Using Native Roots and Microbes for Local Landscapes
Posted on Sep. 1, 2023 / Native Species / Subscribe 0
By: Barry Solomon & Sonny Gamponia
The traditional Hawaiian system of land management known as ahupua’a was based on the location of streams, but also was a geologic, climatic, and socioeconomic subdivision of land to meet native people’s needs. Each ahupua’a was divided into a lowland cultivated area, and an upland forested area. Ahupua’as were subdivided into smaller sections called ‘ili and kuleana. Sustainable land use and fishing practices were enforced by the konohiki (headmen or administrators of the land divisions) and kahuna (priests). The ahupua’a system worked well until the early 1800s. At that time, the use of fire for clearing forests for agriculture was already widely practiced. Moreover, the precious and fragrant sandalwood forests became deforested by 1825, adversely affecting hydrological regimes that supported fertile valleys, and large-scale sugarcane monocultures were established. The “Great Māhele” land redistribution was proposed by King Kamehameha III in 1848, which was intended to provide secure land titles to native Hawaiians but instead resulted in many people losing land rights. The Alien Land Ownership Act approved in 1850 allowed foreigners to formally hold land titles. While the full history is much more complex and nuanced, suffice it to say that what followed was almost 200 years of significant land use change, land and soil degradation, and the introduction of numerous invasive species of plants and animals.
Tropical lowland shrublands cover around 1,500 km2 on the leeward lowlands of the main Hawaiian Islands. They are one of four traditionally recognized ecosystem regions (ecoregions) in Hawai’i, along with tropical high shrubland, tropical moist forest, and tropical dry forest. An ecoregion is a classification system based on the major macroclimatic conditions where the ecosystems found in the region are usually similar, covering large areas of land and or water. Tropical lowland shrublands contain habitats of tropical grasslands and savannas, as well as shrublands. The Nature Conservancy of Hawai’i has designated a broader Hawaiian High Islands Ecoregion, with tropical grasslands, savannas & shrublands habitats.
In Hawai’i in general and Maui in particular, among these three habitats, the savanna makes the most sense as a target for ecosystem recovery in tropical lowland shrublands. Invasive and wildfire-prone grasses such as guinea, napier, and buffelgrass are widespread, covering around one-fourth of Hawai’i’s lands. However, because Hawai’i lacks large animal populations to eat them, and these areas lack sufficient rainfall to support extensive tree cover for shrublands, long drought cycles followed by pronounced rainfall allowed the invasive grasses to dominate the landscape.
Maui has undergone significant land use changes. The leeward coast with its hot semi-arid climate and average annual rainfall of around 10 inches limits the vegetation to grasses and thorny bushes. The closing of four sugar mills and a pineapple cannery in the last 50 years shifted land use from dryland agriculture to built-up areas for hotels, housing development, and infrastructure. Driving from Lahaina to Kihei, one can see how the invasive buffelgrass and kiawe can resemble an African savanna where wildfires have become an annual occurrence. Unfortunately, the predominance of these non-native grasses was a critical factor behind the catastrophic wildfire that destroyed much of Lahaina in August 2023.
These alien species depleted the environment of native pollinators and degraded the soil. The following list of native plants are historically known to survive in a tropical savanna climate. They can be used to create a native plant community on any scale from a small backyard garden to acres of public lands.
Figure 1. The USGS online document offers the best resource for where native plants once grew on the main Hawaiian Islands. T
Soil biologist Dr. Elaine Ingham, in her YouTube masterclasses on restoring soil, claims you can predict the biology of the soil by observing the vegetation. Bare soil and weeds have scarce bacterial microbes and no fungi, whereas shrublands and forests are dominated by fungi. As the landscape gradually transforms from a grassland to a shrubland, the bacteria population increases, and fungi begin to appear. The bacteria and fungi feeding on living roots become the foundation of a soil food web, attracting protozoa, nematodes, millipedes, centipedes, earthworms, and insect larvae, which helps decompose organic material and hold moisture in the soil.
Figure 2. The ratio of fungi to bacteria increases as the landscape matures.
Research offers compelling evidence of bacteria entering root tips growth at the tips and releasing nutrients within the root. As the roots get longer, fungi feed on the woodier fiber further up the root system. In substantial numbers, these fungal hyphae create networks that benefit the resilience of a diverse plant community.
The book Teaming with Microbes by Jeff Lowenfels and Wayne Lewis offers an easy and inexpensive method of collecting and multiplying microbes by brewing aerated compost tea. This liquid can play an important part in a strategy for habitat restoration and backyard landscaping.
Figure 3. One (1). Aerated compost tea with microbes can be applied to containers of foundational roots of akulikuli, aki’aki and pa’u o hi’iaka before they are transplanted into soil. Two (2). In a 100 square foot area, 60% would be planted with foundational treated with microbes, 40% with structural low shrubs and feature plants. Filler plants can fill in bare spots as the plant community matures. Four inches of mulch will help retain moisture and suppress weeds. Three (
A fragment of a dryland savanna is mature when living roots system and active photosynthesis continue into the dry season, with an occasional rescue during a drought.
Figure 4. This fragment of a savanna took two growing seasons to fill with living roots and active photosynthesis. Photo by
Each unique native plant community creates a diverse patchwork of ancient habitats that give life back to depleted underground ecosystems. It can attract some of the rarest pollinators in the world such as the Hawaiian yellow-faced bee (Hylaeus spp.), Blackburn’s sphinx moth (Manduca blackburni), the Hawaiian blue butterfly (Udara blackburnii), and the Kamehameha butterfly (Vanessa tameamea). The Hawaiian yellow-faced bee and the Blackburn’s sphinx moth are on the federal endangered species list.
As a backyard garden, it can be considered Hawai’i’s contribution to a Homegrown National Park, a national program for ecological landscaping. The program’s vision is to turn every landscaping project into an act of ecological restoration.
References:
Brewington, L. 2020. Transitions and drivers of land use/land cover change in Hawai’i: a case study on Maui, pp. 89-117 in S.J. Walsh et al., eds. Land Cover and Land Use Change in Islands: Social and Ecological Interactions in the Galapagos Islands. Cham: Springer Nature.
Dance, S. & Selig, K. 2023, August 10. Why Hawaii’s wildfires are so devastating – and ‘predictable. The Washington Post.
Gon, S.M. III & D. Olson. 1999. Focus on Hawaiian biodiversity and ecoregions, pp. 147-150 in Ricketts, T.H., E. Dinerstein, D.M. Olson, C.J. et al., eds. Terrestrial Ecoregions of North America: A Conservation Assessment. Washington, D.C.: Island Press, 485 pp.
Ingham, E. 2022. Science of returning life to the soil.
Lowenfels, J. & Lewis, W. 2010. Teaming with Microbes: The Organic Gardener’s Guide to the Soil Food Web, rev. ed. Portland & London: Timber Press.
Rainier, T. & West, C. 2015. Planting in a Post-Wild World. Portland: Timber Press, pp. 69-93.
Sheldrake, M. 2020. Entangled Life: How Fungi Make Our Worlds, Change Our Minds and Shape Our Futures. New York: Random House.
Siler, J.F. 2012. Lost Kingdom: Hawaii’s Last Queen, the Sugar Kings, and America’s First Imperial Adventure. New York: Grove Press.
Solomon B. & Gamponia, S. 2022. Restoration of fertility to dryland soils with native plants. Hawaii Landscape 68: 5-6.
Solomon B. & Gamponia, S. 2023. Restoring soil fertility to degraded soils with native plants and microbes. Hawaii Landscape, in press.
Tallamy, D. No date. Homegrown National Park. https://homegrownnationalpark.org/
Wessendorf, C. 2022, November 11. Wildfires on the “Hawaii Savanna”. Hawaii Business Magazine, https://www.hawaiibusiness.com/wildfires-hawaii-invasive-plants-environmental-community-action/
White, J. May 20, 2021. Bacteria in Plant Cells: Consequences for Regenerative Crops. https://youtu.be/YHjBqjss1Fg
Barry Solomon is a Professor Emeritus of Geography and Environmental Policy at Michigan Technological University and has volunteered at Kealia Pond National Wildlife Refuge.
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