Cocoa agroforestry is less resilient to sub-optimal and extreme climate than cocoa in full sun

Cocoa agroforestryis perceived as potential adaptation strategy to sub-optimal or adverse environmental conditions such as drought. We tested this strategy over wet, dry and extremely dry periods comparing cocoa in full sun with agroforestrysystems: shadedby (i) a leguminoustree species, Albizia ferrugineaand (ii) Antiaristoxicaria, the most common shade treespecies in the region. We monitored micro-climate, sap flux density, throughfalland soil water content from November 2014 to March 2016 at the forest-savannah transition zone of Ghana with climate and drought events during the study period serving as proxy for projected future climatic conditions in marginal cocoa cultivation areas of West Africa. Combined transpiration of cocoa and shade treeswas significantly higher than cocoa in full sun during wet and dry periods. During wet period, transpiration rate of cocoa plants shadedby A. ferruginea was significantly lower than cocoa under A. toxicaria and full sun. During the extreme drought of 2015/16, all cocoa plants under A. ferruginea died. Cocoa plants under A. toxicaria suffered 77% mortality and massive stress with significantly reduced sap flux density of 115 gcm−2d−1 whereas cocoa in full sun maintained higher sap flux density of 170 gcm−2d−1. Moreover, cocoa sap flux recovery after the extreme drought was significantly higher in full sun (163 gcm−2d−1) than under A. toxicaria (37 g cm−2 d−1). Soil water content in full sun was higher than in shadedsystems suggesting that cocoa mortality in the shadedsystems was linked to strong competition for soil water. The present results have major implications for cocoa cultivation under climate change. Promoting shadecocoa agroforestryas drought resilient system especially under climate change needs to be carefully reconsidered as shade treespecies such as the recommended leguminousA. ferruginea constitute major risk to cocoa functioning under extended severe drought. This article is protected by copyright. All rights reserved.