3种多年生禾本科牧草不同径级根系特征比较

A comparative study of the characteristics of roots of three perennial gramineous forages with different diameter classes

根系是植物吸收营养元素和水分的重要器官,可以维持和提高土壤质量,对退化高寒草甸的恢复演替起到重要作用.以3种多年生禾本科牧草(紫羊茅(Festuca rubra)、垂穗披碱草(Elymus nutans)和老芒麦(Elymus sibiricus))单播草地作为研究对象,采用微根管技术对不同径级根系特征(现存量、生产量、死亡量、周转和寿命)的变化以及群落特征和土壤理化性质进行比较分析.结果表明:(1)3种牧草的总根系现存量和生产量均随着土层的增加而减少,总根系死亡量、周转及寿命在土层间无显著差异(P>0.05).(2)紫羊茅表层土壤1级根系周转分别显著大于垂穗披碱草和老芒麦42.56%和45.29%;2级根系现存量、生产量和死亡量分别显著大于垂穗披碱草144.51、17.85和2.72 g/m^(2)及老芒麦155.31、17.57和2.06 g/m^(2),而1级根系现存量及生产量则分别显著小于垂穗披碱草72.68和5.12 g/m^(2).(3)紫羊茅群落盖度分别显著大于垂穗披碱草和老芒麦群落盖度36.43%和142.77%,且群落生物量分别显著大于其他两种牧草67.70和116.52 g/m^(2).(4)老芒麦草地表层土壤碳磷比分别显著高于紫羊茅和垂穗披碱草49.27%和35.84%,而老芒麦草地深层土壤碳磷比则分别显著低于其他两种牧草37.83%和32.42%.(5)结构方程模型显示,牧草种类和土层深度通过影响土壤全氮含量间接影响不同径级根系的生产量和周转,进而影响不同径级根系现存量.综上所述,3种牧草的根系分配和形态特征之间具有明显的差异,且对土壤养分的利用效率也不相同;根据牧草对土壤养分资源的利用及根系分配特征,建植紫羊茅和老芒麦混播人工草地可能更有利于退化高寒草甸植物群落和土壤的恢复.

Roots are important organs in plants for nutrient and water absorption that maintain and improve soil quality and play an important role in the restoration and succession of degraded alpine meadows.Diameter is an important functional trait of root systems,and the size of a root system reflects different physiological functions.This study aimed to explore the characteristics of roots with different diameter classes of three perennial gramineous forages and to explore a more suitable method for establishing artificial grasslands for the restoration of degraded meadows.We investigated and analyzed aboveground community characteristics and soil physicochemical properties and used the minirhizotron method to compare changes in root characteristics(standing crop,production,mortality,turnover,and longevity)of different diameters in three perennial gramineous forages:Festuca rubra,Elymus nutans and Elymus sibiricus.The results showed that:(1)The root standing crop and production of the three forage species decreased with increasing soil depth,whereas the total root mortality,turnover,and longevity did not differ significantly between the topsoil and subsoil(P>0.05).(2)In the topsoil,the turnover of the first-order roots of F.rubra was significantly higher than that of E.nutans and E.sibiricus(42.56%and 45.29%,respectively).The standing crop,production,and mortality of the second-order roots of F.rubra were significantly higher than those of E.nutans and E.sibiricus by 144.51 and 155.31 g/m^(2)(standing crop),17.85 and 17.57 g/m^(2)(production),and 2.72 and 2.06 g/m^(2)(mortality),respectively.The standing crop and production of the first-order roots of F.rubra were significantly lower than those of E.nutans by 72.68 and 5.12 g/m^(2),respectively.(3)The coverage and aboveground biomass of F.rubra were significantly higher than that of E.nutans and E.sibiricus by 36.43%and 142.77%(coverage)and 67.70 and 116.52 g/m^(2)(biomass),respectively.(4)The ratios of carbon and phosphorus in the topsoil of E.sibiricus were significantly higher than those in the topsoil of F.rubra and E.nutans by 49.27%and 35.84%,respectively.In the deep soil,the ratios of carbon and phosphorus in E.sibiricus were significantly lower than those in F.rubra and E.nutans by 37.83%and 32.42%,respectively.(5)Structural equation modeling revealed that forage species and soil depth indirectly affected root production and turnover by influencing soil total nitrogen content,which then affected the root standing crop.In conclusion,the distribution and morphological characteristics of the roots differed significantly among the three forages in terms of soil nutrient utilization efficiency.Based on the characteristics of root distribution and soil nutrients of the three forages,development of mixed grasslands with F.rubra and E.sibiricus might be more beneficial for the restoration of degraded alpine meadows.