Study On Techniques Of Transformation And Renovation Of Farmland Shelter Belt In Plain Area Of Yellow River

This study choosed the ways of orientation observation and investigation and especially studied forest renewal age, renewal way and technology, tree choose and collocation, allocation and structure of network of forest, build technology of new network of forest, beneficial evaluation of transformation and so on, which made a thorough and system research, to sum up transformation and renovation techniques of farmland network of forest in plain area of Yellow River of our country. Study results are mainly as follows:1. Research indicates that protection mature age of the paulownia and poplar is 8 years and 6 years, mature age of quantity is, respectively, 25 years and 20 years, mature age of technics have very big diversity in differnet field, mature age of economy is in 13 and in 12 respectively. The best renew age of poplar and paulownia is 10～12 years and 10～13 years.2. Research is indicated, total transformation and renovation of farmland shelter belt is tidy, shelter forest growth is faster, but founction and efficiency of them decreased markly; As to half transformation and renovation of farmland shelter belt, founction and efficiency of shelter actually did not reduced, it also takes up small land and bring the merit which continuly produced protection fountion of shelter, but sometimes appearance of forest is out of order. Nursing and intermediate cutting having improved forest belt structure, strengthens wind-proof efficacy, average wind-proof efficacy of 1-20H of intermediate cuttings forest is 26.8%, which improving 5.3 percentage point compara to un-cuting forest, moreover, growth of reserving wood having promoted, wood cumulation of un-cutting forest increase to 19.33 m~3 from 9.61 m~3, and wood cumulation of intermediate cuttings forest increases to 19.91 m~3 from 6.19 m~3 within the same time, increasing of intermediate cuttings forest is for 2.2 times of intermediate cuttings forest but within identical time. Besides, fertilization significantly improving growth amounts of tree, and wood accumulation which applied fertilizer of 3-year-old and 6-year-old shelter increased 47.2% and 36.8% respectively.3. Study result indicates that when plant at two flanks of the road, ditch and canal, the best varieties of trees should be Zhong Lin-46 poplar, I-69 poplar, this two types of trees grow fast, the tree body is lofty, both can strengthen shelter belt protecting function, and can provide good quality wood; On the middle slope of a ditch betterly using Saliz matsudana (J-172) and I-69 poplar, they show the characteristic of fast growth and perfectly protecting the slope; On the upper slope of the ditch betterly takes I-69 poplar and paulownia as regards; On a dike and dam betterly chooses locust and dwarf elm, this two trees are suit to arid and barren gorund and show stronger adaptability.4. Research shows that the forest belt adopts 2～4 line number, and sparse permeation degree is 0.25-0.35, which is perfectly. It takes up small land and has little bad effection on corps, moerover, can strengthenwind-proof efficacy, per plant interval of forest belt with 3 m×4 m are suitable. Besides, when the I-69 poplar forest belt interval increase, wind-proof efficacy of the forest belt lee side assumes parabola change, the maximum wind-proof distance of function is 22 H, weak wind area is within 14 H. Height of forest belt trees are 15 m, now that 200～350 m be suitable for the interval of forest belt.5. Research indicate that net lattice area change of farmland network of forest affects the wind speed, the temperature and humidity. Follow net lattice area to enhance, whose total average wind-proof efficacy reduces, the absolute value of reducing value of the average temperature cuts down. In addition, average wind-proof efficacy reaches 18.7% 3 years after forest belt renewal at 1-20H area of forest belt, actually have the wind-proof function; It play obvious adjustment role to the temperature and humidity, also restrain the occurrence of dry and hot wind effectively, restore the entirety function of the network of forest.6. Fertilizing, watering and pruning has the fairly good effect for growth and forming of the network of forest, triple union effect is nicer. The pruning height is about 3.0 m beneath the first branch at child forest period, if the height it too low, wood quality and accumulation do not increase fast, contrarily wind-proof efficacy is not perfect, especially to narrow forest belt, pruning amount should be suitable.7. Benefits evaluation of transformation and renovation of the network of forest shows that ecology benefits, social benefits and economic returns are notable. Forest belt structure improvement has strengthened the protection function, renewal of varietys of tree having improved adaptability of the network of forest, has optimized age structure of stand; The indirect increasing benefits of transformation and renovation is 1,234.6 thousand yuan, the direct economic benefits increases is 595,2 thousand yuans, moreover, current ecnomic benefits is 499.1 thousand yuan by compound interest calculation concern cost of investment, rate of beneficial returns to costs is 3.67.