Tree biomass equations for tropical peat swamp forest ecosystems in Indonesia Solichin Manuri a,⇑ , Cris Brack a , Nunung Puji Nugroho b , Kristell Hergoualc’h c , Nisa Novita d , Helmut Dotzauer e , Louis Verchot d , Chandra Agung Septiadi Putra f , Eka Widyasari g a Fenner School of Environment and Society, The Australian National University, Linnaeus way Building 48, Acton, Canberra 0200, Australia b Research Institute for Forestry Technology on Watershed Management, Jl. Jenderal Ahmad Yani, P.O. Box 295, Pabelan, Kartasura, Surakarta 57102, Indonesia c Center for International Forestry Research (CIFOR) c/o Centro International de la Papa (CIP), Av. La Molina 1895, La Molina, Apdo postal 1558, 15024 Lima, Peru d Center for International Forestry Research (CIFOR), Jl. CIFOR, Situ Gede, Bogor 16115, Indonesia e Forests and Climate Change Programe, Deutsche Gesellschaft für Internationale Zusammenarbeit (FORCLIME-GIZ), Manggala Wanabakti Building, Block VII, 6th floor, Jakarta, Indonesia f Tropical Forest Foundation (TFF), Komplek Cimanggu Permai, Jl. Tumapel Block O, IV No 17, Bogor 16164, Indonesia g Faculty of Forestry, Bogor Agricultural University, Dramaga Bogor, Indonesia article info Article history: Received 20 June 2014 Received in revised form 22 August 2014 Accepted 27 August 2014 Keywords: Aboveground biomass estimation Destructive sampling Tree allometry Wood density Species grouping REDD+ abstract To assist countries to reduce emissions from deforestation and forest degradation, the United Nations has introduced the REDD+ mechanism. This performance-based incentive mechanism requires accurate quantification of carbon stock and emissions. However, currently there are limited existing local or regio- nal equations for estimating aboveground biomass in peat swamp forests. The main objective of this study was to define the most accurate models for aboveground biomass estimation in Indonesian peat swamp forests. We found that the pan-tropical equations performed better in estimating biomass of peat swamp forests than did existing local equations. We developed new equations, based on 148 trees from 24 families with diameter at breast height in the range of 2–167 cm collected from peat swamp forests in the western part of Indonesia. Statistical indicators showed that the best model form was the common linear one using log-transformed data. Estimated biomass values needs to be back-transformed applying correction factors. The ratio estimator correction factor which derives from the ratio between the average of measured biomass and the average of predicted biomass, was found to provide the lowest mean devi- ation. The existing pan-tropical equations performed similarly to our mixed species and dipterocarp models but they systematically under- or over-estimated the biomass of certain species groups, espe- cially non-dipterocarp trees. We also found that grouping by family (dipterocarp vs. non-dipterocarp) and wood density class (hardwood vs. softwood) significantly improved the accuracy of biomass estima- tion. In the absence of wood density values, wood density-class specific equations, instead of mixed-spe- cies equations improved the accuracy of biomass estimates. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Greenhouse gas emissions from land use, land-use change and forestry (LULUCF) account for about 12.5% of global emissions (Baccini et al., 2012; Houghton et al., 2012). In Indonesia, this sector represents 47% of national emissions and emissions from peat fires an additional 13% (Ministry of Environment, 2010). Peat swamp for- ests (PSF) in particular suffered intensive deforestation in Indonesia between 1990 and 2010 with around 4.6 million hectares being cleared out of the 1990 8.7 million hectares (Miettinen et al., 2011). In 2011, only 31% of Indonesian PSF were still in pristine con- dition (Ministry of Forestry, 2012). Peat swamp forest are carbon- rich ecosystems (Jaenicke et al., 2008) which store on average 220 Mg C ha 1 in the phytomass (Hergoualc’h and Verchot, 2011) and 670 Mg C ha 1 per meter depth of peat (Warren et al., 2012). Deforestation of PSF and drainage for cultivation of agricultural crops involve major shifts in the carbon and nitrogen cycles leading to substantial greenhouse gas emissions; especially when land- clearing fires are used (Hergoualc’h and Verchot, 2014). Peat swamp forests could hence play a potentially important role in climate change mitigation strategies involving forest conservation. In 2005, a mechanism for reducing emissions from deforestation and forest degradation (REDD) was discussed at the 11th annual Conference of the Parties from the United Nations Framework http://dx.doi.org/10.1016/j.foreco.2014.08.031 0378-1127/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +61 2 6125 4588; fax: +61 2 6125 0651. E-mail addresses: solichin.solichin@anu.edu.au, solichin.manuri@gmail.com (S. Manuri). Forest Ecology and Management 334 (2014) 241–253 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco