半干旱黄土丘陵区退化人工林群落结构调整下细根特征分析

Fine root characteristics of degraded artificial forest under community structure adjustment in semiarid loess hilly region

根系尤其细根在植物的生长发育中起着重要作用,以甘肃省定西市巉口镇龙滩流域的白杨及山杏2种典型退化人工林为研究对象,研究了人工林群落结构调整后形成的白杨+5年生油松、白杨+10年生油松及山杏+云杉、山杏+樟子松混交林与单一纯林相比不同深度、不同径级下细根的根长密度、根面积密度、根生物量密度、比根长及比根面积,以期揭示不同人工林恢复模式下的细根分布特征。结果表明:(1)混交恢复模式起到了一定的积极作用,大部分混交林相较于纯林细根的根长密度、根面积密度及根生物量密度在土壤表层均有所提高。混交林细根在浅层的占比得到了提高,且随恢复年限的增加而升高。(2)细根根长密度、根面积密度及根生物量密度与土壤全碳、全氮、含水量及有机碳之间以及比根长及比根面积与土壤全碳、土壤全氮及有机碳之间均存在显著正相关关系。

This study was conducted in Longtan watershed,Chankou Town,Dingxi City,Gansu Province,China in order to reveal the fine roots distribution characteristics of different plantation restoration patterns.Two typical degraded artificial forests in this study area included Populus tomentosa and Armeniaca sibirica,and their adjusted mixed forests included Populus tomentosa with 5-year-old Pinus tabuliformis,Populus tomentosa with 10-year-old Pinus tabuliformis,Armeniaca sibirica with Picea asperata,and Armeniaca sibirica with Pinus sylvestris.The root length density,root area,root biomass density,specific root length and specific root area of fine roots of the mentioned forests were compared in different soil depth and diameter degree.The roots of different soil layers in sampling plots were collected by root-drilling method.In the lab,the roots were scanned by a root scanner and were classified by WinRHIZO software.Excel 2003 and SPSS 24 software were used for data analysis.One-way ANOVA and LSD method were used to compare the significant differences of various indicators between vegetation restoration patterns and different soil layers.In a 0-to 10-cm soil layer,results showed that the mixed restoration model played a positive role in the increase of the growth of plant roots,root area density,and root biomass density of most mixed forests in the surface soil layer compared with that of the pure forest.Specifically,the root length density of Armeniaca sibirica with Picea asperata and Armeniaca sibirica with Pinus sylvestris were 2.85 cm·cm^-3 and 2.08 cm·cm^-3,respectively,which were higher than that of Armeniaca sibirica(1.65 cm·cm^-3).Similarly,higher root area densities were observed with the two mixed forests(27.48 cm2·cm^-3 and 20.00 cm2·cm^-3,respectively)compared to that of Armeniaca sibirica(16.21 cm2·cm^-3).Finally,the root biomass density of the two mixed forests were 1.25 mg·cm^-3 and 1.36 mg·cm^-3,respectively,which were higher than that of Armeniaca sibirica(1.03 mg·cm^-3).The root length density,root area density,and root biomass density of Populus tomentosa with 5-year-old Pinus tabuliformis and Populus tomentosa with 10-year-old Pinus tabuliformis were 1.52 cm·cm^-3 and 2.11 cm·cm^-3,18.16 cm2·cm^-3 and 26.46 cm2·cm^-3,and 1.23 mg·cm^-3 and 1.82 mg·cm^-3,respectively.The root length density,root area density,and root biomass density of Populus tomentosa were 1.68 cm2·cm^-3,17.66 cm2·cm^-3,and 1.41 mg·cm^-3,respectively.The mixed forest of Populus tomentosa with 10-year-old Pinus tabuliformis had the highest root length density,root area density,and root biomass density in the surface soil layer.In a 1-m deep soil layer,the average root biomass density of Populus tomentosa,Populus tomentosa with 5-year-old Pinus tabuliformis,and Populus tomentosa with 10-year-old Pinus tabuliformis were 0.58 mg·cm^-3,0.66 mg·cm^-3,and 0.82 mg·cm^-3,respectively.The root biomass density of Populus tomentosa and Pinus tabuliformis mixed forests were higher than that of the pure forest and were found to increase with increased restoration years.The average root length density and root area density of Armeniaca sibirica with Picea asperata and Armeniaca sibirica with Pinus sylvestris mixed forests were observed to be higher than that of Armeniaca sibirica in a 1-m soil layer.From the vertical soil profile,the root length density,root area density,and root biomass density of fine roots in all restoration patterns showed obvious surface aggregation phenomenon.The mixed restoration patterns increased the proportion of fine roots in the surface layer and increased with increased restoration years.The correlation analysis between the root indexes and the soil physiochemical indexes showed that the fine root length density,root area density,and root biomass density were significantly positively correlated with soil total carbon,total nitrogen,water content,and organic carbon.Specific root length and specific root area also had a positive relationship with soil total carbon,soil total nitrogen,and organic carbon.