Study location and study setup
Our study was located in the boreal region of northern Sweden in two
catchments of similar size (~350 km2):
Hjuksån and Bjurbäcken (ån and bäcken both mean ‘stream’/
‘creek’), both of which are tributaries of the free-flowing Vindel River
that in turn flows into the Ume River ~30 km upstream of
its outlet in the Baltic Sea (Figure 2). In addition to glaciation
shaping the catchment through numerous mainstem lakes and large amounts
of coarse glacial sediment, the landscape is divided into two
regions—above and below the former highest coast-line (FHC). The FHC
divides areas that have been only affected by glaciation and contains
undisturbed glacial sediment from areas that have been under sea level
after glaciation and affected by deltaic processes and subsequently
uplifted by post-glacial isostatic rebound (Fredén, 1994). Hjuksån
catchment (64° 25’N, 19° 45’E, alt. 245 m) is located nearly entirely
below the FHC, whereas Bjurbäcken (65° 6’N, 18° 4’E, alt. 320 m) is
completely above the FHC. The upland vegetation in the study area is
dominated by boreal forest with Scots pine (Pinus sylvestris ) and
Norway spruce (Picea abies ) and the riparian vegetation is
dominated by deciduous trees, tall herb, and graminoid communities.
We started collecting geomorphic and ecological data directly downstream
of the furthest upstream lake, encompassing 18 process domain reaches in
Bjurbäcken and 20 process domain reaches in Hjuksån catchment.
Geomorphic data were collected along the entire mainstem channel of
Bjurbäcken and Hjuksån, starting below the upstream lake, to the
tributary junction with the Vindel River. Riparian vegetation data were
collected starting at the same point and ~18 km
downstream in Bjurbäcken and ~9 km downstream in
Hjuksån.