毛乌素沙地地下水埋深驱动樟子松水分利用趋深适应与效率提升OA

[Objective]This study aims to explore the water use strategies of Pinus sylvestris var.mongolica plantations in the Mu Us Sandy Land,and analyze the dynamic variation patterns and differences in water sources and water use efficiency of P.sylvestris var.mongolica under the interaction of water table depth gradients and hydrologic year types,so as to provide a scientific basis for the stand structure optimization and sustainable management of artificial forests in arid areas.[Method]This study targeted P.sylvestris var.mongolica plantations with initial water table depth(WTD)of 4 m(WTD4),9 m(WTD9)and 13 m(WTD13).Stable isotope techniques(δ2H,δ18O,and δ13C)combined with the MixSIAR model were employed to analyze the response of P.sylvestris var.mongolica water-use strategies to WTD during both dry years and normal precipitation years in the Mu Us Sandy Land.[Result]1)With the increase in WTD and the significant decrease in soil water content(decreasing from 0.029 g·g-1 in WTD4 to 0.022 g·g-1 in WTD13),the proportion of the root mass density of P.sylvestris var.mongolica in the 60-200 cm soil layer to the total root mass density in the 0-200 cm soil profile increased(increasing from 17.3%in WTD4 to 24.0%in WTD13).2)Water sources of P.sylvestris var.mongolica differed under different WTD during the same period,and varied across different hydrologic years within the same WTD.The proportion of shallow soil water utilized by P.sylvestris var.mongolica in dry years was lower than that in normal years.3)Throughout the observation period,P.sylvestris var.mongolica primarily relied on deep soil water(WTD4:60-360 cm;WTD9 and WTD13:60-400 cm),and its contribution rate gradually increased with the deepening of the WTD(increasing from 34.6%in WTD4 to 52.6%in WTD13).Concurrently,the water use efficiency also increased(increasing from 102.7 μmol·mol-1 in WTD4 to 106.9 μmol·mol-1 in WTD13).4)The height,diameter at breast height(DBH),crown width,and stand density of P.sylvestris var.mongolica in areas with deep water table depth(WTD13)were significantly lower than those in areas with shallow water table depth(WTD4).[Conclusion]WTD and hydrologic year type drive P.sylvestris var.mongolica to develop a synergistic adaptation strategy of"root deepening-deeper water sourcing-enhanced water-use efficiency"by influencing soil water conditions,but growth becomes constrained in areas with deeper WTD.Based on this,during the vegetation restoration process,it is necessary to implement different vegetation allocation and density regulation measures according to the changes in water table depth,so as to effectively reduce the excessive consumption of deep soil water by vegetation construction and promote the sustainable development of ecological construction.