Effects Of Extrem Drought On Root Belowgroung Net Primary Productivity And Biomass In Innder Mongolia Grassland

Global climate change especially extreme drought is increasingly affecting ecosystem function and processes dramatically.However,the current research about ecosystems mostly focused on aboveground rather than belowground.As an important part of the underground ecosystem,plant roots play an important role in maintaining the energy flow and material circulation of the entire underground ecosystem.Extreme drought will change the plant root system in a direct or indirect way.However,the response of the plant root system to extreme drought on the regional scale and its driving factors are still unclear.Here,we investigated the effects across six grasslands with extreme drought treatment replicated across a precipitation gradient in Inner Mongolia,China.We aimed to assess the effects of extreme drought on the belowground net primary productivity(BNPP)and biomass in 2015-2018 on the regional scale by comparing the root productivity at different grasslands and soil layers,and elucidate the driving factors of plant root response to extreme drought.We found the root biomass and belowground net primary productivity(BNPP)were significantly and positively correlated with precipitation at the reginal scale.Extreme drought decreased the slope of this correlation in 0-10 cm and increased the slope in 10-20 cm.Root biomass and BNPP increased by extreme drought in the four relatively arid sites and decreased in the two relatively mesic sites in 0-10 cm,and the reverse pattern showed in 10-20 cm.These shifts correlated with contrasting changes in relative soil moisture availability with depth across the precipitation gradient and showed that the plants are strongly adapted to enhancing access to water under drought conditions.Our findings suggest that including vertical responses of belowground primary productivity to extreme drought may improve models predictions of plant roots to future climate change.