| In this paper,taking the desert land around Miaoliangzi Reservoir-the discharge site of mine water-of Baijitan National Nature Reserve in Lingwu,Ningxia Province as the research object,combining field investigation with laboratory experiment to study the characteristics of the aboveground vegetation,soil properties and soil seed bank and the change rules of correlation at 4 distance gradients of near the reservoir(Sample plot A),0.5 km away from the reservoir(Sample plot B),1 km away from the reservoir(Sample plot C)and 2km(Sample plot D),discussed the effects of mine water on the aboveground vegetation,soil properties and soil seed bank in desert ecosystem,to study the ecological effect of mine drainage on desert ecosystem in arid sandstorm area,in order to provide a certain theoretical and practical basis for the restoration and reconstruction of desert ecosystem.The results of the study are as follows:1.With the increase of the distance from the mine reservoir,the number of aboveground vegetation species on the ground showed a decreasing trend,and the aboveground vegetation of the four distance gradients showed the majority of species of chenopodiaceae and compositae.Among them,16 species of plants belonging to 5 families and 15 genera,appeared in sample plot A.There were 14 species of plants in sample plot B,belonging to 6 families and 13 genera.There were 1 5 species of plants in sample plot C,belonging to 7 families and 14 genera.And there were 12 species of plants in sample plot D,belonging to 4 families and 11 genera.From the perspective of different life types,the four sample plots were dominated by annual plants,all of which were more than 40%,but the number of species tended to decrease with the increase of distance.Compared with sample plot A,sample plot B,C and D decreased by 12.5%,12.5%and 37.5%respectively.The number of perennial plants in sample plot B and D decreased by 25.0%respectively.There was no significant change in shrubs or subshrubs.2.Mine water had different effects on soil physical and chemical properties and soil enzyme activity.The distribution of soil particle size in the study area ranged from 0 to 2000 ?m.With the increase of the distance from the mine reservoir,the volume percentage of sand grains(50-2000 ?m)showed an increasing trend,and the volume percentage of sand grains was the highest in all the sample plots.Only in the sample plot A which is closest to the mine reservoir had clay(<2 ?m).Compared with the sample plot A,the percentage of sand volume in the sample plot D increased significantly at 0-10 cm,10-20 cm and 20-30 cm soil layers(P<0.05).The soil water content increased significantly with the depth of soil layer in the same sample plots(P<0.05),and decreased significantly with the distance in the same soil layer in different sample plots(P<0.05).Soil bulk density increased but not significantly(P>0.05).The pH and electrical conductivity of soil showed an inverted"V" type trend with the deepening of soil layer,and the difference between different soil layers was not significant(P>0.05).The same soil layer showed a"V" type trend with the increase of distance,and there was significant difference between different sample plots(P<0.05).The contents of soil nutrients except organic carbon gradually increased with the increase of the distance from the mine reservoir,and the contents of total nitrogen,total phosphorus,alkali-hydrolyzed nitrogen and available phosphorus were the highest in sample plot A and also decreased significantly with the increase of the distance(P<0.05).The activities of soil urease,invertase and catalase all decreased with the increase of distance to different degrees,in which the activities of soil urease and catalase decreased significantly(P<0.05),while the activities of soil phosphatase increased significantly(P<0.05).3.Mine water had a significant effect on the characteristics of soil seed bank.The soil seed bank density of sample plot A,B,C and D were 2184± 148.1 seeds m-2,1667 ± 88.2 seeds m-2,1017±83.3 seeds m-2,and 733± 16.7 seeds m-2,respectively.After being far away from the mine reservoir,soil seed bank density in sample plot B,C and D decreased by 23.7%,53.4%and 66.4%,respectively,compared with that in sample plot A,and there was significant difference between different sample plots(P<0.05).With the increase of the distance from the mine reservoir,the number of plant species in the soil seed bank showed a decreasing trend,and the number of annual plant species in the four sample plots accounted for a large proportion,all of which were over 45%,while the lowest was 47.7%and the highest was 85.7%.The number of annual plant species in the sample plots B,C and D decreased by 11.1.0%,22.2%and 33.3%,respectively.4.Mine drainage has a significant effect on the species diversity index of aboveground vegetation and soil seed bank,and has different effects on aboveground vegetation,soil seed bank and similarity between aboveground vegetation and soil seed bank.The shannon-wiener index,Simpson index,Pielou index and Margalef index of aboveground vegetation and soil seed bank all decreased significantly with the increase of distance from the mine reservoir(P<0.05).With the increase of the distance from the mine reservoir,the similarity of the aboveground vegetation,soil seed bank and the aboveground vegetation and soil seed bank decreased.The Sorensen similarity coefficient between aboveground vegetation was generally high,reaching a maximum of 0.84,showing extreme similarity,and a minimum of 0.62,showing moderate similarity.In general,the similarity level between soil seed Banks was medium,with a maximum of 0.67 and a minimum of 0.42.The similarity between aboveground vegetation and the soil seed bank at different distances is not high on the whole.The plot of sample A is 0.36,which is moderately dissimilar,and the rest are extremely dissimilar,among which the plot of sample C is the lowest,only 0.16.In addition,with the increase of distance,the number of common species between aboveground vegetation and soil seed bank in all kinds of lands decreased gradually,among which 6 species in A,3 species in B,and only 2 species in C and D appeared.5.Among the effects of soil physical and chemical properties and soil enzyme activity on the species diversity of soil seed bank,soil moisture,total nitrogen and catalase had significant or extremely significant positive effects on the species diversity of soil seed bank.In addition,phosphatase had extremely significant negative correlation with the species diversity of soil seed bank(P<0.01). |
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