Promoting understory for sustainable forest management

Understory vegetation represents an important part of forests, playing a key role in supporting ecosystem function and services. The understory is where the greatest biodiversity of a forest is found. Understory plants affect forest biogeochemistry by influencing water availability, litter decomposition and nutrient cycling. They also provide a habitat for numerous animal species, including arthropods, birds and mammals. The understory also affects the biomass of soil microbial communities, such as fungi and bacteria. These microbial communities are deeply involved in biogeochemical cycles and form close relationships with plant and tree roots.

From a management standpoint, understory plants compete with newly established tree seedlings, capturing most of the available resources and lowering seedling survival and growth. Both mechanical and chemical competing vegetation control are a critical management component in early forests, before and after the seedling establishment. Once the overstory is well established, maintaining a rich, diverse and native understory is crucial for sustainable forest management.

Resource availability in forest understories is scarce, with trees being the major beneficiaries of nutrients and light. But some silvicultural treatments, such as thinning and prescribed fire, can be beneficial for understory composition and diversity. Thinning manipulates forest canopy structure, allowing light to reach the lower forest layers. The increased light availability will increase soil temperature, and the thinning residuals will be readily decomposed and transformed into nutrients by soil biota. Properly planned thinning can maintain the stability and the structure of a stand while enhancing timber production. Several studies have reported that moderate intensity thinning can improve the understory microhabitat, reduce inter species competition and promote the abundance and diversity of understory species, while increasing the stand in terms of height and diameter.

Similarly, prescribed burns can have a positive effect on understory communities, increasing diversity and stimulating germination, while reducing fuel loadings. Researchers showed that low intensity frequent burns can bring richness by creating open space and reducing competition, promoting the recruitment from the local species pool. Moreover, immediately following the burn, soil pH increases, as well availability of carbon, nitrogen and elemental nutrients to the near-surface soils. These favorable conditions start to decline after six months post burn and plummet after 12 months. A well-timed prescribed burn during the end of dormant season can improve the nutrient availability during the growing season for both over and understory.

In summary, silvicultural management activities increase habitat heterogeneity by improving the light environment, increasing the resource availability and fertility, and influencing understory abundance and diversity. These changes mimic natural disturbance processes by creating diverse microhabitats, allowing species with different requirements to thrive. Adopting ecosystem informed practices can help forest managers to achieve sustainable forest management’s goals.

White flowers on a branch.

Blackberry (Rubus spp.) flower. Blackberries are commonly found in forest understories, and they provide shelter, nesting sites and food for numerous wildlife species.

Bush of wild azalea flowers.

Wild azaleas (Rhododendron canescens) are flowering shrubs commonly found in moist forests and along streams and riverbanks.

Close-up of white and pink wild azalea flower.

Wild azaleas (Rhododendron canescens) display spectacular pinkish-white flowers that bloom in the summer.

Close-up of red Florida anise flower.

Florida anise (Illicium floridanum) is a native evergreen shrub or small tree commonly found along shady stream beds and moist wooded ravines in Louisiana and Florida. Its leaves are aromatic, emitting a pungent anise-like odor when crushed.

6/2/2023 4:21:35 PM
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