Microclimate Regulation Research Articles

The ecological role of biodiversity in agroecosystems

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.

Maintenance and regulation of the pH microclimate at the luminal surface of the distal colon of guinea-pig.

1. The fluorescent dye 5-N-hexadecanoyl-aminofluorescein (HAF) was used to study the mechanisms involved in maintaining a relatively constant luminal surface pH (pHs) in the distal colon of the guinea-pig. The fatty acyl chain of the HAF molecule inserts into the apical membrane of epithelial cells. This allows a continuous measurement of the surface pH for several hours. 2. The localization of HAF was confirmed by confocal laser-scanning microscopy and by using monoclonal antibodies against fluorescein. The insertion of HAF into the apical membrane of the colonocytes did not change the transepithelial conductance or the short-circuit current of the epithelium. 3. With the HAF method a pH microclimate was confirmed at the colonic surface. Although the pH of the bulk luminal solution was decreased in bicarbonate-containing solution from 7.4 to 6.4 the pHs changed only in the range 7.54-6.98. 4. In the absence of bicarbonate pHs almost followed changes of bulk luminal pH. In the presence of bicarbonate there was a decrease in pHs after removal of chloride from the luminal side and an increase in pHs after addition of butyrate to the luminal solution. This suggests the involvement of a bicarbonate-anion exchange in bicarbonate secretion: a Cl--HCO3- as well as a short-chain fatty acid--HCO3- exchange. 5. The apical K+-H+-ATPase in the distal colon of guinea-pig has little influence on pHs in the presence of physiological buffer concentrations. 6. Our findings indicate that bicarbonate plays a major role in maintaining the pH microclimate at the colonic surface.

Management of common bean diseases by farmers in the Central African Highlands

Abstract Farmers’ management of bean diseases in the Great Lakes region of Africa was investigated from both phytopathological and anthropological perspectives. Local crop protection strategies were based on microclimate regulation, genetic diversity and sanitation. Microclimate management involved selectively integrating numerous agronomic practices depending on the site and conditions. The strategies included manipulating sowing density and time of sowing, choice of soil, use of varieties, variety and species mixtures for specific conditions, foliage reduction, staking and selective weeding. Decision‐making flexibility was essential to the effectiveness of local microclimate management strategies. Resistant varieties were available in local mixtures and were managed by farmers through intervention and natural selection in the field. A number of sanitation methods were used, such as removal of debris from fields at harvest, but their value by farmers in crop protection was less recognized. Improvements to local plant protection should be possible through the development of technologies which reduce losses in plant density, improve crop resistance to ‘rain’ while maintaining genetic variability and improve seed health, and by educating farmers in the basic principles of plant pathology while ensuring their participation in the development of technologies destined for their agroecosystems. The authors emphasize the importance of developing technologies for fanners which do not decrease existing management flexibility.

Use of Encarsia formosa adults in biological control of Trialeurodes vaporariorum on glasshouse vegetable crops

In Poland, where possibilities for complete microclimate regulation in glasshouses are limited and there is a relatively low degree of automation and computerization, satisfactory biological control of Trialeurodes vaporariorum with Encarsia formosa depends on precise and uniform release of the parasite in the glasshouse, as well as on rapid reaction to increasing pest numbers. This can be achieved by a method, developed in Poland and presented here, of using adults of E. formosa in specially prepared capsules. This paper reports on the principles for using E. formosa in capsules, and on the numbers and frequency of release of the parasite which are appropriate for different crops.