Microclimate describes the climatic conditions near the ground, where plants and animals are found (Rosenberg et al. 1983), and differs from macroclimate, which describes climatic conditions several meters above the ground. The greatest diurnal changes in temperature are found at the microclimatic scale, thus microclimate is important for understanding organismal processes. Besides temperature, other climatic factors such as relative humidity and windspeed change rapidly within the first few centimetres of the surface, and large amounts of energy are exchanged at the surface to balance inputs of solar radiation. The balance of energy at the surface can be described as:
where Rn is the net radiation at the surface, considering all incoming and outgoing sources, S is the total soil heat flux, H is sensible heat flux from between the air and the surface, LE is latent heat flux between the surface and the air through evaporation and condensation, PS is energetic conversion of light to carbohydrates by plants and M represents miscellaneous processes that are otherwise unaccounted for.
Plant physiological processes such as energy exchange, photosynthetic CO2 assimilation, and water loss through transpiration are all strongly tied to the aerial environment. Much of the work in plant physiology has gone into determining response functions of such physiological processes to microclimatic parameters. Examples include photosynthetic temperature (e.g. See protocol Leaf cooling curves: measuring leaf temperature in sunlight ) and light response curves (e.g. See protocol Temperature response of photosynthesis using a Li-Cor 6400 ), which describe a function that can be modelled to predict the rate of a process given microclimatic conditions.
Models are therefore powerful tools for understanding and predicting physiological responses of plants to microclimatic conditions (Jones 1992). In this way, models are able to assist in simplifying the responses of physiological processes to microclimate so that they may be predicted with minimal inputs and allow us to gain a greater understanding of plant physiological function.
Jones HG (1992) Plants and Microclimate. Cambridge University Press, Cambridge
Rosenberg NJ, Blad BL, Verma SB (1983) Microclimate: The Biological Environment, 2nd edn. John Wiley and Sons, New York