Soil matric potential (SMP) is usually monitored by a tensiometer for managing irrigation in forest plantations, so determining where to install the tensiometer is important for improving irrigation efficiency. However, such work has never been conducted for border irrigation, which is commonly used in the intensive cultivation of forest plantations. In a border irrigated Populus tomentosa plantation on sandy loam soil, we monitored the daily changes of SMP at eighteen different positions in soil wetting volume (WV) [expressed in P_{x y} (x means distance from the trunk in cm, y means soil depth in cm)], transpiration (T), and stem growth rate (GR) in a growing season. The fine root distribution was also investigated in two successive growing seasons. The result of time stability analysis showed that, among the eighteen positions, the annual absolute mean relative difference (RD) and the standard deviation of the RD of SMP at P_{25 40} were not the lowest, but its root mean square error of the SMP relative deviation reached the lowest in the growing season. The root water uptake at P_{10 10} had the highest influence on T rate (R² = 0.220, P < 0.01) and GR (R² = 0.112, P < 0.05). The fine roots distribution changed greatly with the stand development, but its pattern within the WV was relatively consistent in different years. There were three dense fine roots zones located around P_{10 10}, P_{40 10}, and P_{10 50}. Consequently, it was suggested to place tensiometers at two positions, i.e., P_{25 40} and P_{10 10}, with the former being used for estimating irrigation amount and the latter for triggering irrigation. This recommended tensiometer placement strategy will not only help to improve the irrigation efficiency in P. tomentosa plantation but also provide a reference for the irrigation management in stands of other tree species.

通常通过张力计来监测土壤基质势（SMP），以管理森林人工林的灌溉，因此确定在何处安装张力计对于提高灌溉效率非常重要。但是，从未对边界灌溉进行过此类工作，边界灌溉通常用于森林人工林的集约化种植中。在砂壤土上的边界灌溉毛白杨人工林中，我们监测了土壤湿润体积（WV）中18个不同位置上SMP的每日变化[以P _{x y}表示（x表示与树干的距离，以厘米为单位，y表示土壤深度，以厘米为单位）]，蒸腾（T）和生长季节中的茎生长速率（GR）。在两个连续的生长季节中还研究了细根分布。时间稳定性分析的结果表明，在18个位置中，P _{25 40}时SMP的年度绝对平均相对差（RD）和RD的标准偏差不是最低的，而是SMP的均方根误差相对偏差在生长季节达到最低。P _{10 10}的根系吸水量对T率（R ² = 0.220，P  <0.01）和GR（R ² = 0.112，P）的影响最大。 <0.05）。随着林分的发展，细根的分布发生了很大的变化，但是在WV中，其根系的模式在不同年份中相对一致。在P _{10 10}，P _{40 10}和P _{10 50}周围有三个密集的细根区。因此，建议将张力计放置在两个位置，即P _{25 40}和P _{10 10}，前者用于估算灌溉量，后者用于触发灌溉。推荐的张力计放置策略不仅有助于提高毛白杨人工林的灌溉效率，而且还为其他树种林分的灌溉管理提供了参考。