Herbivory may mediate the effects of nutrient fluctuations on plant invasion

Yanjun Li, Yingzhi Gao, Mark van Kleunen, Yanjie Liu

This is a plain language summary of a Functional Ecology research article which is published here.

Overview of plants grown in the cage with grasshoppers. PLS photo credit: Liu lab (www.plantecology.cn/)
Overview of plants grown in the cage with grasshoppers. PLS photo credit: Liu lab (www.plantecology.cn/)

It is frequently assumed that environmental variability could promote alien plant invasion, because the fluctuating resource hypothesis predicts that habitats with increased variability in resource availability will be more easily invaded than those with less variable resource conditions. Many studies have tested this hypothesis, but have found mixed results. Thus, more studies are needed to test the hypothesis, and why the results might vary.

Most of the previous studies that tested effects of nutrient fluctuations on alien plant invasion were conducted under overall nutrient-rich conditions. Under more nutrient-limiting conditions, however, the effect of temporal fluctuations may be even stronger due to the stronger competition between alien and native plants. Still, very few studies have tested whether this expectation holds.

Moreover, previous tests only used study systems consisting of a single trophic level (i.e., only considered plant-plant interactions). Plant growth, however, can be strongly regulated by other trophic levels, such as herbivores. This might also be relevant for the fluctuating resource hypothesis as alien species are likely to be released from most of their native enemies, and thus should suffer less herbivory than native species in their introduced regions.

To test the individual effects of nutrient availability, nutrient fluctuations, herbivory, and their interactions on alien plant invasion into resident communities, we carried out a multi-trophic multi-species experiment. We grew eight invasive alien species in pot-mesocosms with five different synthetic native communities, and exposed the plants to eight combinations of nutrient availability (low vs high), nutrient-fluctuation (constant vs pulsed) and herbivory (with vs without herbivores) treatments.

Our results, partly in line with the fluctuating resource hypothesis, showed that nutrient fluctuation promotes alien plant invasion only under overall low-nutrient conditions, and only in the absence of herbivores. Therefore, we conclude that other trophic levels, such as herbivores in our study, might mediate the interactive effect of nutrient enrichment on alien plant invasion into resident communities.

Advertisement

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s