Microclimate effect

Martens JRT, Hoeppner JW, Entz MH (2001) Legume cover crops with winter cereals in Southern Manitoba Establishment, productivity, and microclimate effects. Agron J 93 1086-1096... 

Land use changes in the tropics have resulted in a landscape characterized as a mosaic of logged forests, cleared fields, and successional forests. This results in the transformation from extremely fire resistant rainforest ecosystems to anthropogenic landscapes in which fire is a common event (16, 17), Fires occur in disturbed tropical forests because deforestation has a dramatic effect on microclimate. Deforestation results in lower relative humidities, increased wind speeds, and increased air temperatures. In addition, deforestation results in increased quantities of biomass that are susceptible to fire. This biomass may be in the form of forest slash, leaf litter, grasses, lianas or herbaceous species (16, 18). 

The absorption of short-chain weak acids in the rat intestine, as a function of pH, does not appear to conform to the pH partition hypothesis [44]. Similar anomalies were found with weak bases [77]. The apparent pKa values observed in the absorp-tion-pH curve were shifted to higher values for acids and to lower values for bases, compared with the true pKa values. Such deviations could be explained by the effect of an acid layer on the apical side of cells, the so-called acid pH microclimate [44,70,73,76-84],... 

Permeability is a property closely tied to the environment of the epithelial cell surface. There is little point in measuring permeability at pH 1.7, if the microclimate barrier has pH >5 and <8, averaging 6. An in vitro permeability screen based on donor pH 5.0-7.4 and acceptor pH 7.4 seems about right. It will be useful to correct the data for the unstirred water layer effect, using computational methods. 

Precellular solute ionization dictates membrane permeability dependence on mucosal pH. Therefore, lumenal or cellular events that affect mucosal microclimate pH may alter the membrane transport of ionizable solutes. The mucosal microclimate pH is defined by a region in the neighborhood of the mucosal membrane in which pH is lower than in the lumenal fluid. This is the result of proton secretion by the enterocytes, for which outward diffusion is slowed by intestinal mucus. (In fact, mucosal secretion of any ion coupled with mucus-restricted diffusion will provide an ionic microclimate.) Important differences in solute transport between experimental systems may be due to differences in intestinal ions and mucus secretion. It might be anticipated that microclimate pH effects would be less pronounced in epithelial cell culture (devoid of goblet cells) transport studies than in whole intestinal tissue. 

Amsler CD, Neushul M (1989) Chemotactic effects of nutrients on spores of the kelps Macrocystis pyrifera and Pterygophora califomica. Mar Biol 102 557-564 Amsler CD, Neushul M (1990) Nutrient stimulation of spore settlement in the kelps Pterygophora califomica and Macrocystis pyrifera. Mar Biol 107 297-304 Amsler CD, Reed DC, Neushul M (1992) The microclimate inhabited by macroalgal propagules. Br Phycol J 27 253-270... 

Physiological Buffer Systems Recently, a lot of efforts have been made on how to increase the biorelevance of the Caco-2 model [63, 47, 64, 65,105], Historically, the media used for Caco-2 experiments were buffered at pH 7.4 on both sides of the monolayer. The pH in the cellular interstice and blood compartment is known to be 7.4. However, the pH in the upper GI tract under fasted conditions ranges from 5.0 to 6.5, with an acidic microclimate existing just above the epithelial cell layer estimated to be between 5.8 and 6.3 [90], The pH of the apical medium can have a critical effect on the transport of drugs, especially for drugs with a pKa close to 7, or when pH-dependent transporters are involved. 

Haselgrove, L. et al., Canopy microclimate and berry composiiton the effect of bunch exposure on the phenolic composition of Vitis vinifera L cv Shiraz grape berries. Aust. Grape Wine Res. 6, 141, 2000. 

Indirect effects.—Indirect effects are those that do not require a direct interaction between the herbicide and an organism. As an example, herbicides, because they directly influence plant cover, result in modification of animal habitat (food, cover, microclimate) which, in turn, influences carrying capacity for specific wildlife species. As a result of the interrelations within food chains, direct effects on relatively minor species can be transferred indirectly to organisms at higher trophic levels. Other examples of indirect effects are those that result from the alteration of vegetation density and species composition. For instance, severe and prolonged... 

Shenderova, A. (2000),The microclimate in poly(lactide-co-glycolide) microspheres and its effect on the stability of encapsulated substances, Ph.D thesis, The Ohio State University. 

An exhaustive field study by Moulton et al. (2000) (see also Moulton and Berner, 1998) quantified plant effects on weathering in western Iceland. The study area includes several adjacent basaltic areas one of which was barren (covered only by sporadic moss and hchens) and the others populated by birches and conifers. All of the areas have similar slopes and microclimate and do not have either acid rain (a problem in the northeastern USA, Europe, and elsewhere) or hydro-thermal activity. Also, calcium carbonate is absent which, because it weathers rapidly, could confuse the results. 

Species effects on microclimate influence ecosystem processes most strongly in extreme environments. This occurs because ecosystem... 

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