Abstract: Clonal plants can adapt to stressful environments through clonal integration, the effects of which on stress tolerance may be environmentdependent. With a greenhouse pot experiment, we examined the effects of clonal integration on the tolerance to partial burial (only distal ramets were buried) of clonal fragments (with two nodes) of the noxious invasive species, Mikania micrantha, in Hainan under different soil nutrient conditions (low or high level). The results showed that when the distal ramets were buried at 3 cm depth, they all emerged with a high rate, regardless of the existence of clonal integration. When the distal ramets were buried at 6 cm depth, clonal integration significantly increased emergence rate (from below 17% to 67%). These results were independent on soil nutrient conditions. For the clonal fragments with emergence of both their proximal and distal ramets, burial depth and clonal integration did not significantly affect their total biomass, although the biomass of proximal or distal ramets might be changed. Even for clonal fragments with distal ramets buried at 6 cm depth, clonal integration could maintain their biomass at a level similar to that with distal ramets unburied. These results were also not dependent on soil nutrient conditions. Therefore, clonal integration is one of the ecological strategies of M. micrantha to adapt to partial burial, which could increase the survival of the buried ramets of M. micrantha and plant fitness when subjected to partial burial. The effect of clonal integration on emergence rate and biomass production of M. micrantha did not significantly differ under different soil nutrient conditions, which may be due to that the amount of resources transported between clonal ramets had no variation, or that the burial depth (6 cm) was not enough to lead to differences in plant growth.

Key words: dissolved organic matter, freeze-thaw disturbance, soil leachate, three-dimensional fluorescence spectroscopy-parallel factor analysis., soil moisture