Germination stimulation of weed species by smoke.

Abstract

AbstractA study was conducted to determine the effect of smoke water upon the germination of a wide range of native and introduced weedy species under laboratory conditions, and to investigate the effect of aerosol smoke as a possible tool for the regeneration of a degraded grassland community containing native and introduced weedy species. All the monocotyledonous species tested either germinated well in water (non-dormant, e.g. Bromus diandrus) or were strongly stimulated by smoke water (eight species). The dicotyledonous species were either strong stimulated (e.g. Malva neglecta), moderately stimulated (three species), slightly stimulated (seven species), unaffected (eight species) or inhibited (Lamium purpureum). When smoke-water solutions prepared from four different organic sources were tested on Avena fatua and Polygonum persicaria, three solutions (10% Seed Starter, Regen 2000 and a solution from wheat straw combustion) actively promoted the germination of both species, while the fourth (charred wood solution) was only active on A. fatua. All solutions inhibited germination at the highest concentration. There were distinctive points of entry throughout the seed coat length. The total germinable soil seed bank varied between 20 396 seeds/m2 (control) and 25 124 seeds/m2 (smoke-60 treatment). Introduced weed Parthenium hysterophorus was the most abundant species (79-88% of the seed bank, depending on treatment). Grasses were also common (9-17% of the total) in the seed bank, particularly Cenchrus ciliaris, which represented majority of the germinable grass seed bank. More Parthenium hysterophorus seeds germinated from the two smoke treatments than the control. A significant seedling production increase was observed in the total number of seeds from all other species germinating after the two smoke treatments. The smoke-60 treatment produced significantly more seedlings than the control and smoke-10 treatments.