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201.
P. R. Bird 《Agroforestry Systems》1998,41(1):35-54
The effects of windbreaks on pastures are reviewed, with an emphasis on temperate grazing systems. Mechanisms of plant response
to shelter are dealt with in brief. Few papers on measured responses of pasture species to shelter were located in a search
of the global literature for the period 1972–97. Except in cold climates, where the benefits of snow-trapping on water availability
can be demonstrated, there were few reports of increased production of pasture in response to shelter. A significant result
was obtained in a summer rainfall environment in Australia, where a 43% increase in wool production was obtained over three
years in small plots sheltered with iron sheeting on the fences. The gain was attributed to increased pasture growth. In New
Zealand, one study over three years with a narrow, permeable shelterbelt in a windy, dry summer environment showed a 60% increase
in pasture growth in the sheltered zone. However, another study on a high rainfall site with a dense, wide shelterbelt found
no substantial shelter effect on pasture. In dry, hot and windy climates there appears to be scope for protecting spray-irrigated
pasture with windbreaks. The feasibility of evaluating shelter effects on pastures or crops from old windbreaks is questioned.
Variability of soil over the site can not be satisfactorily accounted for and there are problems in defining the true ‘unsheltered’
yield. Shelter effects on pastures could best be determined by comparing production in small completely sheltered plots and
open plots. Effects in and near the competitive zone should be measured for living windbreaks. Modelling could then be used
to evaluate windbreak systems. We are not yet in a position to provide unequivocal advice to farmers on windbreak outcomes
for particular purposes or regions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
202.