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

Abstract

Abstract 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 analyse 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, Victoria; Tenterfield, New South Wales; and Midvale, Western Australia. 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, whilst Tenterfield (35% vs. 98.6%) and Midvale (32% vs. 91%) were reduced at ≤-0.6 MPa, compared to the mean of all other osmotic potentials. Radiant heat at 100 C significantly reduced and slowed germination compared to 40 C for Tenterfield (62% vs. 100%), Shepparton (15% vs. 89%) and Midvale (41% vs. 100%); whilst Maffra (75% vs. 86%) had consistent germination. For the effect of burial depth and duration (longevity), there was no significant difference across the fourteen-month period, however, the 0 cm burial depth had a significantly lower final germination percentage compared to depths of 3, 5 and 10 cm (24% vs. 55%). Although each trial was conducted independently, their results can be used to help identify efficient control measures to reduce infesting populations. Such measures recommended 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.