Responses Of Soil And Vegetation In The Vegetation Restoration Processes Of Slag Yards In Qinba Mountain, China

Highway is a national fundamental infrastructure. The highway construction generateslarge numbers of excavation and filling slope which result in loose deposit soil and aggravatesoil and water loss. The vegetation restoration in slag yards becomes a hot issue in theresearch of man-made soil and water loss. In this paper, with the study approach of combiningfield investigation and laboratory analysis, we chose13sampling spots in the slag yards ofQinba Mountains with different vegetation restoration periods (0,2,5,7,15a) as our studyarea, and analyzed the measured data using analysis idea of substituting space for time. Foreach sampling spot, we surveyed soil physical and chemical properties, including soil enzymeactivity, vegetation growth status, soil seed bank types and quantity etc. Meanwhile, weclarified the soil and vegetation response pattern during vegetation restoration in the slagyards of Qinba Mountain, and discussed the similarity correlation between soil seed bankcondition and ground vegetation so as to provide soil and water conservation managementwith scientific reference. The results obtained were presented as follows:(1) Soil organic matter and total nitrogen in slag yards are low in the early stage ofvegetation restoration. Both increase as recover age increases, and the increase magnitudereduce gradually with the increase of recover age. For different recover ages in0-5cm soillayers of the slag yards, both soil available P and K content (P<0.01) show very significantdifference, and nitrate nitrogen had significant difference (P<0.05). For different recover agesin5-10cm soil layers, nitrate nitrogen, ammonium nitrate nitrogen and available K contenthave very significant difference. The activity of phosphatase and catalase do not changedsignificantly in vegetation recover process, and phosphatase has a stable increasing trend withthe increase of vegetation recover age.(2) Organic matter and total nitrogen content have very significant positive correlationfor all restoring ages (p<0.01). In0-5cm soil layers, soil total nitrogen content has verysignificant positive correlation with phosphatase and urease activity respectively, and has significant positive correlation with available K content; organic matter has very significantpositive correlation with available K content and urease activity respectively, and organicmatter had significant positive correlation with catalase activity.Soil enzyme activity and soil nutrient content have significant correlation (P<0.05). Therelativity closeness is in the order of urease>phosphatase>catalase. Urease activity has verysignificant positive correlation with soil organic matter and total nitrogen content respectively.It is shown that urease activity takes an important role in C and N conversion process.(3) Cover process can improve soil conditions in slag yard, and is conductive tovegetation recovery. In the comparison between the results based on cover-process and thatbased on un-cover-process, both soil organic matter and total nitrogen content show obviousdifference (soil organic matter and total nitrogen content based on cover-process are about1.5time of those based on un-cover-process respectively), and available nutrient content showsless difference. The cover-process can increase the organic matter in slag yards, but it can timprove the soil enzyme activity in the short time. After about5years, phosphatase andurease activity in slag yards with cover-process are significantly higher than that withun-cover-process.(4) In early stage of recovery, vegetation growth status is relatively poor, coverage rateand diversity index are also low, and the vegetation mainly composes of annual herb.However, artificial vegetation has a good growth status. Soil nutrient based on artificialvegetation restoration is less than that based on natural vegetation restoration. With theincreasing of recover age, the soil improvement based on artificial vegetation gradually showseffect and soil nutrient content is improved faster, because artificial recovery can increase soilbiomass. At the same time, with the increase of recovery age, perennial plant speciesgradually invades and increases their proportion in vegetation community. Thus, diversityindex increases as a result.(5) Seed bank and ground vegetation have a certain degree of similarity. However, thesimilarity shows different degrees for different restoration age and cover-process strategy (i.e.cover-process and un-cover-process). Cover-process restoration provides slag yards with thehighest similarity coefficient (up to0.45) after2years, while un-cover-process restorationleads to relatively bad similarity coefficient (0.05) after15years.