Impact of rainfall variability on the ecophysiology of Hyptis suaveolens: a study in the constructed tropical grassland.

Hyptis suaveolens is considered one of the most potent invaders in the eastern part of Uttar Pradesh, India. Climate change especially precipitation variability along with invasion has enormous consequences. To understand how an invasive plant (H. suaveolens) performs and interacts with precipitation variability, particularly in tropical monsoon climate, is vital. To assess the above, three rainout shelters with simulated rainfall of 1600 mm (60% more rainfall than ambient), 1100 mm (average rainfall) and 800 mm (20% less rainfall than ambient) along with one unsheltered plot (open C) were established. Three invaded grassland (IG) and three uninvaded grasslands (NIG) patches of 1 × 1 m size were established randomly in each sheltered and unsheltered plot. Among the studied physiological properties and growth measurements, photosynthetic rate, height, diameter and biomass varied significantly with precipitation, in general, the maximum value of these in plots receiving maximum precipitation. Also, the aboveground biomass of H. suaveolens was found to be more sensitive towards precipitation treatment than belowground biomass. H. suaveolens biomass was linearly related to soil moisture (R = 0.73), and a linear combination of SM and soil pH increased the R value by 19%. The results indicate that H. suaveolens mediates certain soil properties especially related to N-mineralisation, to maintain a constant supply of nutrient, for faster growth under the favourable condition of enhanced precipitation. These findings suggest that the population of H. suaveolens has not evolved drought tolerance, so it is likely that H. suaveolens will not spread in the part of the world which is drier either naturally or due to climate change.