Prediction model for sap flow in cacao trees under different radiation intensities in the western Colombian Amazon

In this study, we measured diurnal patterns of sap flow (Vs) in cacao trees growing in three types of agroforestry systems (AFs) that differ in the incident solar radiation they receive. We modeled the relationship of Vs with several microclimatic characteristics of the AFs using mixed linear models. We characterized microclimatic variables that may have an effect on diurnal patterns of sap flow: air relative humidity, air temperature, photosynthetically active radiation and vapor pressure deficit. Overall, our model predicted the differences between cacao Vs in the three different AFs, with cacao plants with dense Musaceae plantation and high mean diurnal incident radiation (HPAR) displaying the highest differences compared to the other agroforestry arrangements. The model was also able to predict situations such as nocturnal transpiration in HPAR and inverse nocturnal sap flows indicative of hydraulic redistribution in the other AFs receiving less incident radiation. Overall, the model we present here can be a useful and cost-effective tool for predicting transpiration and water use in cacao trees, as well as for managing cacao agroforestry systems in the Amazon rainforest.

This project was carried out with the financial collaboration of COLCIENCIAS using BID funds under the framework “Characterization and classification of traditional Theobroma cacao plantations as a strategy for the design and implementation of agroforestry arrangements in the Bajo Caguán (Cartagena del Chaira)”, carried out by Amazonia University through a special contract of cooperation 590 from 2012. To the Amazonia University funds for Doctoral Training under the seal “Pro-development of Amazonia University” Law No. 1301 of 2009. The authors thank the Mesoamerican Platform for Scientific Cooperation in Agroforestry Systems with Perennial Crops for their academic and financial support for the development of this manuscript. CA had a “Ramón y Cajal” contract from the Spanish Government and CSIC (RYC-2012-12277).

Peer reviewed