Two Eucalyptus species-E. saligna Sm. and E. grandis Hill-are especially favored in Hawaii for wood, fiber, and fuel production because of their quick growth and high yields. Their growth is limited, however, on many sites by low levels of available nitrogen. Supplemental nitrogen can be provided by nitrogen-fixing plants, such as legumes. A test was conducted to determine whether planting two leguminous species-Acacia melaxylon R. Br. and Albizia facataria (L.) Fosberg-could increase biomass production. Results after 65 months suggest that Eucalyptus growth can be increased substantially by planting the species in mixture with leguminous trees. Total biomass production was much greater in the mixed species plantations than in the pure Eucalyptus plantation.

The aim of this book is to present, in depth, updated information on soil and microbial processes involved in mixed plantations of Eucalyptus and N2-fixing species, especially Acacia mangium, focusing on Forestry, Soils, Biology, Ecosystem Services and Sustainability. The potential of substituting chemical N fertilizer by a consortium of leguminous species that fix atmospheric nitrogen is an interesting solution for a more sustainable, economically and environmentally sound forest system. Among the main topics, we present reference topics on soil microbiology, as biological nitrogen fixation, the role of mycorrhiza in mixed plantations, bio-indicators of soil quality, and plantgrowth promoting bacteria with biotechnological potential. Here we discuss Ecosystem services and ecological benefits of these systems, the invasive potential of A.mangium, as well as the regulations and perspectives of land use policies for mixed forests and their role in the sustainability of the system.

In a 1964-1967 study on the Challenge Experimental Forest, seedfall was evaluated in 2-, 5-, and 10-acre circular clearcuttings. During the 4 years, 10 seed crops, ranging from light to bumper, were produced by ponderosa pine. white fir, Douglas-fir, and incense cedar. Seedfall ranged from 76 to 40,691 sound seed per acre (188 to 100,547/ha) for a single species in a given year. From 89 to 100 percent of each species' seed fell within an area 1 1/2 times the height of the average dominant tree. Overall, seed distribution was highly variable.