| Pinus sylvestris L.is the main windbreak and sand-fixing plant in the Mu Us Sandy Land.Its water consumption is usually greater than that of crops and herbaceous plants,which can cause a decrease in soil water storage and potential risks to the ecosystem.Root distribution characteristics determine plant absorption and utilization of soil water content.Understanding the influence of Pinus sylvestris roots on soil water under limited soil water resources is crucial for achieving sustainable development of artificial forests and vegetation restoration in the Mu Us Sandy Land.This study aimed to quantify the distribution characteristics of Pinus sylvestris roots and soil water content in different age groups 20 years(PL20),40 years(PL40),60 years(PL60)of artificial forests in the Mu Us Sandy Land,and to compare these with grasslands(CK).The study used field sampling and indoor determination to clarify the impact of root distribution and morphology on soil water content,and identified the main influencing factors of soil water content.The main findings are as follows:The order of magnitude of mean soil water content in different sites during the reproductive period was CK>PL60>PL40>PL20(P<0.05),and all monthly mean soil water contents in the vertical direction were of moderate variability.The soil water content of the shallow layer(0-100 cm)in the soil profile of the stand was significantly higher than that of the deep layer(100-500 cm).the soil water content of the shallow layer in PL20,PL40 and PL60 increased with the increase of month,while the soil water content of the deep layer basically tended to be stable.With the increase of forest age,the soil water content tended to decrease and then increase.The minimum soil water content of different soil layers was between PL20 and PL40,and CK maintained the maximum soil water content among different soil layers.The cumulative soil water depletion in different stands was 328.18 mm(PL20),333.67 mm(PL40)and 175.24 mm(PL60).The vertical distribution and morphology of the root system differed significantly among the three age groups(P<0.05).Total root biomass gradually decreased with an increase in age.The root biomass of different ages showed a decreasing trend on the soil profile,and the total root biomass of each soil layer was as follows:PL20(2190.05 g/m~2)>PL40(2023.54g/m~2)>PL60(1625.07 g/m~2).With an increase in age,the distribution depth of roots becomes shallower.The mean order of root length density for each age layer was PL40(255.04 cm/m~3)>PL60(199.85 cm/m~3)>PL20(151.42 cm/m~3),and their vertical variation coefficients were0.89,0.78,and 1.03,respectively.Moreover,the root surface area ratio was highly variable in PL60.The root biomass and root length density of PL20 had a significant positive correlation with soil water content(P<0.05);the root biomass,root length density,root surface area ratio,and average diameter of PL40 were extremely significantly positively correlated with soil water content(P<0.01);and the mean root diameter of PL60 was significantly positively correlated with soil water content(P<0.05).The utilization of soil water by roots becomes shallower with increasing age.Path analysis showed that all root morphological parameters jointly affected the changes in soil water content.Root length density of PL20,root biomass of PL40,and mean root diameter of PL60 were identified as the main influencing factors of soil water among the different ages of Pinus sylvestris. |
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