油松人工林SPAC水势梯度的时空变异

为了解油松林水分运作机制 ,给干旱区造林树种的选择提供依据 ,该文利用压力室、露点水势仪对京西低山油松人工林土壤 植物 大气连续体 (SPAC)的水势梯度及相关因子进行了连续同步测定 .结果表明 :在空间水平上 ,油松林地SPAC各要素水势由土壤到植物再到大气逐步下降 ,梯度比约为 1∶5∶30 ;灌水后SPAC相临界面水势差增大 ,水势梯度比提高至 1∶15∶90 .在时间序列上 ,持久干旱条件下的油松林SPAC各要素水势的日变化和连日变化均呈下降趋势 ,下降的幅度以大气最甚 ,叶片次之 ,土壤最小 ;叶片水势日变化波峰出现于 14:0 0 ,较土壤和大气(18:0 0 )早 4h ;土壤水势的下降幅度随土层由浅而深逐渐减小 .灌水后各层土壤水势由浅而深水势先后升高 ,升高幅度表层和中层较大 ,深层较小 ;叶片水势虽提高 ,但幅度明显小于土壤 .在影响油松林SPAC水势的环境因子中 ,空气温湿度与大气水势和土壤水势相关性显著 ;空气和土壤湿度则是影响叶片水势的主导因子 .

Spatial-and-temporal variation laws of SPAC water potential gradient of P.tabulaeformis plantation

The research on P. tabulaeformis plantation's water transportation mechanism is important for drought area to choose afforestation tree species. The SPAC water potential gradient of P. tabulaeformis plantation and its relative factors are measured by using Dew Point Microvoltmeter and Pressure Bomb at low altitude hills in the west of Beijing. The results show that: at the spatial level, the water potential of SPAC element in the soil, that in the plant and that in the air gradually descends. SPAC water potential gradients are different among conterminous interfaces of soil, leaf and air are amplified from 1∶5∶30 to 1∶15∶90 after watering. While at the temporal level, daily and diurnal vaviations of water potential of SPAC elements gradually descend after a long period of drought, with the descended amplitude air>leaf>soil. Peak of water potential's daily variation of leaf is about 14:00 pm, 4 hours earlier than that of soil and air. The descendant extent of water potential of surface soil is higher than that of deeper layers. Water potential of soil ascends orderly from surface to deep layers after watering, and the amplitudes go as same as that in the drought. Among the affecting environmental factors on water potential, air relative humidity and air temperature affect water potential of air and soil most, and soil moisture and air relative humidity are the most important factors which affect leaf water potential.