2个径级油松细根对土壤水分条件和草本根系竞争的季节性响应OA

[Objective]To understand the influences of soil water conditions in different seasons and herb underground competition on fine roots(≤2 mm)of Pinus tabulaeformis on Loess Plateau and their responses to reveal their potential acclimation mechanisms.[Method]We selected 12 near mature artificial pure Pinus tabulaeformis stands on the eastern edge of the Loess Plateau and measured the morphology,biomass accumulation and growth of Pinus tabulaeformis fine roots of 0-1 mm and 1-2 mm diameter classes in 0-15 cm,15-30 cm and 30-45 cm soil layers in spring and autumn with contrasting precipitation patterns.The effects of season,soil layer,root classes and their interactions on Pinus tabulaeformis fine roots were analyzed using ANOVA analysis.The influences of soil water content and understory herb root biomass on Pinus tabulaeformis fine roots were examined using Pearson correlation analysis by diameter class.[Result]The results showed that the average soil moisture content(SWC)in spring is significantly lower than in autumn in the 0-45 cm soil profile,but comparable to that in autumn in the 0-15 cm soil layer.The roots of understory herbs are mainly distributed in the 0-15 cm soil layer with no seasonal variation.In spring,the biomass,length,and surface area of 0-1 mm and 1-2 mm Pinus tabulaeformis fine root classes are the same as those in autumn in the 0-45 cm soil profile,but significantly and negatively correlated with SWC in the 30-45 cm soil layer.The average root diameter of Pinus tabulaeformis fine roots is the same between spring and autumn,and the average specific root length(SRL)and specific root area(SRA)are significantly larger in spring than in autumn.However,in comparison to the 1-2 mm class,the root diameter of the 0-1 mm class in spring is significantly smaller than in autumn,and its SRL and SRA are significantly higher and negatively correlated with SWC in the 0-45 cm soil profile and also 30-45 cm soil layer.In spring,the length and surface area of 1-2 mm Pinus tabulaeformis fine roots in the 0-15 cm soil layer were significantly and negatively correlated with the herb root biomass concentrated in the same soil layer.[Conclusion]In the near mature Pinus tabulaeformis stands at the eastern edge of Loess Plateau,although soil water content may limit the fine root growth of Pinus tabulaeformis trees,the compensation of spring precipitation to shallow soil may maintain their biomass accumulation and growth in the 0-15 cm soil layer,resulting in insignificant seasonal differences across the entire soil profile.The morphological responses and acclimation of 0-1 mm Pinus tabulaeformis fine roots to soil water content in spring are higher than those of 1-2 mm diameter fine roots,implying their faster morphological responses to possible spring soil drought.The growth of 1-2 mm Pinus tabulaeformis fine roots in the 0-15 cm soil layer is inhibited by underground competition from understory herbs in spring.