| The Wenchuan Earthquake and its secondary disaster finally led to a huge damage to the disaster areas and caused severely vegetation and soil damage,and resulted in serious soil erosion and ecosystem destruction.To understand the soil characteristics differences between vegetation destroyed areas and undestroyed areas and to estimate the restoration condition and the potential of damaged vegetation-soil system,this study set up two ecological restoration areas as study areas in Hanwang town(subtropical humid monsoon climate areas)and Weizhou town(semi-arid dry and hot valley climate areas)in Sichuan Province,the restored destroyed areas and destroyed areas without restoration were treatment sites,and the undestroyed areas were control sites.We made vegetation surveys and got soil samples in the two study areas in May,2014,and determined the soil physical,chemical and biological indicators.Based on the determined data,we analyzed the change characteristics of soil indexes above and soil fertility quality in restored destroyed areas and destroyed areas without restoration and undestroyed areas,and we wanted to understand the impact of ecological restoration in disaster areas.The results and conclusions were as follows:(1)Change characteristics of soil physical properties of typical disaster areas inpreliminary stageSoil moisture contents in Hanwang areas were higher than that in Weizhou areas,especially Hanwang undestroyed areas were significant higher than itsdestroyed areas and all Weizhou areas.There was no significant difference between the bulk density of Hanwang areas,but that were significantly showed a trend that undestroyed areas were lower than destroyed areas in Weizhou zreas.Hanwang had the highest clay contents in the undestroyed areas,but that of Weizhou was in destroyed areas without restoration.Silt content showed undestroyed areas>restored destroyed areas>destroyed areas without restoration both in Hanwang and Weizhou areas,and sand contents were the lowest in the undestroyed areas in the same climate zone.Silt contents were the lowest in the Hanwang areas,and sand contents were the lowest in the Weizhou areas between different climate zones.(2)Change characteristics of soil chemical properties of typical disaster areas inpreliminary stageSoil pH in destroyed areas were lower than that in undestroyed areas both in two climate zones,organic carbon in Hanwang and total nitrogen contents in Hanwang and Weizhou areas were significantly showed a trend that undestroyed area>restored destroyed areas>destroyed areas without restoration,and there were no significant difference of organic carbon between all Weizhou areas,and C:N ratio were significant different both in Hanwang and Weizhou areas.Total phosphorus in undestroyed areas were significant higher than destroyed areas both in two climate areas,but the difference of total potassium were not significant.Soil available nutrients were highest in undestroyed areas while lowest in destroyed areas without restoration both in Hanwang and Weizhou areas.Soil pH and C:N ratio were significantly different between undestroyed areas,and C:N ratio and phosphorus elements were significantly different between destroyed areas of two climate zones.(3)Change characteristics of soil enzymes properties of typical disaster areas inpreliminary stageSoil invertase and dehydrogenase in undestroyed areas were significantly higher than destroyed areas of Hanwang areas,and invertase,urease,alkaline phosphatase,dehydrogenase in restored destroyed areas were significantly higher than destroyed area without restoration of Hanwang areas.Soil invertase,cellulase,alkaline phosphatase,dehydrogenase in undestroyed area were significantly higher than destroyed areas of Weizhou areas,and only invertase in restored destroyed areas were significantly higher than destroyed area without restoration of Weizhou areas.Soil dehydrogenase of undestroyed areas and restored destroyed areas in Hanwang were higher than that in Weizhou areas,while invertase,urease,alkaline phosphatase of destroyed area without restoration were higher in Weizhou areas.(4)Change characteristics of soil microorganism properties of typical disasterareas in preliminary stageSoil microbial biomass,actinomycetes,and carbon source metabolic diversity in Hanwang undestroyed areas were higher than Hanwang destroyed areas,as followed as soil microbial biomass carbon contents,actinomycetes in Weizhou areas,but the differences of carbon source metabolic diversity were not significant in Weizhou areas.Compared between two climate areas,there were significantly differences of carbon source metabolic diversity between destroyed areas,while the differences of that between undestroyed areas were very less,and there were few differences of microbial biomass and numbers between undestroyed areas.(5)Correlation between soil physical,chemical and biological properties oftypical disaster areas in preliminary stageThere were poor correlations between soil physical properties except soil moisture content and clay content.Soil physical properties had correlations with other indicators,and the bulk density was the worst.Most of the correlations between soil chemical properties and other indicaters were significant,especially that were highly significant of organic carbon,total nitrogen and available nutrients.In soil biological characteristics,there were significant and above correlations between most of soil enzymes and soil microorganism,and most of the correlations between enzymes and microorganisms were significant.(6)Change characteristics of soil fertility quality of typical disaster areas inpreliminary stageWe calculated the 30 types of indexes by the methods of comprehensive indexes and factors analysis.The soil fertility quality mean scores showed significant differences in Hanwang undestroyed areas(0.745,0.786)>Weizhou undestroyed areas(0.284,0.165)>Hanwang restored destroyed areas(0.069,0.085)>Weizhou restored destroyed areas(-0.135,-0.179)>Weizhou destroyed areas without restoration(-0.326,-0.382)>Hanwang destroyed areas without restoration(-0.637,-0.475).The results showed the soil fertility quality in subtropical humid monsoon climate areas(Hanwang)were better,and the soil fertility quality of destroyed areas were lower than that of undestroyed sites in both two climates zones,and the effects of artificial ecological restoration were more significant in Hanwang areas than that in Weizhou areas.Then we established the regression equation between two methods and we found the simulation was significant,so that were available to assess the restoration conditions by the two methods above in degenerated soil ecosystem in earthquake disaster areas.(7)Improved methods of soil fertility quality assessmentWith 15 kinds of soil indexes and the comprehensive index and factor analysis methods,we got soil fertility quality values as Hanwang undestroyed areas(1.151,1.131)>Weizhou undestroyed areas(0.497,0.453)>Hanwang restored destroyed areas(0.101,0.103)>Weizhou restored destroyed areas(-0.192,-0.206)>Weizhou destroyed areas without restoration(-0.645,-0.630)>Hanwang destroyed areas without restoration(-0.912,-0.851).The trend of soil fertility values after indexes selecting was similar with the results calculated by non-selected indexes,indicating that the use of screening index for fertility quality evaluation analysis was feasible. |
PDF Full Text Request