Study On The Soil Features And The Bstacles Of Continuous Planting Of Several Typical Artificial Forests In Shannxi Qinling And The Northern Wei River Forests Area

As pure species of composition is simple, the characteristics of bio-ecological is single, the using or absorption material is selective, and the special effects on the environment will lead to its long-term growth or continuous planting, there since the soil depleted, such as self-barren, self-poison, dry, acidification, salinization,and so on, it is a serious impact on the stability and sustainable forest development. This thesis studied the Shaanxi Qinling mountains (chinese pine, larch, sharptooth oak and catalpa) and the Weibei Plateau in Shaanxi (chinese pine, black locust and oriental arborvitae) pure and mixed for the object. Measured the soil prosperities of physical, chemical and biological, to evaluate the soil dynamic trends under the pure or mixed forests; used leaves and seeds extractions to deal with seed germination, to test the existence of self-poison effect; designed the pots experiment of simulation the pure and mixed forests by cultivation, to analysis the species relationship between the soil of different coniferous-broad forests. The main conclusions are as follows:(1)By measuring the soil prosperities of physical, chemical and biological , the results shows: the physical properties of the soil has improved, total nitrogen, ammonium nitrogen, alkaline-hydrolytic nitrogen, total phosphorus, organic matter, and the number of soil microbes are the coniferous-broad leaved mixed forests > coniferous forest> natural grassland in the Qinling Mountains forest area, the soil nutrients of the mixed forest of sharptooth oak and chinese pine are the highest. The coniferous forests soil are better than natural grassland, but have a certain risk of degradation compared to coniferous-broad forests. The soil physical prosperities have improved also in the northern Wei River area, the total nitrogen, ammonium nitrogen, alkaline-hydrolytic nitrogen, organic matter of natural grassland are higher than artificial forests, that the pure forests have an obvious risk of soil degradation.(2)By using extraction of the leaves and seeds to germinate seeds, the test results showed that: the germination rates are basically the seed extractions catalpa (17.01)> sharptooth oak (9.54)> chinese pine(9.02). The integrated soil polarization of pure forests in the northern Wei River forest area is oriental arborvitae (6.16)>black lucst(2.85)>chinese pine (2.43). The pure forests of soil physical, chemical and biological indicators of its contribution rates are 11.22～23.44%,8.82～38.13% and 50.65～72.86% respectively in Qinling forest areas; and 15.10～28.41%,15.64～41.47% and 31.78～69.26% respectively in the northern Wei River forest area, so strengthen soil the biological prosperities will help to improve forests soil.