黄土高原两种树形苹果园花期温度垂直变化特征及预测

Vertical temperature distribution and its forecast for two tree structures of apple orchard during the blooming period in the Loess Plateau

温度是苹果花期最为敏感的生态因子,选择两种在黄土高原区具有代表性的不同树龄和树形结构(盛果期小冠开心形和初挂果期自由纺锤形)的富士苹果园,利用小气候梯度自动测定系统在2011—2014年苹果花期进行定位观测,分析花期不同天气类型下(晴天、阴天或多云、雨天)的果园温度梯度及树体温度的变化特征,并基于气象站温度(TM)建立了果园冠下温度(TL)的推算模型.结果表明:花期果园温度的垂直分布及与园外的差异主要取决于树形结构,而不同天气类型下的差异不显著.平均温度、日最低温度从树冠下到顶部递增,日最高温度、日较差递减.小冠开心形冠层下部晴天日较差最大,多云或阴天冠层中部和顶部日较差较自由纺锤形小.园内外温差的日变化自由纺锤形呈现高-低-高的单波谷形态、而小冠开心形呈单峰形态,园外最低温度高于冠层下部而与冠层中部的温度接近,小冠开心形冠层下的最低温度较园外最低温度更低,特别是多云或阴天更明显,而冠层中部和顶部与园外的温度差异则较自由纺锤形小.线性模型能够较好地推算树冠下部的温度,误差绝对值在1℃以内,特别是自由纺锤形果园和雨天条件下效果更好.

Temperature is the most sensitive environment factor for the blooming period of apple.Temperatures at different levels were measured by automatic micro-climatic gradient system in the blooming periods from 2011 to 2014,in two Fuji apple orchards with two different tree ages and structures [small canopy open center shape（ SMCOCS） and freedom spindle shape（ FSS） ],respectively,which were typical in the Loess Plateau. Variations of the temperature gradient in both canopy and tree body were analyzed in sunny,overcast,cloudy,and rainy weather conditions,and a predicting model was established that could predict the temperature of the canopy（ TL） according to the temperature observed in nearby meteorological station（ TM）. The results showed that the vertical distribution of canopy temperature and its difference to the outside of orchard was mainly due to the tree structure,rather than the weather condition. The average temperature and daily minimum temperature increased while the daily maximum temperature and the diurnal temperature range decreased from the bottom to the upper of the canopy. For SMCOCS,the diurnal temperature range reached its peak under the canopy in the clear days,and the diurnal temperature range was less than that for FSS in the middle and upper canopy in cloudy or overcast conditions. The daily variation of temperature difference between inside and outside the orchard behaved as a single peakvalley-peak for FSS but as a single peak for SMCOCS. The minimum temperature outside the orchard was closer to that in the middle of canopy,but higher than that in the bottom of the canopy.For SMCOCS,the minimum temperature in the bottom of its canopy was rather lower than that in the orchard outside,especially in cloudy or overcast day,while in the middle or upper canopy,the minimum temperature difference with the orchard outside was smaller than that for the FSS. The linear model was found to be able to predict the TL with absolute errors below 1 ℃,and the best prediction was found for the FSS in rainy days.