退化沙质草地恢复过程中植被生物量变化及其与土壤碳的关系

Changes in vegetation biomass and its relationship with soil carbon during restoration processes in degraded sandy grasslands

植物生物量分配特征及其向土壤中的物质输入是退化沙质草地生态系统恢复,尤其是土壤碳含量增加的关键环节。本研究以科尔沁沙地不同恢复阶段的流动沙丘、半固定沙丘、固定沙丘和封育草地为研究对象,调查分析草本植被生物量分配特征、根系性状和土壤理化性质特征,厘清生物量分配特征和根系性状与土壤碳的相互关系。结果发现:随着沙化草地逐步恢复,植被地上生物量、根系生物量、地表凋落物以及地下残体均呈显著的增加趋势(P<0.01),相对于沙化严重的流动沙丘,半固定沙丘、固定沙丘和封育草地的植物总干物质(生物量+凋落物)分别增加了11.0%、116.3%和151.2%。与生物量变化趋势相同,土壤碳含量随沙化草地的逐步恢复显著增加(P<0.05),其中0~10cm层的增加速率高于10~20cm层。结构方程模型(SEM)分析显示,0~10cm层土壤碳含量受地表凋落物、地下残体和根表面积3个因素的影响,10~20cm层土壤碳含量仅受地下残体和根表面积两个因素的影响,同时,两层土壤碳含量均与地上生物量无显著的关系。研究结果表明,在退化沙质草地恢复过程中,土壤碳含量主要受凋落物输入以及根系性状的影响,而与地上生物量无直接关系。

The allocation pattern of plant biomass and its input into the soil are key processes for restoring degraded sandy grassland,especially regarding soil carbon accumulation.In this study,mobile dunes,semifixed dunes,fixed dunes,and fenced grasslands in Horqin Sandy Land at different restoration stages were investigated.By analyzing the biomass allocation of herbaceous vegetation,root traits,soil physicochemical properties,and their interrelations,it was found that the aboveground biomass,root biomass,surface litter,and underground necromass all increased significantly(P<0.05)with the extent of desertified grassland restoration.Compared to severely desertified mobile dunes,the total dry matter(biomass+litters)in semifixed dunes,fixed dunes,and fenced grasslands increased by 11.01%,116.29%,and 151.18%,respectively.Similar to the changes in biomass,soil carbon content also increased significantly(P<0.05)with the extent of desertified grassland restoration,with a higher increase rate observed in the 0-10 cm layer than the 10-20 cm layer.Structural equation modeling indicated that the soil carbon content in the 0-10 cm layer was influenced by the surface litter mass,underground necromass,and root surface area.Conversely,soil carbon content in the 10-20 cm layer was affected only by underground necromass and root surface area.Moreover,the soil carbon content in both layers showed an insignificant relationship with aboveground biomass.In conclusion,the soil carbon content in degraded sandy grassland is primarily affected by litter input and root traits but has an insignificant relationship with aboveground biomass.