黄土丘陵地区唐古特白刺根际土壤水分与根系分布研究

以根际土壤水分和根系分布特征为主要指标,研究了兰州北部黄土丘陵地区唐古特白刺根系分布和根际土壤水分的响应关系。结果表明,唐古特白刺根际土壤水分变化规律明显,0～40 cm土层含水量变幅较大,40～80 cm土层含水量最高,之下随土层加深而递减,160～300 cm土层含水量没有明显变化。唐古特白刺平均根长100 cm,根幅300 cm。主根较粗,入土浅,根长为地上株丛高的1.32倍,侧根发达,扩展范围较广,根幅为冠幅的3.23倍,地上生物量为根系生物量的1.46倍;有效根系主要分布于0～40 cm,在0～20和20～40 cm土层中,有效根重分别占总有效根重的58.69%和22.96%,有效根长分别占总有效根长的59.65%和23.20%,0～40 cm土层是吸收和利用水分的重要区域,该层土壤水分含量随季节呈现明显的动态变化,根系的浅层分布和分布面积扩大,对于及时有效利用季节性降水有重要意义。根系的水平分布范围是垂直分布范围的3倍,这种根系分布格局对于以自然降水为唯一水分补充方式的黄土丘陵地区,有利于对来自降水而短暂提高的土壤浅层水分的吸收。

Study on soil water in rhizosphere and root system distribution of Nitraria tangutorum on Loess Plateau

The soil water in rhizosphere and root system distribution of Nitraria tangutorum was studied in hilly area in north part of Lanzhou City on Loess Plateau. The result indicated that the soil water content in rhizosphere incresed and then decreased as the soil depth. The variation of soil water content within 0 to 40 cm layer was higher and it was lower within 160 to 300 cm layer. The soil water content within 40 to 80 cm layer was the highest. The root length and diameter of root system were 100 cm and 300 cm respectively. The root length was 1.32 times of plant height. The diameter of root system was 3.23 times of plant crown. The aboveground biomass was 1.46 times of underground. The effective roots were mainly distributed within 0 to 40 cm layer, and the effective root weight within 0 to 20 cm and 20 to 40 cm layers accounted for 58.69% and 22.96% of the total respectively. And for the effective root length, they were 59.65% and 23.20% respectively. The amount of effective roots decreased significantly as the soil depth. The 0 to 40 cm layer was very important for the water utilization and the horizontal distribution range of roots was 3 times of that in vertical range. This pattern of root distribution helps the water absorbtion of plant which depend the natural rainfall as the only water source on Loess Plateau.