| Due to the sharp increase of population and the rapid development of social economy, the area and accumulation of forest are gradually reduced.In our country, because of the implementation of the natural forest protection project, the contradiction between the supply and demand of wood is more prominent. Therefore, the development of artificial forest has become one of the main means to solve the contradiction between supply and demand of wood. But the development of artificial forest also brings a series of problems. How to prevent the decline of artificial forest land and maintain the productivity of artificial forest land has become an urgent problem to be solved. Giant in Eucalyptus grandis) is (Eucalyptus) in an excellent and fast growing timber tree from Myrtaceae (Myraceae) eucalyptus, China 60 years from the last century began the introduction of Eucalyptus grandis, successfully introduced later in the promotion of large areas of the country. At present, Sichuan Province has 27.74 million hectares of Eucalyptus grandis plantation, the planting of Eucalyptus grandis as foresters brought considerable economic benefits, driven by the region’s forestry industry development. However, with the continuous planting of Eucalyptus, the development area of Eucalyptus Plantation appeared the decline of forest land productivity, the change of soil physical and chemical properties and so on. Based on this, in order to explore the continuous planting of Eucalyptus grandis on trees and soil physicochemical properties, for the sustainable development of Eucalyptus grandis plantation provide reference, this study in Eucalyptus grandis plantations in the Qingshen County in Sichuan Province as the research object, select site conditions are basically consistent with the three generations (Dailin, Ⅱ generation and Dailin) 5 years old in Eucalyptus grandis plantation, through field investigation and laboratory experiments to study the effects of continuous cropping on tree height, DBH and volume growth and soil physical and chemical properties. The main results are as follows:1 With the continuous planting generation increasing, DBH, tree height and total volume increment and average growth was significantly reduced (p<0.01). The total DBH increment performance Ⅰ was (14.06 cm)>Ⅱ system (11.30 cm)> Ⅲ was 10.72 cm, and the average growth quantity for Ⅰ was (2.81 cm)> Ⅱ system (2.26 cm)> Ⅲ was 2.14 cm). Total tree height growth performance was 1 (13.50 m)> Ⅱ system (11.51 m)> Ⅲ was 11.07 m, and the average growth quantity was 1 (2)> Ⅱ system (2.30m)> Ⅲ was 2.21M. Individual timber product total growth performance was Ⅰ (0.0971 m3)> Ⅱ system (0.0571 m3) and> Ⅲ rotation (0.0501 m3), and the average growth quantity was Ⅰ (0.019 m3)> Ⅱ system (0.011 m3)> Ⅲ rotation (0.010 m3);2 With the continuous planting generation increased, soil bulk density showed a gradually increasing trend, but the difference was not significant; soil maximum water holding capacity and field moisture capacity with the increase of significant variation; soil porosity decreased with the increase of showed significantly reduced trend (P<0.05);3 With the continuous planting generation increased, soil organic matter, pH, total nitrogen, water soluble nitrogen, total phosphorus, available phosphorus, total potassium, available potassium showed decreased significantly, overall I forest and secondary forest between larger decline, second generation and third generation between decline smaller.4 Soil pH, organic matter, total nitrogen, water soluble nitrogen, total phosphorus, available phosphorus, total potassium, available potassium, field to content and volume growth was significant or extremely significant positive correlation (r=0.027-0.959**); organic matter and pH, total nitrogen, available phosphorus, available potassium was extremely significant positive correlation (r=0.810**～ 0.910**), and water soluble nitrogen, total phosphorus, total potassium is positively significant positive correlation r=0.600*～0.665*, and field to content had a positive correlation (r=0.065).In summary, the growth of Eucalyptus plantations is decreased, and the physical and chemical properties of soil are important. In the continuous planting of Eucalyptus grandis in the process, to take timely measures such as fertilization, irrigation and thinning, in order to improve the productivity of forest land. |
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