Action: Sow tree seeds after wildfire
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- Three studies (including one replicated, randomized, controlled study) in the USA examined the effect of sowing herbaceous plant seeds in burnt forest areas. One found it decreased the number and cover of native species and one found it decreased the density of tree seedlings. All three found no effect of seeding on total plant cover or species richness.
One of the ways to restore trees community after wild is by direct seeding of new trees. This action can also affect the abundance of other plant species and consequently the composition of the whole forest.
Supporting evidence from individual studies
A controlled study in 1994-1996 in temperate coniferous forest in Washington State, USA (Schoennagel & Waller 1999) found that spreading seeds in burnt forest areas decreased the number and cover of native species. The number of native plants species (unseeded: 17; seeded: 15/m2) and their cover (unseeded: 41%; seeded: 21%) were lower in seeded plots. Total plant cover was similar between treatments (unseeded: 41%; seeded: 48%). Thirty-two plots (15 × 15 m) were established in each control (unseeded) and seeded area (seeded in September 1994 with seed mix containing 80% annual grass, 15%, short-lived perennial species and 5% nitrogen-fixing legumes). Both areas (7 ha) burned in July 1994. Data were collected two years after seeding in eight quadrats (1 m2) in each plot.
A replicated, randomized, controlled study in 2003-2005 in temperate coniferous forest in Washington State, USA (Dodson & Peterson 2009) found no effect of spreading seeds in burnt forest areas on total plant cover. Total plant cover was approximately 55% under both treatments. Seeded species cover was higher in seeded (8%) than in unseeded plots (1.5%). In 2002-2003, seeding (a mixture of perennial graminoids and forbs) and control treatments were randomly assigned to 8-16 plots (6×8 m) established at each of four sites in an area that was burnt by wildfire in summer 2002. Plant cover was measured in summer 2005.
A replicated, controlled study in 2004-2006 in temperate mixed forest in Nevada, USA (Waitman, Draper & Esque 2009) found that spreading seeds of a sterile wheat-rye hybrid (triticale) in burnt forest area decreased the density of tree seedlings, but did not affect total species richness or cover of perennial plants. Numbers of tree seedlings was lower in seeded (14/m2) than unseeded plots (65/m2). Total number of species (seeded: 17; unseeded: 18/100 m2 plot) and total cover of perennial plants (seeded: 24%; unseeded: 28%) were similar between treatments. Data were collected in 2006 in six pairs of seeded (seeded with triticale at ~92 seeds/m2 in November 2004) and control (unseeded) plots (100 m2). Sites were in an area that was burnt by wildfire in July 2004.
- Schoennagel T.L. & Waller D.M. (1999) Understory responses to fire and artificial seeding in an eastern Cascades Abies grandis forest, USA. Canadian Journal of Forest Research, 29, 1393-1401
- Dodson E.K. & Peterson D.W. (2009) Seeding and fertilization effects on plant cover and community recovery following wildfire in the Eastern Cascade Mountains, USA. Forest Ecology and Management, 258, 1586-1593
- Waitman B.A., Draper T.M. & Esque T.C. (2009) The effects of seeding sterile triticale on a native plant community after wildfire in a pinyon pine–mountain mahogany woodland. International Journal of Wildland Fire, 18, 659-664