Accelerated land erosion and subsequent sedimentation on downstream coral reefs is a major environmental stressor in Guam1,2. Sedimentation smothers corals and blocks sunlight which zooxanthellae need to photosynthesize1, and prevents corals from recovering from episodic bleaching events caused by warming sea surface temperatures3. The main source of sedimentation is from the badlands in the savanna watersheds—barren areas of exposed saprolite or volcanic soil that are either continuously eroding or accumulating eroded soil4. Badlands make up approximately 2.45% of southern Guam, yet contribute anywhere from 2.1 to 9.5 tons/ac/yr of soil erosion—more than any other land cover type on Guam 4.
Guam's Current Restoration Efforts
Planting acacia and eucalyptus seedlings is the current method of restoration on Guam implemented by various local and federal governmental agencies4. These non-native species are chosen because of their ability to grow in nutrient-poor soils and to resist fire, are planted in large monoculture stands4. However, the areas more prone to erosion are high in elevation and are far from road access making trekking with seedlings time and labor intensive. Forest managers are interesting in incorporating native species and biodiversity in restoration areas. Alternatives and supplementary methods would benefit restoration efforts.
In 2017, University of Guam (UOG) Center for Island Sustainability and UOG Sea Grant Program established the Guam Restoration of Watersheds (GROW) Initiative to reduce land erosion and resulting sedimentation on coral reefs. The goal of GROW is to test the effectiveness of various vegetative and engineered tools in watershed restoration. The first tool to be tested will be the dispersal of seedballs.
Seed balls—balls of a matrix of moist clay, compost, and seeds—are commonly known as a "guerilla gardening" method5, but have been recently studied as a means of forest restoration6,7. Stabilizing exposed soil via the mass dispersal of seedballs containing seeds of native savanna plant species could be a cost-effective method of watershed restoration. Seed balls can be easily prepared, and then broadcasted by unmanned aerial vehicles (UAVs) or helicopters over target areas.
Other Benefits from this Study
The species in the study currently lack published studies concerning germination, seed viability, or storage capability. The data collected from the species in this study will add valuable information to scientific literature of the native and endemic species of Guam and Micronesia. The data collected can also enhance our understanding of plant succession and vegetative responses to environmental disturbances in Guam and Micronesia.
This project is designed to equip the local community of all ages and backgrounds with the relevant information they need to restore badland areas with seed balls.
Humåtak Watershed Adventures
UOG Sea Grant conducts educational tours called Humåtak Watershed Adventures (HWAs) to highlight the relationship between watershed health, coral reef ecosystems, and human activities. During these HWAs, I explain my research project and make seed balls with the participants. Participants have ranged from school aged children to community leaders.
Guam Seed Ball Manual
A user-friendly manual for native savanna plant species identification, seed collection, and seed ball creation will be available in pamphlet form and online.
This study aims to investigate the potential of using seeds of native savanna species in seed balls as a restoration tool for Guam’s badlands and eroded savanna areas.
The objectives of this study are to determine:
1) if seed broadcast method has an effect on germination
2) if scarification has an effect on germination
3) if the use of fertilizer has an effect on germination or plant growth
4) if there are significant interactions between species, broadcast method, scarification, and use of fertilizer
5) the plant survival rate of successful germinations
The experiment is conducted in natural outdoor conditions in a split-split plot design in 18 raised plots to compare germination success between 96 species-broadcast-treatment combinations, with 6 repetitions. Samples are arranged in a complete random block to reduce any placement effects. The most effective planting methods and the interactions between each of the factors will be analyzed for statistical differences.
The 7 species used in the study are common, native savanna species of Guam that are easy to recognize:
Geniostoma micranthum (720 seeds total)
Glochidion marianum (720 seeds total)
Myrtella bennigseniana (240 seeds total)
Rhynchospora rubra (1440 seeds total)
Scaevola taccada (72 nuts total)
Scleria polycarpa (1440 seeds total)
Timonius nitidus (720 seeds total)
The broadcast methods are: direct broadcast (D), seed balls (SB), and seed ball stored for one week (SBS).
The 4 treatments are combinations of scarification and fertilization. Scarification was done to the seeds with coarse sandpaper or nail clippers. The fertilizers used are: 14-14-14 Osmocote and 0-45-0 Super phosphate in low amounts. The treatments are: scarified and fertilized (SF), scarified and not fertilized (SnF), not scarified and fertilized (nSF), and not scarified and not fertilized (nSnF).
The soil used was collected from a badland patch in southern Guam, and was pasturized to eliminate unintended growth from a possible seed bank.
Compost was locally produced by Ordot Green Waste Facility, and was sifted to 1/4".
Video made by Audrey Meno in 2017, as a part of her tasks as the Micronesian Challenge Young Champion.
Results as of July 20, 2018. Five of seven study species have germinated.
|species||days in study||days to germ||D SF||D SnF||D nSF||D nSnF||SB SF||SB SnF||SB nSF||SB nSnF||SBS SF||SBS SnF||SBS nSF||SBS nSnF||Total|
1. Shelton, A. & Richmond, R.H. 2016. Watershed restoration as a tool for improving coral reef resilience against climate change and other human impacts. Estuarine, Coastal and Shelf Science. 183, 430-437.
2. Van Beukering, P., Haider, W., Longland, M., Cesar, H., Sablan, J., Shjegstad, S., Beardmore, B., Liu, Y., & Garces, G.O. 2007. The economic value of Guam’s coral reefs. Technical Report 116, University of Guam Marine Laboratory, University of Guam, Mangilao.
3. Carilli JE, Norris RD, Black BA, Walsh SM, McField M (2009) Local Stressors Reduce Coral Resilience to Bleaching. PLoS ONE. 4(7): e6324. doi:10.1371/journal.pone.0006324
4. Kottermair, M., Golabi, M., Khosrowpanah, S., & Wen, Y. 2011. Spatio-temporal dynamics of badlands in southern Guam: A case study of selected sites. Technical Report 133, WERI, University of Guam, Mangilao.
5. Seed-Balls.com. (2013). What are Seed Balls? [accessed 2017 September 6]. http://seed-balls.com/what-are-seed-balls
6. Jones, L.C., Schwinning, S., & Esque T.C. 2014. Seedling ecology and restoration of blackbrush (Coleogyne ramosissima) in the Mojave Desert, United States. Restor. Ecol. 22, 692–700.
7. Ortolani M.R., Schirone A., Camillotti G., Schirone B. 2015. Aerial reforestation by seed bombs. In: Ivetid V., Stankovid D. (eds.) Proceedings: International conference Reforestation Challenges. 03-06 June 2015, Belgrade, Serbia. Reforesta. pp. 227-233.
Other Notable Sources
Baskin, C.C. & Baskin, J.M. 1998. “Ecologically meaningful germination studies.” Seeds: Ecology, biogeography, and evolution of dormancy and germination. San Diego, CA: Academic Press.
Doust, S.J., Erskine, P.D., & Lamb, D. 2006. Direct seeding to restore rainforest species: Microsite effects on the early establishment and growth of rainforest tree seedlings on degraded land in the wet tropics of Australia. Forest Ecology and Management. 234: 333–343.
Engel, V.L. & Parrotta, J.A. 2001. An evaluation of direct seeding for reforestation of degraded lands in central São Paulo state, Brazil. Forest Ecology and Management. 152: 169–181.
Fosberg, F.R. 1960. The vegetation of Micronesia. Bulletin of the American Museum of Natural History 119: 1-75.
Kennedy, T.A., Naeem, S., Howe, K.M., Knops, J.M.H., Tilman, D., & Reich, P. 2002. Biodiversity as a barrier to ecological invasion. Nature. 417, 636–638.
Seed-Balls.com. 2014a. Advanced Seed Ball Recipe. [accessed 2017 September 6]. http://seed-balls.com/advanced-seed-ball-recipe
Seed-Balls.com. 2014b. How big are seed balls? [accessed 2017 September 6]. http://seed-balls.com/how-big-are-seed-balls
Seed-Balls.com. 2014c. How many seeds in a seed ball? [accessed 2017 September 6]. http://seed-balls.com/how-many-seeds-in-a-seed-ball
Stone, B.C. 1971. The flora of Guam: a manual for the identification of the vascular plants of the island. Micronesica: 6. University of Guam, Mangilao.