Study On The Mechanism Of Maintaining Long-term Productivity Of Bamboo Forest

Moso bamboo (Phyllostachys pubescens), which is most widely distributed in South China, has the largest amount and highest economic value among the bamboo species. A set of high-yield cultivation technique of Moso bamboo was built by scientific research and production practice for a long time, which was fast effect, simple operation, and practical method. However, the structure and function of ecosystem of Moso bamboo were destroyed and productivity of site was decline while the higher economic benefits were obtained. Therefore, an important scientific issue was proposed, which was to maintain long-term productivity of Moso bamboo. The main conclusions are as follows:1 The productivity of bamboo was declined by operating time prolonged. And the diameter at breast height may reflect the trend of Moso bamboo productivity.(1) The average diameter at breast height and tree height were declined with the time. 164 sample plots with herb chopping, reclamation measure, and fertilization were investigated which distributed in Yongan County of Fujian Provinecwere, Shunchang County of Fujian Province, Anfu County of Jianxi Province, Anji County of Zhejiang Provice, and Changning County of Sichan Province. Generally, the average DBH and the height of bamboo with the conventional operations increased in a short period. The DBH increased significantly in ten years and reached the maximum 10.95㎝, and the height of bamboo increased significantly in thirteen years and reached the maximum 15.01㎝. However, the DBH and the height of bamboo appeared a decreasing trend with the operation time. The descent range of bamboo DBH reaches extremely significant, but the descent range of bamboo height does not reach significant.Herb chopping. In the management model of herb chopping bamboo forest, the DBH increased significantly within 10 years, and reached the maximum 10.94㎝. Then the average DBH began to descend and reached the value 9.78㎝, extremely significant in 30 years . The height of bamboo increased significantly in 20 years, and reached the maximum 14.58 m, and then the heights of bamboo decreased significantly in 30 years, and reach the value 13.82 m. The average DBH and height of bamboo forest in different plots were influenced differently by measure of herb chopping. The DBH of bamboo with herb chopping within 10 years increased 25.43% compared to no herb chopping in Shunchang County, Fu Jian Province; 13.30% in Yongan County, Fu Jian Province, and 41.89% in Changning County, Sichuan Province. The tree height of bamboo with herb chopping within 10 years increased 21.95% compared to no herb chopping in Shunchang County, Fu Jian Province; 8.30% in Yongan county , Fu Jian Province, and 17.31% in Changning County ,Sichuan Province. The DBH of bamboo forest with herb chopping more than 30 years decreased 5.73% compared to herb chopping within 10 years in Shunchang County, Fu Jian Province; 11.74% in Yongan County, Fu Jian Province, and 13.65% in Changning County, Sichuan Province. The tree height of bamboo forest with herb chopping more than 30 years decreased 1.87% compared to herb chopping within 10 years in Shunchang County, Fu Jian Province; 7.66% in Yongan County, Fu Jian Province, and 3.31% in Changning County, Sichuan Province.Reclamation measure. In the management model of reclamation measure bamboo forest, the DBH and tree height increased significantly within 10 years and reached the maximum 11.32㎝ and 13.88 m. Then the DBH decreased significantly in 30 years, but the height of bamboo decreased insignificantly. The average DBH and height of bamboo forest in different plots were influenced differently by measure of reclamation measure. The DBH of reclamation measure bamboo forest within 10 years increased 40.25% compared to no reclamation measure bamboo forest in Shunchang County, Fu Jian Province; 35.64% in Anfu County, Jiangxi Province. The tree height of reclamation measure bamboo forest within 10 years was increased 32.57% compared to no reclamation measure bamboo forest in Shunchang County, Fu Jian Province; 6.56% in Anfu County, Jiangxi Province. The increased range reaches the extremely significant. However, the DBH and height of bamboo decreased with time. The DBH decreased significantly by 9.95% in Shunchang County, Fu Jian Province and 35.64% in Anfu County, Jiangxi Province. The height of bamboo decreased significantly by 4.68% in Shunchang County and decreased insignificantly 0.38% in Anfu County. Fertilizer application. In the management model of fertilizer application bamboo forest, the DBH and tree height increased significantly in 5 years, and reached the maximum 11.70㎝ and15.90 m. Then the DBH and tree height decreased insignificantly. The DBH of bamboo forest with 10 year fertilizer decreased by 6.24% compared with the DBH of bamboo forest with5 year fertilizer, and the height of bamboo decreased by 3.84%. The decreased range did not reach the significant.(2)The average DBH of Moso bamboo forest is an index which can reflect the productivity degradation of bamboo. The path analysis showed that operating time affect the DBH directly, and the tree height indirectly. Therefore, the index of DBH can reflect the productivity degradation of bamboo, but the index of tree height can't.2 The biological characteristics of bamboo possess fragility. The forest litters is an important part of ecosystem, an important step of material cycling, and a self-fertilization mechanism. First, the litters of bamboo are least among D.barbatus Hsueh et D.Z.Li forest, D.latiflorus Munro forest, and Chinese Fir plantations. The nutrient cycling characteristics were measured in pure bamboo forest, bamboo stand mixed with broadleaves trees and bamboo stand mixed with coniferous trees were studied in YongAn County, FuJian Province. The result showed that the annual uptake is 421.37±42.09 kg·hm-2 in pure bamboo forest, 690.88±65.09 kg·hm-2 in bamboo stand mixed with broadleaves trees, and 376.22±15.95 kg·hm-2 in bamboo stand mixed with coniferous trees;the annual value of return is 26.70±2.79 kg·hm-2 in pure bamboo forest, 58.47±12.04 kg·hm-2 in bamboo stand mixed with broadleaves trees, and 64.84±3.73 kg·hm-2 in bamboo stand mixed with coniferous trees;The annual annual storage amount is 406.64±40.55 kg·hm-2 in pure bamboo forest, 670.81±60.95 kg·hm-2 in bamboo stand mixed with broadleaves trees, and 357.21±14.85 kg·hm-2 in bamboo stand mixed with coniferous trees. There was greater annual absorption and less annual return amount in bamboo forest.3 The loss nutrients and deterioration of soil was accelerated by the unreasonable management and the operating features of bamboo.(1) The operation character of bamboo leads the productivity to degrade. The operation character was invested in Phyllostachys pubescens forests with different operations and management modes in YongAn County, Fujian Province. The results showed that the biomass was carried off the bamboo forest account for 27.87% of total biomass in model of herb chopping+ special fertilizer+ irrigation forest, account for 24.54% in model of herb chopping+ special fertilizer forest, and 24.51% in model of herb chopping forest. The nutrient(N,P,K,Ca,Mg)amount was carried off the forest is 307.65 kg·hm-2 in model of herb chopping+ special fertilizer+ irrigation forest, 215.49 kg·hm-2 in model of herb chopping+ special fertilizer forest, and 222.90 kg·hm-2 in model of herb chopping forest. A large amount nutrient was carried off the forest by chopping bamboo and shoot digging.(2) Generally, the management model of herb chopping, soil turning, special fertilizer, and irrigation can improve the productivity of bamboo forest in short period. However, the soil was degenerated usually by a single operation if the operation sustained enough a long time.Herb chopping. The comprehensive evaluation scores of chopping herb bamboo forest with different time was 0.6390 in no herb chopping forest , 0.3558 in herb chopping forest less 10 years, and 0.4320 in herb chopping forest more than 30 years. The result showed the soil quality was degenerated by the prolongation time of herb chopping. Many indexes of soil properties was degenerated with the time of prolongation of management, such as, soil bulk density, soil porosity, water holding capacity, soil organic matter, pH, the amount nutrient of maim elements, and enzyme activity.(2) Reclamation measure. The comprehensive evaluation scores of soil were increased with the time prolongation of reclamation measure. The comprehensive evaluation scores was 0.3548 in no soil turning forest , 0.4117 in soil turning in 3 years, and 0.4635 in soil turning forest in 10 years, and 0.5815 in soil turning forest more than 30 years. The results showed that the soil turning improve the soil quality. Soil turning affected the indexes of soil physical properties in different ways. Although the comprehensive evaluation scores was increased with management time prolonged, the sustainable productivity of bamboo forest were damaged because of the decreeing of main nutrients of soil, for example, the organic matters, total nitrogen, hydrolysable nitrogen, total phosphorus, and available phosphorus. Fertilizer application. Usually the fertilizer application implemented adjoins to reclamation measure. Contrary to the reclamation, the comprehensive evaluation scores of soil were decreased with the time prolongation of special fertilization. The comprehensive evaluation scores of soil was 0.5693 in bamboo forest with the management of no special fertilization, 0.4286 in bamboo forest the management of special fertilization for 5 years, and 0.3774 in bamboo forest the management of special fertilization for 10 years. The results showed that soil quality was degenerated acutely by the prolongation time of the management of special fertilization. The indexes of soil physical properties increased with the management time prolonged, such as, soil bulk density, non-capillary pore, buy the indexes of soil chemical properties deteriorated with the management time prolonged, such as, organic matters, total nitrogen, hydrolysable nitrogen, calcium, magnesium.(4) The operation of irritation decreased the comprehensive evaluation scores of soil. The comprehensive evaluation scores of soil was 0.4610 in bamboo forest with the irritation, 0.5123 in bamboo forest with no irrational. Many indexes of soil properties were deteriorated with the management time prolonged, such as, soil bulk density, the soil water capacity, soil water infiltration characteristics, the soil organic matters, total nitrogen, hydrolysable nitrogen, available potassium, available phosphorous, calcium, magnesium, catalase, and phosphatase. The result showed that the management of irritation damaged the sustainable productivity of bamboo forest.4 The management measures of organic matters is key to maintain the productivity of bamboo forest.(1) The reasonable management measures can improve the productivity of bamboo forest.The productivity was improved by implementation of some operators in a short period, such as, herb chopping, soil turning, special fertilization, and irrational, etc. It is very important to practice the measures reasonably. The nutrients of storage amount, annual uptake, and annual storage was promoted by the management of herb chopping, but the nutrients of return amount were reduced. The nutrients were supplemented by fertilizer application, and the utilization coefficient was reduced. However, if the time of fertilization application was enough long, the utilization coefficient would be promoted. The circulation rate of nutrients was promoted with the management time prolonged, and the turnover time was reduced. The operator of irritation improved the return amount of nutrients, reduced the circulation coefficient and the turnover time of nutrients. The utilization coefficient of nutrients and circulation coefficient of nutrients of bamboo stand mixed with broadleaves trees were biggest among different mixed plantations. It was promoting the productivity of bamboo forest and the soil qualities deteriorate slowly to combine, alternation, and interval those operators of management reasonably. It may be an effect method to sustainable productivity of bamboo forest.(2) The structure adjustment is an important tool to maintain the productivity of bamboo forest.The composition of species, age structures, and stand density were important impact factors of bamboo forest productivity. To adjust the structure of bamboo can improve the productivity of bamboo forest. The annual return amount of nutrient of mixed plantation is higher than the pure bamboo forest. The annual return amount of bamboo stand mixed with coniferous trees nutrient of is 3.36 times as large as pure bamboo forest, and the annual return amount of bamboo stand mixed with broadleaves trees nutrient is 2.13 times as large as pure bamboo forest. Generally, the litter of bamboo stand mixed with broadleaves is easier degradation than the litters of pure bamboo forest. The results reflected that management of mixed plantation can increase both the litters amount and degradation of litters. The index of bio-diversity is higher than the pure bamboo forest. The bio-diversity can maintain the ecosystem stability.The age structure of forest is the tree numbers in different ages. The index can reflect the time and rate of regenerations. The productivity of bamboo forest can be maintained by adjusting the age structure of bamboo forest.Reasonable density of bamboo forest is an important factor for sustainable productivity of bamboo forests. To adjust the density of bamboo forest can improve the productivity of bamboo forest in accordance with the purpose of operating, management measures, and site conditions.(3) The return of logging residue plays an important role in the return process of nutrient. It can increase the return amount of nutrients if the branches, leaves, and root of bamboo were placed in the bamboo forest. In the article, the biomass of branches, leaves, and culms stump accounted for 23.87% of total biomass and nutrient contents of them acounted for 32.40% of tatol nutrient contents. A large number of nutrients lost if the branches, leaves, and culms stump were transferred form the bamboo forest.