| In this study, we used the method of time-space mutual substitution in order to explore ecological effect variance in the process of vegetation restoration of burned areas. Compared with severely burned areas, Larix gmelinii plantation of different restoration years in severely burned areas of Great Xing’an Mountains were selected as research objects. Soil quality evolution, litter and soil hydrological effects, plant diversity and biomass distribution and microclimate variation were studied. Principal component analysis was used to evaluate the ecological effects in the process of vegetation restoration. The results showed that:(1) Soil physical and chemical properties fluctuated in the progress of vegetation restoration. Restored after twenty-four years, soil bulk density was smallest. While the content of soil total nitrogen, total phosphorus, available phosphorus and organic matter were the highest. Soil microbial biomass carbon content of 0-10 cm and 10-20 cm were 334.77～1764.34 mg/kg and 267.17～1123.07 mg/kg, while microbial biomass nitrogen content of 0-10 cm and 10-20 cm were 34.17～182.14 mg/kg and 23.45～84.81 mg/kg. Soil microbial biomass carbon and nitrogen contents increased with the increase of restoration years. Soil enzyme activity fluctuated in the progress of vegetation restoration. Soil enzyme activity of twenty-four years restoration were higher than severely burned areas. Soil microbial biomass and enzyme activity were closely related to soil nutrient contents. Soil bulk density, capillary porosity, hydrolytic nitrogen, sucrase and catalase were the dominant indicators of the assessment of soil quality in the process of vegetation restoration. Soil quality fluctuated in the process of vegetation restoration.(2) During vegetation restoration, litter storage capacity was 3.01～6.04 t/hm2, litter maximum water-holding capacity varied from 6.66 to 30.23 t/hm2. With the increase of restoration years, litter maximum water-holding capacity showed an increasing trend. Total litter modified interception depth was 0.51～1.45 mm, it increased with the increase of restoration years. Litter water-holding capacity (W) and water absorption rate (V) following W= k lnt+p and V=k tn equation. Soil saturated water storage was significantly higher than litter maximum water holding capacity, soil infiltration properties showed an increasing trend with the increase of restoration years. After twenty-four years restoration, soil initial infiltration rate, steady infiltration rate, cumulative infiltration of the first seventy minutes were the highest, stable infiltration time was longer, soil infiltration properties improved best. Horton model was best to fit the progress of soil infiltration, soil infiltration characteristics index had a good correlation with soil physical and chemical properties. Soil saturated water storage accounting for more than 97% of forest total holding water. After twenty-four years restoration, forest total holding capacity was 1180.93 t/hm2, and it was the highest. After sixteen years restoration, forest total holding capacity was 897.67 t/hm2, and it was the lowest. Soil retention water storage capacity and infiltration characteristics were the dominant indicators of the assessment of litter and soil hydrological effects during vegetation restoration. In the process of vegetation restoration, litter and soil hydrology effects showed a gradual increasing trend.(3) In the process of vegetation restoration, the species, Margalef richness, Shannon-Wiener, Simpson index, Pielou and Hurlber evenness indices of herb layer were higher than tree and shrub layers. Community species diversity.fluctuated, community species, Margalef richness index, Shannon-Wiener index and Simpson index of the plantation restored after twenty-one years was the highest. Pielou and Hurlber evenness indices of the plantation restored after thirteen years was the highest. During vegetation restoration, tree layer biomass was 3.636～115.603 t/hm2, and it gradually increased with the increase of restoration years. Shrub layer biomass and litter storage capacity fluctuated. The biomass of herb layer was 0.018～0.408 t/hm2, it decreased with the increase of restoration years. The biomass of community in the process of vegetation restoration was 10.80～123.96 t/hm2, and it gradually increased with the increase of restoration years. Community species, Margalef richness index, Shannon-Wiener index and Simpson index were significantly or very significantly negatively correlated with surface biomass. Community species, Margalef richness index, Pielou and Hurlber evenness indices were the dominant indicators of the assessment of plant diversity and biomass distribution.The recovery effect of plant diversity and biomass fluctuated in the progress of vegetation restoration.(4) In the progress of vegetation restoration, from June to September, monthly average soil temperature at 5 cm depth was 8.22～18.73 ℃, and monthly average soil temperature at 10 cm depth was 7.70～18.25 ℃. With the increase of restoration years, monthly average soil temperature, monthly maximum temperature, minimum temperature and soil temperature difference showed a gradually decreasing trend. Daily soil temperature variation at 5 cm depth was higher than 10 cm. Soil maximum temperature, minimum temperature at 5 cm depth occurs earlier than 10 cm depth. With the increase of restoration years, soil maximum and minimum temperature at 5 cm and 10 cm depth emerged later. Daily soil temperature variation showed a decreasing trend. Monthly air temperature and relative humidity from June to September were 7.67～18.92 ℃ and 58.71～82.90% in the progress of vegetation restoration. With the increase of restoration years, monthly air temperature decreased, monthly air relative humidity showed an increasing trend. Daily variation of air temperature was inverted "U" type, daily variation of air relative humidity was "U" type. Maximum and minimum air temperature and relative humidity emerged later. Daily air temperature and relative humidity variation showed a decreasing trend. Correlation analysis showed soil temperature, air temperature and relative humidity had significant correlation. Soil temperature and daily soil temperature differences were the dominant indicators of the assessment of microclimate factors in the process of vegetation restoration. During vegetation restoration, Larix gmelinii plantation trends to be more cloudy, cooler and wetter.(5) Soil quality index was not only the dominant indicators of the assessment of ecological effects, but also the major influencing factors in the process of vegetation restoration. In conclusion, after plantation restoration in severely burned areas, the ecological effects showed a gradual increasing trend with the increase of restoration years. |
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