黄土高原半干旱区侧柏(Platycladus orientalis)树干液流动态

应用热扩散式树干茎流计(TDP)于2008年4～10月对黄土高原安塞县侧柏人工林树干液流速率进行了连续测定,并对周围气象、土壤水分等多个环境因子进行了同步测定.结果表明:侧柏在不同月份晴天树干液流速率变化具有明显的昼夜节律性,呈单峰曲线;且各月液流速率日均值受土壤供水水平限制总体上呈下降趋势,即4月份最大,为0.00135 cm · s-1;10月份最小为0.00011cm · s-1;树干液流速率与光合有效辐射、大气温度、水汽压差呈极显著正相关,与相对湿度呈负相关,其相关程度:光合有效辐射＞水汽压差＞大气温度＞相对湿度,并可用线性表达式来估算;侧柏边材面积和地径呈幂指数关系,并以此结合密度估算出样地侧柏人工林的边材面积为4.65m2,最终估算出侧柏人工林生长季总耗水量为1159.6 t · hm-2.

The sapflow dynamics of Platycladus orientali in the semi\|arid Loess Plateau region

A thermal dissipation probe (TDP) was used to measure the sapflow dynamics of Platycladus orientali in Ansai County on the Loess Plateau of China from April to October, 2008. Soil water content, photosynthetic active radiation (PAR), air temperature, relative air humidity, water vapor pressure deficit (VPD) and wind speed were measured at the same time. The results showed that patterns of diurnal variation of P. orientalis sapflow velocity on sunny days were similar with a clear pulse creating a single\|peak curve; in the case of restricted soil water levels, the daily average sapflow velocity tended to decline over time so that it was greatest in April and the least in October, being 0.00135 and 0.00011cm·s-1, respectively; sapflow velocity showed a significant positive correlation with PAR, air temperature, and water VPD, and had a negative correlation with the relative humidity, the correlation coefficients being in the order PAR > VPD > Temperature > relative humidity, so that these linear expressions can be used to estimate it; the sapwood area of P. orientali and the diameter at ground level were used for an index relationship to obtain an estimate of sapwood in the sample plots, which was 4.65 m2. Finally, it can be used to estimate the total water consumption used for transpiration by the P. orientali plantation in the growing season of April\| October, which was 1159.6 t·hm-2.