大气增温对杉木幼树根系生物量的影响

Effect of air warming on root biomass of Cunninghamia lanceolata saplings

为揭示亚热带杉木人工林地下生物量对全球变暖的响应,本研究以杉木幼树为研究对象,在福建三明森林生态系统国家野外科学观测研究站利用开顶式(OTC)大气增温模拟气候变暖,研究增温对杉木幼树根系生物量的空间分布和不同径级分配的影响。结果表明:增温处理后总根系生物量、总细根生物量及总粗根生物量较对照均无显著差异;与对照相比,增温处理显著降低20~50 cm土层的细根生物量占比与0~10 cm土层的粗根生物量占比,但显著提高20~50 cm土层的粗根生物量占比;其余土层细根生物量和粗根生物量较对照均无显著差异;与对照相比,增温处理后0~2、2~5、5~10、10~20和>20 mm径级根系生物量均无显著变化。因此,增温处理下杉木幼树通过降低表层粗根生物量的占比,提高深层粗根生物量的占比以固定和支撑杉木生长,同时通过降低深层细根生物量的占比来维持表层细根生物量以保证水分和养分的吸收;大气增温影响根系生物量的垂直分布和不同径级的分配,在一定程度上影响地下碳分配,可能导致碳循环过程发生改变。

To understand the responses of belowground biomass of subtropical Chinese fir plantation to global warming,the allocation of root biomass in different soil layers and diameter classes were examined in an experiment with open-top chamber(OTC)to simulate climate warming.Air warming did not affect total root biomass,fine root biomass,and coarse root biomass.Air warming significantly decreased the proportion of fine root in the 20-50 cm soil layer and that of coarse root in the 0-10 cm soil layer,but significantly increased that of coarse root in the 20-50 cm soil layer.Neither fine root biomass nor coarse root biomass in other soil layers was significantly influenced by air warming.Air warming did not affect fine root and coarse root biomass in all diameter classes.Overall,after air warming,Chinese fir saplings could increase the proportion of coarse root biomass in deep soil to support growth,and maintain fine root biomass in topsoil by reducing the proportion of deep fine root biomass to ensure the uptake of nutrients and water.Air warming affects the allocation of root biomass in different soil layers and diameter classes,as well as belowground carbon allocation,with consequences on carbon cycling.