植物为了应对自然界中具有时空异质性特点的土壤养分，往往会通过根系的养分捕获塑性来加强对于土壤养分的吸收。而植物在自然界中往往不是单株存在的，而是通常以群落的形式存在，这样研究植物根系的塑性反应和其相互竞争关系 (包括种间竞争和种内竞争) 之间的互作过程就很有必要。目前关于植物塑性方面的研究已较多，将根的养分捕获塑性和其相互间竞争关系一起考虑的研究也有一些，但大都是以实验最后收获的净产物为指标，如生物量、长度等，鲜有涉及根系的动态生长过程的。不同的竞争及养分条件下植物细根会在何时、何处作出怎样的动态反应是我们所关心的具体过程。 本研究以北美枫香 (Liquidambar styraciflua L.) —火炬松 (Pinus taeda L.) 为研究对象，探究了其各种竞争组合在稳定养分和瞬时养分的组合下，包括稳定斑块养分种间竞争、稳定斑块养分种内竞争、瞬时斑块养分种间竞争、瞬时斑块养分种内竞争以及总体对照处理—均匀养分种间缓释，地下过程的具体动态变化。在研究中将微根窗图像数据化所得的数据，包括长度和直径，与图像上的根“个体”进行一一匹配，并加标号标识；将上述得到的每周的微根窗长度数据作图并进行比较，并用重复测量方差分析来比较不同时间节点及不同实验处理间的差异；将微根窗观测的长度数据和相应的生物量数据加以比对；将根分枝再定义为“终点事件”利用失效时间分析中的Kaplan-Meier法进行相应的分析。 结果倾向于得出下列所述：1) 北美枫香和火炬松在不同处理组合中，微根窗观察长度除在种间竞争时的第3土层略微不显著外，其余处理的时间节点上的差异均很显著，并且在种间竞争和稳定养分的条件下，除第2土层外，物种之间的微根窗长度差异均较为稳定；2) 北美枫香和火炬松两物种在对斑块性的养分相互竞争时，增殖的微根窗长度均优于在面对均匀的养分条件时，并且在稳定养分处理的第1和第3土层两物种长势一致，相互间的差异缩小；3) 火炬松在微根窗观测图像中没有出现直径小于0.2mm的根，转而代以出现了直径为0.2-0.3mm的根，且增殖了相当的长度；且火炬松除了在各自种内竞争时的稳定养分处理和瞬时养分处理的第4土层外，其余处理每个土层的根的直径均比相应土层的北美枫香的根直径要大；4) 北美枫香在种间竞争的条件下，包括均匀养分、瞬时斑块养分及稳定斑块养分3个处理中，在4个土层间的分枝时间会出现显著差异，其中前两者在实验前期和后期均出现了差异，而后者则是在实验前期差异显著。另外北美枫香还在稳定养分的种内竞争处理中在实验后期表现出了明显差异。

In order to utilize the soil nutrient resources more effectively, which is featured with spatial-temporal heterogeneity in soil, plant will enhance their nutrient uptake via the combination of a series of root plasticity. It is essential that we study the plastic responses of plant roots, the competition (inter- and intra-specific competition) and the interaction relationship of both mentioned above, due to the presence of plant communities. There have been numerous researches on plant root plasticity and the relationships of plasticity and competition. However, the lack of awareness of the process of how plants compete each other is their common disadvantages, and the indictors are usually biomass and length of roots, which are the net product of the process. So when, where and how the fine roots of plants dynamically respond to diverse competition and nutrient conditions are still remain unknown. My study explored the underground dynamic responses of sweetgum resin (Liquidambar styraciflua L.) and loblolly pine (Pinus taeda L.) under various of treatments, including the treatment of interspecies patchy slow release, intraspecies patchy slow release, interspecies patchy pulse, intraspecies patchy pulse, interspecies homogeneous slow release. I matched the data including root length and diameter which is from minirhizotron system with the images and made labels on it. And I plotted and compared the observed length from minirhizotron in every week. Furthermore, I compared the differences during tine nodes and experimental treatments via repeated measures analysis of variance method. Then I redeclared the concept of end point event in order to apply Kaplan-Meier analysis approach (one of the failure time analysis methods) in it. The results tended to show that: 1) There were significant differences in observed length from minirhizotron images during all time nodes in all treatments except in the soil layer 3 of interspecific competition. Moreover, the steady differences of observed length also existed in other 3 soil layers except in soil layer 2 in the treatment of the interspecific competition and the patchy slow release. 2) The observed length data from minirhizotron of the two species under patchy nutrients was superior to the length which they were in the condition of homogeneous nutrients, and the differences of the two species shrinked in the soil layer 1 and 3 of the patchy slow release treatment. 3) Loblolly pine had no roots’ diameter < 0.2mm in minirhizotron images, what’s more, the diameters of loblolly was larger than sweetgum resin except in the 4th soil layer of the intraspecies patchy slow release and the intraspecies patchy pulse. 4) Under the condition of interspecies competitions, the branching time of sweetgum resin varied significantly in all 4 soil layers. And the treatment of the interspecies patchy pulse and the interspecies homogeneous slow release emerged differences in our early experiment, whereas in the treatment of interspecies patchy slow release was in late experiment.