黄土高原苹果园不同生长阶段的小气候特征

Microclimate characteristics of apple orchard at different growth stages on the Loess Plateau

在黄土高原苹果园内,使用小气候梯度自动测定系统于2011年1月-2013年12月定位观测果园6、3、1.5 m高度的光合有效辐射（PAR）、气温、树体温度、相对湿度以及冠层顶的总辐射和土壤10-60 cm深度的温湿度,分析了苹果园不同生长阶段的小气候特征。结果表明：总辐射、PAR、空气温度和树体温度日变化均呈单峰曲线,总辐射和PAR在12：50、空气温度和树体温度在16：00左右达到最大值;总辐射和PAR在生长盛期最强,生长始期次之;空气温度、树体温度和土壤温度在盛期随辐射变化最大,在始期次之;生长始期温度日较差最大;冠层下部PAR在生长盛期和休眠期小于冠层顶,休眠期空气温度垂直变化最大,盛期次之,除土壤表层外,其余各层土壤温度均随深度增加而升高且日变化较小;空气湿度生长盛期最大,休眠期次之,日变化呈现高-低-高趋势,冠层下部的湿度在夜间高于冠层顶部且盛期相差最为明显,生长始期其日较差最大,盛期次之;生长始期土壤含水量最高,盛期次之,表层和深层含水量较小,20 cm含水量高,但其变化幅度较大。

An automatic measurement system of microclimate gradients was employed to observe photosynthetically active radiation （PAR） , air temperature, tree body temperature, relative humidity at different heights of 6, 3 and 1.5 meters, and total radiation atop the canopy and soil temperature and humidity from 10 to 60 cm with intervals of 10 cm in an apple orchard on the Loess Plateau from January 2011 to December 2013. The microclimate characteristics of the apple orchard at different growth stages were investigated. The results showed that the total radiation, PAR, air temperature and tree body temperature all presented an obvious diurnal variation with one peak. The total radiation and PAR peaked at 12：50, air temperature and tree body temperature peaked around 16： 00. The total radiation and PAR reached maximum at vigorous growth stage and second at initial growth stage. The air temperature, tree body temperature and soil temperature reached maximum at vigorous growth stage, and came second at initial growth stage. PAR atop the canopy was greater than that beneath the canopy at vigorous growth and dormant stages. The vertical variation of air temperature was greatest at dormant stage, and next at vigorous growth stage. Except at the surface, soil temperatures increased with the depth, accompanying a smaller diurnal variation. Humidity was maximum at vigorous growth stage, and next at dormant stage, and its maximum daily difference occurred at initial growth stage and came second at vigorous period. Humidity was higher beneath canopy than atop canopy during night, especiallyat vigorous growth stage. Soil moisture growth stage. It was lower in the surface with a great variation. was highest at initial growth stage and next at vigorous and deep layers, and reached maximum at 20 cm depth