Save the Tree ... seeds

On Aug 21st the Thetford Conservation Commission was pleased to host a presentation by Brooke Fleischman from the Riparian Lands Seed Partnership (RLSP). Brooke was in Thetford to introduce the work of this new organization which became active in 2022.  In a nutshell, their goals are to restore floodplains in Vermont by repopulating them with native, locally adapted tree species to regenerate floodplain forests. 

River floodplains, as their name indicates, are inundated on a regular basis, temporarily storing floodwaters and providing relief to downstream lands. A floodplain that is forested traps silt and reduces the erosive energy of floodwaters because, to quote Greg Russ, the watershed restoration manager of White River Partnership, "trees are the speedbumps that slow floodwaters down." Prior to the arrival of European colonizers, Vermont had extensive floodplain forests of towering silver maples and other trees adapted to regular inundation and siltation. In the 1700s and early 1800s, the vast majority of these forests were cleared for agriculture, and only fragments remain. However, there is a new urgency today to mitigate flood damage, and the state is actively searching for floodplains to restore.

The mission of the RLSP is "to develop a statewide partnership of organizations that work together to meet the need for local, native tree and shrub seeds for restoration projects that support climate mitigation, water quality, and healthy habitats." Because the number of trees needed is potentially enormous, their approach is to collect the seeds of the appropriate woody plants on a large scale, and then process and store them for distribution. They are performing experiments to determine if direct seeding into the ground is an effective approach for large-scale floodplain forest restoration. To seek out sources of seeds, they are reaching out to organizations like conservation commissions and community members to assist by scouting out locations of target species. RLSP is also educating those groups on best practices for seed handling.

The RLSP currently works with a range of groups, with the core being the Intervale Center, NorthWoods Stewardship Center, Vermont Fish & Wildlife, and U.S. Fish & Wildlife. 

Saving seeds sounds straightforward, but there's more to it than meets the eye. It is desirable to repopulate a natural forest with trees not only of the appropriate species but also of the local "ecotype." For example, the species silver maple grows throughout the eastern US, parts of the midwest, and southern Canada. But a local ecotype of silver maple is a subset of the species that has adapted to a specific geographic environment and, as a result, has evolved to be genetically distinct from members of the same species from other environments. Seed collectors must also distinguish true wildtypes from cultivated selections of the same native species. Brooke demonstrated a case in point: cultivated vs native highbush cranberry. The distinction is subtle. The leaf stems of the native bush (Viburnum opulus var. opulus) sport a pair of tiny, cup-shaped glands, whereas the cultivar (Viburnum opulus var. americanum) has multiple tiny glands. For this reason, seed collection should be from natural areas, preserves, and conserved lands, rather that parks and other cultivated areas. RLSP does not perform genetic testing on collected materials.

Collecting shouldn't occur in the same places for more than two years, according to Seeds of Success, the Bureau of Land Management's program, that lays out national standards for the collection, conservation, and study of seeds from native species. Thus, significant time must be devoted to an ongoing search for new locations. The small band of workers at RLSP has already spent 200 hours this year scouting for more sites.

Another proviso is ethical collecting of seed. No more than 20% of the available seed should be taken from any site. Over-collecting deprives wildlife of needed forage. And seed should not be taken without permission. RLSP has an agreement with the state to collect on state-owned land, but needs permission to do the same on private lands.

A familiarity with the seed-bearing season of the target species is also important. For some trees, seed progression happens rapidly in the spring. Aspen and american elm produce seeds in May, while silver maple spills over into June. Service berry also offers its red fruits in June (hence its other name, Juneberry), while other fleshy seeds like chokecherry and dogwoods extend from July into August, even September. 

Because tracking phenology is a significant aspect of this project, seed scouts are asked to record data, including GIS coordinates of the site, the date, the tree or plant height, its stage of seed development, surrounding land use (recreational, agricultural, conserved etc.), and what other species were present (native and invasive plants, woody and herbaceous). Citizens can also register records on iNaturalist, importantly with a photo. 

The tools for seed collection are quite basic — buckets, bags, ladders, and pruners or pole pruners. Collection should be spread randomly throughout the location, taking no more than 20% of what's there. Again, recording who collected and how, where, and the time it took are all data important to the science of the project.

At its headquarters at the Intervale Nursery, RLSP has various techniques for separating the actual seeds from the cones, fruits, bracts, stems, and other accompanying structures. Pulpy seeds are macerated with water in something like a giant blender and the seeds separated on a screen. Fluffy seeds are subjected to blasts of compressed air in The Tornado, till the seeds detach and fall away from the fluff. An expensive machine called The Clipper is needed to break up cones of birch, tamarack, pine, etc. and vibrate and blow the material till the seeds fall away.

So far the data to show whether mass seeding can restore floodplains has been delayed due to flooding. The nursery at Intervale was flooded last July and again in December. All the associated floodplain sites that had received millions of seeds were also flooded, and Brooke assumes that they are a loss. Nevertheless, this program, the only one of its kind in the US, is forging ahead and hoping for assistance from Conservation Commissions and citizens. They will be holding another event about saving tree seeds at Cedar Circle Farm and Education Center in East Thetford on October 6th.

Photo credit Li Shen