| The shrub forms nabkha by blocking wind-sand flow,which was the direct expression of the shrub’s wind-proof and sand-fixing ability.However,the adventitious roots formed after the shrub branches were buried in sand play an important role in the formation and development of nabkhas.With the continuous adaptation of shrub to stressed environment,adventitious roots will gradually develop into specific configurations to provide maximum adaptability for shrub.It is urgent to clarify the growth strategies of desert shrub adventitious roots under stress and the mechanism of soil environment affecting adventitious roots growth.To illustrate this response pattern,Nitraria tangutorum in West Ordos National Nature Reserve was studied,and the shrub was divided into three growth stages:the rudimental stage,developing stage,and stabilizing stage.A combination of total root excavation and root tracing was used to investigate their adventitious root morphology.Revealing response mechanism of the the adventitious root architecture of Nitraria tangutorum to the physicochemical properties of the nabkha soil.The main conclusions are as follows:1.The crown shape of Nitraria tangutorum in the study area was consistent with the shape of the bottom of the nabkha,and most of them are oval shaped.There was a significant correlation between the shrub morphology and nabkha morphology of Nitraria tangutorum(R~2=0.9730,P<0.0001),and it showed allometric growth.Related growth indexαIf it is less than 1.As the Nitraria tangutorum grows,its ability to block wind and sand continuously increases,and the final nabkha deposition speed was quicker than the growth speed of the shrub.At different growth stages,the adventitious root architecture of Nitraria tangutorum was a simple herringbone shape with a simple branching structure and was dominated by vertical roots,accounting for approximately52%.As the Nitraria tangutorum continues developing,the root diameters at all levels gradually increase,the shrub branches gradually becoming complex,and the proportion of vertical and inclined roots gradually increases,with a total branching rate of 1.04 in the Stabilizing stage.2.The soil in the study area was mainly fine sand,and 100～250μm was the main wind erosion particle size area.The shrub had obvious effect on sediment re-sorting and the effect increased with the growth of shrub.The shrubs reduce the solar radiation to the topsoil and reduce the rate of water evaporation.Therefore,the soil moisture content of the 0～20 cm soil layer in the nabkha is significantly higher than that of the vacant land between hills(P<0.05).There was a positive correlation between soil bulk density and soil depth.The average bulk density of CK soil from 0～40cm is 1.62g/cm~3,which is significantly higher than the average bulk density of soil from 0～40cm Nitraria tangutorum nabkha,which is 1.39g/cm~3(P<0.05).3.With the continuous growth of Nitraria tangutorum,the soil nutrient accumulation ability was enhanced,and soil nutrients were significantly improved(P<0.05).Developing stage and stabilizing stage of Nitraria tangutorum all showing the positive effect of soil nutrient accumulation,nutrient was significantly higher than that in stabilizing stage between the high space(P<0.05),while in the rudimental stage,only total phosphorus(TP)forming the nutrient accumulation4.There was a significant positive correlation between soil nutrients and root diameter and root branching rate(P<0.05),but there was no significant correlation between soil physical properties and spatial configuration parameters of adventitious roots in shrubs.The results of Redundancy Analysis(RDA)showed that organic carbon was the main factor affecting the configuration of adventitious roots.The results of the study can reveal the survival strategy of Nitraria tangutorum to adjust the adventitious root configuration to adapt to stress environments. |
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