| Haloxylon ammodendron is a small tree suitable for survival in arid areas,playing an important role in maintaining fragile ecosystems in arid desert areas.This article takes the Alxa Desert Haloxylon ammodendron plantation as the research object.Through a combination of field investigation,remote sensing interpretation,and indoor experiments,analysis methods such as variance analysis and linear regression are used to study the trend of area change,vegetation species composition,plant diversity changes,and soil physicochemical properties changes of Haloxylon ammodendron plantation with different planting years.The aim is to reveal the dynamic changes of the Alxa Desert Haloxylon ammodendron community,Provide a certain theoretical basis for artificial afforestation in desert areas in the future.The main conclusions drawn from the study are as follows:(1)The area of Haloxylon ammodendron plantation in the research area has increased rapidly,and the normalized vegetation index(NDVI)of Haloxylon ammodendron plantation showed an overall increasing trend from 2015 to 2018.The earlier the afforestation time,the greater the NDVI index;The density and new growth of the Haloxylon ammodendron plantation showed a quadratic curve trend,the height and crown diameter showed a linear growth trend,the ground diameter and biomass showed an exponential increase,and the vegetation coverage showed a logarithmic increase trend.(2)The flora of Haloxylon ammodendron plantation in the study area has 52 species in 45 genera of 16 families,and the life forms are mainly perennial herbs,annual herbs and shrubs.The average Margalef index is 0.7919;The average Gleason index is 1.0014,the average diversity index is 0.4770,the average dominance index is 0.9642,and the average evenness index is 0.1949,indicating that the species is relatively single,the dominance is obvious,the richness is insufficient,and the diversity index is low;With the increase of planting years,the diversity index shows an increasing trend.Artificial planting of Haloxylon ammodendron has a significant effect on the changes of plant species in herbaceous layers,with the order of effect size being: flowing sand dunes>rocky soil gentle hills>semi fixed sand dunes>rocky soil low mountains>gravel desert.Therefore,artificial cultivation of Haloxylon ammodendron forests in desert areas is beneficial for enhancing biodiversity,improving vegetation conditions in mobile sand dunes,and achieving the effect of desert management..(3)The soil moisture content of the artificial forest land of Haloxylon ammodendron shows an increasing trend with the increase of depth.The average soil moisture content of 0-100 cm is less than 1%.Due to the fact that the roots of Haloxylon ammodendron are mainly distributed in the soil layer below 60 cm,there is a high risk of survival in the early stages of artificial planting,and appropriate water replenishment is necessary;The soil salt content in the artificial forest land of Haloxylon ammodendron is generally high,with an overall characteristic of high in the northwest and low in the southeast.Compared with the control area,the anion content shows an increasing trend,while the cation content increases and decreases;The content of total nitrogen,total phosphorus,total potassium,available nitrogen,available phosphorus,and available potassium in the soil decreases with the increase of planting years,indicating that Haloxylon ammodendron consumes more and more soil nutrients during its growth process,while the content of organic carbon and organic matter does not show this trend.In order to improve the survival rate and preservation rate of artificial Haloxylon ammodendron forests,it is necessary to supplement fertilizers appropriately and increase soil nutrients after planting for about 3 years. |
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