Evaluation On Soil Ecological Benefits In Different Land Use/vegetation Restoration In The Key Region Of The Upper Reaches Of Minjiang River-valley

Soil is the important foundation of human existence and development. Good soil structure, plentiful nutrient contents and good bioactivity are the basis of biochemical circulation in the process of soil ecology and the important security of vegetation growth and reproduction. Soil ecological benefit, the comprehensive expression of soil quality and the environmental factors, play a direct compact on the ecological function and ecological system stability. Due to the impact of extreme climate event and the irrational human activities, the ecological environment has been destroyed seriously, the trend of water and soil erosion has intensified, and the soil ecological benefits has been reduced. In recent years, many great ecological projects(such as China Natural Forest Conservation Program, Conversion of Cropland to Forest) have been implemented, it has not only played a significant role in improving the ecosystem and achieving sustainable development in China, but also make great contributions to safeguarding global ecological security, Soil ecological benefits evaluation can provide the basic data to the rational long-term planning for ecological projects. The drought river valley of the upper reaches of Minjiang River, has a bad environmental condition because of complicated and variable topography and landform, which forms local microclimate easily. Coupled with man-made destruction, degeneration of natural vegetation, serious soil erosion and poor soil, the upper reaches of Minjiang River is a typical ecologically fragile area which affects the restoration of vegetation and repair of ecological system seriously. With the implementation of "natural forest protection", "returning farmland to forest" and the other of major national ecological restoration project carrying in recent years, it has been a lot of types of land use/vegetation restoration in the region. To some extent, these vegetation types alleviate ecological degradation and improve ecological benefits.But now, how is the ecological recovery benefits of different types of land use/vegetation restoration and how to evaluate the restoration of the ecological system are the focus of research. We selected six different land use types, primeval secondary forest, artificial forest, grassland and orchard, nursery land and farmland, including 22 vegetation restoration types in the core area of drought river valley of the upper reaches of Minjiang River as the research object and measured the environmental factors, soil physical and chemical properties and soil biological activity which related to soil significantly. Based on the principal component analysis, with the help of the basic principles of fuzzy mathematics and RDA mathematics, we built the membership function between each evaluation indexes and soil ecological function, to evaluate the ecological benefits of soil among different types of land use/vegetation restoration by the Factor Analysis Method" comprehensively so as to determine whether the type is superiority or not. Results are as follows:(1) In different land use/vegetation restoration in the key region of the upper reaches of Minjiang River-valley, vegetation coverage is significant different (P< 0.05). There are significant difference of species diversity among different types of shrub layer and herb layer, the species richness and diversity index of the shrub layer was obviously higher than that of the herb layer. The species diversity index (S), richness index (R), Simpson dominance index (D) and Shannon-Wiener diversity index (H) of shrub layer and herb layer in the original secondary forest of Quercus acutissima Carruth are significantly higher than that of in artificial afforestation forest, grassland, orchard, nursery land (P< 0.05), and the species richness and diversity index in farmland is the lowest (P< 0.05); With increasing restoration time, all of the species diversity indexes in shrub layer and herb layer increased. However, the variation tendency of evenness index (J) in both shrub layer and herb layer are different from that of the indexes of S, R, D, H, the highest is in the cupressus chenggiana artificial restoration forest. Under different types the water holding, volume and the maximum water holding capacity of the litters are significant difference, and the water holding capacity is the best in the original secondary forest of Quercus acutissima Carruth, the worst in the farmland of Zea mays-Glycine max. Restoring afforestation can significantly increase the volume and water holding characteristics of the litters(P< 0.05), and with the increasing of restored years, litter volume increased obviously and the water holding capacity also increased.(2) Index of soil anti-scourability is significantly affected by land use/vegetation restoration types (P< 0.05), the highest is in the original secondary forest of Quercus acutissima Carruth followed by Alangium chinense (Lour.)Harms secondary forest and that in farmland is the lowest; Soil bulk density of different types of land use/vegetation restoration increased with the increasing of soil layer, however, soil porosity and aeration showed opposite change tendency, and all these indices were significantly different in the surface layer and the subsurface level (P< 0.05); The change tendency of soil bulk density, the non-capillary porosity, total porosity and aeration in different types of land use/vegetation restoration showed that the original the original secondary forest of Quercus acutissima Carruth is optimal performance, the worst is in farmland and the differences were significant (P< 0.05). The capillary porosity, which is influenced by soil parent material and soil forming process, is not significant influenced by different types of land use/vegetation restoration and its variation coefficient of upper and lower soil layer were 7.96%and 7.83%respectively that were all the weak variation level. The capacity of soil water holdup showed significant difference among different types of land use/vegetation restoration (P< 0.05). The roughly performance of soil natural moisture, maximum moisture capacity, field capacity, capillary capacity and soil infiltration rate is:secondary forest land> nursery land> artificial restoration plant area> grassland> orchard land> farmland and soil drainage ability is the best in nursery land; With the increase of recovery time, index of soil anti-scourability, bulk density, porosity, aeration, storage and drainage capacity, permeability showed significantly increasing trend (P< 0.05).(3) Soil chemical properties presented significant differences on the soil spatial, although the increase in soil nutrient content decreased with soil depth, showing " surface-aggregation " of soil nutrients, soil pH increased with soil depth increased.Soil nutrient content were significantly affected by land use types(P<0.05), soil organic carbon under different land use types or vegetation type, total N, P, K content of nature regeneration of the original secondary forest of Quercus acutissima Carruth exhibited significantly the highest (P<0.05), followed by nursery, orchard and crop land was significant minimum(P<0.05); with the increase age of vegetation restoration, the soil organic carbon and nutrients content accumulation increase. Hydrolysis soil N, available P, available K content showed a crop land and orchard farming land is higher than the nursery, significantly higher than the original forest and grassland, artificial afforestation was significantly low.(4) With soil depth increasing, in addition to secondary shrub land, the microbial number showed a significant decreasing trend (P<0.05); microbial biomass carbon and microbial biomass nitrogen content also showed significantly reduced (P<0.05); soil enzyme activity also decreased with increasing soil, However, the extent of decline is not obvious. Different land use or vegetation restoration under the type and quantity of microorganisms, microbial biomass, soil enzyme activity and soil level of each diameter of fine root biomass was significantly highest in the original forest, nursery, returning farmland to grassland and relatively high minimum crop land (P<0.05), secondary shrub land because of poor soil ecosystem bad environment, significantly reducing the activity of soil microbial communities and soil enzyme activity (P<0.05)(5) Different land use types or vegetation types following soil environmental factors, among soil physical properties, soil chemical properties and soil biological activity related indicators correlation was significant or very significant level, through redundancy analysis, most of "environmental factors" can explain right "species factor" the greater the degree of influence that can explain the "species factor" more than 85% of the variation. The indicators of soil environment were the effective factors of soil physical properties, chemistry properties and ecological activities which can explain 98.96%,85.78% and 95.05% of the total variance in soil properties separately. The indicators of soil physical peroperties can explain 64.24% and 89.41% of the total variance in soil chemistry properties and ecological activities. The indcators of soil chemistry properties can explain 88.82% of the total variance in ecological activities.(6) In accordance with the evaluation principles, We combined with the local practicality in the upper reaches of the Minjing river-valley, and choose 4 kinds of combination, a total of 40 evaluation indexes about the soil evvironmental indicators, soil physical properties aggregated, soil chemistry properties aggregated,and soil ecological activities aggregated. Then the single indicator ecological function models of soil ecological benefits were established. We established Medium type(or Parabola) function model for pH, and Minimum-Best type (or overturned "5")function model for soil bulk density, and Maximum-Best (or "5") function model for the other indicators. Evaluation ecological benefits in the arid valley of the Minjiang River core soil, using principal component analysis and factor analysis, respectively, on soil ecological benefit of all kinds of indexes analysis, EBI, FBI, CBI, BBI were the highest in the primitive forests, crop land is lowest (except CBI), and with the increase in recovery the time of afforestation, the increase of soil ecological benefit evaluation indexes are various, and positively correlated with recovery time(P< 0.05). And based on this, a simple method for performance prediction by using linear regression analysis is put forward, we found there is a very significant correlationship between IBI and SEBI{P< 0.01). According with the SEBI, we can determine the superiority and inferiority of the soil ecological benefits in different land use/vegetation restoration types, the order is as follow:the original secondary forest of Quercus acutissima Carruth> the secondary forest of Alangium chinense (Lour.) Harms> the restored foest of Alangium chinense (Lour.)Harms (45a)> the nursery land ofTaxus chinensis> the grassland> the restored foest of Pinus tabulaeformis Carr. (36a)> the restored foest of Cupressus chengiana(26a)> the restored foest of Robinia pseudoacacia L. (42a)> the restored foest of Platycladus orientalis (L.) Franco(34a)> the orcharding land of Malus domestica-forage grass> the orcharding land of Cerasus pseudocerasu-natural grass> the restored foest of Cupressus chengiana (15a)> the restored foest of Cerasus pseudocerasu (18a)> the restored foest of Cupressus chengiana(6a)> the orcharding land of Zanthoxylum bungeanum Maxim.> the secondary shrub forest> the restored foest of Cerasus pseudocerasu (11a)> the restored foest of Cerasus pseudocerasu (4a)> the orcharding land of Cerasus pseudocerasu-Glycine max> the orcharding land of Amygdalus persica L.-cabbage> the orcharding land of Malus domestica-Zea mays> the farmland of Zea mays-Glycine max. Taking farmland as control, the soil ecological benefits index(SEBI) has increased more than 300% in the original secondary forest(except the shrub secondary forest) which were protected by the "China Natural Forest Conservation Program", but the index has only increased 62.98%-138.57%in restored plantation which were implemented by "Conversion of Cropland to Forest" correspondingly. The SEBI in restored plantation from 1998 are lower than that of in the original secondary forest, even lower than the orcharding land of Malus domestica-forage grass(153.36%).Comprehensive analysis of different land use types and vegetation restoration types of soil environmental factors, soil physical properties, chemical properties and biological activity of each index, land use patterns, vegetation restoration types and recovery time on each factor indicators consistent with the impact on soil ecological benefits. Further analysis showed that:i) Soil in the original secondary forest has the best ecological benefits, so we should strengthen to protect it. ii) During the process of the ecological project about "Conversion of Cropland to Forest", the lack of appropriate supporting management has become the major factor that limmted to improve soil ecological benefits, iii) Among the different vegetation restoration types, the soil ecological benefits in coniferous forest is better than that in broadleaf foret(SEBI in the restored foest of Alangium chinense (Lour.)Harms and Pinus tabulaeformis Carr. were higher than that in the restored foest of Robinia pseudoacacia L), and the the soil ecological benefits in indigenous tree species is better than that in introduced species (SEBI in the restored foest of Cupressus chengiana and Pinus tabulaeformis Carr. were higher than that in the restored foest of Cerasus pseudocerasu). So during vegetation restoration in extreme difficult sites, we shloud match site with trees and choose the indigenous tree species, iv) the soil ecological benefits in the orcharding land of Malus domestica-forage grass is better than that in which were implemented by "Conversion of Cropland to Forest" from 1998, we colud popularize the model for ecological restoration. After that, we can build the stable structures including "Tree-shrub-grass", and develop the agro-forestry models, to...