Plants are a lot like animals, just slower. Both plants and animals move around on the landscape, and both need to move through landscapes that have experienced fragmentation. There has been a lot of interest in how habitat fragmentation affects plants, and how they can move long distances as a response to the rapid changes that our world is currently undergoing. Past work shows that some of these long-distance dispersal patterns do make use of habitat corridors, though how effective these corridors are depends on what is helping the seeds to move.
Warneke, C.R., Caughlin, T.T., Damschen, E.I., Haddad, N.M., Levey, D.J. and Brudvig, L.A. 2022. Habitat fragmentation alters the distance of abiotic seed dispersal through edge effects and direction of dispersal. Ecology 103(2): e03586.
Despite the importance of long-distance dispersal events, most seeds remain very close to the parent. (As they say, the apple doesn’t fall far from the tree!) Because most seeds stay relatively close, understanding how and why patterns of seed dispersal may differ in a landscape context can be important in understanding how those plant populations are doing. It can also help forecast things like plant migration rates and, in conjunction with other data, how seeds might eventually grow to be happy adult plants.
To better understand how habitat fragmentation affects seed dispersal, we looked at what happens to short-distance seed dispersal across a set of experimental landscapes at the Savannah River Site Corridor Experiment. We restored plantation forest to an herbaceous-dominated savanna habitat in carefully-designed habitat patches to enable us to ask specific questions about habitat shape and connectivity.
We found that habitat fragmentation does affect short distance seed dispersal. In the five species we looked at, more than 90% of the seeds that we recovered were within two meters of their parent. Interestingly, for most of our study species, landscape connectivity didn’t affect patterns of seed dispersal. Generally speaking, connectivity by corridors can be helpful in facilitating long-distance seed dispersal. We suspect our result is due to slightly different processes that are in play at large vs. local scales. For wind dispersed species such as ours, wind at higher levels above the surface of the ground may move seeds both more in and through corridors. However, this kind of dispersal would have been lost from our data set, as any seeds doing that would have traveled farther than we were able to search for them.
What we do see in our data is an effect of edges. We know from past research that when wind enters an open area after passing over the forest canopy, it has an eddy that goes back towards the forest edge. This happens relatively close to the ground surface – exactly where our plants are. We found that the seeds dispersed further when the seeds were moving towards the edges of our patches. We also found that seeds move greater distances in areas with higher wind speed, which makes intuitive sense as well.
Overall, our results show that, even at small scales, habitat fragmentation can change how seeds move around. Because so much of the reproductive output of a given plant stays close to that plant, even these small-scale differences can be important for how those plant populations change over time. After all, you can’t have new plants without seeds getting there first.
Related Posts
Connectivity and habitat edges affect multiple plant-arthropod interactions
Experimental habitat corridors in a fragmented longleaf pine ecosystem reveal the complexity of interactions between plants and their associated pollinators, florivores, and spiders.
Habitat fragmentation and edges matter for soil microorganisms
New research reveals the significant impact of fragmented habitat on bacteria and fungi in the soil, which provide key ecosystem services but are rarely studied in such a context.
Fragmentation limits the natural regeneration of tropical forests
Recent simulations quantify how much the degree of forest fragmentation influences the ability of frugivorous birds to disperse seeds into open areas.
