Antonio Lara

and 3 more

This study presents the results of a long-term paired catchment experiment in south central Chile (mean annual precipitation = 2,500 mm, 5% falling in summer, mean annual temperature = 10 °C) in which fast-growing plantations of exotic Eucalyptus spp. were clearcut and replaced with native temperate rainforest species as part of an ecological restoration project. Precipitation, streamflow, and vegetation were measured starting in 2006 in four small (3 to 5 ha) catchments with Eucalyptus globulus plantations and native riparian buffers in the Valdivian Coastal Reserve. In 2011, the 12-yr-old Eucalyptus plantations were harvested in three catchments, and the clearcut area was planted with native trees (Nothofagus dombeyi), and diverse native forest species regenerated vigorously. In the restoration period (2011 to 2019), annual streamflow increased in average by 21 – 73% compared to the 2006-2010 pre-treatment period, and as much as 100% in wet years and by more than 150% in fall and summer of some years. Streamflow was 50 to 100% lower than before treatment in two dry summers (2014-2015. Base flow increased by 28 to 87% during the restoration period (2011 to 2019) compared to the pre-treatment period, and remained elevated in later years despite low summer precipitation. Streamflow increases persisted through the first decade of restoration. Overall, these findings indicate that removal of Eucalyptus plantations immediately increased streamflow, and native forest restoration gradually restored deep soil moisture reservoirs that sustain base flow during dry periods, and these flows showed steady positive values in the last three years contributing to water provision ecosystem services. The results of this study are relevant to efforts to restore native forest ecosystems on land currently intensively managed fast-growing forest plantations. They also provide useful information to inform policy and decision-making related to options for climate change mitigation under a drying trend in South-central Chile. To our knowledge this study is the first to test streamflow response to native forest restoration in former fast-growing Eucalyptus forest plantations.