The steeplands of Central America are being systematically deforested as population pressure dictates a need for an increase in subsistence agriculture. The combined effect of high rainfall and lack of conservation measures leads to high levels of soil erosion. In order to assess sustainable soil conservation technology, research was conducted in the mountainous agricultural area of Guinope, Honduras. Runoff and soil loss from a number of plots that were established on various ground slopes and under different land uses were measured during the 1994 and 1995 seasons. Natural and fired woodland were assessed to provide an indication of both baseline conditions and those associated with the initial stage of deforestation. Against these, the impacts of agriculture involving maize - Zea mays L.- with and without two leguminous cover crops - Mucuna sp. and Canavalia ensiformis (l)DC. - were assessed on ground sloping at 6, 11 and 18 degrees. Seasonal runoff under natural pine forest is shown to be 10 % that of maize agriculture on similar slopes while fired forest is 49 %. Of the cover crops, after a second year Mucuna is the most protective when intercropped with maize, giving runoff on 18 degree slopes which is 47 % that of maize grown by itself, compared with 51 % for Canavalia. On 11 degree slopes, Canavalia offers greater protection but here the difference between the two cover crops is marginal Soil erosion can be shown to be a function of ground slope. For maize grown by itself, soil losses from 6 and 11degree slopes are 13 % and 23 % those from 18 degree slopes. On two years of research Canavalia is more stable in giving protection. On 18 degree slopes, soil loss where Mucuna is intercropped is 43 % that under maize alone while for Canavalia it is 47 %. By comparison, the natural forest loses much less than 1 % that of the maize fields. This study clearly shows the vulnerability of steep lands that are being clear-felled. It also demonstrates the considerable advantages of using extensive green soil conservation technology in reducing soil erosion and prolonging the usefulness of land. This extends to relieving the pressure on virgin forest in a situation where population growth discourages long periods fallow as part of a form of shifting cultivation.

Global changes resulting from human activities, including elevated levels of greenhouse gases, enrichment of nitrogen and land use changes, have led to substantial losses in biodiversity of macroscopic organisms, such as plants and animals, but whether these changes will have similar impacts on microscopic organisms, such as bacteria and fungi, is less clear. I examined the impact of three of these global changes, including elevated carbon dioxide, increased soil nitrogen availability and large-scale deforestation, on the biodiversity of soil fungi in three separate ecosystems. The responses of fungi to global changes were variable across ecosystems and the experimental system and were not readily predicted by observed changes in the plant community. However, subtle shifts in the community composition of fungi were observed in response to all global changes. Whether these shifts will impact the ecosystem function of these systems in unclear, but previous studies suggest that even small changes in community dynamics can have large effects on important processes, such as nitrogen cycling and carbon storage. These findings indicate that soil fungi do respond to global changes, but additional research must be undertaken to examine the effects of these shifts. / 10000-01-01

No description available.

No description available.

No description available.

Thesis (doctoral)--Universität Göttingen, 2004. / Includes bibliographical references (leaves 106-117). Also available in PDF format.

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis (Ph. D.)--Georgia State University, 2008. / Title from file title page. Paul J. Ferraro, committee chair ; Alexander Pfaff, Gary T. Henry, Gregory B. Lewis, Douglas S. Noonan, committee members. Electronic text (99 p.) : digital, PDF file. Description based on contents viewed October 28, 2009. Includes bibliographical references (p. 91-98).

Thesis (M.S.) in Forest Resources--University of Maine, 2008. / Includes vita. Includes bibliographical references (leaves 140-152).

Thesis (Ph. D.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 99-107). Also available on the World Wide Web.