| As an important organ for plants to obtain water and nutrients,fine roots are more sensitive and active than other roots,and their turnover process is the core pathway for soil organic carbon and inorganic carbon and carbon input plants.At the same time,the response of fine roots to the addition of exogenous nitrogen,especially the physiological and ecological aspects,will have a huge impact on the carbon sequestration and productivity of forest ecosystems.Picea schrenkiana is the only dominant plant species in the Tianshan forest in Xinjiang,and plays an extremely important ecological function.Therefore,this paper attempts to use the field in situ nitrogen addition test to explore the response of the underground part(fine root)of Xinjiang Picea schrenkiana spruce to the physiological and ecological processes of exogenous nitrogen addition,in order to reveal the external nitrogen addition to the.Basic research data is provided for the carbon sequestration and productivity of cedar forests.In order to reveal the physiological and ecological effects of nitrogen deposition on fine roots of Picea schrenkiana,the field nitrogen addition test was carried out,and the morphological characteristics of fine roots of Picea schrenkiana were determined after adding nitrogen fertilizer for one year(specific root length,specific surface area,root dryness).Material content,tissue density),fine root biomass,fine root physiological and biochemical characteristics(soluble protein content,soluble sugar content,fine root activity,free proline content,fine root tissue water content,malondialdehyde content),elemental chemistry Metrological indicators(carbon,nitrogen,phosphorus,carbon to nitrogen ratio,carbon to phosphorus ratio,nitrogen to phosphorus ratio),fine root metabolism characteristics(lignin,cellulose,soluble sugar and starch).The physiological characteristics of the fine roots of Picea schrenkiana in different diameter classes and different soil layers were analyzed,and the fine root differentiation rules of snow spruce in different meridians and different soil layers were explored.Through correlation analysis,the relationship between physiological and ecological characteristics of fine roots of Picea schrenkiana and soil environmental factors under different nitrogen input levels was investigated todetermine whether the input of exogenous nitrogen would change its correlation.The main conclusions are as follows:(1)Nitrogen addition has a significant effect on the physiological and ecological characteristics of fine roots of Picea schrenkiana.Nitrogen addition to the roots of snow spruce,the specific surface area of snowy spruce,soluble sugar content,fine root activity,free proline content The MDA content and other indicators reached a very significant level(P<0.01),and their interaction with the soil layer and the diameter level and the interaction of the three had no significant effect on the physiological and ecological characteristics of the fine root.(2)There is a certain differentiation rule of fine roots in different soil layers after nitrogen addition.A small amount of nitrogen input will significantly change its morphological characteristics,while there is no difference between nitrogen input and nitrogen-free addition.Nitrogen input has no significant effect on it,but there is a certain differentiation law between different soil layers.With the gradual deepening of the soil layer,it will increase first,then decrease or decrease first,then increase or decrease gradually.The fine root metabolism characteristics are different.Under the four nitrogen treatments,the soils first increased and then decreased.The fine-stoichiometric characteristics of all soil layers increased with the increase of nitrogen concentration.(3)There are certain differentiation rules of different fine roots after nitrogen addition,fine root morphology features a small amount of nitrogen input.It will significantly change its morphological characteristics.All the fine roots of the meridian grade increase with the increase of nitrogen concentration,and the morphology of fine roots increases first and then decreases.The biochemical characteristics of fine roots increase with the dose of nitrogen input,and the fineness of different meridians The roots showed a trend of increasing or decreasing gradually;the characteristics of fine root metabolism did not change significantly under the four nitrogen treatments of different meridians;all the mesoscales of fine roots showed a trend of increasing with the increase of nitrogen concentration.(4)The redundant analysis of the physiological and ecological characteristics offine roots and environmental factors showed that soil environmental factors were closely related to the physiological and ecological characteristics of fine roots.Fine root morphology,soil phosphorus,soil pH and soil soil conductivity were the main influencing factors of fine root morphology in the control group;soil phosphorus to phosphorus,soil bulk density,soil nitrogen and soil phosphorus in the low nitrogen group;In the middle nitrogen group,soil nitrogen ratio phosphorus,soil conductivity,soil water content,soil pH value and soil nitrogen;in the high nitrogen group,the main influencing factors were soil soil bulk density and soil nitrogen.Fine root biochemical characteristics,soil nitrogen ratio phosphorus and soil carbon were the main factors affecting the biochemical characteristics of fine roots in the control;soil nitrogen and soil carbon ratio phosphorus in the low nitrogen group,medium nitrogen group and high nitrogen group were the fine roots.The main influencing factor of biochemical characteristics.Fine root metabolism characteristics,in the control group,the importance of soil environmental factors on the characteristics of fine root metabolism was: soil carbon ratio nitrogen > soil carbon ratio phosphorus > soil nitrogen ratio phosphorus > soil carbon > soil nitrogen > soil water content > Soil bulk density>soil pH>soil conductivity>soil phosphorus,soil carbon to soil,soil carbon to phosphorus,soil nitrogen to phosphorus significantly affected;soil conductivity and soil pH in N1,N2 and N3 groups Soil nitrogen has a significant effect on the characteristics of fine root metabolism.The stoichiometric characteristics of fine roots,soil conductivity,soil pH and soil carbon ratio nitrogen significantly accounted for soil conductivity,soil pH and soil carbon ratio nitrogen main influence factors;soil nitrogen ratio phosphorus,soil conductance in low nitrogen group The main factors affecting the rate and soil nitrogen;soil water content,soil pH value and soil conductivity in the middle nitrogen group were the main influencing factors;the high nitrogen group and the medium nitrogen group were similar. |
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