| Under the environment of rapid social and economic development,people have a larger demand for wood,and long-term uncontrolled deforestation led to declining natural resources.Plantations occupy an important role in forest ecosystems,where artificial forests accouted for a large proportion.Due to the simple pursuit of long-term economic benefit people of the forest,ignoring the huge forest ecological and social benefits,plus long-irrational mode of operation,resulting in many ecological problems such as soil degradation,environmental degradation,declining productivity stand and other issues.To alleviate these problems,improve forest economic,social and ecological benefits,to achieve sustainable development of forest land and forest,creating mixed forest has become a long-term production and practice by domestic and international forestry workers.Cunninghamia lanceolata was large-scale planting as one of China's fast-growing species and an important afforestation species in the south.The drawbacks was increasingly prominent about continuously planting Cunninghamia lanceolata pure plantation,and how mitigation this problem become a research focus,one way was to create a suitable mode which is formed by Cunninghamia lanceolata and others species.Aleurites Montana is one of fast-growing species as biomass energy.Currently,there is few quantitative research about mixed forest of Cunninghamia lanceolata and Aleurites Montana.So,to a certain extent studying on its mixed forest can reveal growth regularity,provide better cultivation methods and the scientific basis for the southern region of China' mixed forest of Cunninghamia lanceolata and Aleurites Montana.3-5 year old mixed forest of Cunninghamia lanceolata and Aleurites Montana as the research object,measured between different species of various forest stand age intraspecific competition empHasized the physical properties of soil,soil characteristics and soil nutrient content activity changes.Research has made some progress in the following areas:1?The survey showed:the mixed forest of Cunninghamia lanceolata and Aleurites Montana can form compound storied forest structure with more reasonable and uniform forest layer distribution.The different age of the mixed forest of Cunninghamia lanceolata increased the tree height and DBH in different degree.The average DBH of 3-5 years old mixed forest are 19.4%,25.3%,30.2%higher than the Cunninghamia lanceolata's,and the average tree height are 10.7%,18.4%,11.8%higher.2?The Cunninghamia lanceolata's intraspecific and interspecific competition are measured,obtaining;D(mixed forest with fir Cunninghamia lanceolata as object)>D(pure Cunninghamia lanceolata forest)>D(Aleurites Montana),indicating that the fir in mixed forest grow better than those in pure forest;when taking the fir as the object,the intensity of intraspecific and interspecific competition of Aleurites Montana mixed forest and pure fir forest decreases with the DBH increasing.The intensity of competition in the mixed forest are higher than pure forest.Comparing the two forest types 3-5 years old,with age increasing,the intraspecific competition decreases in the short term,while interspecific competition first increased and then decreased,the biggest are 4 years old mixed forest.3?The mixed forest of Cunninghamia lanceolata and Aleurites Montana improves soil organic matter obviously.Compared with pure Cunninghamia lanceolata forest,the soil bulk density of mixed forest of Cunninghamia lanceolata and Aleurites Montana of 0?10cm and 10?20cm decreased,capillary porosity,non capillary porosity and total porosity increased in different degree,In contrast with bulk density variation trend generally;with the increase in age,physical indexes of pure forest show little change in the short term,the mixed bulk density,capillary porosity,non capillary porosity and total porosity obviously changed;Under the impact of other broad-leaved tree species' physiological need in the mixed forest(such as liquidambar formosana)and transpiration,its natural water content is higher than the pure forest,and with the increase of the forest age,natural water content of mixed forest increases less,while the law of pure forest is not obvious.4?Mixed forest of Cunninghamia lanceolata and Aleurites Montana can significantly improve the chemical properties of soil.Overall,the soil in mixed and pure forest possess most organic material,total nitrogen(N),hydrolytic nitrogen,total phosphor(P),effective phosphor,total kalium(K),available K on the surface,except individual soil layers,the nutrient content distribute in a clear hierarchy with gradual decrease.As to different forest types,mixed forests with the same age have more organic material,higher pH,total N,total P,available in general than pure one,within different forest stand,the soil parent material,microbes and other factors,organic material,total N,total P,available P increased with stand age,during as short3-5a as period,while PH,full-K,available K,N change in inconsistent ways.5?Mixed forest of Cunninghamia lanceolata and Aleurites Montana increased the enzyme activity in soil.The oil surface has many fine root,high organic matter content and good permeability.So,the content of four kinds of enzyme in the surface layer is the highest,generally reduce with the depth.Compared with different forest types,in addition to individual,the activity of soil urease,invertase,acid phosphatase,catalase in every layer are higher than those of the pure stand.Compared with different stand ages,the trends of sucrase and acid pHospHatase in pure and mixed forests both increased with the age increased.But catalase and urease showed no obvious regularity.6?Correlation analysis indicated that:the soil bulk density and most of the physical indicators are significantly correlated.So pure forest and mixed forest both can take soil as the center to give a reasonable explanation for the trends of other pHysical indexes.Soil organic matter and total N,total P,hydrolytic N,effective P,available K,urease,invertase,acid pgosphatase,catalase showed a significant or extremely significant correlation,showing that the soil organic matter is not only an important source of nutrients,but also as a part of the enzyme storage base.That is enough to reflect that the organic matter is in the center position of the soil quality indicators.The soil enzyme activity and soil nutrient indexes are closely related,so the enzyme activity also could be used as appraisal indictors for the soil fertility. |
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