A list of frequently asked questions related to plant sampling. Please check these before you contact Rob or Oliver.
Q: The population that I am studying is not very dense. If I lay the transect from what I consider to be the edge of the population, then there are several plots that have less than five or even no plants in them at all. Is this okay?
A: Yes. This can happen in a sparse population, and the fact that there are only few plants in some plots is an important piece of information.
Q: If an adult plant has multiple stems, do I use all of them for the measurements?
A: All stems that belong to the same plant individual must be taken into account when counting the fruits, and when counting whole and damaged leaves. Of course the height of the adult is only measured once, on the tallest stem.
Q: Some of the leaves of adult plants are already pretty old and crumpled (a.k.a. wilted, senescent). It is very difficult to assess the herbivore damage on these. What should I do with them?
A: Leave out these leaves from all counting. For counting the whole and damaged leaves, only use those leaves that are intact enough for you to actually see the damage.
Q: There are some really tiny leaves on the rosettes, or right below the flowers on adult plants, or along the stem of adult plants. What am I supposed to do with these? Do they count?
A: All leaves that are fully expanded can be used for the leaf counts. Usually these will be at least > 1 cm.
Q: Some plants have few seeds to collect, is this okay?
A: If a plant has <10 seeds it is best to find another nearby plant, even if it is not the closest to the 20cm mark on the transect. However, seeds and measurements should be taken from the SAME plant.
Q: Why is this study important? How will this experiment improve my own efforts to control garlic mustard?
We are working towards a more interactive website to allow management ‘teams’ (including conservation or weed control groups) to monitor the effectiveness of control projects over multiple years. Integrating survey data with environmental characteristics can help to identify more effective control strategies for a given area. These control strategies include various combinations of different timing and methods (e.g. pull vs. herbicide vs. biocontrol).
Understanding the ecology of a species can lead to much more effective management decisions, but it also takes a lot more time and effort to get there. For example, the effectiveness of introducing new insects for biological control remains highly variable and difficult to predict. It is based on the idea that invaders ‘escape’ from natural enemies in the native range and this gives an advantage over natives. Biological control can be effective but is very risky business since it introduces one potentially invasive species to deal with another, sometimes with really dire consequences (e.g. mosquito fish, apple snail, cane toad).
As it happens, there is currently a plan in motion to license the import and release of a biocontrol beetle for garlic mustard, so it is quite relevant to our study. Biological control today is a lot more cautious than it has been historically, but there will always be a large amount of uncertainty without more detailed data of the type we are seeking. If garlic mustard populations in Europe and North America have similar abundances, it would suggest that garlic mustard is not heavily controlled by biocontrol agents and therefore biological control would not be an effective strategy. In that case, the risk of introducing a new beetle would probably not be warranted.
On the other hand, if there IS a change in size and density of Garlic Mustard in North America, it suggests that there is something fundamentally different from the native range, but that doesn’t mean that escape from natural enemies is the cause. The next step would be to identify what the cause: perhaps herbivores, perhaps allelopathic chemicals, perhaps genetics, perhaps something else.
More importantly, the abundance of Garlic Mustard is variable throughout North America and Europe, even for populations that have been established for a long time. Understanding why this variation exists could lead to important new insights into the biology of invasive species and ultimately lead to new and more effective control options
The truth is that new discoveries are difficult to predict but can lead to unforeseen management options.