Treesearch

In contrast to other ants in the genus Monomorium that produce cyclic amines, extracts of Monomorium floricola contain (Z)-7-tetradecenylamine (1) and (Z)-9-tetradecenylamine (2). The structures of these compounds were established from their spectral data and by comparison with synthetic 2.

A number of 15-carbon alkaloids have been identified in venoma extracts of four Puerto Rican species of ants in the genus Solenopsis (Diplorhoptrum). Workers of a species from El Verde produced the cis and trans isomers of 2-methyl-6-nonylpiperidine with the latter isomer predominating. The same compounds were identified in queens of a species from Rio Grande, hut in this species no alkaloids were detected in worker extracts. Workers of a Diplorhoptrum species collected on Mona Island produced primarily a trans-2-methyl-6-(Z-4-nonenyl)piperidine, 3, with smaller amounts of the cis isomer,...

This paper provides an overview of agricultural and forestry development in the Amazon basin, and presents and discusses the main land use systems in evidence today in that region. These are logging, shifting-cultivation and ranching. The issue of sustainability is addressed, and current Amazonian land use is interpreted in light of ecological impacts and long-run viability. Also considered are the ecological notions of criticality, endangerment, impoverishment and resilience. After addressing the threats of land use encroachment to the forest resource base, the paper identifies sufficient...

we compared forest structure over a 12 yr period. 1982-1994 that include measurements before and after a servere hurricaine in two forests: a 64 yr old swietenia macrophylla tree plantantion and a paired natural forest of similar age in a subtropical wet forests

We compared patterns of earthworms abundance and species composition in tree plantation and secondary forest of Puerto Rico. Tree plantations included pine (Pinus caribea Morelet) and mahogany (Swietenia macrophylla King) established in the 1930's; 1960's; and 1970's; secondary forests were naturally regenerated in areas adjacent to these plantations. We found that (1) earthworm density and fresh weight in the secondary forests were twice those in either of the tree plantations, and didn't differ between the plantations, and (2) the exotic earthworm species, Pontoscolex corethrurus Muller,...

This paper addresses the relationship between property regimes and land degradation outcomes, in the context of peasant agriculture. We consider explicitly whether private property provides for superior soil resource conservation, as compared to common property and open access. To assess this we implement optimization algorithms on a supercomputer to address resource decision-making of individual households. We find that conditions exist under which private property does not lead to the best environmental outcome. Access to farming technology and off-farm employment opportunities are key...

This paper presents a theoretical discussion of processes linking land use decisions and land cover outcomes at household level, with an emphasis on small proceduers. Evidence from the literature substantiating the existence of domestic cycle phenomena is brought forward and interpreted for the Brazilian case. Also considered are the relative disposition of production factors in the frontier development process, implications for the exercise of political power, and relationships between land concentration and ecological change. The paper concludes with a discussion of traditional land use...