Differential response of graminoid and forb species to precipitation variability in a constructed dry tropical grassland.

Precipitation and temperature are the two major drivers of species distribution on the earth. Change in precipitation has severe effects on the species composition of all ecosystems including grassland. In the present study, we have tried to assess the effect of precipitation on two major functional groups of tropical grassland i.e. graminoid (grasses and sedges) and forbs (herbaceous flowering plants). The study was performed in three rainout shelters with three different rain doses (16T, 11T, and 8T) and one unsheltered plot (open C) with ambient rain. Each sheltered and unsheltered plot has three 1 × 1 m randomly assigned subplots of uninvaded indigenous grassland plots (NIG). The study revealed that the aboveground net primary production (ANPP) of graminoids + forbs of the tropical grassland increase with the increase in precipitation. A significant positive correlation of ANPP was found with total inorganic – N (TIN) and soil moisture (SM) and a significant negative with microbial biomass nitrogen (MBN). Regression analysis reveals that after soil moisture, total inorganic – N and N – mineralization are the major determinants for the ANPP. However, when graminoid and forb species are studied separately, graminoids showed a positive response to increased precipitation while forbs did not show such a response. Indicating that the major contributor to the ANPP response toward precipitation increase is graminoid species in a dry tropical grassland. The study indicates the sensitivity of Indian grassland to the change in rainfall quantity, as studied forbs species decrease in both low and high precipitation. Showing that in tropics, forbs species may extinct as of their narrow range of tolerance due to precipiation change, in turn affecting the biodiversity of the area. This is the new possibility of research for researchers around the world. Moreover, to draw any conclusion a detailed study considering the nature of resource acquisition, root length, root architect, and competitive behavior among graminoids and forbs must be done separately, in relation to the precipitation. [ABSTRACT FROM AUTHOR]