A simple framework to analyze water constraints on seasonal transpiration in rubber tree (Hevea brasiliensis) plantations.

Jessada Sopharat,Charlchai Tanavud,Philippe Thaler,Frederic Gay,Claude Hammecker,Supat Isarangkool Na Ayutthaya,Sayan Sdoodee,Frederic C. Do

doi:10.3389/fpls.2014.00753

Abstract

Climate change and fast extension in climatically suboptimal areas threaten the sustainability of rubber tree cultivation. A simple framework based on reduction factors of potential transpiration was tested to evaluate the water constraints on seasonal transpiration in tropical sub-humid climates, according pedoclimatic conditions. We selected a representative, mature stand in a drought-prone area. Tree transpiration, evaporative demand and soil water availability were measured every day over 15 months. The results showed that basic relationships with evaporative demand, leaf area index and soil water availability were globally supported. However, the implementation of a regulation of transpiration at high evaporative demand whatever soil water availability was necessary to avoid large overestimates of transpiration. The details of regulation were confirmed by the analysis of canopy conductance response to vapor pressure deficit. The final objective of providing hierarchy between the main regulation factors of seasonal and annual transpiration was achieved. In the tested environmental conditions, the impact of atmospheric drought appeared larger importance than soil drought contrary to expectations. Our results support the interest in simple models to provide a first diagnosis of water constraints on transpiration with limited data, and to help decision making toward more sustainable rubber plantations.

Highlights

The rubber tree (Hevea brasiliensis) is a major tree crop in Southeast Asia
relative extractable water (REW) values above 1 at the end of October suggested temporary water logging in the topsoil which was confirmed by observations
In conclusion, the adapted framework of BILJOU99 had allowed analyzing the relative contribution of soil water shortage and atmospheric drought to the regulation of transpiration on a seasonal scale

Summary

Introduction

The rubber tree (Hevea brasiliensis) is a major tree crop in Southeast Asia. Globally, it covers 9.82 million hectares mainly exploited by smallholders (UNCTAD, 2013). In the last 30 years, the rubber plantations have largely expanded into climatically sub-optimal areas in north and northeast Thailand. The dynamic of land use is similar to that in other rubber-producing countries, with expansions recorded in northeast India, the highlands and coastal areas of Vietnam, southern China, and the southern plateau of Brazil (Priyadarshan et al, 2005). In such areas, rubber can be constrained by drought, low temperature and high altitude or by periodic heavy rainfall. The availability of simple models with limited data to analyze water constraints on tree transpiration and consequences on growth, production and soil water balance is a key issue (Guardiola-Claramonte et al, 2010; Boithias et al, 2012; Carr, 2012)

Results

Discussion

Conclusion