[Objective]Determining the appropriate topographical conditions of seabuckthorn ( Hippophae rhamnoides) plantations in semi-arid region of Loess Plateau in north Shaanxi could provide a basis for the stable construction and sustainable management of the plantation forest in this area. [Method] Seabuckthorn plantations with different topographical conditions were surveyed in Wuqi County,Yan’an City,Shaanxi Province using the method of sampling plots. The mortality of seabuckthorn plantations in different topographical conditions were analyzed by correlation analysis and single factor variance analysis from slope position, slope direction, and gradients. [Result]The mortality of seabuckthorn plantations increased firstly and then decreased from the top to the bottom of slopes. Non-significant differences of mortality were showed among the slope positions,although it is 38% at the top,47% at the middle and 31% at the bottom of slopes. The mortality of seabuckthorn plantation at shady slope was the lowest among all the slope directions,with the maximum value of 21% and the average of 4%. The highest mortality occurred on sunny slope,with the minimum of 33% and the average of 63%. The mortalities of semi-shady and semi-sunny slopes were between those of shady and sunny slopes,and the average mortality of seabuckthorn plantations was lower on semi-shady slope than on semi-sunny slope. There were significant differences (P <0. 05) between the shady slope and semi-shady slope,semi-sunny slope and sunny slope. The mortality of seabuckthorn plantations on different slopes rose with increasing gradients. On shady slope,the growth was not obvious. The variation of mortality with gradients was logarithmic on semi-shady slope,linear on semi-sunny slope and exponential on sunny slope. The morality of seabuckthorn plantations had non-significant correlation with the slope position,but significant ( P <0. 01 ) with the slope direction and the gradient. Moreover,the effect of gradient to the mortality was stronger than that of slope aspect. Seabuckthorn forests on shady slope presented a slight degradation ( mortality 0% -30%) . Seabuckthorn plantations on semi-shady slope and semi-sunny slope were the same,of which the flat slope (5° -15°) and the gentle slope (15° -25°) displayed slight degradations, the steep slope (25° -35°) and the extremely steep slope (35° -45°) showed moderate degradations ( morality 30% -70%) . Seabuckthorn plantations of the extremely steep slope on sunny slope showed a severe degradation,and other three gradient sections had moderate degradations ( morality 70% -100%) . [Conclusion]In the semi-arid region of Loess Plateau in north Shaanxi where the average annual precipitation is less than 500 mm,the main cause for death of seabuckthorn plantations was lack of water. Suitable topographical conditions were shady slopes,semi-shady and gentle slopes,semi-shady gentle slope,semi-sunny flat slopes,and semi-sunny gentle slopes.%【目的】确定沙棘人工林在陕北半干旱黄土区适宜的地形条件，为该区人工林的稳定性建设及其可持续经营提供参考。【方法】通过样方法对陕西省延安市吴旗县的13年生沙棘人工林进行调查，采用相关分析和单因素方差分析，从坡位、坡向和坡度3个方面，比较不同地形条件下沙棘人工林的死亡率差异。【结果】随坡位降低，沙棘人工林的死亡率先增大后减小，上坡、中坡和下坡的平均死亡率分别为38%，47%和31%，不同坡位间的差异均不显著；在不同坡向中，沙棘人工林死亡率最轻的是阴坡，最大值仅21%，平均为4%，死亡率最高的是阳坡，最小值为33%，平均值为63%，半阴坡和半阳坡的死亡率介于阴坡和阳坡之间，其中半阴坡的平均死亡率稍低于半阳坡，阴坡与半阴坡、半阳坡、阳坡的死亡率均差异显著(P＜0.05)；在不同坡向中，沙棘人工林的死亡率均随坡度升高而增大，阴坡死亡率增大趋势不明显，半阴坡呈对数型增大，半阳坡呈直线型，阳坡呈指数型；沙棘人工林死亡率与坡位相关不显著，与坡向和坡度相关均极显著(P＜0.01)，其中，坡度比坡向对沙棘人工林衰退死亡的影响更大；阴坡沙棘人工林均属于轻度衰退(死亡率0%～30%)，半阴坡和半阳坡的平缓坡(5°～15°)和缓坡(15°～25°)属于轻度衰退，陡坡(25°～35°)和极陡坡(35°～45°)属于中度衰退(死亡率30%～70%)，阳坡的平缓坡、缓坡和陡坡均属于中度衰退，极陡坡属于重度衰退(死亡率70%～100%)。【结论】在年均降水量小于500 mm 的陕北半干旱黄土区，沙棘人工林衰退死亡的主要原因是水分不足，其适宜的地形条件是阴坡、半阴坡平缓坡、半阴坡缓坡、半阳坡平缓坡和半阳坡缓坡。
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