| Collapse mound is the most harmful type of soil erosion in southern China, and collapse gully erosion is serious in Fujian Province. Collapse gully erosion resulted in hazards such as cutting the mountain, burying and pressing the fields, land degradation and deterioration of the regional ecological environment, which has become one of the major obstacles to wipe out poverty for people in mountainous district. Improvement of collapse mound has become the urgent problem to be addressed in the current scientific community of environment. Engineering measures were the main governance method for most of improvement of collapse mound at home and abroad, but these methods need high investment, and can not bring under permanent control, so find it difficult to promote. Many scholars believe that improvement of collapse mound should adopt bio-based governance model in the southern region of good hydro-thermal conditions. However, due to the different features of collapse mound types formed in different site conditions it makes the situation of vegetation growth different. For a long time, the blind mode of plant disposition is widely used for governance of different types of collapse mound in the South, which lack of scientific and technical guidance, so it is difficult to achieve the desired effect of treatment. Therefore, the study of restoration of vegetation and community succession law in different areas of collapsing erosion is necessary, which currently has become the major issues need to be addressed urgently in governance of collapsing erosion for the soil erosion department.In view of this, this study used areas of collapsing erosion in Fujian Province as the research object, and used the research mode of the combination of field surveys and information sorting, conducted in-depth investigations and studies of the areas of collapsing erosion in Fujian Province, selected the areas of collapsing erosion in the two serious soil erosion regions called Anxi County of Quanzhou City and Changting County of Longyan City located in areas of collapse mound of Fujian as research object. Vegetation recovery of slopes, channels and alluvial areas in different developmental stages of the collapse mound was investigated, plant communities of different governance models of collapse mound were surveyed, the relationship between physical and chemical nature of soil in different collapsing erosion and the process of vegetation restoration was studied, then vegetation rehabilitation and reconstruction principle in Eroded was deeply understood and enriched, and governance-related scheme was put forward. In short, the provision of data was supported for collapsing erosion research and comprehensive management and ecological restoration and reconstruction. The main findings included:(1)Through field survey and information sorting in relation to the status quo of the collapsing erosion in Fujian Province, it was found that: There were 26024 collapse mounds (60m2 and above) in the whole Fujian province. And it had a total area of 6406hm2, about 80% of the collapse mounds in whole province were active type; The number of small and medium-sized collapse mounds in whole province was large, but small in areas; Large-scale collapse mounds accounted for a small number, but the area of the collapse mounds accounted for 70.88% of the total area of whole province collapse. Among them, the collapse phenomenon of Anxi County was the most serious.(2)Survey of vegetation in slopes of different developmental stages of collapsing erosion area showed that: Differences in plant diversity were obvious in vegetation of collapse mounds in different developmental stages. Families and genera compositions in slopes were simpler than those in the control communities. Plant species in slopes of control areas were 13 families and 15 genera, with the development of collapse mounds, species at each stage decreased to 5～8 families and 5～13 genera; Families and genera compositions in channels were also simpler than those in the control communities. Plant species in channels of control areas were 15 families and 17 genera, with the development of collapse, plant species declined to 12 families and 13 genera at the early stage, then declined to 4 families and 6 genera at the middle stage, and plant species in channels were 6 families and 8 genera at late collapse, plant species were 10 families and 12 genera at the end; Families and genera compositions in alluvial areas were simpler than those in the control communities, too, plant species in alluvial areas of control areas were 10 families and 14 genera, with the development of collapse mounds, species at each stage decreased to 4～8 families and 7～10 genera, which showed that collapsing erosion was beneficial for plant growth in the alluvial areas. Survey of plants in collapse mounds found that the importance value of dichotoma had always been at the forefront so that dichotoma were the dominant species.(3)The research results based on vegetation diversity of different parts during the different developmental stages of the area of collapsing erosion showed: With the collapsing erosion happening, the vegetation diversity first descending then ascending. On basis of the two transformation trend of the Diversity Index of slope communities, the Simpson Index (D) and Shannon-Wiener Index (H') showed"V"type in increasing tendency, firstly increased and then decreased with the development of the slope collapse. The Pielou Evenness Index of the communities of slope collapse was found: 0.82, 0.80, 0.84 and 0.93 respectively, on the smaller differentiation of dominance but greater evenness level. It showed the"V"type of the variation tendency of the Evenness Index of communities of brush and herb. It revealed that the species of the community plants was simple in the area of collapsing erosion, mostly the dichotomy forked fern. On basis of the two transformation trend of diversity index of the different developmental stages of the channel regions of collapsing erosion, the Simpson Index (D) and Shannon-Wiener Index (H') were showed less than the control area, 0.893 and 2.447 respectively. The Diversity Index of the different developmental stages of the area of collapsing erosion totally appeared increasing"V"type. The Pielou Evenness Index ranged from 0.91 to 0.93 from early to terminal stages, with 0.76 in holding period. This showed that the vegetation were on serious degradation conditions, therefore the treatment should be taken before the mid-term. Based on the two transformation trend of diversity index of the different developmental stages of the alluvial areas of collapsing erosion were appeared increasing"M"type, the same with the Simpson Index (D) and Shannon-Wiener Index (H'), among which vegetation diversity of mid-term were lowest, 0.78 and 1.71 respectively. During the mid-term of the development, large amount of alluvium of slope and channel were pushed into the alluvial fan, which made both the species of vegetation and the Diversity Index declined, but this created the better condition for vegetation residing and growth especially after the collapsing erosion terminated. The highest Pielou Evenness Index were 0.92 on terminal stage, against the lowest 0.81 in holding period. The variation tendency between the Evenness Index and the Diversity Index were slightly different.(4)The soil physical properties under different development stages in collapsing mound showed that soil bulk after the collapsing erosion happened is higher than the soil bulk of the control(1.35g/m3)that size order is middle stage>last stage>initial stage=terminal stage, but the size order of moisture capacity of soil and capillary is different from the order of soil bulk. The order of soil bulk in gully channel that is last stage >terminal stage >initial stage >middle stage . The soil bulk of 0～20cm in control is 1.24 g/m3. The soil bulk whose size order is last stage> terminal stage> initial stage> middle stage is minimum in alluvial district under the middle stage of collapse erosion.(5)The soil chemical properties under different development stages in collapsing mound showed the pH value is lower than the value of control whose size order is: terminal stage>last stage> middle stage>initial stage. There is significant difference among the soil total nitrogen of different development stages of collapse mound. The law of the change of total P, available P, total K in collapsing slope is not obvious. The order of total N is : terminal stage> initial stage >last stage > middle stage and organic matter and available nitrogen is : initial stage > terminal stage >last stage > middle stage. It showed the change of soil erosion intension is obvious. The range of pH value is 4.86～6.00; the order of total nitrogen, available nitrogen and organic matter is initial stage > terminal stage >last stage > middle stage; the available nitrogen under the initial and middle stage is 58.3% and 12.1% higher than the control, but the available nitrogen under the last and terminal stage is 60.9% and 54.4% lower than the control area. The law of the change of total P, available P, total K is not obvious, but the available K is gradually decreasing as the development degree under the first stage of collapsing mound.(6)The law of vegetation succession through different governance model showed that the species is increasing to 18 by planting bahia grass. By drilling the lespedeza, the species is increased to 13. if using blockading administration, the species is increased to 21.The species is increasing to 21 when in 1980s planted masson pine in Chang ting and open forest transformation. The soil bulk is decreasing 16.5%～23.2% comparing to the control. The non-capillary pore, total porosity, void ratio of model A is 1.72,1.14 and 1.81 times than the control. The non-capillary pore, total porosity, void ratio of model B is 1.98,1.19 and 2.14 times than the control. The >0. 25mm water stable aggregate of model A is 1.96 times than the control. The >0. 25mm water stable aggregate of model B is 1.86 times than the control. And there are also development under different degree in the tree layer, shrub layer and herb layer and the community structure is tending to complexity. The improvement of biodiversity is playing the greatly important part in forming community environment and contributing to the future development of ecosystem. |
