Coupling Characteristics Of Damaged Populus Simonii Root Sprout Tillers And Soil Micro-environment In Wind-sand Mining Subsidence Area

In order to clarify the coupling relationship between damaged Populus simonii root sprout tillers and soil micro-environment in wind-sand mining subsidence area,we observed the root damage rate and types under different kinds of cracks as well as the spatial distribution range of damaged root sprout tillers at the cracks in the horizontal and vertical directions.We also measured the physical and chemical properties and microbial diversity of root soil in fractured zone,non-fractured zone,sprout tillers root and non-sprout root.At the same time,the main soil micro-environmental factors affecting the damaged Populus simonii root sprout tillers in the coal mining subsidence area were revealed,and the conclusions were as follows:(1)The horizontal roots of Populus simonii mainly existed in 0-60 cm soil layer,and the number of roots decreased gradually with the deepening of soil depth.The most damaged roots were found in the collapse type cracks and the number of root damage gradually decreased with the increase of root diameter class.The smaller the root split distance was,the more root damage was,and the root damage was the most serious when the root crack distance was less than 1 m.The main factors causing root damage of Populus simonii were crack width,dislocation gap and root crack distance.The wider the crack,the greater the dislocation difference,the more serious the root damage of Populus simonii,the farther the root split distance,the less the root damage.(2)The root morphology of budding tillers at the root damage of Populus simonii was L-shaped;from the budding tillers at the root skin split,the root system was inverted "T" shape.The number of budding tiller roots increased firstly and then decreased with the increase of root diameter.The minimum root diameter of budding tiller roots was2.36 mm and the maximum was 54.88 mm.The budding tiller roots of Populus simonii were the deepest in the soil layer of 25.50 cm,and the shallowest were exposed outside the soil layer.The roots of Populus simonii were the most easily to sprout in the soil layer of 0～10 cm,and the number of budding roots accounted for 65.38% of the total number of budding tillers.When the root crack distance was less than 50 cm,the maximum number of budding tiller roots was 44.53%.Slope position and crack type had no relationship with root diameter and root depth of the budding tiller roots of Populus simonii,but the root crack distance of the budding tiller roots at different slope position and crack type had significant difference(p < 0.05).Root damage was closely related to budding tiller roots.(3)Different types of cracks have different effects on soil physical and chemical properties in subsidence area.The water content and organic matter content of 0-20 cm topsoil under tensile,collapse and sliding fractures were all lower than those in non-fractured zone in the same slope,while the contents of soil p H,alkali-hydrolyzed nitrogen,available phosphorus and available potassium were all higher than those in non-fractured zone in the same slope.The root sphere soil water content(9.4～9.5%)and organic matter content(1.2～1.6 g/kg)of tillers under the three types of cracks were lower than those of non-tillers.The soil p H value(5.3～5.6),alkali-hydrolyzed nitrogen(104～107.3mg/kg),available phosphorus(8.2～8.8 μg/g)and available potassium content(11.2～14.7mg/kg)were all higher than those of non-tiller roots.(4)The abundance and diversity of bacteria and fungi communities in the root sphere soil of tillers were greater than those in the non-tiller root sphere soil of the three types of cracks.The richness of bacteria and fungi communities in different types of cracks was in descending order: sliding type > collapse type > stretch type.There was no significant change in bacteria and fungi community structure at phylum and genus level in the root sphere soil of tillers and non-tillers in various cracks.Soil water content,available phosphorus and organic matter content were the key factors affecting bacterial diversity in root sphere soil,while available potassium,p H and alkali-hydrolyzed nitrogen had relatively little influence.The content of available phosphorus and organic matter at cracks were the key factors affecting the diversity of root sphere soil fungi,while water content,available potassium,p H and alkali-hydrolyzed nitrogen had relatively little influence.