Lianas potentially play an important role in the climate change response and drought vulnerability of tropical forests. However, our understanding of the role of lianas in forest functioning is limited.

This proposal aims to understand the competition for water by liana and tree roots. The underlying research question is: ‘do lianas and trees compete for the same below ground water resource?’To

date, there is no single scientific study showing that lianas do compete for the same water resources as trees. However, results of a pilot field experiment we conducted in French Guiana in 2015

indicate that lianas and trees have very different water resources during the dry season, with lianas tapping soil water with an enriched isotopic signature, corresponding to surface soil layers, while

trees tap from deeper soil layers. This research grant proposal aims to comprehend lianas below ground water competition strategy by (a) verifying the preliminary results found during dry season,

(b) studying potential strategy shifts under different conditions (wet season and extreme drought) and (c) unraveling the hydrological niche separation. We will use observations of natural abundance

of 2 stable water isotopes H and O in soil and plant material to study the water resource use of trees versus lianas. This project will result in an unique dataset and new insights that will be very

relevant for future modelling work.