Giant goldenrod (Solidago gigantea) population growth and management efficacy

Background/Question/Methods

Although Europe is viewed as suffering fewer biological invasions than North America, the number of plant invasions continues to increase. Solidago gigantea (giant goldenrod) was deliberately introduced to England from North America as an ornamental plant over 200 years ago. It has since spread across the European continent to become one of the most problematic invasive plants in central Europe. Combining data from a series of experiments performed in Hungary as well as using estimates from the literature, we developed a demographic matrix model to explore the dynamics of giant goldenrod and the efficacy of management practices aimed at reducing local population density. The stage-structured model consisted of small, medium and large vegetative shoots and flowering adult shoots, and transitions between the stages were parameterized by combinations of various rates, such as the number of seeds produced in a flowering shoot, the probability of seed germination, the probability of growth and survival to a larger stage, and the average number of shoots produced at each stage.

Results/Conclusions

The S. gigantea populations modeled experienced positive growth under almost all circumstances. The stable age distributions were different in the two types of populations modeled (wet and dry environments), with almost no small vegetative shoots in the more productive wet environments.  The elasticities of the growth rates indicated that the populations were most responsive to changes in transition rates between flowering shoots and medium vegetative shoots, and between flowering shoots and large vegetative stems. The most common management treatment (mowing) was not effective at the level measured in the field (20% reduction); nearly complete reduction of stems produced was necessary to suppress population growth. Insights from the model into what levels of management are required to suppress local population growth of giant goldenrod invasions can lead to more appropriately targeted management practices.