Analysis And Evaluation On Degraded Ecosystem Ecological Characterizes Of Vegetation Restoration Process In The Hill Areas Of The Taihang Mountains

Restoration ecology is one of the new branches in ecology, and one of issues on which many ecologists focus. Restoration and reconstruction of degraded ecosystems have become one of the major subjects of modern ecology. The hilly area in Taihang mountains is an ecotone between the plain vegetation and the mountainous vegetation. As a result of the over-exploitation to vegetation for a long time, ecosystems in the research areas have degraded seriously, which are characterized by natural vegetation with lower coverage ,lower height, even bare land in some parts, and mosaic with different types of artificial vegetations. The ecological protection functions of the vegetations have been declined. Forest ecosystems play an important role for improving and stabilizing agriculture environment in hill areas of Taihang mountains. For this reasons, this dissertation deals mainly with studies on the natural restoration process and their mechanism of degraded forests in order to find out the limit factors of vegetation restoration and promote the natural restoration and forest sustainable development.The ecological mechanisms and ways for vegetation restoration in the hilly areas of Taihang mountains have been analyzed in this study. The degradation of studied ecosystem is mostly caused by disturbance and climatic change. Based on the methods of classifying restoration stages, Starting from analyze soil physical—chemical properties, vegetation and succession and much previous research, The physical ,chemical and biologic characteristics of main communities in hilly areas of Taihang mountains are investigated . The ecological and environmental feature during vegetation succession has been revealed. The succession models of communities have been set up. The succession times of different communities have been put forward by using the method of modeling for vegetation restoration. The evaluating index structure of vegetation succession period have been established. Which are also well-assessment to vegetation restoration.Major conclusion are summarized as follows:1) The present findings suggested that nature and human activity factors would lead to degraded vegetation for studied ecosystem. The degradation of vegetation is mostly caused by human disturbance and destruction. The lower air moisture and higher air temperature is climatic feature in studied areas. In the future, the climate will be more worm and dry. The ET₀ would be progressive increase. Analysis of climatic functional spectrum indicates that changes temperature and precipitation among years present the distinct periodic fluctuation, of which the former changes with 6a, 3.5a periods and the later changes with 8.5a, 4. 3a periods.2) With the development of vegetation restoration, different restoration stages result in different soil bulk density and such as in order as follows: herbs stage>trees stage>shrub stage. The soil bulk density between shrub stage and trees stage are no significantly different. The capillary moisture capacity and porosity of soil was the lowest in bare land, and the soil bulk density is reversed, soil nature moisture becomes lower in the order from the trees stage, herbs stage, shrub stage and bare land. With progressive vegetation succession, the gravel content decreased; while the indicators increase gradually. The content of clay grain is significantly positive with the soil organic matter and total nitrogen and available nitrogen contents of soil.3) The effect of lowering air temperature and increasing air humidity of vegetation increased with vegetation succession. Daily changes of air temperature in every restoration community stage presented a anisomerous curve of single apex. The air temperature and their fluctuation declined with the development of the community. That showed the effect of adjusting air temperature was better and better. Daily changes of air relative humidity in every restoration community stage had anomalous change presenting "U", which was contrary related to daily changes of air temperature change.4) Nitrogen concentration in green leaves varied widely among species from 1.568% to 5.011% and from 0.82% to 3.89% in senescing leaves. A significant correlation was found between N concentrations in leaves and soil organic matter ,soil moisture. N concentration in green leaves (Ng) and N concentration in senecing leaves (Ns) increased with increasing soil organic matter, total soil N and soil moisture. NRE in these species ranged from 17.4% to 50.1%, with an average of 28.8%, depending upon the species and the life-form. The results show that most of species examined in this study can be categorized as incomplete N resorption plants. The pattern of NRE in different life-forms followed the order of herbs>shrubs>trees. NRE was positively related to soil organic matter, total soil N and soil moisture, meaning that the higher soil organic matter was due to low plants NRE.5) The species numbers and richness had significant increased with vegetation succession, some species diversity indices, such as H', D₁ and PIE had a significantly positive correlation with moisture and thickness of soil, others diversity indices H' and D₁ have positively correlation with soil organic matter, available N, available P. The biomass of shrubs and trees had a significantly correlated with H'. There are no relation between H' and biomass of herbs. The vegetation restoration period was positively correlated with species diversity indices Jsw and H', but not PIE, D₁ and D₂. The species numbers increased by six averagely during 10 years of vegetation restoration. H' had significantly positive correlation with coverage and height of shrubs. There was a clear negative correlation between species richness indices and height and coverage of herbs, and no significant correlation with H'. 6) Biomass is significant increase with the succession stages. Which is relationship of power function. The biomass of the Quercus variabilis was the highest, whilst the Platycladus orientalis was the lowest, and the Robinia pseudoacacia was in the middle. The roots biomass of trees community was lower than that of stem. The ground biomass of the shrubs community was higher than that of underground, the biomass ratio between ground and underground ranged from 2.3 to 3.82. The biomass of Artemisia princeps was the highest, and whilst the Pennisetum flaccidum was lowest.7) The litterfall amount of trees community is significant more than that of shrubs. The quantity dynamical of litterfall is obviously along with the seasonal variation, The sequence is that: autumn >spring>winter. The water content of litterfall was close relationship with vegetation restoration stages. Water retention rate of Robinia pseudoacacia is the highest. Water absorption rate of Quercus variabilis in 20 years old is the lowest. Litter decomposition rate of Robinia pseudoacacia is fastest, which will just take 8.83years to almost decompose litterfall. Loweast by 40 years old Quercus variabilis, 26.63 years. Litter decomposition rate of 30 years old Quercus variabilis in same community is the fastest. Litter decomposition rate of shrubs has faster than other community. It will take 9.66 years to almost decompose litterfall by Ziziphus jujube, and 12.35 years by Vitex negundo.8) total carbon storage of ecosystem and soil increased with progressive succession. It increased 4.5times form herbs stage to trees stage, the ratios of soil carbon storage / ecosystem carbon storage show decreased. And the ratios of carbon storage in vegetation increased gradually by progressive succession. So that, The vegetation played an important role in degraded ecosystem restoration process.9) Vegetation successional processes show the trend form herbs to shrubs and trees. With the progressive succession, the community would turn from annual grass species dominance into a multiple-community dominated perennial herbaceous genus , semi-shrubs, shrubs. When the herbs successes 10 years, Ziziphus jujube and Vitex negundo formated mono-dominant community, the community of Quercus variabilis dominance is climax community. Robinia pseudoacacia under natural succession will been taken by Quercus variabilis community. Robinia pseudoacacia might be a dis—climax community under the human disturbance. Platycladus orientalis successes slowly. But the community would turn from mono-dominant coniferous forests into a broadleaf/coniferous mixed stand.10)The successive times will take almost 80 years at fastest speed form bare land to climax-community.but it take about 40 years to reach the sustainable community. The restoration time is about 7-8 years for herbs, and 12-14 years for shrubs. Restoration time of soil is slower than that of community. Physical character index of soil recovered the slowest, biomass restoration take the longest. Quercus variabilis community will reach the climax-community after 60-80 years. The slope effect on restoration process obviously. The restoration time in shade slope is faster than that in sunny slope. And restoration time in steep slope is faster than that in gentle slope. The restoration time is 60-73 years in Robinia pseudoacacia, 95-110 years in Platycladus orientalis, which is longest.11) As a results of cluster analysis, The vegetation in the researching areas can be classified into 4 types, including initial restoration stage (IRS) , progressive restoration stage (PRS), middle restoration stage(MRS), stable restoration stage(SRS). According to different restoration, the index , valued degraded ecosystem ,which included environment , micro-climate , community structure and soil had been setup. The degraded ecosystem at hilly areas in Taihang mountain was assessed by using method of analytic hierarchy process and eco-restoration indices.