F1000 January review: Science can be practical!

Its always nice to find an example of where a great scientific theory can be tested and prove useful!  In this case, ideas about how timing of watering regimes can give a phenological advantage to invaders but could then also be manipulated to give a disadvantage and so suppress invading populations.  Ideas like this have existed in weed control in agriculture for a long time, but its interesting to see this kind of thinking emerging in a new context.

Wainwright CE, Wolkovich EM, Cleland EE (2011) Seasonal priority effects: implications for invasion and restoration in a semi-arid system. J App Ecol. 49:234-41

Our review:

Parry H, Lonsdale M: 2012. http://f1000.com/13480958

This is a good example of hypothesis-driven research in invasion ecology. A concept of phenologically driven seasonal ‘priority advantage’ is introduced, which can be used to explain the success of an invasive species. Having shown that the concept is applicable to exotic annual grasses in California, the authors go a step further and show how an understanding of phenology can be a powerful weapon in restoring invaded ecosystems.

The paper provides experimental evidence that earlier establishment of exotic seedlings under a normal watering regime gives them a ‘priority advantage’. The ‘priority advantage’ is turned into a ‘priority disadvantage’ for the invader when an early season watering regime is introduced. This stimulates early germination of the invasive before true growing season rains, resulting in reduced survival throughout the season as the early seedlings die and a depleted seed bank for later germination. The possibility that this can be used to manage the invader is posed – a suggestion foreshadowed by an older literature for agronomic weeds on the manipulation of the seed bank [1]. However, the study does not isolate the direct effects of phenology and environmental stress from other factors, such as the presence of herbivores; the authors argue that the herbivores simply act to augment the stress impacts of the early season watering strategy and are simply a component of the ‘priority disadvantage’. To implement such a management strategy for vegetation in reality, not only the water regime but also the presence of herbivores should likely be optimised. 

[1] Egley GH, Rev Weed Sci 1986, 2:67-89