Effects Of Warming And Precipitation Exclusion On Biomass Allocation And Carbon Pool Characteristics Of Cunninghamia Lanceolata Saplings In Subtropics

As an important component of forest ecosystems,forest vegetation have attracted more and more attention to global change.Subtropical regions,as the transition zone between temperate and tropical regions,are more sensitive to environmental changes.China’s Subtropical region in China have abundant forest resources and huge carbon sequestration potential.It is of great significance to assess the impact of future climate change on the growth of subtropical forest vegetation and carbon sequestration capacity.In this study,biomass allocation and carbon pool characteristics of Cunninghamia lanceolata saplings were investigated by warming and precipitation exclusion.The experiment was conducted in Chenda Research Station of Fujian Normal University in Fujian province of China,the experiments were established in 20 mini-plots(2 m × 2 m)with the following treatments: control(CT),warming(W),precipitation exclusion(P)warming ×precipitation exclusion(WP).In April 2018,the Cunninghamia lanceolata saplings were harvested after four years.The biomass of branch,stem,leaf,bark and the root biomass of different diameter levels of the saplings were harvested.The carbon content of each organ was measured and the carbon pool of saplings were calculated to reveal the impact of climate change on plant growth strategies.The main conclusions are as follows:(1)The warming treatment did not significantly affect the biomass and carbon pool of the Cunninghamia lanceolata saplings.The biomass,carbon pool of the four organs of leaf,branch,bark,and stems did not change significantly,but the root biomass and carbon content allocated to diameters of 20-50 mm decreased significantly,while the biomass of 2-5 mm and 5-10 mm root biomass increased significantly.(2)Precipitation exclusion promoted the growth of the Cunninghamia lanceolata saplings,and the tree height,breast diameter,the biomass of aboveground and belowground increased significantly,especially the biomass of stem and larger diameter root.The biomass of stem increased by 64.80% significantly,the root bionass of 5-10 mm and 10-20 mm increased by 45% and 40% respectively(P< 0.05).The precipitation exclusion treatment not only promoted the growth of Chinese fir saplings,but also significantly improved the aboveground,belowground,and total carbon pools.(3)The interaction between warming and precipitation exclusion significantly inhibited the growth of Cunninghamia lanceolata saplings,reduced biomass and crbon pool,and the total biomass and carbon pool of the aboveground parts decreased by33.16% and 37.92%,respectively(P <0.05).The interaction between warming and precipitation exclusion decreased soil moisture,and the tree preferentially allocated biomass and carbon to belowground to ensure the growth of the root system.(4)Warming、precipitation exclusion and the interaction of warming and precipitation exclusion decreased soil moisture content of 19%,12.50%,and 31.80%,respectively(P<0.05).The decrease of soil moisture inhibited the accumulation of root biomass in the surface layer.In order to absorb more water and nutrients,the tree allocated more biomass to the 40-60 cm soil depth.