Carbon neutral? No change in mineral soil carbon stock under oil palm plantations derived from forest or non-forest in Indonesia

Abstract

A B S T R A C TSustainability criteria for palm oil production guide new planting toward non-forest land cover on mineral soil, avoiding carbon debts caused by forest and peat conversion. Effects on soil carbon stock (soil C stock ) of land use change trajectories from forest and non-forest to oil palm on mineral soils include initial decline and subsequent recovery, however modeling efforts and life-cycle accounting are constrained by lack of comprehensive data sets; only few case studies underpin current debate. We analyzed soil C stock (Mg ha À1 ), soil bulk density (BD, g cm À3 ) and soil organic carbon concentration (C org , %) from 155 plots in 20 oil palm plantations across the major production areas of Indonesia, identifying trends during a production cycle on 6 plantations with sufficient spread in plot age. Plots were sampled in four management zones: weeded circle (WC), interrow (IR), frond stacks (FS), and harvest paths (HP); three depth intervals 0-5, 5-15 and 15-30 cm were sampled in each zone. Compared to the initial condition, increases in C org (16.2%) and reduction in BD (8.9%) in the FS zone, was compensated by decrease in C org (21.4%) and increase in BD (6.6%) in the HP zone, with intermediate results elsewhere. For a weighted average of the four management zones and after correction for equal mineral soil basis, the net temporal trend in soil C stock in the top 30 cm of soil across all data was not significantly different from zero in both forest-and non-forest-derived oil palm plantations. Individual plantations experienced net decline, net increase or U-shaped trajectories. The 2% difference in mean soil C stock in forest and nonforest derived oil palm plantations was statistically significant (p < 0.05). Unless soil management changes strongly from current practice, it is appropriate for C footprint calculations to assume soil C stock neutrality on mineral soils used for oil palm cultivation. 2015 Z. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Effects of Depth and Land Cover on Soil Properties as Indicated by Carbon and Nitrogen-Stable Isotope Analysis

“…This is consistent with the results of the study by [48][49], who reported that the SOC content increased over time under oil palm plantation. Furthermore, lack of differences between secondary forest and oil palm plantation aged 15 years had also been demonstrated by other investigators [15,50]. When the rubber and oil palm aged 5 years were compared, a similar lack of differences in TOC were also demonstrated in the study by [51].…”

“…This study suggested that the reason why the secondary forest has signifi cantly higher TOC content than the rubber and oil palm plantation aged 5 years may be due to the differences in pH values between the locations. The lower TOC content exhibited by the subsoil was also reported by [15,53]. However, it may be possible that the minimum loss of TOC content after conversion of the secondary forest to plantation may be attributable to the high clay content found in the study area.…”

“…In contrast, others reported a net gain of carbon [13][14][15]. Recent studies on SOC storage and turnover have employed the evaluation of 13 C and 15 N natural abundances as a technique to determine changes in C and N dynamics in relation to land use/land cover changes [16][17][18]. For instance, stable C and N isotopes have been previously employed to gain knowledge of the mechanisms of plant litter decay, SOM evolution, and turnover [19][20][21], to understand the sources of organic carbon [19][20][21][22], the origins of soil N among different ecosystems or soil disturbances as a result of change in land use [18,[23][24], and nitrogen cycling and mineralization [25][26].…”

“…In contrast, others reported a net gain of carbon [13][14][15]. Recent studies on SOC storage and turnover have employed the evaluation of 13 C and 15 N natural abundances as a technique to determine changes in C and N dynamics in relation to land use/land cover changes [16][17][18].…”

Carbon Stocks across a Fifty Year Chronosequence of Rubber Plantations in Tropical China

“…Although soil C generally is expected to decrease due to soil disturbance and aeration in the early decades after plantation establishment [38,44], some studies suggest that SOC stock is neutral, i.e., neither increases nor decreases with stand age [1,16,48]. This phenomenon may be ascribed to numerous factors, such as soil properties, tree species, pre-planting disturbance, and site management, all of which may individually or jointly overshadow the effect of stand age on SOC stock [13,36].…”