1. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå SE-90183, Sweden
2. School of Resources & Environment, Nanchang University, Nanchang 330031, China
3. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala SE-75651, Sweden
4. Institute of Geography and Oeschger Center for Climate Change Research, University of Bern, Bern 3012, Switzerland
5. Department of Chemistry, Umeå University, Umeå SE-901 87, Sweden