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Impact of Human Frugivory on the Population Ecology of a Set of Congeneric Medicinal Plant Species in the Western Ghats, India.EPA Grant Number: F5F21960
Title: Impact of Human Frugivory on the Population Ecology of a Set of Congeneric Medicinal Plant Species in the Western Ghats, India.
Investigators: Weiss, Laura
Institution: University of Hawaii at Manoa
EPA Project Officer: Just, Theodore J.
Project Period: August 22, 2005 through August 21, 2007
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
The structure and composition of a tropical forest is shaped by the differential capacity of its trees to survive, grow, reproduce, and disperse. When humans heavily harvest fruit from a forest, they act as seed predators, potentially impacting or even replacing seed dispersers as well as other predators. This has implications for population dynamics of not only the plant species harvested, but also of the species’ frugivores (dispersers and predators), and of species that provide alternative food sources.
India ’s management of its forests as a combination of extractive and non-extractive reserves affords an ideal opportunity to study this issue, particularly in the Western Ghats mountain range, one of the 25 global hotspots of biodiversity. The Soligas indigenous people harvest non-timber forest products in two of four forest reserves of this area which share similar ecological conditions, flora, and fauna. One valuable species heavily harvested and sold by the Soligas for use in Ayurvedic medicine, Terminalia chebula (Combretaceae), has a congeneric partner, T. bellifera, that shares the same lifecycle characteristics and frugivores but is not subject to the same intensity of human harvest. Both species, known locally as “myrobolan,” occur widely in all four of the above proposed study sites. They have single-seeded fruits eaten and dispersed by native ungulate species and possibly bats, and seeds are heavily predated by rodents. I will explore the following research questions:
- What is the ecological impact of heavy human harvesting of T. chebula fruits on populations of T. chebula and T. bellifera?
- What alternative harvesting techniques are employed?
- Is the current rate of harvest sustainable?
- Are changes in frugivore populations likely to have an impact on the long-term seed population of either Terminalia species?
Transects will be established in two forest reserves where there is heavy harvesting of T. chebula and two in which there is no harvesting of either Terminalia species. W ithin transects, all individuals of the two Terminalia species will be tagged, mapped, and regularly monitored for annual rates of reproduction and recruitment. The Soligas traditional ecological knowledge and harvesting pattern will be explored through interviews, direct observations, censusing the number of harvesters, harvesting rates, and techniques, and quantifying the market for the fruits. Fruit/seed predation by animals will be monitored through direct observation, filming, and analyses of animal pellets and digested seeds. A controlled germination experiment will evaluate the ability of seeds to germinate under a variety of conditions, including post-digestion from ungulates and bats. Basic environmental conditions will be monitored over the study period and compared to the long-term averages for the region. A quantitative model will be used to determine if and how differences in harvest techniques, harvest rates, and frugivory rates affect population growth.
I expect to identify sustainable harvest rates and techniques for T. chebula, and to inform the decision of whether or not harvest should be allowed in other forest reserves of India. Findings of this research will be shared with management agencies, disseminated in the Soligas language at community meetings, as well as published and presented at international meetings in order to inform a wider audience about impacts of non-timber forest product harvesting and the role of traditional ecological knowledge.