A cost-efficient method to assess carbon stocks in tropical peat soil

M W Warren,D Murdiyarso,G Anshari,S Limin,J Rahajoe,K Hergoualc'H,M Afifudin,A Iswandi,J B Kauffman,J Purbopuspito,S Kurnianto,E Gusmayanti,L Alhamd

doi:10.5194/bg-9-4477-2012

Abstract

Abstract. Estimation of belowground carbon stocks in tropical wetland forests requires funding for laboratory analyses and suitable facilities, which are often lacking in developing nations where most tropical wetlands are found. It is therefore beneficial to develop simple analytical tools to assist belowground carbon estimation where financial and technical limitations are common. Here we use published and original data to describe soil carbon density (kgC m−3; Cd) as a function of bulk density (gC cm−3; Bd), which can be used to rapidly estimate belowground carbon storage using Bd measurements only. Predicted carbon densities and stocks are compared with those obtained from direct carbon analysis for ten peat swamp forest stands in three national parks of Indonesia. Analysis of soil carbon density and bulk density from the literature indicated a strong linear relationship (Cd = Bd × 495.14 + 5.41, R2 = 0.93, n = 151) for soils with organic C content > 40%. As organic C content decreases, the relationship between Cd and Bd becomes less predictable as soil texture becomes an important determinant of Cd. The equation predicted belowground C stocks to within 0.92% to 9.57% of observed values. Average bulk density of collected peat samples was 0.127 g cm−3, which is in the upper range of previous reports for Southeast Asian peatlands. When original data were included, the revised equation Cd = Bd × 468.76 + 5.82, with R2 = 0.95 and n = 712, was slightly below the lower 95% confidence interval of the original equation, and tended to decrease Cd estimates. We recommend this last equation for a rapid estimation of soil C stocks for well-developed peat soils where C content > 40%.

Highlights

Tropical wetland forests containing organic soils – mangroves and freshwater peat swamps – are significant global carbon (C) stores (Donato et al, 2011). Page et al (2011) estimated 88.6 PgC are stored in tropical peatlands worldwide, with 68.5 PgC (77 %) occurring in Southeast Asia
A total of 151 values for bulk density, C density, and C concentration were available in the literature for tropical wetland soils and met our criteria (Table 1)
Data included in the analysis span numerous sites, organic soil types, and land uses throughout Indonesia and three Peruvian sites

Summary

Introduction

Tropical wetland forests containing organic soils – mangroves and freshwater peat swamps – are significant global carbon (C) stores (Donato et al, 2011). Page et al (2011) estimated 88.6 PgC are stored in tropical peatlands worldwide, with 68.5 PgC (77 %) occurring in Southeast Asia. Tropical wetland forests containing organic soils – mangroves and freshwater peat swamps – are significant global carbon (C) stores (Donato et al, 2011). Page et al (2011) estimated 88.6 PgC are stored in tropical peatlands worldwide, with 68.5 PgC (77 %) occurring in Southeast Asia. Donato et al (2011) estimated mangroves may contain up to 20 PgC globally. Warren et al.: A cost-efficient method to assess carbon stocks in tropical peat soil rapid rates of deforestation (Langner et al, 2007; Miettinen and Liew, 2010a, b). Of further concern is the vulnerability of tropical wetland C pools exacerbated by predicted consequences of global climate change: ENSO-related droughts and subsequent fires, altered precipitation patterns, increasing frequency and severity of tropical cyclones and sea level rise (Ellison and Stoddart, 1991; Li et al, 2007; Field et al, 2009)

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