Aboveground and belowground legacies of native Sami land use on boreal forest in northern Sweden 100 years after abandonment

Abstract

Human activities that involve land-use change often cause major transformations to community and ecosystem properties both aboveground and belowground, and when land use is abandoned, these modifications can persist for extended periods. However, the mechanisms responsible for rapid recovery vs. long-term maintenance of ecosystem changes following abandonment remain poorly understood. Here, we examined the long-term ecological effects of two remote former settlements, regularly visited for -300 years by reindeer-herding Sami and abandoned -100 years ago, within an old-growth boreal forest that is considered one of the most pristine regions in northern Scandinavia. These human legacies were assessed through measurements of abiotic and biotic soil properties and vegetation characteristics at the settlement sites and at varying distances from them. Low-intensity land use by Sami is characterized by the transfer of organic matter towards the settlements by humans and reindeer herds, compaction of soil through trampling, disappearance of understory vegetation, and selective cutting of pine trees for fuel and construction. As a consequence, we found a shift towards early successional plant species and a threefold increase in soil microbial activity and nutrient availability close to the settlements relative to away from them. These changes in soil fertility and vegetation contributed to 83% greater total vegetation productivity, 35% greater plant biomass, and 23% and 16% greater concentrations of foliar N and P nearer the settlements, leading to a greater quantity and quality of litter inputs. Because decomposer activity was also 40% greater towards the settlements, soil organic matter cycling and nutrient availability were further increased, leading to likely positive feedbacks between the aboveground and belowground components resulting from historic land use. Although not all of the activities typical of Sami have left visible residual traces on the ecosystem after 100 years, their low-intensity but long-term land use at settlement sites has triggered a rejuvenation of the ecosystem that is still present. Our data demonstrates that aboveground-belowground interactions strongly control ecosystem responses to historical human land use and that medium- to long-term consequences of even low-intensity human activities must be better accounted for if we are to predict and manage ecosystems succession following land-use abandonment.

High-resolution palynology reveals the land use history of a Sami renvall in northern Sweden

“…Contours are at 5 m intervals settlements in the Arjeplog area (*66.1°N 17.9°E; Fig. 1) were proposed by Freschet et al (2014): (1) organic matter deposition, both by the Sami and their herds; (2) soil compaction through trampling; (3) destruction of the field layer; (4) selective felling of Pinus sylvestris for fuel and building purposes. Palynologically, the creation of local openings in the boreal forests of northern Fennoscandia, to provide spaces for dwellings and livestock, is recognizable by a decline in trees (Hicks 1976;Vuorela 1976;Berglund et al 2008).…”

“…These taxa respond positively to increased light levels following clearance, are resistant to soil trampling and typically react positively to the increased soil nutrient levels provided by inputs from reindeer dung, domestic waste and ash from smudge fires. Recovery following the abandonment of disturbed areas is characterised by a general secondary succession whereby the Poaceae-dominated vegetation is replaced first by ericaceous heaths and Betula, then by Pinus and finally by Picea (Bradshaw and Zackrisson 1990;Jonsson and Esseen 1998;Freschet et al 2014). This recovery may take considerably longer than the duration of human impact, grazing activity and the resulting nitrogen enrichment (Walker and Wardle 2014).…”

“…At reindeer herding settlements near Arjeplog (450-550 m a.s.l. ), secondary succession was still underway more than 100 years after abandonment, with the old activity areas forming islands of B. pubescens within the P. sylvestris-dominated forest (Freschet et al 2014). Once the vegetation within the renvall has recovered, it barely stands out from the surrounding forest, and can be recognised only by larger specimens of trees that had been left to provide shade for the reindeer (Ö stlund et al 2003).…”

People and pines 1555–1910: integrating ecology, history and archaeology to assess long-term resource use in northern Fennoscandia

“…in the more heavily populated areas of Europe (Kaplan et al 2009;Ludemann 2010) and elsewhere (Lev-Yadun et al 2010). Although our data suggest that Sami pre-industrial land uses had very weak effects on the availability of specific resources from a landscape perspective, specific case-studies have detected long-lasting local ecosystem effects, such as vegetation changes due to cutting of firewood (Josefsson et al 2010a;Staland et al 2011;Ö stlund et al 2015) and both above-and below-ground feedback effects of trampling and organic matter transfer (Freschet et al 2014). In addition, case studies have also detected strong cultural imprints in local hotspots (Berg et al 2011;Sjögren and Kirchhefer 2012;Rautio et al 2014).…”

“…Areas previously considered as 'natural' landscapes and completely devoid of human impacts have, in fact, shown clear traces of human activities, with prolonged ecosystem effects (Cronon 1983;Krech 1999;Foster et al 2003;Josefsson 2009;Freschet et al 2014). To increase our understanding of human-environment interactions, especially over the long term, the integration of ecology, history and archaeology has been identified as a way forward (Briggs et al 2006;Bürgi et al 2013;Goldewijk and Verburg 2013;Scharf 2014).…”