Cacao Cultivation under Diverse Shade Tree Cover Allows High Carbon Storage and Sequestration without Yield Losses

PLoS One. 2016 Feb 29;11(2):e0149949. doi: 10.1371/journal.pone.0149949. eCollection 2016.

Abstract

One of the main drivers of tropical forest loss is their conversion to oil palm, soy or cacao plantations with low biodiversity and greatly reduced carbon storage. Southeast Asian cacao plantations are often established under shade tree cover, but are later converted to non-shaded monocultures to avoid resource competition. We compared three co-occurring cacao cultivation systems (3 replicate stands each) with different shade intensity (non-shaded monoculture, cacao with the legume Gliricidia sepium shade trees, and cacao with several shade tree species) in Sulawesi (Indonesia) with respect to above- and belowground biomass and productivity, and cacao bean yield. Total biomass C stocks (above- and belowground) increased fivefold from the monoculture to the multi-shade tree system (from 11 to 57 Mg ha-1), total net primary production rose twofold (from 9 to 18 Mg C ha-1 yr-1). This increase was associated with a 6fold increase in aboveground biomass, but only a 3.5fold increase in root biomass, indicating a clear shift in C allocation to aboveground tree organs with increasing shade for both cacao and shade trees. Despite a canopy cover increase from 50 to 93%, cacao bean yield remained invariant across the systems (variation: 1.1-1.2 Mg C ha-1 yr-1). The monocultures had a twice as rapid leaf turnover suggesting that shading reduces the exposure of cacao to atmospheric drought, probably resulting in greater leaf longevity. Thus, contrary to general belief, cacao bean yield does not necessarily decrease under shading which seems to reduce physical stress. If planned properly, cacao plantations under a shade tree cover allow combining high yield with benefits for carbon sequestration and storage, production system stability under stress, and higher levels of animal and plant diversity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agriculture*
  • Biodiversity
  • Biomass
  • Cacao / growth & development*
  • Cacao / metabolism
  • Carbon / metabolism*
  • Carbon Sequestration*
  • Forests
  • Geography
  • Indonesia
  • Linear Models
  • Plant Roots / physiology
  • Plant Shoots / physiology
  • Principal Component Analysis
  • Soil / chemistry
  • Trees / physiology*

Substances

  • Soil
  • Carbon

Grant support

This study was financed by the German Research Foundation (DFG) in the framework of the interdisciplinary German-Indonesian research project ELUC (‘Environmental and land-use change in Sulawesi, Indonesia’) and the collaborative research center CRC990 'Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems (Sumatra, Indonesia)’, subproject B04. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.