The spruce-buffer syndrome: should we prioritize deciduous trees in riparian buffer zones of boreal streams?

Stream-side (riparian) buffer zones are among our best tools for reducing the unwanted environmental effects of land use on freshwater ecosystems.

Riparian forest buffers filter nutrients and sediments from upland soils, regulate stream physical conditions, and provide organic matter that support aquatic food webs. Yet, the overall effectiveness of buffer zones varies base on how they are designed.

In Sweden, one recent policy suggestion for improved buffer functioning is to prioritize a greater abundance of broadleaf trees (e.g., birch) along our waterways instead of coniferous species (e.g., spruce).

While there may be good reasons to increase the ‘deciduousness’ of riparian zones, there are no systematic tests that evaluate the costs/benefits of such an action in the Swedish landscape. Without this evidence, it is difficult to push forward clear sets of recommendations to public and private landowners.

To advance riparian buffer management in the boreal landscape, we will use a series observational and experimental approaches to test how broadleaf trees influence nitrogen retention at the land-water interface, enhance a range of stream ecosystem processes, and promote productive aquatic food-webs.

Synthesis of our results will be used to inform a new generation of buffer designs in the Swedish landscape.