Studies On Soil Degradation And Soil Productivity Maintenance Measures For Continuous Cropping Poplar Trees

Aiming at continual fast growing and high-yield in short rotation poplar plantation, and maintain or even if enhance the soil fertility, soil degradation problem caused by continuous cropping in poplar nursery and short rotation plantation, and the soil productivity maintenance measures were studied. The study was comprised of three parts: â‘ influence of continuous cropping on growth, biomass distribution and eco-physiology characteristics, â‘¡dynamic changes of soil ecological environment and forest growth of poplar plantation under continuous cropping condition, and â‘¢effect of soil productivity maintenance measures on trees growth and soil physical, soil chemical, soil biological characteristics for continuous cropping poplar plantation. Results show that: 1. As planting generation increased in nursery, tree height, diameter at breast height (DBH), per tree leaf area, biomass, chlorophyll content, and photosynthetic rate were declined in different level, respectively. Growth of cutting stock had a close relation with tree physiological characteristics and soil ecological characteristics that as the planting generation increased, the biomass distribution changed in a pattern of stem biomass ratio descended, ratio of leaf biomass and root biomass increased, and the ratio of total aboveground biomass declined, root biomass and root number dropped, respectively. Soil volume weight was increased, water-holding capacity and capillary porosity, total porosity were descended at the same time as planting generation increased, and the activities of urease, peroxidase, polyphenol oxidase, soil organic nutrient, contents of available N, P, K, the number of three mainly microbes and total microbes quantity showed a same declined trend. Relations between soil physical characteristic, soil enzymes and soil nutrient, the soil enzymes and soil basic fertility, soil enzymes, three soil microbes and total microbes quantity was correlated significantly. 2. As planting generation increased in popular plantation, tree height, DBH, and singletree volume were decreased, obviously. Continuous cropping affected poplar tree growth rhythm that both the successive-years growth and cumulated growth of 3rd generation were higher than 4th generation. Non-capillary porosity was increased, while the maximum water-holding capacity, water-holding capacity of capillary and capillary porosity, total porosity, soil PH value were decreased in continuous cropping plantation, significantly. Soil organic nutrient, available N, P, K and microelements of Cu and Zn, were descended in large scale, while Mn and Fe was increased, and activities of urease, peroxidase and polyphenol oxidase was decreased, as rotation generations increased. Quantity of soil microbes, the number of bacteria, fungi and actinomyces was descended significantly. Correlation analysis showed that soil characters in popular continuous cropping plantation were related significantly. Result showed that as plantation age increased, soil physical characteristic (such as soil volume weight, maximum water holding capacity, water holding capacity of capillary, non-capillary porosity, capillary porosity, total porosity, soil PH value ) became inferior first and got improved later in the 3, 5 and 10 year old plantation, and soil nutrient content, soil enzyme activities, and the number of soil microbes showed the same variety trend in Houshiyang, Zhaoxian Twon. In Niejiahonggou of Qiaoshan Town, as plantation age increased, soil physical characteristic gradually got inferior, soil nutrient content and soil enzyme activity increased, the quantity dynamic of the microbes in 4 year old plantation was higher than the 2 year and 1year old...