利用Minirhizotron技术监测火炬松新根生长动态

Monitoring New Root Dynamics of Loblolly Pine with Minirhizotron Technique

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。

With the minirhizotron technique, the new root dynamics of 19 year old loblolly pine plantation was studied in Louisiana of US. The results are as follows: the loblolly pine root count density increases in the growing season and reaches its climax in January or February, the end of the growing season. The root count density of the trees, on which drought has been imposed by excluding the throughfall, decreases from the depth of 9.3 cm with the soil depth, and that of the trees without imposed drought is considerable higher even though in the soil depth of 80 100 cm, ranging from 3.81 to 5.12 root count·m -1 , and more than 10 times of that of those trees with imposed drought. The new roots of loblolly pine begin to initiate in March, and rapidly increase until June, when it reaches its climax, it begins to decrease slowly. The new root increment from May through July accounts for 41.8% of the total. Most of the new roots initiate in the soil depth of 0 30 cm. The 11 month long imposed drought significantly decreases the root count density and new root initiation of the loblolly pine, with the mean root count density and new root count being 3.27 root count·m -1 and 156 counts, respectively, for the trees without imposed drought, and 1.1 root count·m -1 and 57 counts, respectively, for the trees with imposed drought. The imposed drought also delays new root's initiation by 1 to 1.5 months. The fertilization applied 5 years ago seems not to have effects on new root initiation and growth.