Effects Of Night Warming And Changing Precipitation On Root Production And Dead In Three Temperate Steppes

Since the Industry Revolution,greenhouse gas concentration has been increasing due to intensified anthropogenic activities,which leads to increased global average temperatures,and greater increases in night than day temperature.The change of atmospheric water circulation caused by climate warming can affect rainfall pattern.Climate warming and changing precipitation can affect ecosystem structure and function,with consequent effect on the carbon cycle in terrestrial biosphere.Plant root is an important component in linking above-and below-ground carbon processes,and the response to climate change is very sensitive and complex.Previous studies mostly focused on single grassland types or experimental sites,with no consistent conclusion.There was no comparative research demonstrating on root responses to night warming and changing precipitation regimes of different grassland ecosystems.A experiment with night warming and changing precipitation(increased 30% rainfall amount and decreased 30% rainfall amount)with three temperate steppes(desert steppe,typical steppe,and meadow steppe)along the natural precipitation gradient in the arid and semiarid region of northern China transplanted to the same study site was conducted.From Jun.to Sep.in 2016 and during the growing season(from May.to Oct.)in 2017,for the whole temperate steppe,night warming did not affect root length production and number production,but stimulated root length dead by 25.8%(relative change),and number dead by 20.2%.Decreased precipitation suppressed root length production,number production,length dead,and number dead by 180.5%,26.7%,19.3%,and 27.6%,respectively.Increased precipitation had no influence on root length production,number production,length dead,and number dead.It was found that the root production and dead of different temperate steppe types had different response to night warming and changing precipitation.Night warming increased root length production,number production,length dead,and number dead by 37.9%,45.6%,25.8%,and 62.3%,respectively in desert steppe.Night warming had no influence on root length production,number production,length dead,and number dead in typical steppe.Night warming enhanced root length production,length dead,and number dead by 25.7%,33.2%,and 16.5%,respectively,but did not affect root number production in meadow steppe.Decreased precipitation reduced root length production,number production,length dead,and number dead by 48.5%,45.6%,62.5%,and 27.6%,respectively in desert steppe.Decreased precipitation had no influence on root length production,number production,length dead,and number dead in typical steppe.Decreased precipitation suppressed root length production,number production,length dead,and number dead by 38.9%,36.2%,44.1%,and 40.0%,respectively in meadow steppe.Increased precipitation elevated root number dead by 28.3%,but had no influence on root number production,length production,and length dead in desert steppe.Increased precipitation did not affect root length production,number production,length dead,and number dead in typical steppe.Increased precipitation enhanced root length production and length dead by 43.7%,and 32.3%,respectively,but had no influence on root length production and length dead.Changing precipitation-induced changes in soil respiration showed no relationship with changing precipitation-induced changes in root production and root dead.Night warming-induced changes in soil respiration showed no relationship with night warming-induced changes in root length production and length dead.However,there are positive dependences of night warming-induced changes in soil respiration on night warming-induced changes in root number production and number dead.Soil respiration is an important way of carbon emission in terrestrial ecosystems,which has a profound impact on global carbon cycle.The findings indicate that night warming-induced changes in root number can affect soil respiration,and may subsequently affect ecosystem carbon cycling.The study will improve the forecast for the response of the carbon cycling in temperate steppe ecosystems to global change in the future.