Effects Of Soil Warming And Precipitation Exclusion On Fine Root Production And Ecophysiological Properties Of Cunninghamia Lanceolata Seedlings

Changes in global warming are expected to have profound effects on precipitation.The aim of study is explore the below-ground responses and adaptability of the most important timber species in southern China,Chinese fir(Cunninghamia lanceolata),to global warming and precipitation changes.A factorial experiment of soil warming and precipitation exclusion was carried out in the Chenda observatory of Sanming Research Station of Forest Ecosystem and Global Change,Fujian Province,including the control treatment(CT),the soil warming treatment(W,+50℃),the precipitation exclusion treatment(P,-50%)and the soil warming+precipitation exclusion treatment(WP).We measured changes in fine root production in response to soil warming,precipitation exclusion and their interaction using the minirhizotron method after two year;and we measured changes in fine root production ecophysiological properties in response to soil warming,precipitation exclusion and their interaction using the ingrowth core donut method after two years.The results showed:(1)that the interaction of soil warming and precipitation exclusion had significant effect on the total fine root production,and total fine root production had significant difference under different years;the effects of fine root production of the interaction of soil warming and precipitation exclusion mainly accured in spring 2014 and summer 2015,0-1 mm diameter class and 20-40 cm soil layer.It is concluded that precipitation exclusion counteracted the acceleration of soil warming to fine root production,and the interaction of soil warming and precipitation influenced fine root production through changing the fine root seasonal distribution,diameter class and soil layer allocation.The results also showed:(2)that the interaction of soil warming and precipitation exclusion significantly reduced fine root production at the soil depth of 0-20 cm.Compared to the CT treatment,the WP treatment significantly increased fine root specific root length(SRL),specific root surface area(SRA)in 1-2 mm diameter class in January 2016,whereas significantly decreased fine root SRL in 1-2 mm diameter class in July 2016.The WP treatment of fine root nitrogen concentration was significant higher than the CT treatment,whereas the WP treatment of fine root carbon-nitrogen ratio was lower than the CT treatment in 0-1 and 1-2 mm diameter class in January and July 2016,the WP treatment of fine root phosphorus concentration was lower than the CT treatment in 0-1 mm diameter class in July 2016.The fine root respiration did not acclimate to the interaction of soil warming and precipitation exclusion in January and July 2016.The souble sugar-starch ratio had no significant changes between the WP treatment and the CT treatment in 0-1 mm diameter class in January and July 2016,but the WP treatment of fine root nonstructural carbonhydrate(NSC)was lower than the CT treatment in 0-1 mm diameter class in January 2016.It is concluded that the interaction of soil warming and precipitation exclusion significantly increased SRL、SRA to obtain soil moisture and nutrients,meanwhile increased the fine root nitrogen concentration,which causing the enhancement of fine root SRR.Thus the fine root consumped carbon concentration and NSC for growthing.