Flaveria bidentis,an exotic plant with the strong invasiveness, spreads at the most regions of Tianjin, Hebei, Province and Shandong Province, China, and there is an evidence that it has high potential to expand to other provinces. This article aims to find out an effective, economic and environmentally friendly measure to manage F. bidentis. Clipping is a common management measure to forage species, and proper clipping can promote their tillering and regeneration, thus enhancing their production yield and quality. However, excessive clipping may restrict the growth of aboveground part of forage species. High frequency clipping above the ground not only restrain plant growth, but also prevent the seed set. After 3 to 4 years' consecutive clipping treatment, the plant would be killed eventually. There are many successful examples using the clipping measure to prevent and control invasive plants.
A field experiment was carried out to clarify the effects of clipping measure on the growth and physiological characteristics of invasive plant F. bidentis, Sixty 3 m by 3 m plots were established. Four treatments (control, one-time clipping, two-time clipping and three-time clipping) were applied to the plots in completely randomized design.
The results showed that clipping reduced the biomass accumulation of F. bidentis. Compared with the control, three-time clipping treatment was most efficient, and a reduction of 82.57%, 44.53%, 80.04% and 91.76% in total biomass, root biomass, stem biomass and leaf biomass was found respectively. The plant height and the inflorescence numbers decreased significantly with clipping times, especially under three-time clipping treatment, the inflorescence numbers declined to 0. The maximum branch numbers was recorded under one-time clipping treatment (so-called super-compensation phenomenon), while three-time clipping yielded the lowest branch numbers. Compared with control, chlorophyll content tended to decrease with increasing clipping times. In addition, clipping treatments significantly enhanced net photosynthetic (Pn), stomatal conductance (Cond) and transpiration rate (Tr). The maximum photochemical efficiency of photosystem Ⅱ (Fv/Fm) and potential activity of photosystem II (Fv/F0) under three-time clipping were significantly lower than other treatments, whereas initial fluorescence yield (F0) increased obviously. At same time, there was a trend of rise in parameters, such as net photosynthetic (Pn), stomatal conductance (Cond) and transpiration rate (Tr) upon clipping, In short, the impact of every growth and physiological index of F. bidentis was greatest by three clipping, three-time clipping affected growth and physiological indices of F. bidentis greatly, restricting its regeneration, flowering and eventually fructifying. The index of growth plasticity was higher than that of physiological plasticity, suggesting that growth plasticity was an important acclimation characteristic for clipping regimes for this invasive species.
In practice, we suggest that the clipping measure should be adapted, combine with field replacement with clipping-resistance forage species such as Sorghum bicolor × S. sudanense, Dactylis glomerata, Medicago sativa, for wise management on F. bidentis.