Root Drought Adaptation Characteristics Of Haloxylon Persicum That A Edificators In Gurbantunggut Desert

Haloxylon persicum is a desert dominant species in the arid region of northwestern China and a group species in the desert of Gurbantunggut,the second largest desert in China.It is a fine tree species for sand fixation,afforestation,drought tolerance,and saline-alkali resistance and plays a vital role in maintaining the stability of the desert ecosystem.Haloxylon persicum grows at a height of 30 m-50 m in the upper part of the dune,away from groundwater flowing sand dune or semi-fixed sand dunes.So it is a plant that is highly dependent on precipitation for survival.However,the precipitation in the ancient desert is unpredictable and the annual precipitation is less than 200 mm.So how does Haloxylon use extremely limited water,and it is necessary to study how the drought adaptation mechanism is formed.It has important scientific significance and broad application.prospect.In this paper,the Haloxylon persicum in the middle and upper part of the high dune is taken as the object of study.Through continuous sampling observation during the drought period,the adaptability of the root system to its morphology and physiological activity,and its relationship with the fluctuation of soil moisture content,etc.The reason of the drought adaptability of the Haloxylon persicum community in the Gurbantunggut Desert was analyzed.The result is as follows:1)As the soil moisture condition decreases,the total root biomass also decreases.However,the coarse roots(diameter>2 mm)showed little change,and the fine roots(diameter?2 mm)changed drastically.The total fine root biomass showed a trend of increasing first and then decreasing.It shows that with the increase of the degree of drought,Haloxylon persicum takes the overall reduction of consumption and adapts to the drought with the stability of the coarse roots and the fine roots.2)Fine roots exhibit very active stress and are highly correlated with soil moisture in terms of biomass,root weight density and root length density.At the same time,it showed that the closer the fine root biomass of the base stem of the plant was,the more the fine root biomass-rich soil layer migrated from 25 cm to the deep 100 cm soil layer in the vertical direction,and the soil water was enriched with the degree of soil moisture deficit.Regional distribution characteristics.3)Fine roots adopt effective morphological adjustments by comparing root lengths and specific surface areas to achieve greater resource capture in horizontal and vertical distributions.With the aggravation of drought,the fine roots in the soil layer near the base stem form a relatively stable state during long-term evolution due to the trunk current collection.The fine roots of the plots away from the base stem have no shade of the canopy,and they are the first to start deeper development when they are severely affected by environmental changes.They always have a high absorption efficiency.4)The fine roots spatially weave an efficient absorption network through the root density and root length density.In June,the fine root weight density and root length density were closer to the base stem of the plant at horizontal distance.In July,as the soil moisture content decreased,plants began to invest in remote space,increasing their own resource capture range,while also moving vertically downwards to obtain more adequate water.In August,due to the suppression of photosynthesis with the arrival of the hot summer,the biomass input of the underground part of the plant is also reduced,and at the same time,it is laid out to the deep soil layers with high soil moisture.However,there are fine root distributions in different soil layers in the three-dimensional space of the plant.This distribution is conducive to the roots of Haloxylon persicum can absorb water from any direction in the space,thus providing sufficient water for the aerial parts to maintain the normal physiological life of the plants.activity.5)From the perspective of root vigor,the root vigor(mainly white)less than 1 mm in diameter is less than the diameter of 1 to 2 mm.The average of the root vigor is less than the diameter >2 mm of root vigor(mainly black).The white fine root belongs to the pioneer root and was used to explore the absorption of water resources at the beginning of birth.As the drought intensified,the soil moisture status deteriorated,and the white root activity was gradually lost due to environmental influence.The brown-black root system evolved into a more drought-tolerant root system,which can resist drought and can also grow a large number of root hairs to absorb transport moisture and maintain high root activity when moisture conditions are affected by precipitation.Haloxylon persicum is an important survival strategy through this new root extension and the old roots' stable water absorption method to deal with extremely arid environments.Therefore,we believe that the mechanism of drought resistance adaptation of Haloxylon persicum is to stably distribute biomass under the canopy,gradually develop a thick root system with strong stress resistance,dynamically adjust fine root morphological characteristics and spatial distribution characteristics to absorb water and maintain functional activity.