| Ground fissures caused by coal mining subsidence are not only a serious geological hazard,but also affect the growth and development of vegetation in the mining area and damage the mining ecosystem.To investigate the quantitative influence of coal mining subsidence fractures on the source of water uptaken by Artemisia Desertorum,the simulated precipitation tests of isotopically-labeled water were conducted in three test zones influenced by coal mining subsidence fractures to different degrees on 22312-working face of Huojitu mine field in Shendong mining area.The three test zones were divided according to the distance between Artemisia Desertorum and the fractures,where the coal mining subsidence conditions were classified as the non-mining zone（where the Artemisia Desertorum was over50 m away from the cracks in the test area）,the zone affected by coal mining subsidence without obvious fractures（hereinafter referred to as fracture-free zone,where Artemisia Desertorum was more than 5 m away from the fractures in the test area）and the fracture zone（where the fractures with a width of about 15 cm passed through the test area at 0～20 cm away from Artemisia Desertorum）.Theδ18O andδ2H isotope contents of soil water and plant xylem water in different soil layers were measured separately,and the water uptake ratios of plants were calculated using the direct comparison method.The Mix SIAR Bayesian mixture model method and the influence of the spatial distribution of coal mining collapse fractures on plant water sources was investigated by combining the methods of spatial analysis.Meanwhile,the interannual and seasonal variations of Artemisia Desertorum growth in the study area and the correlation with meteorological factors and groundwater burial depth were analyzed using NDVI data.The study of plant water absorption mechanism has important reference significance for the research of the implication of coal mining on vegetation growth and ecological restoration in mining areas.The main conclusions are as follows:（1）On the annual scale,NDVI values showed a low positive correlation with precipitation（r=0.744,p=0.090）and NDVI values showed a low positive correlation with groundwater depth of burial.On the seasonal scale,NDVI values showed significant positive correlation with precipitation in both spring and autumn（p<0.05）,with the highest correlation in autumn（r=0.84）,while there was no significant correlation between NDVI values and groundwater depth of burial in all seasons.By establishing the statistical relationships between NDVI values and meteorological factors and groundwater,it was determined that the main influencing factor for the growth of Artemisia Desertorum in the study area in autumn was precipitation.（2）By analyzing the changes of soil water content before and after simulated precipitation,it was found that the soil water transport patterns were different in different test zones.The soil water content in the non-mining zone and the fracture-free zone decreased with the increase of soil depth,and only piston flow existed.The water content of the surface soil in the fracture zone was lower and preferential flow existed.The percentage of preferential flow was 18.2%.This indicates that the fissures formed by coal mining collapse will change the mode and rate of soil water transport.（3）By analyzing the contribution of soil water at different depths to water uptake by Artemisia Desertorum,it was found that in the non-mining zone,soil water at 10～20 cm depth provided 59.7%of water for Artemisia absinthium,which was the main source of water uptake by Artemisia Desertorum in this zone.In the fracture-free zone,Artemisia Desertorum absorptively absorbed water mainly from the 0～10 cm soil layer（39.4%）and 40～60 cm soil layer（46.6%）.In the fracture zone,85.9%of water absorbed by Artemisia Desertorum came from the 40～60 cm soil layer,indicating that the water source of the plant was almost entirely in the deep soil layer.This indicates that the coal mining collapse cracks affected the distribution of plant root biomass,which in turn affected the uptake of soil water by plants.（4）By establishing OLS models and GWR models,the spatial relationship between the water uptake sources of Artemisia Desertorum and the distance between Artemisia Desertorum and fractures in different experimental areas was further analyzed.The results showed that at0～10 cm soil depth,the non-mining zone showed a negative correlation and the fracture-free zone and the fracture zone showed a positive correlation;at 10～20 cm and 20～40 cm soil depth,the three zones all showed a positive correlation;at 40～60 cm soil depth,the three zones all showed a negative correlation. |
