The growth and development of plants, insects and other invertebrates largely depends on the temperature from. Many of these organisms slow or block their growth and development when temperatures rise or fall above or below certain thresholds. All plants need a certain individual temperature in order to be ready for that blossom to be. The accumulation of thermal energy over a certain period of time is called growth degree days or temperature sums (heat sums). It is a heuristic (in contrast to logistic) calculation in the phenology,
As a rule, the degree of growth (WGT) is calculated by taking the average of the daily minimum and maximum temperature and comparing it with a threshold value (10 ° Celsius in Central Europe). The measurement of degree of growth days and temperature sums is used to determine planting dates, to predict flowering and optimal harvesting time, and to select the most appropriate varieties depending on their phenological Maturity date (early to late).
The development of insects and arachnids such as mites also largely depends on the average daily temperature. A simple determination of temperature sums can be related to plant protection be useful to predict the outbreak date of various pests under glass; and to determine the exact date of use of suitable control agents or measures. The first scientific study regarding the climatic influence on viticulture comes from the Swiss botanist Augustin Pyrame de Candolle (1806-1893).
Based on this knowledge, in California by Albert Julius Winkler (1894-1989) and Maynard A. Amerine (1911-1998) carried out an analysis, the results of which in 1944 led to the introduction of a daily heat accumulation system and division into five climatic zones. In the meantime, many wine-growing countries have had similar ones air conditioning systems introduced. See also under Weinbauwürdigkeit,