Evolution Characteristics Of Soil Organic Carbon In Different Generation Of Continuous Eucalyptus Plantations

Eucalyptus because of its strong adaptability, extensive applications and considerable economic benefits, was large area developed in southern China, especially in Guangxi. This paper focuses on large-scale planting of eucalyptus may be brought the "degradation of Soil Fertility Quality" problems, and test for the core component of soil fertility—soil organic carbon, studied on organic carbon and its component evolution. Adapting of field investigation Space-time substitution and laboratory analysis, to discuss evolution characteristics of soil nutrients and organic carbon and its components in four different generations of continuous Eucalyptus plantation and Masson pine(control forest),aim to provide a reference basis for correct evaluation soil quality of eucalyptus plantation multi-generational.The result is following:1、Evolution characteristics of soil nutrients and pH in different successive generations of Eucalyptus Plantation:As the eucalyptus plantations generations increases was decreased, Soil organic matter、Total nitrogen and Available nitrogen was decreased first after increased then decreased; Soil phosphorus was decreased;Available phosphorus was increased first then decreased;Rapid available K was increased first then decreased; After planting eucalyptus, soil pH increased slightly, but it was still acidity.Compared with Pinus massoniana, excepting Available phosphorus content reduced, the other nutrients were increased, show that Eucalyptus plantation instead of Masson pine forestin, soil nutrients were improved, did not cause soil fertility declined.2、Evolution characteristics of soil total organic carbon content in different successive gen rations of Eucalyptus Plantation:soil total organic carbon content as generations increases was decreased first after increased then decreased, and the highest content in the three generation, the maximum organic carbon content was appeared in the July or September and the lowest in the November or March; Compared with Pinus massoniana,except fourth-generations eucalyptus slightly lower,the other has increased, but not significant differences, and the maximum organic carbon content was appeared in the March and the lowest in the September. Show that Eucalyptus plantation instead of Masson pine was increased soil organic carbon content, and enhanced the capacity of soil carbon sequestration3、Different successive generations of Eucalyptus plantation soil readily oxidation carbon content and evolution characteristics of it:Soil readily oxidation carbon content of eucalyptus plantations as generations increases was showed that G3>G1>G4>G2;Compar-ed with Pinus massoniana, excepting third-generations eucalyptus plantations, it was not significant differences; Soil soil readily oxidation carbon content has not significant changed seasonal variation.4、Evolution characteristics of soil stable carbon content in different successive generations of Eucalyptus Plantation:As eucalyptus plantations generations increases, soil stable carbon content was decreased first after increased then decreased,but compared with Pinus massoniana, it was increased, and the most significant increased in the third generations of eucalyptus forest soil; Soil carbon content of steady state has not significant changed seasonal variation. It was showed that Eucalyptus plantation instead of Pinus massoniana,the forest soil available nutrient capacity increased and reinforced soil structure stability.5、Evolution characteristics in different successive generations of Eucalyptus plantation soil organic carbon oxidation stability:Instead of Pinus massoniana, the organic carbon oxidation stability index was increase, but as eucalyptus plantations generations increases, it was changed smaller and showed that G2>Gl>G3>G4>G0.Ther-e were indicated that Eucalyptus plantation instead of Pinus massoniana, the resistant decomposition ability of soil organic carbon was increased.6、Different successive generations of Eucalyptus plantation soil humus acid carbon content and Evolution characteristics of it:As the eucalyptus plantations generations increases was decreased, the humus carbon%HA-C and humin carbon were decreased first after increased then decreased, and the FA-C was increased first then decreased; Instead of Pinus massoniana, the HA/FA of eucalyptus plantations was decreased, and indicated that the soil humus degree was tend to decrease and the quality of humus to be weak. In different forest soil, the minimum HA-C content was appeared in January and the maximum in a slightly different month, while the HA-C maximum humin carbon content was appeared in January or November and the lowest in September.