人工林毛白杨根系特征对地下水位季节性波动的适应
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为阐明毛白杨根系对地下水位季节波动的适应性，对年平均波动幅度为363 cm的毛白杨人工林的粗根构型和细根形态进行了研究。选取3个不同年龄和种植密度的林分进行根系取样，其中34个结构根用于评价根系构型，10个树桩用于测量生根深度和蔓延距离，2106个土块(~150 cm深)用于分析细根分布。毛白杨的平均生根深度为200 cm(最大根深270 cm)，说明毛白杨可以成为芽生植物。4年生和7年生林分平均侧根扩展距离分别为437 cm和535 cm。约23%的根面密度分布在最上层20 cm的土壤中，这可能有助于毛白杨在淹水抑制深层根系吸收功能的情况下，有效地截留雨水，吸收浅层土壤水资源。一些水平、倾斜和垂直的结构根既能探测深层，也能探测浅层。综上所述，深层根系、浅层宽广而密集的侧根以及开发深、浅两种土壤资源的一些结构性根系的发育，可能是毛白杨在地下水位波动较大的地点茁壮成长的三种协同生根适应策略。
To clarify the adaptability of Populus tomentosa root systems to seasonal fluctuations of the groundwater table, a study was conducted on the coarse root architecture and fine root morphology of a Populus tomentosa plantation with an annual average fluctuation amplitude of 363 cm. Three stands with distinct ages and planting densities were selected for root sampling: 34 structural roots were used to evaluate root architecture, 10 stumps were measured to determine rooting depth and spreading distance, and 2106 soil cores (approximately 150 cm deep) were employed to analyze fine root distribution. The average rooting depth of Populus tomentosa was 200 cm (with a maximum rooting depth of 270 cm), indicating that this species is a deep-rooted plant. The average lateral root spreading distances of 4-year-old and 7-year-old stands were 437 cm and 535 cm, respectively. Approximately 23% of the root surface density was distributed in the top 20 cm soil layer, which may enable Populus tomentosa to effectively intercept rainfall and absorb shallow soil water resources when flooding inhibits the water uptake function of deep roots. Some structural roots—horizontal, inclined, and vertical—can detect both deep and shallow soil layers. In summary, the development of deep root systems, wide, dense lateral roots in shallow soil layers, and certain structural roots that exploit both deep and shallow soil resources may represent three synergistic root adaptive strategies enabling Populus tomentosa to thrive in sites with large groundwater level fluctuations.
