Growth performance of six multipurpose tree species based on the carbon assimilation capacity: a functional approach

This study is an attempt to evaluate six tree species with potential for growth and water use efficiency under 50% moisture stress, based on the carbon assimilation capacity in order to identify species to be grown in low moisture conditions. Plants were maintained at field capacity (control) and at 50% less than the field capacity (stress) in lysimeters for 90 days by weighing them and replenishing with the water lost. Eucalyptus comaldulensis and Melia dubia recorded 259 and 204 and 243 and 151 g plant⁻¹ of biomass under control and moisture stress conditions respectively while Simaruba glauca and Callophylum inophyllum recorded 61–53 and 37–23 g plant⁻¹. Photosynthetic rates of these species were in the range of 25.43–22.78 and 9.10–8.03 μmol m⁻²s⁻¹ under control and stress conditions respectively, which corroborated with biomass production. Both diffusive and carboxylation processes of photosynthesis were higher in species with higher biomass. Photosynthetic rates assessed using leaf model and cumulative models go with each other. Species with higher photosynthetic rates tended to sustain under stress by reducing photosynthetic surface area and maintain the growth rates suggesting that growth performance under moisture stress depends on carbon assimilation capabilities. This was also evident in species with low photosynthetic rates which recorded lower growth rates. Species with lower carbon assimilation showed higher water use efficiency, while it was the opposite in species with higher carbon assimilation. Isohydric behavior of stomata help plants to maintain longer stomatal conductance and hence the photosynthetic rates, but lower water use efficiency. Such a strategy helps plants in sustaining growth under intermittent moisture stress. Thus slow growing species with higher water use efficiency and lower moisture consumption are useful in establishing tree cover in marginal lands with low moisture.