Taken from “Soil seed bank resilience after rangeland conversion: implications for restoring abandoned agricultural lands” published in Science of the Total Environment.
A new study examining semi-arid landscapes in northern Iran has found that converting rangeland to agricultural or horticultural land significantly reduces the density and diversity of soil seed banks (SSBs), jeopardizing the potential for natural regeneration in degraded areas. According to research published in Science of the Total Environment, soil seed banks act as an ecological and genetic reserve, supporting vegetation recovery after disturbance. When these reserves are depleted, restoration becomes dependent on active interventions such as reseeding.
Testing the Resilience of Seed Banks
Researchers compared seed bank composition and density in ungrazed rangelands, intensively grazed rangelands, wheat cropland, legume cropland, horticultural land, and abandoned agricultural land. They sampled at two depths, between 0-5 cm and 5-10 cm, and analyzed results across plant functional groups including annuals, perennials, forbs, and grasses. The highest seed densities were found in ungrazed rangelands and legume cropland, particularly in the upper soil layer. Wheat fields, horticultural land, and abandoned agricultural land consistently showed the lowest seed bank densities. Perennials were scarce across all land-use types, with the lowest numbers recorded in horticultural land and grazed rangelands.
Grazing Effects Exceed Cultivation Losses
The study revealed that intensive grazing caused more severe seed bank depletion than conversion to agricultural use. Grazing pressure not only reduced the total number of viable seeds but also diminished diversity, particularly in species that are palatable to livestock. This aligns with global observations that trampling and selective feeding directly reduce the reproductive success of many plants.
Abandonment Does Not Guarantee Recovery
Abandoned agricultural fields, even after several years without cultivation, remained severely depleted of viable seeds. The findings indicate that passive recovery is unlikely in these areas, as seed inputs from surrounding landscapes are insufficient to rebuild seed banks to levels needed for sustainable vegetation reestablishment.
Importance of Soil Depth in Restoration Planning
Across all land uses, the highest densities of seeds were found in the top 5 cm of soil. This reflects the natural deposition of seeds at the soil surface through seed rain. In agricultural fields, plowing disrupted this pattern, redistributing seeds vertically and potentially reducing germination potential. The deeper 5-10-cm layer contained fewer viable seeds, further emphasizing that restoration planning should focus on topsoil.
Implications for the Seed Industry
The depletion of seed banks in both cultivated and grazed systems suggests that natural regeneration cannot be relied upon in many degraded landscapes. For seed industry stakeholders, this highlights the need to develop and supply seed mixes tailored to restoration goals. In regions facing widespread land abandonment, sourcing and distributing native seeds could be a critical service. Restoration practitioners will need to match species selection to local climate, soil conditions, and target plant communities, ensuring that reseeding efforts rebuild both aboveground vegetation and the underlying seed bank.
Active Restoration as a Necessary Strategy
The study concludes that active restoration measures, including reducing grazing intensity in rangelands and sowing native seeds in abandoned lands, are essential for restoring ecosystem function. The findings underscore that protecting existing seed banks in ungrazed rangelands is the most effective way to preserve long-term recovery potential.
State of Practice: Rebuilding Seed Banks in Degraded Lands
- Prioritize Ungrazed Rangeland Protection
Preventing seed bank depletion is the most cost-effective approach. Limiting grazing pressure in high-value rangelands maintains both seed density and diversity, reducing the need for future reseeding. - Assess Soil Seed Bank Viability Before Planning
Use soil sampling to determine seed density and species composition at multiple depths. This guides whether a site can regenerate naturally or requires active intervention. - Targeted Native Reseeding
In abandoned or heavily grazed lands with depleted seed banks, reseeding with native species is essential. Select species adapted to local climate and soil, and include a mix of functional groups (annuals, perennials, forbs, and grasses) to promote ecological stability. - Incorporate Soil Preparation Practices
Where plowing has disrupted vertical seed distribution, minimal-tillage restoration methods help preserve any remaining viable seeds while creating conditions for new seedling establishment. - Combine Seeding with Grazing Management
If grazing is reintroduced post-restoration, use controlled rotational systems to allow vegetation recovery between grazing periods and protect young plants until they reach reproductive maturity. - Source Seed Strategically
Work with regional suppliers to ensure genetic compatibility and adaptability. Locally produced seed often improves establishment rates and long-term resilience.
Source: Erfanzadeh, R., Sabetpour, T., Amini, T., & Török, P. (2025). Soil seed bank resilience after rangeland conversion: implications for restoring abandoned agricultural lands. Science of The Total Environment.www.sciencedirect.com