Seed longevity and germination in response to changing drought and heat conditions on four populations of the invasive weed African lovegrass (Eragrostis curvula)

African lovegrass [Eragrostis curvula (Schrad.) Nees] is an invasive weed that is threatening biodiversity around the world and will continue to do so unless its efficient management is achieved. Consequently, laboratory and field-based experiments were performed to analyze several measures of germination to determine the effect of drought stress, radiant heat stress, and burial depth and duration (longevity) on E. curvula seeds. This study investigated seeds from four spatially varied populations across Australia: Maffra and Shepparton, VIC; Tenterfield, NSW; and Midvale, WA. Results showed that increasing drought stress reduced and slowed germination for all populations. Maffra (24% vs. 83%) and Shepparton (41% vs. 74%) were reduced at the osmotic potential of <=-0.4 MPa, while Tenterfield (35% vs. 98.6%) and Midvale (32% vs. 91%) were reduced at <=-0.6 MPa, compared with the mean of all other osmotic potentials. Radiant heat at 100 C significantly reduced and slowed germination compared with 40 C for Tenterfield (62% vs. 100%), Shepparton (15% vs. 89%), and Midvale (41% vs. 100%), while Maffra (75% vs. 86%) had consistent germination. For the effect of burial depth and duration (longevity), there was no significant difference across the 14-mo period; however, the 0-cm burial depth had a significantly lower final germination percentage compared with depths of 3, 5, and 10 cm (24% vs. 55%). Although each trial was conducted independently, the results can be used to help identify efficient control measures to reduce infesting populations. Recommended measures include using soil moisture monitoring to detect which conditions will promote germination, as germination is encouraged when the osmotic potential is >-0.6 MPa; exposing seeds to radiant heat (>100 C) using methods such as prescribed burning; and limiting soil disturbance over time to reduce seed establishment.

Automated summary

African lovegrass is an invasive weed that threatens biodiversity globally, with germination affected by drought stress, radiant heat stress, and burial depth and longevity. Different populations showed varied responses to these stressors, highlighting the importance of understanding the factors influencing germination in managing infestations.