利用Minirhizotron技术 ,研究了位于美国路易斯安那州的 19年生的火炬松新根生长动态。结果表明 ,火炬松新根的根量密度随时间呈增长趋势 ,在生长季末的 1、2月份达到最大。经过林地土壤干旱处理 (通过建立穿透雨隔离系统 ,阻止雨水到达地面 )的树木的根量密度自 9.3cm处 ,随土壤深度增加呈下降趋势 ,未经干旱处理的树木在离土表 80　 10 0cm深处仍有较高的根量密度 ,达 3.4 8　5 .12条·m- 1,是经干旱处理树木对应土壤层次中根量密度的 10多倍。火炬松从 3月份开始发生新根 ,随后迅速增加 ,至 6月份发生最多 ,然后缓慢减少 ,5　 7月的新根发生数占总量的 4 1.8% ,大部分新根发生在离土表 30cm以内的土壤中。 11个月的干旱处理显著地降低火炬松的根量密度 (1 1条·m- 1,未经干旱处理的为 3 2 7条·m- 1)和新根发生数 (5 7条·株- 1,未经干旱处理的为 15 6条·株 - 1) ,干旱处理还可导致新根推迟 1 0　 1.5个月发生。 5a前在土表撒施化肥似乎对新根的发生和生长没有明显影响 Using the Minirhizotron technique, the growth dynamics of 19-year-old new roots of Pinus taeda in Louisiana, USA were studied. The results showed that the root mass density of the new roots of Pinus taeda tended to increase with time, reaching the maximum in January and February at the end of the growing season. After the woodland soil drought treatment (through the establishment of through the rain isolation system to prevent rainwater to reach the ground) of the tree density density from 9.3cm, with the soil depth decreased, non-arid treated trees in the soil surface 80 10 10 There is still a higher root density at the depth of 0 cm, reaching 3.4 8 5 · 12 · m -1, which is more than 10 times of the root density in the soil layers corresponding to drought-treated trees. The new roots of loblolly pine began to emerge from March and then rapidly increased to the highest in June and then slowly decreased. The new roots in July accounted for 41.8% of the total, and most of the new roots occurred in the off-table 30cm Within the soil. The 11-month drought treatment significantly reduced the root density density of Pinus taeda (11 × m-1, 327 × m-1 without drought) and the number of new roots (57 × strains - 1, and 15 6 non-drought-treated plants - 1). Drought treatment may also lead to a delay of 10 5 months for new roots. Fertilization of 5a soil before seemingly had no apparent effect on the occurrence and growth of new roots