Investigations of microclimatic improvement, sand protection, and growth promotion of a crop by multiple row windbreaks made of several mixed trees were carried out near the Turpan Desert Research Station at Turpan, Xinjiang, China in the middle of June, 1994. The main results are:
(1) Wind speed was decreased by the first windbreak partially recovered near the second windbreak, but decreased further after it, i.e., the decrease in wind speed was accumulative as the number of windbreak rows increased.
(2) In summer, excessive increases in air soil temperatures near the windbreak during the daytime had a negative effect on crops. However, there was a positive effect on the temperatures between the first and second windbreaks due to the decrease in radiative cooling.
(3) The water vapor content in the air was increased by evaporation from the soil and transpiration from windbreaks and crops, in particular in the weak wind at night because of the temperature decrease. Absolute humidity increased at the daytime in summer, but relative humidity generally decreased due to the temperature increase caused by windbreaks.
(4) Windbreaks promoted the growth and development of young crops, presumably due to the higher temperature and to the decreasing energy exchange accompaning the lower wind speeds. As a result, crop quality and productivity increased.
(5) Windbreaks made of Ulmus, Elaeagnus and Populus were suitable for an agricultural field in the arid Turpan region and windbreaks made of mixed trees and multiple rows were most suitable for making oases.
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