 O C the germination and growth of E. curvula are often slower (Firn, 2009; Han et al, 2012; Roberts et al, 2021).…”

“…Nees] (African Lovegrass) is an invasive C 4 perennial grass that threatens the multifunctionality of agricultural landscapes in Australia, including agricultural productivity and biodiversity (Firn, 2009; Godfree et al, 2017). It is often described as an undesirable and moderately palatable species that is commonly found on lighter sandy soils along coastal areas within Australia; however, it can also be found further inland if conditions are suitable (Godfree et al, 2017; Roberts et al, 2021). When established, E. curvula can form dense swards that increase its competitiveness towards other species (Firn, 2009; Firn et al, 2010b; Johnston, 1989; Muyt, 2001).…”

“…Although E. curvula shows signs of being competitive in disturbed or neglected regions, particularly when establishing prior to native species (Firn et al, 2010b; Johnston, 1989; Muyt, 2001; Roberts et al, 2021), supporting literature to date has been equivocal (Firn, 2009; Firn et al, 2010a). In some regions across Australia, China and the United States of America, it is a valuable pasture species when intensive management is regularly applied (Firn, 2009; Ngoy and Shebitz, 2019; Zhu, 2006).…”

“…Such management includes rotational grazing in combination with added soil fertility (Firn et al, 2010a; Leigh and Davidson, 1968) and large‐scale burning (Archibald et al, 2005) which aims to prevent mature unpalatable biomass from developing (Firn, 2009). In contrast, when management is not regularly applied E. curvula can spread unchecked and begin to dominate ecosystems (Coutts et al, 2013), which can be mainly attributed to its quick seed germination (Roberts et al, 2021) and mass production of thousands of small seeds (0.3 to 0.7 mm) (Csurhes et al, 2016). Consequently, such actions have led to the species readily escaping regions where it was deliberately planted and has now become an invasive weed in several countries, including Australia (Firn et al, 2018), Chile (EPPO International, 2020; Holm et al, 1991), New Zealand (EPPO International, 2020; Randall, 2002) and the United States of America (Barkworth et al, 2003; EPPO International, 2020).…”