多枝柽柳幼苗根系分布对灌溉量的响应

Response of the Distribution of Roots of Tamarix ramosissima Seedlings to Irrigation with Different Volumes

通过分层分段挖掘法,对塔克拉玛干沙漠腹地不同灌溉量条件下(35,24.5,14 kg/株.次)多枝柽柳(Tamarix ramosissima)幼苗根系分布特征进行了研究。结果表明:随着深度的增加,各灌溉量根系生物量逐渐减少;但随着灌溉量的减少,其深层次根系生物量有增加的趋势。各灌溉量地下生物量的分布与深度呈显著的负对数关系。采用数值拟合方法,对不同灌溉量条件下多枝柽柳根系消弱系数(root extinction coefficient)进行了求解,结果表明:随灌溉量的减少,滴灌条件下多枝柽柳根系消弱系数有增加的趋势。根长和根表面积在垂直方向的变化趋势,随灌溉量的不同而有所不同。灌溉量为35,24.5 kg/株.次的2个处理,根长和根表面积随深度的增加呈指数递减;而灌溉量为14 kg/株.次的处理,根长与根表面积为“单峰型”曲线。

The study area is located in the hinterland of the Taldimakan Desert, where the annual temperature and monthly temperatures in July （the hottest month） and December （the coldest month） are 12.4 ℃, 28.2 ℃ and -8.1℃, the extremely maximum and minimum tempexatures are 45.6℃ and - 22.2℃, respectively, the annual accumulated tenaperature ≥10℃ is 4 621.8℃ ; the frost-free period is 283 days, the annual sunshine duration is 2 571.3 hours; the annual precipitation and evaporation are 36.6 mm and 3 638.6 mm respectively; and strong winds and dust weathers occur frequendy. In this paper, the vertical distribution characteristics of roots of annual Tamarix ramosissima seedlings under irrigation with different volumes （35.0 kg/plant·time, 24.5 kg/plant·time and 14.0 kg/plant·time） in the hinterland of the Taklimakan Desert are lucubrated. The results reveal that the root biomass of annual T. ramosissima seedlings is gradually decreased with increasing soil depth under irrigation with different volumes, but there is an increase trend in deep-seated root biomass only with decreasing irrigation volume. There is a significant negative logarithm relationship between the underground biomass of annual T. ramosissima seedlings and the soil depth under irrigation with different volumes. The root extinction coefficients of annual T. ramosissima seedlings under irrigation with different volumes are calculated using numerical simulation. The results reveal that there is an increase trend in root extinction coeffident of annual T. ramosissima seedlings with decreasing drip irrigation volume. The vertical change of root length and root surface area is different under irrigation with different volumes. The root length and root surface area are decreased in an exponential way with increasing soil depth under irrigation with volumes of 35.0 kg/plant.time and 24.5 kg/plant· time, and the curves of root length and root surface area under irrigation with volume of 14.0 kg/plant·time are unimodal.