Research On The Ecological Cultivation Mechanism Of Eucalyptus Plantation In Southeast Of Fujian Province

Eucalyptus (Eucalyptus Spp) is one of the world's three fast growing timber species widely introduced and used to afforestation since the 20th century 80's in south, southwest, southeast of Fujian province. The research range of this paper is the main cultivated areas of eucalyptus in Zhangzhou, Fujian, Quanzhou, Putian and Fuzhou, Ningde and the research objective are eucalyptus clone species forest such as Eucalyptus granddis×E. uophylla,Eucalyptus urophylla×E. grandis, Eucalyptus grandis and Eucalyptus urophylla. The problems of the Eucalyptus plantation in these areas are low nutrient use, soil degradation, vegetation diversity reducing and other ecological issues. By researching the forest management, forest structure adjustments, tending and thinning, soil nutrients and nutrient compensation control mechanism, such as mixed planting of Eucalyptus plantations in terms of growth, vegetation diversity, soil fertility and analyzing the efficiency of economics, ecology and sustainability, this research constructed the ecological cultivation optimization model of eucalyptus plantation in Fujian Province and put forward the key technology of sustainable management, aiming at overcoming the contradiction between fast growing and soil fertility consumption, improving ecological environment, maintaining soil fertility. The purpose of the study was supplying scientific basis and technical support for sustainable management of eucalyptus plantations in southeast Fujian and achieving the best economic, ecological and social benefits. The main study results are as follows:1. There was significant ecological effects difference between different way of forest management and forest structure adjustment, such as forest clearing, soil preparation, planting density, tending fertilization, thinning and so on.(1) The different woodland clearance way showed that the forest productivity decreased after burning. The tree height, volume, accumulation decreased significantly of three years old forest. The forests were disturbed by human after burning. The growing of understory vegetation was effected, leading to the reduction of species diversity, deterioration of soil property and eventually leading to forest productivity decline. Compared with the burning, the average height, volume, stock volume, vegetation types,coverage, soil density in no burning forest increased by 14.63%,22.16%,56.38%,22.16%,56.38% and 4.92%. Capillary water, field capacity, capillary porosity, non-capillary porosity, total porosity and aeration decreased 9.02%,5.53%,4.52%,25.45%,9.62% and 25.00% respectively. Soil organic matter, total N, total P, hydrolysis of N, the effective P, available K decreased by 14.32%,27.45%,6.44%,33.55%,16.48% and 27.83% respectively.(2) Results showed that the interaction of soil preparation size and plantation density had no significant effect on forest growth and wind resistance. The plantation density had significant effect on forest growth and wind resistance. Compared with soil preparation size, plantation density had more significant effect on oil fertility, understory vegetation and water conservation. Taking all factors into consideration, such as forest growth, wind resistance, soil fertility, understory vegetation diversity, water conservation and investment cost, eucalyptus plantation in Fujian mountain area may not dig large hole which will increase invest cost and decrease wind resistance. So the size of soil preparation could mainly on small specifications, i.e.30 cm×20 cm×20 cm. And plantation density of 1110-1320 plants per hectare was suitable, which will help to improve output, improve wind resistance and maintain land capability.(3) Growth of eucalyptus forest after weeding, cultivation and fertilizing was significantly higher than those without tending. Weeding and fertilizing had significant effect on growth of eucalyptus forest. After fertilizing, soil fertility could be improved and provide sufficient nutrients to understory vegetation. The weeding, covered, fertilization and other measures to foster the growth of eucalyptus forest was significantly higher than those without the application of plots fertilization management, forest cover reclamation, fertilization and other measures to foster a greater impact on the growth of Eucalyptus. The manure management, soil fertility improvement can provide sufficient nutrients to understory vegetation, improving their diversity. Proper cultivation could help increase soil water content and porosity, with the result of soil volume weight reduction. Furthermore, the soil is more aerated and permeable, improving forest growth.2. The key technology measures for the eco-training were forest resource management and soil nutrient quality control (1) Study of nutritional characteristics of Eucalyptus and nutrient cycling showed that N,K and Ca were in hare demand and accumulation ability of Mn and Fe was strong. The cycling rate of P was the lowest, about from 11.33 to 14.70 percent, next to K. Microelement of Mn and Fe had the lowest cycling rate, about 15 percent. So, application of N, P, K, Ca was indispensable technical measures for long-term management of eucalypt woodland. Combining application of Mn,Z,Fe could promote ecosystem nutrient cycling, and stable yield of forest.(2) Study of nutrient accumulation and forest nutrient cycling rate showed that the distribution proportion of nutrition elements was leaf and bark in sequence. Leaves and barks played an important role for nutrition balance and maintenance of site fertility. Most of nutrient absorbing were in the tree body and only few of them return to forest site by litter, the ratio of which is about from 24.16% to 26.58%. When cutting and using, the best method was "whole tree application", which was good for the forest ecosystem nutrient cycling.3. Better economic and ecological benefits could be achieved by thinning and controlling reasonable stand density.(1) The density of 1200 plants per hectare for long period plantation forest could achieve best ecological benefits, demonstrating in vegetation diversity, soil property, water conservation. The species richness, evenness and diversity indices of Eucalyptus grandis were decreasing with the density increasing. So rational density is suitable for the growth of Eucalyptus and could promote the stability of eco-system.(2) Soil nutrient content was increasing with the density increasing, reaching the peak at the density of 1200 plants per hectare. Soil nutrient content was declining at the density of 1415 plants per hectare.(3) The results showed that the total water capacity of Eucalyptus forest aboveground was from 9.32 to 14.17 ton per hectare, with the most ratio of canopy class and the least ratio of litter. Total water capacity was increasing with the density increasing, reaching the highest value at the density of 1200 plants per hectare and lowest at the density of 600 plants per hectare.4. Mixed forest was one of the most effective bio-ecological cultivation measures.(1) Mass growth of mixed forest was higher than single forest. The fir- eucalyptus mixed with star shape at the ratio of 8 to 2 is advantageous for both the mass of fir and eucalyptus and the maintenance soil fertility, suitable for medium or long term management. The eucalyptus-acacia is suitable for medium or short term management. Results showed that eucalyptus- acacia mixed with star shape and the ratio of acacia between 30% and 50% is suitable for growth of eucalyptus and acacia. If mixed in line, the ratio of 2 line eucalyptus to 3 line acacia is suitable.(2) Mixed forest has obvious advantage of maintenance soil fertility. The eucalyptus- acacia mixed forest with more litter, more complex composition and higher nutrient content, coupled with the interaction of the roots, the soil property and fertility was significantly improved. Besides, the special sub-storied structure promoted the vegetation growth of under forest and improved the species diversity.(3) According to the study results and productive practice, fir-eucalyptus mixed forest and medium or long term rotation management with proper density and plowing, fertilizing could achieve large timber, Eucalyptus- acacia mixed forest and medium or short term rotation management could achieve the forest of plank stuff and pulpwood.(4) Because of different tree age, the fir-eucalyptus mixed forest could be only suitable for medium or long term rotation management. So the eucalyptus breed of small growth stress and strong corrosion is suitable for mixing with fir. As lower growth speed of acacia, the mass growth of mixed forest is lower than eucalyptus forest in short term so the cutting period could extend to 8 to 12 years. Not only the mass growth could be improved but also the soil fertility be promoted and huge economic, ecological and social benefits achieved.