杨树人工林连作效应的研究

通过对莒县沭河流域杨树人工林多代连作条件下林地土壤物理结构、养分特征、土壤酶活性、土壤微生物数量以及林分生长状况的系统研究,发现随着杨树连续栽植代数的增加,其林木的树高、胸径、材积呈明显的下降趋势。多重比较结果表明各代之间的树高、胸径、材积差异均达到了极显著的水平。连作后土壤的物理性状的变化不大,随林地代数的增加,土壤容重略有增大,毛管持水量、毛管孔隙度没有一定规律性。土壤pH值随连作代数的增加而减小。土壤养分随栽植代数的增加,总体呈逐代下降趋势。3代、4代林地与2代林地相比,林地表层土壤有机质及各层速效N、速效P、速效K及微量元素Cu,Zn大幅度下降,而Mn和Fe含量有增加的趋势。在0 2 0cm土层范围内,随连作代数增加,林地土壤脲酶、过氧化物酶、多酚氧化酶活性逐渐降低,其变化规律与土壤有机质和速效N ,P ,K含量变化规律相似。过氧化氢酶活性则有随着栽植代数的增加而增加的趋势。连作对杨树人工林土壤微生物数量有显著影响,随着连作代数的增加,土壤细菌、真菌、放线菌的数量大幅度下降

Effect of Continuous Cropping on Poplar Plantation

Soil physical and chemical characteristic, soil nutrient contents, soil enzyme activity, soil microbes distribution and forest growth of tree diameter at breast height (DBH), tree height and single tree volume of continuous cropping poplar plantation, were investigated along Shu river in Ju County in Shandong. Result showed that, with the planting generation increased, tree height, DBH and log volume decreased. By means of multiple comparisons, it was found that the differences among tree height, DBH and log volume of three generations were different, significantly. With the generation increased, soil volume weight increased, while soil pH value decreased, water-holding capacity of capillary and hole degree of capillary have no law. Compaired with the 2nd generation plantation, besides Mn and Fe, all the other mineral elements, such as available N, P, K trace-element Cu and Zn in top soil layer decreased dramatically. Soil urea enzyme, polyphenol oxidase enzyme, peroxide enzyme decreased with the planting generation increased, while the hydrogen enzyme increased. Continuous cropping has a notable effect on the quantity of microbe of poplar population, and with the generation increased, the quantity of the soil bacterium, fungi and actinomyces decreased obviously.