Stock, turnover and functions of carbon in heavily weathered soils under lowland rainforest transformation systems

DFG . 2012-2015 . SFB SonderForschungsBereich: Sumatra
Thomas Guillaume, Yakov Kuzyakov

Organic carbon (Corg) is an important fertility parameter especially inhighly weathered soils of tropical rainforests such as Acrisols. Two contrasting processes contribute to fast turnover of C in highly weathered soils: i) fast litter decomposition undercontinuously warm and wet conditions leading to high DOM production, and ii) high amount of Fe3+ and Al3+ oxides absorbing C and especially
dissolved organic matter (DOM) in upper and deep horizons. We hypothesize that transformation of lowland rainforest to jungle rubber, oil palm and rubber plantations changes not only quantity and quality of C input (B04), but also the water consumption by vegetation (A02) and consequently DOM production (this SP). This leads to changes of quality, turnover and stocks of C and so, of soil fertility
and functions.
We will evaluate not only the C budget: C input (A06, B04), output of DOM and CO2(A03, A05) and stocks of C in soils, but will especially focus on DOM sorption by Fe3+ and Al3+oxides and the stability of the C in soil aggregates. C turnover under four land use systems will be evaluated by ∆14C and related to prehistoric and historic rainforest transformations (A01) and will be compared with
decomposition rates of C from different depths analyzed in incubation studies. Different plant genetic diversity (B03) will lead to changed C input quality (A06, B04) and consequently quality of soil C with consequences for functional diversity of soil prokaryotes (B02) and fungi (B07), macro-invertebrate communities (B01) and decomposers (B08) evaluated by enzyme activities (thisSP). Scaling of soil C stocks (B05) and fertility pattern will allow socioeconomic conclusions considering functional changes of soil fertility and estimation of the smallholderfarmers’ welfare (C07), poverty dynamics (C04) and cultural landscape transformations (C02).

Oil-Palm plantation