Termites in ecosystems of central Amazonia: species composition, soil properties, and nutrient cycling / by Ilse Lieve Ackerman.

Tese (Ph.D.)- Cornell University, 2006

We investigated how termite species composition differed between primary forest and agroecosystems, and the impact of mound-building termites on soil properties and nutrient cycling in a secondary forest. In Chapter 1, we compared the termite assemblage of a primary forest with that of low- and high-diversity agroforests using a rapid biodiversity assessment protocol. The agroforests maintained the same percentages of termite species across feeding guild and taxonomic classes as primary forest, indicating that agroforests may be able to support the same suite of termite functions as primary forest. The palm-based, low-diversity agroforest hosted a termite assemblage more similar to the primary forest than the high-diversity agroforest, indicating that specific plant attributes may be more important drivers of termite diversity than plant diversity alone. An unusually high percentage of oil-feeding termite species was found in all land uses. In Chapter 2 we investigated chemical, physical, and hydraulic properties of termite mounds in secondary forest to determine the most important constraints on plant establishment. Termite mounds were found at a density of 760 ha-1 in the study site, covering 3% of the area. Root biomass was 50% lower in the surface of these mounds than in the soil surface. The physical strength of the termite mounds (13.5 MPa resistance) and their hydraulic characteristics (higher infiltration rate (16 mm s-1), lower water retention, and lower rates of water absorption) were found to be the most important constraints to plants. In Chapter 3, we looked at the role of termite mounds in carbon and nitrogen storage in a secondary forest site. Termite mounds stored 80% and 20% more carbon and nitrogen per mass soil than the surrounding soils. Carbon mineralizes at the same rate as the control soil, but nitrogen mineralizes 30% more slowly, at 0.14 mg (g N)-1 d-1. Microbial carbon in termite mounds was 50% lower than in control soils, at 0.5 and 1%, respectively. Neither moisture nor physical protection in termite-mound aggregates were constraints to nitrogen mineralization. We inferred that low-quality organic matter used in mound construction (post-digestion) is responsible for the lower rates of nitrogen mineralization.