| In the process of ecological restoration,vegetation selection is of great significance.With lush branches and leaves and well developed root system,Chinese dwarf cherry is a kind of shrub species having strong adaptability to endure cold,drought and barren conditions.Recently,Chinese dwarf cherry has been exploited for ecological restoration and reconstruction in multiple regions,but its ecological effects have not been systematically evaluated.In this study,four different zones with fragile ecosystems were slected as test plots for Chinese dwarf cherry planting,the Loess Hilly Gully Region of Liulin,two reclamation areas of Pingshuo and Xiyang opencast coal mines,the transformation area of Zuoyun beach land.Through difference analyses between rhizosphere and non-rhizosphere soil of Chinese dwarf cherry,soil under the canopy and in inter-row of Chinese dwarf cherry bushes in the same soil layer,and soil of different layers,characteristics of soil nutrients,enzyme activities and microorganisms in different ecological fragile areas were explored after Chinese dwarf cherry planting.Comprehensive evaluation on soil quality was also carried out via the principal component analysis,in order to provide theoretical basis for Chinese dwarf cherry as a new ecological restoration tree species.Soil characteristics analysis among different growth stages of Chinese dwarf cherry in Loess Hilly Gully Region were studied as well,in order to reveal the dynamic changes of soil characteristics after Chinese dwarf cherry planting.The main results were as follow:(1)Studies of different ecological fragile areas and different growth stages of Chinese dwarf cherry on soil characteristics indicated that rhizosphere effects existed widely except several indexes of 0-20 cm soil layer under the canopy of Chinese dwarf cherry bushes(UCC20).And the rhizosphere effects were mainly manifested in soil pH,electrical conductivity,enzyme activities(except catalase),soil microbial quantity and soil respiration intensity,among which the rhizosphere effect of soil microbial quantity was particularly significant.(2)Improvement degree on soil quality after Chinese dwarf cherry planting varied from region to region,and the improvement of Loess Hilly and gully area was the most significant.In Loess Hilly Gully Region,multiple indexes of soil under the canopy of Chinese dwarf cherry(UCC20 and UCC40)were improved in different degrees,such as soil aggregate structure,pH value,nutrients content(except available phosphorus),enzyme activities(except the catalase of UCC40),microbial quantity,respiration intensity and etc.However,improvement of reclamation areas of Pingshuo and Xiyang opencast coal mines and the transformation area of Zuoyun beach land were only reflected on soil aggregate structure,pH value,electrical conductivity(except the 20-40 cm soil layer of reclamation area of Pingshuo opencast coal mine),a minority of nutrient indexes and microbial quantity.In addition,comprehensive evaluations on soil quality in different ecological fragile areas were also carried out according to scores of first three principal components and their proportions,results given as follow.In Loess Hilly Gully Region of Liulin and the reclamation area of Pingshuo opencast coal mine,comprehensive quality of soil under the canopy of Chinese dwarf cherry bushes was higher than that of corresponding soil layers in inter-row of Chinese dwarf cherry,and comprehensive quality of soil in 0-20 cm soil layer under the canopy of Chinese dwarf cherry bushes(UCC20)was higher than that of 20?40 cm soil layer(UCC40).Although in the reclamation area of Xiyang opencast coal mine and the transformation area of Zuoyun beach land,comprehensive soil quality of 0-20 cm soil layer under the canopy of Chinese dwarf cherry bushes(UCC20)was similar to that of soil in inter-row of Chinese dwarf cherry(IRC20),while comprehensive soil quality of 20?40 cm soil layer under the canopy of Chinese dwarf cherry bushes(UCC40)was much higher than that of 20?40 cm soil layer in inter-row of Chinese dwarf cherry(IRC40),thus improvement function of Chinese dwarf cherry on soil quality was not negligible.In summary,the planting of Chinese dwarf cherry enhanced the comprehensive soil quality of all four ecological fragile areas in different degrees.(3)In addition,results of Liulin Loess Hilly Gully Region also showed that improvement effects of Chinese dwarf cherry and Pinus tabulaeformis plantation had their own respective advantages.Fraction of 0.25 mm-2.0 mm soil aggregate,alkali-hydrolysable nitrogen content,total phosphorus content and enzyme activities of soil under the canopy of Chinese dwarf cherry bushes were superior to those of P.tabulaeformis plantation,while fraction of>2.0 mm soil aggregate,soil moisture content,electrical conductivity,microbial quantity and other nutrient contents were inferior to those of P.tabulaeformis plantation.(4)Results of the principal component analysis indicated that,among different ecologically fragile areas,similarities and differences of key factors which resulted in differences among different soil samples coexisted.The organic matter content was presented as the common key factor in four different ecological fragile areas.In addition,mutual key factors of these ecological fragile areas also included soil basal respiration intensity,urease activity and soil moisture content(except for the transformation area of Zuoyun beach land),bacterial and actinomyces quantity(except for Liulin Loess Hilly Gully Region),and total nitrogen content(except for the reclamation area of Xiyang opencast coal mine).(5)Except some available nutrients(such as alkali-hydrolyzable nitrogen and available potassium),dynamic changes in soil moisture content,pH,electrical conductivity,available phosphorus and organic matter content,enzyme activities and soil microbial biomass were relatively consistent among different treatments.Soil moisture content of all treatments showed the valley value and the lowest value in 6.16(pit-hardening stage),while the highest value appearing in 8.21(mature stage)or 10.30(defoliation stage).Similar to the soil moisture content,pH values of all treatments had the lowest value in 6.16(pit-hardening stage),and showed the highest value in 8.21(mature stage).Content of organic matter showed a trend that decreased in the early stage and then accumulated,and the lowest value appeared in 8.21(mature stage).Phosphorus content of all treatments showed the highest value in 8.21(mature stage),while the lowest value in 10.30(defoliation stage),except for the rhizosphere of Chinese dwarf cherry.Contrary to dynamic changes of soil pH,peak values of electrical conductivity,soil enzyme activities(except catalase),soil microbial biomass mostly appeared in 6.16(pit-hardening stage),while valley values appeared in 10.30(defoliation stage).(6)Although soil indicators varied along with changes of stages,the soil quality was improved by planting Chinese dwarf cherry in loess hilly gully region,which did not strongly depend on the season.In conclusion,there were certain improvement in all four ecological fragile areas after Chinese dwarf cherry planting.However,the improvement degree varied from region to region,in which the improvement of Loess Hilly and gully area was the most significant.And the improvement on soil quality of Chinese dwarf cherry planting was not strongly depend on the season. |
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