Study On The Stability Of Plantation For Wind Protection And Sand Fixation In Horqin Sandy Land

Horqin Sandy is one of main sand in China. Due to soil erosion and desertification continues to expand, ecological environment further deterioration. In resent years, the sand-fixing and ecological restoration is the main object of afforestation in this region.There are many wind protection and sand fixations such as Poplar, Prunus armeniaca,Caragana microphylla, Shiny-leaved yellowhorn and Hedysarum Laeve, and so on. The stability of plantation become the primary problem. The stability of Caragana microphylla, Shiny-leaved yellowhorn and Hedysarum Laeve for wind protection and sand fixation in Horqin sandy land has been studied. The study includes the statistical analysis of grain size of surface soil, the changes of population structure, the analysis of the process of species invasion and community structure changes in different developmental stages, the species diversity of community in different age class, the change of site quality and the comprehensive evaluation of the population stability to provide a theoretical basis for rehabilitation and reconstruction in this area. The main conclusions can be draw from paper as follows:Based on the comprehensive analysis of grain size of surface soil of three different artificial sand fixations, the differentiation of grain size of surface soil in three different populations was obvious and showed some regular. The proportion of sand(1-0.05mm) decreased with the increase of age class of Caragana microphylla and Shiny-leaved yellowhorn. The proportion of coarse sand (1-0.25mm) increased gradually and the fine sand (0.25-0.05mm)declined. The Hedysarum Laeve also showed that law follow the middle slope, the upper slope and the below slope.The semi-fixed sand(Caragana microphylla and Shiny-leaved yellowhorn)were the most coarse and good separation. Semi-mobile sand (Hedysarum Laeve)showed the wind erosion and desertification stage.According to the inference of grain size of soil on the soil erosion by wind, the relative value of sensitive to grain size accounted for easily erodible segment of grain size of surface soil showed:Caragana microphylla was as follow:nature sand>6a>14a>20a>27a. Shiny-leaved yellowhorn was as follow:nature sand>3a>18a>31a>44a. Hedysarum Laeve was as follow:nature sand> the middle slope>the upper slope>the below slope. To some extent that the dust sources mainly come from the surface soil of natural sand and younger age-class forest lack of plantations.The artificial sand fixation of Caragana microphylla belonged to stable population in certain developmental stage. It had a certain ability to update.With the age increase, the number of seedling growth equaled to the number of adult deaths. To some extent it can reflect the stability of population. However, as time goes further, the number of seedlings began to reduce;population structure was recession-type, species diversity decreased. The population structure began recession when 27a due to moisture,nutrients and other conditions decreased. In short, the stability of 20-year Caragana microphylla was the best.With the growth of, the number of seedlings decreased, the number of large diameter increased. It showed that Shiny-leaved yellowhorn itself less able to reproduce without artificial reproduction, due to temperature,water quality and other site conditions. The population of Shiny-leaved yellowhorn began recession. The majority of individuals have passed the reproductive age, population size tends to reduce.But the stability of Shiny-leaved yellowhorn was better, and it can better fit the local environment. The stability of 44a Shiny-leaved yellowhorn was the best.Hedysarum Laeve is one of the main species of wind protection and sand fixations in Horqin sandy, it has strong advantage at quality and productivity and plays a significant role as an important fixing species. By studies of Hedysarum Laeve in different habitats showed that: the stability of Hedysarum Laeve wasn't influence by soil moisture, nutrients and other effects. The stability of Hedysarum Laeve on the below slope was better. The population of Hedysarum Laeve was growth. There were many young individuals and the population continued to grow. The stability increased gradually. In conclusion, the stability of Hedysarum Laeve on the below slope was the best.Finally, the most stable populations of three species compared, results showed that the stability of 20-year Caragana microphylla was the best.44a Shiny-leaved yellowhorn second, and the stability of Hedysarum Laeve on the below slope was relatively poor. This shows that the stability of Caragana microphylla was the best in three major artificial fixation in Horqin sandy. Caragana microphylla can adapt to natural conditions in the region. It can play a role in sand fixing while the structure and function achieve a relatively stable state. The stability of Shiny-leaved yellowhorn increased with the growth, but less able to update. Hedysarum Laeve was adapt to the semi-mobile sand and had strong drought tolerance. It play a strong role to restorate the ecological environment, and was a good species to manual control sand.Base on the study of stability of three wind protection and sand fixation in Horqin Sandy, the stable fixation forest communities should have the following conditions:(1)suited to local environmental conditions,(2)have a certain resistance to outside interference and restorative,(3)with normal development and self-renewal capacity,(4)have population structure of more perfect.