干旱区绿洲核桃-冬小麦间作系统核桃吸收根空间分布

Spatial Distribution of Fine Roots of Juglans regia Trees in Walnut-wheat Intercropping System in Arid Oasis

塔里木盆地人均耕地占有量小,在绿洲灌溉条件下核桃的大面积栽植多采用与农作物间作的模式。采用田间分层挖掘法和图像扫描分析法,对塔里木盆地绿洲灌溉条件下核桃-冬小麦间作系统中核桃吸收根(直径≤1 mm)的空间分布进行研究。结果表明:在垂直方向上,核桃吸收根集中分布在10～80 cm土层,约占采样吸收根总根长密度的65.9%,根长密度随土层深度的变化呈指数函数分布;在水平方向上,核桃吸收根根长密度随着与树干距离的增加呈明显的降低趋势,距离两侧核桃树干0～175 cm,核桃吸收根长密度占采样吸收根总根长密度的65.3%,间作巷道中央吸收根根长密度最低。在绿洲灌溉条件下,核桃-冬小麦间作系统中核桃吸收根水平和垂直分布决定了进入盛果期后,距离树干175 cm以内的10～60 cm土层是核桃与冬小麦的主要水肥竞争区域。

Under irrigation in an oasis in the Tarim Basin, the plant mode of Juglans regia L. intercropped with crops was used more because of the limited area of cultivated land per capita. The research was conducted to investi-gate the spatial distribution of fine roots （diameter ≤1 mm） of J. regia trees in J. regia-wheat intercropping system in the Tarim Basin using the layered digging and image analysis methods. Results showed that, in vertical direction, the fine root length density of J. regia trees increased with the increase of soil depth in layer of 0-40 cm and de-creased with the increase of soil depth below 40 cm. The fine roots grew mainly in soil layer of 10 - 80 cm, their pro-portion accounted for 65.9% of the total, and that in soil layer below 80 cm was 34.1%. The fine root length density of J. regia trees in the J. regia-wheat intercropping system varied with soil depth in an exponential way. In horizontal direction, the proportion of the fine roots 175 cm away from the tree rows was 65.3% of the total. The fine root length density in the middle of alley in the intercropping system was minimum and relatively even. The patterns gained by analyzing the vertical and horizontal distribution of fine roots showed that, under irrigation in the oasis, the soil layer of 10-60 cm within 175 cm away from the trees was the main area for J. regia trees and wheat to compete soil mois-ture and fertilizer. Thus it is necessary to strengthen the water-fertilizer management in this competition area in farm-ing practice.