Abstract

Fire and land-use change are two major types of disturbances that strongly affect the structure and function of forest ecosystems around the world, although their impacts can be difficult to quantify due to concomitant changes in climate or other land-use change factors. In this study we examined how fire and subsequent land-use conversion impacted soil properties (i.e. organic matter (OM), total available pools of carbon (C), nitrogen (N), and phosphorous (P)), and processes (i.e. N cycling inferred through delta N-15) in each of six different land cover types, including old- and second-growth native Nothofagus pumilio, similar to 50 year old exotic conifer plantations, and grassland pastures. We selected six land cover types, including unburned old-growth (MF), and post-fire second-growth (SG) forests of N. pumilio, post-fire afforestations of Pinus contorta (PC), P. ponderosa (PP) and P. sylvestris (PS), and post-fire grassland (GR), in three watersheds in the Aysen Region, Chilean Patagonia. In one growing season, at each of 5-7 sampling locations within each site, two 10 cm deep soil cores were removed using a 12.4 cm diameter PVC soil-corer. From each soil core, organic matter content, total C and N concentrations, availability of NH4+, NO3-, and PO4-, and delta N-15 were determined. Additionally, we collected foliage of Osmorhiza chilensis, a forb that was present in every tree-cover condition, for delta N-15 determination. Unburned old-growth Nothofagus forests showed significantly higher stocks of OM, C, N and P than the P. contorta and P. sylvestris afforestations but not higher than Nothofagus second-growth forests and P. ponderosa afforestations. Conifer afforestations showed significantly lower NH4+ values than unburned Nothofagus forests, whereas no differences in NO3- were found among the land cover types. Contrary to expectations, conifer afforestations showed significantly higher plant and soil delta N-15 values than the unburned Nothofagus forests. Although most land cover types resulted in significant alteration of soil properties and processes relative to the mature, unburned N. pumilio forests, we highlight that P. ponderosa afforestations generated the most similar characteristics, suggesting a utility of this species to restore some ecosystem properties. (C) 2015 Elsevier B.V. All rights reserved.

Keywords

Forest fires; Mineral N; Natural abundance delta N-15; Nothofagus pumilio; Osmorhiza chilensis; Stable isotopes; Temperate forest

Published in

Forest Ecology and Management
2015, Volume: 357, pages: 60-67
Publisher: Elsevier

SLU Authors

• Gundale, Michael

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

SDG15 Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss


UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1016/j.foreco.2015.08.012

Permanent link to this page (URI)

https://res.slu.se/id/publ/68445