1. Introduction
Global forests are changing rapidly to produce fiber, food and other
products (Hansen et al., 2013). Despite their central relevance to
global sustainability goals and ecosystem services, including water
provision and streamflow regulation, natural forests are being lost in
many regions of the world including South America (Creed & van
Noordwijk, 2018; Creed et al., 2019; Jones et al., 2017; Paquette &
Messier, 2010). Temperate rainforests of south central Chile are a
global biodiversity hotspot containing highly threatened endemic species
(Olson & Dinerstein, 1998). Since 1974, much of the area of native
forests in central Chile has been converted to fast growing plantations
of exotic Pinus radiata and Eucalyptus species, or to
shrublands, agriculture and pastureland (Aguayo, Pauchard, Azócar, &
Parra, 2009; Echeverría et al., 2006; Miranda, Altamirano, Cayuela,
Lara, & González, 2016). These changes have been associated with
declining annual and summer runoff in small and large catchments (Lara
et al., 2009; Little, Lara, McPhee, & Urrutia, 2009; Iroumé &
Palacios, 2013) as well as reduced plant diversity (Altamirano,
Echeverría, & Lara, 2007) and carbon storage (Hall, van Holt, Daniels,
Balthazar, & Lambin, 2012; Heilmayr, Echeverría, & Lambin, 2020).
Ecological restoration aims to increase biodiversity and increase the
provision of diverse ecosystem services (Benayas, Newton, Diaz, &
Bullock, 2009). Ecological restoration is defined as the process of
assisting the recovery of an ecosystem that has been degraded, damaged
or destroyed (Gann et al., 2019). Restoration efforts attempt to
increase native forest cover, species diversity, ecosystem
functionality, and ecosystem services such as water provision and
regulation (Little & Lara 2010; Clewell & Aronson, 2013). Functional
ecological restoration includes efforts specifically targeted at
restoring critical structural ecosystem features such as native
vegetation, and ecological processes such as nutrient dynamics (Palmer,
Hondula, & Koch, 2014).
Ecological restoration is distinct from afforestation, but these two
contrasting concepts are sometimes confused in the hydrological
literature. Afforestation with fast-growing species has been linked to
adverse hydrologic effects such as reduced streamflow (Farley, Jobbágy,
& Jackson, 2005; Filoso, Bezerra, Weiss, & Palmer, 2017) and
groundwater (Lu, Zhao, Shi, & Cao, 2018). In contrast, the restoration
of native vegetation is intended to restore forest hydrology. For
example, native forest restoration was associated with increased soil
moisture and water table levels and increased forest biodiversity,
including plants, fungi, and lichens (Mazziotta et al., 2016).
This study addresses a gap in knowledge about hydrologic response to
forest restoration. We describe a 14-year (2006 to 2019) catchment study
to determine how streamflow responded to the first nine years of a 130
to 180-year forest restoration experiment (Lara, Little, González, &
Lobos, 2013). After five years of pre-treatment streamflow measurements,Eucalyptus globulus plantations were clear-cut in 2011.
Restoration was initiated by this clearcut, followed by planting
seedlings of native Nothofagus dombeyi tree species and fostering
regeneration of other native species. The study is located in the
Valdivian Coastal Reserve in south central Chile, a Nature Conservancy
(TNC) reserve on former private industrial forest land. This study is
one of the longest catchment experiments in South America, and to our
knowledge, the only one involving a long-term effort to restore native
forests on land formerly in short-rotation intensively managed forest
plantations.
This study addressed the following questions:
- How did streamflow respond to restoration of native forest in formerEucalyptus plantations?
- How has native vegetation changed in catchments under restoration?
- What factors explain variation in streamflow response?