Increasingly research suggests that the level of internal regulation of function in agroecosystems is largely dependent on the level of plant and animal biodiversity present. In agroecosystems, biodiversity performs a variety of ecological services beyond the production of food, including recycling of nutrients, regulation of microclimate and local hydrological processes, suppression of undesirable organisms and detoxification of noxious chemicals. In this paper the role of biodiversity in securing crop protection and soil fertility is explored in detail. It is argued that because biodiversity mediated renewal processes and ecological services are largely biological, their persistence depends upon the maintenance of biological integrity and diversity in agroecosystems. Various options of agroecosystem management and design that enhance functional biodiversity in crop fields are described.

It has recently been proposed that many communities are structured by a hierarchy of interactions in which facilitation by foundation species is of primary importance. We conducted the first explicit experimental test of this hypothesis by investigating the organization of positive interactions on New England cobblestone beaches. In this midintertidal community, wave-generated substrate instability and solar stress largely limit marine organisms to the shelter of cordgrass beds. Cordgrass, which can establish and persist without the aid of other foundation species, facilitates a dense assemblage of inhabitants (e.g., mussels, snails, seaweeds) with roots/rhizomes that stabilize substrate and a dense canopy that baffles waves and provides shade. Within the cordgrass bed community, ribbed mussels further enhance physical conditions and densities of other species (e.g., amphipods, barnacles) by providing crevice space and hard substrate. We conclude that cordgrass bed communities are hierarchically organized: secondary interactions (e.g., facilitation by ribbed mussels) play a key role within an assemblage dependent on primary facilitation by the independently successful foundation species cordgrass. Our results identify emergent indirect positive interactions in the form of facilitation cascades, have broad implications for conservation, and help unify existing models of community organization that were developed without considering the fundamental role of positive interactions.

Objective: The distribution of potential environmental risk factors among patients affected by superficial transitional cell carcinoma of the bladder (TCCB) has been analyzed. Methods: Patients affected by superficial TCCB underwent TUR and early intravesical chemotherapy. Detailed data about age, sex, residence, employment, active and passive cigarette smoking, water resource and hair dye use were centralized. Analysis has been conducted on 474 patients affected by Ta-T1 G1-2 TCCB at medium risk for recurrence. Patients with primary single Ta G1-2, Tis or T1G3 tumors were excluded from the present analysis. Results: Over 80% of the patients lived in urban areas, 22% were employed in industries presumed at risk for bladder cancer, 8% used hair dye and 75% were smokers. Bottled water was the only water resource in 42% of the patients. Employment in industry at risk (p = 0.01) and cigarette smoking (p = 0.04) resulted in being statistically related to tumor multiplicity. Moreover, the period of cigarette smoking was significantly longer in patients with recurrent tumors (p = 0.026). The municipal water supply represented the main water source in never-smokers (p = 0.01) rather than in smokers and in patients harboring T1 rather than Ta tumors (p = 0.03). Conclusions: Employment in industry at risk and cigarette smoking resulted in being related to tumor multiplicity. The length of exposure to cigarette smoking was related to the natural history of the tumor. A drinkable water source emerged as a risk factor in absence of cigarette smoking.

This study indicates that the PP method, although not recommended internationally, is a reliable alternative to MF and MPN.