As Above, So Below: Why Forest Understories Deserve the Spotlight
- Sabrina Dookie
- May 18
- 5 min read
Written by Sabrina Dookie
I have always been an ardent admirer of forest canopies. As I walk through the forests in my homeland, Guyana, I am always in awe of the serene beauty they provide. From the filtered light to the leaves rustling when the winds pay a visit, and even to the mixture of scents that surround me. I am reminded of the keen sense of life and balance that these forests uphold.
As I ponder upon this balance in my quiet moments, I am reminded of the old phrase “as above, so below.” It turns out this phrase is built into the lens in which we observe forests, as the forest itself is not just a roof. It is a whole living mirror – with roots deep within the earth – searching, finding, anchoring. I asked myself: “If this is a living mirror, what have I been failing to see in the reflection?” . The answer to my question was lying at the bottom of my feet, literally. I looked down. And I stayed there.
We plant trees to restore and diversify forests, but are we really building forests if we overlook what lies beneath the canopy? Turns out that my fellow scientists and ecologists have been studying the “as above, so below” theory for years by mirroring the importance of forest understory for the maintenance of biodiversity. So, what’s the story about the understory?
Below drives above: how understory diversity drives forest biomass
Understory vegetation plays a critical but underappreciated role in forest ecosystems, serving as a cornerstone for overall ecological stability. The phrase “as above, so below” isn’t just poetic, it is actually measurable. For example, Chen et al. (2025) highlighted that shrub species richness was as important as tree species richness in promoting tree and total woody biomass [1]. This provides evidence that understory diversity can significantly increase forest productivity and should be considered in forest restoration to promote ecosystem functioning.
The resource economy of the forest floor
This looking glass goes both ways as both layers play an intricate role in shaping each other. The understory may seem quiet, but it is never still. Beneath the canopy, it is constantly working—holding the soil in place, slowing the escape of water, and returning life to the forest through the steady fall and decay of leaves. In this layered world, nothing is separate. The understory becomes a bridge—linking earth to canopy, process to pattern, and survival to renewal.
Many studies report a bi-directional relationship where the forest overstory and understory act as a feedback loop. While the overstory controls resources such as light, the understory actively shapes overstory development through belowground networks and resources, competition, and regeneration ‘filtering’ [2]. Additionally, understory vegetation regulates aboveground biomass and carbon dynamics while fostering beneficial soil microbial relationships that enhance nutrient availability [3]. It creates shelter in the smallest spaces, where insects move, where seedlings begin, and where unseen communities in the soil quietly sustain what grows above.
Reading the understory: what the forest floor tells us about climate change
What is interesting, and at times worrisome, is the fact that the understories of many forests are already reacting to the same environmental pressures that the canopies face. This tells us that this mirror is constantly shifting with environmental changes through a dynamic interplay of microclimate buffering and resource competition.
For instance, in Canadian forests, the number and type of different plants which make up the forest understory is usually related to biomass distribution. As such, any changes to the species composition or density of the understory can cause diversity shifts. This may be due to changes in resource availability which may shape the composition and dominance of understory plant species. This ultimately reshapes how the entire forest may function [4]!
China’s forests show us another piece of the puzzle: the tree species present and the grass layer coverage work together to buffer functional traits against extreme heat. Thus, healthy understories may enhance forest resilience to extreme heat events. This optimal understory coverage may be implemented in forest management to improve ecosystem stability and functional diversity in forests facing increasing temperature extremes [5].
Why does this matter for forest management globally?
“As above, so below” should be made into a practical rule and only works if you can see on both sides. We are in an era where the importance of forest conservation and restoration is constantly encouraged worldwide. We are staring hard at the reflection we all want to see – the canopy, the trees, the hectares planted. We count them, we fund them, we celebrate them. However, if we don’t turn around and look at the other side of the looking glass – the understory – we may risk building forests which look good in the reflection without being functional as these forests may lose resilience over time.
Many restoration policies and funding frameworks often overlooking the recovery of understory structure and diversity. If we are to build truly resilient forests, policy and practice must evolve to recognise and monitor the full ecological system from the forest floor to the canopy rather than just what is most visible above. The evidence is crystal clear. The presence of understories in forests drives diversity, productivity, and functionality. Therefore, they should not be neglected in planning and restoration efforts. It is time for us to flip the mirror around. If we want resilient forests, we cannot take the one-sided approach.
Because the below isn’t just reflecting the above, it is holding it up against the test of time.
References
[1] Chen, C., Yan, G., Schmid, B., Li, Y., Bongers, F. J., Bruelheide, H., Huang, Y., Li, S., von Oheimb, G., Tang, T., Verheyen, K., Yang, B., Ma, K., & Liu, X. (2025). Understory shrub diversity: equally vital as overstory tree diversity to promote forest productivity. National Science Review. https://doi.org/10.1093/nsr/nwaf093
[2] Balandier, P., Mårell, A., Prévosto, B., & Vincenot, L. (2022). Tamm review: Forest understorey and overstorey interactions: So much more than just light interception by trees. Forest Ecology and Management, 526, 120584. https://doi.org/10.1016/j.foreco.2022.120584
[3] Haritika, N. A. K. (2025). The underestimated role of understory vegetation dynamics for forest ecosystem resilience: a review. Plant Ecology. https://doi.org/10.1007/s11258-025-01529-7
[4] Chen, X., Reich, P. B., Chen, X., Hisano, M., Taylor, A. R., Li, D., & Chang, S. X. (2025). Environmental change shapes understory plant diversity and dominance in boreal forests. Nature Communications, 16(1). https://doi.org/10.1038/s41467-025-65633-y
[5] Wang, D., Chen, H., & Yang, Y. (2026). Forest layer structure and functional trait heat-tolerance: The critical role of grass coverage in subtropical forest to extreme heat events. Forest Ecology and Management, 601, 123359. https://doi.org/10.1016/j.foreco.2025.123359
About the author
Dr. Sabrina Dookie is a lecturer and mangrove ecologist attached to the University of Guyana, Turkeyen Campus (Department of Biology). Her research interests include mangrove restoration and dynamics, microbial functionality in mangroves, ecophysiological adaptations of mangroves in stressed environments, coastal and marine life management, hydroperiod and sedimentation dynamics, sustainable forestry management, and traditional ecological knowledge and its applications.
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