Buffer effects of streamside native forests on water provision in watersheds dominated by exotic forest plantations

AbstractThe Valdivian rainforest ecoregion in Chile (35°–48°S) has a high conservation priority worldwide. These forests are also keys for social welfare as a result of their supply of timber as well as ecosystem services. Forests in the ecoregion have been extensively converted to fast growing Pinus radiata and Eucalyptus spp. plantations for timber production promoted by public policies and timber companies. This study describes the results of detailed measurements of hydrology and stream water chemistry in eight small watersheds in south central Chile, subjected to replacement of native temperate rainforest by exotic Eucalyptus plantations. In this system, watersheds have streamside buffers of native forest (SNFW) with varying widths. Results indicate that retention of SNFW counteracts hydrologic effects of Eucalyptus plantations, which are widely known to reduce water yields. A 1.4% rate of increase of the run‐off coefficient for each metre of increase of SNFW was observed. In addition, a decrease in the concentrations of total nitrogen, dissolved inorganic nitrogen (DIN), nitrate‐N, and different sized fractions of particulate organic matter were found in streams draining these plantations as a function of increasing SNFW. Streamside buffer widths of 17–22 m for total nitrogen and DIN concentrations and ≥36 m for sediments were required to provide comparable values to reference watersheds (100% native forest). The findings from this study suggest that SNFW may significantly reduce adverse effects from exotic species forestry plantations on water provision in an area of south central Chile where exotic forest plantations are rapidly expanding. Copyright © 2014 John Wiley & Sons, Ltd.