Forest Soils under Alternatives to Slash and Burn Agriculture in Sumatra, Indonesia

Abstract

A global projecl on 'Allefnatives lo Slash and Burn'agricullure was initialed by a consorlium of inlernalional and nalional research inslilules lo lacili lale inlensilicalion 01 Ihe use 01 converted loresl land, in order lo help alleviale poverly and prolecl Ihe remaining loresl areas lor lheir biodivcrsil) values dnd their role in miligaliny greenhouse gas emissions. Dala lor Ihe Indonesian benchmark areas in Ihe lowland peneplain, piedmonl and mounlain zone 01 Sumalra are presenled. A sigrtilicanl ainounl oi loresl land, especially in Ihe lowland peneplain, has been converted in lhe lasl len years inlo agricullural use, usually lollowing logging concessiorls Soils on Ihe peneplain are poor (oxi- and ullisols) and currenl inlensive crop based produclion syslems are no1 suslainable. In Ihe piedrnonl zone or beller soils (inceplisols), rubber agroloresls (slill) characterize Ihe area. Agroloresls have emerged during the 20'lh century 2s Ihe major allcrnalivc Ir slash-and-burn agriculture, based on a shill 01 emphasis from food crops lo cash-earning lree crops. Emphasis on food crops, however. continues ir government reselllemenl schemes. Dillerences in organic C conlenl 01 Ihe lopsoil between loresls and crop land are aboul 0.5% C, wilh agroloresls and lree crop planlalions in nr inlermediale posi1ion.A new size-density lraclionation scheme lor soil organic matter demonstrated larger changes in light and inlerrnediatc Irac(ions Foresl soils can be signilicanl sinks lor methane and thus partly compensale lor Ihe methane emissions in lowland rice produclion Overall, the Sumalra benchmark areas dernot~slraleIh e need lo combine inlensilicalion of land use al Ihe lieldlhousehold level wilh elleclivc prolcc lion 01 remaining loresl areas al the communily level and reducing other driving forces of deloreslalion al Ihe nalional level.