Kobayashi Makoto and Scott Wilson recently had a mini-review article published in Journal of Ecology about dispersal limitation and primary succession. Makoto tells us more about the article in his blog post below.

Ultimately, primary succession starts with the dispersal of propagules on to new substrate (Photo 1). However, little is known about where and when dispersal influences the later stages of primary succession and accompanying ecosystem development.

In our paper for Journal of Ecology, we reviewed the literature on dispersal limitation globally in order to understand when (successional stage) and where (e.g. ecosystem, disturbance type, hemisphere) dispersal influences primary succession.

Photo 1: The glacier foreland in arctic tundra of northern Sweden (a). The bare soil soon after glacier retreat (b, and the white square in Photo 1a) is waiting for the dispersal of propagule from a distant seed source (Photo: Kobayashi Makoto)

When does dispersal limitation matter in primary succession? Studies from many systems (tropical, temperate, arctic, floodplain forest, desert, mines, alpine volcanic lava, alpine) show that dispersal limitation occurs consistently in the early stages of primary succession, suggesting that this is a general pattern. On the other hand, there are exceptions, especially where local conditions include additional disturbance or harsh conditions. For example, in coastal dunes on Lake Michigan, episodic burial of seeds by sand, which occurs in the youngest sites, strongly regulates plant colonization (Lichter, 2000). Similarly, seed predation by mammals or birds determines success in the early stages of some primary successions (Bishop, 2002) suggesting that dispersal importance interacts with trophic interaction.

In addition, we also introduce a novel approach, multi-scale chronosequence comparison, which tests for the long-term (century scale) importance of dispersal during primary succession. This new approach revealed that, at least in arctic tundra, dispersal regulates the rate of primary succession over several centuries (Photo 2). It is easy to imagine that dispersal continues to matter for the rate of primary succession for the long-term, but until recently, this fact has not been confirmed with field evidence.

Photo 2: A vegetation patch dominated by Salix herbacea in arctic glacier foreland. Here the primary succession has been regulated by dispersal limitation over several centuries (Photo: Kobayashi Makoto)

Where does dispersal limitation matter in primary succession? Our literature review found strong biases in study sites towards the northern hemisphere, temperate regions, volcanic eruptions and glacier forelands (Photo 3), which suggests that there are risks in drawing general conclusions about the importance of dispersal for primary succession for other biomes.

Photo 3: Primary succession in Mt. Komagatake in Hokkaido, Japan. A frequently studied research system in volcanic eruption, in a temperate region of northern hemisphere (Photo: Shiro Tsuyuzaki)

The role of dispersal in primary succession is also interesting in the context of climate change, as current climate change is associated with accelerating glacier retreat, creating new forelands for primary succession, and new opportunities for studying mechanisms underlying succession. A recent investigation of a previously studied glacier foreland chronosequence revealed that the current rate of primary succession is faster than it was about 100 years ago, probably due to climate warming (Fickert, Grüninger, & Damm, 2017).

However, the mechanism underlying the acceleration of succession rate is not clear. Somewhat surprisingly, whether the rates of primary succession and its limiting factors will be influenced by climate change has not been tested, but this seems likely given that drivers associated with primary succession (competition between plants, dispersal strategies, wind speed, soil nutrient availability) are climate dependent. The generality or context-dependency of the role of dispersal, and its variation with changing climate, should be addressed in diverse primary successions using multi-scale chronosequence comparisons and factorial manipulation experiments involving dispersal, warming and nutrient addition.

Kobayashi Makoto, Hokkaido University, Japan

Read the full paper online: When and where does dispersal limitation matter in primary succession?