山西太岳山油松林木夏季树干液流速率的研究

2005年6—8月在山西太岳山32年生油松林内,用TDP探针,采用热平衡技术,测定油松林木树干液流速度.研究结果表明:晴天液流速度曲线略呈现双峰形状,为11:00和13:00时(0.002 97,0.002 94 cm/s),12:00流速略有下降(0.002 73 cm/s),反映出林木蒸腾轻度午休现象.树干液流速度晴天大于阴天,雨天液流速度很低.相同天气条件下树干液流速度存在随林木胸径增大而上升的趋势,树干液流速度主要受太阳辐射强度、气温和空气相对湿度影响.夏季林木日平均液流量与树干胸高横断面积呈正比.试验林夏季日平均单株液流量为白天8.666 3 dm3/d,日总量10.373 3 dm3/d,30年生油松林分夏季日平均蒸腾速率为12 843 dm3/(hm2.d),其中白天蒸腾10 730 dm3/(hm2.d),占日蒸腾总量的83.55%.

Sapflow rate of Pinus tabulaeformis in summer in Taiyue Mountain of Shanxi Province,north China.

The sapflow rate of a 32-year-old Pinus tabulaeformis forest was investigated as well as the influence of environmental factors on the rate in Taiyue Mountain,Shanxi Province from June to August in 2005.The techniques of thermal dissipation sap velocity probe(TDP) and ICT——2000 were used in the study. Results showed that the curve of sapflow rate presented a two-peaked pattern in sunny days: diurnal sapflow increased from 7:30 and reached the first peak at 11:00((0.002 97) cm/s)and second peak at 13:00((0.002 94) cm/s).Between the two peaks,the rate dropped down slightly to(0.002 73) cm/s at 12:00.Generally,sunny days had larger sapflow rates than cloudy days,and in the last place rainy days.The sapflow rate under the same weather condition had a trend to rise with the increase in the diameter at breast height.The sapflow rates in different days were affected mainly by such environmental factors as solar radiation,relative humidity and air temperature.The average daily sapflow amount was positively correlated with the cross area at breast height of trees.The average daily sapflow per tree amount in mid-summer was 10.373 3 dm~3/d,of which the diurnal amount was 8.666 3 dm~3/d.For the 32-year-old P.tabulaeformis plantation,the average daily transpiration rate in summer was 12 843 dm~3/(hm~2·d),and the diurnal transpiration amounted to(10 730) dm~3/(hm~2·d),accounting for 83.55% of the whole day.