西南亚高山冬瓜杨和峨眉冷杉吸收根特征

Characteristics of absorptive roots of subalpine Populus purdomii and Abies fabri in Southwest China

植物的吸收根是植物从土壤中获取资源的重要器官,其快速周转在生态系统碳循环和养分循环中充当着重要作用,而且其形态特征也反映了植物根系对地下资源利用策略的异同.以海螺沟冰川末端原生演替后期非顶极落叶阔叶林优势物种冬瓜杨(Populus purdomii)和顶极的暗针叶林群落优势物种峨眉冷杉(Abies fabri)作为研究对象,采用土钻法获取两种优势物种的吸收根,分别测定两个优势树种的吸收根形态特征及对应的林下土壤养分含量、温度和湿度.结果显示:(1)两个森林群落林下的土壤温湿度差异不显著,但峨眉冷杉群落土壤总氮、有效氮、有效磷、铵态氮及硝态氮显著高于冬瓜杨群落;(2)峨眉冷杉的总根长、根长密度、比根长和比表面积显著低于冬瓜杨,平均根直径、总根体积和生物量密度显著高于冬瓜杨;(3)冗余分析表明,冬瓜杨和峨眉冷杉的部分吸收根形态特征和土壤养分存在着正相关性,其中冬瓜杨林下土壤有效氮、总磷分别和冬瓜杨根长密度、根比表面积呈显著正相关,峨眉冷杉林下土壤有效氮和峨眉冷杉吸收根平均直径呈显著正相关.上述研究结果说明土壤中氮和有效磷养分显著不同可能是造成冬瓜杨和峨眉冷杉吸收根形态特征差异的重要因素.

The absorptive root is an important part of plants as it extracts nutrients from the soil.The rapid turnover of absorptive roots functions in the carbon and nutrient cycles as a reflection of the root morphological characteristics.Such characteristics of plant roots differ depending on the utilization of underground resources.In this study,Populus purdomii(dominant species of broad-leaved forest as a representative non-climax community) and Abies fabri(dominant species of coniferous forest as a representative climax community) in the retreat terrain of the Hailuogou Glacier were selected as the target species for root samples.All roots were sampled in the field using a soil auger.Morphological characteristics of absorptive roots from both species,soil temperature,soil moisture,and soil nutrient content were all measured under both succession stages.There were no significant differences in soil temperature or moisture between the two types of forest soil;however,soil total nitrogen,available nitrogen,available phosphorus,ammonium nitrogen,and nitrate nitrogen were significantly higher in the A.fabri community than in the P.purdomii community.Total root length,root length density,specific root length,and specific root surface area were all significantly lower in A.fabri than in P.purdomii,but average root diameter,total root volume,and biomass density were significantly higher in A.fabri than in P.purdomii.Positive correlations between some morphological characteristics in both species and soil nutrients were detected by redundancy analysis.In particular,available nitrogen and total phosphorus in the soil of the P.purdomii community positively correlated with root length density and root specific surface area,respectively.Available nitrogen in the soil positively correlated with average root diameter in the A.fabri forest.The results suggested that different root morphological characteristics between different types of forest was mainly due to differences in the available nitrogen and phosphorus in the soil.