Determining the Optimal Sowing Density for a Mixture of Native Plants Used to Revegetate Degraded Ecosystems

Abstract

No standardized, objective methodology exists for optimizing seeding rates when establishing herbaceous plant cover for pastures, hay fields, ecological restoration, or other revegetation activities. Seeding densities, fertilizer use, season of seeding, and the interaction of these treatments were tested using native plants on degraded sites in northern British Columbia, Canada. A mixture of 20% Achillea millefolium, 20% Carex aenea, 20% Elymus glaucus, 20% Festuca occidentalis, 16% Geum macrophyllum, and 4% Lupinus polyphyllus seed was applied at 0, 375, 750, 1,500, 3,000, and 6,000 pure live seed (PLS) per m 2 in 2.5 3 2.5-m rototilled test plots, established in the fall and spring, with and without fertilizer. There was no significant difference in plant cover of sown species between fall seeding and spring seeding, and few treatment interactions were identified in the first 2 years after sowing. There was no significant difference in cover between seed densities of 3,000 and 6,000 PLS/m 2 in the first year, nor among 1,500, 3,000, and 6,000 PLS/m 2 treatments in the second year. Seed densities as low as 375 PLS/m 2 produced year 2 plant cover equivalent to that observed at 3,000 PLS/m 2 in year 1. Plots sown to seed densities less than or equal to 750 PLS/m 2 generally exhibited an increase (infilling) in plant density from year 1 to year 2, whereas plots sown to seed densities greater than or equal to 1,500 PLS/m 2 generally exhibited a decrease (density-dependent mortality) in plant density. These results imply a most efficient sowing density between 750 and 1,500 PLS/m 2 (corresponding to 190-301 established plants . m 22 after two growing seasons). It is suggested that net changes in plant populations observed over a range of sowing densities are a robust and objective means of determining optimal sowing densities for the establishment of herbaceous perennials.

Influence of Richness and Seeding Density on Invasion Resistance in Experimental Tallgrass Prairie Restorations

“…Although varying levels of seeding density can affect the establishment success and plant density of seeded species (Burton et al 2006, Frances et al 2010, the role of seeding density has received less attention than richness in grassland invasion resistance research. Martin (2006) examined the effect of four seeding density treatments on prairie establishment.…”

Grassland gap effects on Elymus dahuricus Turcz. seedling emergence, survival and growth

“…It potentially improves grassland community structure, productivity and maintains the grassland ecosystem biodiversity and stability (Burton et al, 2006;Robichaud et al, 2000). Seedling emergence and survival are the key development stages after seed germination and pre-conditions for successful establishment.…”

Plant performance on anthroposols at Huckleberry Mine, Houston, British Columbia.

“…Burton et al (2006) point out that low seeding densities will not fully occupy the growing space available and high densities may result in intense competition that inhibit growth and 22 productivity of individual plants. The study by Burton et al (2006) suggests an optimal density between 750 -1500 PLS (pure live seed) m '2 for revegetation efforts on disturbed soils in west-central BC. When considering seed mixes that incorporate species with different life histories (e.g., grasses and shrubs), other factors must be taken into consideration as well.…”

“…In total, seven seeding treatments were applied to all 12 test plots initiated on the minesite (Table 2) Treatments were applied to all subplots at a standardized sowing density o f 750 PLS m '2 which was chosen based on optimal sowing densities recommended as the result o f a previous study (Burton et al 2006). The amount o f seed to weigh out in order to obtain the desired PLS was calculated by adjusting the bulk seed lot weights on the basis o f their germination and purity values (Table 2).…”

“…Research testing the effects of fertilizer and sowing rate on seed emergence and seedling densities for similar grass and legume species was completed by Burton et al (2006) at degraded sites in northern BC. For all sowing densities tested, percent emergence was shown to be significantly higher on fertilized compared to non-fertilized soils.…”